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Risk Factors for Enterococcal Bacteriuria in Dogs

Shelly J. Olin, DVM, DACVIM (SAIM), University of Tennessee

Urology & Nephrology

|July/August 2021

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In the literature

Wood MW, Lepold A, Tesfamichael D, Lasarev MR. Risk factors for enterococcal bacteriuria in dogs: a retrospective study. J Vet Intern Med. 2020;34(6):2447-2453.


Enterococcus spp are commensals of the GI tract in dogs. These bacteria are generally considered to have low virulence, but they can be pathogenic and colonize in the bile, blood, and urine in dogs.1-4 An established infection can be difficult to eradicate because Enterococcus spp rapidly acquire multidrug antimicrobial resistance.5 

This study sought to identify risk factors that predispose dogs to enterococcal bacteriuria. Records of 70 dogs with Enterococcus spp bacteriuria were reviewed and compared with those of 70 dogs with Escherichia coli bacteriuria to observe clinical and pathologic variables. Similar to other studies, Enterococcus faecalis was the predominant species identified in 61% of cases.1,6 This species is noteworthy and relevant to clinical practice because it contains more virulence genes and expresses higher levels of antimicrobial resistance as compared with other species.7,8

Of those dogs with Enterococcus spp infection, 60.6% had a history of recurrent bacteriuria, which was more common than in dogs with E coli bacteriuria. Lower urinary tract (LUT) anatomic abnormalities, uroliths, and the presence of LUT neoplasia were also more common in dogs with Enterococcus spp bacteriuria. 

Studies in mice9,10 and humans11,12 suggest that local inflammation and proteinuria, specifically fibrinogen and inflammatory mediators (ie, interleukin 6, interleukin 1β), can cause predisposition to colonization with Enterococcus spp. The current study was not designed to assess this predisposition in dogs, but an association with previous infection or urinary tract injury in dogs with enterococcal infection was noted.

Limitations of this study included a low number of dogs with certain comorbidities that compromised the ability to calculate an odds ratio (ie, strength of association between events) for these variables, as well as incomplete medical records for some dogs. It is possible that enterococcal UTI has risk factors not evaluated in this study.


Key pearls to put into practice:


Risk factors for Enterococcus spp bacteriuria in dogs include a history of recurrent bacteriuria, LUT abnormalities, uroliths, and LUT neoplasia.



Enterococcus spp generally have low virulence, but they can colonize in the bile, blood, and urine of dogs. Eradication can be difficult once an enterococcal infection is established, and these bacteria can rapidly acquire antimicrobial resistance.


In this study, ≈55% of dogs infected with Enterococcus spp in the urinary tract were presented with LUT signs (eg, stranguria, pollakiuria, dysuria, gross hematuria); thus, up to 45% of cases may have been subclinical.


Enterococcus spp bacteriuria could serve as a marker of underlying LUT inflammation if LUT inflammation promotes colonization with these bacteria in dogs, similar to what is seen in humans.


For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

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