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

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.

Serotypes and Biochemical Reaction Patterns of Group B Streptococci / 대한임상병리학회지

BACKGROUND: This study is designed to provide data on the trend of serotypes of group B streptococci (GBS) isolated from clinical specimens during recent eight years and to elucidate the relationship between biochemical reactions and serotypes of GBS. METHODS: Serotyping, pigment production test, CAMP test, hippurate hydrolysis, and hemolysis test were performed for 150 GBS isolates from clinical specimens during March 1990 to February 1998. The typing sera used were Ia, Ib, II, III, IV, and V. Pigment production was detected by new Granada tube medium. The CAMP test and hippurate hydrolysis were performed by standard technique. Hemolytic patterns of GBS were determined on sheep blood agar and human blood agar plate. RESULTS: GBS were frequently isolated from cervix, urine, wound (pus), and blood. Striking increase of GBS isolates were notified from 1996 to 1997 period. Identification rates of GBS serotypes were Ib (38.0%), III (37.3%), Ia (9.3%), V (8.7%), nontypable strains (4.0%), and II (2.7%) in decreasing order. The proportion of serotype III increased markedly from 1996. Serotype V was not isolated until 1996, and ranked third in 1997. Seven (4.7%) isolates were nonhemolytic, and six of seven isolates revealed serotype III. Two (1.3%) isolates that were negative in both CAMP test and hippurate hydrolysis were serotype II. CONCLUSIONS: Clinical microbiology laboratories relying on beta hemolysis or pigment production for initial detection of GBS may underestimate the isolation rate of GBS and the proportion of serotype III which hardly makes hemolysis. It is therefore recommended that laboratories providing cultures for the GBS of genitalia specimens supplement other detection methods such as CAMP test or immunologic methods.