Antimicrobial Resistance-Conferring Plasmids with Similarity to Virulence Plasmids from Avian Pathogenic Escherichia coli Strains in Salmonella enterica Serovar Kentucky Isolates from Poultry

Abstract

Salmonella enterica, a leading cause of food-borne gastroenteritis worldwide, may be found in any raw food of animal, vegetable, or fruit origin. Salmonella serovars differ in distribution, virulence, and host specificity. Salmonella enterica serovar Kentucky, though often found in the food supply, is less commonly isolated from ill humans. The multidrug-resistant isolate S. Kentucky CVM29188, isolated from a chicken breast sample in 2003, contains three plasmids (146,811 bp, 101,461 bp, and 46,121 bp), two of which carry resistance determinants (pCVM29188_146 [strAB and tetRA] and pCVM29188_101 [bla CMY-2 and sugE]). Both resistance plasmids were transferable by conjugation, alone or in combination, to S. Kentucky, Salmonella enterica serovar Newport, and Escherichia coli recipients. pCVM29188_146 shares a highly conserved plasmid backbone of 106 kb (>90% nucleotide identity) with two virulence plasmids from avian pathogenic Escherichia coli strains (pAPEC-O1-ColBM and pAPEC-O2-ColV). Shared avian pathogenic E. coli (APEC) virulence factors include iutA iucABCD, sitABCD, etsABC, iss, and iroBCDEN. PCR analyses of recent (1997 to 2005) S. Kentucky isolates from food animal, retail meat, and human sources revealed that 172 (60%) contained similar APEC-like plasmid backbones. Notably, though rare in human-and cattle-derived isolates, this plasmid backbone was found at a high frequency (50 to 100%) among S. Kentucky isolates from chickens within the same time span. Ninety-four percent of the APEC-positive isolates showed resistance to tetracycline and streptomycin. Together, our findings of a resistance-conferring APEC virulence plasmid in a poultry-derived S. Kentucky isolate and of similar resistance/virulence plasmids in most recent S. Kentucky isolates from chickens and, to lesser degree, from humans and cattle highlight the need for additional research in order to examine the prevalence and spread of combined virulence and resistance plasmids in bacteria in agricultural, environmental, and clinical settings.

Pathogenomics of the Virulence Plasmids ofEscherichia coli

“…pCVM29188_146 originated from an S. enterica subsp. enterica serovar Kentucky isolate from retail chicken breast (60). Despite the diverse sources from which these plasmids originated, their core genetic constitution remains remarkably conserved (Fig.…”

Antimicrobial susceptibility and pathogenicity of Escherichia coli strains of environmental origin

“…Pathogenicity, as well as the high levels of antimicrobial resistance can be explained, likely, by the exchange of genetic material between different bacterial strains, where genes involved in virulence and resistance are constantly transferred, mostly mediated by plasmids. As reported by FLORIAN FRICKE et al (2009), a single plasmid can possess genes responsible for both antimicrobial resistance and pathogenicity of APEC isolates. The transfer of genetic elements leads an apathogenic strain to present some pathogenic potential and, similarly, isolates that are sensitive to certain antimicrobials can become resistant.…”

Salmonella spp. in poultry: a constant challenge and new insights

“…Different Salmonella serovars tend to take place is genetically similar to the virulence plasmids found in avian pathogenic Escherichia coli (APEC). These APEC-like plasmids were probably exchanged among the two bacteria species in the intestinal environment and they also possess virulence elements that have contributed to their establishment in predominant Salmonella Kentucky strains in chicken intestines and meat (Fricke et al, 2009).…”