Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2016

Toxin A-negative toxin B-positive ribotype 017 Clostridium difficile is the dominant strain type in patients attending tuberculosis hospitals in Cape Town, South Africa (#253)

Brian Kullin 1 , Lourens Robberts 2 , Justyna Wojno 3 , Valerie Abratt 1 , Sharon Reid 1
  1. Molecular and Cell Biology, University of Cape Town, Cape Town, Western Cape, South Africa
  2. National Health Laboratory Service, Groote Schuur Hospital, Cape Town, Western Cape, South Africa
  3. Department of Medical Microbiology, University of Cape Town, Cape Town, Western Cape, South Africa

Clostridium difficile infection (CDI) is understudied in South Africa and there is little published information regarding the predominant ribotypes present in CDI patients and the antibiotic susceptibility profiles of local strains.  Samples submitted by various Cape peninsula hospitals during September 2014-September 2015 that tested positive using the GeneXpert diagnostic test were retained and subjected to selective culture.  Putative C. difficile isolates were confirmed by PCR targeting the tpi gene as well as the toxin encoding genes (tcdA, tcdB, cdtA, cdtB).  Isolates were characterised further by ribotyping (RT) and multilocus variable-number tandem-repeat analysis (MLVA) as well as antibiotic susceptibility testing.  A total of 269 C. difficile isolates were obtained, of which 97% harboured at least one of the toxin genes.  Toxin A-B+ strains accounted for 64.68% of the total isolates, while toxin A+B+ strains accounted for a further 31.60%.  Only two isolates harboured the binary toxin genes.  Ribotyping revealed that all toxin A-B+ strains belonged to the RT017 group.  RT017 strains also made up 90% and 100%, respectively, of isolates received from two dedicated tuberculosis (TB) hospitals.  The predominant RTs amongst toxin A+B+ strains were RT001, RT014, RT015 and RT(SE108).  All tested isolates were sensitive to vancomycin and metronidazole, although a small proportion of RT017 strains showed decreased susceptibility to metronidazole (4-6 mg L-1 MIC).  Moxifloxacin resistance was predominantly seen in RT017 and RT012 strains (97.64% and 50% resistant, respectively), while erythromycin resistance was mainly observed in RT017 and RT(SE108) strains (78.69% and 85.71% respectively).  Rifampicin resistance was seen almost exclusively in ribotype 017 strains (97.50% of strains resistant).  MLVA of RT017 strains suggested diverse sources of infection as well as patient-to-patient transfer events.  The results of this study suggest that multidrug resistant RT017 C. difficile strains are prevalent amongst tuberculosis patients in the Cape peninsula area.