Molecular Detection, Virulence Genes, Biofilm Formation, and Antibiotic Resistance of Salmonella enterica Serotype enteritidis Isolated from Poultry and Clinical Samples

Background: Salmonella spp. is one of the most important zoonotic pathogens transmitting among human and animals. Due to the similarity of antibiotic classes used to treat animals and humans, there is a high risk for emerging the multi-drug resistant (MDR) strains. Objectives: The current study aimed at evaluating molecular detection, virulence genes, biofilm formation, and antibiotic resistance of Salmonella enterica serotype enteritidis recovered from poultry and clinical isolates. Methods: A total of 282 isolates were recovered from chicken meat, live poultry feces, eggs, and human feces in Iran. The presence of virulent factors in the isolates was confirmed using biochemical and microbiological tests. The presence of Salmonella genus was determined using antiserum. Triplex polymerase chain reaction (PCR) was performed to detect Salmonella spp., serogroup D and the discriminate S. enteritidis from other species. Kirby-Bauer disk diffusion method was applied to perform the susceptibility testing. Quantification of biofilm formation was determined in 96-well microtiter plates as recommended by the defined protocol. The data were then analyzed with SPSS using consensus tables and Chi-square test. Results: Based on the results, all the isolates were positive for invA, sdiA, hilA, and ratA. Moreover, spvC had the lowest prevalence (37.6%). Of all strains, 67% were MDR, 51.7% of which were recovered from humans. Furthermore, 34.5% of isolates were strong biofilm producers. There was a significant correlation between the strong biofilm formation and the antibiotic resistance to colistin, ceftazidime, chloramphenicol, gentamicin, trimethoprim, penicillin, and trimethoprim-sulfamethoxazole. Conclusions: The results of the current study showed a significant correlation between the strong biofilm formation and the antibiotic resistance to some antibiotics.