ASSESSMENT OF 2 METHODS FOR RAPID INTRAPARTUM DETECTION OF VAGINAL GROUP-B STREPTOCOCCAL COLONIZATION

Aims-To compare two methods for the rapid detection of intrapartum vag inal carriage of group B streptococci (Streptococcus agalactiae) with standard culture techniques and to establish their suitability for rou tine use. Methods-Vaginal swabs from 266 patients in labour were incub ated in glucose broth in an anaerobic atmosphere for four to six hours . The Wellcogen Strep B latex particle agglutination test kit was subs equently used for antigen detection. In the second part of the study s wabs from 117 women were assessed for the presence of group B streptoc occi using the ICON STREP B immunoconcentration assay (Hybritech). Bot h methods were compared with standard semiquantitative culture on Colu mbia horse blood agar and Islam's medium. Results-In the first study v aginal carriage of group B streptococci was shown in 38 of 266 (14.3%) patients by culture. Latex particle agglutination with the Wellcogen kit detected 30 of these positive results (sensitivity 78.9%, specific ity 100%). In those patients with moderate to heavy colonisation (> 10 (4) colony forming units per millilitre) antigen was detected in all ( 26/26) culture positive patients (sensitivity 100%, specificity 100%). In the second study 16 (13.7%) patients were culture positive. The IC ON test detected 11 positive results (sensitivity 68.8%, specificity 1 00%) and for heavy colonisation (10(5) cfu/ml) detected nine of nine c ases (sensitivity 100%, specificity 100%). The ICON test took 10 to 15 minutes to perform. Conclusion-These tests are potentially useful for the rapid detection of group B streptococci vaginal colonisation in l abour, particularly heavy colonisation. Both tests are insufficiently sensitive to replace standard culture methods.