Plague & Zoonoses Flashcards
Bacterial Zoonoses
Brucellosis – Brucella abortus
Plague – Yersinia pestis
Tularemia – Francisella tularensis
Infected bites – Pasteurella multocida
Brucella genus
- Gram -
- coccobacilli
- facultative intracellular
- B. abortus
B. abortus
- Coccobacillary Gram-negative rods
- Nonmotile
- Non–spore-forming
- Slow growth (2-3 days) on ordinary blood agar
- Brucella abortus
– single species
– Named variants related to animal hosts
Brucellosis Epidemiology
• Disease of large mammals (cattle, pigs, goats)
– Recurrent abortion (not in humans)
– Placenta – erythritol (also not in humans)
• Occupational exposure – farmers, veterinarians
– Abrasions, mucous membranes, inhalation
• Unpasteurized dairy products
– “Health” foods
– Imported dairy products - cheese
Brucellosis Pathogenesis
- Facultative intracellular pathogen
- Evades innate defenses
– OM lipids resemble eukaryotic composition
– Not recognized by Toll-like receptors (TLRs)
• Survives in macrophages
– Inhibit phagosome/lysosome fusion, myeloperoxidase
– Multiply in endoplasmic reticulum
– Inhibit apoptosis – prolong life of host cell
- Multiply in reticuloendothelial system - granulomas
- Seeds bloodstream much like typhoid
Brucellosis Manifestations
- Incubation 2-4 weeks
- Chronic fever, night sweats, weight loss, malaise
- Periodic nocturnal (undulant) fever in untreated cases
- Can last 1-2 years
- May have enlarged spleen or swollen lymph nodes
Brucellosis Diagnosis
•blood culture, (serology)
Brucellosis Treatment
•doxycycline + aminoglycoside
Brucellosis Prevention
•Pasteurization
Yersinia genus
- Gram -
- bacilli
- facultative anaerobe
- member of the Enterobacteriaceae
- Y. pestis
Y. pestis
- Member of the Enterobacteriaceae
- Pleomorphic with bipolar staining
- Adhesin similar to invasins of Shigella
- Yersinia outer membrane proteins (Yops)
- Virulence plasmids
– F1 antigen – protein capsule
– Multiple enzymes
•plague
Plague Epidemiology
•Disease of rodents
- Rats, prairie dogs
- Transmitted by flea bite – Fleas leave dead host
- Humans “step into” the cycle
- Flea bite leads to infected lymph nodes called bubo
- Bubonic plague
– 50-75% bacteremia
– 5% bacteremic pneumonia
• Pneumonic plague spreads human to human
Sylvatic Plague
Urban Plague
Plague: Pathogenesis Two sets of virulence factors #1
Plague: Pathogenesis Two sets of virulence factors #2
Plague Manifestations
Bubonic plague
• Bubo - 2 to 7 days from flea bite
– Fever, local pain
• Untreated 50-70% die in bacteremic shock
Pneumonic plague
- 2 to 3 days from respiratory exposure
- Cough, sputum, dyspnea, cyanosis = black death
- 100% fatal untreated (2-3 days)
Plague Diagnosis
- Smears, culture
- DFA in reference laboratories
Plague Treatment
- Streptomycin (gentamicin) +/- doxycycline
- Bubonic plague – <10% mortality
- Pneumonic plague – 10-20% mortality
Plague Prevention
- Doxycycline chemoprophylaxis
- No vaccine
Francisella genus
- Gram -
- coccobacilli
- aerobic
- F. tularensis
F. tularensis Bacteriology
- Gram-negative coccobacillus
- Requires special medium for growth
F. tularensis Epidemiology
- Direct contact with wild mammals - hunters
- Infecting dose <100 cells – minor trauma
F. tularensis Pathogenesis
- LPS not recognized by TLRs
- In macrophage resists lysosomal fusion
- Escapes to cytoplasm infecting reticuloendothelial organs
F. tularensis Manifestations
- Local ulcer depending on inoculation site
- Bloodstream spread common
- 5-30% mortality
F. tularensis Diagnosis
- Culture – special medium
- Serology
F. tularensis Treatment
•Gentamicin plus doxycycline
Pasteurella multocida
- Gram -
- coccobacilli
- facultative anaerobe
- In respiratory flora of wide range of animals
- Most common infection by bite or scratch of domestic dog or cat
- Diffuse cellulitis within 24 hours
- Culture on routine media
- Treatment – penicillin! – rare for GNR (but yes, peptidoglycans are still present in GNR cell wall)
