USMLE Step 1
| Frente | How does vancomycin act? |
| Verso | Mechanism of action: binds D-Ala–D-Ala Class: Glycopeptide Effect: blocks peptidoglycan synthesis → weak cell wall Spectrum: Gram-positive only Uses: MRSA, C. difficile (oral) Resistance: D-Ala–D-Lac substitution |
| Frente | What are the key features and causes of subacute infective endocarditis? |
| Verso | Slow onset (weeks) Low virulence organisms → Viridans streptococci Especially Strep mutans and Strep sanguinis Typically involves the left-sided valves (mitral > aortic) Associated with: Dental caries Dental procedures Patients with abnormal/damaged heart valves Key clue: 🦷 Dental flora → Subacute → Left heart (Viridans). |
| Frente | Which bacteria are gamma-hemolytic? |
| Verso | Enterococcus (E. faecalis, E. faecium) No hemolysis |