Molecular Typing And Antimicrobial Susceptibility Of Clostridium Difficile Isolated From Food Animals In China

More and more reports of genetic overlap between animal and human sources of Clostridium difficile(C.difficile)and C.difficile as an important pathogen of zoonotic disease appeals to be highly critical for human hea lth oblige an understanding of molecular characterization and antimicrobial resistance in these populations.In this study,we aimed to investigate the molecular characterization and antimicrobial susceptibility of C.difficile isolated from food animals in China.The samples comprised of 538 fecal swabs were collected from food animals(pig,n=398;chicken,n=121;duck,n=19)with diarrhea on different farms during year 2016.The isolation of C.difficile was performed by using the spore enrichment methods followed by DNA extraction.Identification of tcdA,tcdB,cdt A and cdt B genes was performed by PCR method.All isolates were typed by MLST and Ribotyping.Antimicrobial susceptibility of17 antimicrobials was determined by agar incorporation methodology according to CLSI.A total of 44 samples(8.2%)were positive in bacteriological assay and comprised of 4 toxin gene profiles,7 different sequence types(STs;3,11,35,48,109,238,240)and 6 ribotypes based on molecular assay.Among the 44 C.difficile,88.6%of the isolates(39/44)were toxigenic and the remaining 5 were non-toxigenic.Out of the 39 toxigenic strains,27 were positive for tcdA and positive for tcdB(A~+B~+),14 of which were also positive for cdt A/B(A~+B~+C DT~+),and the remaing 12 toxigenic strains were negative for tcdA and positive for tcdB(A~-B~+).Sequence types(ST)11 was the most popular and predominantly accounted for 14 of the 44C.difficile,followed by ST109 accounted for 9 of 44 C.difficile.ST11 isolates produce ctdA/B and tcdA and tcdB(A~+B~+CDT~+),however ST 109 producing tcd B(A~-B~+CDT~-)and widely distributed among Shandong,Guangzhou and Henan Province.6 ribotypes were identified among 44 isolates,including GZ1,GZ2,GZ3,GZ4,GZ5 and GZ6.Based on the molecular characteristics of RT078/ST11 epidemic clone,GZ2 was confirmed as RT078.All isolates were fully susceptible,to vancomycin,metronidazole,fidaxomicin,amoxicillin/clavulanate,and meropenem,the remainder multiplex resistant to 3 or 4antibiotics.The predominate RT078/ST11 concurrent ly resistant to tetracycline,cefoxitin,ciprofloxacin and imipenem.The present study for the first reported the molecular epidemiology of C.difficile isolated from food animals in C hina,and identified RT078(GZ2)/ST11 cases as a predominate clone among food animals in China.This study provides an important baseline for ongoing long-term surveillance of antimicrobial resistance and prospective tracking of prominent and emerging strain types.