B1 R&C Lec 3 : Atypical Mycobacteria Flashcards
What is the habitat of Atypical mycobacteria?
widespread in environment (eg.soil & water)
What is the pathogenicity of atypical mycobacteria to guinea pigs?
They are not pathogenic for guinea pigs , unlike M.tuberculosis
What are the factors that classify the groups of Atypical mycobacteria?
According to:
- Rate of growth
- Whether they produce pigment under certain conditions
What are the 4 groups of Atypical Mycobacteria?
• 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
What are the organisms in group 1 ?
1-Mycobacterium kansasii
2-Mycobacterium marinum
Mention points about M. kansasii
• 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
Mention points about M. marinum
• 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
What are the manifestations of M. marinum?
• 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
Which organism is in group 2 ?
Mycobacterium scrofulaceum
Mention points about M. scrofulaceum
• 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
What is the organism in Nonchromogens?
M. avium-intracellulare complex ——> Group 3
What is M. M. avium-intracellulare complex composed of ?
- M. avium
- M. intracellulare
What does M. avium-intracellulare complex cause?
• 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
What does M. avium-intracellulare complex cause?
• 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
What is the habitat of group 3 organisms?
It widespread in environment, including water & soil
Nonchromogens are highly resistant to what?
anti tuberculosis drugs
What are the drugs of choice in group 3 currently ?
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.
What are the drugs of choice in group 3 currently ?
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.
Which drug is used for AIDS prevention?
Clarithromycin
Which organisms are rapidly growing?
1-Mycobacterium fortuitum-chelonae complex
2-Mycobacterium abscessus
3-Mycobacterium smegmatis
What is Mycobacterium fortuitum-chelonae complex composed of ?
- M. fortuitum
- M. chelonae.
Where does group IV organisms occur?
It is saprophytes, found in soil & water & rarely cause human disease
Where does Skin & soft tissue infections occur?
at site of puncture wounds (e.g., at tattoo sites and injections sites).
Mycobacterium fortuitum-chelonae complex are resistant to what?
antituberculosis therapy
Which population/s are affected by Mycobacterium fortuitum-chelonae complex?
• Infections occur chiefly in two populations:
(1) immunocompromised patients
(2) individuals with prosthetic hip joints & indwelling catheters.
What is the drug of choice of Mycobacterium fortuitum-chelonae complex?
Current drugs of choice are Amikacin plus Doxycycline
- Therapy with multiple drugs in combination plus surgical excision may be required for effective treatment
Mycobacterium abscessus is resistant to?
Highly antibiotic-resistant
Which group 4 organism is not associated with human disease?
Mycobacterium smegmatis
Where is Mycobacterium smegmatis found ?
It is part of normal flora of smegma, material that collects under foreskin of penis
What does M. abscessus cause?
causes chronic lung infections, as well as infections of skin, bone& joints
How is M. abscessus acquired?
from environment
