Group B Strep Infections (Overview)

GBS = Strep agalactiae, a beta-hemolytic streptococcus that frequently colonizes the GI/GU tract, also the skin, pharynx, and sometimes upper respiratory tract.

Important cause of infections in 3 populations:
1. Neonates – GBS is acquired in utero, or during passage through the vagina.  Big cause of bacteremia/sepsis, PNA, and meningitis.
2. Pregnant women – causes UTIs, chorioamnionitis, postpartum endometritis, and bacteremia.
3. Nonpregnant adults – is an increasingly recognized important cause of various infections (see below).
Risk Factors for Invasive GBS in Adults:

• Diabetes
• Cirrhosis
• Malignancy
• HIV
•  Renal disease
• Also, nosocomial infections (esp associated with central line infections)
  

Clinical Syndromes caused by GBS – causes a wide variety of syndromes!
1. Skin and Soft Tissue Infections – most commonly celluitis, also causes of necrotizing fasciitis (some associated with a toxic shock-like syndrome), foot and decubitus ulcers
2. Bacteremia, often without a clear source – many are nosocomial, and associated with high mortality.  Can be associated with endocarditis as well (see below).
3. Endocarditis – usually native valve endocarditis, often have large friable vegetations.  Very high mortality and is similar to staph aureus in that it is very virulent, and should prompt consideration of early surgery in addition to Abxs.
4. UTI – common
5. Pneumonia
6. Osteomyelitis and Septic Arthritis – with typical risk factors (prior abnormal joints, trauma, joint replacement, etc)
7. Meningitis – bimodal distribution in adults, with peak in mid-20s and then mid-60s
Treatment is IV penicillin, as GBS is uniformly PCN-sensitive.  Gentamicin is added for synergy in endocarditis.  If PCN-allergic, Vancomycin is the drug of choice.   

(Chanu Rhee MD, 1/17/11)