Comparison of BD GeneOhm real-time polymerase chain reaction with chromogenic and conventional culture methods for detection of group B Streptococcus in clinical samples.
A total of 200 antenatal high vaginal swabs were screened for the presence of group B Streptococcus (GBS) using a conventional culture method (recommended by Centers for Disease Control and Prevention). Screening was also performed by using a new chromogenic agar, chromID Strepto B, and by using the BD GeneOhm StrepB real-time polymerase chain reaction (PCR), which was performed directly on swabs without enrichment. Using a combination of all methods, we detected GBS in 101 samples. A total of 82 samples (81.2%) were positive using PCR, and 83 samples (82.2%) were confirmed as positive by culture (any method). PCR was more sensitive for detection of GBS than direct culture using any method (P < 0.0005). PCR was also more sensitive than any single enrichment method, but this difference was not statistically significant. With culture as a "gold standard", the PCR method showed a sensitivity of 77.1% and a positive predictive value of 79.3%. Of the culture-positive samples, significantly, more GBSs were detected by direct plating on chromID Strepto B than on selective sheep blood agar (67.5% versus 57% respectively, P < 0.02). After selective enrichment, 92.8% of GBS were isolated on chromID Strepto B compared with 89.2% isolated on sheep blood agar.
Smith
Dawn
D
Microbiology Department, Freeman Hospital, Newcastle-upon-Tyne NE7 7DN, UK.
Perry
John D
JD
Laine
Larissa
L
Galloway
Angela
A
Gould
F Kate
FK
D001431:Bacteriological Techniques / Q000379:methods*; D003470:Culture Media / Q000737:chemistry; D005260:Female; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D037841:Pregnant People; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis*; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000302:isolation & purification*; D014621:Vagina / Q000382:microbiology
D003470:Culture Media