Mycobacterium

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characteristics of all Mycobacterium species

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acid fast bacilli

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main component of cell wall

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mycolic acid

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specimens

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lower respiratory

gastric secretions

urine

tissue, CSF, blood

skin

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lower respiratory specimen

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sputum, bronchoaveolar lavage, bronchial washing

first morning is the best

collect over several days

induced sputum

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when to use bronchoscopy

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-if pt cannot cough up enough sputum

-if an induced sputum cannot be obtained

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gastric secretions specimen

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use if cannot get a lower respiratory specimen (kids)

1st morning is the best

neutralize immediately bc acids brought up will kill bacteria

usually use sodium carbonate to neutralize

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urine specimen

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1st morning is the best

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skin specimen

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use only if certain species are suspected

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processing specimens, use caution

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BSL 3

negative air flow room

biological safety cabinet

gowns, gloves, respirator

skin test every 6 months

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acid fast for direct smears

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Kinyoun- cold method

Ziehl-Neelsen- hot method

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Fluorescent for direct smears

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auramine

auramine-rhodamine

increased sensitivity

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how to process gastric/sputum specimens

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1-NALC n-acetyl-L-cysteine to digest mucus

2-NaOH to decontaminate specimen

3-neutralize after 15 mins

4-centrifuge to concentrate specimen

alternate: trisodium phosphate + benzalkonium chloride

5- culture!

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how to process urine specimen

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concentrate

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Mycobacterium culture

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use solid & liquid media

Lowenstein-Jensen

Middlebrook

Petragnani

Can add antibiotics but need to run non-selective parallel

automated detection systems

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Lowenstein-Jensen agar

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for Mycobacterium

egg-based

Good for TB

malachite green: bactericidal, makes it selective

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Middlebrook media

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clear agar-based

not selective

2 types: 7H10 and 7H11 (the more selective one)

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Petragnani media

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for heavily contaminated specimens, highly selective

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incubation of media

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temp: skin 30 C, others: 37

increased CO2

up to 8 wks before calling it

TB grows in 3-5 wks in solid media

some intracellular bacteria take 6-8 wks to grow

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initial tests once growth on media:

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check acid-fastness

check colonial morphology

if unpigmented, expose to light for 1 hr and reincubate

record time it took to grow

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Mycobacterium complex consists of

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M. tuberculosis (most common)

M. bovis

M. africanum

M. canettii

M. caprae

M. microti

M. pinnipedii

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Mycobacterium tuberculosis

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causes tuberculosis (TB)

only contagious AFB

cording of AFB is common

see a lot in people with immunosuppression

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transmission:

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can lie latent for a very long time

droplets causes pulmonary TB

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AFB and transmission

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machrophages phagocytize AFB but cannot kill them

reproduce & infect new macrophages--> lasts several weeks--> no symptoms--> inflammation--> macrophages surround site of infection--> tubercle--> collagen deposited--> necrosis of tissue/ center liquefies and fills with air

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secondary/ reactive TB

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when tubercle ruptures

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TB symptoms

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chronic cough

low-grade fever

weight loss

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Latent TB Infection (LTBI)

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inactive, contained tubercle bacilli in the body

TST/blood test: usually +

chest x-ray: normal

sputum smear/culture: -

symptoms: no

infectious: no

Case of TB: no

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TB Disease (in the lungs)

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active, multiplying tubercle bacilli in the body

TST/blood test: usually +

chest x-ray: abnormal

sputum smear/culture: may be +

symptoms: cough, fever, weight loss

infectious: yes, often before treatment

case of TB: yes

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Sites of TB disease (Miliary TB)

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bacilli commonly found in: brain, larynx, lymph node, bone, pleura, lung, kidney, spine

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methods to screen of TB

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skin tests: mantous or tine

chest x-ray

IGRA: interferon gamma release assays, blood test

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IGRA Principle

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measure pt's immune rxn to M. tuberculosis

detects release of interferon-gamma (IFN-y) from WBC in heprainized whole bld when incubated with 2 TB proteins

ELISA test

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2 proteins used in IGRA

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ESAT-6: early secretory antigenic target

CFP-10: culture filtrated protein

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uses for IGRAs

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detect LTBI and active infetion

for pts that won't return for TST reading

for pts who received BCG

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CDC testing recommendations

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Test pulmonary specimens for M. tb

AFB smear

culture for 1-8 weeks; 1 liquid and 1 solid media

at least 1 specimen tested with NAAT for M. tb

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cautions regarding NAAT

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a single - NAAT cannot excluded TB especially when there is moderate-high suspicion of TB

do not use for non-respirator specimen or if pt is already being treated

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cultures:

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use to confirm diagnosis of TB

culture all specimens, even if smear is -

results in 4-14 days liquid medium systems used

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reporting TB

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Report of Verified Case of Tuberculosis (RVCT)

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treatment for TB

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2 lines of drugs

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first-line of drugs

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Isoniazid (INH)

Rifampin (RIF)

Pyrazinamide (PZA)

Ethambutol (EMB)

Rifapentine

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problems with 2nd

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less effective

more toxic

more expensive

less available

less convenient

require longer duration of treatment

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Drug Resistant TB

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MDR TB

XDR TB

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what is MDR TB resistant to?

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Isoniazoid

Rifampin

possibly other 1st line drugs

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MDR TB

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Multiple drug resistant TB (MDR TB)

2/3 of cases in Russia, China, India

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XDR TB

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extreme drug resistant TB

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what is XDR TB resistant to?

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Isoniazid and Rifampin

possibly other 1st line drugs

Fluoroquinolones

at least 1 2nd line injectable drug

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DOT

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directly observed therapy

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TB pts must be:

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in isolation until evidence of TB -

need 3 - AFB smears to rule out TB

confirmed TB needs evidence of response to treatment:symptom improvement, AFB smear -

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Mycobacterium bovis

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rare in US

BCG vaccine: Bacillus Calmette-Guerin

Found in cattle

Get TB like symptoms

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Nontuberculous Mycobacteria (Runyon's Groups)

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photochromogens

scotochromognes

non-chromogens

rapid growers

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photochromogens

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develop yellow-orange pigment only when exposed to light for only 1 hr

M. kansasii

M. marinum

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Mycobacterium kansasii

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chronic TB-like illness

photochromogens

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Mycobacterium marinum

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"swimming pool granuloma"

grows at room temp 30-33 C

photochromogens

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scotochromogens

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produce pigment in the dark

M. scofulaceum

M. gordonae

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Mycobacterium scofulaceum

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causes Scofula in neck, infection of lymph nodes in neck

high drug resistance

scotochromogens

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Mycobacterium gordonae

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tap water scotochromogen

rarely pathogenic

can interfere with stains if you use tap water to rinse stains

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non-chromogens

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M. avium complex (MAC)

M. ulcerans

M. haemophilum

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Mycobacterium avium complex

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MAC

M. avium-intracellulare complex

disseminates to skin, intestine, liver, bone marrow

50% of non TB isolates are this

high drug resistance

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Mycobacterium ulcerans

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skin

buruli ulcer

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Mycobacterium haemophilum

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skin with immunocompromised pts

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other non-chromogens

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M. branderi

M. celatum

M. conspicuum

M. gastri

M. genavense

M. heidelbergense

M. malmoense

M. shimoidei

M. simiae

M. triplex

M. xenopi

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rapid growers

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grow within 7 days

M. fortuitum complex (see the most)

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Mycobacterium fortuitum complex

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rapid grower

soft tissue and bone

nail & skin infections: assoc. with nail salons

not contagious, found in soil, water, non-pasturized milk

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other rapid growers

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M. abscessus

M. chelonae

M. immunogenum

M. peregrinum

M. smegmatis

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Leprosy

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found in leper cells

humans are the only host for M. legrae

lepromatous and tuberculoid

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Lab Dx of Leprosy

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AFB

in vivo growth only: armadillis and pads of mouse feet

elimination of other Mycobacterium species to ID

incubation period: 2-30 yrs

Lepromatous form-skin

Tuberuloid form- nerve

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Mycobacterium paratuberculosis

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Crohn's disease