Plague & Zoonoses

Question 1

Bacterial Zoonoses

Answer 1

Brucellosis – Brucella abortus

Plague – Yersinia pestis

Tularemia – Francisella tularensis

Infected bites – Pasteurella multocida

Question 2

Brucella genus

Answer 2

• Gram -
• coccobacilli
• facultative intracellular
• B. abortus

Question 3

B. abortus

Answer 3

• 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

Question 4

Brucellosis Epidemiology

Answer 4

• 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

Question 5

Brucellosis Pathogenesis

Answer 5

• 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

Question 6

Brucellosis Manifestations

Answer 6

• 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

Question 7

Brucellosis Diagnosis

Answer 7

•blood culture, (serology)

Question 8

Brucellosis Treatment

Answer 8

•doxycycline + aminoglycoside

Question 9

Brucellosis Prevention

Answer 9

•Pasteurization

Question 10

Yersinia genus

Answer 10

• Gram -
• bacilli
• facultative anaerobe
• member of the Enterobacteriaceae
• Y. pestis

Question 11

Y. pestis

Answer 11

• 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

Question 12

Plague Epidemiology

Answer 12

•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

Question 13

Sylvatic Plague

Answer 13

Question 14

Urban Plague

Answer 14

Question 15

Answer 15

Question 16

Plague: Pathogenesis Two sets of virulence factors #1

Answer 16

Question 17

Plague: Pathogenesis Two sets of virulence factors #2

Answer 17

Question 18

Plague Manifestations

Answer 18

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)

Question 19

Plague Diagnosis

Answer 19

• Smears, culture
• DFA in reference laboratories

Question 20

Plague Treatment

Answer 20

• Streptomycin (gentamicin) +/- doxycycline
• Bubonic plague – <10% mortality
• Pneumonic plague – 10-20% mortality

Question 21

Plague Prevention

Answer 21

• Doxycycline chemoprophylaxis
• No vaccine

Question 22

Francisella genus

Answer 22

• Gram -
• coccobacilli
• aerobic
• F. tularensis

Question 23

F. tularensis Bacteriology

Answer 23

• Gram-negative coccobacillus
• Requires special medium for growth

Question 24

F. tularensis Epidemiology

Answer 24

• Direct contact with wild mammals - hunters
• Infecting dose <100 cells – minor trauma

Question 25

F. tularensis Pathogenesis

Answer 25

* LPS not recognized by TLRs * In macrophage resists lysosomal fusion * Escapes to cytoplasm infecting reticuloendothelial organs

Question 26

F. tularensis Manifestations

Answer 26

* Local ulcer depending on inoculation site * Bloodstream spread common * 5-30% mortality

Question 27

F. tularensis Diagnosis

Answer 27

* Culture – special medium * Serology

Question 28

F. tularensis Treatment

Answer 28

•Gentamicin plus doxycycline

Question 29

Pasteurella multocida

Answer 29

* 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)