title: Direct identification of Streptococcus agalactiae and capsular type by real-time PCR in vaginal swabs from pregnant women.
abstract: Most group B streptococcus (GBS) infections in newborns are with capsular type Ia, Ib, or III. To prevent these infections more effectively, we developed a real-time PCR method to simultaneously detect GBS species and identify these 3 capsular types in vaginal swab samples from women at 36-39 weeks of gestation. DNA to be detected included those of the dltS gene (encoding a histidine kinase specific to GBS) and cps genes encoding capsular types. PCR sensitivity was 10 CFU/well for a 33-35 threshold cycle. Results were obtained within 2 h. Direct PCR results were compared with results obtained from cultures. Samples numbering 1226 underwent PCR between September 2008 and August 2012. GBS positivity rates by direct PCR and after routine culture were 15.7% (n = 192) and 12.6% (n = 154), respectively. Sensitivity and specificity of direct PCR relative to culture were 96.1% and 95.9%. Of GBS positive samples identified by PCR, capsular types determined directly by real-time PCR were Ia (n = 24), Ib (n = 32), and III (n = 26). Real-time PCR using our designed cycling probe is a practical, highly sensitive method for identification of GBS in pregnant carriers, allowing use of prophylactic intrapartum antibiotics in time to cover the possibility of unexpected premature birth.
authors.affiliation: Department of Infectious Diseases, Keio University School of Medicine, 35 Shinano-machi, Shinjyuku-ku, Tokyo 160-8582, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Morozumi
authors.affiliation: Department of Infectious Diseases, Keio University School of Medicine, 35 Shinano-machi, Shinjyuku-ku, Tokyo 160-8582, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Chiba
authors.affiliation: Departments of Obstetrics and Gynecology, Juntendo University Shizuoka Hospital, 1129 Nagaoka Izunokunishi, Shizuoka 410-2295, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Igarashi
authors.affiliation: Departments of Obstetrics and Gynecology, Juntendo University Shizuoka Hospital, 1129 Nagaoka Izunokunishi, Shizuoka 410-2295, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Mitsuhashi
authors.affiliation: Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and, Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Takeaki
authors.initials: T
authors.lastname: Wajima
authors.affiliation: Department of Infectious Diseases, Keio University School of Medicine, 35 Shinano-machi, Shinjyuku-ku, Tokyo 160-8582, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Iwata
authors.affiliation: Department of Infectious Diseases, Keio University School of Medicine, 35 Shinano-machi, Shinjyuku-ku, Tokyo 160-8582, Japan. Electronic address: ubukatak@a6.keio.jp.
authors.forename: Kimiko
authors.initials: K
authors.lastname: Ubukata
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008875:Middle Aged; D058889:Molecular Typing / Q000379:methods; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis / Q000382:microbiology*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000235:genetics*; D014621:Vagina / Q000382:microbiology*; D055815:Young Adult
keywords: Capsular type; Pregnant women; Real-time PCR; Streptococcus agalactiae