Therapeutic caveats: Difficult urinary tract infections
Aug 01, 2005
As discussed in last month's Diagnote, the underlying causes of bacterial urinary tract infections (UTIs) encompass transient or persistent abnormalities in host defenses.
It follows that protocols designed to safely and effectively eliminate UTIs should include:
The most commonly reported bacterial isolates from dogs with UTIs have been Escherichia coli (~45 percent), Staphylococcus spp. (~10 percent), Proteus spp. (~10 percent), Klebsiella spp. (~10 percent), Enterococcus spp. (~5 percent) and Streptococcus (~5 percent).
Caveat: Patients with acute onsets of uncomplicated bacterial UTIs often "respond" to empirical antimicrobial treatment. Therefore, making an empirical, but educated, "guess" of the proper antibiotic to treat patients with acute onsets of uncomplicated bacterial UTI has been an accepted standard of practice.
However, the standard of practice also includes appropriate follow-up evaluation of the patient to determine the efficacy of therapy. Empirical selection of antimicrobial agents is not recommended for patients that have 1) a history of frequently recurrent clinical signs, and 2) been given antibacterial drugs to treat signs of urinary tract disease in the past three to six weeks.
Susceptibility testing When should antimicrobial agents be selected on the basis of antimicrobial susceptibility tests?
Caveat: Once bacterial urinary tract pathogens that have been exposed to one or more antimicrobial drugs, they often acquire resistance to many commonly used antimicrobial agents. In this setting, the susceptibility of bacterial pathogens is unpredictable, and therefore cannot be accurately predicted from tables derived from untreated patients (Table 1). If a patient with recurrent signs of UTI has recently been given antimicrobics, it is essential that the therapy be re-evaluated on the basis of quantitative culture and antimicrobic susceptibility tests to determine whether changes in susceptibility have occurred.