ABSTRACT
A total of 162 Salmonella isolates were isolated in samples from poultry farms, slaughterhouses, retail chicken meats, and human feces between 2012 and 2013. All extended-spectrum ß-lactamase-producing isolates had bla(CTX-M-15) gene sequence in their plasmids. This genotype may be related to multidrug resistance. Repetitive sequence-based polymerase chain reaction patterns among CTX-M-15 isolates were classified into 12 indistinguishable groups. CTX-M-15 isolates had various plasmid replicon types; however, the most frequent type was FIIS. This result suggests that bla(CTX-M-15) could be propagated via plasmid transfer.
Subject(s)
Poultry/microbiology , Salmonella/enzymology , Salmonella/isolation & purification , beta-Lactamases/metabolism , Animals , Bacterial Typing Techniques , Chickens , DNA, Bacterial/genetics , DNA, Bacterial/isolation & purification , Food Contamination , Food Microbiology , Genotyping Techniques , Republic of Korea , Salmonella/classification , Sequence Analysis, DNAABSTRACT
Multidrug-resistant foodborne pathogens are a leading public health concern, as antimicrobial resistance can lead to therapeutic failure. In this study, a ciprofloxacin-susceptible Salmonella Istanbul (Sal10-FC-KU12) was isolated from chicken meat obtained from a market in Korea to induce ciprofloxacin-resistant mutants (SalML, SalMM, and SalMH). Minimum inhibitory concentrations (MICs) of 12 antibiotics were measured in the presence or absence of an efflux pump inhibitor. Expression levels of efflux pump-related genes (acrB, acrF, marA, ramA, rob, and soxS) were determined using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Elevated MICs for the derived mutants were shown to result from the action of the efflux pump, with increased expression of marA, ramA, and acrB compared with the wild-type strain. The results of this study suggest that continued use of ciprofloxacin might induce the emergence of Salmonella mutants resistant not only to fluoroquinolones, but also to several other classes of antimicrobials.
Subject(s)
Bacterial Proteins/genetics , Ciprofloxacin/pharmacology , Drug Resistance, Multiple, Bacterial/drug effects , Fluoroquinolones/pharmacology , Gene Expression Regulation, Bacterial/drug effects , Membrane Transport Proteins/genetics , Salmonella enterica/genetics , Animals , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/metabolism , Carrier Proteins/antagonists & inhibitors , Carrier Proteins/drug effects , Carrier Proteins/genetics , Chickens , Drug Resistance, Multiple, Bacterial/genetics , Escherichia coli Proteins/antagonists & inhibitors , Escherichia coli Proteins/drug effects , Escherichia coli Proteins/genetics , Gene Expression Regulation, Bacterial/genetics , Membrane Transport Proteins/metabolism , Microbial Sensitivity Tests/methods , Microbial Sensitivity Tests/veterinary , Mutation/genetics , Poultry Products/microbiology , Republic of Korea , Reverse Transcriptase Polymerase Chain Reaction/methods , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Salmonella enterica/metabolismABSTRACT
Of the Salmonella enterica serovars, S. Enteritidis and S. Typhimurium are responsible for most of the Salmonella outbreaks implicated in the consumption of contaminated foods in the Republic of Korea. Because of the widespread occurrence of antimicrobial-resistant Salmonella in foods and food processing environments, bacteriophages have recently surfaced as an alternative biocontrol tool. In this study, we isolated a virulent bacteriophage (wksl3) that could specifically infect S. Enteritidis, S. Typhimurium, and several additional serovars. Transmission electron microscopy revealed that phage wksl3 belongs to the family Siphoviridae. Complete genome sequence analysis and bioinformatic analysis revealed that the DNA of phage wksl3 is composed of 42,766 bp with 64 open reading frames. Since it does not encode any phage lysogeny factors, toxins, pathogen-related genes, or food-borne allergens, phage wksl3 may be considered a virulent phage with no side effects. Analysis of genetic similarities between phage wksl3 and four of its relatives (SS3e, vB_SenS-Ent1, SE2, and SETP3) allowed wksl3 to be categorized as a SETP3-like phage. A single-dose test of oral toxicity with BALB/c mice resulted in no abnormal clinical observations. Moreover, phage application to chicken skin at 8°C resulted in an about 2.5-log reduction in the number of Salmonella bacteria during the test period. The strong, stable lytic activity, the significant reduction of the number of S. Enteritidis bacteria after application to food, and the lack of clinical symptoms of this phage suggest that wksl3 may be a useful agent for the protection of foods against S. Enteritidis and S. Typhimurium contamination.
