Lecture 6 - Hemotropic mycoplasmas, Francisella tularensis, and Yersinia pestis

What are the morphology and structure of mycoplasma?

-Highly pleomorphic but typically cocci

-Smallest known bacteria

What is important about mycoplasma cell wall and membrane?

-Lack cell wall (cannot use antibiotics that target cell walls)

-Contain triple layered cytoplasmic membrane

What are mycoplasma growth and colony characteristics?

-Colonies are usually small and require magnification

-Have a fried egg appearance

-Difficult to culture from clinical specimens (need rich media)

What are the common transmission methods for hemotropic mycoplasma?

-Vectors (fleas, ticks, mosquitoes)

-Blood

-Verticle transmission

What is the pathogenesis of hemotropic mycoplasmas?

Invade and damage RBCs

What are the signs, transmission, and pathogenicity in mycoplasma suis?

-Signs: anorexia, weakness, listlessness, anemia, pale mucous membranes, occasionally icterus

-Transmission: Inoculations, in utero infection

-Pathogenicity: adhesion, invasion, hemolysis, eryptosis, coagulation

What is the disease caused by mycoplasma hemofelis? What are the signs and transmission

-Disease: feline infectious anemia

-Signs: anemia, weakness, pallor, tachypnea, tachycardia, fever

-Transmission: vectors

How do mycoplasma infections cause cell damage?

-Cell lysis

-Scavenger enzymes

-Immune response (inflammation, autoreactivity)

What are three ways that mycoplasma can persist?

-Intracellular survival

-Attachment to cell surfaces

-Biofilm formation

How do mycoplasma evade the immune response?

-Molecular mimicry (glycolopids similar to host)

-Antigenic variation - trick immune system into thinking it’s a different infection

How is hemotropic mycoplasma diagnosed?

-PCR

-Microscopy

-Culture

How are hemotropic mycoplasmas treated and prevented?

-Treatment: tetracyclines, glucocorticoids (for hemolysis), blood transfusion

-Prevention: flea meds/insect repellant, screen blood donors

What disease does Francisella tularensis cause? What are two important subspecies and where are they found

-Tularemia

-Subspecies: tularensis (north america) and holarctica (europe and asia)

What is the morphology and growth of francisella tularensis?

-Small gram (-) coccobacillus

-Facultative intracellular parasite

-Strict aerobe

-Fastidious

How is Francisella tularensis transmitted?

-Reservoirs: small wild mammals

-Vectors

-Contact or ingestion of contaminated animals or water

-Inhalation of airborne organisms

What is the pathogenesis of Francisella tularensis?

-Targets macrophages, dendritic cells, neutrophils, hepatocytes, and lung epithelium

-Capsule to evade immune system

-LPS (Prevent TLR recognition)

-Type IV pili for adherence

-Acid phosphatase for survival in macrophages

How is Francisella tularensis diagnosed? What should you do if you suspect it?

-Clinical presentation, culture, serology, PCR

-If suspected, notify lab (bioterrorism potential)

How is Francisella tularensis treated and prevented?

-Treatment with enrofloxacin

-Prevention with isolation

What disease is caused by Yersinia pestis? Where in the US is it present?

-Bubonic plague

-Present in southwest US

What is the morphology and growth of Yersinia pestis?

-Gram (-) coccobacillus

-Facultative anaerobe

-Fried egg colony

How is Yersinia pestis transmitted?

-Reservoir: rodents (chipmunks, mice, prairie dogs)

-Vectors (fleas)

-Ingestion of infected animals

-Contact with contaminated soil

-Respiratory droplets

What are the clinical signs of Yersinia pestis?

Lethargy, fever, inappetence, swollen lymph nodes, vomiting, depression, dehydration, oral lesions

What are the three types of disease presentation of Yersinia pestis? What is the classic sign of each?

1. Bubonic plague - swollen lymph nodes

2. Pneumonic plague - pneumonia

3. Septicemic plague - blood infection causing necrosis on fingers, toes, and nose

What is the pathogenesis of Yersinia pestis?

-Targets macrophages and other immune cells

-Serum resistance (complement inhibition)

-Avoids PAMPs

How is Yersinia pestis diagnosed?

Culture, PCR, microscopy

How is Yersinia pestis treated and prevented?

-Treatment: streptomycin or gentamicin

-Prevention: isolation, rodenticide, flea control