Molecular characterization of Salmonella enterica serovar Enteritidis on retail raw poultry in six provinces and two National cities in China

Abstract One hundred and twenty six Salmonella Enteritidis isolates recovered from 1152 retail raw poultries were characterized by antimicrobial susceptibility test, pulsed-field gel electrophoresis (PFGE), presence of quinolone resistance (Qnr) associated genes, Class I integron, extended spectrum beta-lactmases (ESBLs) encoding genes, and mutations in quinolone resistance-determining region (QRDR) of Gyr A and Par C. Resistance was most frequently found to nalidixic acid (88.1%), followed by to tetracycline (65.9%), sulfisoxazole (65.1%), and ampicillin (61.9%), and a less extent to cefoxitin (8.7%), gatifloxacin (8.7%), levofloxacin (7.9%), ceftriaxone (7.1%), and ceftiofur (6.3%). One hundred and twenty three (98.4%) isolates were resistant to at least one antibiotic, and 93 (74.4%) to at least four antibiotics. aac(6 ′ )-Ib-cr , qnr B, qnr A and qnr S genes were detected in 15 (11.9%), 11 (8.7%), 6 (4.8%) and 1 (0.8%) isolates, respectively. Amino acid substitutions of Ser83Tyr, Asp87Asn, Asp87Tyr, Asp87Gly and Ser83Phe/Asp87Asn were detected in QRDR of Gyr A, Arg80Ser was the unique mutation in Par C. Eight isolates were detected with amino acid substitution both in Gyr A and Par C. Three isolates carried Class I integron that harboring dfr A17- aad A5, dhf R1- aad A1, and dfr A1, respectively. Five isolates were detected carrying bla TEM – bla ACC ( n  = 1), bla TEM ( n  = 1), bla TEM – bla OxA ( n  = 3), respectively. Genetic diversities ( D  = 0.9255) were found among isolates based on PFGE analysis.