Isolation and identification of antibiotic-resistant Salmonella spp. from local Koozeh and Poosti cheeses

Nowadays, the occurrence of antibiotic-resistant bacterial strains in food is increasing, which makes antibiotic treatment of infected food more difficult. One of the food sources that can cause foodborne infection is dairy products made from raw milk and one of the bacteria resistant to various antibiotics is Salmonella. The aim of this study was to investigate the presence of antibiotic-resistant Salmonella species in Poosti and Koozeh cheeses produced from raw milk in western Iran. For this purpose, the probable Salmonella species were isolated in Koozeh cheese from Bukan and Poosti cheese from Lorestan and Kermanshah. After initial phenotypic identification and biochemical testing, molecular identification was performed by amplification of the 16S rRNA gene with primers U1492R and B27F. The isolates were tested for resistance to tetracycline, oxacillin, penicillin and ampicillin. The results confirmed the presence of Salmonella enterica subspecies Typhimurium in all three cheeses among 14 Enterococcus isolates. The species of all three cheese were resistant to oxacillin, penicillin and ampicillin and the identified species of Lorestan Poosti cheese were resistant to tetracycline. But the identified species in Kermanshah Poosti cheese and Bukan Koozeh cheese were sensitive to tetracycline. The results of this study indicate that local Poosti and Koozeh cheeses in some western parts of the country may be carriers of antibiotic-resistant Salmonella strains and that in case of microbial infection caused by contaminated cheese, treatment with antibiotics may be difficult.