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Updated: Aug 23, 2026
A Murine Model of Group B Streptococcus Vaginal Colonization
Published on: November 16, 2016
[Susceptibility of vertically transmitted Group B streptococci to antimicrobial agents. Multicenter study]
Juan José González1, Antonia Andreu,
1Servicio de Microbiología, Hospital Vall d'Hebron, Barcelona, Spain.
Introduction:
To investigate the susceptibility of group B streptococci (GBS) to macrolides and lincosamides and assess alternatives for intrapartum chemoprophylaxis in women allergic to penicillin and colonized by a GBS strain resistant to these antibiotics.
Methods:
Multicenter study performed with 131 strains isolated between 1997-2002 from newborns diagnosed with early-onset GBS disease and 479 strains collected in 2002 from the vagina or rectum of pregnant women.
Results:
All the GBS (100%) were susceptible to penicillin, ampicillin, vancomycin, quinupristin/dalfopristin, levofloxacin and teicoplanin. Resistance rates were as follows: 12.45% to erythromycin and azithromycin, 11.80% to clindamycin, 11.31%, to josamycin, 1.80% to telithromycin and 0.32% to fosfomycin. Seventy-nine strains had a constitutive MLSB phenotype of resistance, 4 an inducible MLSB phenotype, 3 an M phenotype and 3 were resistant to clindamycin but susceptible to macrolides. The MIC for erythromycin and azithromycin was > 32 mg/L in more than 85% of GBS strains with a constitutive MLSB phenotype, from 0.5 to 4 mg/L in those with an inducible MLSB, and 4 mg/L in those with phenotype M. Fifty-one telithromycin-sensitive strains (all with a constitutive MLSB phenotype) showed induced resistance to telithromycin when erythromycin was present. No significant differences in antimicrobial resistance were found between GBS strains producing invasive neonatal disease and maternal isolates, or among strains from different geographic areas.
Conclusions:
The high rate of resistance to macrolides and lincosamides in our area makes susceptibility testing mandatory for GBS strains isolated from pregnant women allergic to penicillin.
Insights
Group B Streptococcus (GBS) shows high resistance to macrolides and lincosamides, necessitating susceptibility testing for pregnant women allergic to penicillin. Alternative antibiotics are crucial for intrapartum chemoprophylaxis in these cases.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Pharmacology
Background:
- Group B Streptococcus (GBS) is a leading cause of neonatal infections.
- Penicillin is the standard for intrapartum chemoprophylaxis, but allergies necessitate alternatives.
- Emerging resistance to macrolides and lincosamides complicates treatment options for penicillin-allergic pregnant women.
Purpose of the Study:
- To determine the susceptibility of GBS to macrolides and lincosamides.
- To evaluate alternative antibiotics for intrapartum chemoprophylaxis in penicillin-allergic, GBS-colonized women.
- To assess resistance patterns in GBS strains from neonatal infections and pregnant women.
Main Methods:
- A multicenter study analyzed 131 GBS strains from early-onset neonatal disease (1997-2002) and 479 maternal vaginal/rectal isolates (2002).
- Antimicrobial susceptibility testing was performed for various antibiotics, including macrolides, lincosamides, and alternatives.
- Phenotypic resistance (e.g., MLSB, M) and Minimum Inhibitory Concentrations (MICs) were determined.
Main Results:
- All GBS strains were susceptible to penicillin, ampicillin, vancomycin, and other tested agents.
- Significant resistance rates were observed: 12.45% to erythromycin/azithromycin, 11.80% to clindamycin, and 11.31% to josamycin.
- Constitutive MLSB phenotype was the most common resistance mechanism (79 strains), with high MICs for erythromycin and azithromycin.
- Induced resistance to telithromycin was observed in some strains with constitutive MLSB phenotype.
Conclusions:
- High rates of GBS resistance to macrolides and lincosamides were found.
- Susceptibility testing is mandatory for GBS strains from penicillin-allergic pregnant women.
- Alternative antibiotic strategies are needed for intrapartum chemoprophylaxis.
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