Occurrence of virulence factors and carbapenemase genes in Salmonella enterica serovar Enteritidis isolated from chicken meat and egg samples in Iraq

Background Food-borne infections mainly due to Salmonella enterica serovar Enteritidis (S. Enteritidis) are major concerns worldwide. S. Enteritidis isolates may serve as reservoirs for spreading antimicrobial drug resistance genes including carbapenemases. This study aimed to screen the occurrence of virulence factors, carbapenemases, and antibiotic resistance genes in S. Enteritidis isolated from chicken meat and eggs in Iraq. Results In total, 1000 non-duplicated chicken meat and 1000 egg samples were collected during 2019-2020. Presumptive S. Enteritidis isolates were initially identified by standard bacteriology tests and then were confirmed using polymerase chain reaction (PCR). Carbapenem resistance was detected using the disk diffusion method. Virulence and carbapenemase genes were screened using the PCR method. In total, 100 (5.0%) S. Enteritidis isolates were identified from 2000 samples collected using phenotypic and molecular methods. These isolates were identified from 4.9% chicken meat (n = 49/1000) and 5.1% egg (n = 51/1000) samples, respectively. The most and the least susceptibility was found to gentamicin and ceftazidime antibiotics, respectively. The prevalence of different virulence factors were as follows: phoP/Q (40.0%), traT (30.0%), stn (22.0%), slyA (11.0%), and sopB (9.0%). Among 20 carbapenem-resistant S. Enteritidis isolates, the most predominant carbapenemase gene was bla(IMP) (35.0%, n = 7), followed by bla(OXA-48-like) (25.0%, n = 5), and bla(NDM) (10.0%, n = 2), while the bla(KPC) and bla(VIM) genes were not detected. The coexistence of bla(IMP), bla(OXA-48-like), and bla(NDM) genes was determined in two isolates. The prevalence of different antibiotic resistance genes were as follows: tetA (87.1%), tetB (87.1%), dfrA1 (77.6%), and sul1 (83.6%). Conclusion Considering the existence of carbapenem-resistant S. Enteritidis harboring different virulence and antibiotic resistance genes in chicken meat and egg samples, adherence to proper hygienic conditions should be considered.

Automated summary

This study investigated the presence of virulence factors, carbapenemases, and antibiotic resistance genes in S. Enteritidis isolated from chicken meat and eggs in Iraq. The results showed varying levels of resistance and virulence factors in the samples collected.