Evaluation of the Cepheid® Xpert®C. difficile binary toxin (BT) diagnostic assay.

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.

Clostridium difficile Infection in Production Animals and Avian Species: A Review.

Clostridium difficile is the leading cause of antibiotic-associated diarrhea and colitis in hospitalized humans. Recently, C. difficile infection (CDI) has been increasingly recognized as a cause of neonatal enteritis in food animals such as pigs, resulting in stunted growth, delays in weaning, and mortality, as well as colitis in large birds such as ostriches. C. difficile is a strictly anaerobic spore-forming bacterium, which produces two toxins A (TcdA) and B (TcdB) as its main virulence factors. The majority of strains isolated from animals produce an additional binary toxin (C. difficile transferase) that is associated with increased virulence. C. difficile is ubiquitous in the environment and has a wide host range. This review summarizes the epidemiology, clinical presentations, risk factors, and laboratory diagnosis of CDI in animals. Increased awareness by veterinarians and animal owners of the significance of clinical disease caused by C. difficile in livestock and avians is needed. Finally, this review provides an overview on methods for controlling environmental contamination and potential therapeutics available.

Persistence of Clostridium difficile RT 237 infection in a Western Australian piggery.

Clostridium difficile is commonly associated with healthcare-related infections in humans, and is an emerging pathogen in food animal species. There is potential for transmission of C. difficile from animals or animal products to humans. This study aimed to determine if C. difficile RT 237 had persisted in a Western Australian piggery or if there had been a temporal change in C. difficile diversity. C. difficile carriage in litters with and without diarrhea was investigated, as was the acquisition of C. difficile over time using cohort surveys. Rectal swabs were obtained from piglets aged 1-10 days to determine prevalence of C. difficile carriage and samples were obtained from 20 piglets on days 1, 7, 13, 20, and 42 of life to determine duration of shedding. Isolation of C. difficile from feces was achieved by selective enrichment culture. All isolates were characterized by standard molecular typing. Antimicrobial susceptibility testing was performed on selected isolates (n = 29). Diarrheic piglets were more likely to shed C. difficile than the non-diseased (p = 0.0124, χ2). In the cohort study, C. difficile was isolated from 40% samples on day 1, 50% on day 7, 20% on day 13, and 0% on days 20 and 42. All isolates were RT 237 and no antimicrobial resistance was detected. The decline of shedding of C. difficile to zero has public health implications because slaughter age pigs have a low likelihood of spreading C. difficile to consumers via pig meat.

Clostridium difficile in soil conditioners, mulches and garden mixes with evidence of a clonal relationship with historical food and clinical isolates.

With rates of community-associated Clostridium difficile infection (CA-CDI) increasing worldwide, potential reservoirs/sources of C. difficile in the community are being sought. Since C. difficile is found in animal manure and human biosolids, which are composted for agricultural purposes, composted products could be a source. In this study, the presence of C. difficile in composted products, and their genetic relatedness to other previously isolated strains from humans, root vegetables and the environment in Western Australia, was investigated. Overall, C. difficile was found in 22.5% (16/71) of composted products [29.7% (11/37) of soil conditioners, 16.7% (2/12) of mulches and 13.6% (3/22) of garden mixes]. Fifteen C. difficile PCR ribotypes (RTs) were identified, the most common toxigenic strains being RTs 020 and 056. Clostridium difficile RT 056 is commonly associated with CDI in humans and has also been isolated from cattle, root vegetables and the environment (veterinary clinics and lawn) in Australia. High-resolution core-genome analysis of 29 C. difficile RT 056 strains revealed clonal relationships between isolates derived from humans, vegetables, composted products and the environment. These findings provide support for an intricate transmission network between human, food and the environment, further highlighting the importance of a 'One Health' approach for managing CDI.

Antimicrobial susceptibility of Clostridium difficile isolated from food and environmental sources in Western Australia.

We recently reported a high prevalence of Clostridium difficile in retail vegetables, compost and lawn in Western Australia. The objective of this study was to investigate the antimicrobial susceptibility of previously isolated food and environmental C. difficile isolates from Western Australia. A total of 274 C. difficile isolates from vegetables, compost and lawn were tested for susceptibility to a panel of 10 antimicrobial agents (fidaxomicin, vancomycin, metronidazole, rifaximin, clindamycin, erythromycin, amoxicillin/clavulanic acid, moxifloxacin, meropenem and tetracycline) using the agar incorporation method. Fidaxomicin was the most potent agent (MIC50/MIC90, 0.06/0.12 mg/L). Resistance to fidaxomicin and metronidazole was not detected and resistance to vancomycin (0.7%) and moxifloxacin (0.7%) was low. However, 103 isolates (37.6%) showed resistance to at least one agent, and multidrug resistance was observed in 3.9% of the resistant isolates (4/103), all of which came from compost. A significantly greater proportion of compost isolates were resistant to clindamycin, erythromycin and tetracycline compared with food and/or lawn isolates. Clostridium difficile ribotype (RT) 014/020 showed greater clindamycin resistance than other less common RTs (P = 0.008, χ2). Contaminated vegetables, compost and lawn could be playing an intermediary role in the transmission of C. difficile from animals to humans. Environmental strains of C. difficile could also function as a reservoir for antimicrobial resistance genes of clinical relevance. This study provides a baseline for future surveillance of antimicrobial resistance in environmental C. difficile isolates in Australia.

High prevalence of toxigenic Clostridium difficile in public space lawns in Western Australia.

Clostridium difficile is a well-established hospital pathogen. Recently, it has been detected increasingly in patients without hospital contact. Given this rise in community associated infections with C. difficile, we hypothesized that the environment could play an important role in transmission of spores outside the hospital. Lawn samples (311) collected in public spaces in the metropolitan area of Perth, Western Australia, from February to June 2016 were cultured for C. difficile. C. difficile was isolated from the samples by direct and enrichment culture, and characterized by standard molecular methods using toxin gene PCR and ribotyping. The overall prevalence of C. difficile was 59%, new lawn (≤4 months old) was twice as likely as old lawn (>4 months old) to test positive (OR = 2.3; 95%CI 1.16-4.57, p = 0.015) and 35 C. difficile ribotypes were identified with toxigenic ribotype 014/020 (39%) predominating. The highest viable count from lawn soil samples was 1200 CFU/g. These results show that lawns in Perth, Western Australia, harbor toxigenic C. difficile, an important finding. The source of lawn contamination is likely related to modern practice of producing "roll-out" lawn. Further work should focus on identifying specific management practices that lead to C. difficile contamination of lawn to inform prevention and control measures.