Bacterial Pathogenicity Flashcards
(17 cards)
Gram +ve vs Gram -ve bacteria
Acid-Fast Bacteria
Gram +ve but will not show a result on stain due to waxy cell wall
e.g. mycobacteria
Types of Bacteria that interact with body
Symbionts (Lactobacilli) (can make it difficult for other bacteria to grow, can also produce nutrients like vit B12 in animals)
Commensals (Dont provide harm but don’t benefit either) (e.coli, Neisseria species)
Opportunistic pathogens
Primary pathogens (Mycobacteria, Botulinum, Cholerae)
Accidental pathogens (Neisseria meningitidis; commensal bacteria that can go into blood and cause harm)
Opportunistic Pathogens
Pathogens that cause disease in individuals with intact immune systems
Susceptible include:
- Congenital coniditions (CF)
- Acquired conditions (AIDS)
- Immunosupressed (medication)
- Surgical procedures (splenectomy)
- Antibiotic treatment
Clostridum Difficile
Commensal bacteria that lives in balance with other bacteria that can become opportunistic; e.g. when patients are given antibiotics and gut bacteria are killed so bacterium can rapidly divide
Primary Pathogens
Pathogens capable of establishing infection and causing disease in healthy individuals
Tend to produce pathology that favours survival/dissemination of bacterium
- Toxins that kill/impair leukocytes
- Pathogenesis like coughs that disseminate pathogen (TB)
Accidental Pathogens
Neisserium Meningitidis (Kissing virus)
Most neisseria live harmlessly on mucous membranes but become harmful when crossing certain barriers (e.g. entering blood)
Zoonotic/Non-zoonotic Pathogens
Zoonotic - Pathogens that infect animals and transfer to humans
(e.g. Campylobacter jejuni - found in raw chicken mear)
Non-zoonotic pathogens - Human specific pathogens (e.g. Neisseria)
Do bacteria tend to have single or multi-factorial natures of bacterial pathogenesis
They tend to have a multi-factorial nature of bacterial pathogenesis
Exceptions tend to rely on a single toxin
Exo- vs Endo- toxins
Exotoxins - Proteins that disrupt infectee activity
Endotoxins - Lipopolysaccharides that come from vesicles of bacterial cell walls that prompt an immune response
Adhesins/Invasins
Pili or Surface Proteins
Bacteria with Flagella
Campylobacter jejuni
Vibrio cholera
Consequences of bacterial adherence
Prevents pathogens from being lost from host
Causing cytoskeletal changes in host cells that may allow invasion; breaking intracellular junctions
Induction of cytokines which causes inflammation
Survival Factors of bacteria
Complement-evading proteins (tricking immune system)
Capsules (protein [S-layers] or polysaccharide) that protect bacteria from environment
Nutrient scavenging system
- Production of siderophore-binding proteins that have high iron affinity
Bacterial Biofilms
Bacteria going together to form monolayers then microcolonies and eventually biofilms that have an exopolymer matrix and can be difficult to treat/penetrate
Secretion of virulence factors
Methods by bacteria to secrete proteins from the cytosol to the external environment in gram negative bacteria
Haemolysin secreted simply (Type I)
Salmonella (Type III, gets through bacterial cytosol all the way to body cell)
Quorum sensing
Means for bacteria to detect environment
Production and release of small molecule; if not picked back up then bacterium assumes it is alone from other bacteria
When there are enough bacteria, ‘molecule’ concentrations reach a threshold where it is detected by luxR protein which can turn on virulence factors and coordinate responses
