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Difficult bacterial urinary tract infections: recurrent infections


During preventative therapy, urine samples collected by cystocentesis should be recultured at appropriate intervals (so-called surveillance cultures). Samples should not be collected by catheterization, as catheters may cause iatrogenic infection. Urine samples should not be collected by voiding as it may be impossible to distinguish bacterial contaminants in voided samples from pathogens.

Surveillance cultures of urine for bacteria should be performed at shorter intervals initially (after first week of treatment and, if sterile, after the fourth week of treatment). If there are no signs of bacteria-induced urinary tract disease, and the urine is sterile, surveillance intervals may be extended to every eight to 12 weeks.

Any time bacteria are identified, a "breakthrough" infection should be suspected. Recurrences during prophylactic therapy may be associated with poor compliance (Table 4).

Compare bacterial culture results to previous bacterial isolates to determine whether a relapse or reinfection has occurred. The recurrent infection should be treated for an appropriate period with therapeutic dosages (so-called "full dose") of an antimicrobial drug selected on the basis of susceptibility tests. Once the infection has been eradicated and the associated inflammatory response subsides, preventative therapy may be resumed.

Following six to nine months of consecutive negative urine cultures and urinalysis results indicating that the host defenses are functioning adequately, therapy may be discontinued on a trial basis to determine if re-infection will occur. If abnormalities in host defenses have healed, UTI may not recur. If UTI develops within a short period, the procedures outlined above should be repeated.

Caveat: Bacterial infections should be eradicated from the urinary tract prior to prophylactic therapy. Therefore, low-dose preventative antimicrobial therapy would be inappropriate for management of patients with recurrent bacterial UTI due to relapses since by definition viable bacteria are still present in the urinary tract.

Dr. Osborne, a diplomate of the American College of Veterinary Internal Medicine, is professor of medicine in the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota.


Source: DVM360 MAGAZINE,
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