Occurrence and Antibiotic Resistance of Listeria monocytogenes in Retail Minced Beef Distributed in Ahvaz, South-West of Iran

Background: Listeria monocytogenes is one of the most important food-borne bacteria causing septicemia, meningitis and encephalitis in humans. The objective of this study was to evaluate the occurrence and antibiotic resistance of the bacterium in retail minced beef in Ahvaz, South-West of Iran. Methods: In this survey, 150 samples of minced beef were randomly obtained from retail butcheries in Ahvaz, Iran and tested for presence of L. monocytogenes. The procedure was one-step enrichment in Listeria enrichment broth followed by plating on oxford agar. Isolated colonies were subjected to subsequent biochemical tests and polymerase chain reaction (PCR) assay using the target iap-P60 gene encoding P60 protein. Susceptibility of the isolates to various antibiotics was investigated by Kirby-Bauer disk diffusion method. The results were analyzed by chi-square test and fisher’s exact test using SPSS 16.0 software. Results: The incidence of Listeria spp. was 2.7% (4 of 150 samples) and only one sample (0.66%) was contaminated to L. monocytogenes. Statistical analysis showed no significant difference in prevalence of Listeria between various regions (p>0.05). The isolate was resistant to streptomycin and showed an intermediate susceptibility to tetracycline and penicillin. However, it was sensitive to other tested antibiotics. Conclusion: Our findings showed the presence of antibiotic resistant L. monocytogenes strain among beef samples in this region of Iran and so, indicated the potential risk for public health from consumption of raw or undercooked beef which may increase the possibility of acquisition of resistance to antibiotics.