Antimicrobial susceptibility and toxin production of Clostridium difficile isolated from diarrheal patients during 2012-2015

Abstract

Background: Clostridium difficile infection affects people who have been treated with antibiotics and long-term care facilities. C. difficile release two protein toxins, toxin A and toxin B that are the major virulence factors. C. difficile plays important role in hospital-associated diarrhea around the world with wide range of clinical symptoms from asymptomatic carrier, mild to severe diarrhea, colitis, pseudomembranous colitis. Objectives: To investigate the prevalence of toxigenic C.difficile by multiplex PCR and to determine antimicrobial susceptibility of C. difficile isolated from diarrheal patients using agar dilution method. Materials and methods: A total of 49 isolates of C. difficile from stool specimens of diarrheal patients with suspected antibiotic-associated diarrhea during 2012-2015 were included. Detection of toxin genes by multiplex PCR and minimum inhibitory concentration (MIC) by agar dilution were performed. Results: C. difficile isolates were classified into three groups according to toxin genes found as following 1) negative detection of types A and B toxin genes (A-B-) (29 isolates, 3.36%), 2) negative detection of type A toxin gene but positive detection of type B toxin gene (A-B+) (14 isolates, 1.62%), 3) positive detection of type A and B toxin genes (A+B+) (6 isolates, 0.69%). Binary toxin genes were not found in any isolate. Results of MIC for 9 drugs were as following; all isolates were sensitive to vancomycin (MIC 0.25-1 μg/mL) and Metronidazole (MIC 0.25-2 μg/mL). All isolates were resistant to clindamycin (MIC=8 to >256 μg/ml, MIC50=32 μg/mL). Approximately 65.7% of isolates were sensitive to moxifloxacin (MIC 1-4 μg/mL). Most isolates were sensitive to tetracycline (MIC128 μg/mL (MIC50=4 μg/mL), 0.5-32 μg/mL (MIC50=1 μg/mL) and 0.125-128 μg/mL (MIC50=2 μg/mL), respectively. Conclusion: Antimicrobial susceptibility and toxin production of C. difficile are useful for monitoring the severity of disease and rate of resistant to antibiotics. The study found that the majority of metronidazole and vancomycin were effective for treatment of C. difficile diarrheal infection in Thailand. Journal of Associated Medical Sciences 2017; 50(2): 187-196. Doi: 10.14456/jams.2017.14

Keywords

• Clostridium difficile
• agar dilution
• minimum inhibitory concentration (MIC)
• antimicrobial susceptibility