HAIs

Question 1

MRSA

Answer 1

HAIs

• a leading cause HAI
• defining feature is staphylococcal cassette chromosome mec (**SCCmec)
  
  • encodes *mecA gene
    
    • product is altered penicillin binding protein
    • *imparts broad spectrum β-lactam resistance
  • many different SCCmecs
    
    • highly diverse in structural organization and genetic content
    • E.g. *Panton-Valentine leukocidin (PVL)
      
      • forms pores in neutrophil membranes → lysis

Question 2

Acinetobacter baumannii

Answer 2

HAIs
- Gr- coccobacillus
- ubiquitous  
- opportunist
  - *innate resistance to desiccation + remarkable ability to accumulate different resistance mechanisms
- *a leading cause of HAIs
   - pneumonia, UTIs, wound infect., sepsis
- capsule
- obligate aerobes
- grow on wide variety media, wide temp. range
Virulence
- *polysaccharide capsule
- *pili
- *biofilms
- *extreme antibiotic resistance, intrinsic + acquired
- OmpA
- phospholipases, proteases
- siderophores
- OM blebbing

Question 3

Clostridium difficile

Answer 3

HAIs
- Gr+ *endospore-forming rod
- *obligate anaerobe
- flagella
- leading cause antibiotic-associated diarrhea hospitals, long-term care facilities
- *#1 HAI organism
- causes *pseudomembranous colitis
Virulence
- *endospores 
- *toxin A- enterotoxin
   - **predominates in watery diarrhea
- *toxin B- cytotoxin
   - **predominates in pseudomembrane