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Journal of Clinical Microbiology, August 2008, p. 2745-2750, Vol. 46, No. 8
0095-1137/08/$08.00+0     doi:10.1128/JCM.00189-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Use of Phenotypic and Molecular Serotype Identification Methods To Characterize Previously Nonserotypeable Group B Streptococci{triangledown}

Fanrong Kong,1 Lotte Munch Lambertsen,2 Hans-Christian Slotved,2 Danny Ko,1 Hui Wang,1,3 and Gwendolyn L. Gilbert1*

Centre for Infectious Diseases and Microbiology (CIDM), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead, New South Wales, Australia,1 Neisseria & Streptococci Reference Laboratory, Department of Bacteriology, Mycology & Parasitology, Division of Microbiology & Diagnostics, Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark,2 Research Laboratory for Infectious Skin Diseases, Department of Dermatology, Wuhan First Hospital, Wuhan, Hubei Province, People's Republic of China3

Received 30 January 2008/ Returned for modification 11 April 2008/ Accepted 10 June 2008

Among 1,762 isolates of Streptococcus agalactiae (group B streptococcus [GBS]), 207 (12%) initially nonserotypeable isolates were tested by improved conventional serotyping methods (Lancefield antigen extraction with 0.1 and 0.2 N HCl, latex agglutination assays, and use of antisera against all known serotypes [Ia, Ib, and II to IX]) and a molecular serotype identification system (multiplex PCR-based reverse line blot [mPCR/RLB] assays targeting serotype-specific sites in the region spanning cpsH to cpsM). Serotypes were assigned to 71 (34%) of the 207 isolates by using antisera and to 204 (98.5%) of them by mPCR/RLB. Sequencing of a portion of the cpsE-cpsF-cpsG region of 141 persistently nonserotypeable isolates and 1 with discrepant conventional and molecular serotyping results was attempted. Major mutations were identified in 34 isolates (24%), including 11 (8%) from which no amplicons were obtained and 23 (16%) with sequence variation compared with published sequences; of the latter, 21 (15%) were associated with amino acid changes. By contrast, mutations were identified in only 12 (2.3%) of 516 serotypeable isolates for which this region has been sequenced previously. In summary, an improved serotyping scheme allowed serotype identification of more than one-third of the previously nonserotypeable GBS isolates. Molecular serotypes were assigned to almost all of the isolates by mPCR/RLB. Significant mutations (with no amplicons or with associated amino acid changes) were found in the cpsE-cpsF-cspG region of a higher proportion of nonserotypeable than of serotypeable isolates (32/141 versus 8/516; P < 0.001), but further investigation is needed to determine the genetic basis for most nonserotypeable GBS isolates.

* Corresponding author. Mailing address: Centre for Infectious Diseases and Microbiology (CIDM), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Darcy Road, Westmead, New South Wales 2145, Australia. Phone: (612) 9845 6255. Fax: (612) 9893 8659. E-mail: l.gilbert{at}usyd.edu.au

{triangledown} Published ahead of print on 18 June 2008.

Journal of Clinical Microbiology, August 2008, p. 2745-2750, Vol. 46, No. 8
0095-1137/08/$08.00+0     doi:10.1128/JCM.00189-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Ulett, K. B., Benjamin, W. H. Jr., Zhuo, F., Xiao, M., Kong, F., Gilbert, G. L., Schembri, M. A., Ulett, G. C. (2009). Diversity of Group B Streptococcus Serotypes Causing Urinary Tract Infection in Adults. J. Clin. Microbiol. 47: 2055-2060 [Abstract] [Full Text]  


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