Anthrax, Plague, Viruses Flashcards
Anthrax: Gram +/-? Aerobic/anaerobic? Spore/non-spore former? Cocci/rods? How does it appear on the microscope?
Gram + Aerobic/facultative anaerobic Spore forming Rod Forms long filaments/chains
What type of diseases can Bacillus cause?
Cereus (food poisoning)
Anthracis: anthrax.
Virulence factors of Bacillus anthracis? Toxins?
- CAPSULE: Poly D-glutamic acid (unique!!! different from the polysaccharide capsule of others)
- Edema toxin (A subunit)
- Lethal toxin (A subunit)
- Protective antigen (B subunit - binds cell)
What is edema factor
A calmodulin dependent bacterial adenylate cyclase: increases cAMP resulting in edema.
What is lethal factor
A zinc-metaloprotease that cleaves mitogen activated protein kinase kinase (MAPKK) => inhibits signal transduction pathway in macrophages.
What is protective antigen? How does it work?
Protective antigen binds to cell, forming a 7-mer or 8-mer - then EF or LF binds to it and can enter the cell.
Where is the reservoir of anthrax?
Soil
What are the disease forms of anthrax?
- Cutaneous: forms a painless black eschar with edema. MOST COMMON. 80-90% complete resolution.
- Gastrointestinal: RARE. Causes ulcers at site of invasion = hemorrhage.
- Inhalational: incubates 1-43 days, results in nonspecific symptoms for 3-5 days. defined by HEMORRHAGIC MEDIASTINITIS
How do you treat anthrax?
60 day regiment:
ciprofloxacin or doxycycline
+ clindamycin
+ rifampin
antibodies do not kill the spore = thus the long treatment
What is the vaccine for anthrax?
Biothrax
Inactivated vaccine of protective antigen (PA)
one intramuscular dose at 0, 4 weeks, then 6, 12, 18 months.
Requires yearly boosts
What is the bug that causes bubonic plague?
Yersinia pestis
Yersinia pestis: Gram +/-, cocci/rod? What does it grow on? what can you stain it with to confirm diagnosis?
Gram - rod, grows well on MacConkey’s agar.
Stains with Wayson stain = appears light blue bacilli with darl blue polar bodies (fluorescent)
What is the mode of transportation of yersinia pestis?
flea - except for pneumonic plague.
What are the viral agents that are listed in Category A of bioterrorism?
Smallpox
viral hemorrhagic fevers (filoviruses - ebola/marbur and Arenaviruses like Lassa Fever)
What is the viral agent that is listed Category B of bioterrism?
Viral encephalitic agents (alphaviruses such as VEE)
What are the viral agents that are listed in Category C?
These are emerging pathogens:
- henipaviruses (nipah virus, hendra virus)
- tick-borne encephalitis virus
- Tick-borne hemorrhagic fever viruses such as Crimean-congo Hemorrhagic fever
- Yellow Fever
What is Viral Hemorrhagic Fevers?
These groups of illnesses causes overall damage to the vascular system, resulting in hemorrhage.
What are the common presenting signs of a viral hemorrhagic fever?
- malaise
- myalgia
- prostration
- bleeding = lots of bruises. More vascular damage than life-threatening volume loss.
What are some examples of viruses that can cause viral hemorrhagic fever?
Arenaviruses: Lassa Fever
Bunyaviruses: CCHF, Hantavirus
Filovirus: Ebola, Marburg
Flavavirus: Yellow Fever
What are the properties of viruses that cause viral hemorrhagic fevers? eg - type of virus? reservoir? location? cure/treatment?
- they are all enveloped RNA viruses
- Thus, their survival is dependent on a host
- they are generally geographically restricted based on their host
- There is no cure or establised drug treatment
What are the differential diagnosis of a viral hemorrhagic fever?
consider Bacterial (tyhoid fever, rickettsiosis), Protozoa (falciparum malaria), Others: (HUS, heat stroak, vasculitis).
What is the typical patient history of a patient with viral hemorrhagic fever?
- foreign travel to endemic/epidemic areas
- rural environments
- contact with arthropod or rodent reservoir
- domestic animal blood exposure
What are some treatments for patients presenting with viral hemorrhagic fever?
SUPPORTIVE CARE
- coagulopathies?
- Ribavirin - only for arenaviruses and bunyaviridae (CCHF, Hantavirus, RVF). Tpically used for HCV and for RSV.
which viruses that cause VHF currently have vaccines?
- Yellow Fever: Yellow fever 17D
2. Argentine hemorrhagic fever/Junin virus: Candid #1
Filoviruses: Ebola/Marburg. What are the key structural elements?
-SSRNA enveloped viruses that appear filamentous and CURLY
What is the natural reservoir of ebola?
Bats, mostly seen in Africa
Crimean-congo hemorrhagic fever (CCHF): transmission?
TICKS
Crimean-congo hemorrhagic fever (CCHF): key structural elements?
This is a bunyavirus: circular genome, ambisense RNA (+ and -) divided into three parts small, meddle, and large.
Arenaviruses: Lassa fever and S. american Hemorrhagic fevers. How are these transmitted?
RATS: contact with rat excretia, ingestion of contaminated food, direct contact with broken skin, inhalation of tiny particles.
Arenaviruses: Lassa fever and S. American Hemorrhagic fevers: how do these appear microscopically?
grainy appearance due to presence of ribosomes from their host cells (arena = sandy in latin).
Symptoms of Lassa Fever
Flu-like symptoms, HEARING LOSS, facial swelling, sore throat, v/d - varied and nonspecific symptoms. Death rates higher in pregnant women especially in third trimester (Lassa virus also causes abortions) “SWOLLEN BABY SYNDROME”
Treatment of Lassa fever
Ribavirin
Hyperimmune serum
Prevention of Lassa fever
RODENT CONTROL
no vaccine available.
Paramyxoviruses: Hendra and Nipah viruses: what animals? What receptors are used to enter the cells?
This is a zoonotic and highly pathogenic virus that originates from bats but can infect pigs, horses, dogs, cats, hamsters, ferrets, monkeys and humans.
These have a broad tropism: ephrin B2/B3 as receptors
What are the symptoms of a Nipah/Hendra infection?
Widespread multisystem vasculitis: thrombosis, ischemia, necrosis.
Especially at the brain, lungs and spleen
Can cause a severe respiratory disease (ARDS like?) and/or acut encepahalitis.
Bloody froth at the mouth
Poxviruses: how does this appear microscopically?
LARGE - can see with simple light microscopy as a brick-shaped particle. Has a complex outer envelope.
What are the structural properties of Poxviruses?
LARGE - complex outer shell, with DNA virus that REPLICATED IN THE CYTOPLASM. It is very resistant to inactivation (can remain viable in crusts for years at room temperature)
How did ppl in the past become immunized to smallpox?
they got cowpox! “Fair as a milkmaid” = would get a small pox on their fingers, but be immune to smallpox
How are we able to eradicate smallpox from the US?
Because:
- there is no animal reservoir
- there are very few sterotypes
- there is an effective vaccine
- There is no subclinical infection
What are the clinical signs of smallpox? verses chicken pox?
First fever, then 2-4 days after, rash appears - papules => fluid filled vesicles. All of these papules will be at the same stage of development (different from chicken pox where pustules can be at different stages).
Small pox can appear all over the body, but will favor which part of the body? compared to chickenpox?
Smallpox pustules are denser on the face, arms, hands, legs and feet rather than the trunk/body. Involves the palms and soles.
Chickenpox rarely involves the hands/sole of feet.
How do you diagnose chickenpox? what are the key microscopic features you look for?
Stain with gentian violet = look for GUARNIERI BODIES (typical inclusion bodies)
Electron microscopy: Shows cytoplasmic inclusions and brick shaped virions
Egg inoculation: shows specific pock morphology on chorioallantoic membranes
PCR.
What are some complications of the smallpox vaccine?
can auto-inoculate (touch pox vaccine => eye = BAD)
can have generalized vaccinia (body wide dermatitis reaction instead of one pox rnx), eczema vaccinatum (seen in ppl with chronic granulocytic leukemia - spreading red rash from vaccine site) , post-vaccination encephalitis, etc.
