Lecture 8 -- Corynebacterium & Listeria Flashcards
are corynebacterium, listeria, and bacillus spore forming or non-spore forming? what is their shape?
spore-forming: bacillus
non-spore forming: corynebacterium and listeria
corynebacterium is CLUB SHAPED
bacillus and listeria are rods
is bacillus anthracis an aerobe or anaerobe?
aerobe
corynebacterium has a ___ shape while listeria monocytogenes is a ___ shape
corynebacterium has a IRREGULAR (club) shape, while listeria monocytogenes has a uniform shape
both are NON SPORE FORMING
give an example of an anaerobic spore forming rod
clostridium difficile
what can you say about a bacteria that has the ability to form spores?
also, give 2 examples of bacteria that can form spores
bacillus anthracis (aerobic) and clostridium difficile (anaerobic)
both can form spores, meaning that they can go dormant and survive in very harsh environments
what disease does corynebacterium diptheriae cause?
what toxin does it have?
diptheria
DT toxin (diphtheria toxin)
can corynebacterium diptheria form spores?
NO
is corynebacterium diptheria motile?
no
does corynebacterium have a capsule?
no
what is the source of corynebacterium diptheria?
what is the source of listeria monocytegenes?
source of corynebacterium diptheria = human carriers
source of listeria monocytegenes = food and animals
can listeria monocytogenes form endospores?
is it encapsulated?
no to both
is listeria monocytogenes motile?
yes
what disease(s) does listeria monocytogenes cause?
meningitis, bacteremia
what is the major toxin of listeria monocytogenes
LLO (listeriolysin O)
can bacillus form endospores?
yes
is bacillus anthracis encapsulated?
is it motile?
can it form endospores?
yes encapsulated
NOT MOTILE
can form endospores
what is the source of bacillus antrhacis
imported animal products
what disease(s) does bacillus anthracis cause
anthrax
corynebacterium diptheria is gram ____, catalase _____, and is ___ shaped
is anaerobic or aerobic?
gram positive
catalse positive
club shaped
aerobic
can corynebacterium diptheria form spores?
no
what is the only known source of corynebacterium diptheria? where specifically is it found?
humans – found on our skin and mucosal surfaces
corynebacterium diptheriae primarily affects which population?
pediatrics – their immune system isn’t as developed
true or false
corynebacterium diptheriae produces lactic acid
true
what is the MAJOR toxin of corynebacterium diptheriae
Diphtheria toxin. it is an A-B toxin (EXOTOXIN)
general question: is an A-B toxin an endotoxin or exotoxin?
exotoxin
explain in detail how diphtheria toxin works
A-B toxin
B subunit binds to EGFR on human surface (epidermal growth factor receptor)
A subunit inactivates EF-2 (elongation factor 2). doing this blocks host protein synthesis, since EF-2 is required for moving mRNA back and forth
a SINGLE MOLECULE of diphtheria toxin is enough to kill the entire cell due to the IRREVERSIBLE BLOCK of EF-2
as the cell gets destroyed, a “pseudomembrane” is produced by fibrin and the actual bacteria begin entering and replicating in the host cell. eventually, the toxin itself gets into the blood stream through the damaged cells. this is NOT bacteremia – the TOXIN is in the blood
Explain how diphtheria toxin inactivates EF-2
CATALYTIC inactivation. it doesn’t just bind to it to inhibit it.
bc of this, a single molecule of Diphtheria toxin can kill the entire cell. it is an irreversible inactivation
corynebacterium diphtheriae toxin infection is catalyzed by…
the delivery of TOXINS through the bloodstream
name the different specific clinical diseases caused by corynebacterium diphtheriae
respiratory diphtheriae and cutaneous diphtheriae
explain respiratory diphtheriae and what it can lead to if untreated
SUDDEN ONSET
occurs when corynebacterium diphtheriae colonizes the epithelium in the pharynx (causing pharyngitis)
the TOXIN is what brings about tissue damage — thick exudate is produced from this damage due to the formed pseudomembrane, white blood cells, fibrin, and debris
this exudate obstructs the airway (respiratory obstruction) and causes severe coughing which DISLODGES THE EPITHELIUM
if toxin gets into the blood and delivered to the heart, it can cause acute myocarditis
diptheria primarily affects what population?
neonates
explain cutaneous diphtheriae and what develops because of it
occurs when corynebacterium diphtheriae invades subcutaneous tissue.
pustules and ulcers develop
is there a vaccine for diphtheria?
yes
true or false
in a corynebacterium diphtheriae infection, ONLY the toxin gets into the bloodstream
TRUE
how can a neonate get corynebacteriae diphtheriae?
usually by breathing it in (respiratory diphtheriae) or by contact with an open sore or ulcer (cutaneous diphtheriae)
what is unique about listeria monocytogenes
it is capable of growing in very harsh conditions
4 degrees celsius
a wide pH range
high salt
also, it is intracellular – unique for bacteria
how is listeria monocytogenes transmitted?
by exposure to contaminated food (food poisoning)
is listeria monocyogenes gram positive or gram negative? is at aerobic or anaerobic? can it form spores? what shape is it?
gram positive rods
a facultative anaerobe (capable of producing energy with or without oxygen)
does not form spores
listeria monocytogenes is ___ _hemolytic
weakly beta hemolytic – can lyse but it takes a while
how does listera monocytogenes grow?
it is motile at what temperature?
often grows in pairs
motile at temperatures less than 37 degrees celsius
true or false
listeria monocytogenes is an intracellular pathogen
TRUE – can grow and replicate inside of host cells. this is unique to bacteria
explain how listeria monocyogenes invades
is ingested through contaminated food
then, it invades through MUCOSAL LINING of the GI tract and gets into the bloodstream to infect any neonate in the womb and cause meningitis
adheres to the host cell via INTERNALINS that bind to a host protein called E-cadherin. then, they are transported in via the GI tract M cells or enterocytes
“listeria monocytogenes”
what can you remember by looking at the name of this bacteria?
they SURVIVE when they’re engulfed by macrophages. hence the name “listeria monocytogenes”
explain HOW listeria monocytogenes can survive in macrophages
they have a toxin called LLO (listeriolysin O) which is a cytotoxin that stimulates the bacteria’s RELEASE from endosomes in the macrophage. also forms pores
listeria monocytogenes primarily infects…..
both neonates AND adults
explain the diseases that listeria monocytogenes can cause in neotnates
amnionitis
stillbirth
meningitis
meningoencephalitis
explain the diseases that listeria monocytogenes can cause in adults
flu-like illness with possible gastroenteritis
bacteremia
besides LLO, what other virulence factors does listeria monocytogenes have
Phospholipase C enzymes (2 of them) that break down the host cell membrane
ActA which induces actin polymerization
true or false
listeria monocytogenes have some capability to evade the immune system
true – through their ability to replicate when phagocytised by macrophages
As mentioned, listeria monocytogenes contains a virulence factor called ActA that stimulates actin polymerization.
what exactly does this do?
the bacteria utilize this polymerized actin to move through the host cell and even move along to infect OTHER cells
recap: how does listeria monocytogenes adhere to the host cell
through internalins that bind to E-cadhedrin on the host cell
what does listeria monocytogenes release that enables it to evade phagocytosis by macrophages?
LLO (listeriolysin O)
