Usefulness of a Disk Method for Detection of Hippurate Hydrolysis by Campylobacter jejuni

Uh, Young; Park, Soon Duk; Cho, Hyun Mi; Lee, Hyeun Gyeo; Jeoung, An Suk; Lee, Mi Kyung; Yoon, Kap Jun

Abstract

BACKGROUND: The test for hippurate hydrolysis is critical for differentiation of C. jejuni and other thermophilic Campylobacter species. So, we evaluated the disk method for detection of hippurate hydrolysis by C. jejuni.
METHODS
Twenty-eight Campylobacter species isolated from stool culture were simultaneously tested with disk method for detection of hippurate hydrolysis and polymerase chain reaction (PCR) for hippuricase specific gene. Disk method was tested with difference in incubation time (2 hours vs. 4 hours), hippurate concentration (1%, 2%, and 4%), amount of ninhydrin (50 microliter vs. 100 microliter), and inoculation method (colony vs. suspension of organism adjusted by turbidity), finally, 24 types of disk methods were performed.
RESULTS
By using hippuricase PCR method as the reference for the detection of hippurate hydrolysis, the disk method showed a sensitivity of 91.7% and a specificity of 100% when two kinds of disk methods were simultaneously performed.
CONCLUSIONS
The disk method for detection of hippurate hydrolysis is simple to use and require fewer cells than the tube method do, and should be useful as a routine diagnostic test in clinical laboratory for rapid identification of C. jejuni.