Staphylococcal and streptococcal infections

1. Big picture

Staphylococci and streptococci are Gram-positive cocci and among the most important causes of community-acquired and hospital-acquired bacterial infections.

For the exam, separate them first by microscopy and basic tests:

Feature	Staphylococci	Streptococci
Microscopy	Gram-positive cocci in clusters	Gram-positive cocci in chains/pairs
Catalase	Positive	Negative
Main dangerous species	Staphylococcus aureus	Streptococcus pyogenes, S. pneumoniae
Typical pattern	Abscesses, catheter infection, bacteremia, endocarditis	Pharyngitis, erysipelas/cellulitis, pneumonia, meningitis, postinfectious immune disease

The practical clinical rule:

Staphylococcus aureus makes pus, abscesses, bacteremia, and metastatic infection. Streptococcus pyogenes spreads rapidly through tissue and causes toxin-mediated shock. Streptococcus pneumoniae causes pneumonia, meningitis, bacteremia, and severe infection in asplenia.

1. Big picture

Unlock the rest of this topic