Group B streptococcal colonization in elderly women.

Baldan, Rossella; Droz, Sara; Casanova, Carlo; Knabben, Laura; Huang, Dorothy J; Brülisauer, Christine; Kind, André B; Krause, Elke; Mauerer, Stefanie; Spellerberg, Barbara; Sendi, Parham (2021). Group B streptococcal colonization in elderly women. BMC infectious diseases, 21(1), p. 408. BioMed Central 10.1186/s12879-021-06102-x

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In 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.


GBS 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).


The 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.


Our findings indicate a similar colonization rate for pregnant and elderly women.


Current Controlled Trial ISRCTN15468519 ; 06/01/2017.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Service Sector > Institute for Infectious Diseases > Research
04 Faculty of Medicine > Service Sector > Institute for Infectious Diseases
04 Faculty of Medicine > Department of Gynaecology, Paediatrics and Endocrinology (DFKE) > Clinic of Gynaecology
04 Faculty of Medicine > Service Sector > Institute for Infectious Diseases > General Bacteriology
04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Clinic of Infectiology

UniBE Contributor:

Baldan, Rossella, Droz, Sara Christine, Casanova, Carlo, Knabben, Laura Michelle Tatjana, Brülisauer, Christine, Krause, Elke, Sendi, Parham


500 Science > 570 Life sciences; biology
600 Technology > 610 Medicine & health




BioMed Central




Andrea Stettler

Date Deposited:

25 Jun 2021 17:04

Last Modified:

05 Dec 2022 15:51

Publisher DOI:


PubMed ID:


Uncontrolled Keywords:

Colonization Elderly women Group B Streptococcus Postmenopausal women Streptococcus agalactiae




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