Exposure to antimicrobials is the major risk factor associated with Clostridium difficile infection (CDI). Paradoxically, treatment of CDI with antimicrobials remains the preferred option. To date, only two studies have investigated the antimicrobial susceptibility of Thai isolates of C. difficile, both of which were published in 1990s. To gather more contemporary data, a collection of 105 recent C. difficile isolates from inpatients admitted at Siriraj Hospital in Bangkok in 2015 was tested for their susceptibility to 10 antimicrobials using an agar incorporation method.
All isolates were susceptible to vancomycin, metronidazole, amoxicillin/clavulanate and meropenem. Resistance to clindamycin, erythromycin, ceftriaxone and moxifloxacin was observed in 73.3%, 35.2%, 23.8% and 21.0% of the isolates, respectively. The in vitro activity of fidaxomicin (MIC50/MIC90 0.06/0.25 mg/L) was superior to vancomycin (MIC50/MIC90 1/2 mg/L) and metronidazole (MIC50/MIC90 0.25/0.25 mg/L). Rifaximin exhibited potent activity against 85.7% of the isolates (MIC ≤0.03 mg/L), and its MIC50 (0.015 mg/L) was the lowest of all antimicrobials tested. The prevalence of multi-drug resistant C. difficile, defined by resistance to ≥3 antimicrobials, was 21.9% (23/105).
High level resistance against multiple classes of antimicrobial was observed, emphasising the need for enhanced antimicrobial stewardship and educational programmes to effectively disseminate information regarding appropriate use of antimicrobials to healthcare workers and the general public.