Flow-cytometric assay to detect group B streptococci in vaginal swabs

Abstract number: 1733_652

Zabel L., Anliker M., Nuding S., Müller H.

Objectives: Group B streptococci (GBS) are the leading cause of neonatal sepsis in the USA and appear to be a growing problem world-wide. The CDC guidelines and the German AWMF guidelines recommend screening pregnant women for GBS. Collection of cultures between 35 and 37 weeks gestation is recommended to improve the sensitivity and specificity of detection of women who remain colonised at the time of delivery. Women at risk should receive antibiotic prophylaxis during delivery. The screening-cultures from vaginal swabs require at least two days for culture and identification. Unfortunately many women are hospitalised for delivery, when the woman is already in labour and a screening result is not available by the time.

Methods: Using flow-cytometry and a monoclonal mouse antibody (C55560M Dunn laboratories, Germany) directed against GBS an assay was established, which detected GBS from liquid cultures (Todd Hewitt broth) of vaginal swabs after a short incubation time of 90 min. Results were received within 2.5 hours. The assay was applied to 121 vaginal swabs of women selected independent of diagnosis or hospitalisation and compared to conventional culture methods.

Results: The detection limit was determined to be approximately 1.88×103 cfu/mL, using serial dilutions of the reference strain Streptococcus agalactiae ATCC 13813.

A total of 15 (12.4%) were identified as carriers of BGS by both, culture and flow-cytometry. Taking only the culture into account, 18 (14.9%) of the vaginal specimens were positive for GBS. Flow-cytometric analysis showed a more increased positivity rate with 44 (36.4%) GBS-positive specimens.

Conclusion: The flow-cytometric assay provided physicians with results within 2–3 hours and was more sensitive than conventional culture. It therefore may be used to detect GBS in sufficient time, even if the patient is already in labour.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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