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Bacteriology-52 Yersinia, Brucella, Francisella*


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What is the agent of plague
Yersinia pestis
What is the agent of Brucellosis
Brucella species
What is the agent of tularemia
Francisella tularensis
What kind of bacteria are Yersinia pestis, Brucella spp, and Francisella tularensis
Gram negative rods that cause systemic, zoonotic infections
What are the three types of plague caused by Yersinia pestis
Humans are incidental in the rodent-flea cycle
What are the general characteristics of Yersinia pestis
Gram negative coccobacillus with bipolar staining
Facultative intracellular that grows within the phagolysosomes of macrophages
Not fastidious, optimal growth 28C, but virulence traits expresses at 37C
How do humans become infected with Yersinia pestis
Sylvatic transmission with chipmunks, praire dogs, and squirrels. Most common
Urban plague (rat to flea)
What disease presents with high fever, tachycardia, malaise, aching of extremities, and painful bubo (tender, enlarged lymph node)
Bubonic plague. Most untreated patients progress to bacteremia and die of Gram-negative septic shock soon after developing bubo
What disease presents only with fever, malaise, and a feeling of tightness in the chest. Productive cough, dyspnea, and cyanosis develop later
Pneumonic plague. Develops in a few with bubonic plague as a secondary pneumonia caused by bacteremic spread to the lungs. Human to human can occur. Can't survive without therapy
Transmission of Yersinia pestis is enhanced by what
Hemin storage locus (hms) gene, which encodes a factor that causes blockage in the foregut of the flea
What are the virulence factors of Yersinia pestis
Capsular antigen (fraction 1): antiphagocytic
V antigen: plasmid encoded. Induced by low calcium levels
Yersinia outer membrane proteins (YOPs): plasmid encoded, inhibits phagocytosis by macrophages
How is Yersinia pestis treated
Streptomycin and tetracycline. Vaccine also available
What is Brucellosis
Disease of domestic animals, never human to human. Propensity to localize in pregnant uterus and mammary glands. Growth factor erythritol
What are the characteristics of Brucella
Slow-growing, fastidious gram negative rods. Facultative intracellular parasites of the RES. Cause chronic infections
What species of Brucella cause disease in humans
B. melitensis (goats)
B. abortus (cattle)
B. suis (swine)
How are Brucella species differentiated
Whether they need CO2 for growth (B. abortus), inhibition of growth, slide agglutination
What causes Malta fever
Brucella melitensis
How is Brucella transmitted to humans
Eye, nasopharynx, skin, or cut after contact
What are the complications of Brucella infection
Arthritis is the most common; reproductive tract infections (epididymitis, orchitis, and abortion)
What type of immunity is protective against Brucellae
Cell-mediated immunity
How is Brucella treated
Intracellular organism, so doxycycline and rifampin. Vaccines for animals exist
What causes Tularemia
Infection with Francisella tularensis
What are the characteristics of Francisella
Gram negative coccobacilli, fastidious, grows slowly.
Facultative intracellular for macrophages
Very low infectious dose. Point of entry may not be apparent
Tularemia, caused by Francisella tularensis, can manifest as what
Skin lesions, pneumonic, gastrointestinal, ocular, and systemic
How is Tularemia, caused by Francisella tularensis, acquired
Direct contact with infected animals or bites of infected insects
What are the four major clinical manifestations of Francisella infection
Ulceroglandular: follows primary infection of skin. Fever, headache, malaise, bubo
Pneumonic: aerosols
Typhoidal: ingestion; typhoidal-like illness
Oculoglandular: contaminated eye with infected material
How is Francisella acquired
Direct contact with infect animals (hunter, vets) or bites of infected insects
What specific media is needed to culture Francisella
Cysteine-enriched. Lab must be alerted of potential diagnosis
What type of immunity is important for Francisella infection
Cell-mediated immunity. Vaccine availabe

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