In Situ Molecular Diagnosis and Histopathological Characterization of EnteroadherentEnterococcus hiraeInfection in Pre-Weaning-Age Kittens

Abstract

The bacterial causes of diarrhea can be frustrating to identify, and it is likely that many remain undiagnosed. The pathogenic potential of certain bacteria becomes less ambiguous when they are observed to intimately associate with intestinal epithelial cells. In the present study we sought to retrospectively characterize the clinical, in situ molecular, and histopathological features of enteroadherent bacteria in seven unrelated kittens that were presumptively diagnosed with enteropathogenic Escherichia coli (EPEC) on the basis of postmortem light microscopic and, in some cases, microbiological examination. Characterization of the enteroadherent bacteria in each case was performed by Gram staining, in situ hybridization using fluorescence-labeled oligonucleotide probes, PCR amplification of species-specific gene sequences, and ultrastructural imaging applied to formalin-fixed paraffin-embedded sections of intestinal tissue. In only two kittens was EPEC infection confirmed. In the remaining five kittens, enteroadherent bacteria were identified as Enterococcus spp. The enterococci were further identified as Enterococcus hirae on the basis of PCR amplification of DNA extracted from the formalin-fixed, paraffin-embedded tissue and amplified by using species-specific primers. Transmission electron microscopy of representative lesions from E. coli-and Enterococcus spp.-infected kittens revealed coccobacilli adherent to intestinal epithelial cells without effacement of microvilli or cup-and-pedestal formation. Enterococci were not observed, nor were DNA sequences amplified from intestinal tissue obtained from age-matched kittens euthanized for reasons unrelated to intestinal disease. These studies suggest that E. hirae may be a common cause of enteroadherent bacterial infection in pre-weaning-age kittens and should be considered in the differential diagnosis of bacterial disease in this population.Diarrhea is a frequent clinical sign at the time of death or euthanasia of kittens, particularly those residing in shelters or rescue facilities. Enteritis is second only to the specific diagnosis of feline parvovirus infection as the most common cause of kitten mortality identified by histopathology-based studies (2). Aside from viral, protozoal, and helminthic causes of enteritis, the bacterial culprits of diarrhea are particularly problematic to identify. The intestinal tract harbors a diverse population of bacteria that play critical roles in nutrient assimilation, mucosal immunity, and colonization resistance. Recognition of pathogenic bacteria within this population is hampered by our limited knowledge of normal bacterial diversity, the challenge of distinguishing commensal from pathogenic bacteria, the frequent presence of pathogenic bacteria in clinically normal animals, and the ability of commensal bacteria to become pathogenic in genetically susceptible individuals or under abnormal environmental conditions. The pathogenic potential of certain bacteria becomes less ambiguous when they are observed to intimately adh...

Relapse of Enterococcus hirae Prosthetic Valve Endocarditis

“…The source of infection in our patient was probably the digestive tract, as colonoscopy showed multiple colonic polyps. Currently, there is no demonstrated relationship between E. hirae infection and colonic pathology, but very few cases of infections due to this particular bacterium have been reported; however, enterococci are commensal species of the human intestinal tract, and E. hirae has been involved in colonic pathology in animals (6,9). Therefore, we decided to perform a colonoscopy in order to seek intestinal disease, as is recommended for other bacteria colonizing the gastrointestinal tract.…”

Mortality in Kittens Is Associated with a Shift in Ileum Mucosa-Associated Enterococci from Enterococcus hirae to Biofilm-Forming Enterococcus faecalis and Adherent Escherichia coli

“…In recent years certain enterococci, most notably Enterococcus hirae and Enterococcus durans, have been observed in numerous different species of neonatal animals to intimately and extensively colonize the mucosal surface of the small intestine in a manner similar to that of enteropathogenic Escherichia coli (EPEC) (17)(18)(19)(20)(21)(22)(23)(24)(25). While most of these reports describe animals having concurrent signs of diarrhea, the association of enteroadherent enterococci with clinical disease of the gastrointestinal tract in these young animals remains unclear.…”

Diarrhea Caused by <i>Enterococcus villorum</i> in Piglets

“…This view was supported by the current study in which seven unexamined piglets recovered without any treatment. E. durans and E. hirae are capable of causing diarrhea in young animals of several species (Tzipori et al 1984, Collins et al 1988, Rogers et al 1992, Cheon & Chae 1996, Lapointe et al 2000, Nicklas et al 2010, Larsson et al 2014. No distinction was made between E. hirae and E. villorum in reports earlier than 2001, but it is probable that E. hirae induced enteropathy with ascending cholangitis and pancreatitis in a kitten (Lapointe et al 2000) and septicemia in psittacine birds (Devriese et al 1995).…”

“…in piglets, calves, foals and a pup (Tzipori et al 1984, Collins et al 1988, Rogers et al 1992, Cheon & Chae 1996, and by E. hirae in piglets and kittens (Lapointe et al 2000, Nicklas et al 2010, Larsson et al 2014. These organisms are adherent to the surface of villous enterocytes in the small intestine, but the pathogenesis of diarrhea is unknown (Rogers et al 1992, Cheon & Chae 1996, Larsson et al 2014).…”