Prevalence of listeria monocytogenes in poultry marketed in Iran: Characterization and antimicrobial resistance of the isolates

The aim of the present study was to evaluate the prevalence of Listeria monocytogenes (L.m) in poultry marketed in Varamin, Tehran province, Iran. A total of 584 samples, including intestinal contents of chicken (n = 370) and turkey (n = 214) were randomly collected from different wet markets, between November 2008 to July 2010. USDA method was used for isolation of Listeria spp and L. m. The L. m. isolates were confirmed by API Listeria and PCR and were seroptyped using antisera against O and H antigens. The Kirby-Bauer disc diffusion method was used to assess the antimicrobial susceptibility to 10 antibiotics (Tetracycline, Gentamycin, Chloramphenicol, Vancomycin, Rifampin, Pen G, Kanamycin, Erythromycin, Clindamycin and Amoxicillinclavulanic acid) according to CLSI. Furthermore, the virulence profile of L.m isolates (inlA, inlB, inlC, inlJ, actA, hlyA, iap, plcA, prfA) and the presence of antimicrobial resistance genes (tetA, tetB, vanA, vanB, ermB, cmlA, penA) was investigated by PCR. The contamination rate with Listeria spp in poultry was 16%. The most frequent isolated species was L. ivanovii (9%). L.m was detected in 3% of poultry samples and serovar 1/2a (61%) was the predominant among L.m isolates. All virulence-associated genes were detected in 85% of the isolates. The 33% of L.m isolates were sensitive to all tested antibiotics: the remaining L.m isolates were resistant to 1 to ≥ 3 antibiotics. The presence of antimicrobial resistance genes was not completely correlated with antimicrobial resistance to Tetracycline and Pen The main results of the present study confirmed the high prevalence of Listeria spp. and the high rate of antimicrobial resistance of L.m isolates from poultry products marketed in Iran.