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J. Clin. Microbiol. doi:10.1128/JCM.02036-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Rapid Antimicrobial Susceptibility Determination of Uropathogens in Clinical Urine Specimens Using ATP Bioluminescence

Vesna Ivani, Mitra Mastali, Neil Percy, Jeffrey Gornbein, Jane T. Babbitt, Yang Li, Elliot M. Landaw, David A. Bruckner, Bernard M. Churchill, and David A. Haake^*

Departments of Urology, Medicine, Biomathematics, Human Genetics, Pathology and Laboratory Medicine, Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095; Hygiena, Camarillo, CA 93012; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA 90073

^* To whom correspondence should be addressed. Email: dhaake{at}ucla.edu.

	Abstract

We describe the first direct testing of antimicrobial susceptibility of bacterial pathogens in human clinical fluid samples using ATP bioluminescence. We developed an ATP bioluminescence assay that eliminates somatic sources of ATP to selectively quantify the bacterial load in clinical urine specimens, with a sensitivity of <1000 colony forming units per milliliter. There was a log-log relationship between light emission and colony forming units in clinical urine specimens. A clinical study was performed to evaluate the accuracy of the ATP bioluminescence assay for determination of antimicrobial susceptibility of uropathogens in blinded clinical urine specimens. ATP bioluminescent bacterial density quantitation was used to determine the inoculation volume into growth medium with and without antibiotics. After incubation at 37°C for 120 minutes the ATP bioluminescent assay was repeated to evaluate the uropathogen response to antibiotics. The ability of the ATP bioluminescent assay to discriminate between antimicrobial susceptibility and resistance was determined by comparison with results obtained by standard clinical microbiology methods. Receiver operator characteristic curves were used to determine the optimal threshold for discriminating between susceptibility and resistance. Susceptibility and resistance was correctly predicted in 87% and 95% of cases, respectively, for an overall unweighted accuracy of 91%, when stratified by antibiotic. In susceptible samples, the accuracy improved to 95% when samples with less than 25-fold increase in bacterial ATP in the medium without antibiotics were excluded. These data indicate that a rapid bioluminescent antimicrobial susceptibility assay may be useful in the management of urinary tract infection.