Master the board step 3

Master the Boards: USMLE Step 3
Basic Science Correlate
Gram-positive bacteria stain purple due to their thick peptidoglycan layer.
Gram-negative bacteria stain red due to the thin peptidoglycan layer.
Plasma membrane
Gram Positive
Periplasmic space
Peptidoglycan
Plasma membrane
Periplasmic space
Peptidoglycan
Outer membrane
(lipopolysaccharide
and protein
Gram Negative
In cases of early-onset sepsis (within first 24 hours), pneumonia is the most
common cause. The most common organisms involved are these:
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Group B Streptococcus (beta-hemolytic, gram-positive)
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E. coli (gram-negative, rod shaped)
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Haemophilus influenzae (gram-negative coccobacilli)
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Listeria monocytogenes (gram-positive, motile with flagella)
In cases of late-onset sepsis (after first 24 hours), meningitis and bacteremia
are the most common causes. The most common organisms are these:
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Staphylococcus aureus (gram-positive cocci)
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E. coli
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Klebsiella (gram-negative, oxidase-negative rod)
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Pseudomonas (gram-negative aerobic bacteria)
Treatment
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Empiric treatment of neonatal sepsis is to prescribe ampicillin and gentamicin
until 48- to 72-hour cultures are negative.
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If meningitis is possible, add cefotaxime.
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