Serotypes and Biochemical Reaction Patterns of Group B Streptococci

Uh, Young; Jang, In Ho; Hwang, Gyu Yel; Yoon, Kap Jun

Abstract

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.