Characterization of Clostridium difficile from human and swine in Taiwan

  • 蔡 博仰

Student thesis: Master's Thesis


Clostridium difficile is the major cause of nosocomial diarrhea Epidemiological study on C difficile in Taiwan is limited A total of 251 C difficile isolates from patients were collected between January 2011 and December 2012 in southern Taiwan I analyzed the distribution of toxin A (tcdA) toxin B (tcdB) and binary toxin genes (both cdtA and cdtB) and tcdC truncated mutations in all isolates by a newly established multiplex-PCR with additional truncated-tcdA PCR screening A total of 45 8% (115/251) isolates harbored tcdA and tcdB (A+B+) and 32 7% (54/251) isolates did not have tcdA and tcdB (A-B-) Notably 21 5% (54/251) of isolates were tcdA-nagative and tcdB-positive (A-B+) Among these A+B+ strains eighteen isolates (7 2%) were also positive for cdtA/B which carry a tcdC gene deletion including an 18-bp (22%) or 39-bp deletion (78%) These eighteen hypertoxigenic (A+B+CDT+) strains were further typed by PCR-ribotyping There was no ribotype 027 in this study and the predominant PCR-ribotypes were defined as RT078-family (77 8% 14/18) including RT078 (5 5%) RT127 (33 3%) RT126 (22 2%) and unknown RT-type (16 7%) with a RT078 marker which were confirmed by the C difficile Ribotyping Network (CDRN) in England Retrospective review of clinical data demonstrated 7 hypertoxigenic strains caused C difficile associated diarrhea (CDAD) in patients and 5 of 7 belonged to RT078-family Notably one patient infected by RT126 even developed the severe pseudomembranous colitis (PMC) In addition RT078-family is more cytotoxic than other ribotypes Previous studies demonstrated that C difficile RT078-family is predominant in animals worldwide particularly in swine Therefore I surveyed C difficile strains isolated from swine in sixteen farms during August 2011 and March 2015 in Taiwan I found the positive culture rate is 85 1% (114/134) and all strains from swine belonged to RT078-family including RT078 (32 5%) RT126 (28 9%) RT127 (37 7%) and one unknown-RT (0 9%) with RT078 marker Among RT078 isolates I found three swine isolates might that be identical to the strains isolated from patient by Rep-PCR and tcdB sequencing suggesting these is potential zoonosis between human and swine in Taiwan Meanwhile we observed that RT078 and RT126 strains presented distinctive colony morphology on agar plate and aggregation phenotype in broth culture which were not associated with rapid growth or biofilm formation In conclusion these results highlighted that toxigenic RT078 family strains in Taiwan is predominant and more attention should be given in order to minimize risk of further spreading
Date of Award2015 Aug 11
Original languageEnglish
SupervisorPei-Jane Tsai (Supervisor)

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