Streptococcus, Group B

Streptococcus, Group B

Streptococcus, Group B (GBS), also known as Streptococcus agalactiae, is a type of bacterial infection that can be found in the human body. It is a significant cause of illness in newborns, pregnant women, and adults with certain chronic medical conditions.

Microbiology

Group B Streptococcus is a Gram-positive bacterium that is beta-hemolytic and belongs to the Lancefield group B. It is a facultative anaerobe and is typically found in the gastrointestinal and genitourinary tracts of humans. The bacterium is encapsulated, which helps it evade the host's immune system.

Pathogenesis

GBS is a leading cause of neonatal sepsis, pneumonia, and meningitis in newborns. The bacterium can be transmitted from a colonized mother to her baby during childbirth. In adults, GBS can cause urinary tract infections, skin and soft tissue infections, and bacteremia.

Epidemiology

Approximately 10-30% of pregnant women are colonized with GBS in the vagina or rectum. The incidence of early-onset GBS disease in newborns has decreased due to the implementation of intrapartum antibiotic prophylaxis.

Clinical Manifestations

In newborns, GBS can cause early-onset disease (within the first week of life) or late-onset disease (from 1 week to 3 months of age). Symptoms in newborns may include fever, difficulty feeding, irritability, and lethargy. In adults, symptoms depend on the site of infection and may include fever, chills, and localized pain.

Diagnosis

Diagnosis of GBS infection is typically made by culturing the bacteria from a sterile site, such as blood or cerebrospinal fluid. Rapid antigen detection tests and polymerase chain reaction (PCR) assays are also used for diagnosis.

Prevention

The primary strategy for preventing early-onset GBS disease in newborns is screening pregnant women for GBS colonization and administering intrapartum antibiotic prophylaxis to those who are colonized. Vaccines for GBS are currently under development.

Treatment

GBS infections are treated with antibiotics. Penicillin is the antibiotic of choice, but alternatives such as ampicillin or cefazolin may be used in patients with penicillin allergies.

Also see

• Streptococcus pneumoniae
• Streptococcus pyogenes
• Neonatal sepsis
• Bacterial meningitis