Dataset Information

Production of 2-aminophenoxazin-3-one by Staphylococcus aureus causes false-positive results in ?-galactosidase assays.

ABSTRACT: Staphylococcus aureus can be distinguished from similar coagulase-positive staphylococci by its absence of ?-galactosidase activity. This is commonly tested using o-nitrophenyl-?-D-galactopyranoside (ONPG) as the substrate. Unexpectedly, 111 and 58 of 123 isolates displayed apparent ?-galactosidase activity in the ONPG assay and on the Vitek 2 system, respectively. Compositional analysis showed that the yellow coloration of the positive ONPG assay resulted from production of 2-aminophenoxazin-3-one. Alternative ?-galactosidase substrates like X-Gal (5-bromo-4-chloro-3-indolyl-?-D-galactopyranoside) should be used for testing staphylococci.

SUBMITTER: Tse H

PROVIDER: S-EPMC3486264 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Production of 2-aminophenoxazin-3-one by Staphylococcus aureus causes false-positive results in β-galactosidase assays.

Tse Herman H Chan Elaine E Lam Ching-Wan CW Leung Ka-Fai KF Chow Pat P Lee Kim-Chung KC Sze Kong-Hung KH Cheung Stanley K K SK Tse Man-Kit MK Ho Pak-Leung PL Leung Sze-Pui SP Lau Susanna K P SK Woo Patrick C Y PC Yuen Kwok-Yung KY

Journal of clinical microbiology 20120912 11

Staphylococcus aureus can be distinguished from similar coagulase-positive staphylococci by its absence of β-galactosidase activity. This is commonly tested using o-nitrophenyl-β-D-galactopyranoside (ONPG) as the substrate. Unexpectedly, 111 and 58 of 123 isolates displayed apparent β-galactosidase activity in the ONPG assay and on the Vitek 2 system, respectively. Compositional analysis showed that the yellow coloration of the positive ONPG assay resulted from production of 2-aminophenoxazin-3- ...[more]

PMID: 22972831

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Project description:IntroductionEarly cancer detection can significantly improve patient outcomes and reduce mortality rates. Novel cancer screening approaches, including multi-cancer early detection tests, have been developed. Cost-utility analyses will be needed to examine their value, and these models require health state utilities. The purpose of this study was to estimate the disutility (i.e., decrease in health state utility) associated with false-positive cancer screening results.MethodsIn composite time trade-off interviews using a 1-year time horizon, UK general population participants valued 10 health state vignettes describing cancer screening with true-negative or false-positive results. Each false-positive vignette described a common diagnostic pathway following a false-positive result suggesting lung, colorectal, breast, or pancreatic cancer. Every pathway ended with a negative result (no cancer detected). The disutility of each false positive was calculated as the difference between the true-negative and each false-positive health state, and because of the 1-year time horizon, each disutility can be interpreted as a quality-adjusted life-year decrement associated with each type of false-positive experience.ResultsA total of 203 participants completed interviews (49.8% male; mean age = 42.0 years). The mean (SD) utility for the health state describing a true-negative result was 0.958 (0.065). Utilities for false-positive health states ranged from 0.847 (0.145) to 0.932 (0.059). Disutilities for false positives ranged from - 0.031 to - 0.111 (- 0.041 to - 0.111 for lung cancer; - 0.079 for colorectal cancer; - 0.031 to - 0.067 for breast cancer; - 0.048 to - 0.088 for pancreatic cancer).ConclusionAll false-positive results were associated with a disutility. Greater disutility was associated with more invasive follow-up diagnostic procedures, longer duration of uncertainty regarding the eventual diagnosis, and perceived severity of the suspected cancer type. Utility values estimated in this study would be useful for economic modeling examining the value of cancer screening procedures.

Dataset Information

Production of 2-aminophenoxazin-3-one by Staphylococcus aureus causes false-positive results in ?-galactosidase assays.

Publications

Production of 2-aminophenoxazin-3-one by Staphylococcus aureus causes false-positive results in β-galactosidase assays.

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