Bacterial Pathogenesis Flashcards
Pathogenicity
ability to cause disease
Infection
Host response - inflammation: Pain, Red, Immobility, Swelling, Heat
Endogenous infection
infection by member of NF
Exogenous infection
Infection not by a member of NF
Local infection
infection restricted to an area
Focal infection
localised infection but the pathogen releases by-products that can spread to other parts of body e.g. tetanus
Systemic infection
Infection spread throughout the body by organism and their by-product
Primary infection
initial infection caused by one pathogen
Secondary infection
infection that follows primary infection e.g. may contract another infection because immune sys. is weak from 1º infection: cold -> flu
Latent infection
Infection that one may have but symptoms arise at a later date
Acute infection
rapid @ start & more severe e.g. measles
Chronic infection
Slow progressive disease e.g. TB
Commensals (refer to microbes)
rarely cause disease
Define Pathogen and list 3 types
may cause disease in normal host.
3 O’s: Opportunistic; Obligate; Overt
Opportunistic pathogens
a microbe that can become pathogenic under circumstances like if body is immunocompromised (weak immune sys)
Obligate pathogen
Always cause disease => transferred from one host to another = survive
Overt pathogen
organism that is ALWAYS regarded as pathogenic by clinical labs
What is ID50 and what does it measure?
Infectious dose 50: measure # of bacteria to infect 50% of population of animals exposed (NOTE: Lo val. = more virulent)
What is LD50 and what does it measure?
Lethal dose 50: measure # of bacteria to kill 50% of population of animals exposed (NOTE: Lo val. = more virulent)
Which virulence factors in pathogens aids in attachment to body surfaces?
Glycocalyx (Capsule and slime layer); pili and fimbrae
Explain the emergence of Haemophilius influenzae as a secondary pathogen?
H. influnzae becomes a secondary pathogen if the host’s immune defences are weak due to the response to a primary pathogen: cold-> flu
What is glycocalyx and how can this contribute to the virulence of a pathogen?
capsule/slime layer made up of glycoproteins and /or polysaccharides.»_space; sticky = adherence= resist cough reflex; resist phagocytosis (too big for macrophages)
How may collagenase act as a virulent factor?
Break down collagen in connective tissue = allow pathogen to spread to neighbouring tissues
What is the basis of vaccine for tetanus?
Exotoxin from clostridium tetani converted into toxoids for vaccine: heat treated or formalin treated (= to stimulate primary immune resp.)
Why does a single molecule of diptheria toxin subunit A lead to death of host cell?
subunit A interferes w/ elongation factor 2 (EF-2) = inhibit protein synthesis= cell can’t make new proteins = repeats process until all ribosome is blocked enzyme not consumed) = cell dies.
What gram stain is the Vibrio species and a feature it has?
Gram neg baccilli. Motile- single polar flagella
What does ENTEROTOXIN (endotoxin of Vibrio cholera) do to the human body?
- enterotoxin binds to GM1 (mucosal cells of SI)
- A1 goes in SI via A2 subunit
- A1 stimulates intracellular cAMP production
- = Excrete ions (K+, Cl-,Na+, HCO3-) = water follows ions = large fluid loss
What 2 places were majorly affected by cholera?
Yemen & Haiti
The serotype of Vibrio cholera
Variable O antigen
Cholera toxin component and their roles
5 beta units, one alpha subunit w/ the A2 bridging piece and an active component A1
How does fibrinolysin act as a virulence factor?
DIssolves fibrin clot preventing a phagocyte from capturing the pathogen
What type of exotoxin binds one portion of the host cell receptor while another portion enters the cell w/ enzyme activity to cause toxicity?
AB toxin
Describe how antibody works as normal vs w/ protein A on bact. surface
Normal
- Fab portion (Antibody) binds to epitope (antigen) which is the
- antibody presents to phagocyte (Fc portion binds to receptor on macrophage)
- Bact. engulfed
w/ Protein A
- Fc portion (bottom of antibody) binds to Protein A (antigen)
- Fab portion presented to cell but not recognised bc Fc portion can’t bind on receptor
- Bact. can’t be engulfed
Give 3 examples each of indirect contact and fomite transmission
Indirect: food, water, soil
Fomite (inanimate objects): splinters, blankets, clothing, furniture surfaces
define immunogenicity
ability for antigen to spark an immune response from host
