Drug resistance detection and pulsed-field gel electrophoresis typing of Shigella sonnei isolated in case-based surveillance in Sichuan, 2007–2017

ObjectiveTo understand the drug resistance and pulsed-field gel electrophoresis (PFGE) patterns of Shigella sonnei strains isolated from sporadic diarrhea cases in surveillance in Sichuan province during 2007–2017.

MethodsA total of 30 S. sonnei strains isolated from diarrhea patients were analyzed by PFGE and tested for minimal inhibitory concentration of 14 antibiotics after the serological and biochemical identification.

ResultsThe antibiotic resistance test indicated all the isolates were only sensitive to cefoxitin, while 96.67% of the strains were multi-drug resistant. The resistance rates to azithromycin and ciprofloxacin were more than 10%. The resistance to 7 common antibiotics, including cefotaxime, reached more than 50%. PFGE typing showed that strains had 16 patterns and two predominant clusters which accounted for 80%, and other types accounted for 20%. A suspected outbreak caused by SCSN-1 and SCSN-3 from cluster I was detected respectively.

ConclusionS. sonnei isolated in Sichuan from 2007 to 2017 had two predominant PFGE clusters and partial subtype showed clustering. The strains had high drug resistance, some of which showed resistance to common antibiotics used in the treatment of bacterial diarrhea, such as ciprofloxacin, azithromycin and cefotaxime.