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  News from the Maryland Veterinary Medical Association                                                    Summer  2013

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Guidelines for Treating UTI in Dogs and Cats
by Celeste Clements, DVM, DACVIM

Urinary tract disease is common in dogs and cats, and often leads to antibiotic treatment. To encourage rational and appropriate use of antimicrobials for urinary tract infection (UTI) in small animals infectious disease workers, led by J. Scott Weese, collaborated on recommendations for veterinarians, Antimicrobial Use Guidelines for Treatment of Urinary Tract Disease in Dogs and Cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases (2011).Their findings are summarized here.

Establishing an accurate diagnosis of UTI, and characterizing it correctly, are critical to successful management. The readily recognized signs of dysuria, pollakiuria and hematuria have many causes; while urinary tract infection may be the most common cause in dogs, this is not the case in cats, who have a higher incidence of sterile cystitis or urinary calculi. Patients should be evaluated for clinical signs and the presence of an active urine sediment, with quantitative aerobic bacterial cultures and susceptibility (c/s) being advised in all cases.

A cystocentesis sample is preferred unless collection of the sample is contraindicated (eg. severe thrombocytopenia). Catheterized samples are less desirable and have limited utility in female canine patients. Quantitative cultures of cystocentesis samples from a patient with UTI generally yield greater than or equal to 1000 colony forming units/ml (CFU/ml)(Bartges 2010). The authors emphasize that while bacterial counts of greater than or equal to 100,000 CFU/ml and 10,000/ml, in dogs and cats, respectively, may be significant on free catch samples, infection should be confirmed by a quantitative culture on a cystocentesis sample whenever possible due to the possibility of contamination!

It is true, however, that antibiotic choices for uncomplicated UTIs are often empiric rather than guided by susceptibility data. Simple uncomplicated UTI occurs sporadically in an otherwise healthy animal with normal urinary anatomy and function. For these cases amoxicillin or trimethoprim-sulfonamide are suggested, commonly administered for 7-14 days. Clinical trials indicating a shorter duration of treatment are limited.

Treatment of complicated infections, defined as those infections that occur in the presence of an anatomic or functional abnormality or comorbidity that predisposes to persistent infection, recurrent infection or treatment failure, should be guided by c/s testing. Amoxicillin and sulfa drugs are reasonable choices until culture results are available. Recurrent UTI, as defined by more than 3 infections in a one-year period, (Albert et al, 2004) are considered complicated infections and may be due to re-infection, relapse or refractory infection. Identifying the underlying cause(s) is essential to successful management. In most cases patients will be treated for at least four weeks with appropriate antibiotics, but there is little evidence to support this duration of treatment.

Subclinical bacteriuria is a challenging topic. Bacteria noted in the urine in the absence of clinical or cytologic evidence of UTI do not always indicate treatment, unless there is concern for existing or future upper urinary infection, impending orthopedic surgery and implant use, or systemic infection, as might occur in immunocompromised patients or patients with renal disease. Even multiply drug- resistant bacteria such as Enterococcus spp. may be preferentially monitored for development of signs, rather than treated. If treatment is elected, veterinarians should treat these as complicated UTIs.

For upper urinary infections, as with pyelonephritis, treatment with a fluoroquinolone that is excreted in urine in an active form should be initiated immediately, pending results of c/s. Referring those patients with complicated urinary disease or infection with a drug-resistant bacteria to a board certified internist (urologist or infectious disease specialist) may be helpful. Advanced imaging, cystourethroscopy and serial cultures are often needed to define the nature of any underlying problem and to aid with management. Most patients with pyelonephritis should be treated for four to six weeks minimum, although evidence for this specific treatment interval is lacking.

Judicious antimicrobial use is important to limit the emergence of dissemination of multiply drug resistant pathogens that pose a challenge to people and animals. The use of such drugs as vancomycin, carbapenems and linezolid should be carefully considered and justified on the basis of several criteria, to include a) confirmed clinical infection b) resistance to all other reasonable choices and documented susceptibility to the drug in question c) removal of impediments to successful treatment providing for possible cure and 4) upon appropriate consultation with an expert who can advise of other viable options.

The panel has provided an excellent working guideline for addressing UTIs. Other topics such as urinary catheter management and monitoring are discussed in some detail, and a basic antibiotic formulary is included. Interested readers are encouraged to review the complete monograph published in Veterinary Medicine International and share it with colleagues. The article is available for review at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3134992/
Request for complete references should be directed to cclementsdvm@hotmail.com.

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