Clostridium difficile is an important nosocomial pathogen, and the most commonly recognised cause of antibiotic-associated diarrhoea in the human population. Development of disease is linked to disruption of the host microbiota, which often occurs after antibiotic therapy. Antibiotic resistance is commonly identified in C. difficile and may contribute to its ability to cause disease and to spread in a particular environment.
The aim of this study was to characterise the types of C. difficile circulating locally. Isolates from two hospitals in Melbourne were collected from 2006 - 2009. Historic (pre-1990) Victorian isolates were also examined. PCR for genes encoding virulence determinants toxin A and toxin B, as well as binary toxin, was performed. Isolates were toxinotyped, as this method provides information about variation in the genes encoding major toxins, and also ribotyped. A selection of isolates was assayed for antibiotic susceptibility profiles and resistance determinants identified where possible.
The types of C. difficile strains identified in the Victorian healthcare setting during the study period were diverse. Toxinotyping revealed that most of the isolates were toxinotype 0 (75.6%), with seven variant toxinotypes (16.3% of isolates) also present. Variant toxinotypes identified in this study included toxinotype V and toxinotype VIII, both of which have been linked to outbreaks and severe disease overseas. This study also showed that Victorian isolates of C. difficile may be resistant to many antimicrobial agents. All isolates tested were resistant to at least two agents, and the majority were resistant to three or more. All isolates were resistant to bacitracin, and many resistant to fusidic acid (83%). A large proportion of strains was clindamycin resistant (96%), while 22% were also resistant to erythromycin. Tetracycline resistance was seen in 13% of isolates tested. Two isolates (9%) were resistant to moxifloxacin. All isolates were susceptible to metronidazole and vancomycin.