MEDICAL MICROBIOLOGY Flashcards
SKIN AND WOUND INFECTIONS (26 cards)
What are the primary protective mechanisms of the skin?
Physical barrier, antimicrobial peptides, normal flora, immune system.
What are the two main sources of skin infections?
-Endogenous (normal flora)
-Exogenous (environment, person-to-person).
How does normal flora end up causing skin infections?
Normal flora [e.g. staphylococcus aureus and streptococcus epidermis] is usually harmless under normal conditions but under certain conditions [e.g. breaks in the skin/ immunocompromised individuals] these bacteria can cause skin infections by invading deeper tissues, colonizing or releasing toxins [e.g. Staph in TSS and SSS]
How are exogenous skin infections transmitted?
Direct or indirect contact with infected individuals or contaminated surfaces
What are the key features of Staphylococcus aureus?
Gram-positive coccus, grape-like clusters, golden colonies, resistant to drying & high salt.
Results of staphylococcus aureus on coagulase and hemolysis test
Staphylococcus aureus is coagulase-positive and exhibits beta hemolysis
What infections does S. aureus cause?
Impetigo, folliculitis, furuncles, carbuncles, cellulitis, wound infections, toxic shock syndrome.
How is MRSA treated?
Vancomycin is used to treat beta-lactam resistant bacteria (MRSA) - Vancomycin is a glycopeptide that bypasses PBPs, directly inhibiting peptidoglycan synthesis.
What are the key features of S. pyogenes?
Gram-positive coccus, chains, beta-hemolytic.
What infections does S. pyogenes cause?
Impetigo, erysipelas, cellulitis, necrotizing fasciitis, toxic shock syndrome
What is the first-line treatment for S. pyogenes infections?
Penicillin (no resistance in GAS) or amoxicillin
What is the most common cause of folliculitis?
S. aureus
How is a furuncle different from a carbuncle?
Furuncle is a single abscess in a hair follicle; carbuncle involves multiple follicles & deeper tissue.
What is the main difference between erysipelas and cellulitis?
Erysipelas is a superficial infection (dermis), cellulitis is deeper (subcutaneous).
What are the clinical features of folliculitis?
Small, red, raised bumps or pustules around hair follicles- may have a small white or yellow pus-filled head. Found on neck, axilla and buttocks
-may experience itching
What are the clinical features of furuncles?
Small abscesses that develop in the region of a hair follicle- red, may develop into abscesses
What are the clinical features of carbuncles?
Multiple red, swollen, painful lumps with pus drainage
What are the clinical features of erysipelas?
Erythema (redness), pain, fever, and lymphadenopathy (swollen lymph nodes)
What are the clinical features of cellulitis?
poorly defined erythema and marked constitutional signs and symptoms
What are the two main types of necrotizing fasciitis?
Type 1: Polymicrobial (GAS, anaerobes, Gram-negatives).
Type 2: Monomicrobial (S. pyogenes, S. aureus).
Q: What are key clinical signs of necrotizing fasciitis?
Severe pain, redness, bullae, crepitus, gangrene.
What is the treatment for necrotizing fasciitis?
Surgical debridement + broad-spectrum IV antibiotics (Piperacillin-Tazobactam, Clindamycin).
What causes Staphylococcal Scalded Skin Syndrome (SSSS)?
Exfoliatin A and B released by S. aureus
What are key features of Staphylococcal toxic Shock Syndrome?
Fever, hypotension, diffuse erythematous rash and multi-organ failure
