Rapid detection of the "highly virulent" group B Streptococcus ST-17 clone.
Group B streptococcus (GBS) is a leading cause of neonatal morbidity and mortality. Multilocus sequence typing (MLST) revealed that the sequence type ST-17 defines a "highly virulent" serotype III clone strongly associated with neonatal invasive infections. Our aim was to identify a target sequence enabling rapid, simple, and specific detection of this clone by a real-time PCR assay. Conventional methods for DNA manipulation and gene analyses were used to characterize the gbs2018 gene variant specific for ST-17 clone and to design ST-17- and GBS-specific primers. Conventional and real-time PCR assays were developed to detect GBS and ST-17 clones in bacterial cultures and directly on clinical samples. One hundred and fifty-six French GBS strains from various geographical areas in France isolated between 1990 and 2005 were screened by PCR with ST-17-specific primers. Forty strains were positive, and all were validated by MLST as ST-17. A representative sampling of 49 ST-17-PCR-negative strains was confirmed by MLST as non-ST-17. Real-time PCR was further used to directly test 85 vaginal samples. Among these, 13 were GBS-positive, and one was identified as ST-17. The association between strain invasiveness and ST-17 lineage in neonates with late onset disease was highly significant: 78% (P<0.0001) of strains isolated were ST-17. In conclusion, an ST-17-specific gbs2018 allele was identified and used to develop a sensitive and specific rapid-screening molecular assay for identifying ST-17 "highly virulent" GBS. Using this technique, accurate identification of women and neonates colonized by ST-17 can be readily achieved within less than 2 h.
Lamy
Marie-Cécile
MC
Laboratoire de Recherche de Bactériologie, Université Paris 5, Faculté de Médecine René Descartes-Site Cochin, 24 rue du Faubourg Saint Jacques, Paris, France.
Dramsi
Shaynoor
S
Billoët
Annick
A
Réglier-Poupet
Hélène
H
Tazi
Asmaa
A
Raymond
Josette
J
Guérin
François
F
Couvé
Elisabeth
E
Kunst
Frank
F
Glaser
Philippe
P
Trieu-Cuot
Patrick
P
Poyart
Claire
C
D000328:Adult; D002648:Child; D002675:Child, Preschool; D017931:DNA Primers; D005260:Female; D005798:Genes, Bacterial; D014644:Genetic Variation; D006801:Humans; D007231:Infant, Newborn; D016133:Polymerase Chain Reaction / Q000379:methods*; D011247:Pregnancy; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity
D017931:DNA Primers