Bacterial infections pose a serious public health concern, especially when an infectious disease ... more Bacterial infections pose a serious public health concern, especially when an infectious disease has a multidrug resistant causative agent. Such multidrug resistant bacteria can compromise the clinical utility of major chemotherapeutic antimicrobial agents. Drug and multidrug resistant bacteria harbor several distinct molecular mechanisms for resistance. Bacterial antimicrobial agent efflux pumps represent a major mechanism of clinical resistance. The major facilitator superfamily (MFS) is one of the largest groups of solute transporters to date and includes a significant number of bacterial drug and multidrug efflux pumps. We review recent work on the modulation of multidrug efflux pumps, paying special attention to those transporters belonging primarily to the MFS.
The bacterium Vibrio cholerae is the causative agent of cholera, a severe gastrointestinal diseas... more The bacterium Vibrio cholerae is the causative agent of cholera, a severe gastrointestinal disease characterized primarily by the excretion of large amounts of the so-called rice water stool, which contains critical electrolytes and water. Cholera patients may succumb very quickly to the resulting severe dehydration producing significant morbidity and mortality rates. According to the World Health Organization (WHO), approximately 3-5 million cases of cholera occur each year with 100,000-120,000 yearly estimated deaths. Clearly, V. cholerae represents a critical public health concern 1. Key therapeutic efforts against cholera in humans include electrolyte replenishment, and for severe cholera cases, antimicrobial agents, such as tetracycline, furazolidone, ciprofloxacin, and trimethoprimsulphamethoxazole 2. Though antimicrobials shorten the duration of illness and reduce faecal shedding of V. cholerae, prolonged antimicrobial use results in the development of antimicrobial resistance. Strains of V. cholerae have emerged that are resistant not only to each of these antimicrobial agents but also to multiple drugs, further confounding treatment efforts against cholera 3. Bacterial antimicrobial resistance mechanisms consist of enzymatic drug inactivation, drug target protection, reduced drug permeability into bacterial cells, biofilm protection, alteration of drug target, alteration of metabolite pathways, and active efflux of single and multiple drugs from cells 3. Active multidrug efflux is a major mechanism for bacterial pathogen drug resistance 4. Efflux pumps are integral-membrane proteins that confer single-and multi-drug resistances by actively extruding drugs from bacterial pathogens 4,5. We discovered a new multi-drug efflux pump, called EmrD-3, from V. cholerae O395 6. EmrD-3 confers resistance in V. cholerae against linezolid, rifampin,
International Journal of Environmental Research and Public Health, 2015
Foodborne illnesses caused by bacterial microorganisms are common worldwide and constitute a seri... more Foodborne illnesses caused by bacterial microorganisms are common worldwide and constitute a serious public health concern. In particular, microorganisms belonging to the Enterobacteriaceae and Vibrionaceae families of Gram-negative bacteria, and to the Staphylococcus genus of Gram-positive bacteria are important causative agents of food poisoning and infection in the gastrointestinal tract of humans. Recently, variants of these bacteria have developed resistance to medically important chemotherapeutic agents. Multidrug resistant Escherichia coli, Salmonella enterica, Vibrio cholerae, Enterobacter spp., and Staphylococcus aureus are becoming increasingly recalcitrant to clinical treatment in human patients. Of the various bacterial resistance mechanisms against antimicrobial agents,
The purpose of this study was to examine the sugar recognition and transport properties of the su... more The purpose of this study was to examine the sugar recognition and transport properties of the sucrose permease (CscB), a secondary active transporter from Escherichia coli. We tested the hypothesis that maltose transport is conferred by the wild-type CscB transporter. Cells of E. coli HS4006 harboring pSP72/cscB were red on maltose MacConkey agar indicator plates. We were able to measure "downhill" maltose transport and establish definitive kinetic behavior for maltose entry in such cells. Maltose was an effective competitor of sucrose transport in cells with CscB, suggesting that the respective maltose and sucrose binding sites and translocation pathways through the CscB channel overlap. Accumulation ("uphill" transport) of maltose by cells with CscB was profound, demonstrating active transport of maltose by CscB. Sequencing of cscB encoded on plasmid pSP72/ cscB used in cells for transport studies indicate an unaltered primary CscB structure, ruling out the possibility that mutation conferred maltose transport by CscB. We conclude that maltose is a bona fide substrate for the sucrose permease of E. coli. Thus, future studies of sugar binding, transport and permease structure should consider maltose, as well as sucrose.
Pathogenic and opportunistic bacteria which are causative agents of infectious disease and harbor... more Pathogenic and opportunistic bacteria which are causative agents of infectious disease and harbor effective drug resistance mechanisms may confound treatment in human clinical medicine. Of the various antimicrobial agent resistant mechanisms, active efflux by secondary active transporter systems, called drug efflux pumps, are commonly found within infectious disease causing bacteria. These secondary active drug efflux systems are energized by cation gradients and may have single or multiple drug substrates. It is these multidrug efflux systems that compromise chemotherapeutic efforts against multiple drug resistant bacteria. Close scrutiny of these multidrug efflux systems may provide useful molecular information for potential modulation in order to reduce the conditions that foster bacterial drug resistance and thus possibly restore clinical efficacy of antimicrobial agents. This chapter focuses on key bacterial secondary drug efflux pump systems from a molecular perspective.
Vibrio cholerae is a Gram-negative bacterium and causative agent of cholera , which is a severe g... more Vibrio cholerae is a Gram-negative bacterium and causative agent of cholera , which is a severe gastrointestinal disease and a global public health concern. Repletion and antimicrobial drug therapies are necessary for efficacious treatment of severe cases of cholera. In situations where proper sanitation and repletion therapy are unavailable and multidrug resistant V. cholerae variants are present, alternative means of therapy are indicated. Towards this, comparative genomic analyses between virulent versus non-virulent serotypes of V. cholerae have been useful in identifying new cellular targets for the development of new chemotherapies for cholera. This review article explores these new avenues for cholera treatments and summarizes these novel putative drug targets.
Biotechnological Applications of Quorum Sensing Inhibitors, 2018
Bacterial pathogenesis is frequently enhanced by virulence mechanisms that facilitate growth. Suc... more Bacterial pathogenesis is frequently enhanced by virulence mechanisms that facilitate growth. Such virulence factors include biofilm formation and antimicrobial resistance mechanisms. One primary resistance mechanism involves the active efflux of antimicrobial agents from cells of pathogenic bacteria. It has been established that quorum sensing serves as a line of communication between the environment and mechanisms of antimicrobial resistance, such as antimicrobial efflux pump systems from bacterial pathogens. This chapter covers several well documented antimicrobial efflux transporter resistance mechanisms and their relationships to key aspects of quorum sensing. Knowledge of these critical relationships may enhance their biotechnological applications.
With the advent of new molecular tools, new taxa of sulphur-oxidising bacteria (SOB) in diverse e... more With the advent of new molecular tools, new taxa of sulphur-oxidising bacteria (SOB) in diverse environments are being discovered. However, there is a significant gap of knowledge about the ecology and diversity of SOB in thermal springs. Here, the species diversity and phylogenetic affiliations of SOB were investigated using 16S rRNA and functional gene marker, soxB in thermal springs of Thane district of Maharashtra, India. Most SOB detected by 16S rDNA sequences belong to different operational taxonomic units (OTU's): Firmicutes, α-, β-, γ-Proteobacteria and Actinobacteria with the dominance of first class. However, the soxB gene clone library sequences had shown affiliation with the β-, γ-and α-Proteobacteria. β-Proteobacteria-related sequences were dominant, with 53.3% clones belonging to genus Hydrogenophaga. The thiosulphate oxidation assay carried out for different isolates having distinct identity showed the mean sulphate-sulphur production from 117.86 ± 0.50 to 218.82 ± 2.56 mg SO 4-S l −1 after 9 days of incubation. Also, sulphur oxidation by the genus Nitratireductor, Caldimonas, Geobacillus, Paenibacillus, Brevibacillus, Tristrella and Chelatococcus has been reported for the first time that reveals ecological widening over which thiotrophs are distributed.
The Paracoccus sp. is one of the best-characterized prokaryote that has served as a model organis... more The Paracoccus sp. is one of the best-characterized prokaryote that has served as a model organism to study the dentrification and sulphur oxidation processes. However, its ability of dentrification and sulphur oxidation in coastal shrimp ponds is not reported much. In the present work, the Gram-negative, neutrophilic, facultatively lithoautotrophic bacterium Paracoccus saliphilus strain SPUM isolated from coastal shrimp ponds of Urran, Maharashtra, was studied for its efficiency of simultaneous heterotrophic nitrification–aerobic denitrification and sulphur oxidation processes. The maximum removal rate of nitrite and nitrate was 11.22 ± 0.31 and 14.17 ± 0.31 mg of NO3-N/l respectively after 24 h of incubation, while the sulphate-sulphur production observed was 190 ± 4.3 mg l−1 with a change in pH from 8.0 to 7.4 ± 0.08 after 12 days of incubation. The strain was characterized using universal 16S rRNA gene primers revealing high similarity (> 99%) with Paracoccus saliphilus belonging to α-proteobacteria. The isolate could express sulphate thiolesterase/sulphate thiohydrolase, soxB gene which is essential for sulphur oxidation. From all the results, it has been found that the strain SPUM could play a major role in simultaneous aerobic nitrification/denitrification and sulphur oxidation processes to overcome the toxicity of nitrogenous and sulphur-reducing compounds respectively in coastal aquaculture and wastewater systems.
Variants of the microorganism Staphylococcus aureus which are resistant to antimicrobial agents e... more Variants of the microorganism Staphylococcus aureus which are resistant to antimicrobial agents exist as causative agents of serious infectious disease and constitute a considerable public health concern. One of the main antimicrobial resistance mechanisms harbored by S. aureus pathogens is exemplified by integral membrane transport systems that actively remove antimicrobial agents from bacteria where the cytoplasmic drug targets reside, thus allowing the bacteria to survive and grow. An important class of solute transporter proteins, called the major facilitator superfamily, includes related and homologous passive and secondary active transport systems, many of which are antimicrobial efflux pumps. Transporters of the major facilitator superfamily, which confer antimicrobial efflux and bacterial resistance in S. aureus, are good targets for development of resistance-modifying agents, such as efflux pump inhibition. Such modulatory action upon these antimicrobial efflux systems of the major facilitator superfamily in S. aureus may circumvent resistance and restore the clinical efficacy of therapy towards S. aureus infection.
Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when ... more Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when they are the causative agents of infectious disease. These multi-drug resistance mechanisms allow bacteria to survive in the presence of clinically useful antimicrobial agents, thus reducing the efficacy of chemotherapy towards infectious disease. Importantly, active multi-drug efflux is a major mechanism for bacterial pathogen drug resistance. Therefore, because of their overwhelming presence in bacterial pathogens, these active multi-drug efflux mechanisms remain a major area of intense study, so that ultimately measures may be discovered to inhibit these active multi-drug efflux pumps.
World Journal of Microbiology and Biotechnology, 2008
Biofilms formed by the human pathogen Listeria monocytogenes in food processing environments can ... more Biofilms formed by the human pathogen Listeria monocytogenes in food processing environments can be a potential source of contamination. In this study, we investigated the ability of L. monocytogenes wild type and its laboratory derived isogenic mutants in cwhA, prfA, agrA, flaA, degU, ami and sigB to adhere to and form biofilms on abiotic surfaces. The results suggest that inactivation of the two component regulatory system degU completely abolished biofilm formation, while inactivation of the flagellar gene flaA, two component response regulator agrA and the autolysin-adhesin gene ami lead to severe impairment of initial attachment and the subsequent development of a mature biofilm by L. monocytogenes. Mutants in global regulator of virulence prfA and the alternative sigma factor sigB were unaffected and formed biofilms similar to the wild type L. monocytogenes.
Detection of whitespot syndrome virus (WSSV) in cultured shrimps (Penaeus monodon), P. monodon br... more Detection of whitespot syndrome virus (WSSV) in cultured shrimps (Penaeus monodon), P. monodon brooders, shrimp postlarvae and water samples in Bangladesh was carried out by Polymerase chain reaction (PCR) using five different pairs of primers yielding amplicons ranging from 310 to 2310 bp. The primer pairs used in this study are designated as KF 1-2 (2310 bp), Lo 1-2 (1447 bp), Lo 5-6 (775 bp), IK 1-2 (486 bp) and IK 3-4 (310 bp). Out of 42 cultured shrimp tested, 36 were positive for WSSV, with 18 by non-nested reaction and 18 by nested reaction. In nonnested reaction only one shrimp sample showed positive for WSSV with all the five primer pairs, four showed positive with primer pairs Lo 1-2, Lo 5-6, IK 1-2 and IK 3-4, two showed positive with primer pairs Lo 5-6, IK 1-2 and IK 3-4, 2 positive with primer pairs IK 1-2 and IK 3-4 and nine showed positive with primer pairs IK 3-4 only. In nested reaction all the 18 samples showed positive with primer pairs IK 1-2 and IK 3-4. All the five brooders were positive for WSSV by non-nested PCR with primers IK 3-4 and only one was positive by primers yielding higher fragments. Out of 18 post larvae tested, two were positive by nested reaction using IK 1-2 and IK 3-4. Among 12 water samples analysed, three showed positive in non-nested reaction with primers IK 3-4 only and five showed positive in nested reaction with primers IK 1-2 and IK 3-4. All the PCR products were further confirmed by dot blot hybridization using biotinylated probe.
A multidrug efflux pump designated LmrS (lincomycin resistance protein of Staphylococcus aureus),... more A multidrug efflux pump designated LmrS (lincomycin resistance protein of Staphylococcus aureus), belonging to the major facilitator superfamily (MFS) of transporters, was cloned, and the role of LmrS in antimicrobial efflux was evaluated. The highest relative increase in MIC, 16-fold, was observed for linezolid and tetraphenylphosphonium chloride (TPCL), followed by an 8-fold increase for sodium dodecyl sulfate (SDS), trimethoprim, and chloramphenicol. LmrS has 14 predicted membrane-spanning domains and is homologous to putative lincomycin resistance proteins of Bacillus spp., Lactobacillus spp., and Listeria spp.
Bacterial infections pose a serious public health concern, especially when an infectious disease ... more Bacterial infections pose a serious public health concern, especially when an infectious disease has a multidrug resistant causative agent. Such multidrug resistant bacteria can compromise the clinical utility of major chemotherapeutic antimicrobial agents. Drug and multidrug resistant bacteria harbor several distinct molecular mechanisms for resistance. Bacterial antimicrobial agent efflux pumps represent a major mechanism of clinical resistance. The major facilitator superfamily (MFS) is one of the largest groups of solute transporters to date and includes a significant number of bacterial drug and multidrug efflux pumps. We review recent work on the modulation of multidrug efflux pumps, paying special attention to those transporters belonging primarily to the MFS.
The bacterium Vibrio cholerae is the causative agent of cholera, a severe gastrointestinal diseas... more The bacterium Vibrio cholerae is the causative agent of cholera, a severe gastrointestinal disease characterized primarily by the excretion of large amounts of the so-called rice water stool, which contains critical electrolytes and water. Cholera patients may succumb very quickly to the resulting severe dehydration producing significant morbidity and mortality rates. According to the World Health Organization (WHO), approximately 3-5 million cases of cholera occur each year with 100,000-120,000 yearly estimated deaths. Clearly, V. cholerae represents a critical public health concern 1. Key therapeutic efforts against cholera in humans include electrolyte replenishment, and for severe cholera cases, antimicrobial agents, such as tetracycline, furazolidone, ciprofloxacin, and trimethoprimsulphamethoxazole 2. Though antimicrobials shorten the duration of illness and reduce faecal shedding of V. cholerae, prolonged antimicrobial use results in the development of antimicrobial resistance. Strains of V. cholerae have emerged that are resistant not only to each of these antimicrobial agents but also to multiple drugs, further confounding treatment efforts against cholera 3. Bacterial antimicrobial resistance mechanisms consist of enzymatic drug inactivation, drug target protection, reduced drug permeability into bacterial cells, biofilm protection, alteration of drug target, alteration of metabolite pathways, and active efflux of single and multiple drugs from cells 3. Active multidrug efflux is a major mechanism for bacterial pathogen drug resistance 4. Efflux pumps are integral-membrane proteins that confer single-and multi-drug resistances by actively extruding drugs from bacterial pathogens 4,5. We discovered a new multi-drug efflux pump, called EmrD-3, from V. cholerae O395 6. EmrD-3 confers resistance in V. cholerae against linezolid, rifampin,
International Journal of Environmental Research and Public Health, 2015
Foodborne illnesses caused by bacterial microorganisms are common worldwide and constitute a seri... more Foodborne illnesses caused by bacterial microorganisms are common worldwide and constitute a serious public health concern. In particular, microorganisms belonging to the Enterobacteriaceae and Vibrionaceae families of Gram-negative bacteria, and to the Staphylococcus genus of Gram-positive bacteria are important causative agents of food poisoning and infection in the gastrointestinal tract of humans. Recently, variants of these bacteria have developed resistance to medically important chemotherapeutic agents. Multidrug resistant Escherichia coli, Salmonella enterica, Vibrio cholerae, Enterobacter spp., and Staphylococcus aureus are becoming increasingly recalcitrant to clinical treatment in human patients. Of the various bacterial resistance mechanisms against antimicrobial agents,
The purpose of this study was to examine the sugar recognition and transport properties of the su... more The purpose of this study was to examine the sugar recognition and transport properties of the sucrose permease (CscB), a secondary active transporter from Escherichia coli. We tested the hypothesis that maltose transport is conferred by the wild-type CscB transporter. Cells of E. coli HS4006 harboring pSP72/cscB were red on maltose MacConkey agar indicator plates. We were able to measure "downhill" maltose transport and establish definitive kinetic behavior for maltose entry in such cells. Maltose was an effective competitor of sucrose transport in cells with CscB, suggesting that the respective maltose and sucrose binding sites and translocation pathways through the CscB channel overlap. Accumulation ("uphill" transport) of maltose by cells with CscB was profound, demonstrating active transport of maltose by CscB. Sequencing of cscB encoded on plasmid pSP72/ cscB used in cells for transport studies indicate an unaltered primary CscB structure, ruling out the possibility that mutation conferred maltose transport by CscB. We conclude that maltose is a bona fide substrate for the sucrose permease of E. coli. Thus, future studies of sugar binding, transport and permease structure should consider maltose, as well as sucrose.
Pathogenic and opportunistic bacteria which are causative agents of infectious disease and harbor... more Pathogenic and opportunistic bacteria which are causative agents of infectious disease and harbor effective drug resistance mechanisms may confound treatment in human clinical medicine. Of the various antimicrobial agent resistant mechanisms, active efflux by secondary active transporter systems, called drug efflux pumps, are commonly found within infectious disease causing bacteria. These secondary active drug efflux systems are energized by cation gradients and may have single or multiple drug substrates. It is these multidrug efflux systems that compromise chemotherapeutic efforts against multiple drug resistant bacteria. Close scrutiny of these multidrug efflux systems may provide useful molecular information for potential modulation in order to reduce the conditions that foster bacterial drug resistance and thus possibly restore clinical efficacy of antimicrobial agents. This chapter focuses on key bacterial secondary drug efflux pump systems from a molecular perspective.
Vibrio cholerae is a Gram-negative bacterium and causative agent of cholera , which is a severe g... more Vibrio cholerae is a Gram-negative bacterium and causative agent of cholera , which is a severe gastrointestinal disease and a global public health concern. Repletion and antimicrobial drug therapies are necessary for efficacious treatment of severe cases of cholera. In situations where proper sanitation and repletion therapy are unavailable and multidrug resistant V. cholerae variants are present, alternative means of therapy are indicated. Towards this, comparative genomic analyses between virulent versus non-virulent serotypes of V. cholerae have been useful in identifying new cellular targets for the development of new chemotherapies for cholera. This review article explores these new avenues for cholera treatments and summarizes these novel putative drug targets.
Biotechnological Applications of Quorum Sensing Inhibitors, 2018
Bacterial pathogenesis is frequently enhanced by virulence mechanisms that facilitate growth. Suc... more Bacterial pathogenesis is frequently enhanced by virulence mechanisms that facilitate growth. Such virulence factors include biofilm formation and antimicrobial resistance mechanisms. One primary resistance mechanism involves the active efflux of antimicrobial agents from cells of pathogenic bacteria. It has been established that quorum sensing serves as a line of communication between the environment and mechanisms of antimicrobial resistance, such as antimicrobial efflux pump systems from bacterial pathogens. This chapter covers several well documented antimicrobial efflux transporter resistance mechanisms and their relationships to key aspects of quorum sensing. Knowledge of these critical relationships may enhance their biotechnological applications.
With the advent of new molecular tools, new taxa of sulphur-oxidising bacteria (SOB) in diverse e... more With the advent of new molecular tools, new taxa of sulphur-oxidising bacteria (SOB) in diverse environments are being discovered. However, there is a significant gap of knowledge about the ecology and diversity of SOB in thermal springs. Here, the species diversity and phylogenetic affiliations of SOB were investigated using 16S rRNA and functional gene marker, soxB in thermal springs of Thane district of Maharashtra, India. Most SOB detected by 16S rDNA sequences belong to different operational taxonomic units (OTU's): Firmicutes, α-, β-, γ-Proteobacteria and Actinobacteria with the dominance of first class. However, the soxB gene clone library sequences had shown affiliation with the β-, γ-and α-Proteobacteria. β-Proteobacteria-related sequences were dominant, with 53.3% clones belonging to genus Hydrogenophaga. The thiosulphate oxidation assay carried out for different isolates having distinct identity showed the mean sulphate-sulphur production from 117.86 ± 0.50 to 218.82 ± 2.56 mg SO 4-S l −1 after 9 days of incubation. Also, sulphur oxidation by the genus Nitratireductor, Caldimonas, Geobacillus, Paenibacillus, Brevibacillus, Tristrella and Chelatococcus has been reported for the first time that reveals ecological widening over which thiotrophs are distributed.
The Paracoccus sp. is one of the best-characterized prokaryote that has served as a model organis... more The Paracoccus sp. is one of the best-characterized prokaryote that has served as a model organism to study the dentrification and sulphur oxidation processes. However, its ability of dentrification and sulphur oxidation in coastal shrimp ponds is not reported much. In the present work, the Gram-negative, neutrophilic, facultatively lithoautotrophic bacterium Paracoccus saliphilus strain SPUM isolated from coastal shrimp ponds of Urran, Maharashtra, was studied for its efficiency of simultaneous heterotrophic nitrification–aerobic denitrification and sulphur oxidation processes. The maximum removal rate of nitrite and nitrate was 11.22 ± 0.31 and 14.17 ± 0.31 mg of NO3-N/l respectively after 24 h of incubation, while the sulphate-sulphur production observed was 190 ± 4.3 mg l−1 with a change in pH from 8.0 to 7.4 ± 0.08 after 12 days of incubation. The strain was characterized using universal 16S rRNA gene primers revealing high similarity (> 99%) with Paracoccus saliphilus belonging to α-proteobacteria. The isolate could express sulphate thiolesterase/sulphate thiohydrolase, soxB gene which is essential for sulphur oxidation. From all the results, it has been found that the strain SPUM could play a major role in simultaneous aerobic nitrification/denitrification and sulphur oxidation processes to overcome the toxicity of nitrogenous and sulphur-reducing compounds respectively in coastal aquaculture and wastewater systems.
Variants of the microorganism Staphylococcus aureus which are resistant to antimicrobial agents e... more Variants of the microorganism Staphylococcus aureus which are resistant to antimicrobial agents exist as causative agents of serious infectious disease and constitute a considerable public health concern. One of the main antimicrobial resistance mechanisms harbored by S. aureus pathogens is exemplified by integral membrane transport systems that actively remove antimicrobial agents from bacteria where the cytoplasmic drug targets reside, thus allowing the bacteria to survive and grow. An important class of solute transporter proteins, called the major facilitator superfamily, includes related and homologous passive and secondary active transport systems, many of which are antimicrobial efflux pumps. Transporters of the major facilitator superfamily, which confer antimicrobial efflux and bacterial resistance in S. aureus, are good targets for development of resistance-modifying agents, such as efflux pump inhibition. Such modulatory action upon these antimicrobial efflux systems of the major facilitator superfamily in S. aureus may circumvent resistance and restore the clinical efficacy of therapy towards S. aureus infection.
Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when ... more Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when they are the causative agents of infectious disease. These multi-drug resistance mechanisms allow bacteria to survive in the presence of clinically useful antimicrobial agents, thus reducing the efficacy of chemotherapy towards infectious disease. Importantly, active multi-drug efflux is a major mechanism for bacterial pathogen drug resistance. Therefore, because of their overwhelming presence in bacterial pathogens, these active multi-drug efflux mechanisms remain a major area of intense study, so that ultimately measures may be discovered to inhibit these active multi-drug efflux pumps.
World Journal of Microbiology and Biotechnology, 2008
Biofilms formed by the human pathogen Listeria monocytogenes in food processing environments can ... more Biofilms formed by the human pathogen Listeria monocytogenes in food processing environments can be a potential source of contamination. In this study, we investigated the ability of L. monocytogenes wild type and its laboratory derived isogenic mutants in cwhA, prfA, agrA, flaA, degU, ami and sigB to adhere to and form biofilms on abiotic surfaces. The results suggest that inactivation of the two component regulatory system degU completely abolished biofilm formation, while inactivation of the flagellar gene flaA, two component response regulator agrA and the autolysin-adhesin gene ami lead to severe impairment of initial attachment and the subsequent development of a mature biofilm by L. monocytogenes. Mutants in global regulator of virulence prfA and the alternative sigma factor sigB were unaffected and formed biofilms similar to the wild type L. monocytogenes.
Detection of whitespot syndrome virus (WSSV) in cultured shrimps (Penaeus monodon), P. monodon br... more Detection of whitespot syndrome virus (WSSV) in cultured shrimps (Penaeus monodon), P. monodon brooders, shrimp postlarvae and water samples in Bangladesh was carried out by Polymerase chain reaction (PCR) using five different pairs of primers yielding amplicons ranging from 310 to 2310 bp. The primer pairs used in this study are designated as KF 1-2 (2310 bp), Lo 1-2 (1447 bp), Lo 5-6 (775 bp), IK 1-2 (486 bp) and IK 3-4 (310 bp). Out of 42 cultured shrimp tested, 36 were positive for WSSV, with 18 by non-nested reaction and 18 by nested reaction. In nonnested reaction only one shrimp sample showed positive for WSSV with all the five primer pairs, four showed positive with primer pairs Lo 1-2, Lo 5-6, IK 1-2 and IK 3-4, two showed positive with primer pairs Lo 5-6, IK 1-2 and IK 3-4, 2 positive with primer pairs IK 1-2 and IK 3-4 and nine showed positive with primer pairs IK 3-4 only. In nested reaction all the 18 samples showed positive with primer pairs IK 1-2 and IK 3-4. All the five brooders were positive for WSSV by non-nested PCR with primers IK 3-4 and only one was positive by primers yielding higher fragments. Out of 18 post larvae tested, two were positive by nested reaction using IK 1-2 and IK 3-4. Among 12 water samples analysed, three showed positive in non-nested reaction with primers IK 3-4 only and five showed positive in nested reaction with primers IK 1-2 and IK 3-4. All the PCR products were further confirmed by dot blot hybridization using biotinylated probe.
A multidrug efflux pump designated LmrS (lincomycin resistance protein of Staphylococcus aureus),... more A multidrug efflux pump designated LmrS (lincomycin resistance protein of Staphylococcus aureus), belonging to the major facilitator superfamily (MFS) of transporters, was cloned, and the role of LmrS in antimicrobial efflux was evaluated. The highest relative increase in MIC, 16-fold, was observed for linezolid and tetraphenylphosphonium chloride (TPCL), followed by an 8-fold increase for sodium dodecyl sulfate (SDS), trimethoprim, and chloramphenicol. LmrS has 14 predicted membrane-spanning domains and is homologous to putative lincomycin resistance proteins of Bacillus spp., Lactobacillus spp., and Listeria spp.
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Papers by Sanath Kumar