Molecular Detection of some Antimicrobial Resistance Genes in Salmonella Species Isolated from Commercial Layers in Egypt

The present study was done to investigate the wide spread resistance to some antimicrobial groups among Salmonellae isolated from replacement and layer flocks in Egypt. A total of 24 salmonellae were isolated from 200 birds (apparently healthy or diseased suffered from diarrhea, dehydration, respiratory distress and decrease of egg production) and serotyped into S. Enteritidis, S. Typhimurium, S. Kentucky and S. Newport. Twenty-one Salmonella isolates were examined for resistance genes against different antimicrobials. The resistance pattern of all Salmonella isolates was done using antibiogram, the resistant isolates were examined for the presence of resistance coding genes using PCR technique. The investigated resistance genes were (qnrS, aac (6')-ib-cr) for quinolone resistant isolates, blaTEM for β-lactam resistant isolates, aadA1 and aadA2 for aminoglycosides resistant isolates and tetA(A) and tetA(B) for tetracycline resistant isolates. Resistant genes percentages for tetA(A), tetA(B), blaTEM, aadA1, aadA2, aac (6')-ib-cr and qnrS in the examined isolates were 70%, 20%, 93.3%, 30%, 80%, 10% and 15%, respectively. In conclusion, at the study area, antimicrobial resistance genes are widely spread in Salmonella isolates. Thus, minimizing the influence of antibiotics in treatment and prevention