Dataset Information

Evolution of antibiotic resistance in Salmonella enterica serovar typhimurium strains isolated in the Czech Republic between 1984 and 2002.

ABSTRACT: In a collection of 66 Salmonella enterica serovar Typhimurium strains isolated between 1984 and 2002 in the Czech Republic, genes coding for antibiotic resistance were determined by using specific PCRs. We found that the pentadrug-resistant ACSSuT clone first appeared in the Czech Republic in 1990. A new variant of the aadA gene designated aadA21 is described, the 5' end of which was identical to aadA2 and the 3' end of which was identical to aadA1.

SUBMITTER: Faldynova M

PROVIDER: S-EPMC155862 | biostudies-literature | 2003 Jun

REPOSITORIES: biostudies-literature

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Evolution of antibiotic resistance in Salmonella enterica serovar typhimurium strains isolated in the Czech Republic between 1984 and 2002.

Faldynova M M Pravcova M M Sisak F F Havlickova H H Kolackova I I Cizek A A Karpiskova R R Rychlik I I

Antimicrobial agents and chemotherapy 20030601 6

In a collection of 66 Salmonella enterica serovar Typhimurium strains isolated between 1984 and 2002 in the Czech Republic, genes coding for antibiotic resistance were determined by using specific PCRs. We found that the pentadrug-resistant ACSSuT clone first appeared in the Czech Republic in 1990. A new variant of the aadA gene designated aadA21 is described, the 5' end of which was identical to aadA2 and the 3' end of which was identical to aadA1. ...[more]

PMID: 12760885

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Project description:Microbial horizontal gene transfer is a continuous process that shapes bacterial genomic adaptation to the environment and the composition of concurrent microbial ecology. This includes the potential impact of synthetic antibiotic utilization in farm animal production on overall antibiotic resistance issues; however, the mechanisms behind the evolution of microbial communities are not fully understood. We explored potential mechanisms by experimentally examining the relatedness of phylogenetic inference between multidrug-resistant Salmonella enterica serovar Typhimurium isolates and pathogenic Salmonella Typhimurium strains based on genome-wide single-nucleotide polymorphism (SNP) comparisons. Antibiotic-resistant S Typhimurium isolates in a simulated farm environment barely lost their resistance, whereas sensitive S Typhimurium isolates in soils gradually acquired higher tetracycline resistance under antibiotic pressure and manipulated differential expression of antibiotic-resistant genes. The expeditious development of antibiotic resistance and the ensuing genetic alterations in antimicrobial resistance genes in S Typhimurium warrant effective actions to control the dissemination of Salmonella antibiotic resistance.IMPORTANCE Antibiotic resistance is attributed to the misuse or overuse of antibiotics in agriculture, and antibiotic resistance genes can also be transferred to bacteria under environmental stress. In this study, we report a unidirectional alteration in antibiotic resistance from susceptibility to increased resistance. Highly sensitive Salmonella enterica serovar Typhimurium isolates from organic farm systems quickly acquired tetracycline resistance under antibiotic pressure in simulated farm soil environments within 2 weeks, with expression of antibiotic resistance-related genes that was significantly upregulated. Conversely, originally resistant S Typhimurium isolates from conventional farm systems lost little of their resistance when transferred to environments without antibiotic pressure. Additionally, multidrug-resistant S Typhimurium isolates genetically shared relevancy with pathogenic S Typhimurium isolates, whereas susceptible isolates clustered with nonpathogenic strains. These results provide detailed discussion and explanation about the genetic alterations and simultaneous acquisition of antibiotic resistance in S Typhimurium in agricultural environments.

Project description:BackgroundBacterial genomes are mosaic structures composed of genes present in every strain of the same species (core genome), and genes present in some but not all strains of a species (accessory genome). The aim of this study was to compare the genetic diversity of core and accessory genes of a Salmonella enterica subspecies enterica serovar Typhimurium (Typhimurium) population isolated from food-animal and human sources in four regions of Mexico. Multilocus sequence typing (MLST) and macrorestriction fingerprints by pulsed-field gel electrophoresis (PFGE) were used to address the core genetic variation, and genes involved in pathogenesis and antibiotic resistance were selected to evaluate the accessory genome.ResultsWe found a low genetic diversity for both housekeeping and accessory genes. Sequence type 19 (ST19) was supported as the founder genotype of STs 213, 302 and 429. We found a temporal pattern in which the derived ST213 is replacing the founder ST19 in the four geographic regions analyzed and a geographic trend in the number of resistance determinants. The distribution of the accessory genes was not random among chromosomal genotypes. We detected strong associations among the different accessory genes and the multilocus chromosomal genotypes (STs). First, the Salmonella virulence plasmid (pSTV) was found mostly in ST19 isolates. Second, the plasmid-borne betalactamase cmy-2 was found only in ST213 isolates. Third, the most abundant integron, IP-1 (dfrA12, orfF and aadA2), was found only in ST213 isolates. Fourth, the Salmonella genomic island (SGI1) was found mainly in a subgroup of ST19 isolates carrying pSTV. The mapping of accessory genes and multilocus genotypes on the dendrogram derived from macrorestiction fingerprints allowed the establishment of genetic subgroups within the population.ConclusionDespite the low levels of genetic diversity of core and accessory genes, the non-random distribution of the accessory genes across chromosomal backgrounds allowed us to discover genetic subgroups within the population. This study provides information about the importance of the accessory genome in generating genetic variability within a bacterial population.

Dataset Information

Evolution of antibiotic resistance in Salmonella enterica serovar typhimurium strains isolated in the Czech Republic between 1984 and 2002.

Publications

Evolution of antibiotic resistance in Salmonella enterica serovar typhimurium strains isolated in the Czech Republic between 1984 and 2002.

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