Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

High diversity of TcdA-negative, TcdB-positive and non-toxigenic Clostridium difficile in Thailand (#138)

Korakrit Imwattana 1 , Piyada Wangroongsarb 2 , Thomas V Riley 1 3 4 5
  1. School of Biomedical Sciences, The University of Western Australia, Perth, WA, Australia
  2. The National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Nonthaburi, Thailand
  3. School of Veterinary and Life Sciences, Murdoch University, Perth, WA, Australia
  4. School of Medical and Health Sciences, Edith Cowan University, Perth, WA, Australia
  5. Department of Microbiology, PathWest Laboratory Medicine, Perth, WA, Australia

It has been previously reported that there is a high prevalence of TcdA-negative, TcdB‑positive (A-B+) Clostridium difficile, all of which belong to a single ribotype (RT) 017, as well as non-toxigenic C. difficile in Thailand, many of which are resistant to multiple antimicrobials. However, these findings were limited to a single tertiary hospital in Bangkok. In this study, 145 C. difficile strains isolated from clinical specimens from 13 provinces of Thailand during 2006 – 2018 were ribotyped and toxin profiled. In addition, minimal inhibitory concentrations (MIC) for eight antimicrobials were determined for 100 C. difficile strains isolated during 2006 – 2015. Forty-nine per cent of the strains (71/145) were non‑toxigenic. Among the toxigenic strains, the most common toxin profile was A-B+ (46/145; 32%) and, of A-B+ C. difficile, the most common RT was RT 017 (28/145; 19 %). In contrast to previous studies, 18 A-B+ C. difficile strains (12 %) belonged to 12 new RTs. All C. difficile strains remained susceptible to vancomycin and metronidazole, however, a slight increase in MICs for metronidazole was noticed (MIC50/90: 0.25/0.25 mg/l during 2006 – 2010 compared to MIC50/90: 1.0/2.0 mg/l during 2011 – 2015). Resistance to moxifloxacin occurred in 73 % of RT 017 strains, consistent with previous reports on this RT. Given that the use of fluoroquinolones (FQs) is poorly controlled in Thailand, it is possible that FQ resistance in RT 017 will drive its spread, as it had happened in many countries during recent decades. In contrast, only 22 % of other A-B+ RTs were resistant to moxifloxacin. Non-toxigenic strains in this study had low rates of antimicrobial resistance in contrast to previous reports. This study suggests that there is a great diversity of A-B+ and non-toxigenic C. difficile in Thailand, both of which may have played a role in the pathogenesis of CDI in this country, resulting in the unique clinical characteristics often seen.