III - Infection Biology Flashcards
Microbes that can cause disease
pathogens
Pathogens that cause disease only in the immunocompromised
opportunistic pathogens
Measure of a microbe’s ability to cause disease
virulence
Virulence is determined by
virulence factors - capsule, endotoxin, exotoxin
Number of organisms required to cause disease in 50% of the population
ID50
Presence of microbes, symptoms of disease
infection
Mechanisms of Bacterial Disease
production of toxins, induction of inflammation
Human-Human Bacterial Transmission
sexual, fecal-oral, inhalation, transplacental, blood
Non-Human-Human Bacterial Transmission
soil, water, animal, vector, feces, fomites
Mediates attachment of bacteria
pili
Mediates strong adherence to the surface of human cells
glycocalyx
Surface protein of Salmonella and E. coli that mediate binding to endothelium and to extracellular proteins such as fibronectin
curli
Bacterial Invasion: Spread through subcutaneous tissue
collagenase, hyaluronidase
Bacterial Invasion: Accelerates formation of a fibrin clot coating the organisms with a layer of fibrin
coagulase
Bacterial Invasion: Allows adherence to mucous membranes
IgA protease
Bacterial Invasion: Destroys both neutrophilic leukocytes and macrophages
leukocidin
Bacteria with IgA Protease
Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Neisseria gonorrhoeae
Protects against phagocytosis
polysaccharide capsule
Anticapsular antibodies allow more effective phagocytosis to occur
Opsonization
Antiphagocytic cell wall protein of S. pyogenes
M Protein
Cell wall protein of S. aureus that prevents complement activation
Protein A
Exotoxin: Source
gram (+), gram (-)
Exotoxin: Secreted from cell?
yes
Exotoxin: Chemical Compound
polypeptide
Exotoxin: Location of Genes
plasmid, bacteriophage
Exotoxin: Toxicity
high
Exotoxin: Antigenicity
high
Exotoxin: Vaccine
toxoids
Exotoxin: Heat Stability
destroyed at 60°C (except Staphylococcal enterotoxin)
Exotoxin: Typical Diseases
tetanus, botulism
Endotoxin: Source
gram (-)
Endotoxin: Secreted from cell?
no
Endotoxin: Chemical Compound
lipopolysaccharide
Endotoxin: Location of Genes
bacterial chromosome
Endotoxin: Toxicity
low
Endotoxin: Antigenicity
low
Endotoxin: Heat Stability
stable at 100°C for 1 hour
Endotoxin: Typical Diseases
meningococcemia
Polypeptides secreted by certain bacteria that alter specific cell functions resulting in the symptoms of disease
exotoxins
Exotoxins: Active subunit, toxic, less toxic in toxoids
A subunit
Exotoxins: Binding subunut
B subunit
All exotoxins are heat-labile except
Staphylococcal enterotoxin
MoA of Exotoxins: Diphtheria, cholera, E.coli heat-labile toxin, pertussis
ADP-ribosylation
MoA of Exotoxins: Toxic Shock Syndrome, Staphylococcal enterotoxin, erythrogenic toxin
Superantigen
MoA of Exotoxins: Tetanus, botulinum, lethal factor of anthrax toxin, Scalded Skin toxin
Protease
MoA of Exotoxins: Clostridium perfringens alpha toxin
Lecithinase
Can elicit widespread activation of the complement and coagulation cascades
Superantigens
Lipoplysaccharides located in the outer membrane of gram (-) bacteria
endotoxins
Toxic component of LPS
Lipid A
Induces the overproduction of cytokines such as TNF and IL-1, activates the complement and coagulation cascade resulting in disseminated intravascular coagulation
Lipid A
All bacteria have cell walls composed of peptidoglycan except
Mycoplasma pneumoniae
Only gram (+) bacteria with endotoxin
Listeria monocytogenes
All bacterial capsules are composed of polysaccharide except
Bacillus anthracis
All exotoxins are heat-labile except
Staphylococcal enterotoxin
Determine whether antibodies are present in a patient’s serum, detect the antigens of the organism in tissues or body fluids, at least a fourfold increase in titer between the acute and convalescent samples, IgM antibody for acute infection
Serologic Tests
Nucleic acid amplification tests, nucleic acid probes, nucleic acid sequence analysis
Molecular Tests
Highly specific, sensitive, faster than culture
Molecular Tests
Useful for bacteria that are difficult to culture such as Chlamydia and Mycobacterium
Molecular Tests