ABSTRACT
Strains of Clostridium difficile producing only binary toxin (CDT) are found commonly in animals but not humans. However, human diagnostic tests rarely look for CDT. The Cepheid Xpert C. difficile BT assay detects CDT with equal sensitivity (≥92%) in human and animal faecal samples.
Subject(s)
ADP Ribose Transferases/genetics , Bacterial Proteins/genetics , Clostridioides difficile/genetics , Clostridium Infections/diagnosis , Clostridium Infections/veterinary , Molecular Diagnostic Techniques/methods , Animals , Humans , Sensitivity and SpecificityABSTRACT
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 (A-B-CDT+) 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 A-B-CDT+ 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 A-B-CDT+ 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 A-B-CDT+ isolates. This corresponded to an A-B-CDT+ prevalence of 2/35 (5.7%) isolates possessing at least one toxin, 2/10 (20%) A-B- 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 A-B-CDT+ isolate was the predominant A-B-CDT+ strain found in Australia, RT 033, nor did they belong to toxinotype XI. Previous reports infrequently describe A-B-CDT+ C. difficile in patients and strain collections but the prevalence of human A-B-CDT+ C. difficile is rarely investigated. This study highlights the occurrence of A-B-CDT+ strains of C. difficile in symptomatic patients, warranting further investigations of its role in human infection.
Subject(s)
ADP Ribose Transferases/metabolism , Bacterial Proteins/metabolism , Clostridioides difficile/classification , Clostridioides difficile/genetics , Diarrhea/epidemiology , Diarrhea/microbiology , Ribotyping , Australia/epidemiology , Clostridioides difficile/isolation & purification , Genome, Bacterial , Humans , Polymorphism, Single Nucleotide/genetics , PrevalenceABSTRACT
Clostridium difficile PCR ribotype 033 (RT033) is found in the gastrointestinal tracts of production animals and, occasionally, humans. The illumigene C. difficile assay (Meridian Bioscience, Inc.) failed to detect any of 52 C. difficile RT033 isolates, while all strains signaled positive for the binary toxin genes but were reported as negative for C. difficile by the Xpert C. difficile/Epi assay (Cepheid).
