Increased antimicrobial resistance in clonal clostridium difficile isolates in Dublin Ireland

Clostridium difficile is a major cause of infectious diarrhoea in hospitalised patients. While antibiotics are a major risk factor predisposing to C. difficile diarrhoea, few studies have examined antimicrobial resistance in C. difficile isolates. We described previously an outbreak of C. difficile diarrhoea in Dublin, Ireland. The aim of this study was to determine antimicrobial susceptibilities of the C. difficile isolates collected during the outbreak period. C. difficile isolates were cultured on CCFA agar. PCR ribotyping was used to determine genomic relatedness between C. difficile isolates. Antimicrobial susceptibilities to macrolide and fluoroquinolone antibiotics were determined using E-tests. 90 isolates were collected during the outbreak period. PCR ribotyping profiles divided the isolates into two clusters, a major outbreak cluster of 85 isolates and a second cluster of 5 strains. The clonal outbreak isolates (n=85) were resistant to all fluoroquinolones (Ofloxacin, Ciprofloxacin, Levofloxacin, Moxifloxacin and Gatifloxacin) and MLS (Erythromycin, Clarithromycin, Clindamycin) antibiotics tested. In contrast non-clonal isolates were sensitive to MLS antibiotics and Levofloxacin, Moxifloxacin and Gatifloxacin. Acquired antimicrobial resistance may be an additional virulence factor in C. difficile isolates by allowing persistence of clonal strain types in the hospital environment.