Bacterial Enteritis

Introduction

The main aetiological agents involved in bacterial enteritis are reported to be Clostridium perfringens, Clostridium difficile, Campylobacter spp., Salmonella spp and enteropathogenic Escherichia coli (EPEC). However, given that these organisms can be part of the indigenous intestinal microflora, there does not appear to be a simple cause-effect relationship with clinical disease. Clearly, other factors (e.g. within the host or its environment) influence how the disease manifests.

Clostridium perfringens:

Clostridium perfringens is an anaerobic, spore-forming, gram-positive bacillus, which has been typed into five toxigenic phenotypes, A-E. Each elaborates a major toxin and other toxins, including C. perfringens enterotoxin (CPE), a well-characterised virulence factor. Several recent studies have shown an association between the presence of CPE in faeces and diarrhoea. Signs of largebowel diarrhoea predominate characterised by increased frequency of defecation, tenesmus, faecal mucus and haematochezia. C. perfringens has also been implicated in the acute haemorrhagic gastroenteritis syndrome (AHG) in dogs; clinical signs include severe vomiting and diarrhoea, often associated with blood. Onset of signs is peracute and animals can be markedly volumedepleted.
A number of methods to diagnose C. perfringens-associated diarrhoea have been reported including routine bacterial culture, identification of increased spore counts on faecal smears, and detection of CPE in faeces. Although the presence of endospores could help support a diagnosis, detection of CPE is most reliable. Unfortunately, in Europe, there is limited availability of validated assays for detection of CPE, and samples must be shipped to the USA.
For most cases of C. perfringens-associated diarrhoea, animals respond to antimicrobial therapy. Recommended antimicrobials include macrolides (particularly tylosin), ampicillin, and metronidazole. Supportive measures such as dietary modification, is also recommended. Aggressive treatment is required for AHG, including intravenous fluid therapy (usually colloids), and a combination of intravenous bacteriocidal antibacterials (e.g. amoxicillin-clavulanate and enrofloxacin). Cases are initially maintained nil per os, but subsequently dietary management can be instigated.

Clostridium difficile:

Clostridium difficile is a gram-positive, anaerobic spore-forming bacillus, which has been associated with diarrhoea in dogs. Two toxins, toxin A and toxin B, are thought to be primarily responsible for manifestation of clinical signs, although other toxins may also play a role. C. difficile-associated diarrhoea can be diagnosed by routine bacterial culture, identification spores on fecal smears and detection of toxin A or toxin B in faecal specimens with ELISA. Again the latter is reported to be most reliable. Similar to C. perfringens, a strong association has been found between the detection of C. difficile toxin A and the presence of AHDS. This organism is commonly implicated in nosicomial infections and acute diarrhoea outbreaks in veterinary hospitals. Clostridium difficile seems to be less prevalent in cats compared to dogs. The antimicrobial of choice for therapy of C. difficile-associated diarrhoea is metronidazole. [...]