Bacterial properties and disease Flashcards
Properties; Gene transfer; Infectivity and virulence; Sources and routes; Pathogens; Pathophysiology; SIRS; Sepsis treatment; Susceptability; Therapeutic targets
What is the difference between gram positive and gram negative bacteria?
Gram +ve stains violet -Peptidogylcan cell wall -e.g. Strep pneumoniae Gram -ve stains pink -LPS and peptidoglycan cell wall -e..g E.coli
What define acid fast bacteria?
Bacteria resistant to gram staining method due to waxy mycolic acid in cell walls
Stained with acid-fast stain method - resist decolourisation with acid alcohol
What is the difference between extracellular and intracellular pathogens?
Extracellular replicate outside of cells
Intracellular enter cells to replicate inside endo/phagosome and can survive by escape, preventing lysosome fusion, or survival in the phagolysosome
What are the 3 main ways bacteria exchange genetic material?
Transformation
-absorption and incorporation of naked DNA into host genome from surroundings
-e.g. Streptococcus
Transduction
-Basic process of viral replication
-Some bacterial DNA packaged and inserted into new bacterial genome
Conjugation
-Bridge between two bacteria used to exchange plasmids
Define infectivity
The ability of a pathogen to establish an infection
Define virulence
The ability of a pathogen to cause disease
Define infective dose
The minimum amount of a pathogen required to establish a disease
Influenced by infectivity and virulence
Measured in CFU (colony forming units)
What are the potential sources of bacteria?
Intrinsic - normally reside in body
extrinsic - enter body from external sources via portals of entry
What are 8 possible routes of infection?
Neonate and urogenital tract during birth Surgery Upper respiratory tract Urogenital tract Broken skin Gastro-intestinal tract Faeco-oral
Give 5 examples of important bacterial pathogens and their routes of transmission
Mouth - streptococcuus pyogenes, Meningiococcal septicaemia
Resp tract upper to lower - Streptococcus pneumoniae
Faeco-oral - cholera
Through skin - Staphylococcus aureus
How does neisseria meningitis cause disease?
Gram -ve bacteria is a respiratory endotoxin
Damages RBC/causes shock
Has a polysarccharide capsule ∴ antiphagocytic
How does E. coli cause disease?
Gram -ve
Contaminates food/water
Toxin enters blood stream via large intestine
causes kidney failure
How does Staphylococcus aureus cause disease?
Gram +ve
Respiratory transmission
Releases enzymes and toxins to cause multiple symptoms
What are the 5 stages of sepsis progression?
SIRS Sepsis Severe sepsis Septic shock MODS
What criteria define SIRS?
2 or more symptoms of:
- Temperature >38 or <36
- Resting HR >90
- Resting respiratory rate >20
- WBC count >10k or <4k
