Exam 2 Lecture 12 Flashcards
Corynebacteria, Listeria, Bacillus
Describe the Gram Stain of Corynebacterium matruchotii
Gram Positive rods with clubbed ends
True or False: Humans are the only natural reservoir of Corynebacterium diphtheriae
True
How is corynebacterium diphtheriae spread? (3)
- Respiratory droplets
- Skin lesions
- Fomites
Where do convalescent patients commonly carry corynebacterium diphtheriae?
Pharynx, nasal area
Name the principal virulence factor for corynebacterium diphtheriae
Diphtheria toxin (DT)
The __ subunit is catalytic, while the __ subunit accomplishes cell binding
A, B
Via acidification of the endosome, the B subunit releases the A subunit from the endosome into the cytoplasm, where it catalyzes ____-_________ of _________ _____ __.
ADP-ribosylation
elongation factor 2
True or False: many molecules diphtheria toxin are needed to kill cells.
False - just 1 molecule is sufficient
What encodes the diphtheria toxin?
lysogenic bacteriophage
True or False: C. diphtheriae strains that lack the lysogenic bacteriophage do not produce diphtheria toxin and do not cause the disease diphtheria.
True
Name the chromosomal gene (not phage encoded) that represses the expression of DT at high iron conditions
DtxR
Where is most host iron?
Heme bound or intracellular
True or False: When iron is low, DtxR represses expression of DT
False
What is DT co-regulated with? (2)
- Endogenous genes encoding bacterial iron transport system
2. HmuO (heme oxygenase)
What is the function of heme oxygenase?
It utilizes heme and hemoglobin as a source of iron
Diphtheria is historically a ______ disease.
childhood
Name the key local effects of diphtheria toxin (4)
- Pharyngitis
- Epithelial cell necrosis & inflammation
- Formation of a pseudomembrane
- Mechanical obstruction of airway
What is characteristic about the pseudomembrane?
It is a gray/yellow/white membrane with surrounding inflammation
Name the key systemic effects of DT (2)
- Paralysis of soft palate and muscle groups like the diaphragm
- Myocarditis and cardiomyopathy
What heart problems may arise from DT? (3)
heart enlargement, arrhythmia, pump dysfunction (which can lead to shortness of breath)
What infections caused by DT usually arise without systemic complications?
Superficial skin infections
What compound is used to inhibit oropharyngeal microbiota and Gram (-) bacteria?
Potassium tellurite
What color colony does diphtheria produce?
Dark brown/black
What leads to the dark brown halo?
H2S production from L-cysteine
How has diphtheria been prevented/almost eliminated?
DTaP vaccine
DTaP consists of toxin treated with ______ to mitigate potential toxicity and retain the immunogenicity of the native form of the antigen.
formalin
What does the diphtheria toxoid inactive?
The B subunit of DT (but maintains subunit A’s structure/antigenicity)
The __ subunit of DT ensures that the toxin is taken up by endocytosis, while acidification of ____ releases the __ subunit into the cytosol
B; endosome; A
Because the toxoid inactivates the B subunit, the __ subunit cannot translocate from the
______ to the ______
A
endosome
cytoplasm
________ may be used for life threatening illness in people who are not vaccinated.
anti-toxin
True or False: Corynebacterium jeikeium also produces DT
False
Where is corynebacterium jeikeium typically found?
skin
What systemic diseases can corynebacterium jeikeium cause? (5)
- bacteremia
- endocarditis
- pneumonia
- osteomyelitis
- meningitis
Where is corynebacterium jeikeium typically acquired?
Hospital (nosocomial infection)
True or False: corynebacterium jeikeium is not antibiotic resistant thus it responds well to a variety of antibiotics
False - it is multi-drug resistant
Describe the Gram Stain of Listeria
Short Gram Positive coccobacilli
Listeria monocytogenes is an ________ pathogen
intracellular!!
Does listeria contain catalase?
Yes
What type of hemolysis does listeria display on blood agar?
Beta hemolysis (small colonies w/ discrete zones)
What environmental conditions allow for growth of listeria? (3)
- Low temps
- Low pH
- High salt
What part of the body does listeria colonize?
Large intestine
_____ and ____ allow for listeria to bind and invade non-phagocytic cells
lnlA, lnlB (internalins)
What does lnlA bind to?
e-cadherin on intestinal epithelial cells
What does lnlB bind to?
hepatocyte growth factor receptor
______ are involved in crossing critical anatomical membranes
internalins
what is the name of the cholesterol-dependent pore-forming cytolysin in listeria?
listeriolysin (LLO)
True or False: Listeria grows well in the cytoplasm but is unable to replicate in the phagosome
True
what does LLO do?
causes lysis of the bacteria-containing phagosome
in addition to listeriolysin, _______ help release bacteria from the phagosomes
phospholipases
Lytic activity is limited by __ _____, _________ _________ and ________ _______
pH optima
translational regulation
proteolytic degradation by proteasome (PEST)
What is the surface protein that leads to polar distribution in Listeria?
ActA
What does ActA do?
Promotes actin polymerization and the “comet tails” that push bacteria through the cytoplasm
Immunity depends upon _____ __ cells
CD8+ T cells
Listeria is frequently ______
foodborne
Who is particularly vulnerable to listeria infection? (6)
- Pregnant women and their fetuses
- Elderly
- Alcoholics
- Diabetics
- Compromised individuals
- Corticosteroid users
Vertical transmission of listeria can occurs via _________ ________
feto-placental infections
In people vulnerable to listeria, they may get _______ or _______
meningitis
septicemia
What listeria symptoms do immune competent hosts suffer from?
- GI infections [high inoculum]
- mild flu like symptoms [low inoculum]
What is the mortality rate of Listeria when critical anatomical barriers are crossed?
20-30%
Listeria is primarily diagnosed by ______
culture
For diagnosis of Listeria, cultures can be taken from ….. (5)
- CSF
- blood
- amniotic fluid
- placenta
- fetal tissue
Describe the Gram Stain of Bacillus Cereus
Long/wide Gram Positive rods
What is unique about bacillus cereus?
able to form spores
Bacillus cereus is __ hemolytic
beta
Bacillus cereus can decolorize to appear ___
GNR
Name characteristics of spores formed by bacillus cereus (4)
- heat and desiccation resistant
- metabolically inactive
- autoclave withstanding
- germinate into cells after decades of persistence
What does bacillus cereus produce?
- enterotoxins
Enterotoxins can be broken down into 2 categories. What are they?
- heat stable toxins
2. heat labile toxins
The heat-stable toxin is _____ tolerant and leads to ________
acid, vomiting
which form of the toxin is a circular peptide with ionophore activity?
heat stable
The heat-labile toxin is associated with ______ illness
diarrheal
GI infections are found in ___ of food tested. ____ is a common vehicle for illness.
25%
rice
The heat-stable form is due to ……
toxin contamination of food (2-3 hr incubation)
The heat-labile form is due to ………………
intestinal bacterial replication (6-24 hr incubation)
