Mechanisms of Antibiotic Resistance in Salmonella: Efflux Pumps, Genetics, Quorum Sensing and Biofilm Formation
31 Jan 2011-Letters in Drug Design & Discovery (Bentham Science Publishers Ltd)-Vol. 8, Iss: 2, pp 114-123
About: This article is published in Letters in Drug Design & Discovery.The article was published on 2011-01-31. It has received 15 citations till now. The article focuses on the topics: Quorum sensing & Biofilm.
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TL;DR: In this paper, a review summarizes data supporting the importance of exopolysaccharides during biofilm formation and its role in antibiotic resistance and strategies to overcome or attack biofilms are provided.
42 citations
TL;DR: It is suggested that sub-lethal concentrations of triclosan induce discernible changes in the proteome of exposed Salmonella and provide insights into mechanisms of response and tolerance.
38 citations
TL;DR: The results indicate that efflux pumps of MDR S. Typhimurium may contribute to resistance for at least one antibiotic, even in EtBr cartwheel test negative isolates.
Abstract: Introduction: Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium) is one of the major cause of foodborne zoonoses in humans. Poultry acts as a reservoir for S. Typhimurium without showing clinical signs and has become a source of infection to humans. Besides, it also became a source of multidrug-resistant (MDR) strains of S. Typhimurium.
Methods: In the present study, we have isolated 9 S. Typhimurium from 503 samples from environmental sources of poultry wet markets in the Kadapa District of Andhra Pradesh, India. The role of efflux pump activity in antibiotic resistance was evaluated by ethidium bromide cartwheel test and efflux pump inhibition assay.
Results: Eight out of nine isolates were resistant to two or more classes of antibiotics. The efflux pump activity of these isolates by ethidium bromide cartwheel method revealed that 66.6% isolates had shown evidence of pronounced efflux activity. The zone of inhibition (ZOI) of resistant antibiotics for each isolate was estimated in the presence or absence of 25 µg/mL of PAβN. Overall, cephalosporins (cefazolin, cefamandole, and cefaclor), kanamycin, polymyxin-B, piperacillin, and imipenem showed significant increase (≥2 mm) of ZOI, indicating the role of efflux pumps for efflux of these drugs. A maximum of 4 antibiotics among EtBr efflux pump positive isolates and 2 antibiotics among EtBr efflux pump negative isolates showed increased ZOI in the presence of PAβN.
Conclusion: The results indicate that efflux pumps of MDR S. Typhimurium may contribute to resistance for at least one antibiotic, even in EtBr cartwheel test negative isolates.
17 citations
Cites background from "Mechanisms of Antibiotic Resistance..."
...Efflux pumps of resistance nodulation division superfamily contribute to intrinsic and acquired resistance for wide variety of antibiotics.(7,9) The distribution of efflux-mediated drug resistance among Salmonella isolates is important to understand the mechanisms that occur in a natural selection process for antibiotic resistance....
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...Extrusion of antimicrobial compounds through efflux pumps is one of the mechanisms in antibiotic-resistant strains of foodborne pathogens.(7) Efflux pumps are classified into 5 major families namely, small multidrug-resistant family, major facilitator superfamily, adenosine triphosphate-binding cassette superfamily, multidrug and toxic compound extrusion family, and resistance nodulation division superfamily....
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...Efflux pumps are classified into 5 major families namely, small multidrug-resistant family, major facilitator superfamily, adenosine triphosphate-binding cassette superfamily, multidrug and toxic compound extrusion family, and resistance nodulation division superfamily.(7,8) Efflux pumps of resistance nodulation division superfamily contribute to intrinsic and acquired resistance for wide variety of antibiotics....
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TL;DR: Results indicate that cadmium, if acquired from the environment, being non-degradable can exert a long-lasting selective pressure on Salmonella in the host which may display antibiotic resistance later on, as a result of co-selection.
Abstract: In view of the reports on co-selection of metal and antibiotic resistance, recently we have reported that increased cadmium accumulation in Salmonella Typhi Ty2 leads to increased antibiotic resistance. In continuation, the present study was carried to substantiate this association in clinical isolates. Interestingly, the levels of cadmium were found to be more in the clinical isolates which co-related with their antibiotic sensitivity/resistance pattern. On cadmium accumulation, antibiotic(s) sensitive isolates were rendered resistant and the resistant isolates were rendered more resistant as per their minimum inhibitory concentration(s). Further, after subjecting the pathogen to cadmium accumulation, alterations occurring in the cells were assessed. Transgenerational cadmium exposure led to changes in growth response, morphology, proteome, elevated antioxidants other than SOD, increased biofilm formation, decreased intracellular macrophage killing coupled with upregulation of genes encoding metallothionein and metal transporters. Thus, these results indicate that cadmium, if acquired from the environment, being non-degradable can exert a long-lasting selective pressure on Salmonella in the host which may display antibiotic resistance later on, as a result of co-selection. Therefore, appropriate strategies need to be developed to inhibit such an enduring pressure of heavy metals, as these represent one of the factors for the emerging antibiotic resistance in pathogens.
9 citations
TL;DR: The results of this study suggest that mutations in the QRDRs or efflux pump could be involved in ciprofloxacin resistance, and that a combination of these mechanisms may lead to increased cipronolone resistance in LAB strains.
Abstract: Twenty-five strains of ciprofloxacin-resistant lactic acid bacteria (LAB; 14 Lactobacillus spp. and 11 Streptococcus thermophiles spp.) isolated from commercial yogurts in China were analyzed in this study. For each of these strains, amino acid changes associated with quinolone resistance-determining regions (QRDRs) were investigated using PCR-based detection methods. The same methodology was used to identify the presence of plasmid-mediated quinolone resistance (PMQR) genes in LAB. Sequencing analyses and an efflux pump inhibition test (using reserpine) were also performed as part of the analysis. Our results showed that typical mutations corresponding to quinolone resistance were found in the QRDRs of LAB strains. Detected mutations included Ser80Leu in parC, and Ser83Leu and Glu87Asp in gyrA. In addition, a Tyr74Phe substitution in parC, which had not previously been reported to be associated with quinolone resistance, was observed in two Lactobacillus delbrueckii subsp. bulgaricus strains. For each of the tested strains, the presence of the efflux pump inhibitor, reserpine, resulted in a two- to eightfold reduction in the minimum inhibitory concentrations (MICs) of ciprofloxacin. However, PMQR genes were not observed in any of the strains analyzed. Our results suggest that mutations in the QRDRs or efflux pump could be involved in ciprofloxacin resistance, and that a combination of these mechanisms may lead to increased ciprofloxacin resistance in LAB strains.
6 citations
Cites background from "Mechanisms of Antibiotic Resistance..."
...Previous studies have reported that quorum sensing and biofilm formation could contribute to antimicrobial resistance in many organisms (Davies 2003; Martins et al. 2011; Zhang et al. 2013)....
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