Identification and pretherapy susceptibility of pathogens in patients with complicated urinary tract infection or acute pyelonephritis enrolled in a clinical study in the United States from November 2004 through April 2006.

OBJECTIVE

The purpose of this study was to assess the pretherapy microbiology and fluoroquinolone susceptibility of pathogens from 650 patients with complicated urinary tract infection (cUTI) or acute pyelonephritis (AP) as part of a multicenter, randomized, controlled clinical trial.

METHODS

In this post hoc analysis of a multicenter, randomized, double-blind study, adults with a clinical diagnosis of cUTI or AP were recruited from 130 community-based and institution-based study centers in the United States from November 2004 through April 2006. Urine and blood culture specimens were identified and tested for susceptibility according to Clinical and Laboratory Standards Institute methods. Presence of a pathogen in the urine culture was confirmed by a colony count of =105 colony-forming units per milliliter. Susceptibility to nonstudy drugs (trimethoprim/sulfamethoxazole [TMP/SMX] and ampicillin) and to study drugs (levofloxacin and ciprofloxacin) was categorized as susceptible, intermediate, or resistant.

RESULTS

Six hundred fifty patients (417 women, 233 men; age range, 18-94 years) with a diagnosis of cUTI or AP were recruited. A total of 68.2% patients (224 men, 219 women) were diagnosed with cUTI, and 31.8% (198 women, 9 men), with AP. Most (646/650 [99.4%]) infections were community acquired. The most common pathogen was Escherichia coli (65.6%), although 12.2% of patients had gram-positive pathogens. Testing for susceptibility to ampicillin and TMP/SMX found that 50.1% and 22.1% of gramnegative pathogens were fully resistant to ampicillin and TMP/SMX, respectively. However, 91.9% of isolates were susceptible to levofloxacin and ciprofloxacin, with 6.5% of isolates resistant or intermediately resistant to levofloxacin, and 9.7% of isolates resistant or intermediately resistant to ciprofloxacin at study entry (P < 0.001 [Stuart-Maxwell test]). All isolates resistant to levofloxacin were also resistant to ciprofloxacin, whereas 6 isolates that were fully susceptible to levofloxacin were fully resistant to ciprofloxacin.

CONCLUSION

In this study, the level of fluoroquinolone susceptibility of urinary pathogens was high (90.6% in cUTI; 98.1% in AP).