Several Mycoplasma species can be found in the lower urinary tract of healthy dogs, making it difficult to interpret culture studies from dogs with urinary tract infections (UTIs). However, Mycoplasma canis has been implicated in some cases of persistent urinary tract disease. In this study, 9 dogs with persistent UTI were analyzed for Mycoplasma canis (a total of 11 specimens were taken). All 9 dogs had infestations of Mycoplasma canis. However, in 3 of the dogs, mycoplasma was cultivated only from urinary sediments, resulting in lower-than-expected numbers for indication of UTI. Of the 4 dogs that were not euthanized for multiple disease conditions, the 2 females were completely cured with tetracycline alone but the 2 males (although repeatedly treated with tetracycline) recovered fully only after castration.
 

COMMENTARY: Although involved in less than 2% of UTIs, mycoplasma should be considered when clinical signs persist after antimicrobials other than tetracycline have been tried. For intact male dogs, doxycycline may be the best treatment choice for Mycoplasma species because of better prostatic penetration. Mycoplasma canis will grow on standard blood agar but many Mycoplasma and Ureaplasma species will not. Thus, such infections may go unrecognized. Even low quantitative counts of Mycoplasma canis in the urine may represent significant infection.

Mycoplasma canis and urogenital disease in dogs in Norway. L'Abee-Lund TM, Heiene R, Friis F, Ahrens P, Sørum H. VET REC 153:231-235, 2003.