This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Friedman, M P Articles by Freeman, T R Search for Related Content PubMed PubMed Citation Articles by Friedman, M P Articles by Freeman, T R

Rapid isolation and presumptive diagnosis of uropathogens by using membrane filtration and differential media.

Department of Microbiology, Our Lady of Lourdes Hospital, Camden, New Jersey.

ABSTRACT

Random urine samples from hospitalized patients (n = 550) and seeded sterile filtered urine samples (n = 730) were used to test a membrane filtration technique, Qualture (Future Medical Technologies International, Inc., West Palm Beach, Fla.), for the detection and identification of uropathogens. Results for each sample were compared with those obtained by the calibrated loop (0.01 ml) method to demonstrate the sensitivity of the method as a screening tool and the specificity of the presumptive diagnosis obtained from the pattern of growth on differential media. The medium was supplied as dehydrated nutrient pads (Sartorius AG, Goettingen, Germany) and was activated by rehydration by the addition of the liquid specimen. With a threshold of 10(4) CFU/ml defining a positive culture, the sensitivity of the Qualture was 100%. At lower levels of bacteriuria, the Qualture was more sensitive than the calibrated loop method. Significant infections were presumptively diagnosed at 4 h by filtration rather than at 24 h on agar medium. The specificity of uropathogen identification ranged from 99% for Enterococcus spp. to 83% for Pseudomonas spp. Citrobacter spp. could not be differentiated from Escherichia coli and Providencia spp. could not be differentiated from Proteus spp., which does not create a therapeutic dilemma. Filtration, isolation, quantitation, and presumptive diagnosis are performed in one step, without subculture. Membrane filtration is a sensitive and rapid technique, with the advantage that it can be used as a collection and transport device without the use of growth inhibitors.