Flashcards in Lecture 6: Myobacteriae Deck (75)
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1
What is the family and genus of Myobacteriae?
Family: Mycobacteriaceae
Genus: Myobacterium
-more than 100 species
2
Define what Myobacteriae are?
Slow-growing, rod-shaped, non-spore forming, nonmotile
3
What is the main way to identify Myobacteriae?
Acid-fast staining (Ziehl-Neelsen stain)
-Myobacteriae have cell walls with high lipid contents (25%) that are able to absorb the dye
-once stained they cannot be decolorized with acid solutions
*you'll see a bunch of pink spots if it is a Zihel-Neelsen stain*
4
Define M. Tuberculosis
-disease of humans transmitted by respiratory droplets
-human host with person-to-person transmission
-presents like cancer because of non-specific symptoms and hemoptysis
5
Which animals can be incidentally infected by M. Tuberculosis?
-apes
-elephants
-dogs
-cattle
-pigs
6
What is the transmission of TB from humans to animals called?
Reverse zoonosis
7
When was reverse zoonosis of TB discovered?
-exotic animal farm in Illinois in 1996 where elephant handlers may have transmitted disease to elephants
-otherwise not typically found in the wild
8
What are specific clinical symptoms associated with MTB?
-coughing that lasts three or more weeks
-coughing up blood
-chest pain, pain with breathing or coughing
-unintentional weight loss
9
What are non-specific clinical symptoms of MTB?
-fatigue
-fever
-night sweats
-chills
-loss of appetite
10
What is NTM?
Non-tuberculosis Myobacterium
11
What is the pathogenesis of NTM?
-present in environment but rarely cause disease in comparison to MTB and M. leprae which are obligate pathogens (need to cause disease in order to be transmitted)
-host susceptibility determines infection
-share common properties with MTB: acid fastness, ability to cause pulmonary and extrapulmonary granulomatous disorders
12
What host susceptibility factors determine infection of NTM?
-deficiencies of IFN-gamma receptor or IL-12 receptor
-acquired deficiency of cell-mediated immunity (HIV)
-diabetes
-preexisting lung disease
-body habitus in postmenopausal women (pectus excavatum, scoliosis, mitral valve prolapse)
13
What is the prevalence of NTM?
largely unknown because it's not actually a reportable disease since its not transmissible from person-to-person
-rates increasing from 90s but this may be because of improved detection methods
14
What are recent trends that have sparked interest in NTM?
-increasing NTM infections in AIDS patients
-increasing NTM lung disease in HIV negative population (caucasian women over age of 50 who have had children are at higher risk of disease but they don't know why)
15
Have rates of TB been decreasing in relation to NTM last 10 years?
NO, we have just gotten better at detecting NTM and distinguishing it from TB
16
What are the 4 clinical syndromes that NTM causes in humans?
1. pulmonary disease (most common)
2. superficial lymphadenitis
3. Disseminated disease (MAC-myobacterium avium complex in HIV)
4. skin and soft tissue infection due to direct inoculation
17
What are the 4 main methods to diagnose NTM?
1. acid-fast microscopy with fluorochrome stains
-but it has unreliable sensitivity
-environmental contamination rarely positive on smear
2. Gastric lavage fluid/Bronchoscopy if poor sputum production
3. Nucleic Acid Amplification Tests (NAA): provides fast differentiation of TB from NTM
-MTB-PCR identifies species
4. Sputum culture = GOLD STANDARD but it takes forever
18
What are the 4 clinical syndromes that NTM causes in humans?
1. pulmonary disease (most common)
2. superficial lymphadenitis
3. Disseminated disease (MAC-myobacterium avium complex in HIV)
4. skin and soft tissue infection due to direct inoculation
19
What are the 4 main methods to diagnose NTM?
1. acid-fast microscopy with fluorochrome stains
-but it has unreliable sensitivity
-environmental contamination rarely positive on smear
20
What is M. Bovis?
-causes less than 1.4% of pulmonary TB
-spread to humans from inhalation of infectious droplet nuclei and ingestion of raw milk
-animal host: cattle
-strictly pathogenic in humans but very rare in US
-human-to-human transmission is rare
21
How is M. Bovis controlled in transmission from cattle to humans?
Pasteurization
22
What are the two main ways M. Bovis is transmitted to humans?
1. direct contact with infected bodily secretions (i.e. inhalation of infected droplets)
2. consumption of infected animal products (i.e. milk)
23
What is the largest impact that M. Bovis has?
constraint in international trade of animals and their products --> results in major economic losses
24
What is the main route of cattle-to-cattle transmission of M. Bovis?
respiratory excretion and inhalation (cattle show respiratory disease at slaughter)
25
What does consumption of M. Bovis infected milk cause?
extrapulmonary TB-like symptoms = Bovine TB
26
Does M. Bovis only exist in cattle?
NO; cattle are natural and main host but also exists among bears, cheetahs, possums, deer, pigs, leopards, lions etc.
27
What is treatment for M. Bovis?
RIPE without the P: Rifampin, Isoniazid, Ethambutol
-2 months isoniazid, rifampin and ethambutol
-followed by 7 months of isoniazid and rifampin
** all three because it is resistant to pyrazinamide**
28
Do you have a special risk of acquiring M. Bovis if you are immunocompromised?
NO
29
In Kruger National Park which animals were spreading TB and how?
-high prevalence of tb in buffalo populations
-contaminate the environment through saliva and nasal secretions
-warthogs were drinking from same watering holes and grazing same areas
30
