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28 Cards in this Set

  • Front
  • Back
morphology of corynebacteria
pleomorphic {varying size and shape} gram positive rods
do not form spores
often club shaped
arrangement in gram stain resembles chinese characters
2 groups of corynebacteria
Corynebacterium diptheriae (the cause of diptheria)

all others, generally called diptheroids (normal inhabitants of skin and throat)
the only natural hosts for corynebacterium diptheriae (cause of diptheria)
transmission of corynebacterium diptheriae (cause of diptheria)
usually by respiratory droplets
incubation period of corynebacterium diptheriae (cause of diptheria)
2-5 days (short) of bacterial growth in the throat, results in a local inflammatory response
early symptoms of diptheria
local inflammatory response to bacterial growth in throat:
fever, cough, sore throat, that progresses to form a gray PSEUDOMEMBRANE (of fibrin, necrotic epithelium, and white cells)
other than throat, where might diptheria infections be seen
in the tropics, also seen as necrotizing skin infections spread by contact
how does diptheria cause systemic disease?
bacteria (confined to pharynx) produce an EXOTOXIN that damages eukaryotic cells (including those in heart, kidney, nervous system, etc..)
characteristics of EXOTOXIN-
chemical composition:
bacterial origin:
coded by bacteriophage or plasmid:
stable to boiling:
highly antigenic and easily induces protective Ab:
chemical composition: PROTEIN
bacterial origin: GRAM (+) or (-)
Coded by phage or plasmid: USUALLY
stable to boiling: USUALLY NOT
highly antigenic and easily induces protective Ab: YES
characteristics of ENDOTOXIN-
chemical composition:
bacterial origin:
coded by phage or plasmid:
stable to boiling:
highly antigenic and easily induces protective Ab:
chemical composition: LPS
bacterial origin: Gram (-) OM
coded by phage or plasmid: NEVER
stable to boiling: YES
highly antigenic and easily induces protective Ab: NO
ENTEROTOXINS are the same as...
All toxogenic strains of C. diptheriae are lysogenic for a specific temperate bacteriophage called:
The gene for the diptheria toxin is part of what genome?
a specific temperate bacteriophage called beta,

capable of lysogenizing bacteria.. to integrate their genome into (and be replicated with) host chromosome
What are the two ways by which a temperate bacteriophage can alter the phenotype of bacteria?
TRANSDUCTION (by transferring bacterial genes from their previous bacterial host)

CONVERSION (via the expression of their own bacteriophage genes)
What are the 2 domains of Diptheria Exotoxin?
B DOMAIN: binds to a specific cell surface receptor, causes endocytosis of EXOTOXIN

A DOMAIN= "toxic domain" separates from B domain, leaves vesicle to enter cytoplasm, BLOCKS EUKARYOTIC PROTEIN SYNTHESIS {by inactivating EF2}
What is the role of the "A DOMAIN" of Diptheria Exotoxin
"TOXIC DOMAIN" enters cytoplasm of infected cell, acts as enzyme

blocks EUCARYOTIC PROTEIN SYNTHESIS by INACTIVATING EF2 (elongation factor 2) mechanisms involves: adenosine diphosphate ribosylation
immunity to Diptheria depends on what?
presence of Ab against the toxin {ANTITOXIN)
describe the vaccine used for immunity to Diptheria
formaldehyde treated diptheria toxin = TOXOID
{formaldehyde destroys the toxic activity, but immunogenicity of toxin is maintained}
protection lasts 10 years
How is Diptheria Dx made?
-IN VITRO TEST (suspected bacteria grown as single streaked line, at right angle to strip of antitoxin-soaked paper) in agar (diagonal precipitates form)
-characteristic growth on tellurite and Leoffler media
-staining characteristics (metachromatic granules)
-demonstration of toxin production via indradermal injection of animals (to produce local necrosis)
how is diptheria treated?
must be treated immediately

treated with HORSE or HUMAN ANTITOXIN (to neutralize free toxin)

Penicillin is used to eliminate bacteria that would continue to produce toxin
prevention of diptheria in those exposed
those in contact with infected patients should be reimmunized and treated with penicillin
Diptheria epidemiology
before immunization (many carriers of Corynebacterium diptheriae)

epidemics are now seen in poorly immunized populations with inadequate medical care. (major problem in developing countries with inadequate immunization)
ALL SKIN TESTS involve what?
intradermal injection of small volume of a BIOLOGICAL REAGENT

NEGATIVE (if nothing happens)
POSITIVE (if somethign happens)
If skin test reagent is a TOXIN, a positive response means what?
NO IMMUNITY (no toxin-neutralizing Abs)

{whereas a negative response means immunity resulting from previous infection or immunization}
If skin test reagent is a delayed-hypersensitivity-inducing Ag, a POSITIVE response means what?
IMMUNITY (cell mediated immunity, induced by previous infection or immunization)

{whereas a NEGATIVE response means no previous infection)
What is the SHICK TEST?
(what is the potential complication?)
intradermal injection of a small amount of toxin

persons lacking antibody dvp local necrotic-inflammatory response that develops slowly and is maximal at 5 days

potential COMPLICATION: delayed hypersensitivity against other proteins
How can Shick Test be used to determine if reaction is a true positive, a pseudopositive or a combined positive?
Inject TOXIN in one arm and TOXOID in other arm

TRUE POSITIVE: (toxin injected arm will be (-) @ 1.5 days, (+) @ 5 days)

PSEUDOPOSITIVE: (both toxin arm and toxoid arm with be (+) @ 1.5 days and (+/-) @ 5 days)

COMBINED: toxin arm (+) @ 1.5 & 5 days, toxoid arm: + @ 1.5 days, (+/-) @ 5 days
What do the following Shick Tests Results indicate regarding: IMMUNITY & HYPERSENSITIVITY

Negative Rxn
Positive Rxn
Pseudo Positive
Combined Poisitive
Negative: IMMUNE but not hypersensitive
Positive: not immune, not hypersensitive
Comb: not immune, yes HYPERSENSITIVE