DurgicalDurgical
EN
Open the app

Microbiology · Streptococci and enterococci

Streptococcus agalactiae !

  • Bacterium
  • Gram-positive
  • Exam priority: medium

A bacterium that lives in the gut and vagina of many pregnant women and can cause sepsis, pneumonia and meningitis in the newborn.

Updated 2026-11-01

Also called: group B streptococcus, GBS

At a glance

Gram
Gram-positive
Shape
Cocci in chains
Oxygen
Facultative anaerobe
Family
Streptococcaceae
Stain
Gram positive; catalase negative; beta-haemolytic

Morphology

  • Gram-positive cocci in chains
  • Narrow zone of beta-haemolysis
  • Bacitracin resistant; CAMP positive; hydrolyses hippurate

Transmission

  • From the mother's genital and gut tract to the baby during birth
  • The source of late-onset disease is often unclear

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Virulence factors

  • Polysaccharide capsule rich in sialic acid
  • CAMP factor

Diseases it causes

Clinical picture

  • Newborn with breathing difficulty, apnoea or unstable temperature
  • Infections in pregnant and postpartum women and in older adults with diabetes or cancer

Diagnosis

  • Prenatal screening with a vaginal-rectal culture
  • CAMP positive, bacitracin resistant, hippurate positive
  • Blood and cerebrospinal fluid cultures in the newborn

Treatment

Penicillin or ampicillin are preferred. Intrapartum antibiotic prophylaxis for colonised mothers reduces early-onset disease.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Universal prenatal screening
  • Antibiotic prophylaxis during labour when indicated

Test yourself

Think of the answer, then tap the question to see it.

Which lab test is characteristic of group B streptococcus?

A positive CAMP test (plus bacitracin resistance).

How is early-onset group B sepsis prevented?

With prenatal screening and intrapartum antibiotic prophylaxis for colonised mothers.

Which three classic bacteria cause newborn sepsis and meningitis?

Group B streptococcus, Escherichia coli and Listeria monocytogenes.

Add to my cards (3)

← Back to the group: Streptococci and enterococci

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: About Group B Strep Disease (CDC, 2024); Clinical Overview of Group B Strep Disease (CDC, 2024).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.