Plague Flashcards
Egypt in 541 AD
North Africa, Europe, central and southern Asia, and Arabia
ended in the mid-700s
Europe1320s
25 million deaths
30% to 40% of the population
Europe alone (30% to 40% of the population
China in the 1860s
spread to Africa, Europe, and the Americas
United States, with disease primarily sylvatic plague and
present in western states.
◦nonmotile, rod-shaped, facultative anaerobe with bipolar staining
- *◦safety pin appearance**
- *◦tests negative for urease, lactose fermentation, and indole**
Y. pestis
____________
◦highly virulent pathogen
◦causes the highly fatal systemic disease known plague
◦
Yersinia Pestis
◦enteric pathogens
◦relatively uncommon
◦rarely cultured from blood
Yersinia enterocolitica,Yersinia pseudotuberculosis
ability to resist phagocytic killing
◦______________-
dephosphorylate several proteins required for phagocytosis
induce cytotoxicity by disrupting actin filaments
initiate apoptosis in macrophages
suppresses cytokine production
type III secretion system
two plasmids that encode virulence genes:
1.fraction 1 (f1) gene
2.plasminogen activator (pla) protease gene
codes for an antiphagocytic protein capsule
1.raction 1 (f1) gene
degrades complement components C3b and C5a
degrades fibrin clots
.plasminogen activator (pla) protease gene
Zoonotic
Humans as accidental hosts
two forms of Y. pestis infection
1.urban plague
Rats natural reservoir
2.sylvatic plague
Causes infections in squirrels, rabbits, field rats, and domestic cats
Rats natural reservoir
1.urban plague
Causes infections in squirrels, rabbits, field rats, and domestic cats
1.sylvatic plague
◦Pigs, rodents, livestock, and rabbits
◦
Y. enterocolitica
◦Wild animals, and game birds
Y. pseudotuberculosis
◦maintained in rat populations
◦Spread among rats OR between rats (reservoir) and humans by infected fleas (vector)
◦Fleas become infected during a blood meal from a bacteremic rat
◦bacteria replicate in the flea gut
Urban plague
◦produces fatal infection in the animal reservoir
◦Infections acquired through:
Ingestion of contaminated animals
handling of contaminated animal tissues
◦human-to-human spread is uncommon
Y. pestis
◦common cause of enterocolitis
◦1 per 100,000 persons each year
◦90% of infections associated with consumption of contaminated meat, milk, or water
◦infections more common during the cold months
◦relatively uncommon cause of human disease
Y. enterocolitica
◦Flea bite
◦incubation period of <7 days
◦General malaise
◦high fever
◦Headache and chills occur suddenly at the end of the incubation period
◦painful bubo in the groin or axilla
Most flea bites will occur on the legs, so the inguinal nodes are most frequently affected (boubon is Greek for “groin”)
◦Death occurs oin less than 2 weeks
75% mortality rate
◦Gangrene
Bubonic plague
◦Incubation period 2 to 3 days
◦fever and malaise
◦Highly infectious
◦mortality rate > 90%
◦
Pneumonic plague
◦ingestion of contaminated food products(pork), unpasturized milk or water
◦Incubation period 1 to 10 days (average, 4 to 6 days)
◦diarrhea, fever, and abdominal pain that last as long as 1 to 2 weeks
Can persist for months
Y. enterocolitica
involves terminal ileum
Presentations may vary with age
Very young: febrile diarrhea (blood and pus)
Older kids/ young adults: Pseudoappendicitis
can mimic acute appendicitis if mesenteric lymph nodes enlarge
Adults: enterocolitis with postinfective sequelae like reactive arthritis
◦
◦Enterocolitis
Other manifestations
◦septicemia,
◦arthritis,
◦intraabdominal abscess,
◦hepatitis
◦osteomyelitis
◦blood transfusion–related bacteremia
can grow at 4° C
Distinguishing features
Motile at 25ºC
Non-motile at 37ºC
Cold growth
Diagnosis
◦Usually supportive care
◦Stool culture, 25ºC, cold enrichmentTreatment
What is the treatment?
◦For immunocompromised : Supportive care
Flouroquinolones or third generation cephalosporins
