Microarray analysis of antimicrobial resistance genes in Salmonella enterica from preharvest poultry environment

Aims:  To detect antimicrobial resistance genes in Salmonella isolates from turkey flocks using the microarray technology. Methods and Results:  A 775 gene probe oligonucleotide microarray was used to detect antimicrobial resistance genes in 34 isolates. All tetracycline-resistant Salmonella harboured tet(A), tet(C) or tet(R), with the exception of one Salmonella serotype Heidelberg isolate. The sul1 gene was detected in 11 of 16 sulfisoxazole-resistant isolates. The aadA, aadA1, aadA2, strA or strB genes were found in aminoglycoside-resistant isolates of Salm. Heidelberg, Salmonella serotype Senftenberg and untypeable Salmonella. The prevalence of mobile genetic elements, such as class I integron and transposon genes, in drug-resistant Salmonella isolates suggested that these elements may contribute to the dissemination of antimicrobial resistance genes in the preharvest poultry environment. Hierarchical clustering analysis demonstrated a close relationship between drug-resistant phenotypes and the corresponding antimicrobial resistance gene profiles. Conclusions: Salmonella serotypes isolated from the poultry environment carry multiple genes that can render them resistant to several antimicrobials used in poultry and humans. Significance and Impact of the Study:  Multiple antimicrobial resistance genes in environmental Salmonella isolates could be identified efficiently by microarray analysis. Hierarchical clustering analysis of the data was also found to be a useful tool for analysing emerging patterns of drug resistance.