-
Enters from outside the body
Exogenous
-
Already present as part of normal flora
Endogenous
-
Two dissimilar organisms living in close association
Symbiosis
-
Living on or within, deriving benefit w/o injuring or providing benefit to another organism
Commensalism
-
Both organisms gain benefit, often cannot survive separately
Mutualism
-
One derives benefit while the other is harmed in some way
Parasitism
-
Parasite that lives outside the body
Ectoparasite
-
Parasite that lives within the body
Endoparasite
-
Parasite whose entire life cycle occurs in one host
Monogenic
-
Parasite that requires more than one host
Digenetic
-
One organism derives no benefit while the other is harmed
Amensalism
-
Both organisms are harmed
Synnecrosis
-
Lack of interaction
Neutralism
-
Main host or one in which sexual cycle takes place
Definitive host
-
Temporary host for larval stages, asexual repro, development
Intermediate host
-
Intermediate host actively involved in transmission
Vector
-
Transport host; other than intermediates host that carries parasites to definitive host
Paratenic host
-
Alternate definitive host; maintains infxn
Reservoir host
-
Alternative definitive host that for some reason is rarely infected, often the life cycle cannot be completed
Accidental host
-
GI tract bug: causes malabsorption by numbers/ blocks epithelial surface
Giardia
-
GI tract bug: Penetrates into mucosa and sucks blood
Hookworm
-
GI tract bug: Absorbs large quantities of Vit. B12
D. latum
-
GU tract infxn is typically accomplished by
extension (periurethral bacteria, hematogenous spread, sexual contact)
-
Properties of potential pathogen that allow it to establish within the host, avoid the host defenses and cause disease
Virulence Factor
-
-
Proteins that promote tighter binding of bacteria to host. Name 2 examples
- Adhesins
- M protein= inhibits macrophages ingestion
- F protein= binds fibronectin
-
Name 3 toxins
- Exotoxin
- Neurotoxin
- Membrane-disrupting toxin (usually phospholipase)
- Superantigen
-
Typically heat labile, secreted into local environement: often A-B type (A has enzyme activity; often disrupts cAMP levels)
Exotoxin
-
Inhibits release of neurotransmitters
Neurotoxin
-
Non-specifically bind to a conservatie region of T lymphocyte receptor
Superantigen
-
Name 5 diseases with superantigens
- Toxic Shock Syndrome (TSS)
- RA
- MS
- Graves
- SIDS
-
-
Toxic component of LPS
Lipid A
-
Chelates iron, competes with transferrin
Siderophores
-
Inhibits C3b binding, inhibition of IFN activity, etc.
Sialic acid residues
-
Elevated WBC:
Left-shift?
No shift?
Eosinophilia?
- Left-shift: bacterial
- No shift: viral
- Eosinophilia: parasites
-
Common tests on dip stick for neutrophils
Leukocyte esterase (urine test)
-
Not normally present in urine, but is produced by a # of bacterial species
Nitrite
-
Meningitis most common bacteria:
Neonates?
Children?
Adults?
Elderly?
Post-neurosurgery?
- Neonates: Grp. B Strep, E. coli
- Children: H. influenza, S. pneumo, Neisseria
- Adults: S. pneumo, Neisseria
- Elderly: Bacillus, S. pneumo, HI, Listeria
- Post-neurosurgery: Staph, Pseudomonas
-
Name 2 stains done to check for CSF bacteria
-
Gram stain of male urethal discharge is senesitive/ specific for this, but NOT for females
Neisseria gonorrhoeae
-
Obtained from a chancroid, needs special media for culture
H. ducreyi
-
3 types of Urinary tract specimens
- 1) Clean catch
- 2) Suprapubic: Infants where clean catch was not succesful; suspect anaerobes
- 3) Catheter: Shouldn't be used for culture sample
-
Only thing you refrigerate (and only if it takes more than 2 hours from collection to culture)
Urine sample
-
Feces sample bacteria: Sensitive to drop in pH secondary to anaerobic metabolism, needs specific media
Shigella
-
Feces sample bacteria: Doesn't survive in buffered glycerol
Campylobacter
-
Catalase Test
Add H2O2 to culture, if catalase is present, it will bubble
-
Certain organisms produce diffusible extracellular protein (CAMP factor) that works with beta-lysin of S. aureus to cause hemolysis
Camp test
-
Performed to see if certain bacteria will use citrate as their sole carbon source and ammonium as sole nitrogen source
Citrate utilization test
-
Allows transport of citrate into bacteria
Citrase permease
-
Defense mechanism to clot surrounding plasma and resist phagocytosis. This enzyme is produced by Staph.
- Coagulase
- (Coagulase Test)
-
Measures ability of microorganism to degrade tryptophan into indole, ammonia, and pyruvic acid.
Indole test
-
Degradation of tryptophan is detected through addition of
Kovack's reagent (reacts w/ indole and makes a red color)
-
Used to ID strains of strep pneumonia; has detergent-like action and causes selective lysis of pneumococci
Optochin test (S. pneumonia is optochin sensitive so zone of inhibition will develop around the disk where the bacteria have lysed)
-
Determines if organism possesses cytochrome c
Oxidase test
- Absence of cytochrome c= clear
- Presence of cytochrome c= purple
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