Temporal Variations in Patterns of Clostridioides difficile Strain Diversity and Antibiotic Resistance in Thailand.

Supapit Wongkuna,Phurt Harnvoravongchai,Tavan Janvilisri,Natamon Malaisri,Surang Chankhamhaengdecha,Sathid Aimjongjun,Amornrat Aroonnual,Matthew Phanchana

doi:10.3390/antibiotics10060714

Supapit Wongkuna, Phurt Harnvoravongchai + Show 6 more

Open Access

https://doi.org/10.3390/antibiotics10060714

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Abstract

Clostridioides difficile has been recognized as a life-threatening pathogen that causes enteric diseases, including antibiotic-associated diarrhea and pseudomembranous colitis. The severity of C. difficile infection (CDI) correlates with toxin production and antibiotic resistance of C. difficile. In Thailand, the data addressing ribotypes, toxigenic, and antimicrobial susceptibility profiles of this pathogen are scarce and some of these data sets are limited. In this study, two groups of C. difficile isolates in Thailand, including 50 isolates collected from 2006 to 2009 (THA group) and 26 isolates collected from 2010 to 2012 (THB group), were compared for toxin genes and ribotyping profiles. The production of toxins A and B were determined on the basis of toxin gene profiles. In addition, minimum inhibitory concentration of eight antibiotics were examined for all 76 C. difficile isolates. The isolates of the THA group were categorized into 27 A−B+CDT− (54%) and 23 A-B-CDT- (46%), while the THB isolates were classified into five toxigenic profiles, including six A+B+CDT+ (23%), two A+B+CDT− (8%), five A−B+CDT+ (19%), seven A−B+CDT− (27%), and six A−B−CDT− (23%). By visually comparing them to the references, only five ribotypes were identified among THA isolates, while 15 ribotypes were identified within THB isolates. Ribotype 017 was the most common in both groups. Interestingly, 18 unknown ribotyping patterns were identified. Among eight tcdA-positive isolates, three isolates showed significantly greater levels of toxin A than the reference strain. The levels of toxin B in 3 of 47 tcdB-positive isolates were significantly higher than that of the reference strain. Based on the antimicrobial susceptibility test, metronidazole showed potent efficiency against most isolates in both groups. However, high MIC values of cefoxitin (MICs 256 μg/mL) and chloramphenicol (MICs ≥ 64 μg/mL) were observed with most of the isolates. The other five antibiotics exhibited diverse MIC values among two groups of isolates. This work provides evidence of temporal changes in both C. difficile strains and patterns of antimicrobial resistance in Thailand.

Highlights

Clostridioides difficile, belonging to the family Clostridiaceae and genus Clostridioides, is an obligate anaerobic, Gram-positive, spore-forming, toxin-producing bacillus [1,2]
C. difficile isolates were classified based on molecular features, including toxin genes and the 16S–23S rRNA intergenic spacer regions [33,34]
Isolates used in this study were obtained from the patients with C. difficile infection (CDI), consistent with previous studies, non-toxigenic strains were highly detected from clinical samples due to the mix of both the non-toxigenic and toxigenic populations and isolation method [10,39,40]

Summary

Introduction

Clostridioides difficile (formerly Clostridium difficile), belonging to the family Clostridiaceae and genus Clostridioides, is an obligate anaerobic, Gram-positive, spore-forming, toxin-producing bacillus [1,2]. This organism is well known to cause infectious diarrhea in humans, ranging from mild diarrhea to severe pseudomembranous colitis [3]. Toxin A is an enterotoxin encoded by tcdA, and toxin B is a cytotoxin encoded by tcdB. Both toxins belong to the family of large clostridial toxins (LCTs) and are located within a 19.6 kb pathogenicity locus (PaLoc) [5]. CDTs are not directly required for diseases, they have been known to promote the virulence of C. difficile by impairing host immunity and acting in synergy with toxins A and B, exacerbating toxicity [7]

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