Yersinia Pestis

Question 1

What did Yersinia Pestis cause?

Answer 1

PLAGUE

Question 2

How was the plague transmitted?

Answer 2

Flea bite
Direct contact wiht infected tissues
Inhalation of infected aerosols from pt with pulmonary disease

Question 3

Is Y.Pestis infections still present?

Answer 3

YES.

Question 4

What are the 2 epidemic forms of Yersinia Pestis?

Answer 4

Urban Plague: Plague maintained by rat population and spread to humans via fleas

Sylvatic Plague: Endemic in Western US and carried by prairie dogs, mice, rats, rabbits

Question 5

Describe the pathogenesis of plague

Answer 5

Organisms multiply in flea’s gut -> flea bites human/rodent -> organism move from bite site to lymph nodes-> multiply in lymph nodes-> necrosis + swelling -> BUBO -> disseminate to blood, lungs, liver and spleen

Question 6

Describe the pathologic characteristics of plague

Answer 6

Facultative Intracellular Organisms
Resist killing and multiplies in mononuclear phagocytes
Multiplies freely in EC evironment

Question 7

What is pneumonic disese from Y.Pestis characterized by?

Answer 7

Hemorrhagic pneumonia

Question 8

What is characteristic of “Black Death”

Answer 8

Terminal Cyanosis (fingers)

Question 9

What is the clinical presentation of the Bubonic Plauge?

Answer 9

Fever and painful bubo 2-7 days after bite
Sudden onset of fever chills, weakness, HA
Intense pain in region with buboes
75% mortality if untreated

Question 10

What is the clinical presentaiton of Septicemic Plague

Answer 10

Direct infection of blood by flea bite
High fever, delirium, seizures in kids, septic shock, DIC
Black Hemorrhagic splotches

High fatality rates due to delay in Dx and Tx

Question 11

How does pneumonic plague arise?

Answer 11

Hematogenous spread of plague bacillus to lungs
OR
Inhalation of infectious aerosol from pt with plague

Question 12

What is the clinical presentation of a pt with pneumonic plague?

Answer 12

Initial: HA, malaise, fever, vomiting, confusion, prostration
Later: Cough, chest pain, Hemoptysis
Eventually to sepsis and death unless treated within 1 day after onset of sx

Question 13

What category does Y.Pestis fall into?

Answer 13

Category A Bioterrorism Agent

Question 14

What is the DDx when a pt is suspected to have plague?

Answer 14

REye’s Syndrome
Tularemia
Bacterial Pneumonia
Acute Surgical Abdomen

Question 15

What should you suspect plague based on a pt’s history?

Answer 15

Febrile pts who have been exposed to rodents or mammales in known epidemic areas

Question 16

How can a bacteriologic diagnosis of the plague be done?

Answer 16

Smear and culture of bubo aspirate, blood, or sputum sample
Must notify lab of possible pestis

Shows Inc WBC and normal or low plateletcount with DIC

Question 17

What are the key identifying features of Y.Pestis?

Answer 17

Oxidase Neg
Non-Motile
Enterobacteriaceae
Bipolar Gram - Stain - coccobacilli (safety pin)
Glucose Fermenter
Slow growing colonies look like fried egg or beaten copper
Small pinpoint colonies on MacConkey
Faster growth at 28C than 37C

Question 18

How is Y.Pestis treated?

Answer 18

Streptomycin

Alternatives: Gentamicin, Chloramphenicol, Tetracyclines

Question 19

Which abx are NOT effective intreating Y.Pestis?

Answer 19

Penicillin

Cephalosporin

Question 20

WHat is given for chemoprophylaxis for Y.Pestis?

Answer 20

Tetracycline

Question 21

• A 6 Y.O. boy arrives with his mother in ER complaining of pain in right arm where a cat had bit him the previous day. The next morning the boy awoke crying and complaining of pain in his hand. Temp 39 C. Skin over the wound is erythematous. Material from the wound is submitted for culture and Gram stain. The laboratory reports growth of gram-negative coccobacilli. The organisms were faculatatively anaerobic but failed to grow on MacConkey agar. Which organisms is most likely responsible for this
infection?
A. Capnocytophaga
B. Eikenella
C. Escherichia
D. Fusobacterium
E. Pasteurella
6

Answer 21

E

Question 22

Which arthropod is the most important vector of
tuleremia?
A. House fly
B. Flea
C. Lice
D. Tsetse fly
E. Tick

Answer 22

E

Question 23

During a military conflict in Somalia, several soldiers develop a febrile illness characterized by abrupt onset of fever with rigors, severe headaches, myalgias, arthralgias, lethargy, photophobia, and coughing. Conjunctival suffusion and a petechial rash develop 4 days into the illness and then fade after 1 to 2 days at the time symptoms wane. Splenomegally and hepatomegaly are also observed. After 1 week, the symptoms recur. Blood cultures are collected during febrile
phase and are positive after extended (7 days) incubation with small, faint staining gram-negative coccobacill. What is the likely etiologic agent for this disease?
A. Brucella melitensis
B. Escherichia coli
C. Francisella tularensis
D. Haemophilus influenzae
E. Pasteurella multocida

Answer 23

a