The microbiology of bacteriuria in men: a 5-year study at a Veterans' Affairs hospital

Bacteriuria and urinary tract infection occur relatively frequently in older men, but data regarding the causative microorganisms are limited. We retrospectively identified all positive cultures of urine specimens (n = 4943) obtained over a 5-year period at our institution. We determined the frequency of causative microorganisms and grouped these by Gram type, setting of patient care, and method of urine specimen collection. We also assessed the performance characteristics of the Gram-stained smear of uncentrifuged urine. Among our patients, Gram-positive cocci (GPC) were isolated as often as Gram-negative rods (GNR). Escherichia coli was the single or predominant isolate in only 14% of cases, and Enterococcus was the single most commonly identified genus (22.5%). The Gram stain was accurate in predicting the culture results (positive likelihood ratio, 7.0 for GPC and 8.1 for GNR). We conclude that the microorganisms causing bacteriuria in older male veterans are substantially different from those found in women, and the Gram-stained smear provides useful information on the causative organisms.