The Significance of Polymicrobial Growth in Urine: Contamination or True Infection

Abstract

Urine growing more than one organism is usually considered contaminated. During 1980-1984, among 198 episodes of urosepsis with at least one identical organism in blood and urine, there were 62 with polymicrobial growth from urine. The significance of the multiple growth from urine was confirmed in 12 episodes by the growth of more than one identical organism in blood and urine and in 21 episodes by repeated growth of the same mixture of organisms in multiple urine specimens. Escherichia coli had a higher tendency to invade blood stream than other Gram-negative organisms, such as pseudomonas and proteus. In specific populations with high risk of polymicrobial infection, multiple growth in urine should be carefully evaluated with appropriate colony count and identification of each isolate.

Limited vs full microbiological investigation for the management of symptomatic polymicrobial urinary tract infection in adult spinal cord-injured patients

“…However, polymicrobial urine cultures can sometimes represent a true infection as demonstrated by the simultaneous growth of 51 identical organisms in blood and urine cultures from patients with urosepsis 13 or by the repeated growth of the same mixture of organisms in multiple urine specimens. 7 Our ®ndings support the notion that polymicrobial growth in urine cultures obtained from symptomatic SCI patients can be clinically meaningful. The results of this study may apply to other types of patients who are dependent on bladder catheterization, such as stroke victims, elderly subjects, and nursing home residents.…”

“…For instance, almost half of positive urine cultures from SCI patients with clinical UTI in our institution were observed to grow 52 organisms in urine cultures; this ®nding is usually referred to as polymicrobial symptomatic UTI, although not all cultured organisms may contribute to signs and symptoms of UTI. There is no established way to accurately identify which cultured organism(s) is/are responsible for the particular clinical episode of polymicrobial UTI, 7 thereby impairing the ability to administer antibiotic therapy directed against only the pathogenic organism(s). As a result, physicians generally request that clinical microbiology laboratories identify and perform antibiotic susceptibility on most, if not all, organisms isolated from urine cultures in patients with polymicrobial UTI.…”

Gram-Positive Uropathogens, Polymicrobial Urinary Tract Infection, and the Emerging Microbiota of the Urinary Tract

“…There are multiple cited cases of polymicrobial bloodstream infection with identical organisms present in both urine and blood cultures [for examples see [312–314]]. In these cases, polymicrobial bloodstream infection supports the interpretation of polymicrobial UTI, especially when multiple of the organisms identified in the blood are also identified in urine.…”

Applications of Flow Cytometry to Clinical Microbiology

“…At the same time, it is possible to perform qualitative and quantitative analyses of samples. Thus, FCM is a suitable technique for the study of heterogeneous populations (68,186) under circumstances of infections due to the presence of multiple microorganisms (292) or for the study of the effects of treating microorganisms with antimicrobial agents (119,309,330), since each particle is analyzed individually. As stated above, its main advantages are simplicity, reliability, speed, and the possibility of detecting simultaneous infections.…”