Group B streptococcal colonization in elderly women

Rossella Baldan,Parham Sendi,Barbara Spellerberg,Laura Knabben,Dorothy J Huang,André B Kind,Stefanie Mauerer,Carlo Casanova,Elke Krause,Sara Droz,Christine Brülisauer

doi:10.1186/s12879-021-06102-x

Abstract

BackgroundIn non-pregnant adults, the incidence of invasive Group B Streptococcus (GBS) disease is continuously increasing. Elderly and immunocompromised persons are at increased risk of infection. GBS commonly colonizes the vaginal tract, though data on colonization in the elderly are scarce. It is unknown whether the prevalence of GBS colonization is increasing in parallel to the observed rise of invasive infection. We conducted a three-year (2017–2019) prospective observational cross-sectional study in two teaching hospitals in Switzerland to determine the rate of GBS vaginal colonization in women over 60 years and i) to compare the proportions of known risk factors associated with invasive GBS diseases in colonized versus non-colonized women and ii) to evaluate the presence of GBS clusters with specific phenotypic and genotypic patterns in this population.MethodsGBS screening was performed by using vaginal swabs collected during routine examination from women willing to participate in the study and to complete a questionnaire for risk factors. Isolates were characterized for antibiotic resistance profile, serotype and sequence type (ST).ResultsThe GBS positivity rate in the elderly was 17% (44/255 positive samples), and similar to the one previously reported in pregnant women (around 20%). We could not find any association between participants’ characteristics, previously published risk factors and GBS colonization. All strains were susceptible to penicillin, 22% (8/36) were not susceptible to erythromycin, 14% (5/36) were not susceptible to clindamycin and 8% (3/36) showed inducible clindamycin resistance. Both M and L phenotypes were each detected in one isolate. The most prevalent serotypes were III (33%, 12/36) and V (31%, 11/36). ST1 and ST19 accounted for 11% of isolates each (4/36); ST175 for 8% (3/36); and ST23, ST249 and ST297 for 6% each (2/36). Significantly higher rates of resistance to macrolides and clindamycin were associated with the ST1 genetic background of ST1.ConclusionsOur findings indicate a similar colonization rate for pregnant and elderly women.Trial registrationCurrent Controlled Trial ISRCTN15468519; 06/01/2017

Highlights

In non-pregnant adults, the incidence of invasive Group B Streptococcus (GBS) disease is continuously increasing
Our study showed a prevalence of GBS colonization of 17% in postmenopausal women, similar to that reported by Moltó-Garcia et al (17.8%) in Spain [25]
The observed increase in invasive GBS infections in elderly women may be for reasons other than the colonization rate

Summary

Introduction

In non-pregnant adults, the incidence of invasive Group B Streptococcus (GBS) disease is continuously increasing. GBS commonly colonizes the vaginal tract, though data on colonization in the elderly are scarce It is unknown whether the prevalence of GBS colonization is increasing in parallel to the observed rise of invasive infection. A Danish study showed that from 2005 to 2018, the incidence of invasive GBS in adults aged 65–74 years increased from 3.23 to 8.34 per 100,000, and in adults over 75 years from 6.85 to 16.01 per 100,000 [7] Their finding aligns with data from Iceland, Finland, Norway, England and Wales, Canada, and other countries [8,9,10,11,12]. Little is known about the GBS colonization rate in women older than 60 years of age The site of GBS colonization could potentially be the source of invasive infection, underscoring the importance to investigating the colonization rate in this patient population

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