Mycobacteria

Question 1

Mycobacteria Staining

Answer 1

Acid Fast Bacteria (stain pink while non-acid fast stain blue)

Fluorochrome stain is more sensitive than acid fast, but slightly more specific

Cannot Gram stain

Question 2

Mycobacteria General

Answer 2

Slender rods
Obligate aerobe
Cell wall high in lipids and N-glucolylmuramic acid
Does not Gram stain (will see ghost or beaded)
Acid fast stain
Slow growing

Question 3

Mycobacterium tuberculosis

Transmission, Pathogenesis, symptoms

Answer 3

Transmission: person to person via respiratory droplets

Leading cause of infectious agents worldwide

Bacteria multiply in alveolar macrophages. Can remain latent due to immunity (delayed type hypersensitivity)

Granulomatous inflammation occurs at initial foci and lymph nodes forming tubercles

Host injury is due to immune response instead of specific bacteria!

Active disease occurs when immune system cannot keep Tb under control or a granuloma explodes and releases Mtb; dissemination of Mtb can occur anywhere

Question 4

Testing for Mycobacteria tuberculosis

Answer 4

Acid fast or flurochrome stain of sputum, urine, stool, body fluids, blood

Cording in acid fast stain is common

Cultivation by inoculating bacteria and identifying with acid fast stain, nucleic acid probes, or prob negative isolates. Cultures are slow

Molecular testing

Nucleic Acid Amplification Test (NAAT): used in conjunction with smears and cultures, but have greater sensitivity and greater specificity; used for detection of Mtb and resistance

Tuberculin Skin Testing-inject tuberculin intradermally and measure ring of induration 48-72 hours later

Interferon-gamma release assay (IGRAs)-measure immune reactivity to Mtb; take IFN-gamma levels of three samples after adding Mtb peptides to see if it is elevated

Question 5

Difference between Latent and Active Mtb

Answer 5

Latent: no symptoms, cannot spread, do not feel sick, needs treatment to prevent Mtb from becoming active

Active: has symptoms (usually bad cough, bloody cough, flu-like symptoms), can spread TB, abnormal chest Xray, and treatment for active disease

Question 6

Miliary TB

Answer 6

When Tb infected lymph node eats through a vessel wall, spilling Tb into the blood stream and lung

Will look like millet seeds in an Xray

Question 7

Mycobacteria Kansasii

Answer 7

Causes chronic pulmonary infection in upper lobes of lungs

Usually acquired from tap water

Dissemination is rare unless patient is immunocompromised

Responds to antimicrobial therapy

Question 8

Mycobacteria Marinum

Answer 8

Cutaneous infection associated with exposure to salt/fresh water following trauma

“Swimming pool” or “Fish Tank” Granuloma

Question 9

Mycobacteria Gordonae

Answer 9

No treatment needed

Found in soil and water

Colonizes respiratory tract

Question 10

Mycobacteria Xenopi

Answer 10

Grows best in hot water systems, causing chronic pulmonary disease in adults with underlying disease

Question 11

Mycobacterium Leprae

Answer 11

Long incubation

Can cause single or widespread skin lesions

Attracted to Schwann Cells–>Causes peripheral neuropathy and sensory loss

Question 12

Challenges to treating TB

Answer 12

1. Slow-growing or dormant intracellular infection; bacteria live in macrophages
   4-9 months of treatment is needed
2. High rate of mutations that cause drug resistance
3. Compliance
4. Strong cell wall made of lipids (mycolic acid)
5. Often seen in people coinfected with HIV

Question 13

Multi-drug therapy for TB

Answer 13

Decrease odds that patient is resistant to a drug or becomes resistant to a drug

There is no cross-resistance among four major anti-TBs