Interpretation of multiple isolate urine cultures in adult male patients

A retrospective analytical study examined the records of 220 adult males (mean age 64.9 years) to determine the relative probability that multiple urine culture isolates (MUI) represent urinary tract infection (UTI) versus contamination or colonization. Nonculture laboratory data were used to determine the likelihood of UTI. Patients were classified into three categories: group 1 (those with single isolate cultures; n = 110), group 2 (those with MUI and either symptomatic UTI or an underlying pathologic condition; n = 71) and group 3 (those with MUI and either surgically altered urinary passages or absence of UTI symptoms; n = 39). Nonculture laboratory data suggested UTI in 48.2% of patients in group 1, 46.5% in group 2, and 23.1% in group 3. Patients in groups 1 or 2 with cultures yielding isolate counts of 10(5) colony forming units/mL were 6.2 times more likely to be classified as having a UTI (by nonculture laboratory data) compared with patients having only one or more of these two criteria. This study proposes a more objective approach to interpretation of MUI cultures using the results of nonculture laboratory data, clinical profiles, and colony counts.