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Background <p>Group B streptococcus (GBS) is a commensal bacterium that can cause severe infection in neonates. Vaginal colonization with GBS is a risk factor for mother-to-child transmission and, therefore, its monitoring is essential for prevention strategies. Epidemiological data on maternal GBS carriage and the characterization of recovered isolates in North African regions are scarce, mainly due to the lack of systematic GBS screening in pregnant women. Maternal vaccination based on the use of various capsular polysaccharides (CPS) remains a promising strategy for the control of GBS infection. Therefore, studying the distribution of CPS is of paramount importance to ensure vaccine efficacy in diverse and large populations. This investigation aims to provide the first large-scale epidemiological analysis in pregnant women in Morocco, regarding prevalence of GBS carriage and the main characteristics of circulating strains.</p> Methods <p>GBS screening was conducted between April 2021 and July 2024 on 1710 pregnant women at 35–40 weeks of gestation. Capsular serotyping was performed using multiplex PCR. Disk diffusion test was applied to evaluate antimicrobial susceptibility. Resistance genes and key virulence genes were detected by PCRs.</p> Results <p>The prevalence of colonization was 9.9%. The serotypes Ib, IV, II, V, Ia, and III were more prevalent, accounting for 19.8%, 17.1%, 14.3%, 13.7%, 12.3%, and 7.5% respectively. All GBS isolates were found to be susceptible to penicillin. Resistance to tetracycline was observed in 98.8% of strains, with a significant correlation to the presence of <i>tetM</i> gene. 6.4% of isolates were clindamycin resistant and 14.1% were erythromycin resistant, with a significant correlation to the <i>ermB</i> gene. In addition, <i>mefA</i> gene was detected in 16.6% of erythromycin-resistant isolates. Regarding virulence genes, <i>scpB</i> was present in all tested isolates and <i>bac</i>,<i> fbsA</i>, and <i>cyIB</i> were found in more than 70.0% of tested isolates, whereas <i>rib</i> gene was detected in 37.5% of tested isolates.</p> Conclusion <p>The serotype distribution indicates that a candidate vaccine based on hexavalent capsular polysaccharides (Ia, Ib, II, III, IV, and V) would prevent 85.0% of cases. Resistance to macrolides (erythromycin 14.1%) and lincosamides (clindamycin 6.4%), which are used as alternative therapies, was observed in a total of 20.5% of strains. This highlights the need for sustained epidemiological surveillance of GBS in the region.</p> Trial registration <p>Clinical trial number: not applicable.</p>

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A large prospective study of group B Streptococcus carriage in pregnant women in Morocco: prevalence, serotype distribution, antimicrobial resistance and virulence determinants

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月2日

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  • Hanane Ben-Taleb,
  • Narjis Amar,
  • Azeddine Chakroun,
  • Kaotar Nayme,
  • Amine Lamrissi,
  • Amal Badre,
  • Karima Mohtadi,
  • Rosalie Sacheli,
  • Rajae Darfouf,
  • Cécile Meex,
  • Pierre Bogaerts,
  • Te-Din Huang,
  • Halima Lebrazi,
  • Rachid Saïle,
  • Mustapha Chamekh

摘要

Background

Group B streptococcus (GBS) is a commensal bacterium that can cause severe infection in neonates. Vaginal colonization with GBS is a risk factor for mother-to-child transmission and, therefore, its monitoring is essential for prevention strategies. Epidemiological data on maternal GBS carriage and the characterization of recovered isolates in North African regions are scarce, mainly due to the lack of systematic GBS screening in pregnant women. Maternal vaccination based on the use of various capsular polysaccharides (CPS) remains a promising strategy for the control of GBS infection. Therefore, studying the distribution of CPS is of paramount importance to ensure vaccine efficacy in diverse and large populations. This investigation aims to provide the first large-scale epidemiological analysis in pregnant women in Morocco, regarding prevalence of GBS carriage and the main characteristics of circulating strains.

Methods

GBS screening was conducted between April 2021 and July 2024 on 1710 pregnant women at 35–40 weeks of gestation. Capsular serotyping was performed using multiplex PCR. Disk diffusion test was applied to evaluate antimicrobial susceptibility. Resistance genes and key virulence genes were detected by PCRs.

Results

The prevalence of colonization was 9.9%. The serotypes Ib, IV, II, V, Ia, and III were more prevalent, accounting for 19.8%, 17.1%, 14.3%, 13.7%, 12.3%, and 7.5% respectively. All GBS isolates were found to be susceptible to penicillin. Resistance to tetracycline was observed in 98.8% of strains, with a significant correlation to the presence of tetM gene. 6.4% of isolates were clindamycin resistant and 14.1% were erythromycin resistant, with a significant correlation to the ermB gene. In addition, mefA gene was detected in 16.6% of erythromycin-resistant isolates. Regarding virulence genes, scpB was present in all tested isolates and bac, fbsA, and cyIB were found in more than 70.0% of tested isolates, whereas rib gene was detected in 37.5% of tested isolates.

Conclusion

The serotype distribution indicates that a candidate vaccine based on hexavalent capsular polysaccharides (Ia, Ib, II, III, IV, and V) would prevent 85.0% of cases. Resistance to macrolides (erythromycin 14.1%) and lincosamides (clindamycin 6.4%), which are used as alternative therapies, was observed in a total of 20.5% of strains. This highlights the need for sustained epidemiological surveillance of GBS in the region.

Trial registration

Clinical trial number: not applicable.