Exam #8: Zoonotic & Vector Borne Bacterial Infections I Flashcards
How is zoonosis prevented & controlled?
1) Avoidance of reservoirs and vectors
2) Eradicate reservoir or vector
3) Proper sanitation
*Note that vaccines are generally not feasible due to low incidence.
List the zoonotic bacteria that are considered bioterrorism agents.
- Anthrax
- Brucellosis
- Meliodosis
- Tularemia
- Plague
List the characteristics of Anthrax.
Anthrax is caused by Bacillus anthracis
- Gram positive rods
- Aerobes
- Spore-forming (remain viable for decades)– green spore
- Appear in long chains with squared ends
“Boxcar” in culture
What virulence factors is associated with Anthrax?
- Protein capsule, which is unique–others are polysaccharide
- Protective antigen (like B) with either Lethal toxin or Edema toxin associated with it
What is the function of protective antigen?
Acts like B-subunit, binding
What is the mechanism of Lethal Toxin?
Disrupts normal cellular signaling events, leading to cell death, inflammation, and tissue damage
What is the mechanism of Edema Toxin?
Activates adenylate cyclase, increases cAMP, changes osmotic gradients, and ultimately leads to edema
Describe the pathenogenesis of Anthrax.
- Spores are inoculated, ingested, or inhaled
- Spores germinate into cells that produce toxin
- Protective antigen binds cellular receptors on host tissues and cells
- Protective antigen is then activated by host cell enzymes to form a multimeric complex on the host cell surface
- LF or EF bind this complex & are internalized by the cell
What is Anthrax a primary disease of?
Herbivores: Cattle, sheep, goats, and horses
*This can be cultured on almost any farm; animals and soil are the principal reservoirs but there are only 1-2 cases anually
How is Anthrax prevented?
Vaccine in both animals and humans
What are the three types of Anthrax disease?
1) Inoculation
2) Inhalation
3) Ingestion
What is inoculation anthrax?
Direct inoculation of spores into open cuts or wounds
- Spores from soil, animal fur, hides, wool, or skin
What is inhalation anthrax?
Inhalation of spores
- Bioterrorism
- Previously called “wool-sorters disease”
What is ingestion anthrax?
Ingestion of spores
Describe the progression of Cutaneous anthrax.
1) Small red papule
2) Vesicle
3) Necrotic ulcer (eschar) is formed
*Described as painless & 5-20% are fatal without treatment
Describe the presentation of inhalation anthrax.
1) Initially presents as non-productive cough, dyspnea, myalgia, fatigue, and fever
2) Progresses to fever, drenching sweats, & severe dyspnea/cyanosis
3) By 3rd day, death in 100% without treatment
*Note that there is a long incubation period; pneumonia is rare; meningeal symptoms are in half of the cases
Describe the presentation of gastrointestinal anthrax.
1) Upper GI involvement includes oro-pharyngeal ulcerations with cervical lymphadenopathy & fever
2) Intestinal involvement includes abdominal pain, nasuea, fever, hematemesis, & hematochezia
*Note that the fatality rate with this disease is ~100%
How is gastrointestinal anthrax acquired?
Ingesting contaminated meat (likely with black eschar)
How is anthrax diagnosed?
- Clinical signs
- History
- Microscopy
- Culture
*Must inform lab that anthrax is suspected & handled under certain containment conditions
How is cutaneous (non-bioterrorism) anthrax treated?
Amoxacillin
How is inhalation, gastroinestinal, or bioterrorism anthrax treated?
- Doxycycline or Ciprofloaxcin with 2x additional antibiotics
What is is causative organism of Brucellosis?
Brucella
List the characteristics of Brucella.
- Gram negative coccobacilli
- Intracellular pathogen
*Requires specialized media for culture
How is Brucella transmitted?
Aerosol or ingestion of
- Contaminated food
- Direct contact with infected animal
Describe the presentation of Brucellosis.
- Acute undulating fever with joint pain, headache, & drenching sweat
- This daily undulating fever is pathognomonic for Brucella/ Brucellosis
*Fever starts in the evening and is normally done by the morning
What does Brucella infection cause during pregnancy?
Spontaneous abortion
Premature delivery
Miscarriage
*Because of this, lab must be notified if this is what you suspect the patient may have
How is Brucellosis diagnosed?
- Patient history
- Lab MUST be notified
- Blood culture
- Serology
- PCR
What is the treatment for Brucellosis?
6+ week course of Tetracycline (doxycycline) & rifampin
How is Brucellosis prevented?
- Quaratine & vaccination of cattle, pasteuization of milk
- Avoidance of imported unpasteurized soft cheeses/ home-made cheese
- Better laboratory practices
*Note that Brucellosis is the #1 lab acquired infection
What organism causes Pasteurellosis?
Pasteurella multocida
List the characteristics of Pasteurella multocida.
- Gram negative coccobacilli
- Anaerobe
- Commensals or normal flora in dogs & cats
- Easy to culture
What are the virulence factors associated with Pasteurella multocida?
LPS
HA capsule
How is Pasteurellosis typically transmitted?
- Infections commonly occur following the bite or scratch of a cat or dog
- Also, letting dogs “lick” wounds
Describe the presentation of Pasteurellosis.
- Redness & swelling around the wound that becomes painful
- Cellulitis and abscess formation
- Lymphadenopathy
- Possible spread to tendons, joints, and bones if untreated
How is Pasteurellosis diagnosed?
- Clinical signs
- Hx of exposure
- Culture and biochemical testing
How is Pasteurellosis treated?
PCN
What organism causes Leptospirosis?
Leptospira interrogans
List the characteristics of Leptospira interrogans.
- Thin, motile gram-negative spiral shaped bacterial with terminal hooks
- Slow growth in culture
- Poor staining
Describe the pathogenesis of Leptospira interrogans.
1) Organism invades abraded skin or intact mucous membranes
2) Enters bloodstream & disseminates
What is the clinical presentation of Leptospirosis?
Most infections present as self-limited, non-specific febrile illness
Where is Leptospirosis most prevalent?
- Most prevalent in the tropics
- Cases in the US are seen mostly in Hawaii
- Infection develops after exposure to contaminated animal urine or contaminated water
What are the two phases of Leptospirosis?
1) febrile influenza-like illness
2) Disseminated phase if infection is not resolved
- Meningitis
- Eye infection
- Jaundice
- Renal failure
- Rash
How is Leptospirosis diagnosed?
- Hx
- Culture is v. difficult
- Serology is employed to confirm infection
How is Leptospirosis treated?
PCN
Ampicillin
How is Leptospirosis prevented?
Limiting exposure to animal urine
What is the causative organism of Tularemia?
Francisella tularensis
List the characteristics of Francisella tularensis.
- Small, slow-growing, aerobic, Gram-negative coccobacilli
- Difficult to grow in culture
- Intracellular pathogens of monocytes & macrophages
What virulence factors are associated with Francisella tularensis?
LPS
Polysaccharide capsule
Intracellular pathogen
*Prevents fusion of the phagosome-lysosome and acidification–>Cell-mediated activation is crucial for resoltuion of infection
Where is Tularemia most commonly seen?
Primarily in the Northern Hemisphere (Oklahoma, Missouri, Arkansas)
- Acquired by inhalation of infected blood aerosol when skinning animals
- Ingestion of contaminated meat
What are the reservoirs for Tularemia?
Wild mammals
What is the vector for Tularemia?
Hard-shell ticks
What is the difference between summer & fall/winter Tularemia?
Summer= ticks Winter= small game
What are the three types of Tularemia, and what are they dependent on?
There are three major forms of Tularemia that are dependent on the site of inoculation:
1) Skin= Ulceroglandular
2) Eye= Oculoglandular
3) Lungs= Pneumonic
What are the symptoms of Ulceroglandular Tularemia?
This is caused by direct inoculation of Fraceisella tularemia into the skin
- Red painful swollen papule that becomes swollen and ulcerates
- Lymphadenopathy may occur with suppuration (filled with pus) & ultimately ulcerate
- Patient may become bacteremic
- Many patients will be febirle, experience headache, and photophobia
What are the symptoms of Oculoglandular Tularemia?
This is caused by direct inoculation of Fraceisella tularemia into the eye
- Painful conjunctivitis with swollen cervical lymph nodes
What are the symptoms of Pneumonic Tularemia?
This is caused by inhalation of Fraceisella tularemia
- Causes pneumonitis & eventually sepsis
- High rate of mortality and morbidity
How is Tularemia diagnosed?
- Hx
- Serology and molecular techniques
- Culture is slow and difficult
*Must inform lab of suspected case
How is Tularemia treated?
Gentamicin
How is Tularemia prevented?
- Prevent tick bites
- Hunter education i.e. precautions when skinning animals
What is the causative organism of the Plague?
Yersinia pestis
List the characteristics of Yersinia pestis.
- Gram negative rod
- Non-motile
- Produces a PROTEIN capsule
What is the difference between the appearance of Yersinia Pestis on Giemsa stain & Gram stain?
Gram= red (negative)
Geimsa= purple with “closed safety pin” morphology
What are the virulence factors associated with Yersinia pestis?
- Protein capsule
- LPS
3x plasmids associated with virulence
- Biofilm formation
- Enhanced resistance to macrophage killing
- Complement resistance
What animals serve as reservoirs for Yersinia pestis?
- Mostly rodents
- Rat fleas
What is the most important animal reservoir of Yersinia pestis in the US?
Prarie dogs
How is Yersinia pestis transmitted?
- Bite from infected fleas
- Bites & scratches from cats that killed infected rodents
- Inhalation of aerosol
Human–>human is possible
What are the symptoms of Bubonic plague.
Bubonic plague is caused by a flea bite
- Fever, chills, headache, myalgia
- Painful lymphadenopathy develops proximal to the port of entry– called “buboes”
- Surrounding area becomes swollen and inflammed
- Overlying skin may be stretched & desquamate
- Buboes may perforate if untreated–>bacteremia & septic shock
- Gangrene of the extremities
50% mortality
What is pneumonic plague?
Inhalation of respiratory droplets from an infected person or animal (Yersinia pestis)
What are the symptoms of Pneumonic plague?
- Fever, headache, myalgias & respiratory signs
- Progresses rapidly to symptoms of hemoptysis, resp. distress, cardiopulmonary insufficiency, cyanosis, and circulatory collapse
100% mortality
How is plague diagnosed?
History
How is plague treated?
Streptomycin
