Lecture 13 Flashcards
How do bacteria invade human body
-Through mucus membranes (respiratory and garstrointestinal tracts, urinary tract and genital openings)
-Non intact skin (bites, wounds, injections…)
How do bacterial pathogens damage host cells?
- Invasion
- Toxins
What is invasion
Ability to spread to other loc in host by invading cells or tissues. Atp that signs of illness and disease occur
what are Toxins
Very specific virulent factor produced by bacterial pathogens, poisonous substances to host
What is toxigenicity
Organism’s ability to make toxins
Two categories of toxins
Endotoxins and exotoxins
Exotoxins
Toxin secreted by microorganism into surrounding enviro
Endotoxin
Toxin release by microorganism into environment when it dies, it’s part of cell wall
Impacts to metabolic pathways in eukaryote host by bacterial toxins
- Damage cell membrane
- Disrupt prot synthesis
- Inhibiting function of nervous syst
- Inhibiting activation of host immune syst
Some pathogens
Gonorrhea, lyme disease, strep throat, tuberculosis, tetanus
What are antibiotics
Drugs to treat infections caused by bacteria
What is zone of inhibition (ZOI)
Clear zone surrounding antimicrobial agent, complete absence of bacteria
What is a bacterial lawn
Dense and uniform layer of bacteria on agar plate
What is selective toxicity
When agents affect pathogens and not host (by interacting with structures not present in/diff from host)
Antibiotic modes of action
- Cell wall synthesis
- Cell membrane function
- Metabolic reaction
- Prot synthesis
- Dna synthesis
Inhibitors of cell wall synthesis (ex penicillin)
Targets cell wall(critical for survival of bacteria)
Inhibitors of cell membrane function:
Content of cell will leak out and cell dies. However, often poorly selective and can be toxic for systemic use in mammalian host -> only topical
Inhibitors of metabolic processes:
Inhibits certain pathways necessary for bacteria survival
Inhibitor of prot synthesis
Target ribosome components (diff from eukaryotic) and leads to death bc prot synthesis is necessary for multiplication/survival of bacteria
Inhibitors of nucleic acid synthesis
Binding to components involved in process of dna or rna -> hinders multiplication
Cell wall function
Very strong, resists bursting/maintains shape, structural support and protection
What is composed of peptidoglycan
Cell wall in bacteria
What is the gram stain
Determines gram positive (purple) and gram negative (red) bacteria and proper antibiotic to choose
Which bacteria stain purple (gram positive)
Those with thick peptidoglycan walls
Which bacteria stains red (gram negative?
Those with thin peptidoglycan wall with thick outer layer of lipids and carbohydrates
Gran stain process steps
- Crystal violet added (primary stain)
- Iodine makes purple stick to peptidoglycan layer (if present)
- Alcohol is decolourizing agent (gram - lose colour)
- Safranin sticks to gram- cell walls
Gran stain process steps
- Crystal violet added (primary stain)
- Iodine makes purple stick to peptidoglycan layer (if present)
- Alcohol is decolourizing agent (gram - lose colour)
- Safranin sticks to gram- cell walls
Penicillin kills which gram bacteria
Gram positive
Which bacteria-toxin
Endotoxin = gram negative
Exotoxin = gram positive
Narrow Spectrum antibiotics
Affects small range of bacteria (each target specific one)
Broad spectrum antibiotic
Affects large range of bacteria, also kills natural microbiota -> increases risk of opportunistic infections (ex yeast infections)
Penicillin mechanism
Cell wall inhibitors (gram positive)
Streptomycin (antibiotic) mechanism
Inhibits protein synthesis (broad spectrum, tuberculosis
Where is the chromosome in prokaryotes
Nucleoid region
Plasmids are and can
Smaller circular dna fragments (no genes essential for survival) and can be transferred between bacterial cells (conjugation)
Why carry plasmid through evolution if not necessary?
Bc could be advantageous (ex antibiotic resistant gene -> gets passed on and more have it)
Antibiotic resistant bacteria grow how
The more antibiotics used, the greater the “selective pressure”. Antibiotics create an enviro which favours growth of resistant bacteria by killing non resistant ones
How fast can antibiotic resistant bacteria multiply
Once resistance established, rapidly evolves bc rapidly multiplies. Overnight, one can multiply to become a million
