Molecular detection, typing, and virulence potential of Salmonella Serotypes isolated from poultry feeds

Salmonella contamination in poultry feed is one of the main issues in poultry industry and public health. The aim of the present study was molecular detection and typing of Salmonella serotypes isolated from poultry feeds. Moreover, we determined the antibiotic resistance pattern and the ability of biofilm formation in the serotypes. To this end, eighty feed samples were collected from aviculture depots. Salmonella serotypes were identified by culture and PCR methods. For serological identification, a slide agglutination test was used. BOXAIR and rep-PCR methods were applied to evaluate the diversity of serotypes. The disc diffusion method was performed to evaluate the antibiotic susceptibility of serotypes to sixteen antibiotics. Biofilm formation was also assessed by the microtiter-plate test. From a total of 80 feed samples, 30 samples were contaminated with Salmonella spp., which were divided into 5 different serotypes belonging to B, C, and D serogroups. BOXAIR-PCR (D value [DI] 0.985) and rep-PCR (DI 0.991) fingerprinting of isolates revealed 23 and 19 reproducible fingerprint patterns, respectively. A higher antibiotic resistance was observed to ampicillin and doxycycline (100% each), followed by chloramphenicol (83.33%) and tetracycline (73.33%). Multidrug resistance (MDR) was detected in all Salmonella serotypes. Half of the serotypes possessed the ability of biofilm formation with varied adhesion strengths. These results revealed the high and unexpected prevalence of Salmonella serotypes in poultry feed with MDR and biofilm formation ability. BOXAIR and rep-PCR revealed a high diversity of Salmonella serotypes in feeds and subsequently indicated variation in the source of Salmonella spp. The unknown sources harboring high diversity of Salmonella serotypes indicated poor control, which could cause problems for feed manufacturing.