Abstract
Objective. Our objective was to assess the ability of real-time PCR to predict in vitro resistance in isolates of group B streptococcus (GBS). Methods. The first real-time PCR assays for the genes known to confer resistance to erythromycin and clindamycin in GBS were developed. Three hundred and forty clinical GBS isolates were assessed with these assays and compared with conventional disk diffusion. Results. The presence of an erythromycin ribosome methylation gene (ermB or ermTR variant A) predicted in vitro constitutive or inducible resistance to clindamycin with a sensitivity of 93% (95% CI 86%–97%), specificity of 90% (95% CI 85%–93%), positive predictive value of 76% (95% CI 67%–84%), and negative predictive value of 97% (95% CI 94%–99%). Conclusion. This rapid and simple assay can predict in vitro susceptibility to clindamycin within two hours of isolation as opposed to 18–24 hours via disk diffusion. The assay might also be used to screen large numbers of batched isolates to establish the prevalence of resistance in a given area.
Highlights
Each year in the US 8000 neonatal cases of sepsis due to group B streptococcus (GBS) are reported [1]
Penicillin is the drug of choice for prophylaxis and treatment of GBS infection
The prevalence of resistance among invasive GBS isolates in the United States and Canada ranged from 7% to 25% for erythromycin and from 3% to 15% for clindamycin in reports published between 1998 and 2001
Summary
Each year in the US 8000 neonatal cases of sepsis due to GBS are reported [1]. Up to 30% of women carry GBS in the urogenital tract, intestinal tract, or both. Intrapartum antibiotic chemoprophylaxis remains the key to preventing neonatal disease. Penicillin is the drug of choice for prophylaxis and treatment of GBS infection. In patients allergic to penicillin, erythromycin and clindamycin are the commonly used alternatives. The proportions of GBS isolates with in vitro resistance to erythromycin and clindamycin have steadily increased since 1996 [2]. The prevalence of resistance among invasive GBS isolates in the United States and Canada ranged from 7% to 25% for erythromycin and from 3% to 15% for clindamycin in reports published between 1998 and 2001
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