4.5 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.
What are photochromogens?
They produce pigment when exposed to light.
What are the PHOTOCHROMOGEN species?
Mycobacterium kansasii, Mycobacterium marinum.
What is known as the Yellow Bacillus?
Mycobacterium kansasii.
What is the clinical significance of M. kansasii?
Pulmonary: Chronic cavitary lesions. Extrapulmonary: Lymphadenitis, skin, soft tissue, and joint infections.
What are the 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.
What are the 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.
What is the 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.
What is the 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.
What are the biochemical test results for M. marinum?
Tween 80 hydrolysis: Positive. Weakly catalase: Positive. Niacin: Negative. Urease: Positive. Pyrazinamidase: Positive.
What is the drug susceptibility and resistance of M. marinum?
Susceptible: Rifampin and ethambutol. Resistant: Isoniazid and pyrazinamide. Intermediate: Streptomycin.
What is the microscopic appearance of M. marinum?
Moderately long to long rods with crossbarring.
What are the characteristics of scotochromogens?
They produce yellow to orange pigment regardless of light exposure.
What disease is primarily associated with M. scrofulaceum?
Cervical lymphadenitis in children.
What are the 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.
What is the microscopic appearance of M. scrofulaceum?
Uniformly stained, acid-fast, medium to long rods.
What are the biochemical test results for M. scrofulaceum?
Tween 80 hydrolysis: Negative. Urease: Positive. Catalase: Positive (>45 mm).
What is the 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.
What are the cultural characteristics of M. szulgai at 37°C?
Yellow to orange pigment in the absence of light, intensifies with light exposure.
What are the cultural characteristics of M. szulgai at 22°C?
Nonpigmented or buff in darkness; yellow to orange pigment with light exposure.
What media does M. szulgai grow on and what are its characteristics?
Egg-based media with smooth and rough colonies.
What is the microscopic appearance of M. szulgai?
Medium to long rods with some cross-barring.
What are the biochemical test results for M. szulgai?
Slow hydrolysis of Tween 80. Nitrate reduction: Positive. Unable to grow in the presence of 5% NaCl.
What is the environmental association of M. gordonae?
It commonly contaminates tap water, often found in rinsed sputum samples and bacteriologic smears.
What is M. gordonae also known as?
Tap Water Bacillus.
What are the cultural characteristics of M. gordonae?
Smooth colonies. Yellow-orange pigment.
What are the 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).
What are the 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).
What are the 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.
What are the biochemical test results for M. genavense?
Heat-stable catalase: Positive. Pyrazinamidase: Positive. Urease: Positive.
What is M. gastri known as?
The ‘J Bacillus,’ rapidly hydrolyzes Tween 80, and is catalase-negative at 68°C.
What does M. haemophilum require for growth?
Requires hemoglobin or hemin for growth on CHOC agar or LJ medium with 2% ferric ammonium citrate.
What is the 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.
What are the 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.
What are the 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).
What is the optimal growth temperature of M. ulcerans?
30°C to 33°C.
What are the 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.
What is the optimal growth temperature of M. xenopi?
42°C (fails to grow at 25°C).
What is the 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.
What are the biochemical test results for the M. terrae complex?
Tween 80 hydrolysis: Positive. Heat-stable catalase: Positive. Growth in 5% NaCl: M. triviale only.
What are the cultural characteristics of the 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?
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.
What is the 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).
What is the clinical presentation of tuberculoid leprosy?
Skin lesions with nerve involvement leading to loss of sensation. Effective cell-mediated immune (CMI) response.
What is the clinical presentation of lepromatous leprosy?
Progressive, symmetric nerve damage and skin lesions. No effective cell-mediated immune (CMI) response.
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.
