DNA Probe for Beta-Hemolytic Group B Streptococcus: Diagnostic Accuracy in Threatened Preterm Labor

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Objective: To determine the diagnostic accuracy of a DNA probe for beta-hemolytic group B Streptococcus (GBS) in women with threatened preterm labor.

Study Design: Two identical vaginal/perianal samples were collected from 75 pregnant women who were being evaluated for threatened preterm labor. One sample was managed in the traditional manner, with direct plating onto blood agar followed by plating after 8 and 24 hours of LIM broth enhancement. The "gold standard" was 24 hours of LIM broth enhancement followed by blood agar plating. The second sample was placed in LIM broth, and DNA probe testing was performed after incubation for 8 and 24 hours.

Results: The prevalence of GBS colonization by the gold standard culture was 32%. After 8 hours of incubation in LIM broth, the DNA probe had poor sensitivity (79%); however, after 24 hours of incubation in LIM broth the DNA probe sensitivity rose to 96%. The DNA probe demonstrated only one false negative result after 24 hours of LIM broth enhancement. All DNA probe results were known 25 hours after sample collection.

Conclusion: This DNA probe gave results nearly identical to those of standard cultures and allowed a substantial saving of time.

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