Prevalence of Clostridium sPP. in diarrhoeic and healthy dogs ...

Ann. Fac. Medic. Vet. di Parma (Vol. XXVII, 2007) pag. 143 - pag. 156by complex qualitative changes from a predominantly aerobic flora in the smallintestine to a predominantly anaerobic flora in the large intestine. There is a widevariation in the bacterial flora between normal individuals, and concentrations maybe affected by a variety of circumstances or behaviours, including environment, diet,scavenging and coprophagia. Increased numbers of bacteria in the small intestinecarry an increased risk of a harmful outcome. Whether this is manifest clinically willdepend on individual circumstances, including the composition of the diet whichbacteria can convert to potentially harmful metabolites. The nature of a host responseto the increased load could also be important, and this may involve stimulation ofimmunoglobulin and mucus production, suppression of potentially damaging cellmediated immune responses, a compensatory production of structural and functionalepithelial cell proteins, and increased epithelial cell turnover. The threshold betweenapparent normality and clinical disease may therefore differ between individuals andbe influenced by a delicate balance between the microflora and the host. Clinicaldisease associated with bacterial overgrowth is a very common problem in dogs andoccurs when this balance is tipped against the host [1].Primary enteric bacterial pathogens can also cause acute clinical diseasesince they possess virulence factors with adverse effect on the intestine. Adherenceto the surface or invasion of the mucosa facilitate long-term colonization by certainenteropathogens, predisposing to a carrier status or chronic disease, the outcomeprobably depending on expression of virulence determinants and the host response[1].Since dogs are carnivorous, the total length of their intestine in relation to thebody length is somewhat shorter and the motility slower than in humans. As a wholethe digestive tract of dog, however, resembles that of humans and the physiologyis similar in many ways. Like humans, dogs utilize intestinal microbiota in theirphysiology and both are homothermic mammals. The pH values in the differentcompartments of the digestive tract are also comparable to those of human, being thepH in the dog stomach 3, in duodenum and jejunum 6, in ileum 7.5, in colon 6.5 andin feces 6.2 [10].The main cultivable bacterial groups and most common findings in humansand dogs are similar, including clostridia, bacteroides, streptococci, coliforms,enterococci, lactobacilli and veillonellae with increasing counts towards the largeintestine [10]. Most intestinal pathogens cause similar clinical symptoms in dogs asin humans (C. difficile, multiresistant Gram-negatives, enterococci, staphylococci).The most common intestinal dysfunction in dogs is diarrhoea. Another commondisturbance, small intestinal bacterial overgrowth, composing of Escherichia coli,enterococci and clostridia is associated with raised serum folate, reduced serumvitamin B12 concentrations and altered mucosal permeability and function [10].In the most cases of bacterial overgrowth, the cause cannot be identified, buthost factors known to predispose to bacterial overgrowth include defective gastric acidsecretion, interference with normal motility or stasis, and defective local immunity[1]. Other factors, as a potentially stressful or contamined environment, diet andcoprophagia, may also play a role and could contribute to the relatively high numbersof bacteria reported in kennelled dogs [1]. The damaging consequences of overgrowth145