Molecular Characterization of Extended- pectrum β- Lactamase Resistance Genes among Salmonella Isolates from Poultry, Poultry Products and Human Patients in Saudi Arabia

Thirty seven Salmonella isolates from poultry, poultry products and human patients in Saudi Arabia were examined for antimicrobial susceptibility and characterized by pulsed-field gel electrophoresis (PFGE) and plasmid profile. Cephalosporin-resistant isolates were examined for the presence of genes encoding beta_lactamases by PCR and sequencing. Seven different PFGE types were observed. One type was recovered in all sources; two types were found only in human patients, two only in poultry, one only in poultry products, and one both in poultry and poultry products. Seven isolates were susceptible to all antimicrobial agents tested, whereas 29 were resistant to three or more antimicrobials. Most resistance was observed among the isolates from human patients. Of the 17 isolates from human patients, 12 displayed resistance to ampicillin and the cephalosporins ceftiofur and cephalothin. All 12 isolates tested negative for b1aCMY-1, blaCMY-2, and blaACC, but positive for blaSHV, of which five were sequenced to blaSHV-2. Plasmid profiling and hybridization revealed that the b/aSHV gene was located on plasmids of approximately 70 kb. Five plasmid profiles were found among these 12 isolates. The plasmid profiling confirmed the PFGE-type and was able to further subdivide the strains nine of these 12 isolates contained also blaTEM, of which four representatives were sequenced to blaTEM-1H. One isolate contained blaCTX-M-15, blaSHV-2, and blaTEM-1H, with the blaCTX-M-15, and blaTEM-1H genes located on a 64-kb transferable plasmid. This study showed a high frequency of resistance among salamonella. isolated from humans and poultry, with a lower frequency in poultry and poultry products. The clonal relatedness among the isolates from three sources could indicate a recent spread of the isolates.