Respiratory Bacterial Zoonoses Flashcards
What are the three bacterial agents of respiratory bacterial zoonoses? What do they all have?
- Yersinia Pestis (PLAGUE)
- Brucella spp (BRUCELLOSIS or undulant fever)
- Coxiella burnetti ( Q-FEVER)
All three of these bacteria have ANIMAL RESERVOIRS.
What is unique about the transmission of plague (Y pestis) compared to the other two?
Plague is the only one transmitted via a VECTOR, the FLEA, and in the PNEUMONIC form, it can be transmitted HUMAN-TO-HUMAN. (neither brucellosis nor Q fever can be transmitted human-to-human.
How is Brucellosis acquired?
by direct contact with animals or by the consumption of unpasteurized dairy products
How is Q fever acquired?
by inhalation of animal aerosols
Are these three infections common or rare? Which one of the three is regionally restricted?
These zoonoses are rare.
Y. pestis (plague) is regionally restricted.
What organism causes Plague?
Yersina Pestis (Yp)
What is the most common natural form of plague?
Beubonic Plague
How is Plague transmitted? Where?
Transmission is via the FLEA from GROUND RODENTS (and rabbits) in NEW MEXICO AND ADJOINING STATES and some rocky mtn states to the north.
What are the keys to Dx of Plague? (3)
- History: exposure to ground rodents, fleas, rural Southwest US
- LARGE SWOLLEN PAINFUL NODES, usually one-sided axillary or inguinal, fever.
- Failure to respond to BETA-LACTAMS and MACROLIDES
What is secondary plague pneumonia?
It follows beubonic plague and is rare. It causes severe respiratory and systemic symptoms. Plague pneumonia is nearly always FATAL and it’s CONTAGIOUS.
What form of plague is expected in a bioterrorist attack? How is it spread?
Primary Plague Pneumonia; from a PERSON or CAT with plague pneumonia
How are Yp described microscopically? When might they be seen?
As Chubby gram-negative rods with bipolar inclusion bodies said to look like SAFETY PINS.
They are sometimes seen in biopsies, blood smears, and CSF.
What type of bacteria is Yp? What can they grow on?
Yp is an ENTEROBACTERIACAE that is capable of growing on BAP and enteric media.
What are two important virulence factors of Yp?
- Type three secretion system
2. F1 Protein antigen capsule
What does the type three secretion system of Yp do?
It injects effectors into host cells.
It paralyzes phagocytes, and also suppresses the innate and, to some degree, adaptive immune response.
What virulence factor is unique to Yp among the Yersinia? What is it the basis for?
F1 protein antigen capsule; it is the basis of rapid tests and confirmatory serological tests
What are the 3 forms of plague?
- Bubonic (60% fatal if untreated)
- Septicemic
- Pneumonic (100% fatal if untreated)
In bubonic plague, what is the initial infection from? What is the incubation period?
it is from a flea bite (1-8 days incubation)
What are the signs/symptoms of bubonic plague?
SWOLLEN PAINFUL axillary or inguinal, femoral LYMPH NODES called BUBOES, with fever, chills, headache, possible vomiting, nausea, prostration.
Ulcerous or macular lesion may or may not be seen at the site of the flea bite.
How do the site lesions of bubonic plague compare to those of tularemia or anthrax?
BP site lesions are not as prominent
25% of bubonic plague cases progress to what?
severe septicemia
What are the signs/symptoms/characteristics of Septicemic Plague?
- W/ or w/out buboes
- rapid progression
- SEVERE TOXEMIA and GENERAL ORGAN SYSTEM FAILURE
- Vomiting/diarrhea
- PETECHIAE to EXTREME DIC
What does secondary pneumonic plague result from?
(it will include septicemia)
It results from dissemination from primary infection from flea bite (10%
What is the prognosis of secondary pneumonic plague?
Extremely poor prognosis with rapid progression from first symptoms to death
What is unique about secondary pneumonic plague?
It is CONTAGIOUS, so it requires isolation of the patient and prophylaxis for all exposed individuals
What is the sputum like from a patient with secondary pneumonic plague?
Productive sputum more bloody and watery than purulent; necrotic
What is the differential Dx for a patient presenting with a bubo?
- Tularemia (inoculation site should be more evident and pt shouldn’t be septicemic early on)
- Chancroid: inoculation site should be more evident, no sepsis, less local pain, and a recent Hx of sexual contact and genital lesions
- Lymphogranuloma venereum: a recent history of sexual contact and genital lesions
- Strep/staph adenitis: pt should be less septic and the lymph node likely to be more fluctuant and less painful; often purulent, often an ascending or descending lymphangitis or cellulitis
- Cat-scratch disease: Hx of cat scratch; indolent course; no systemic toxicity
What is the DDx for septicemic plague?
- Meningococcemia
- Other gram negative sepses
- Rickettsioses
In a pt with pneumonic plague, what suggests Yp as the causative agent, given all the possible causes of systemic toxicity with a productive cough with bloody sputum?
Identification of gram negative rods in sputum of an otherwise immunocompetent pt
Where is natural plague contracted?
only where silvatic (rural, natural zoonotic) plague exists, which is entirely west of the mississippi in the west (New Mexico area)
What is the animal reservoir of plague?
ground rodents (occasionally rabbits and cats infected from fleas of rodents)
How is bubonic plague transmitted?
flea bite
How is primary pneumonic plague transmitted?
a) from a case of human pneumonic plague
b) from a cat with pneumonic plague
c) an act of bioterrorism
How is plague diagnosed?
- Serology: based on Abs to F1 surface antigen (CONFIRMATORY)
- Gram stains of buboes, sputum blood, which may reveal safety pin rods
- Culture
- IF test
- New RADT (dipstick test)
What medications are used to treat plague?
- GENTAMICIN (STREPTOMYCIN, if available)
- Doxy
- Cipro
When is immediate treatment of plague imperative?
if it is septicemic or pneumonic
What is given prophylactically to people exposed to pneumonic plague?
doxy for 7 days; no vaccine exists
If Brucellosis rarely involves the lungs, why is it important in the context of respiratory illnesses?
B/c its symptoms are often confused with TB
What are the characteristics of Brucella?
It is a small gram negative aerobic coccobacillus. It is a facultative intracellular parasite of the RES (liver, spleen, bone marrow), and it can be cultured on a rich medium.
What is the time course of Brucellosis?
aka Undulant fever, it is usually a slow-moving, chronic infection, but initial infection can be acute (flu symptoms with high fever)
What are symptoms of chronic brucellosis?
- RELAPSING FEVER (nocturnal with NIGHT SWEATS; may go on for several weeks if untreated)
- Weakness, generalized symptoms, weight loss, fatigue
- Can be localized, infect bones (esp lower vertebrae), liver, heart, GI and UG tracts (orchitis)
- Long-term sequelae sometimes occur, including hepatitis. endocarditis
- THE TYPICAL LESION ON BIOPSY (BONE, LIVER) IS A GRANULOMA
DDx for Brucellosis?
- TB
- histoplasmosis
- cryptococcosis
- Leptospirosis
- typhoid fever
- infectious mononucleosis
- various forms of hepatitis
- non-infectious spondylodiscitis
- Flu
What are the animal reservoirs of brucella?
In the US, typical reservoirs are cow, sheep/goats, and pigs, with UG tract and mammary glands infected.
Wild animal reservoirs include American bison, elk, wild boars, other herbivores
How is brucella transmitted?
- BY CONTACT (thru abrasions) with infectious materials
- CONSUMPTION OF RAW MILK, UNPASTEURIZED CHEESE
- Rarely, inhalation of aerosols from infected animals (dry cough, pleuritic chest pain; CXR may be negative
There is no human-human transmission of brucella, and no arthropod vectors
What types of people are at risk for brucellosis?
- People handling animals or animal viscera (vets, farmers, slaughterhouse workers)
- Consumers of raw milk, unpasteurized cheese: almost exclusively RECENT IMMIGRANTS from MEDITERRANEAN area, MEXICO, or those recently living in these areas and consuming raw cheese
How is the Dx of brucella made?
- SEROLOGY (b/c of chronic nature, high initial titer is often diagnostic)
- Can be cultured on rich media
How is brucellosis treated?
Treatment requires prolonged course of suitable antibiotics (usually doxycycline plus and aminoglycoside)
How is brucellosis prevented/controlled in the US?
- Pasteurization of milk, including milk used to make cheese
- Live attenuated vaccine for cattle
- Destroying infected herds
What bacteria causes Q fever? What is it?
Coxiella burnetti (Cb); it is an obligate intracellular parasite that infects animals, which are the primary source of human infection.
What are the characteristics of Cb?
It’s a gram negative bacillus that is an obligate intracellular parasite, closely related to Legionella.
Where does Cb replicate?
in phagolysosomes
What are the symptoms of Q fever?
1/3 to a 1/2 are asymptomatic.
Symptoms:
1. acute febrile illness, atypical pneumonia that lasts 2-4 weeks
2. Sometimes liver and heart involvement
3. Long term chronic infections are rare but may lead to ENDOCARDITIS, or granulomatis hepatitis
What is the DDx for Q fever?
- Atypical pneumonias
- Tularemia
- Ehrlichioses and RMSF
- Mycobacterial infections
What are the animal reservoirs of Q fever?
mainly cows, sheep, and goats
How is Q fever transmitted to humans?
- by aerosol
- by handling viscera including amniotic fluid, placentas
- drinking raw milk
- occasionally by ticks
What is unique about the distribution of Cb?
It has a spore-like form that permits distribution over several miles by wind, giving it the potential to cause serious disease.
How is Q fever diagnosed?
Serology: looking for high or rising antibody titers to Q fever antigen
How is Q fever treated?
Most infections will resolve spontaneously, but doxycycline treatment can shorten duration and reduce risk for chronic infection
