Lc 18 Flashcards
What distinguishes mycobacteria from mycoplasma?
Presence of waxy cell wall
Where are those mycobacterium found?
Water, soil, foodstuffs.
Many are opportunistic pathogens in humans
What are some important determinants of disease presence and severity for all of disease from mycobacteria?
Host susceptibility
Are mycobacterium gram negative or gram positive?
Neither, but slightly positive when stained
What are composed of in their cell wall?
60% mycolc acids. ( waxy coats), lipoarabinomannan
Mycobacteria are acid fastness. What does it mean?
Resists destaining( resistance to decolorization) by acid or ethanol
What does the waxy cell wall do?
It is very resistant to drying
Even if you stain the bug(mycobacteria), you won’t see any color but purple. True or false?
True.
How do you divide mycobacteria into two distinct types?
Slow growing and fast growing
Explain slow growing and fast growing.
Slow growing :
-M.tuberculosis, M.leprae are examples
- Generation times often 40x E.coli
- forms visible colonies > 7 days
Fast frowing:
- M. abscessus spp
- Forms visible colonies or growth < 7 ays
Explain mycobacteria’s characteristics
Aerobic
Nonmotile (except M.marinum)
Difficult to culture in vitro
Difficult to manipulate genetically
Susceptibility to infection is conferred by host characteristics
Mycobacyeria are hard to grow in in vitro and hard to manipulate genetically.
What does that result in?
Hard for lab study and diagnosis
What characteristics of slow mycobacteria growth makes them difficult to treat?
-less likely to respond to standard antibiotics
-often grows to high densities before immunity develops
- develop resistance to single agents easily
How do we treat mycobacterium?
Use multiple drugs
What are the cause of resurgence of mycobacterium?
Poverty
Crowding
Malnutrition
Africa-Asia hardest-hit
Multi drugs resistance
HIV/AIDS
HIV impacts TB. How do they do that?
They infect T cells
AIDS increases susceptibility to to tuberculosis. True or false
False. AIDS increases susceptibility to to non tuberculosis disease, especially M. Avium complex
Covid also impacts TB. Does poverty impact TB?
Yes. Sadly
What are the clinical features of TB?
Primary : often quite
Immunocompromised - bugs go crazy and disseminated disease can occur
Secondary: reactivation disease .
Immune response(night sweats, fever, weight loss)
How do TB get transmitted?
Via droplets
—> coughing, talking,sneezing
—> remain in the air for hrs
—> small droplet nuclei can penetrate lung airspaces
—> require prolonged recurrent exposure for infection
Explain TB pathogenesis
-M. Tb replicate in macrophages, destroying them.
-Blood borne inflammatory cells migrate to infection —> granuloma
-infected macrophages disseminates via lymphatic to lymph nodes
Define immunocompetent and immunocompromised
Immunocompetent : helathy individ. W good immune systems
Immunocompromised: unhealthy, susceptible individuals, —> often in infants and elderly
When does TB get very infectious? Primary or secondary TB?
Secondary TB (deactivation)
When does latency state happen?
Once they have developed immune response..
It splits into two categories :containment, reactivation
How do we diagnose TB.
Microscopy, culture, PCR, skin yest(PPD), IFN-r release test
What is the most important part of treating TB.
Use multiple drugs
Use more than 3 agents for disease
(High bacterial burden)
Single agent for known exposure, no disease (low bacterial burden)
What is the first bacterium identified as causing disease in humans
Leprosy (Hansen’s disease)
Can we cultivate leprosy in vitro?
No
What are the hosts of leprosy?
Humans and primates
Armadillos
Eurasian red squirrel
How does leprosy get transmitted?
Aerosol
Exposure to animals or soils
Epidemiology is very difficult
We also need multidrug therapy for leprosy. True?
True.
Use multi drugs —> lose infection within 3 days
