USMLE STEP 1 Microbiology-1048 Questions with Complete Solutions

USMLE STEP 1 Microbiology-1048 Questions with Complete Solutions What is a special cellular component of fungal membrane targeted in anti-fungal medication? - CORRECT ANSWER Ergosterol A major sterol What is the special component of bacterial cell wall? - CORRECT ANSWER Peptidoglycan Where are the normal flora found? Contributions to health? Causes of infection? - CORRECT ANSWER Location: - found on body surfaces contiguous with outside environment (GI, etc.) - Semipermanent (dependent on life-changes) Contributions to health: - Protective functions by maintaining a certain pH other microorganisms cannot proliferate - Nutritional: synthesizing vitamin K + B Causes of infection: - "Getting lost" (E. coli to urethra causing UTI) - Overgrowth due to immunocompromised state Are there normal flora in the blood or organs? - CORRECT ANSWER No Sterile environment What is a medically important normal flora found in the nose? - CORRECT ANSWER Staphylococcus aureus What are the pathogenicity mechanisms? (8) - CORRECT ANSWER 1. Colonization (adherence) 2. Avoiding immediate destruction by host defense sys. 3. "Hunting + Gathering" needed nutrients 4. Antigenic variation 5. Ability to survive intracellularly 6. Type III secretion systems 7. Inflammation of Immune-mediated damage 8. Physical damage What are the types of colonization? - CORRECT ANSWER 1. Adherence to cell surface - *Pili*/fimbriae: primary mechanism in most G- bacteria (E. coli)