36-hour-old neonate. Fever, poor feeding, bulging fontanelle. Blood culture grows gram-positive cocci in chains. Beta-hemolytic on blood agar. Bacitracin-resistant. CAMP test positive. What do you give, and why not ceftriaxone?
CAMP test positive locks in GBS (S. agalactiae). The treatment is ampicillin + gentamicin, not ceftriaxone. Why not cephalosporins? Neonatal meningitis empiric coverage must include Listeria monocytogenes, and every cephalosporin misses it. Ampicillin covers both GBS and Listeria. Gentamicin provides aminoglycoside synergy for bactericidal effect. That gap in cephalosporin coverage is a clinical medicine pattern you have to know cold.
How the Gram Stain Works
Tap each step. Watch what happens to the cell wall.
STEP 1 OF 4
Crystal Violet
Purple dye floods every cell regardless of wall thickness. At this point everything looks purple. No discrimination yet between gram-positive and gram-negative.
Organism
Stain
Morphology
Key Virulence
Clinical
First-Line Tx
Pattern Recognition 6 clinical vignettes
Stain result + clinical picture. What organism, what treatment, and why?
Board Walkthrough
25 original clinical vignettes. One at a time. Shuffle resets when you exhaust the bank.
Medically reviewed by Kaitlyn Cocuzzo, MD and Fatima Ali, DO · Last reviewed June 2026
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