Molecular Characterization and Occurrence of Extended-Spectrum β-Lactamase Resistance Genes among Salmonella enterica Serovar Corvallis from Thailand, Bulgaria, and Denmark

Abstract

Fifty nine Salmonella Corvallis isolates from humans and food products in Bulgaria, Denmark, and Thailand were examined for antimicrobial susceptibility and characterized by pulsed-field gel electrophoresis (PFGE). Cephalosporin-resistant isolates were examined for the presence of genes encoding beta-lactamases by PCR and sequencing. Ten different PFGE types were observed. One type (30 isolates) was recovered in all three countries; three types were found only in Bulgaria, two only in Denmark, two only in Thailand, and two both in Denmark and Thailand. Ten isolates were susceptible to all antimicrobial agents tested, whereas 41 were resistant to three or more antimicrobials. Most resistance was observed among the isolates from Bulgaria. Of the 25 isolates from Bulgaria, 20 displayed resistance to ampicillin and the cephalosporins ceftiofur and cephalothin. All 20 isolates tested negative for bla (CMY-1), bla (CMY-2), and bla (ACC), but positive for bla (SHV), of which five were sequenced to bla (SHV-2). Plasmid profiling and hybridization revealed that the bla (SHV) gene was located on plasmids of approximately 70 kb. Five plasmid profiles were found among these 20 isolates. The plasmid profiling confirmed the PFGE-type and was able to further subdivide the strains. Seventeen of these 20 isolates contained also bla (TEM), of which nine representatives were sequenced to bla (TEM-1B), or bla (TEM-1H). One isolate contained bla (CTX-M-15), bla (SHV-2), and bla (TEM-1H), with the bla (CTX-M-15), and bla (TEM-1H) genes located on a 63-kb transferable plasmid. This study showed a high frequency of resistance among S. Corvallis isolated from humans and food products in Bulgaria, with a lower frequency in Thailand and Denmark. The clonal relatedness among the isolates from three countries could indicate a recent spread of this serovar.

Clonal relatedness and resistance patterns of Salmonella Corvallis from poultry carcasses in a Brazilian slaughterhouse

“…S. Corvallis was originally described in 1949 [22] after being isolated from poultry, and its importance has been increasing in recent years due to its potential for causing local or global outbreaks [6,7,23,24]. Detection of ESBLproducing Salmonella strains has emerged over the years [13,14].…”

“…Detection of ESBLproducing Salmonella strains has emerged over the years [13,14]. One of the largest studies on S. Corvallis strains showed that different types of ESBL were occasionally simultaneously present in strains recovered from human sources and food products in Bulgaria, Thailand, and Denmark [6]. The emergence of ESBL in Salmonella isolated from animal production may be, at least in part, attributed to the selective pressure in this reservoir when antimicrobial agents are widely applied to promote growth [13,15,25].…”

“…Corvallis is considered to be rare in most countries; however, in recent years, a higher incidence has been reported in specific geographic areas such as Bulgaria, Denmark, Tunisia and Japan [6][7][8]. This serovar has been isolated from poultry, food products of animal origin, human infections, and even in outbreaks of foodborne diseases [6][7][8].…”

“…This serovar has been isolated from poultry, food products of animal origin, human infections, and even in outbreaks of foodborne diseases [6][7][8].…”

Livestock Production and Foodborne Diseases from Food Animals in Thailand

“…Tetracycline resistance is mediated by a mobile resistance gene usually clustered together in an integron capable of horizontal transfer [3,19]. Detection of the integrase gene in the bacteria indicates the presence of an integron element which may carry an antimicrobial resistance gene.…”