Surveillance for antimicrobial resistance in Australian isolates ofClostridium difficile, 2013–14

Abstract

These data confirm the potent in vitro activity of fidaxomicin against C. difficile. Moreover, this study provides an important baseline for ongoing long-term surveillance of antimicrobial resistance and prospective tracking of prominent and emerging strain types.

Genome Analysis of Clostridium difficile PCR Ribotype 014 Lineage in Australian Pigs and Humans Reveals a Diverse Genetic Repertoire and Signatures of Long-Range Interspecies Transmission

“…C. difficile culture was performed as previously described (Knight et al, 2015b). After subculture on blood agar for 24 h, 1–3 colonies of each isolate were inoculated into pre-reduced brain-heart infusion broth containing 0.1% L-Cysteine and incubated anaerobically at 37°C overnight (~16 h).…”

“…Minimum inhibitory concentrations (MIC) were determined for a panel of 16 antimicrobial agents against all RT014 isolates ( n = 40) using CLSI agar dilution methodology as previously described (Knight et al, 2015b). The panel included vancomycin, metronidazole, fidaxomicin, rifaximin, clindamycin, erythromycin, amoxicillin-clavulanate, piperacillin-tazobactam, ceftriaxone, meropenem, moxifloxacin, tetracycline, trimethoprim, gentamicin, tobramycin, and spectinomycin.…”

“…The panel included vancomycin, metronidazole, fidaxomicin, rifaximin, clindamycin, erythromycin, amoxicillin-clavulanate, piperacillin-tazobactam, ceftriaxone, meropenem, moxifloxacin, tetracycline, trimethoprim, gentamicin, tobramycin, and spectinomycin. Where available, clinical breakpoints for antimicrobial agents are those based on recommendations of CLSI and EUCAST as previously detailed (Knight et al, 2015b). For fidaxomicin, a European Medical Agency proposed susceptible breakpoint of 1 mg/L was used (report WC500119707, http://www.ema.europa.eu/).…”

“…RT014 [toxinotype 0, North American Pulsotype (NAP) 4] is a highly successful clade 1 lineage of C. difficile consistently among the most common RTs causing CDI in Europe (Bauer et al, 2011; Freeman et al, 2014) and is predominant in some pediatric populations (Schwartz et al, 2014). RT014 is also currently the most prevalent RT in Australia, accounting for ~25% of CDI cases (Foster et al, 2014; Knight et al, 2015b; Collins et al, in press). In 2013, we conducted a prevalence study of C. difficile in 21 piggeries across five states in Australia and found RT014 to be the most prevalent RT in neonatal pigs, accounting for 23% ( n = 26/154) of isolates (Knight et al, 2014).…”

Infection with Toxin A-Negative, Toxin B-Negative, Binary Toxin-Positive Clostridium difficile in a Young Patient with Ulcerative Colitis

“…C. difficile RT033 was previously detected in the patient's stool sample; thus, it was possible that this ribotype was responsible for the CDT-positive result obtained. Susceptibility testing using an agar dilution method and CLSI/EUCAST in-terpretive criteria (2) showed that both RTs were susceptible to clindamycin, moxifloxacin, metronidazole, and vancomycin. The MICs of fidaxomicin and rifaximin were 0.06 mg/liter and 0.004 mg/liter, respectively.…”