Micro- Zoonotic Infections Flashcards
What are the 3 major zoonotic pathogens that cause serious disease?
What age group do they tend to affect?
- Yersinia pestis [plague]
- Franisella tularensis [tularemia]
- Brucella [brucelliosis]
These diseases tend to occur in adults
To what area of the country is yersinia pestis restricted [in the absence of a bioterror attack]?
What is the reservoir?
West and Southwest
It is sylvatic/enzootic plague found in small rodents and the larger animals that eat the small rodents
What is the most common source of brucelliosis in Texas?
Unpasteurized goat milk products from Mexico
How does yersinia pestis gram stain?
G+ or G-? Cocci or bacilli?
What is unique about the staining on Wright or Wayson?
What is the oxygen requirements?
It is a G- bacillis that has bipolar staining on wright or wayson.
It is a facultative anaerobe
What temperature and what type of media can yersinia pestis grow on?
How long does it take to grow visible colonies?
Yersinia grows at 28 degrees celcius on blood or MacConkey’s agar.
It takes 2 days to grow visible colonies
What disease is caused by:
- yersinia pestis
- Y. enterocolitica
- Y. pseudotuberculosis
What is the reservoir for these organisms?
- bubonic, septicemic, and pneumonic plaque
- gastroenteritis
- gastroenteritis
Reservoir: variety of animals and birds [y. pseudoTB]
How does an usually contract plaque?
- direct or indirect exposure to a plague-infected animal
- handling infected animals
- bitten by an infected rodent flea - bioterror
In what areas of the world is plague most prevalent today?
Sub-saharan Africa and Madagascar
Describe the pathogenesis of yersinia pestis from introduction to the host until first symptom of the plague.
yersinia pestis grows in gut of infected fleas where it expresses anti-phagocytic fractionI antigen.
- flea bites and regurgitates yersinia pestis into the bite site
- it travels by cutaneous lymphatics to lymph nodes
- y. pestis is phagocytosed by PMNs and monocytes
- PMNs kill the bacteria, mononuclear phagocytes do not
- Proliferation in the lymph nodes lead to swelling [BUBO] that occurs after 2-6 days
What antigen is up-regulated while Y. pestis grows in the lymph node that helps it evade host immune response?
Y. pestis synthesizes an increased level of anti-phagocytic fraction I antigen which helps it resist further phagocytosis
What is the pathogenesis of y. pestis once it is released from regional lymph nodes?
- released from regional lymph nodes via cell lysis
2. hematogenous dissemination causing septicemia
What 4 symptoms are associated with “secondary septicemic plaque”?
When does it occur?
Secondary septicemic plague occurs after infection with Y. pestis–> bubo formation–> dissemination in the blood.
- shock
- DIC
- necrotic and hemorrhagic lesions in other organs
- purpura of distal extremities [fingers] become gangrenous (which is why it is called “black death”)
What is primary septicemic plague?
Severe febrile illness that occurs in the absence of obvious buboes or pneumonic plague
What are the 2 causes of pneumonic plague?
What is case fatality of pneumonic plague if untreated? Treated?
- bubonic and/or septicemic plague proceed to involve the lungs
- inhalation of aerosolized Y. pestis [bioterror scenario]
Untreated : 100%
Treated: 57%
How is diagnosis of plague made?
- febrile patient that was exposed to animals or had insect bites in a plague endemic area should be suspected
- if bubonic–>bubo should be aspirated and:
- gram and wayson stained
- cultured on blood and macconkeys
If septicemic or pneumonic:
-culture and stain blood and sputum respectively
What must you do if you suspect a case of plague?
Contact the local and state public health departments
What is treatment for plague?
What is used as mass prophylaxis in bioterrorism setting?
Treatment: streptomycin, gentamicin
Mass prophylaxis: doxycycline, ciprofloxacin
Describe the microbiology of francisella tularensis.
G+/-? cocci or bacillus?
What is unique about the staining?
What is the oxygen use?
It is a G- bacillus that may or may not show bipolar staining [like y. pestis]
It is facultative anaerobe
What disease is caused by francisella tularensis?
Tularemia aka Rabbit fever aka Deerfly fever
F. tularensis is very hardy and can survive in ___ or __________ for weeks.
water or soil
What special growth requirement does f. tularensis have? How long does it take to grow? at what temp?
It requires sulfhydryl compounds [cysteine or cystine] for growth (so it will not grown on normal lab media)
It grows in 2-4 days at 35 degrees C
What are the 2 biogroups of F. tularensis?
Which is more virulent?
Where is the more virulent group found almost exclusively?
A and B
A is more virulent than B and is found exclusively in N. America
What are the six clinical syndromes caused by F. tularensis?What are they dependent to some degree on?
Dependent to some degree on the portal of entry of the organism into the human body
- ulceroglandular - skin ulcer with painful regional lymphadenopathy
- glandular - lymphadenopathy alone
- typhoidal - no lymphadenopathy
- pneumonic
- oculoglandular - conjunctivitis and cervical or preauricular lymphadenopathy
- oropharyngeal - pharyngotonsillitis with cervical lymphadenopathy
What is the regional preference for tularemia in the US?
What is the seasonal preference?
All states have it, but the majority of cases occur in South-Central and Western states.
April–> September
What is the reservoir of tularemia?
What is the vector?
What are the 2 ways humans can be infected? Which is more common way children are infected?
Reservoir: rabbits, hares, rodents
Vector: deerfly or tick infected by feeding on an infected animal
Man acquire infection by:
- getting bit by an infected tick or deerfly [tick is most common for childhood tularemia]
- handling or eating infected animal
________ bacilli will cause disease if inhaled or injected intradermally, but it requires ________ organisms for oral route infection.
10-50 bacilli if inhaled or injected
10 to the 8th if oral-ingestion
Describe the pathogenesis of ulceroglandular tularemia.
When does the onset of overt disease [fever, chills, malaise, fatigue and lymphadenopathy] occur?
- bacteria multiply to form a papule at the site of entry [tick bite] that appears in 3-5 days
- papule ulcerates 2-4 days later
- bacteria move from portal of entry to regional lymph nodes where they grow in phagocytic cells [facultative intracellular parasite]
Overt disease coincides with the appearance of the papule and is abrupt
What are the 2 ways to acquire pneumonic form of tularemia?
- inhalation of the organism
2. hematogenous spread
If you are suspicious of tularemia, what are the steps you need to take for diagnosis?
What additional step must be taken if it is inhalation tularemia?
- notify the clinical laboratory because of the EXTREMELY infectious nature of F. tularensis
- get sputum, exudate, biopsy and send to reference labs for direct fluorescent Ab test
- isolate organism on cysteine heart blood agar
If it is inhalation tularemia, contact local and state public health departments
What is prevention for tularemia?
What is treatment for controlled situations?
Treatment for mass casualty situations?
Prevention - vaccine is in the works by FDA
Treatment for controlled:
IM streptomycin, IM/IV gentamycin
Treatment for mass situations:
Oral doxy and oral ciprofloxacin
What is the microbiology of Brucella?
G+ or G-? Bacillus or cocci?
What is the oxygen requirements?
It is a G- bacillus
Facultative anaerobe
What 4 species of brucella cause disease in humans?
What is the reservoir for each?
- B. abortus = cattle, elk, bison
- B. melitensis = goats and sheep
- B. suis = pigs
- B. canis = dogs in commercial kennels
What body systems are effected by brucellosis?
How long after the organism enters the body until the start of disease?
Brucellosis is a systemic infection, but any organs system of the body can be involved: cardio, respiratory, GI, GU, skin, hepatobiliary, skeletal, nervous
2-4 weeks from brucella introduction to onset of disease
What are the short term and long term symptoms of brucellosis?
Short term = flu-like fever, sweats, headache, back pain
Long term:
- recurrent fevers
- joint pain
- fatigue
- depression
What accounts for the majority of brucellosis-related deaths?
Endocarditis
Where does brucella localize in the animals?
How does this contribute to symptoms?
How is it spread animal to animal?
It localizes in reproductive organs leading to:
- reduced milk production
- weight loss/infertility
- spontaneous abortions
Spread by licking aborted fetuses or newborns from infected mothers
What is the most common laboratory-associated infection caused by a bacterial pathogen?
brucella
Which 3 strains of brucella are on the bioterrorism list of “select agents” due to their ability to cause infection via aerosol?
B. suis, B. melitensis, B. abortus
What are the 3 main ways by which brucella gains access to the human body? Which is most common?
- ingestion [most common via unpasteurized goat milk]
- inhalation [slaughterhouses]
- entry via skin wounds [hunter processing feral pig]
What is the pathogenesis of brucella once in the human?>
- engulfed by PMNs but are facultative intracellular parasites
- localize to organs of the RES [lymph, spleen, marrow, liver]
How is brucellosis diagnosed?
- detailed history including diet, animal exposure, travel and occupation [because symptoms are VERY non-specific]
- culture blood, marrow, tissue HOWEVER it takes 4 weeks to grow
- serologic testing
There are no human vaccines for brucella, however, which 2 strains of brucella have live attenuated vaccines for the animals?
B. abortus
B. melitensis
What is treatment for brucellosis?
How long is treatment?
- doxy + streptomycin
OR - doxy+ rifampin
Treatment must be atleast 6 weeks to kill intracellular brucella
