Prevalence and antimicrobial susceptibility of Listeria monocytogenes in Koozeh cheeses of Urmia retails

Koozeh cheese is of the local traditional cheeses of Azerbaijan and Kurdistan areas of Iran, and this cheese has high consumption among the people of these regions. Listeria monocytogenes is a food borne pathogen, and because of its growth at refrigeration temperatures has great concern in public health. In the present research, prevalence rate of L. monocytogenes in Koozeh cheeses of Urmia retails was surveyed. Moreover, antimicrobial susceptibility of the isolates was studied. One hundred samples of Koozeh cheese were collected randomly from Urmia retails in the spring of 2013. Samples were cultured in L-PALCAM Listeria selective enrichment broth with supplement. The enriched samples were transferred to PALCAM Listeria selective agar with antibiotics. For the identification of Listeria species, specific biochemical tests were performed. Antibiotic susceptibility of L. monocytogenes isolates was determined by disk diffusion method using penicillin G, chloramphenicol, ceftriaxone, erythromycin, tetracycline, and gentamicin. Among the 100 tested samples, L. monocytogenes was isolated from 3 of the samples. Antibiogram results showed that all L. monocytogenes isolates were susceptible to the tested antibiotics. However, tetracycline, penicillin and erythromycin were shown larger diameter of inhibition zone than the others. Although the prevalence rate of L. monocytogenes in Koozeh cheeses was low, its capability to growth in refrigerator conditions along with the pathogenicity of the bacterium to humans, hygienic production and distribution of these cheeses are recommended