Purpose: The aim of this study was to detect the occurrence of stx1 and stx2 genes in E. coli isolated from Minas frescal cheese processing plants located in São Paulo State, Brazil, and to verify the phenotypic antibiotic resistance profiles.
Methods: Twelve samples were collected in six processing cheese plants. During each visit raw milk, pasteurized milk, cheese, environment, equipments, utensils, and surface samples were collected. MacConkey agar and eosin methylene blue (EMB) agar were used for bacterial isolation. The confirmation of species was performed using biochemical tests. Detection of stx1 and stx2 was carried out by polymerase chain reaction (PCR). Antibiotic susceptibility testing was performed by disk-diffusion method using ciprofloxacin, cefoxitin, ceftazidime, chloramphenicol, cefotaxime, trimetopim, tetracycline, streptomycin, nalidixic acid, imipenem, tobramycin, gentamicin, amoxicillin-clavulanic acid, fosfomycin, kanamycin, trimethoprim sulfamethoxazole, rifampicin, aztreonam, and cefepime disks.
Results: Strains were isolated from raw milk, pasteurized milk, cheese, table, floor, coagulation tank, and drain samples. Fourteen E. coli strains carrying the stx1 gene and ten carrying the stx2 gene were identified. The presence of E. coli carrying the stx1 gene in pasteurized milk was of note. Regarding stx1 and stx2 gene positive strains: one was resistant to rifampicin and the other strains were sensitive to the antibiotics tested.
Significance: The results showed that the production of Minas frescal cheese needs to be studied more in regard to food safety because the consumption of this dairy product represents a possible risk to consumers. Furthermore, the producers need to improve the hygiene conditions along the processing chain.