Infectious disease · USMLE Step 1 and Step 2

Streptococcus agalactiae - Group B song

CAMP Test & GBS Prophylaxis, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Streptococcus agalactiae - Group B

Full song on YouTube ↗Spotify ↗

Key points in this song10

Streptococcus agalactiae (Group B Strep) is a beta-hemolytic gram-positive coccus that colonizes the vagina and rectum of 10–30% of pregnant women, making maternal rectovaginal screening at 35–37 weeks gestation standard of care.
The CAMP test is the classic laboratory identifier: GBS produces CAMP factor, which synergistically enhances beta-hemolysin of Staphylococcus aureus, creating an arrowhead-shaped zone of hemolysis on blood agar.
GBS is the leading cause of neonatal meningitis and sepsis in the first 3 months of life, with early-onset disease (< 7 days) acquired via vertical transmission and late-onset disease (7 days–3 months) acquired from environmental sources.
Intrapartum IV penicillin G is the prophylaxis of choice for GBS-positive mothers; ampicillin is an alternative, and clindamycin or vancomycin is used in penicillin-allergic patients depending on sensitivities.
Risk factors triggering intrapartum prophylaxis regardless of screening status include: GBS bacteriuria during pregnancy, previous infant with invasive GBS disease, preterm labor < 37 weeks, prolonged rupture of membranes ≥ 18 hours, or intrapartum fever ≥ 100.4°F.
GBS is the most common cause of bacterial meningitis in neonates (0–3 months), whereas Listeria monocytogenes is the second most common and shares a similar age group, making this distinction high-yield.
GBS possesses a polysaccharide capsule containing sialic acid that inhibits complement activation, serving as its primary virulence factor enabling immune evasion in neonates with immature immunity.
In adults, GBS most commonly causes invasive infections in elderly patients, diabetics, and immunocompromised individuals, presenting as pneumonia, bacteremia, skin/soft tissue infections, or septic arthritis.
GBS is hippurate hydrolysis positive, which biochemically distinguishes it from other beta-hemolytic streptococci such as Group A Strep (Streptococcus pyogenes), which is hippurate negative.
Penicillin G remains the drug of choice for treatment of confirmed GBS infections; GBS is notably resistant to vancomycin monotherapy and lacks intrinsic resistance to beta-lactams, unlike Enterococcus.