Clostridium difficile: a survey of fecal carriage in cats in a veterinary medical teaching hospital

Molecular epidemiology of Clostridioides difficile in companion animals: Genetic overlap with human strains and public health concerns

Introduction

The changing epidemiology of Clostridioides difficile reflects a well-established and intricate community transmission network. With rising numbers of reported community-acquired infections, recent studies tried to identify the role played by non-human reservoirs in the pathogen's transmission chain. This study aimed at describing the C. difficile strains circulating in canine and feline populations, and to evaluate their genetic overlap with human strains to assess the possibility of interspecies transmission.

Methods

Fecal samples from dogs (n = 335) and cats (n = 140) were collected from two populations (group A and group B) in Portugal. C. difficile isolates were characterized for toxigenic profile and PCR-ribotyping. The presence of genetic determinants of antimicrobial resistance was assessed in all phenotypically resistant isolates. To evaluate the genetic overlap between companion animals and human isolates from Portugal, RT106 (n = 42) and RT014/020 (n = 41) strains from both sources were subjected to whole genome sequencing and integrated with previously sequenced RT106 (n = 43) and RT014/020 (n = 142) genomes from different countries. The genetic overlap was assessed based on core-single nucleotide polymorphism (SNP) using a threshold of 2 SNP.

Results

The overall positivity rate for C. difficile was 26% (76/292) in group A and 18.6% (34/183) in group B. Toxigenic strains accounted for 50% (38/76) and 52.9% (18/34) of animal carriage rates, respectively. The most prevalent ribotypes (RT) were the toxigenic RT106 and RT014/020, and the non-toxigenic RT010 and RT009. Antimicrobial resistance was found for clindamycin (27.9%), metronidazole (17.1%) and moxifloxacin (12.4%), associated with the presence of the ermB gene, the pCD-METRO plasmid and point mutations in the gyrA gene, respectively. Both RT106 and RT014/020 genetic analysis revealed several clusters integrating isolates from animal and human sources, supporting the possibility of clonal interspecies transmission or a shared environmental contamination source.

Discussion

This study shows that companion animals may constitute a source of infection of toxigenic and antimicrobial resistant human associated C. difficile isolates. Additionally, it contributes with important data on the genetic proximity between C. difficile isolates from both sources, adding new information to guide future work on the role of animal reservoirs in the establishment of community associated transmission networks and alerting for potential public health risk.

Clostridioides difficile infection: an emerging zoonosis?

INTRODUCTION

Clostridioides difficile (C. difficile) infection (CDI) is the most common cause of antibiotic-associated diarrhea and one of the common infections in healthcare facilities. In recent decades, there has been an emerging threat of community-acquired CDI (CA-CDI). Environmental transmission of C. difficile in the community setting has become a major concern, and animals are an important reservoir for C. difficile causing human diseases.

AREAS COVERED

In this article, the molecular epidemiology of C. difficile in animals and recent evidences of zoonotic transfer to humans are reviewed based on an electronic search in the databases of PubMed and Google Scholar.

EXPERT OPINION

C. difficile can be found in stool from diarrheal dogs and cats; therefore, household pets could be a potential source. C. difficile will threaten human health because hypervirulent C. difficile ribotype 078 strains have been found in retail chickens, pig farms, and slaughterhouses. Risk factors for fecal C. difficile carriage in animals include young age, dietary changes, and antibiotic abuse in domestic animals. With the advent of whole genome sequencing techniques, there will be more solid evidence indicating zoonotic transfer of C. difficile from animals to humans.

High contamination rates of shoes of veterinarians, veterinary support staff and veterinary students with Clostridioides difficile spores

Clostridioides difficile is often found in animals and their environment. However, not much has been reported on veterinary clinics environment in terms of the spore load, prevalence and PCR ribotype diversity. The aim of this study was to assess the prevalence of C. difficile on shoe soles of veterinarians, veterinary support staff and veterinary students at the Veterinary Faculty campus. Altogether, 50 shoe sole swabs were collected, and the positivity rates ranged from 86.7% in swabs from veterinarians to 100% in swabs from support staff and students. Non‐toxigenic and toxigenic strains representing toxinotypes 0, IV and XIX were isolated and distributed into 17 different PCR ribotypes, most common being 010, 014/020, SLO002 and 009. PCR ribotype 010 was the most prevalent and isolated from shoe soles sampled in 6/7 areas. Students' shoes had highest ribotype diversity (15/17 PCR ribotypes) but showed a low overlap with ribotype isolated from vets and support staff shoes. Veterinary students are likely the main vectors of C. difficile spores transmissions among veterinary teaching clinics and the hospital.

Clostridioides difficile carriage in animals and the associated changes in the host fecal microbiota

The relationship between the gut microbiota and Clostridioides difficile, and its role in the severity of C. difficile infection in humans is an area of active research. Intestinal carriage of toxigenic and non-toxigenic C. difficile strains, with and without clinical signs, is reported in animals, however few studies have looked at the risk factors associated with C. difficile carriage and the role of the host gut microbiota. Here, we isolated and characterized C. difficile strains from different animal species (predominantly canines (dogs), felines (cats), and equines (horses)) that were brought in for tertiary care at North Carolina State University Veterinary Hospital. C. difficile strains were characterized by toxin gene profiling, fluorescent PCR ribotyping, and antimicrobial susceptibility testing. 16S rRNA gene sequencing was done on animal feces to investigate the relationship between the presence of C. difficile and the gut microbiota in different hosts. Here, we show that C. difficile was recovered from 20.9% of samples (42/201), which included 33 canines, 2 felines, and 7 equines. Over 69% (29/42) of the isolates were toxigenic and belonged to 14 different ribotypes including ones known to cause CDI in humans. The presence of C. difficile results in a shift in the fecal microbial community structure in both canines and equines. Commensal Clostridium hiranonis was negatively associated with C. difficile in canines. Further experimentation showed a clear antagonistic relationship between the two strains in vitro, suggesting that commensal Clostridia might play a role in colonization resistance against C. difficile in different hosts.

Prevalence, Colonization, Epidemiology, and Public Health Significance of Clostridioides difficile in Companion Animals

Clostridioides difficile, previously Clostrdium difficile, is a major cause of antibiotic-associated enteric disease in humans in hospital settings. Increased incidence of C. difficile infection (CDI) in community settings raises concerns over an alternative source of CDI for humans. The detection of genetically similar and toxigenic C. difficile isolates in companion animals, including asymptomatic pets, suggests the potential role of household pets as a source of community-associated CDI. The close association between companion animals and humans, in addition to the use of similar antibiotics in both species, could provide a selective advantage for the emergence of new C. difficile strains and thus increase the incidental transmission of CDI to humans. Therefore, screening household pets for C. difficile is becoming increasingly important from a public health standpoint and may become a part of routine testing in the future, for the benefit of susceptible or infected individuals within a household. In this review, we analyze available information on prevalence, pathophysiology, epidemiology, and molecular genetics of C. difficile infection, focusing on companion animals and evaluate the risk of pet-borne transmission of CDI as an emerging public health concern. Molecular epidemiological characterization of companion animal C. difficile strains could provide further insights into the interspecies transmission of CDI. The mosaic nature of C. difficile genomes and their susceptibility to horizontal gene transfer may facilitate the inter-mixing of genetic material, which could increase the possibility of the emergence of new community-associated CDI strains. However, detailed genome-wide characterization and comparative genome analysis are warranted to confirm this hypothesis.

Clostridium (Clostridioides) difficile in animals

Clostridium (Clostridioides) difficile is a gram-positive, spore-forming bacterium that is an important cause of disease in people, a variably important cause of disease in some animal species, and an apparently harmless commensal in others. Regardless of whether it is a known pathogen in a particular species, it can also be found in healthy individuals, sometimes at high prevalences and typically with higher rates of carriage in young individuals. As it is investigated in more animal species, it is apparent that this bacterium is widely disseminated in a diverse range of domestic and wild animal species. Although it can be found in most species in which investigations have been performed, there are pronounced intra- and inter-species differences in prevalence and clinical relevance. A wide range of strains can be identified, some that appear to be animal associated and others that are found in humans and animals. A large percentage of strains that cause disease in people can at least sporadically be found in animals. It is a potentially important zoonotic pathogen, but there is limited direct evidence of animal-human transmission. Although C. difficile has been studied extensively over the past few decades, it remains an enigmatic organism in many ways.

Clostridioides (Clostridium) Difficile in Food-Producing Animals, Horses and Household Pets: A Comprehensive Review

Clostridioides (Clostridium) difficile is ubiquitous in the environment and is also considered as a bacterium of great importance in diarrhea-associated disease for humans and different animal species. Food animals and household pets are frequently found positive for toxigenic C. difficile without exposing clinical signs of infection. Humans and animals share common C. difficile ribotypes (RTs) suggesting potential zoonotic transmission. However, the role of animals for the development of human infection due to C. difficile remains unclear. One major public health issue is the existence of asymptomatic animals that carry and shed the bacterium to the environment, and infect individuals or populations, directly or through the food chain. C. difficile ribotype 078 is frequently isolated from food animals and household pets as well as from their environment. Nevertheless, direct evidence for the transmission of this particular ribotype from animals to humans has never been established. This review will summarize the current available data on epidemiology, clinical presentations, risk factors and laboratory diagnosis of C. difficile infection in food animals and household pets, outline potential prevention and control strategies, and also describe the current evidence towards a zoonotic potential of C. difficile infection.

The Comparative Pathology of Clostridium difficile-associated Disease

Clostridium difficile is a confirmed pathogen in a wide variety of mammals, but the incidence of disease varies greatly in relation to host species, age, environmental density of spores, administration of antibiotics, and possibly, other factors. Lesions vary as well, in severity and distribution within individuals, and in some instances, age groups, of a given species. The cecum and colon are principally affected in most species, but foals and rabbits develop severe jejunal lesions. Explanations for variable susceptibility of species, and age groups within a species, are largely speculative. Differences in colonization rates and toxin-receptor densities have been proposed. Clostridium difficile-associated disease is most commonly diagnosed in Syrian hamsters, horses, and neonatal pigs, but it is reported sporadically in many other species. The essential virulence factors of C. difficile are large exotoxins, toxin A (TcdA) and toxin B (TcdB). Receptor-mediated endocytosis of the toxins is followed by endosomal acidification, a necessary step for conversion of the toxin to its active form in the cytosol. Cell-surface receptors have been characterized for TcdA, but remain to be identified for TcdB. Both TcdA and TcdB disrupt the actin cytoskeleton by disrupting Rho-subtype, intracellular signaling molecules. Disruption of the actin cytoskeleton is catastrophic for cellular function, but inflammation and neurogenic stimuli are also involved in the pathogenesis of the disease.

Clostridium difficile infection: Early history, diagnosis and molecular strain typing methods

Recognised as the leading cause of nosocomial antibiotic-associated diarrhoea, the incidence of Clostridium difficile infection (CDI) remains high despite efforts to improve prevention and reduce the spread of the bacterium in healthcare settings. In the last decade, many studies have focused on the epidemiology and rapid diagnosis of CDI. In addition, different typing methods have been developed for epidemiological studies. This review explores the history of C. difficile and the current scope of the infection. The variety of available laboratory tests for CDI diagnosis and strain typing methods are also examined.

Clostridium difficile in Food and Animals: A Comprehensive Review

Zoonoses are infections or diseases that can be transmitted between animals and humans through direct contact, close proximity or the environment. Clostridium difficile is ubiquitous in the environment, and the bacterium is able to colonise the intestinal tract of both animals and humans. Since domestic and food animals frequently test positive for toxigenic C. difficile, even without showing any signs of disease, it seems plausible that C. difficile could be zoonotic. Therefore, animals could play an essential role as carriers of the bacterium. In addition, the presence of the spores in different meats, fish, fruits and vegetables suggests a risk of foodborne transmission. This review summarises the current available data on C. difficile in animals and foods, from when the bacterium was first described up to the present.

Enteropathogenic bacteria in dogs and cats: diagnosis, epidemiology, treatment, and control

This report offers a consensus opinion on the diagnosis, epidemiology, treatment, and control of the primary enteropathogenic bacteria in dogs and cats, with an emphasis on Clostridium difficile, Clostridium perfringens, Campylobacter spp., Salmonella spp., and Escherichia coli associated with granulomatous colitis in Boxers. Veterinarians are challenged when attempting to diagnose animals with suspected bacterial-associated diarrhea because well-scrutinized practice guidelines that provide objective recommendations for implementing fecal testing are lacking. This problem is compounded by similar isolation rates for putative bacterial enteropathogens in animals with and without diarrhea, and by the lack of consensus among veterinary diagnostic laboratories as to which diagnostic assays should be utilized. Most bacterial enteropathogens are associated with self-limiting diarrhea, and injudicious administration of antimicrobials could be more harmful than beneficial. Salmonella and Campylobacter are well-documented zoonoses, but antimicrobial administration is not routinely advocated in uncomplicated cases and supportive therapy is recommended. Basic practices of isolation, use of appropriate protective equipment, and proper cleaning and disinfection are the mainstays of control. Handwashing with soap and water is preferred over use of alcohol-based hand sanitizers because spores of C. difficile and C. perfringens are alcohol-resistant, but susceptible to bleach (1:10 to 1:20 dilution of regular household bleach) and accelerated hydrogen peroxide. The implementation of practice guidelines in combination with the integration of validated molecular-based testing and conventional testing is pivotal if we are to optimize the identification and management of enteropathogenic bacteria in dogs and cats.

Bacterial enteritis in dogs and cats: diagnosis, therapy, and zoonotic potential

A variety of bacteria are known or suspected of being able to cause enteritis in dogs and cats. Campylobacter spp, Clostridium difficile, Clostridium perfringens, and Salmonella spp are most commonly implicated, but many other organisms are likely involved. Poor understanding of the intestinal microflora and the fact that many, if not all, of these microorganisms can also be found in healthy individuals complicates testing, thereby affecting the use of specific treatments and assessment of potential infection control and zoonotic disease risks. An understanding of the strengths and limitations of various diagnostic options is important for the management of canine and feline enteritis.

Prevalence and risk factors for Clostridium difficile colonization in dogs and cats hospitalized in an intensive care unit

Clostridium difficile is the most common cause of hospital- and antimicrobial-associated diarrhea in hospitalized humans however the role of C. difficile in diarrhea in dogs has not been defined. A prospective study of C. difficile colonization in dogs and cats was conducted in a veterinary teaching hospital intensive care unit (ICU). Rectal swabs were taken from patients upon admission to the ICU and every third day of hospitalization until discharge or death. C. difficile was isolated from 73/402 (18%) animals; 69% of isolates were toxigenic. Community-associated colonization was identified in 39/366 (11%) of animals that were sampled at the time of admission, while C. difficile was subsequently isolated from 27 of the remaining 327 (8.3%) animals that had a negative admission swab. C. difficile was isolated from seven other dogs during hospitalization, but the origin was unclear because the admission swab was not collected. Administration of antimicrobials prior to admission and administration of immunosuppressive drugs during hospitalization were risk factors for hospital-associated colonization (P=0.006, OR 4.05, 95% CI 1.4-10.8). Acquisition of C. difficile during hospitalization in the ICU was associated with the development of diarrhea (P=0.004). Two ribotypes, one toxigenic and one non-toxigenic, predominated.

Implications of the changing face of Clostridium difficile disease for health care practitioners

Recent reported outbreaks of Clostridium difficile-associated disease in Canada have changed the profile of C difficile infections. Historically, C difficile disease was thought of mainly as a nosocomial disease associated with broad-spectrum antibiotics, and the disease was usually not life threatening. The emergence of an epidemic strain, BI/NAP1/027, which produces a binary toxin in addition to the 2 classic C difficile toxins A and B and is resistant to some fluoroquinolones, was associated with large numbers of cases with high rates of mortality. Recently, C difficile has been reported more frequently in nonhospital-based settings, such as community-acquired cases. The C difficile disease is also being reported in populations once considered of low risk (children and young healthy women). In addition, poor response to metronidazole treatment is increasing. Faced with an increasing incidence of C difficile infections and the changing profile of patients who become infected, this paper will reexamine the current concepts on the epidemiology and treatment of C difficile-associated disease, present new hypotheses for risk factors, examine the role of spores in the transmission of C difficile, and provide recommendations that may enhance infection control practices.

PCR ribotyping of Clostridium difficile isolates originating from human and animal sources

Molecular typing of Clostridium difficile isolates from animals and humans may be useful for evaluation of the possibility for interspecies transmission. The objective of this study was to evaluate C. difficile isolates from domestic animals and humans using PCR ribotyping. Isolates were also tested using PCR for the presence of genes encoding toxins A and B. One hundred and thirty-three isolates of C. difficile from dogs (n = 92), horses (n = 21) and humans (n = 20), plus one each from a cat and a calf, were evaluated. Overall, 23 ribotypes were identified. Of these, nine were identified from dogs, 12 from horses, seven from humans and one each from the cat and calf. In dogs, humans and horses, one or two different ribotypes predominated. Overall, 25 % of isolates from humans were indistinguishable from isolates from one or more animal species. Genes encoding C. difficile toxins A and B were detected in all human, equine and bovine isolates, and in 69 % of canine isolates. While different ribotypes appear to predominate in different mammalian species, several indistinguishable strains may be found in multiple species. This suggests that there is a potential for interspecies transmission of C. difficile and epidemiological studies are warranted.

Clostridium difficile infections in animals with special reference to the horse. A review

In human medicine, Clostridium (C.) difficile is since many years a well-known cause of nosocomial diarrhea induced by antibiotic treatment. In horses, C. difficile was recently suggested as a possible enteric pathogen. The bacterium is associated with acute colitis in mature horses following treatment with antibiotics. C. difficile, and/or its cytotoxin, is also associated with acute colitis in mares when their foals are being treated with erythromycin and rifampicin for Rhodococcus equi pneumonia. The colitis can have resulted from an accidental ingestion of erythromycin by the mares. In an experimental study it was also demonstrated in mature horses that erythromycin can induce severe colitis associated with proliferation of C. difficile. A new interesting finding was that in healthy foals younger than 14 days, C. difficile was isolated from every third foal whereas older foals proved negative. In this paper the current state of knowledge of C. difficile infections in animals, especially in horses, is reviewed. A short description is given of the historical background of Clostridium difficile and the antibiotic-associated colitis and diarrhea caused by infection with this bacterium. The taxonomy of Clostridium difficile is described extensively. A summary is given of the diseases associated with clostridia infections in animals. Special attention is paid to the pathogenesis, epidemiology, clinical symptoms, laboratory diagnosis, and pathology of Clostridium difficile infections in horses. Finally, some other bacterial causes of colitis in horses are discussed shortly.

Suspected Clostridium difficile-associated diarrhea in two cats

Two adult cats from the same household developed acute diarrhea. Clostridium difficile toxins were detected in the feces of both cats, whereas other recognized causes of diarrhea were not identified. Supportive medical treatment and metronidazole were administered and both cats responded well. A fecal sample obtained from 1 of the affected cats after treatment and a fecal sample obtained from a clinically normal cat in the household did not contain C difficile toxins. The role of C difficile in enteric disease in cats has not been extensively studied and is unclear; however, our findings suggest that toxigenic strains of C difficile may cause diarrhea in cats.

Isolation of environmental Clostridium difficile from a veterinary teaching hospital

An environmental survey of a veterinary teaching hospital for the presence of Clostridium difficile was performed using contact plates and cycloserine-cefoxitin-fructose with 0.1% sodium taurocholate agar. Clostridium difficile was isolated from 24 of 381 sites (6.3%). Growth was obtained from 4.5% (9/202) of sites sampled in the Large Animal Clinic, from 8.1% (13/160) of sites within the Small Animal Clinic, and from 20% (2/10) of sites sampled elsewhere. Fourteen of 21 strains tested produced toxins in vitro. A geographic association was found with areas in the large animal clinic where nosocomial C. difficile diarrhea in horses had previously been diagnosed. Several other sites with a potential for nosocomial transmission of the organism were identified. Areas from which C. difficile was isolated tended to be areas with high animal traffic, with increased chance of fecal contamination, and with rough, difficult to clean surfaces. This study documents the prevalence of this organism in the environment and its potential role in nosocomial disease.