Nosocomial Bacteriuria: A Prospective Study of Case Clustering and Antimicrobial Resistance

Abstract

The role of cross-infection in nonepidemic nosocomial bacteriuria in a large, university-afflilated hospital was investigated. In adult patients admitted over an 11 wk period, all infective organisms of the same genus, species and antimicrobial susceptibility were identified and clustered by date of onset and hospital ward. Further laboratory studies were conducted to verify clustering. Among the 3452 patients studied, 194 cases of nosocomial bacteriuria were identified; 49 appeared clustered by epidemiologic evidence. Additional laboratory tests verified clustering in 30 cases (15.5%). In 90% of the clustered and 76% of the nonclustered cases, previous urinary catheterization had been performed; Pseudomonas aeruginosa, Serratia marcescens and Citrobacter freundii often caused clustered infection, while Escherichia coli predominated in nonclustered cases. Resistance to gentamicin, sulfathiazole and carbenicillin was significantly greater for pathogens from clustered cases than for nonclustered ones. This increased resistance emphasizes the need to prevent cross-infection, even in the absence of epidemics.