Papers by Kishore Sakharkar
Background: There is a dearth of treatment options for community-acquired and nosocomial
Pseudomo... more Background: There is a dearth of treatment options for community-acquired and nosocomial
Pseudomonas infections due to several rapidly emerging multidrug resistant phenotypes, which
show resistance even to combination therapy. As an alternative, developing selective promiscuous
hybrid compounds for simultaneous modulation of multiple targets is highly appreciated
because it is difficult for the pathogen to develop resistance when an inhibitor has activity
against multiple targets.
Methods: In line with our previous work on phytochemical–antibiotic combination assays and
knowledge-based methods, using a fragment combination approach we here report a novel drug
design strategy of conjugating synergistic phytochemical–antibiotic combinations into a single
hybrid entity for multi-inhibition of P. aeruginosa DNA gyrase subunit B (GyrB)/topoisomerase
IV subunit B (ParE) and dihydrofolate reductase (DHFR) enzymes. The designed conjugates
were evaluated for their multitarget specificity using various computational methods including
docking and dynamic simulations, drug-likeness using molecular properties calculations, and
pharmacophoric features by stereoelectronic property predictions.
Results: Evaluation of the designed hybrid compounds based on their physicochemical properties
has indicated that they are promising drug candidates with drug-like pharmacotherapeutic
profiles. In addition, the stereoelectronic properties such as HOMO (highest occupied molecular
orbital), LUMO (lowest unoccupied molecular orbital), and MEP (molecular electrostatic
potential)
maps calculated by quantum chemical methods gave a good correlation with the
common pharmacophoric features required for multitarget inhibition. Furthermore, docking and
dynamics simulations revealed that the designed compounds have favorable binding affinity and
stability in both the ATP-binding sites of GyrB/ParE and the folate-binding site of DHFR, by
forming strong hydrogen bonds and hydrophobic interactions with key active site residues.
Conclusion: This new design concept of hybrid “phyto-drug” scaffolds, and their simultaneous
perturbation of well-established antibacterial targets from two unrelated pathways, appears to
be very promising and could serve as a prospective lead in multitarget drug discovery.
Keywords: hybrid compounds, multi-target inhibition, drug resistance, dihydrofolate reductase,
DNA gyrase subunit B, topoisomerase IV subunit B, rational drug design
PPARs are ligand activated transcription factors. PPAR𝛾 agonists have been reported as a new and ... more PPARs are ligand activated transcription factors. PPAR𝛾 agonists have been reported as a new and potentially efficacious treatment
of inflammation, diabetes, obesity, cancer, AD, and schizophrenia. Since cancer cells show dysregulation of glycolysis they are
potentially manageable through changes in metabolic environment. Interestingly, several of the genes involved in maintaining the
metabolic environment and the central energy generation pathway are regulated or predicted to be regulated by PPAR𝛾.The use of
synthetic PPAR𝛾 ligands as drugs and their recent withdrawal/restricted usage highlight the lack of understanding of the molecular
basis of these drugs, their off-target effects, and their network.These data further underscores the complexity of nuclear receptor
signalling mechanisms.This paper will discuss the function and role of PPAR𝛾 in energy metabolism and cancer biology in general
and its emergence as a promising therapeutic target in breast cancer.
Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor and plays important ro... more Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor and plays important roles in breast cancer
cell proliferation. The complexity of the underlying biochemical and molecular mechanisms of breast cancer and the
involvement of PPARγ in breast cancer pathophysiology are unclear. In this study, we carried out prediction of the
peroxisome proliferator response element (PPRE) motifs in 2332 genes reported to be involved in breast cancer in
literature. A total of 178 genes were found to have PPRE (DR1/DR2) and / or PPAR-associated conserved motif (PACM)
motifs. We further constructed protein-protein interaction network, disease gene network and gene ontology (GO)
analyses to identify novel key genes for experimental validation. We identified two genes in the glycolytic pathway
(phosphoglycerate kinase 1 (PGK1) and pyruvate kinase M2 (PKM2)) at the ATP production steps and experimentally
validated their repression by PPARγ in two breast cancer cell lines MDA-MB-231 and MCF-7. Further analysis suggested
that this repression leads to decrease in ATP levels and apoptosis. These investigations will help us in understanding
the molecular mechanisms by which PPARγ regulates the cellular energy pathway and the use of its ligands in human
breast cancer therapeutics.
In this study, we successfully present the dualtarget
design hypothesis to inhibit both dihydropt... more In this study, we successfully present the dualtarget
design hypothesis to inhibit both dihydropteroate
synthase (DHPS) and dihydrofolate reductase (DHFR)
enzymes using a novel scheme that integrates our previous
antibiotic-phytochemical interaction data, fragment
combination and knowledge-based methods. Both the
enzymes are well established antibacterial targets from
folate biosynthesis pathway and their synergistic
modulation by a single hybrid entity may have profound
therapeutic benefits. Evaluation of the designed hybrid
compounds based on their physico-chemical properties has
indicated them as promising drug candidates with drug-like
pharmacotherapeutic profiles. In addition, the stereoelectronic
properties such as HOMO, LUMO and MEP
maps calculated by quantum chemical methods gave a good
correlation with the common pharmacophoric features
required for dual-site interactions. Furthermore, docking
and dynamics simulation studies reveal that the designed
hybrid compounds have favorable binding affinity and
stability in both pterin-binding site of DHPS and folatebinding
site of DHFR by forming strong hydrogen bonds
and hydrophobic interactions with key active-site residues.
Looking forward this study could serve as a prospective
lead in the process of new natural-product based hybriddrugs
development.
Low density polythene (LDPE) is the most
widely used packaging material primarily because of its
... more Low density polythene (LDPE) is the most
widely used packaging material primarily because of its
excellent mechanical properties, barrier properties against
water, light weight, low cost and high energy effectiveness.
However, due to its ubiquitous nature, and resistance to
biodegradability, the disposal strategies are crucial and
need attention. Recently, microorganisms have become the
focus of interest for environmental friendly disposal of
plastic and polymer-based waste. This manuscript aims to
investigate the extent of biodegradability of LDPE by four
different strains of Pseudomonas bacteria—Pseudomonas
aeruginosa PAO1 (ATCC 15729), Pseudomonas aeruginosa
(ATCC 15692), Pseudomonas putida (KT2440 ATCC
47054) and Pseudomonas syringae (DC3000 ATCC
10862). Degradation of LDPE was determined by weight
loss of the sample, morphological changes, mechanical and
spectroscopic variations. The eluted compounds after
degradation were analysed by gas chromatography coupled
with mass spectroscopy. Our results show that Pseudomonas
spp. can degrade LDPE films.
Constraint-based flux balance analysis (FBA) is a powerful tool for predicting target genes that ... more Constraint-based flux balance analysis (FBA) is a powerful tool for predicting target genes that can be
engineered by analyzing the redistribution of metabolic fluxes on specific gene modifications. Specifically,
the effects of metabolic gene deletions on flux distribution can be examined by forcing the fluxes of different
reactions catalyzed by the corresponding gene product to zero. However, the target enzyme needs to
be essential for survival of the organism to ensure that efficient chemical inhibition results in cell stasis or
death. Here, we investigate the essentiality of enzymes in iMO1056 metabolic model of nosocomial pathogen
Pseudomonas aeruginosa by performing in silico enzyme deletions using FBA. We identified 116/113
essential enzymes in rich medium in P. aeruginosa. These were then compared with human metabolic model
to identify nonhomologous enzymes that could be possible drug targets. Here, we present a refined list of 41
novel potential targets for P. aeruginosa. These targets were then matched with the enzymes belonging to 97
correlated clusters through which we propose the concept of “one target per cluster.” Our approach relates
to the “single drug multiple target (SDMT)” concept and has potential in efficient drug target discovery
Mutant selection window (MSW) is the antimicrobial concentration ranging from the minimum inhibit... more Mutant selection window (MSW) is the antimicrobial concentration ranging from the minimum inhibitory concentration
(MIC) to the mutant prevention concentration (MPC). Placing antibiotic concentration in the MSW is expected
to selectively enrich mutant subpopulations while placing the concentration above the window is expected to restrict the
selective enrichment of resistant bacteria. Even though there is a rise of multidrug resistant bacteria, there are not many
new antibiotics introduced to market in the recent years. Therefore, there is a need to utilize existing knowledge on antibiotics
to prevent the development of multidrug resistance and if possible reposition the antibiotics. The increase in knowledge
on MSW and microbial evolution of resistance can be of potential use in novel dosing regimens and antimicrobial
combinations. In this study, we investigated the effect of the addition of ethyl gallate (EG) on the MSW and MPC of
MRSA ATCC strain 43300, before and after it has been induced to develop resistance to tetracycline and fusidic acid. It is
observed that tetracycline has narrower MSW than fusidic acid. This suggests that fusidic acid provides less genetic stability
than tetracycline and hence it is easy for mutants to develop. We also report that addition of ethyl gallate at
1024μg/ml closes the mutant selection window (i.e. MIC = MPC) of both tetracycline and fusidic acid, thus helping overcome
the effect of resistance developed over time. Hence, we propose that combination of ethyl gallate with antibiotics
has potential clinical implications and needs further exploration
The 2009 swine-origin H1N1 influenza A virus (S-OIV) pandemic has afflicted many populations worl... more The 2009 swine-origin H1N1 influenza A virus (S-OIV) pandemic has afflicted many populations worldwide to varying degrees of severity. The apparent susceptibility of different populations to S-OIV was addressed by predicting the consensus T-cell epitopes of hemagglutinin, neuraminidase, matrix 1 and 2 proteins of four selected influenza H1N1 strains (A/California/4/09, A/Brisbane/59/07, A/Puerto Rico/8/34, A/Brevig Mission/1/18), and comparing their binding to MHC class I molecules in the predominant HLA haplotypes in the Singapore, Mexican, and US populace (HLA-A*0201, HLA-A*1101, and HLA-A*2402). Tracking the changes in these strains offered insights into H1N1 virus evolution over 9 decades. The occurrence of T-cell epitopes predicted to be conserved among 1918, 1934 and 2009 strains of H1N1 may explain why the elderly are not amongst the most affected in this recent pandemic. The extent of cross-reactivity between the T-cell responses to the seasonal vaccine with those against the current circulating strain may also be inferred from the number and quality of the epitopes predicted to be conserved between the vaccine strain and S-OIV. The relatively lower number of common T-cell epitopes predicted for HLA-A*0201 suggests that T-cells of individuals with this haplotype are relatively less likely to recognize the novel S-OIV strain. These findings may account for the differences in epidemiology of S-OIV infection in different countries, where the attack, hospitalization and fatality rates vary. Such data also have potential applications in identifying cross-reactive Tcell epitopes to design future vaccines against a broader range of influenza strains.
In this study the in vitro activities of seven antibiotics (ciprofloxacin, ceftazidime, tetracycl... more In this study the in vitro activities of seven antibiotics (ciprofloxacin, ceftazidime, tetracycline,
trimethoprim, sulfamethoxazole, polymyxin B and piperacillin) and six phytochemicals
(protocatechuic acid, gallic acid, ellagic acid, rutin, berberine and myricetin) against five P.
aeruginosa isolates, alone and in combination are evaluated. All the phytochemicals under
investigation demonstrate potential inhibitory activity against P. aeruginosa. The combinations
of sulfamethoxazole plus protocatechuic acid, sulfamethoxazole plus ellagic acid, sulfamethoxazole
plus gallic acid and tetracycline plus gallic acid show synergistic mode of interaction.
However, the combinations of sulfamethoxazole plus myricetin shows synergism for three
strains (PA01, DB5218 and DR3062). The synergistic combinations are further evaluated for
their bactericidal activity against P. aeruginosa ATCC strain using time-kill method.
Sub-inhibitory dose responses of antibiotics and phytochemicals individually and in combination
are presented along with their interaction network to suggest on the mechanism of action
and potential targets for the phytochemicals under investigation. The identified synergistic
combinations can be of potent therapeutic value against P. aeruginosa infections. These
findings have potential implications in delaying the development of resistance as the antibacterial
effect is achieved with lower concentrations of both drugs (antibiotics and phytochemicals).
Background: In June 2009, we conducted a prospective study in Singapore on 51 individuals to dete... more Background: In June 2009, we conducted a prospective study in Singapore on 51 individuals to determine
their serologic responses before and following receipt of the 2009 Southern Hemisphere seasonal
influenza vaccine.
Materials and methods: Paired serum samples were obtained before and 3–4 weeks after vaccination. Virus
microneutralization assays were performed to quantify antibodies against A/Brisbane/59/2007 vaccine,
pandemic H1N12009
and A/Puerto Rico/08/34 H1N1 strains.
Results: Postvaccination,
43%, 12% and 24% of subjects displayed a 4fold
or greater rise in neutralizing
antibody titers against the three strains, respectively. There was a positive correlation among individuals
whoshowed increased titers to both pandemic H1N12009
and A/Puerto Rico/08/34 (p < 0.001). However,
this correlation was not observed for A/Brisbane/59/2007 with either strain. The relative conservation
and accessibility of predicted Bcell
epitopes may explain the limited crossreactivity
of the antibodies
directed against common H1N1 epitopes.
Conclusions: These results suggest that seasonal influenza vaccination confers a certain degree of crossprotection
to other H1N1 strains. The correlation in crossreactive
antibody titers to A/Puerto Rico/08/34
and pandemic H1N12009
implies that previous exposure to pre1957
H1N1 strains may confer some
protection against the 2009 pandemic strain
The emergence of antibiotic resistance in bacterial pathogens
poses a great challenge to public h... more The emergence of antibiotic resistance in bacterial pathogens
poses a great challenge to public health and emphasizes
the need for new antimicrobial targets. The recent development
of microbial genomics and the availability of genome
sequences allows for the identification of essential
genes which could be novel and potential targets for antibacterial
drugs. However, these predicted targets need experimental
validation to confirm essentiality. Here, we report
on experimental validation of a two potential targets in the
lipopolysaccharide (LPS) biosynthesis pathway of the pathogen
Pseudomonas aeruginosa PAO1 using insertion duplication.
Two genes, kdsA and waaG , from LPS encoding proteins
2-dehydro-3-deoxyphosphooctonate aldolase and UDPglucose
(heptosyl) LPS -1,3-glucosyltransferase were selected as putative target candidates for the gene disruption experiments
using plasmid insertion mutagenesis to determine
essentiality. The introduction of a selectable ampicillin
and kanamycin resistance marker into the chromosome resulted
in lack of recovery of antibiotic-resistant co lonies suggesting
the essentiality of these genes for the survival of
P. aeruginosa . Several molecular analyses were carried out in
order to confirm the essentiality of these genes. We propose
that the above two validated drug targets are essential and
can be screened for functional inhibitors for the discovery of
novel therapeutic compounds against antibiotic-resistant
opportunistic pathogen P. aeruginosa
Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureu... more Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus
(MSSA) are highly resistant to some antibiotics and it is difficult to treat infections caused by Staphylococcus aureus.
This study evaluates the amount of Biofilm formation in four strains of MRSA and two strains of MSSA in presence of
three antibiotics (mupirocin, tetracycline, and fusidic acid), two phytochemicals (epicatechin gallate and ethyl gallate) as
single agents and in combination. Biofilm formation was quantified using spectrophotometry and visualized by Scanning
Electron Microscope. Our results show that the combination of tetracycline with ethyl gallate, and tetracycline with epicatechin
gallate were most effective in inhibiting the biofilm formation. It is interesting to observe that biofilm formation
is inhibited significantly at synergistic concentration of combinations of antibiotics and phytochemicals. These results can
be of potential therapeutic value towards development of new drugs for the prevention and treatment of infections caused
by drug- resistant biofilm forming bacteria
This investigation reports on the drug interactions between chitosans and antibiotics in Staphylo... more This investigation reports on the drug interactions between chitosans and antibiotics in Staphylococcus aureus. The combination
study shows that chitosan oligosaccharides have synergistic effect in combination with tetracycline, ceftriazone and sulfamethoxazole.
Also, high molecular weight chitosan was found to be effective against Staphylococcus aureus in combination with Sulfamethoxazole.
These results indicate the potential efficacy of chitosans in combinations with antibiotics for enhancing total biological activity
The antimicrobial activities of tetracycline,
mupirocin, and fusidic acid are tested in combinati... more The antimicrobial activities of tetracycline,
mupirocin, and fusidic acid are tested in combination with
Epicatechin Gallate (ECG), and Ethyl Gallate (EG) using 2
Methicillin resistant (MRSA) and 2 Methicillin sensitive
(MSSA) strains of Staphylococcus aureus. Sub-inhibitory
concentration of EG at 256mg l-1 is found to be synergistic
when used in combination with tetracycline, mupirocin,
and fusidic acid; and a sub-inhibitory concentration of ECG
at 32 mg l-1 is found to be synergistic with tetracycline in
all the four Staphylococcus aureus strains tested. The
synergistic combinations reduce the MICs of all the above
three antibiotics by 4 fold. Combining ECG at 32mg l-1
with mupirocin, reduces the MIC of mupirocin by four fold
in MSSA C1 strain. 74% of the combinations show
consistent results in both time-kill assay and checkerboard
method. The identified combinations may lead towards
novel therapeutic interventions for treating MRSA
infections
Background and purpose: Antibiotic combinations are used to enhance antibacterial efficacy and to... more Background and purpose: Antibiotic combinations are used to enhance antibacterial efficacy and to prevent
the development of resistance. In this study, the in vitro activities of antibiotic and phytochemical combinations
against Pseudomonas aeruginosa were tested by the fractional inhibitory concentration method, derived from
the minimal inhibitory concentrations (MICs) of the agents in combination.
Methods: The antimicrobial activity of phytochemicals, alone and in combination with antibiotics, was evaluated
using the checkerboard assay and time-kill curve methods.
Results: There was synergism between gentamicin and caffeic acid, and sulfadiazine and the 3 phytochemicals
under investigation (protocatechuic acid, quercetin, caffeic acid). The MIC of sulfadiazine was 256 μg/mL, and
of gentamicin was 2 μg/mL. When gentamicin was combined with one-quarter the MIC of caffeic acid, the MIC
of gentamicin was reduced 4-fold. When sulfadiazine was tested with one-quarter the MIC of protocatechuic
acid, quercetin, and caffeic acid, the MIC was reduced 4-fold in combination with each of the drugs.
Conclusions: These results indicate the potential efficacy of phytochemicals in combination with antibiotics for
enhancing total biological activity
Chitosan and its derivative water soluble Chitosan oligosaccharide are used in a variety of
appli... more Chitosan and its derivative water soluble Chitosan oligosaccharide are used in a variety of
applications in pharmaceutical preparations. In this study, 2 wild (ATCC 15729 and PAO1)
and 2 mutant strains (PT121 and PT149) of P. aeruginosa are investigated for drug-drug interactions
in vitro. 10 antimicrobial agents (antibiotics) are combined with different degree of
deacetylated Chitosans and Chitosan oligosaccharide. All the chitosans show synergistic activity
with sulfamethoxazole, a sulfonamide antimicrobial agent. It is interesting to observe
that the MIC value for the MexEF-OprN overexpressing mutant strain of P. aeruginosa is 5
fold higher than the other strains under investigation suggesting a possible role of this efflux
pump in Sulfamethoxazole efflux. The findings suggest on the use of chitosans as enhancing
agent in combination with antibiotics in pharmaceutical preparations.
The genome profile of exon-intron distributions is presented for six eukaryotic genomes (H. sapie... more The genome profile of exon-intron distributions is presented for six eukaryotic genomes (H. sapiens, P. troglodytes, M. musculus, D. rerio, C. elegans, D. melanogaster) to deduce similarities and differences among their genome design and architecture. Interestingly, in all the six genomes, the total length in exons, introns and intergenic DNA on each chromosome is significantly correlated to the chromosome size. Another correlation is found between the total intron length and total exon length for each genome. The results presented provide a framework for understanding the nature and patterns of exon-intron length distributions, the constraints on them and their role in genome design and evolution and provide an insight into the evolution of intron-exon structures of eukaryotic genes.
The diversity of hosts, pathogens and host–pathogen relationships reflects the influence of selec... more The diversity of hosts, pathogens and host–pathogen relationships reflects the influence of selective pressures
that fuel diversity through ongoing interactions with other rapidly evolving molecules in the environment. This
paper discusses specific examples illustrating the phenomenon of diversity of hosts and pathogens, with special
reference to human papillomaviruses and H5N1 influenza viruses. We also review the influence of diverse host–
pathogen interactions that determine the pathophysiology of infections, and their responses to drugs or vaccines
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Papers by Kishore Sakharkar
Pseudomonas infections due to several rapidly emerging multidrug resistant phenotypes, which
show resistance even to combination therapy. As an alternative, developing selective promiscuous
hybrid compounds for simultaneous modulation of multiple targets is highly appreciated
because it is difficult for the pathogen to develop resistance when an inhibitor has activity
against multiple targets.
Methods: In line with our previous work on phytochemical–antibiotic combination assays and
knowledge-based methods, using a fragment combination approach we here report a novel drug
design strategy of conjugating synergistic phytochemical–antibiotic combinations into a single
hybrid entity for multi-inhibition of P. aeruginosa DNA gyrase subunit B (GyrB)/topoisomerase
IV subunit B (ParE) and dihydrofolate reductase (DHFR) enzymes. The designed conjugates
were evaluated for their multitarget specificity using various computational methods including
docking and dynamic simulations, drug-likeness using molecular properties calculations, and
pharmacophoric features by stereoelectronic property predictions.
Results: Evaluation of the designed hybrid compounds based on their physicochemical properties
has indicated that they are promising drug candidates with drug-like pharmacotherapeutic
profiles. In addition, the stereoelectronic properties such as HOMO (highest occupied molecular
orbital), LUMO (lowest unoccupied molecular orbital), and MEP (molecular electrostatic
potential)
maps calculated by quantum chemical methods gave a good correlation with the
common pharmacophoric features required for multitarget inhibition. Furthermore, docking and
dynamics simulations revealed that the designed compounds have favorable binding affinity and
stability in both the ATP-binding sites of GyrB/ParE and the folate-binding site of DHFR, by
forming strong hydrogen bonds and hydrophobic interactions with key active site residues.
Conclusion: This new design concept of hybrid “phyto-drug” scaffolds, and their simultaneous
perturbation of well-established antibacterial targets from two unrelated pathways, appears to
be very promising and could serve as a prospective lead in multitarget drug discovery.
Keywords: hybrid compounds, multi-target inhibition, drug resistance, dihydrofolate reductase,
DNA gyrase subunit B, topoisomerase IV subunit B, rational drug design
of inflammation, diabetes, obesity, cancer, AD, and schizophrenia. Since cancer cells show dysregulation of glycolysis they are
potentially manageable through changes in metabolic environment. Interestingly, several of the genes involved in maintaining the
metabolic environment and the central energy generation pathway are regulated or predicted to be regulated by PPAR𝛾.The use of
synthetic PPAR𝛾 ligands as drugs and their recent withdrawal/restricted usage highlight the lack of understanding of the molecular
basis of these drugs, their off-target effects, and their network.These data further underscores the complexity of nuclear receptor
signalling mechanisms.This paper will discuss the function and role of PPAR𝛾 in energy metabolism and cancer biology in general
and its emergence as a promising therapeutic target in breast cancer.
cell proliferation. The complexity of the underlying biochemical and molecular mechanisms of breast cancer and the
involvement of PPARγ in breast cancer pathophysiology are unclear. In this study, we carried out prediction of the
peroxisome proliferator response element (PPRE) motifs in 2332 genes reported to be involved in breast cancer in
literature. A total of 178 genes were found to have PPRE (DR1/DR2) and / or PPAR-associated conserved motif (PACM)
motifs. We further constructed protein-protein interaction network, disease gene network and gene ontology (GO)
analyses to identify novel key genes for experimental validation. We identified two genes in the glycolytic pathway
(phosphoglycerate kinase 1 (PGK1) and pyruvate kinase M2 (PKM2)) at the ATP production steps and experimentally
validated their repression by PPARγ in two breast cancer cell lines MDA-MB-231 and MCF-7. Further analysis suggested
that this repression leads to decrease in ATP levels and apoptosis. These investigations will help us in understanding
the molecular mechanisms by which PPARγ regulates the cellular energy pathway and the use of its ligands in human
breast cancer therapeutics.
design hypothesis to inhibit both dihydropteroate
synthase (DHPS) and dihydrofolate reductase (DHFR)
enzymes using a novel scheme that integrates our previous
antibiotic-phytochemical interaction data, fragment
combination and knowledge-based methods. Both the
enzymes are well established antibacterial targets from
folate biosynthesis pathway and their synergistic
modulation by a single hybrid entity may have profound
therapeutic benefits. Evaluation of the designed hybrid
compounds based on their physico-chemical properties has
indicated them as promising drug candidates with drug-like
pharmacotherapeutic profiles. In addition, the stereoelectronic
properties such as HOMO, LUMO and MEP
maps calculated by quantum chemical methods gave a good
correlation with the common pharmacophoric features
required for dual-site interactions. Furthermore, docking
and dynamics simulation studies reveal that the designed
hybrid compounds have favorable binding affinity and
stability in both pterin-binding site of DHPS and folatebinding
site of DHFR by forming strong hydrogen bonds
and hydrophobic interactions with key active-site residues.
Looking forward this study could serve as a prospective
lead in the process of new natural-product based hybriddrugs
development.
widely used packaging material primarily because of its
excellent mechanical properties, barrier properties against
water, light weight, low cost and high energy effectiveness.
However, due to its ubiquitous nature, and resistance to
biodegradability, the disposal strategies are crucial and
need attention. Recently, microorganisms have become the
focus of interest for environmental friendly disposal of
plastic and polymer-based waste. This manuscript aims to
investigate the extent of biodegradability of LDPE by four
different strains of Pseudomonas bacteria—Pseudomonas
aeruginosa PAO1 (ATCC 15729), Pseudomonas aeruginosa
(ATCC 15692), Pseudomonas putida (KT2440 ATCC
47054) and Pseudomonas syringae (DC3000 ATCC
10862). Degradation of LDPE was determined by weight
loss of the sample, morphological changes, mechanical and
spectroscopic variations. The eluted compounds after
degradation were analysed by gas chromatography coupled
with mass spectroscopy. Our results show that Pseudomonas
spp. can degrade LDPE films.
engineered by analyzing the redistribution of metabolic fluxes on specific gene modifications. Specifically,
the effects of metabolic gene deletions on flux distribution can be examined by forcing the fluxes of different
reactions catalyzed by the corresponding gene product to zero. However, the target enzyme needs to
be essential for survival of the organism to ensure that efficient chemical inhibition results in cell stasis or
death. Here, we investigate the essentiality of enzymes in iMO1056 metabolic model of nosocomial pathogen
Pseudomonas aeruginosa by performing in silico enzyme deletions using FBA. We identified 116/113
essential enzymes in rich medium in P. aeruginosa. These were then compared with human metabolic model
to identify nonhomologous enzymes that could be possible drug targets. Here, we present a refined list of 41
novel potential targets for P. aeruginosa. These targets were then matched with the enzymes belonging to 97
correlated clusters through which we propose the concept of “one target per cluster.” Our approach relates
to the “single drug multiple target (SDMT)” concept and has potential in efficient drug target discovery
(MIC) to the mutant prevention concentration (MPC). Placing antibiotic concentration in the MSW is expected
to selectively enrich mutant subpopulations while placing the concentration above the window is expected to restrict the
selective enrichment of resistant bacteria. Even though there is a rise of multidrug resistant bacteria, there are not many
new antibiotics introduced to market in the recent years. Therefore, there is a need to utilize existing knowledge on antibiotics
to prevent the development of multidrug resistance and if possible reposition the antibiotics. The increase in knowledge
on MSW and microbial evolution of resistance can be of potential use in novel dosing regimens and antimicrobial
combinations. In this study, we investigated the effect of the addition of ethyl gallate (EG) on the MSW and MPC of
MRSA ATCC strain 43300, before and after it has been induced to develop resistance to tetracycline and fusidic acid. It is
observed that tetracycline has narrower MSW than fusidic acid. This suggests that fusidic acid provides less genetic stability
than tetracycline and hence it is easy for mutants to develop. We also report that addition of ethyl gallate at
1024μg/ml closes the mutant selection window (i.e. MIC = MPC) of both tetracycline and fusidic acid, thus helping overcome
the effect of resistance developed over time. Hence, we propose that combination of ethyl gallate with antibiotics
has potential clinical implications and needs further exploration
trimethoprim, sulfamethoxazole, polymyxin B and piperacillin) and six phytochemicals
(protocatechuic acid, gallic acid, ellagic acid, rutin, berberine and myricetin) against five P.
aeruginosa isolates, alone and in combination are evaluated. All the phytochemicals under
investigation demonstrate potential inhibitory activity against P. aeruginosa. The combinations
of sulfamethoxazole plus protocatechuic acid, sulfamethoxazole plus ellagic acid, sulfamethoxazole
plus gallic acid and tetracycline plus gallic acid show synergistic mode of interaction.
However, the combinations of sulfamethoxazole plus myricetin shows synergism for three
strains (PA01, DB5218 and DR3062). The synergistic combinations are further evaluated for
their bactericidal activity against P. aeruginosa ATCC strain using time-kill method.
Sub-inhibitory dose responses of antibiotics and phytochemicals individually and in combination
are presented along with their interaction network to suggest on the mechanism of action
and potential targets for the phytochemicals under investigation. The identified synergistic
combinations can be of potent therapeutic value against P. aeruginosa infections. These
findings have potential implications in delaying the development of resistance as the antibacterial
effect is achieved with lower concentrations of both drugs (antibiotics and phytochemicals).
their serologic responses before and following receipt of the 2009 Southern Hemisphere seasonal
influenza vaccine.
Materials and methods: Paired serum samples were obtained before and 3–4 weeks after vaccination. Virus
microneutralization assays were performed to quantify antibodies against A/Brisbane/59/2007 vaccine,
pandemic H1N12009
and A/Puerto Rico/08/34 H1N1 strains.
Results: Postvaccination,
43%, 12% and 24% of subjects displayed a 4fold
or greater rise in neutralizing
antibody titers against the three strains, respectively. There was a positive correlation among individuals
whoshowed increased titers to both pandemic H1N12009
and A/Puerto Rico/08/34 (p < 0.001). However,
this correlation was not observed for A/Brisbane/59/2007 with either strain. The relative conservation
and accessibility of predicted Bcell
epitopes may explain the limited crossreactivity
of the antibodies
directed against common H1N1 epitopes.
Conclusions: These results suggest that seasonal influenza vaccination confers a certain degree of crossprotection
to other H1N1 strains. The correlation in crossreactive
antibody titers to A/Puerto Rico/08/34
and pandemic H1N12009
implies that previous exposure to pre1957
H1N1 strains may confer some
protection against the 2009 pandemic strain
poses a great challenge to public health and emphasizes
the need for new antimicrobial targets. The recent development
of microbial genomics and the availability of genome
sequences allows for the identification of essential
genes which could be novel and potential targets for antibacterial
drugs. However, these predicted targets need experimental
validation to confirm essentiality. Here, we report
on experimental validation of a two potential targets in the
lipopolysaccharide (LPS) biosynthesis pathway of the pathogen
Pseudomonas aeruginosa PAO1 using insertion duplication.
Two genes, kdsA and waaG , from LPS encoding proteins
2-dehydro-3-deoxyphosphooctonate aldolase and UDPglucose
(heptosyl) LPS -1,3-glucosyltransferase were selected as putative target candidates for the gene disruption experiments
using plasmid insertion mutagenesis to determine
essentiality. The introduction of a selectable ampicillin
and kanamycin resistance marker into the chromosome resulted
in lack of recovery of antibiotic-resistant co lonies suggesting
the essentiality of these genes for the survival of
P. aeruginosa . Several molecular analyses were carried out in
order to confirm the essentiality of these genes. We propose
that the above two validated drug targets are essential and
can be screened for functional inhibitors for the discovery of
novel therapeutic compounds against antibiotic-resistant
opportunistic pathogen P. aeruginosa
(MSSA) are highly resistant to some antibiotics and it is difficult to treat infections caused by Staphylococcus aureus.
This study evaluates the amount of Biofilm formation in four strains of MRSA and two strains of MSSA in presence of
three antibiotics (mupirocin, tetracycline, and fusidic acid), two phytochemicals (epicatechin gallate and ethyl gallate) as
single agents and in combination. Biofilm formation was quantified using spectrophotometry and visualized by Scanning
Electron Microscope. Our results show that the combination of tetracycline with ethyl gallate, and tetracycline with epicatechin
gallate were most effective in inhibiting the biofilm formation. It is interesting to observe that biofilm formation
is inhibited significantly at synergistic concentration of combinations of antibiotics and phytochemicals. These results can
be of potential therapeutic value towards development of new drugs for the prevention and treatment of infections caused
by drug- resistant biofilm forming bacteria
study shows that chitosan oligosaccharides have synergistic effect in combination with tetracycline, ceftriazone and sulfamethoxazole.
Also, high molecular weight chitosan was found to be effective against Staphylococcus aureus in combination with Sulfamethoxazole.
These results indicate the potential efficacy of chitosans in combinations with antibiotics for enhancing total biological activity
mupirocin, and fusidic acid are tested in combination with
Epicatechin Gallate (ECG), and Ethyl Gallate (EG) using 2
Methicillin resistant (MRSA) and 2 Methicillin sensitive
(MSSA) strains of Staphylococcus aureus. Sub-inhibitory
concentration of EG at 256mg l-1 is found to be synergistic
when used in combination with tetracycline, mupirocin,
and fusidic acid; and a sub-inhibitory concentration of ECG
at 32 mg l-1 is found to be synergistic with tetracycline in
all the four Staphylococcus aureus strains tested. The
synergistic combinations reduce the MICs of all the above
three antibiotics by 4 fold. Combining ECG at 32mg l-1
with mupirocin, reduces the MIC of mupirocin by four fold
in MSSA C1 strain. 74% of the combinations show
consistent results in both time-kill assay and checkerboard
method. The identified combinations may lead towards
novel therapeutic interventions for treating MRSA
infections
the development of resistance. In this study, the in vitro activities of antibiotic and phytochemical combinations
against Pseudomonas aeruginosa were tested by the fractional inhibitory concentration method, derived from
the minimal inhibitory concentrations (MICs) of the agents in combination.
Methods: The antimicrobial activity of phytochemicals, alone and in combination with antibiotics, was evaluated
using the checkerboard assay and time-kill curve methods.
Results: There was synergism between gentamicin and caffeic acid, and sulfadiazine and the 3 phytochemicals
under investigation (protocatechuic acid, quercetin, caffeic acid). The MIC of sulfadiazine was 256 μg/mL, and
of gentamicin was 2 μg/mL. When gentamicin was combined with one-quarter the MIC of caffeic acid, the MIC
of gentamicin was reduced 4-fold. When sulfadiazine was tested with one-quarter the MIC of protocatechuic
acid, quercetin, and caffeic acid, the MIC was reduced 4-fold in combination with each of the drugs.
Conclusions: These results indicate the potential efficacy of phytochemicals in combination with antibiotics for
enhancing total biological activity
applications in pharmaceutical preparations. In this study, 2 wild (ATCC 15729 and PAO1)
and 2 mutant strains (PT121 and PT149) of P. aeruginosa are investigated for drug-drug interactions
in vitro. 10 antimicrobial agents (antibiotics) are combined with different degree of
deacetylated Chitosans and Chitosan oligosaccharide. All the chitosans show synergistic activity
with sulfamethoxazole, a sulfonamide antimicrobial agent. It is interesting to observe
that the MIC value for the MexEF-OprN overexpressing mutant strain of P. aeruginosa is 5
fold higher than the other strains under investigation suggesting a possible role of this efflux
pump in Sulfamethoxazole efflux. The findings suggest on the use of chitosans as enhancing
agent in combination with antibiotics in pharmaceutical preparations.
that fuel diversity through ongoing interactions with other rapidly evolving molecules in the environment. This
paper discusses specific examples illustrating the phenomenon of diversity of hosts and pathogens, with special
reference to human papillomaviruses and H5N1 influenza viruses. We also review the influence of diverse host–
pathogen interactions that determine the pathophysiology of infections, and their responses to drugs or vaccines
Pseudomonas infections due to several rapidly emerging multidrug resistant phenotypes, which
show resistance even to combination therapy. As an alternative, developing selective promiscuous
hybrid compounds for simultaneous modulation of multiple targets is highly appreciated
because it is difficult for the pathogen to develop resistance when an inhibitor has activity
against multiple targets.
Methods: In line with our previous work on phytochemical–antibiotic combination assays and
knowledge-based methods, using a fragment combination approach we here report a novel drug
design strategy of conjugating synergistic phytochemical–antibiotic combinations into a single
hybrid entity for multi-inhibition of P. aeruginosa DNA gyrase subunit B (GyrB)/topoisomerase
IV subunit B (ParE) and dihydrofolate reductase (DHFR) enzymes. The designed conjugates
were evaluated for their multitarget specificity using various computational methods including
docking and dynamic simulations, drug-likeness using molecular properties calculations, and
pharmacophoric features by stereoelectronic property predictions.
Results: Evaluation of the designed hybrid compounds based on their physicochemical properties
has indicated that they are promising drug candidates with drug-like pharmacotherapeutic
profiles. In addition, the stereoelectronic properties such as HOMO (highest occupied molecular
orbital), LUMO (lowest unoccupied molecular orbital), and MEP (molecular electrostatic
potential)
maps calculated by quantum chemical methods gave a good correlation with the
common pharmacophoric features required for multitarget inhibition. Furthermore, docking and
dynamics simulations revealed that the designed compounds have favorable binding affinity and
stability in both the ATP-binding sites of GyrB/ParE and the folate-binding site of DHFR, by
forming strong hydrogen bonds and hydrophobic interactions with key active site residues.
Conclusion: This new design concept of hybrid “phyto-drug” scaffolds, and their simultaneous
perturbation of well-established antibacterial targets from two unrelated pathways, appears to
be very promising and could serve as a prospective lead in multitarget drug discovery.
Keywords: hybrid compounds, multi-target inhibition, drug resistance, dihydrofolate reductase,
DNA gyrase subunit B, topoisomerase IV subunit B, rational drug design
of inflammation, diabetes, obesity, cancer, AD, and schizophrenia. Since cancer cells show dysregulation of glycolysis they are
potentially manageable through changes in metabolic environment. Interestingly, several of the genes involved in maintaining the
metabolic environment and the central energy generation pathway are regulated or predicted to be regulated by PPAR𝛾.The use of
synthetic PPAR𝛾 ligands as drugs and their recent withdrawal/restricted usage highlight the lack of understanding of the molecular
basis of these drugs, their off-target effects, and their network.These data further underscores the complexity of nuclear receptor
signalling mechanisms.This paper will discuss the function and role of PPAR𝛾 in energy metabolism and cancer biology in general
and its emergence as a promising therapeutic target in breast cancer.
cell proliferation. The complexity of the underlying biochemical and molecular mechanisms of breast cancer and the
involvement of PPARγ in breast cancer pathophysiology are unclear. In this study, we carried out prediction of the
peroxisome proliferator response element (PPRE) motifs in 2332 genes reported to be involved in breast cancer in
literature. A total of 178 genes were found to have PPRE (DR1/DR2) and / or PPAR-associated conserved motif (PACM)
motifs. We further constructed protein-protein interaction network, disease gene network and gene ontology (GO)
analyses to identify novel key genes for experimental validation. We identified two genes in the glycolytic pathway
(phosphoglycerate kinase 1 (PGK1) and pyruvate kinase M2 (PKM2)) at the ATP production steps and experimentally
validated their repression by PPARγ in two breast cancer cell lines MDA-MB-231 and MCF-7. Further analysis suggested
that this repression leads to decrease in ATP levels and apoptosis. These investigations will help us in understanding
the molecular mechanisms by which PPARγ regulates the cellular energy pathway and the use of its ligands in human
breast cancer therapeutics.
design hypothesis to inhibit both dihydropteroate
synthase (DHPS) and dihydrofolate reductase (DHFR)
enzymes using a novel scheme that integrates our previous
antibiotic-phytochemical interaction data, fragment
combination and knowledge-based methods. Both the
enzymes are well established antibacterial targets from
folate biosynthesis pathway and their synergistic
modulation by a single hybrid entity may have profound
therapeutic benefits. Evaluation of the designed hybrid
compounds based on their physico-chemical properties has
indicated them as promising drug candidates with drug-like
pharmacotherapeutic profiles. In addition, the stereoelectronic
properties such as HOMO, LUMO and MEP
maps calculated by quantum chemical methods gave a good
correlation with the common pharmacophoric features
required for dual-site interactions. Furthermore, docking
and dynamics simulation studies reveal that the designed
hybrid compounds have favorable binding affinity and
stability in both pterin-binding site of DHPS and folatebinding
site of DHFR by forming strong hydrogen bonds
and hydrophobic interactions with key active-site residues.
Looking forward this study could serve as a prospective
lead in the process of new natural-product based hybriddrugs
development.
widely used packaging material primarily because of its
excellent mechanical properties, barrier properties against
water, light weight, low cost and high energy effectiveness.
However, due to its ubiquitous nature, and resistance to
biodegradability, the disposal strategies are crucial and
need attention. Recently, microorganisms have become the
focus of interest for environmental friendly disposal of
plastic and polymer-based waste. This manuscript aims to
investigate the extent of biodegradability of LDPE by four
different strains of Pseudomonas bacteria—Pseudomonas
aeruginosa PAO1 (ATCC 15729), Pseudomonas aeruginosa
(ATCC 15692), Pseudomonas putida (KT2440 ATCC
47054) and Pseudomonas syringae (DC3000 ATCC
10862). Degradation of LDPE was determined by weight
loss of the sample, morphological changes, mechanical and
spectroscopic variations. The eluted compounds after
degradation were analysed by gas chromatography coupled
with mass spectroscopy. Our results show that Pseudomonas
spp. can degrade LDPE films.
engineered by analyzing the redistribution of metabolic fluxes on specific gene modifications. Specifically,
the effects of metabolic gene deletions on flux distribution can be examined by forcing the fluxes of different
reactions catalyzed by the corresponding gene product to zero. However, the target enzyme needs to
be essential for survival of the organism to ensure that efficient chemical inhibition results in cell stasis or
death. Here, we investigate the essentiality of enzymes in iMO1056 metabolic model of nosocomial pathogen
Pseudomonas aeruginosa by performing in silico enzyme deletions using FBA. We identified 116/113
essential enzymes in rich medium in P. aeruginosa. These were then compared with human metabolic model
to identify nonhomologous enzymes that could be possible drug targets. Here, we present a refined list of 41
novel potential targets for P. aeruginosa. These targets were then matched with the enzymes belonging to 97
correlated clusters through which we propose the concept of “one target per cluster.” Our approach relates
to the “single drug multiple target (SDMT)” concept and has potential in efficient drug target discovery
(MIC) to the mutant prevention concentration (MPC). Placing antibiotic concentration in the MSW is expected
to selectively enrich mutant subpopulations while placing the concentration above the window is expected to restrict the
selective enrichment of resistant bacteria. Even though there is a rise of multidrug resistant bacteria, there are not many
new antibiotics introduced to market in the recent years. Therefore, there is a need to utilize existing knowledge on antibiotics
to prevent the development of multidrug resistance and if possible reposition the antibiotics. The increase in knowledge
on MSW and microbial evolution of resistance can be of potential use in novel dosing regimens and antimicrobial
combinations. In this study, we investigated the effect of the addition of ethyl gallate (EG) on the MSW and MPC of
MRSA ATCC strain 43300, before and after it has been induced to develop resistance to tetracycline and fusidic acid. It is
observed that tetracycline has narrower MSW than fusidic acid. This suggests that fusidic acid provides less genetic stability
than tetracycline and hence it is easy for mutants to develop. We also report that addition of ethyl gallate at
1024μg/ml closes the mutant selection window (i.e. MIC = MPC) of both tetracycline and fusidic acid, thus helping overcome
the effect of resistance developed over time. Hence, we propose that combination of ethyl gallate with antibiotics
has potential clinical implications and needs further exploration
trimethoprim, sulfamethoxazole, polymyxin B and piperacillin) and six phytochemicals
(protocatechuic acid, gallic acid, ellagic acid, rutin, berberine and myricetin) against five P.
aeruginosa isolates, alone and in combination are evaluated. All the phytochemicals under
investigation demonstrate potential inhibitory activity against P. aeruginosa. The combinations
of sulfamethoxazole plus protocatechuic acid, sulfamethoxazole plus ellagic acid, sulfamethoxazole
plus gallic acid and tetracycline plus gallic acid show synergistic mode of interaction.
However, the combinations of sulfamethoxazole plus myricetin shows synergism for three
strains (PA01, DB5218 and DR3062). The synergistic combinations are further evaluated for
their bactericidal activity against P. aeruginosa ATCC strain using time-kill method.
Sub-inhibitory dose responses of antibiotics and phytochemicals individually and in combination
are presented along with their interaction network to suggest on the mechanism of action
and potential targets for the phytochemicals under investigation. The identified synergistic
combinations can be of potent therapeutic value against P. aeruginosa infections. These
findings have potential implications in delaying the development of resistance as the antibacterial
effect is achieved with lower concentrations of both drugs (antibiotics and phytochemicals).
their serologic responses before and following receipt of the 2009 Southern Hemisphere seasonal
influenza vaccine.
Materials and methods: Paired serum samples were obtained before and 3–4 weeks after vaccination. Virus
microneutralization assays were performed to quantify antibodies against A/Brisbane/59/2007 vaccine,
pandemic H1N12009
and A/Puerto Rico/08/34 H1N1 strains.
Results: Postvaccination,
43%, 12% and 24% of subjects displayed a 4fold
or greater rise in neutralizing
antibody titers against the three strains, respectively. There was a positive correlation among individuals
whoshowed increased titers to both pandemic H1N12009
and A/Puerto Rico/08/34 (p < 0.001). However,
this correlation was not observed for A/Brisbane/59/2007 with either strain. The relative conservation
and accessibility of predicted Bcell
epitopes may explain the limited crossreactivity
of the antibodies
directed against common H1N1 epitopes.
Conclusions: These results suggest that seasonal influenza vaccination confers a certain degree of crossprotection
to other H1N1 strains. The correlation in crossreactive
antibody titers to A/Puerto Rico/08/34
and pandemic H1N12009
implies that previous exposure to pre1957
H1N1 strains may confer some
protection against the 2009 pandemic strain
poses a great challenge to public health and emphasizes
the need for new antimicrobial targets. The recent development
of microbial genomics and the availability of genome
sequences allows for the identification of essential
genes which could be novel and potential targets for antibacterial
drugs. However, these predicted targets need experimental
validation to confirm essentiality. Here, we report
on experimental validation of a two potential targets in the
lipopolysaccharide (LPS) biosynthesis pathway of the pathogen
Pseudomonas aeruginosa PAO1 using insertion duplication.
Two genes, kdsA and waaG , from LPS encoding proteins
2-dehydro-3-deoxyphosphooctonate aldolase and UDPglucose
(heptosyl) LPS -1,3-glucosyltransferase were selected as putative target candidates for the gene disruption experiments
using plasmid insertion mutagenesis to determine
essentiality. The introduction of a selectable ampicillin
and kanamycin resistance marker into the chromosome resulted
in lack of recovery of antibiotic-resistant co lonies suggesting
the essentiality of these genes for the survival of
P. aeruginosa . Several molecular analyses were carried out in
order to confirm the essentiality of these genes. We propose
that the above two validated drug targets are essential and
can be screened for functional inhibitors for the discovery of
novel therapeutic compounds against antibiotic-resistant
opportunistic pathogen P. aeruginosa
(MSSA) are highly resistant to some antibiotics and it is difficult to treat infections caused by Staphylococcus aureus.
This study evaluates the amount of Biofilm formation in four strains of MRSA and two strains of MSSA in presence of
three antibiotics (mupirocin, tetracycline, and fusidic acid), two phytochemicals (epicatechin gallate and ethyl gallate) as
single agents and in combination. Biofilm formation was quantified using spectrophotometry and visualized by Scanning
Electron Microscope. Our results show that the combination of tetracycline with ethyl gallate, and tetracycline with epicatechin
gallate were most effective in inhibiting the biofilm formation. It is interesting to observe that biofilm formation
is inhibited significantly at synergistic concentration of combinations of antibiotics and phytochemicals. These results can
be of potential therapeutic value towards development of new drugs for the prevention and treatment of infections caused
by drug- resistant biofilm forming bacteria
study shows that chitosan oligosaccharides have synergistic effect in combination with tetracycline, ceftriazone and sulfamethoxazole.
Also, high molecular weight chitosan was found to be effective against Staphylococcus aureus in combination with Sulfamethoxazole.
These results indicate the potential efficacy of chitosans in combinations with antibiotics for enhancing total biological activity
mupirocin, and fusidic acid are tested in combination with
Epicatechin Gallate (ECG), and Ethyl Gallate (EG) using 2
Methicillin resistant (MRSA) and 2 Methicillin sensitive
(MSSA) strains of Staphylococcus aureus. Sub-inhibitory
concentration of EG at 256mg l-1 is found to be synergistic
when used in combination with tetracycline, mupirocin,
and fusidic acid; and a sub-inhibitory concentration of ECG
at 32 mg l-1 is found to be synergistic with tetracycline in
all the four Staphylococcus aureus strains tested. The
synergistic combinations reduce the MICs of all the above
three antibiotics by 4 fold. Combining ECG at 32mg l-1
with mupirocin, reduces the MIC of mupirocin by four fold
in MSSA C1 strain. 74% of the combinations show
consistent results in both time-kill assay and checkerboard
method. The identified combinations may lead towards
novel therapeutic interventions for treating MRSA
infections
the development of resistance. In this study, the in vitro activities of antibiotic and phytochemical combinations
against Pseudomonas aeruginosa were tested by the fractional inhibitory concentration method, derived from
the minimal inhibitory concentrations (MICs) of the agents in combination.
Methods: The antimicrobial activity of phytochemicals, alone and in combination with antibiotics, was evaluated
using the checkerboard assay and time-kill curve methods.
Results: There was synergism between gentamicin and caffeic acid, and sulfadiazine and the 3 phytochemicals
under investigation (protocatechuic acid, quercetin, caffeic acid). The MIC of sulfadiazine was 256 μg/mL, and
of gentamicin was 2 μg/mL. When gentamicin was combined with one-quarter the MIC of caffeic acid, the MIC
of gentamicin was reduced 4-fold. When sulfadiazine was tested with one-quarter the MIC of protocatechuic
acid, quercetin, and caffeic acid, the MIC was reduced 4-fold in combination with each of the drugs.
Conclusions: These results indicate the potential efficacy of phytochemicals in combination with antibiotics for
enhancing total biological activity
applications in pharmaceutical preparations. In this study, 2 wild (ATCC 15729 and PAO1)
and 2 mutant strains (PT121 and PT149) of P. aeruginosa are investigated for drug-drug interactions
in vitro. 10 antimicrobial agents (antibiotics) are combined with different degree of
deacetylated Chitosans and Chitosan oligosaccharide. All the chitosans show synergistic activity
with sulfamethoxazole, a sulfonamide antimicrobial agent. It is interesting to observe
that the MIC value for the MexEF-OprN overexpressing mutant strain of P. aeruginosa is 5
fold higher than the other strains under investigation suggesting a possible role of this efflux
pump in Sulfamethoxazole efflux. The findings suggest on the use of chitosans as enhancing
agent in combination with antibiotics in pharmaceutical preparations.
that fuel diversity through ongoing interactions with other rapidly evolving molecules in the environment. This
paper discusses specific examples illustrating the phenomenon of diversity of hosts and pathogens, with special
reference to human papillomaviruses and H5N1 influenza viruses. We also review the influence of diverse host–
pathogen interactions that determine the pathophysiology of infections, and their responses to drugs or vaccines