Prevalence of binary toxin positive Clostridium difficile in diarrhoeal humans in the absence of epidemic ribotype 027

Alan M. McGovern, Grace O. Androga, Daniel R. Knight, Mark W. Watson, Briony Elliott, Niki F. Foster, Barbara J. Chang, Thomas V. Riley

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10 Citations (Scopus)


Virulence of Clostridium difficile is primarily attributed to the large clostridial toxins A and B while the role of binary toxin (CDT) remains unclear. The prevalence of human strains of C. difficile possessing only CDT genes (ABCDT+) is generally low (< 5%), however, this genotype is commonly found in neonatal livestock both in Australia and elsewhere. Zoonotic transmission of C. difficile has been suggested previously. Most human diagnostic tests will not detect ABCDT+ strains of C. difficile because they focus on detection of toxin A and/or B. We performed a prospective investigation into the prevalence and genetic characteristics of ABCDT+ C. difficile in symptomatic humans. All glutamate dehydrogenase or toxin B gene positive faecal specimens from symptomatic inpatients over 30 days (n = 43) were cultured by enrichment, and C. difficile PCR ribotypes (RTs) and toxin gene profiles determined. From 39 culture-positive specimens, 43 C. difficile isolates were recovered, including two ABCDT+ isolates. This corresponded to an ABCDT+ prevalence of 2/35 (5.7%) isolates possessing at least one toxin, 2/10 (20%) AB isolates, 2/3 CDT+ isolates and 1/28 (3.6%) presumed true CDI cases. No link to Australian livestock-associated C. difficile was found. Neither ABCDT+ isolate was the predominant ABCDT+ strain found in Australia, RT 033, nor did they belong to toxinotype XI. Previous reports infrequently describe ABCDT+ C. difficile in patients and strain collections but the prevalence of human ABCDT+ C. difficile is rarely investigated. This study highlights the occurrence of ABCDT+ strains of C. difficile in symptomatic patients, warranting further investigations of its role in human infection.

Original languageEnglish
Article numbere0187658
JournalPLoS One
Issue number11
Publication statusPublished - 1 Nov 2017


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