🧬Microbiology Flashcards
(98 cards)
What are the 4 main groups of microbes?
- Eukaryotes
- Parasites
- Protozoa
- Fungi - Prokaryotes (no nucleus)
(ie. bacteria) - Viruses (acellular)
- Prions (acellular)
What are the basic steps for infection to occur?
- Pathogen
- Susceptible host
- Entry of pathogen to host
- Colonization (adhere, replicate, evade)
- Damage caused
- Direct vía virulence factors
- indirect via immune system
What are the main portal of entry for pathogens?
- Mucous membranes
- Resp Tract
- GI
- GU
- Placenta - Skin
- Parenteral
- bites
- puncture
- wound
- injection
Pathogens portal of entry
- Most have preferred POE
Ex. Strep - Some cause illness from any entry
Ex. Ebola - Some cause different disease depending on POE
Ex. Bubonic/pneumonic plague.
What is the progress of infection following adherence?
- Exposure
- Colonization
- Latency period
- Incubation period
- Infection
- Period of communicability
What are examples of human barriers to infection?
- Lysozyme in tears/sweat
- HCl in stomach
- Fatty acids
- Phagocytosis WBC
- Ciliated mucosa (resp) (physical)
- Skin
What are virulence factors for colonization of the host?
- Adherence: adhesins (bacteria), attachment proteins (viruses)
- Destructive enzymes: hyaluronidase (destroy connective tissue), hemolysins
- Toxins: anthrax (bacteria)
What are virulence factors for immunoevasion?
- Prevent antibody binding: capsule (bacteria, yeasts)
2. Prevent phagocytosis: Biofilm (bacteria, yeast)
What are virulence factors for immunosuppression?
- Destructive enzymes:: immunoglobulin proteases
2. Conversion enzymes: catalase
What are virulence factors for invasion of host cells?
Destruction (lysis) of host cells
What happens during indirect damage via host immune response?
Septic shock
Endotoxins
Part of Gram-negative cell wall
(Lipopolysaccharide; LPS)
- Triggers immune cells to release cytokines in toxic concentrations
- Antibiotics can trigger release (get worse before gets better)
Exotoxins
Enzymes that are secreted by bacteria that perturb some aspect of normal host physiology
- Generally specific to genus/species
- Highly immunogenic
What does damage to the host facilitate?
- Invasion
- Dissemination
- Transmission
Ex: cholera uses toxin to cause diarrhea in order to spread to others
What are the steps in nucleic acid sequences? (PCR)
- Denaturation
- Annealing - primer binds
- Elongation - extension of primer
- Repeat
- Detection
Gram Negative
- PINK
- Outer membrane
- Periplasmic space
- Liposaccharide (LPS) endotoxin = SEPTIC SHOCK
- 10-20% of cell wall is peptidoglycan
Gram Positive
- PURPLE
- NO Outer membrane
- NO LPS
- 60-90% cell wall is peptidoglycan
What are the three shapes of bacteria?
- Spherical
- Rod-like
- Spiral
What are the different arrangements of bacteria?
- Clusters
- Chains
- Pairs
- Tetrads
Glycocalyx
Viscous, gelatinous polymer composed of polysaccharides, polypeptides, or both.
- Capsule = organized and attached to cell wall
- Slime layer = unorganized and loosely attached
- Visualized with negative stains
- Prevents antibodies recognizing bacteria
- Assists with attachment to surfaces
Tropism
The type of host cell receptors that bind bacteria (adhesins) and visuals (attachment proteins).
What are the 2 general phases of bacterial growth?
- Free-swimming (planktonic)
2. Sessile, surface associated (Biofilm)
Biofilms
Aggregated of organisms encased in a matrix consisting of proteins, carbohydrates, and nucleic acid complex structure.
- Ubiquitous
- Resistant to immune clearance, antibiotics, disinfectants
- Metabolically less active bacteria
What are the six links in The Chain if Infection?
- Pathogen
- Reservoir
- Portal of exit
- Means of transmission
- Portal of entry
- New host