TY - JOUR
T1 - Use of phenotypic and molecular serotype identification methods to characterize previously nonserotypeable group B streptococci
AU - Kong, Fanrong
AU - Lambertsen, Lotte Munch
AU - Slotved, Hans Christian
AU - Ko, Danny
AU - Wang, Hui
AU - Gilbert, Gwendolyn L.
PY - 2008/8
Y1 - 2008/8
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=53149147462&partnerID=8YFLogxK
U2 - 10.1128/JCM.00189-08
DO - 10.1128/JCM.00189-08
M3 - Journal article
C2 - 18562579
AN - SCOPUS:53149147462
SN - 0095-1137
VL - 46
SP - 2745
EP - 2750
JO - Journal of Clinical Microbiology
JF - Journal of Clinical Microbiology
IS - 8
ER -