Lec 2 Mycobacterium

Question 1

Epidemiology of mycobacterium tuberculosis:

transmission and inf severity

Answer 1

-Transmission by aerosols
-2nd most lethal infection itw

Question 2

sensitivity and resistance and properties of Mycobac:

Answer 2

Aerobic, non motile, acid fast intracellular bacilli

Sensitive to- UV, alcohol,aldehydes
Resistant to- Alkaline acid pneumonia

Question 2

Mycobacterium tuberculosis complex:

Answer 2

1)MB TB
2)M.Africanum
3)M.bovis
4)M.Microtii: Smooth growth culture

Question 3

Mycobacterium structure:

Answer 3

in the envelope, it has Mycolic acid lipid,

which resists decolorization after being stained already, leavin it in pink color.

Question 4

Growth medium of MB: Lowenstein-Jensen medium LJ

Answer 4

1)Lowenstein and jensen medium-
-contains egg-glycerol to enhance MTB growth
-malachite green which supresses growth of other bacteria
-slow growing (4-8 weeks)
- white dry rough growth

Question 5

Liquid medium:

Answer 5

Detects O2 consumption and CO2 production in 8 days to 2 weeks. (liquid medium is faster than LJ medium)

Question 6

M. TB Pathogenisis

Answer 6

-Transmitted to lungs by aerosols inhalation
-10 bacilli needed to cause infection
-Primary tuberculosis: Skin, intestine and lymph nodes, mainly lungs

Question 7

Lung MB TB:

Answer 7

Primary TB: asymptomatic
-Macrophages 1 in alveoli engulf bacteria and granulomatos lesion (tubercle) is formed.
-macrophages and bacilli migrate to hilar lymph nodes— milliary TB

Macrophages 2 attack tubercle (by O2 consumption) surrounding the lesion in granuloma.

This can progress into lung infection or necrosis, and become calcified— latent.

Question 8

Mycobacterium TB Clinically:

Things that increase the likelyhood that patients have TB

Answer 8

-HIV
-History of prior TB treatment
-TB exposure
-homelessness, malnutrition

Question 9

Classic signs of active pulmonary TB:

Answer 9

Cough/ hemoptysis
weight loss
fever
night sweats
chest pain

Question 10

Diagnosis:

Answer 10

-Chest X ray- whiteness in upper lobe

Lab:
-sputum/ tissue acid fast stain—– can give false negative stain
-culture
-PCR- detect drug resistance
-PPD
-IGRT- Interferon gamma release test> detect T cells to MTB antigens

Question 11

important

PPD test (mantoux test):

purified protein derivative

Answer 11

-Given intradermally
-2-12 weeks post infection
-Delayed hypersensitivity reaction in skin (PPD test is positive in) = active infection, vaccine, environmental TB

IF you doubt the result: Do IGRT

-False negative is possible

Question 12

Management and treatment:

prevention also

Answer 12

Isolation: negative pressure room until uninfectious ( after 3 negative tests)

directly observed therapy

(1st line anti TB)
-RIF/INA for 6 months + Ethambutol and pyrazinamide for first 2 months ( 4 medications first 2 months)

Prevention: BCG life attenuated vaccine
-Bacillus Calmette guerin
-Life attenuated M.bovis

Question 13

Environmental Mycobacterium divided into 4:

Answer 13

1)Photocromogenes, develop pigment after exposure to light
2)Scotochromogenes, develop pigment in the dark
3)Non-chromogenes
4)Rapid growers: visible growth on LJ medium within a week of subculture.

Question 14

1)Photochromogen e.g

Answer 14

M.marinum

-swimming pool granuloma
-poor growth, skin lesions should be incubated at 33C

Question 15

2)Scotochromagen e.g

isolated from?

name of bacteria

Answer 15

isolated from sputum or urine:

M.Scrofulaceum causes scrofula or cervical lymph adenitis

Question 16

3)Nonchromogens

Answer 16

most prevalent group, M.Avium intracellular complex — MAI think of HIV

-M.ulcerans: causes buruli ulcer; produces tissue necrosis toxin 31-34c

-M.xenopi: thermophile that grows at 45C
Cause pulmonary lesions.