Rapid culture based detection of Streptococcus agalactiae on vaginal/rectal swabs
Abstract number: R2395
Tritten M.L., Siegrist H.H., Jacquet A., Lienhard R.
Objectives: To develop and test a rapid method based on direct agglutination of a selective Todd-Hewitt broth to detect group B streptococci (GBS) on routine vaginal and/or rectal swabs obtained for perinatal screening.
Methods: A total of 447 swabs for the detection of GBS were cultivated in Todd-Hewitt + antibiotics enrichment broth overnight at 35°C. The next day 2 drops (100ul) of the broth were extracted and a direct latex agglutination (Streptex®, Remel Inc.) was performed for the detection of Lancefield group A, B, C, D, F and G streptococci. On the same broth, subcultures at 35°C overnight were made on sheep blood agar (n = 447) and chromogenic agar plates (STREPTO B ID® bioMérieux, n = 168) to search for GBS. Agglutination was then used again to identify all types of colonies.
Results: Overall, direct agglutination gave 81 broths (18.1%) positive for a group B streptococcus. Subcultures confirmed GBS in 80 (98.7%) of the samples, only 1 colony type could not be identified on sheep blood agar after 24 hours. Out of the 366 broths presenting none or other streptococcal groups on direct agglutination, only 1 presented a GBS after subculture on sheep blood and chromogenic agar.
Conclusion: Direct agglutination of the Todd-Hewitt + antibiotics enrichment broth containing vaginal/rectal swabs offers a rapid (within 24 hours), sensitive and specific method for the detection of GBS colonisation in perinatal screening. This cost-effective procedure can easily be performed in any clinical microbiology laboratory.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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