Characteristics of drug resistance and molecular typing for Salmonella enteritidis isolated in He′nan Province from 2013 to 2015

Objective To investigate the etiological, antimicrobial resistance status and pulsed field gel electrophoresis (PFGE) patterns of S. enteritidis strains in Henan Province. Methods Totally 82 strains of S. enteritidis strains were isolated from seven sentiel hospitals which were able to detect multiple pathogens from April, 2013 to December, 2015. According to Salmonella K-B drug susceptibility testing and molecular typing method published by the USA clinical and Laboratory Standards Institute (2015), the drug sensitivity to 7 kinds of antimicrobial agents and PFGE molecule characteristics of 82 S. enteritidis strains were tested. The PFGE patterns were analyzed by BioNumerics 6.0 software based on international PulseNet bacterial infectious disease monitoring network. Results Forty-seven strains of S. enteritidis were isolated from male patients, 35 strains isolated from female patients. A total of 56 S. enteritidis strains were isolated from young children aged from 0 to 5 years old, including 29 strains isolated from 6 months to 2 years old. The strains were mainly isolated between May and November of the year, and 15 (18.3%) strains were isolated between March and April, 27(32.9%) strains between May and July, 34 (41.5%) strains between August and October, 6 (7.3%) strains were isolated in the rest time of the year, with a typical seasonal characteristics of summer and autumn. Sxity-four (78.0%) strains of S. enteritidis were resistant to ampicillin; 23 (28.0%) strains were resistant to ceftazidime; 39 (47.6%) strains were resistant to cefotaxime; 13 (15.9%) strains were resistant to cefepime; 55 (67.1%) strains were resistant to nalidixic acid; 24 (29.3%) strains were resistant to ciprofloxacin; 32 (39.0%) strains were resistant to gentamicin; 14 (17.1%) strains were resistant to chloramphenicol; 47 (57.3%) strains were resistant to methicillin benzyl ammonium; 13 (15.9%) strains were resistant to sulfamethoxazole and trimethoprim; 21 (25.6%) strains were resistant to tetracycline. All strains were multi-drug resistant, and 21 (25.6%) isolates were resistant to 3-4 kinds of antibiotics, 32 (39.0%) isolates were resistant to 5—6 kinds of antibiotics, 29 (35.4%) isolates were resistant to 7-8 kinds of antibiotics. These 82 strains of S. enteritidis were divided into 25 molecular patterns by digestion with XbaⅠ enzyme. Each pattern contained 1 to 26 strains with similarity ranged from 59.33%-100.00%. EN1 and EN2 were the main PFGE belt types and included 26 and 16 strains, respectively. Conclusions The drug resistance of clinical isolates of S. enteritidis in Henan province is serious. PFGE patterns show polymorphism and the dominant patterns, part of which are associated with drug-resistance spectrum and show aggregation. Key words: Salmonella enteritidis; Molecular typing; Pulsed field gel electrophorsis