E2- MTB and NTM Flashcards
Are mycobacterium tuberculosis infections common?
Yes, many millions/billions infected but over 90% of healthy persons infected never become ill
What strains of mycobacterium tuberculosis are particularly difficult to tx?
MDR (multi-drug resistant) and XDR (extensively drug resistant) strains
What are the two main problems for pts with inadequate tx for a mycobacterium tuberculosis ?
Remain infectious
Opportunity for drug resistance
Who are the only reservoirs for MTB?
Humans
How is MTB transmitted?
Person-to-person via aerosol droplet nuclei
not as dangerous on surfaces
What populations have an especially difficult time with MTB and MAC?
AIDs`patients
What is an occupational hazard for people who do autopsy and anatomist from accidental exposure to MTB? How can you prevent these?
Prosector’s warts
Gloves
What age populations are most commonly affected by MTB?
Bimodal age distributions- infants and older adults
Who is at highest risk for MTB infection?
Infants and immunocompromised pts
What can result in meningitis?
Hematogenous dissemination of a MTB infection
What is a possible etiology of MTB in older pts?
Failure of the immune system
Possible reactivation of latent infection
What three things influence the probability of MTB infection?
Environment- crowded conditions
Duration of exposure
Virulence of strains
How do many children become infected by MTB?
Close contact with caregivers
What are some initial MTB infection risk factors?
Close contact with TB case Residence in long-term care facility Low income/inner city housing Alcohol or IV drug use Malnutrition DM Silicosis- pneumoconiosis (coal minners) Imunosupression
What three species of MTB produce human TB?
Mycobacterium tuberculosis Mycobacterium bovis (cattle) Mycobacterium africanum (Wast Africian)
How do we control Mycobacterium bovis?
Pasteurization and treatment of infected farm animals
How is Mycobacterium africanum spread?
Opportunist infection, especially in immunocompromised HIV pts
Spread by food, no animal reservoirs
What aerotolerance is M. tuberculosis? What shape?
Obligate aerobes
Bacillus
What vaccine can be used for MTB in high endemic regions?
BCG (Bacille Calmette-Guerin)
What can kill M. tuberculosis?
Heat sensitive- killed by pasturization
Where does M. tuberculosis grow within a human?
Alveolar macrophages
What two qualities does mycolic acid give M. tuberculosis?
Acid fast
Hydrophobic
What virulence factors and toxins do MTB have?
No classic virulence factors or toxins, the structural features create the issues
What structural components makes MTB virulent?
Mycolic acids
Cord factor
Lipoarabinomannan (LAM)
How does mycolic acid add virulence to MTB?
Prevent dehydration and resists H2O2
What is a cord factor?
Mycoside- glycolipid mycolic acid + disaccharide
How does Lipoarabinomannan (LAM) provide virulence to MTB?
Inhibits cell-mediated immunity
Scavenges ROI
What are the five potential outcomes of MTB infection?
- Immediate resolution
- Primary disease
- Progressive primary (active) disease
- Latent infection
- Endogenous reaction/secondary infection
If there is no active TB because the innate immune system is able to clear the bacteria, what is this called?
Immediate resolution
Granuloma formation may progress to what?
Caseous lesions
What are areas surrounded by macrophages, multi-nucleated giant cells, fibroblasts, and collagen fibers that harbor viable MTB cells?
Ganulomas
Over time, what can form fibrotic tubercle and calcify, and can be seen on X-ray?
Granulomas
What is MTB diagnosed?
X-ray
Skin test
Sputum strain culture
Rapid blood test based on IFN-y
The USA depends on what for treatment of infection persons?
Recognition, isolation, and treatment of infected persons
What kind of testing is used to ID latent TB?
Serial screening
Is MAC gram positive/negative/acid fast? What shape?
Weakly gram positive bacilli
Acid fast
Where is MAC found?
Water, soil, and plants
How is MAC transmitted?
Ingestion of contaminated water or food
DISTINCT FROM TB- NO person to person transmission
Is patient isolation required for MAC infection?
NO
no person to person transmission
What is the leading cause of Nontuberculous mycobacteria (NTM) infection in HIV-positive pts in the US?
MAC
What patient populations may get a disseminated MAC infection
AIDS patients
How is Nontuberculous mycobacteria (NTM) dx?
Microscopy to reveal acid-fast bacteria and culture
Must exclude other etiologies (fungi, TB)
-Use PCR to determine 16s rRNA sequence pathogen
What must you take into account when treating a MAC infection?
HIV infection status
What is an epidemic infection among cystic fibrosis patients?
Mycobacterium abscesses (very difficult to treat in CF due to intrinsic abx resistance)
Can latent TB be spread? Should these pts be treated?
Latent TB cannot be spread, but these pts should still be treated
What results from lymphohematogenous spread of a primary infection or by a latent focus with subsequent spread?
Miliary tuberculosis
What test can be used to detect MTB and Rifampin resistance?
GeneXpert Rapid Test
What syndrome is found in elderly female non-smokers and is associated with MAC?
Lady Windermere’s syndrome
What kind of stains are used for MTB?
Ziehl-Neelson or Kinyoun stains
How would you treat a MAC infection in HIV negative patients?
Continue antibiotics until sputum cultures are negative for 1 year
How do you prophylactically treat HIV positive patients without a MAC infection?
Chemoprophylaxis in patients with CD4< 50, and can discontinue after 3 months after CD4 >100
How do you treat HIV positive patients with a MAC infection?
Lifelong therapy for patients without immune reconstitution
-or begin treatment for 2 weeks then anti-HIV HAART
What can be used to treat HSV?
Acyclovir, valacyclovir, and Famciclovir
What is the MOA of acyclovir/valacyclovir?
The viral enzyme thymidine kinase phosphorylates acyclovir and this will halt viral DNA replication
What is the treatment for parvovirus?
- Most patients make a rapid and full recovery.
- NSAIDS
- Immunoglobulin for anemic patients
