B4.5 NONTUBERCULOUS MYCOBACTERIA Flashcards
What are other names for Nontuberculous Mycobacteria (NTM)?
Atypical Mycobacteria,
Mycobacteria Other Than Tubercle Bacillus (MOTT),
Anonymous,
Unclassified,
Unknown,
Tuberculoid,
Environmental, or
Opportunistic.
Where are NTMs commonly found, and how do they infect individuals?
Found in the environment.
Can colonize the skin, respiratory tract, and gastrointestinal tract of healthy individuals
What is the typical clinical presentation of NTM infections?
Chronic pulmonary disease resembling TB.
Are NTMs transmissible from person to person?
No, NTMs are non-transmissible between individuals.
How are NTMs classified in the Runyon system
By growth rate and colonial pigmentation into four groups.
What are the two growth rates used in the Runyon classification?
Slow growers.
Rapid growers.
They produce pigment when exposed to light.
in the Runyon classification
photochromogens
PHOTOCHROMOGEN SPP
Mycobacterium kansasii
Mycobacterium marinum
known as the Yellow Bacillus
Mycobacterium kansasii
Produces yellow pigment with prolonged light exposure
Mycobacterium kansasii
What is the clinical significance of M. kansasii?
Pulmonary: Chronic cavitary lesions.
Extrapulmonary: Lymphadenitis, skin, soft tissue, and joint infections.
Cultural characteristics of M. kansasii colonies?
Grows on Middlebrook 7H10 agar.
Colonies are slow-growing, smooth to rough, with wavy edges and dark centers.
Prolonged light exposure: Dark red β-carotene crystals on colony surfaces.
Biochemical test results for M. kansasii?
Catalase: Strongly positive (>45 mm in semiquantitative test).
Tween 80 hydrolysis: Positive (3 days).
Nitrate reduction: Positive.
Niacin: Negative.
Pyrazinamidase production: Positive.
Microscopic appearance of M. kansasii?
Long rods with distinct crossbanding.
What is the environmental association and clinical presentation of M. marinum?
Environment: Found in fish and aquariums.
Disease: Swimming pool granuloma, tender red or blue-red subcutaneous nodules on elbows, knees, toes, or fingers.
Optimal growth temperature and culture characteristics for M. marinum?
Grows best at 28–32°C.
Egg-based medium: Smooth to rough and wrinkled.
Middlebrook 7H10/7H11 agar: Smooth colonies
Biochemical test results for M. marinum?
Tween 80 hydrolysis: Positive.
Weakly catalase: Positive.
Niacin: Negative.
Urease: Positive.
Pyrazinamidase: Positive
Drug susceptibility and resistance of M. marinum?
Susceptible: Rifampin and ethambutol.
Resistant: Isoniazid and pyrazinamide.
Intermediate: Streptomycin.
Microscopic appearance of M. marinum?
Moderately long to long rods with crossbarring.
They produce yellow to orange pigment regardless of light exposure.
Scotochromogens
What disease is primarily associated with M. scrofulaceum?
Cervical lymphadenitis in children
Cultural characteristics of M. scrofulaceum
Slow-grower (4–6 weeks).
Grows at 25–37°C.
Smooth colonies with dense centers, light yellow to orange pigment
Microscopic appearance of M. scrofulaceum?
Uniformly stained, acid-fast, medium to long rods.
Biochemical test results for M. scrofulaceum
Tween 80 hydrolysis: Negative.
Urease: Positive.
Catalase: Positive (>45 mm).
Drug resistance of M. scrofulaceum?
Resistant to isoniazid, streptomycin, ethambutol, and p-aminosalicylic acid.
What diseases are associated with M. szulgai?
Pulmonary disease similar to TB.
Extrapulmonary: Lymphadenitis and bursitis
Cultural characteristics of M. szulgai?
At 37°C
Yellow to orange pigment in the absence of light, intensifies with light exposure
Cultural characteristics of M. szulgai?
At 22°C
Nonpigmented or buff in darkness; yellow to orange pigment with light exposure
M. szulgai Grows on what media and characteristics
egg-based media with smooth and rough colonies
Microscopic appearance of M. szulgai?
Medium to long rods with some cross-barring
Biochemical test results for M. szulgai?
Slow hydrolysis of Tween 80.
Nitrate reduction: Positive.
Unable to grow in the presence of 5% NaCl
It commonly contaminates tap water, often found in rinsed sputum samples and bacteriologic smears.
M. gordonae
M. gordonae aka
Tap Water Bacillus
Cultural characteristics of M. gordonae?
Smooth colonies.
Yellow-orange pigment
Biochemical test results for M. gordonae?
Tween 80 hydrolysis: Positive.
Heat-stable catalase: Positive.
Nitrate reduction: Negative.
What species are classified under Nonphotochromogens (Runyon Group III)?
Mycobacterium avium Complex (MAC)
Mycobacterium genavense
Mycobacterium gastri
Mycobacterium haemophilum
Mycobacterium malmoense
Mycobacterium simiae
Mycobacterium ulcerans
Mycobacterium xenopi
Mycobacterium terrae Complex
What are the species in the M. avium complex?
M. avium
M. intracellulare
What disease is caused by M. avium subspecies paratuberculosis?
Johne’s disease (chronic diarrhea in ruminants).
Biochemical test results for M. avium complex?
Heat-stable catalase: Positive.
T2H (2 µg/mL): Positive.
Niacin: Negative.
Nitrate reduction: Negative.
Tween 80 hydrolysis: Negative.
Tellurite reduction: Positive (within 3 days).
Cultural requirements for M. avium subspecies paratuberculosis?
Requires mycobactin-supplemented media for growth
What infections are caused by M. genavense
Disseminated infections in AIDS patients.
Enteritis and genital/soft tissue infections.
Biochemical test results for M. genavense?
Heat-stable catalase: Positive.
Pyrazinamidase: Positive.
Urease: Positive.
Known as the “J Bacillus,” rapidly hydrolyzes Tween 80, and is catalase-negative at 68°C.
M. gastri
Requires hemoglobin or hemin for growth on CHOC agar or LJ medium with 2% ferric ammonium citrate.
M. haemophilum
Optimal growth temperature of M. haemophilum?
28°C to 32°C
What is the drug susceptibility pattern of M. malmoense?
Resistant to: Isoniazid, streptomycin, p-aminosalicylic acid, rifampin.
Susceptible to: Ethambutol and cycloserine.
Biochemical test results for M. malmoense?
Niacin accumulation: Negative.
Nitrate reduction: Negative.
Tween 80 hydrolysis: Positive.
Heat-stable catalase: Positive.
What is the primary source of M. simiae strains?
Originally isolated from monkey lymph nodes
Biochemical test results for M. simiae?
Niacin accumulation: Positive.
Nitrate reduction: Negative.
Heat-stable catalase: Positive.
Slow hydrolysis of Tween 80.
What disease is caused by M. ulcerans?
Buruli ulcer (severe, painless skin ulcers).
Optimal growth temperature of M. ulcerans?
30°C to 33°C.
Biochemical test results for M. ulcerans?
Heat-stable catalase: Positive.
Inert in most other conventional tests.
What is the characteristic appearance of M. xenopi colonies on cornmeal agar?
Bird’s nest appearance with stick-like projections.
Optimal growth temperature of M. xenopi?
42°C (fails to grow at 25°C).
Drug susceptibility of M. xenopi?
Susceptible: Quinolones (e.g., ciprofloxacin, ofloxacin).
Resistant: Ethambutol.
What species are included in the M. terrae complex?
M. terrae (Radish Bacillus).
M. triviale (V Bacillus).
M. nonchromogenicum.
Biochemical test results for the M. terrae complex?
Tween 80 hydrolysis: Positive.
Heat-stable catalase: Positive.
Growth in 5% NaCl: M. triviale only.
Cultural characteristics of M. terrae complex?
M. terrae: Smooth.
M. triviale: Rough and dry.
M. nonchromogenicum: Smooth to rough, white to buff.
What is the general habitat of NTM rapid growers?
Found in dust, soil, and water systems.
What is the mode of transmission (MOT) for NTM rapid growers?
Inoculation into skin and subcutaneous tissues through trauma, injections, surgery, or animal contact.
What is the culture characteristic of NTM rapid growers?
Produce colonies on solid media within 7 days.
What are the microscopy features of NTM rapid growers?
Weakly Gram-positive rods resembling diphtheroids.
What species are classified under NTM rapid growers?
Mycobacterium abscessus subsp. abscessus
Mycobacterium chelonae
Mycobacterium fortuitum
Mycobacterium smegmatis
What is the notable feature of Mycobacterium chelonae infections?
Causes disseminated cutaneous infections in immunocompromised patients
What are the culture characteristics of Mycobacterium chelonae?
Rough or smooth, nonpigmented to buff colonies within 3 to 5 days at 37°C.
What is the biochemical test profile of Mycobacterium chelonae?
3-day arylsulfatase test (+)
Nitrate reduction (-)
Growth on MacConkey agar without crystal violet.
What infections are associated with Mycobacterium abscessus subsp. abscessus?
Chronic lung disease, otitis media, disseminated cutaneous infections, and cystic fibrosis-related infections.
What is the culture characteristic of Mycobacterium fortuitum?
Rough or smooth, nonpigmented, creamy white, or buff colonies within 3 to 5 days at 37°C.
What is the notable feature of Mycobacterium smegmatis on culture?
Produces rough, wrinkled colonies that are nonpigmented or creamy white to buff or pink
What biochemical test distinguishes Mycobacterium fortuitum from
Positive for nitrate reduction and 3-day arylsulfatase test.
What is the microscopy feature of Mycobacterium smegmatis?
Long and tapered or short rods with irregular acid-fastness and sometimes Y-shaped branching.
Noncultivable Nontuberculous Mycobacteria
Mycobacterium leprae
What is the causative agent of leprosy?
Mycobacterium leprae
What is another name for leprosy?
Hansen’s disease
What is the cellular arrangement of Mycobacterium leprae in tissues?
Parallel or palisade arrangement known as “cigar packets.”
What enzyme is present in Mycobacterium leprae that differentiates it from other mycobacteria?
Phenolase
What are the two stable forms of leprosy?
Tuberculoid (TT)
Lepromatous (LL)
Skin lesions with nerve involvement leading to loss of sensation
Effective cell-mediated immune (CMI) response
tuberculoid leprosy
Progressive, symmetric nerve damage and skin lesions
No effective cell-mediated immune (CMI) response
lepromatous leprosy
What is the treatment for lepromatous leprosy?
Diaminodiphenyl sulfone (dapsone), clofazimine, and rifampin
What is the treatment for tuberculoid leprosy?
Dapsone and rifampin
What is the mode of transmission (MOT) for Mycobacterium leprae?
Contact with nasal secretions or ulcer exudates of patients with lepromatous leprosy
Major portal of entry: respiratory tract
What is the pathogenesis of Mycobacterium leprae?
Obligate intracellular bacteria with a strong predilection for nerves, multiplying slowly within mononuclear phagocytes.
What are the five clinical forms of leprosy?
Tuberculoid (TT), Borderline Tuberculoid (BT), Borderline (BB), Borderline Lepromatous (BL), and Lepromatous (LL)
What test is used to detect immune response in leprosy?
Lepromin test
What are the two types of lepromin reactions?
Early Fernandez Reaction: Induration appears in 24–48 hours.
Late Mitsuda Reaction: Indurate nodule appears after 3–4 weeks
What are the specimens used for diagnosing Mycobacterium leprae?
Nasal mucosal smear and skin snips from eyebrows and other sites
Can Mycobacterium leprae be cultured on artificial media?
No, it is non-culturable on artificial media.
What are the experimental methods to grow Mycobacterium leprae?
Footpads of mice (30°C)
Armadillos
What is the optimal growth temperature for Mycobacterium leprae?
30°C
What are the acid-fast staining indices for Mycobacterium leprae?
Bacteriologic Index (BI): Number of organisms per OIF
Morphologic Index (MI): Number of solid-staining cells per 100 bacilli examined
