CHROMagar™ StrepB Kit

For the Isolation and Differentiation of Group B Streptococcus (Streptococcus agalactiae)

CHROMagar™ StrepB is a selective chromogenic culture medium specifically developed for the detection of Group B Streptococcus (GBS), also known as Streptococcus agalactiae, from clinical specimens such as vaginal, rectal, vagino-rectal swabs, and urine. On this medium, GBS colonies appear mauve, while other microorganisms are typically blue, colorless, or inhibited, offering clear visual differentiation.

This medium supports the growth of both hemolytic and non-hemolytic GBS strains, allowing for accurate and rapid screening of GBS colonization in pregnant women and aiding in the implementation of intrapartum antibiotic prophylaxis to prevent neonatal infections.

Colony Appearance

• Group B Streptococcus (GBS): Mauve
• Other microorganisms: Blue, colorless, or inhibited

Performance

Streptococcus agalactiae is a leading cause of early-onset neonatal sepsis, pneumonia, and meningitis. Studies show that 12–27% of pregnant women are colonized with GBS. Transmission to newborns typically occurs during childbirth. To prevent this, many international guidelines recommend prenatal screening for GBS between weeks 35–37 of gestation.

CHROMagar™ StrepB enables reliable, visual detection of GBS, including non-hemolytic strains that may be missed on blood agar or other conventional media. It offers high sensitivity and specificity, helping clinicians identify carriers quickly and confidently.

Intended Use

CHROMagar™ StrepB is intended for:

• Qualitative detection of Group B Streptococcus colonization in pregnant women
• Screening from:
  • Vaginal swabs
  • Vagino-rectal swabs
  • Urine samples
  • Direct or post-enrichment cultures (e.g., from LIM broth)

The medium supports aerobic incubation, eliminating the need for CO₂ supplementation. Confirmatory testing (e.g., latex agglutination) can be done directly from suspect colonies.

Note: CHROMagar™ StrepB is not intended to diagnose infections or guide treatment. Confirmatory testing and further identification are recommended.

Advantages

1. Easy Interpretation
   Mauve coloration allows rapid visual identification of GBS colonies, reducing interpretation errors in mixed flora.
2. High Sensitivity
   Detects both hemolytic and non-hemolytic GBS, ensuring no clinically relevant strain is missed.
3. High Specificity
   Suppresses growth of competing flora, reducing false positives and the need for additional confirmatory tests.
4. Rapid Results
   Colonies can be interpreted after 18–24 hours of incubation.
5. Simple Workflow
   Aerobic incubation—no CO₂ atmosphere required. Compatible with confirmatory identification via latex agglutination or MALDI-TOF.

Test Procedure

1. Collect vaginal, rectal, or urine samples from pregnant women.
2. Inoculate the sample directly or after enrichment (e.g., in LIM broth) onto CHROMagar™ StrepB.
3. Incubate the plate at 35–37 °C for 18–24 hours under aerobic conditions.
4. Interpret colonies:
   • Mauve = presumptive GBS
   • Blue/colorless = other flora

Ordering Information

Each pack includes:

• Base medium
• Supplements S1 and S2

Storage & Shelf Life

• Storage: 2–8 °C, sealed and protected from light
• Shelf Life: Up to 24 months from the date of manufacture
• Prepared media: Use within validated timeframes specified in the instructions

Scientific Publications

• Soto-Pastrana et al., 2023 – CHROMagar™ StrepB utility in vaginal-rectal GBS screening (Peru)
• Lüthje et al., 2023 – MALDI-TOF identification of chromogenic media isolates
• Rick et al., 2023 – GBS colonization prevalence and risk factors in pregnant women (Guatemala)

CHROMagar™ StrepB offers a fast, accurate, and user-friendly solution for the detection of Group B Streptococcus in pregnant women, enabling better prevention of early-onset neonatal infections. Its distinct mauve colony color, aerobic incubation, and compatibility with enrichment broths make it a trusted tool in prenatal screening programs and obstetric care settings.