Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2009
Publication Date: 9/1/2009
Citation: Zou, W., Frye, J.G., Chang, C., Liu, J., Cerniglia, C.E., Nayak, R. 2009. Microarray Analysis of Antimicrobial Resistance Genes in Salmonella enterica from Preharvest Poultry Environment. Journal of Applied Microbiology. 107(3):906-914.
Interpretive Summary: Salmonella harbored by food animals has the potential to impact human health particularly if food stuffs are consumed raw, are mishandled or are undercooked. Although salmonellosis is typically self-limiting, when treatment is required, the occurrence of resistance among Salmonella isolates can present extra concerns. To investigate the presence of antimicrobial resistance genes, a DNA microarray chip designed to detect 775 antimicrobial resistance genes was used to analyze 34 Salmonella from a turkey production facility. Phenotypic resistance of the isolates using conventional broth microdilution techniques was also determined. When microarray data was positive for several genes, results were confirmed by PCR. Resistance genes were identified from the DNA microarray which correlated with phenotypic testing, including: tet(A), and/or tet(R) (specific for tetracycline-resistance), sul1 and sul2 (specific for sulfa resistance). Resistance genes aadA, aadB, strA and strB detected only in Salmonella serotypes Heidelberg, Senftenberg and rough S. Senftenberg, also had several mobile genetic elements which may contribute to the transfer of resistance genes. Identification of the causes of antimicrobial resistance in animal production environments is a step towards developing strategies to prevent the spread of antimicrobial resistance.
Technical Abstract: Rapid detection of drug resistance profiles in Salmonella can be critical in treatment of salmonellosis. A 70-mer oligonucleotide microarray chip with 775 gene probes was used to detect antimicrobial resistance genes in 34 Salmonella isolates from a turkey production facility. The phenotypic antimicrobial susceptibility profiles were tested with the NARMS-CLSI Sensititre method using CMVAGNF1 antimicrobial testing plates. The microarray data was validated by PCR analysis of ten antimicrobial resistance genes. Overall, ~62% of the gene probes shared a common homology (presence or absence) in all Salmonella isolates; the remaining 297 probes elicited diverse drug resistance gene profiles. All tetracycline-resistant isolates harbored the tet(A), tet(R) or both genes. The sul1 gene was detected in all sulfisoxazole-resistant isolates, while the sul2 gene was only detected in sulfisoxazole-resistant S. rough isolates. The aadA, aadB, strA and strB genes, associated with aminoglycoside resistance, were found to prevail in S. Heidelberg, S. Senftenberg and S. rough phenotypes, resistant to ampicillin and ceftiofur. Resistant genes remained undetected in susceptible Salmonella isolates. The prevalence of mobile genetic elements, such as class I integron and transposon genes, in drug-resistant S. Heidelberg suggests that these isolates may contribute to the dissemination of antimicrobial resistance genes in preharvest poultry environment. There was 94% agreement between the microarray hybridization and PCR data for detection of antimicrobial resistance genes. Hierarchical clustering analysis was conducted to examine relationships between Salmonella phenotypes and the antimicrobial resistance gene profiles.