B1 R&C Lec 3 : Atypical Mycobacteria

Question 1

What is the habitat of Atypical mycobacteria?

Answer 1

widespread in environment (eg.soil & water)

Question 2

What is the pathogenicity of atypical mycobacteria to guinea pigs?

Answer 2

They are not pathogenic for guinea pigs , unlike M.tuberculosis

Question 3

What are the factors that classify the groups of Atypical mycobacteria?

Answer 3

According to:

1. Rate of growth
2. Whether they produce pigment under certain conditions

Question 4

What are the 4 groups of Atypical Mycobacteria?

Answer 4

• Group I (photochromogens):

produce a yellow-orange–pigmented colony only when exposed to light

• Group II (scotochromogens):

produce pigment mainly in dark

• Group III (nonchromogens):

produce little or no yellow-orange pigment, irrespective of the presence or absence of light

• Group IV (Rapidly Growing Mycobacteria)
  *While groups 1,2,3 are slow growing

Question 5

What are the organisms in group 1 ?

Answer 5

1-Mycobacterium kansasii

2-Mycobacterium marinum

Question 6

Mention points about M. kansasii

Answer 6

• It causes lung disease clinically resembling tuberculosis

• Patients are frequently tuberculin skin test– positive

• Its habitat in environment is unknown

• It is susceptible to standard antituberculosis drugs

Question 7

Mention points about M. marinum

Answer 7

• It causes swimming pool granuloma (fish tank granuloma)

• These granulomatous, ulcerating lesions occur in skin at site of abrasions incurred at swimming pools & aquariums.

• The natural habitat of the organism is both fresh & salt water

Question 8

What are the manifestations of M. marinum?

Answer 8

• Usually a single lump or pustule that breaks down to form a crusty sore or abscess

• Other lumps may occur around the initial lesion, particularly along the lines of lymphatic drainage (sporotrichoid forms)

• Most often affects elbows, knees, top of feet, knuckles or finger

Question 9

Which organism is in group 2 ?

Answer 9

Mycobacterium scrofulaceum

Question 10

Mention points about M. scrofulaceum

Answer 10

• It causes scrofula; a granulomatous cervical adenitis, usually in children (M. tuberculosis also causes scrofula.)

• It enters through oropharynx & infects draining lymph nodes.

• Its natural habitat is :

• Environmental water sources

Question 11

What is the organism in Nonchromogens?

Answer 11

M. avium-intracellulare complex ——> Group 3

Question 12

What is M. M. avium-intracellulare complex composed of ?

Answer 12

1. M. avium
2. M. intracellulare

Question 13

What does M. avium-intracellulare complex cause?

Answer 13

• They cause pulmonary disease clinically indistinguishable from tuberculosis, primarily immunocompromised patients such as those with AIDS who have CD4 cell counts of less than 200/mL

• MAI is the most common bacterial cause of disease in AIDS patients

Question 13

What does M. avium-intracellulare complex cause?

Answer 13

• They cause pulmonary disease clinically indistinguishable from tuberculosis, primarily immunocompromised patients such as those with AIDS who have CD4 cell counts of less than 200/mL

• MAI is the most common bacterial cause of disease in AIDS patients

Question 14

What is the habitat of group 3 organisms?

Answer 14

It widespread in environment, including water & soil

Question 15

Nonchromogens are highly resistant to what?

Answer 15

anti tuberculosis drugs

Question 16

What are the drugs of choice in group 3 currently ?

Answer 16

Current drugs of choice are clarithromycin plus one or more of the following: ethambutol, rifabutin, or ciprofloxacin

• As many as six drugs in combination are frequently required for adequate treatment.

Question 16

What are the drugs of choice in group 3 currently ?

Answer 16

Current drugs of choice are clarithromycin plus one or more of the following: ethambutol, rifabutin, or ciprofloxacin

• As many as six drugs in combination are frequently required for adequate treatment.

Question 17

Which drug is used for AIDS prevention?

Answer 17

Clarithromycin

Question 18

Which organisms are rapidly growing?

Answer 18

1-Mycobacterium fortuitum-chelonae complex

2-Mycobacterium abscessus

3-Mycobacterium smegmatis

Question 19

What is Mycobacterium fortuitum-chelonae complex composed of ?

Answer 19

1. M. fortuitum
2. M. chelonae.

Question 20

Where does group IV organisms occur?

Answer 20

It is saprophytes, found in soil & water & rarely cause human disease

Question 21

Where does Skin & soft tissue infections occur?

Answer 21

at site of puncture wounds (e.g., at tattoo sites and injections sites).

Question 22

Mycobacterium fortuitum-chelonae complex are resistant to what?

Answer 22

antituberculosis therapy

Question 23

Which population/s are affected by Mycobacterium fortuitum-chelonae complex?

Answer 23

• Infections occur chiefly in two populations:

(1) immunocompromised patients

(2) individuals with prosthetic hip joints & indwelling catheters.

Question 24

What is the drug of choice of Mycobacterium fortuitum-chelonae complex?

Answer 24

Current drugs of choice are Amikacin plus Doxycycline

• Therapy with multiple drugs in combination plus surgical excision may be required for effective treatment

Question 25

Mycobacterium abscessus is resistant to?

Answer 25

Highly antibiotic-resistant

Question 26

Which group 4 organism is not associated with human disease?

Answer 26

Mycobacterium smegmatis

Question 27

Where is Mycobacterium smegmatis found ?

Answer 27

It is part of normal flora of smegma, material that collects under foreskin of penis

Question 28

What does M. abscessus cause?

Answer 28

causes chronic lung infections, as well as infections of skin, bone& joints

Question 29

How is M. abscessus acquired?

Answer 29

from environment