select agents Flashcards
(26 cards)
Yersinia Pestis - The plague
gram negative rod
facultative anaerobe
non spore forming
a direct descendent of Y. pseudotuberculosis
zoonotic - still important in western US
potential agent of bioterrorism
Y. pestis encounter and entry
reservoir - rodents
can also infect: cats, dogs, bears, skunks, raccoons, humans
Y. pestis multiplication and spread
once in a mammalian host different genes are expressed that lead to:
- gene expression triggered by warmer temperature
- lower calcium concentration
phagocytosis evasion
- Type 3 secretion system (T3SS - a YOPS) - Yersinia Outer Protein
- Capsule (F1 protein)
other virulence factors (the standard Gram negative arsenal)
- LPS (endotoxin)
- siderophores
Y. pestis and fleas
commonly spread via fleas
bacterium grows in and blocks the proventriculus of certain fleas
- xenopsylla cheopis (rat flea) most common
- can infects/block ~ 80 other flea species
- ctenocephalides felis (cat flea) is NOT an efficient plague host
“blocked” fleas regurgitate a mix of host blood and Y. pestis
- whole cycle takes ~ 2 weeks
Y. pestis damage
3 patterns of disease in animals and humans
- bubonic (least deadly) –> lymphadenopathy and fever
- septicemic (moderately deadly) –> bacteremia and sepsis
- pneumonic (most deadly–> bromchopneumonia
- Spread by aerosol
- contagious without fleas
- can also get secondary pneumonic - hematogenous spread to lung
cats and dogs prone to bubonic form, pneumonic can occur but difficult to identify
should be a rule out in endemic areas
francesella tularensis encounter
infected animals (lags, rodents)
contaminated soil and water, contaminated by carcasses
mechanical transmission via arthropods - - ticks amblyomma, dermacentor, others, biting flies
plague diagnosis
is reportable
contact lab before sending suspect plague samples
PCR (blood, lymph node aspirate, trachael wash, post mortem liver lung spleen)
aerobic culture
- 48 hours
- lab must confirm identification
immunodiagnostics
- FA
- IFA
- CF
plague treatment
doxycycline
fluoroquinolones (ciptofloxacin, enrofloxacin)
aminoglycosides - sometimes, be careful with them
francisella tularensis
a gram negative coccobacillus
non spore forming
aerobic nonfermenter, fastidious/difficult to culture
capnophilic
facultative intracellular
zoonotic
potential agent of bioterrorism
causes disease “tularemia” AKA rabbit fever AKA lawnmower pneumonia
francesella transmission cycle
has botoh terrestrial (sylvatic) and aquatic cycles
type A vs Type B tularemia, type A is more virulent
tularemia entry
arthropod bites
ingestion
inhalation
direct contact
highly infectious with ID50 of <10 CFU in humans and cats
- this and its ability to cause fatal pneumonia are why its listed as a select agent
tularemia pathogenicity
depends on route of exposure and immune status
lymphadenopathy
ulcerglandular - dermatologic signs + lymphadenopathy
bronchopneumonia
typhoidal - hepatosplenomegaly
oculogandular - conjuctivitis and lymphadenopathy
intestinal
organism survives in macrophages by escaping phagolysosomes
replicates in the cytosol of macrophages
tularemia diagnosis
PCR - LN aspirates, liver/spleen aspirates, trachael wash, blood
aerobic culture - fastidious, requires cysteine enrichment (Chocolate agar)
serology - FA agglutination tests
post mortem - multifocal granulomas in liver - biohazard level 3
if you live in an endemic area should be on your list
tularemia tx and control
cats and dogs
- docycycline
- fluoroquinolones
limit wildlife exposure
wear PPE if suspected
- goves, eye protection
- N95 respirator or powered air purifying respirator (PAPR))
report to state public health lab
- may recommend post-exposure prophylaxis and/or fever watch
bacillus anthracis
LARGE - 5X larger than most bacteria
gram postive rods
facultative anaerobes
include:
- B. anthracis (anthrax)
- B. cereus
- B. thuringiensis
- B. subtilis
B. anthracis encounter and entry
the SPORE is the infectious form
- contaminated soil spores can survive for decades or longer)
- infected animals/carcasses
entry via:
- wounds
- ingestion
- arthropod bites
- inhalation
B. anthracis multiplication/spread
happens FAST
spores germinate in mononuclear cells
vegetative cells escape the phagolysosome
RAPID expansion of cells in blood and tissue
systemic spread
- 10^9 organism/ml in blood!
B. anthracic damage
all major virulence factors are EXOTOXINS and are encoded by PLASMIDS
lethal toxin/factor: causes apoptosis, pulmonary edema, shock (on plasmid PX01)
edema toxin/factor: elevates cAMP in cells causing varying effects
- inhibits PMN function
protective antigen: works with lethal factor and eema factor to act as complete toxins
capsule: allows to evade phagocytosis (on plasmid pX02)
net effect: increased vascular permeability and tissue necrosis
anthrax spectrum of disease
peracute septicemia - ruminants
acute septicemia - horses
pulmonary disease - humans - woolsorters disease
intestinal disease - humans, pigs, horses
cutaneous disease - humans - malignant carbuncle
anthrax in ruminants
suspect anthrax in a ruminant BEFORE YOU OPEN A CARCASS IF:
- there is a lack of rigor mortis
- there is a lack of blood clotting
- if blood is coming from orifaces
anthrax epidemiolgy
risk factors:
alkaline, calcium, nitrogen rich soils
history of anthrax in the area
flood and drought cycles
- soil rearrangement
-grazing close to the ground with more soil ingestion
a problem in canadas NWT bison
spores may be thawing out of permafrost…
anthrax diagnosis
is reportable
real time PCR is preferred - use qualified laboratory
aerobic culture and ID via PCR or bacteriophage - y susceptibility
presumptive - stained blood smears with polychrome methylene blue stain
- chains of “boxcar” shaped organisms with pink capsule
B. anthracis culture
very recognizable
- medusa head
- ground glass
non hemolytic
B. anthracis tx and control
antimicrobials must be given early
- penicillins, tetracyclines - may be used in all species
control
- vaccination of healthy animals in endemic areas during high risk conditions such as droughts
-live vaccine - less virulent
- strain lacks PX02 that encodes capsule (sterne strain)
