Clostridium Prevalence and Characterization in Spain

Clostridium perfringens and Clostridium difficile are gram-positive anaerobic bacteria that produce toxins and cause gastrointestinal disease in humans and animals. However, because these bacteria can reside asymptomatically in the gut of healthy hosts, their isolation usually has little diagnostic significance.

Underdiagnosis of clostridial disease, particularly C. difficile infection, has been problematic in human medicine. Fortunately, prevalence surveys of C. difficile have led to improved infection control strategies.

Whether underdiagnosis of C. perfringens and C. difficile is problematic in small animal veterinary medicine is largely unknown, in part because previous veterinary prevalence surveys of these bacteria examined only selected animal populations. In addition, genetic characterization and antibiotic susceptibility testing (AST) on these Clostridium species are uncommonly performed in veterinary hospitals, leaving important knowledge gaps.

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In Madrid, where dog and cat populations have risen by 7% and 81%, respectively, in recent years, a research team determined C. perfringens and C. difficile prevalence and characterization in dogs and cats. Study results were published in Anaerobe.

Sample Collection and Testing

Researchers recruited 17 small animal veterinary clinics in Madrid. During 1 week, the clinics’ veterinarians collected 2 fecal swabs each from 105 dogs and 37 cats, regardless of age, origin, or health status.

For each animal, 1 swab each was tested for C. perfringens and C. difficile. After initial bacterial isolation, the researchers performed toxin profiling, genotyping, and AST.

Clinic and Animal Characteristics

Clinics varied in such ways as size and number of sampled animals. Similar proportions of dogs and cats had diarrhea (approximately 13%) on the day of sampling.

Prevalence

Overall prevalence rates were:

• C. perfringens: dogs, 31%; cats, 20%
• C. difficile: dogs, 5%; cats, 0%

Prevalence varied widely between clinics, likely reflecting clinic heterogeneity.

Three dogs from different clinics shed both bacteria. Statistically, C. perfringens shedding was significantly associated with fecal consistency, with 80% of C. perfringens—positive samples being liquid. C. difficile and age were significantly associated, with most C. difficile shedding occurring in animals age 7 years or older.

Interestingly, neither bacteria were significantly associated with diarrhea or recent antibiotic treatment, leaving unanswered the question about the bacteria’s relevance in causing disease in dogs and cats. More robust statistical analyses will be needed to answer this question, the researchers acknowledged.

Seventeen animals positive for either or both bacteria participated in a follow-up survey 4 months after initial testing. Several of these animals tested negative during the follow-up.

Toxin and Genetic Profiles

Toxinotype A was the most common of several toxinotypes identified in the C. perfringens isolates. The researchers also identified several C. difficile toxinotypes, indicating toxin profile diversity for each bacterium.

Amplified fragment length polymorphism fingerprinting, which differentiates between bacterial strains using DNA fragments, revealed wide genetic diversity in the initial and follow-up surveys. Namely, one C. difficile genotype identified in this study reportedly causes human disease, highlighting the potential risk for zoonotic transmission.

Antibiotic Susceptibility Testing

C. perfringens isolates were susceptible to several antibiotics, including amoxicillin/clavulanic acid, and had low resistant rates (<7%) to other antibiotics. C. difficile isolates were also susceptible to several antibiotics and had resistance rates ranging from 15% to 100% to other antibiotics (eg, 100% resistance to imipenem).

The researchers observed marked genetic diversity among the antibiotic-resistant isolates. Previous studies have reported this finding, yet its importance remains unknown.

Bringing It Together

The researchers concluded that C. perfringens and C. difficile shedding is not common in dogs and cats at veterinary clinics in Madrid. They emphasized, though, that “increased awareness among veterinarians and pet owners of the potential threat that clostridial shedding by pet animals might pose for human health is needed.”

Dr. Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.