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22 Cards in this Set

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  • Back
Are bacteria in the genus bacillus gram +/-? Are they catalase +/-?

What do the genomic islands lead to?

What was this group the first for Pasteur to make into?

What is the big disease associated with this genus?
Anthrax- an ancient disease

One of the Egyptian plagues, recorded by ancient Greeks.

The first “germ” identified by Koch- Bacillus anthracis.

One of the first live __attenuated vaccines__- Pasteur

Gram-positive, aerobic or fac. anaerobic, spore-forming bacteria.

Forms __Chains of long rods___. _Spores__ are often evident in the chains

Catalase positive, most are motile (not B. anthracis)

Note that Bacillus cereus, Bacillus anthracis, and Bacillus thurigensis
are genetically very similar. Genomic islands lead to __phenotypic diversity__
What is the special stain for Bacillus spp?
Spore stain
How can bacillus spores stay alive so long?
Ancient bacteria trapped in a state of suspended
animation for 250 million years are the world's oldest
living things, claim US scientists.The microbes are ten
times older than any previously discovered living
organism and may reopen the debate about the origins
of life on Earth.
Bacillus spores- alive...after 250 million years
What are the three types of human infection by anthrax?
In humans, cutaneous anthrax is unique and easily
identifiable by people looking for it….. Most
environmentally acquired infections are cutaneous.

Inhalation anthrax is a different story- symptoms
nonspecific: people often die just after the disease is
diagnosed.

Intestinal anthrax: highly fatal- death occurs 2-5 days post
ingestion of contaminated animal products. Humans or
animals can suffer the same disease.

Bacteria are transferred across the intestinal membrane and
systemic disease occurs. Symptoms often are nondescript.

Can also cause hemorrhagic meningitis- toxemia

Easily treated with antibiotics if caught early.
What is an eschar?
A cutaneous anthrax lesion - is it just anthrax?
How common are human anthrax infections?
Very uncommon - the deadly kinds are highly unlikely to be transmitted. The one that can be seen are highly treatable.

In 2006 a person working with untreated animal
skins died of anthrax in the U.K.

The last person to die of naturally acquired
anthrax in the US was a home weaver working
with hides from Pakistan.

Natural anthrax examples:

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5032a1.htm

http://www.paherald.sk.ca/index.cfm?sid=156563&sc=4

http://www.ph.ucla.edu/epi/Bioter/anthraxhidescattletrail.html

http://www.ncbi.nlm.nih.gov/pubmed/10475947

Anthrax and bioterror:

http://www.washingtontimes.com/news/2009/jul/30/lessons-learned-from-
the-anthrax-letters/
What species are susceptible to anthrax infection?

What do the carcasses look like?
May be very
_bloated_ upon death.
Omnivores,
carnivores 
apparently less susceptible.

Ruminants very susceptible, horses, people too.

Dead animals may have _fluids__ exuding from nose,
mouth, anus.

These carcasses need to be buried on the spot, 6 feet deep - no burning, no culturing, no moving, it is far too contagious at this point.

Orofices exude a dark tarry blood. Blood won’t clot. 
Edema fluid, peripheral blood smear, stain on site if possible. _culture_ is important for confirmation.
Gram pos. rods, spores, capsule.
Disposal of carcasses should always involve incineration.
Should be on site.
Burial of carcasses can lead to long term spore persistence- in
presence or absence of lime.
Burial of dead cows: worms can bring anthrax to the surface
(Pasteur).
Anthrax plasmids have two plasmids. What does this give them?

What does it give us?
Anthrax plasmids- examples of __pathogenicity islands_.

Strains lacking one of the plasmids are _avirulent__.

Capsule-less strain- _Stern's_ vaccine strain. Get rid of the capsule, you also make the bacteria avirulent.
How does the anthrax capsule work?
Polyglutamic acid
capsule-
antiphagocytic

Synthesis pathway encoded by virulence plasmid pOX2
Anthrax has A and B subunits - what is that called? What is special about their subunits?

Are they coded on the same plasmid?
Bipartite

_AB toxin __, consists of one B subunit, but two _different__ A
subunits

B subunit- __protective_ antigen (PA)

A subunits:

_edema__ factor (EF)- targets calmodulin-dependent adenylate
cyclase.

__lethal_ factor (LF)- serine proteinase that affects host cell
cytokine release. May be critical in Anthrax-associated sepsis.

Encoded by virulence _plasmid_ pOX1
What does anthrax edema factor target?

What does lethal factor target?
Cell signalling

Interferes with cytokine release
What are the two attenuated strains of anthrax?

What are the structural differences?
Pasteur strain- __encapsulated__, lacks toxin genes.!
Sterne strain- not encapsulated, contains __toxin genes__.!
Sterne strain, sold as a live spore prep, is a standard veterinary
vaccine. Injectable.!
What is the poor man's weapon?
Bioterrorism.

Costs per fatality are far less than high tech weapons.
What do you need to know about anthrax?
Ruminants
Humans
zoonotic dz
spores
What does bacillus cereus cause?

Is it a spore former?
Bacillus _cereus_
_food infections__/intoxications in people!
Gangrenous mastitis in cattle!
Rare abortions in cattle sheep and horses.!
Another _soil inhabiting__ spore
former.!
How do Rhodococcus organisms gram stain?
Short gram positive rods.
What kind of bronchopneumonia does rhodococcus equi cause?

How often does it lead to intestinal infection?
Chronic suppurative _bronchopneumonia__ of foals!
Serious problem in foals 1-6 months of age- worldwide
distribution.!
Slow developing_pneumonia__- easy to miss in the early stages!
May progress to a rapid, very serious condition with no
warning.!
About 1/2 have __intestinal infection_- usually not diagnosed
until post mortem. Ulcerative enterocolitis, granulomas,
purulent inflammation of lymph nodes.!
Bacteremia can lead to sepsis, systemic infection.!
Mortality can be quite high.!
What are the rhodococcus virulence factors?
Survival inside of macrophage is a key element of virulence.!
Pathogen is taken up and then can kill the macrophage.!


IMPORTANT
What is plasmid-associated virulence?
_soil borne__ organism. Very common in soil and in
equine intestinal material/fecal matter. The vast majority of
isolates found in soil do not carry a large plasmid.!
Isolates causing disease all carry a large __plasmid__.!
Also siderophore positive.!
How does the rhodococcus plasmid play into virulence?
Rhodococcus pathogenicity island- plasmid
absolutely required for virulence!
What are rhodococcus plasmid genes regulated by? What is the signifigance?
Regulated by temperature.

Signifigance is that when in the host and the temp changes, gene regulation is upregulated in response.
Why does rhodococcus equi only infect foal, not adults?
R. equi is a soil organism- adults pick the pathogen up from grass and the carriage is passive- no bacterial growth. Young horses, however, harbor actively growing R. equi- up to 100,000 per gram of feces. Unknown aspects of immunity are apparently protective in adults.
Acquired protection against disease is likely cell-mediated, but hyperimmune sera administered IV is protective in foals.