Antimicrobial resistance and virulence of Salmonella spp. from foods in Mazandaran

SSalmonella is the most important source of food-borne infections around the world. Human salmonellosis is also caused by the consumption of fresh fruit and vegetable salads contaminated with Salmonella spp. We aimed to detect Salmonella spp. in hamburgers, vegetable salads, and cream-filled pastries from various sources in Mazandaran and assess their pathogenicity and antimicrobial resistance.

A total of 90 samples, i.e., hamburgers, vegetable salads, and cream-filled pastries (30 samples of each), were randomly collected. Biochemical and serological tests were performed to detect the Salmonella spp. Antimicrobial susceptibility tests were performed by the disc diffusion method and the virulent genes were examined using polymerase chain reaction (PCR). All the examined Salmonella serovars in this study showed positive amplification for the virulence genes invA, spv, and viaB.

Salmonella spp. were detected in 54 of the 90 samples based on biochemical tests. Of these, 46 isolates (85.2%) were recovered by the 16S-23S rRNA PCR test, of which 19 (41.4%) represented the S. typhimurium serotype, 15 (32.7%) represented the S. enteritidis serotype, and 2 (4.4%) represented the S. typhi serotype. These Salmonella serotypes (19 S. typhimurium, 15 S. enteritidis, and 2 S. typhi; 36 in total) were sensitive to all the tested antibiotics: Ampicillin, 22/36 (61.11%); Streptomycin 22/36 (61.11%); Cefotaxime 23/36 (63.88); Gentamycin 36/36 (100%), and Tetracycline 36/36 (100%). However, a few of these serotypes exhibited slight resistance to ampicillin (4/36; 11.11%) and cefotaxime 2/36 (5.55%).

These results would greatly help in understanding the prevalence of virulence genes and antibiotic sensitivity among Salmonella serovars in hamburgers, vegetable salads, and cream-filled pastries.