MYCOBACTERIUM TUBERCULOSIS, MYCOBACTERIUM BOVIS: Acid-Fast Rods
MYCOBACTERIA
Facultative Intracellular Parasites
Catalase (+)
MYCOBACTERIUM TUBERCULOSIS, MYCOBACTERIUM BOVIS: Acid-Fast Rods
Name-Derivation: Forms tubercles in lung.
Epidemiology / At Risk: COMMUNICABLE during primary infection.
Approx. 10 million new cases every year.
Low treatment compliance and thus multi-drug resistance is a big problem.
Urban / HIV / poverty / AIDS
Caring for a single TB patient is extremely expensive.
Manifestations: TUBERCULOSIS
Primary Pulmonary Tuberculosis: Very small number of bugs needed to infect.
Bugs live intracellularly in macrophages. They are strict aerobes and thus prefer the apical lobe of the lung.
Hilar Lymphadenopathy: Macrophages carry the bugs to the hilar lymph nodes.
Unproductive cough, low-grade fever, anorexia, night sweats, fatigue.
Localized granulomas, tubercles, formed in lung.
Miliary Tuberculosis: Disseminated tuberculosis that results from bacteremia.
Likes to go to kidneys, bones, meninges.
Reactivation Tuberculosis: Occurs when quiescent granuloma reactivates. You never get rid of the bug. Seen in immuno-compromised cases, or just spontaneously.
Processing:
Specimen: Not easy to get bugs. Collected by spraying warm saline and withdrawing, right when patient awakes.
Use N-Acetyl-L-Cysteine, an anti-mucus agent, to free bugs from the macrophages in the sputum. Then apply NaOH to remove contaminants. Then centrifuge and resuspend the sediment in a phosphate buffer.
Stain: Acid-Fast Smear is done on the suspension from the prepared specimen above. Acid-Fast rods is not diagnostic, as it may be some other Mycobacterium species.
Culture: Must be obtained to verify M. Tuberculosis. Takes 3-8 weeks for culture results.
Lowenstein-Jensen Medium: Selective medium inhibits growth of normal flora. Penicillin added.
Rough Colonies = More Virulent! This is just like with B. Anthracis.
Liquid Bactec: Faster method, 1-2 weeks. Look for radioactive byproduct of metabolism.
Luciferase gene in phage is used for antibiotic susceptibility testing. Luciferase product releases light when bug is alive and replicating.
Thus, loss of light = susceptible.
Identification:
Strict Aerobes
NIACIN:
M. TUBERCULOSIS: Niacin(+)
M. bovis: Niacin(-)
Virulence:
Obligate Intracellular Parasite: Thus cell mediated immunity is required for defense. Can only replicate within macrophages.
Catalase, Peroxidase
Cord Factor: Lipid. Causes serpentine arrangement of growth.
Inhibits PMN migration
Activates Complement
damages mitochondria
Protect against dessication.
Sulfatides: Glycolipids in cell wall.
Wax-D: Mycolic acid with a little peptidoglycan. Acts as an adjuvant. It is a component of Freund's adjuvant.
Freund's Incomplete Adjuvant: Contains Wax-D.
Freund's Complete Adjuvant: Simple dead M. TUBERCULOSIS, used in animals only.
Siderophores:
Exochelin = extracellular factor released to get Fe+2 from environment.
Mycobactin: Membrane bound, binds to the exochelin to bring it in.
Proteins: Tuberculin is antigenic and immunogenic (but not protective).
Peptidoglycans: arabinagalactans. Antigenic, responsible for hypersensitivity reaction, and contributes to caseous necrosis.
Host Immune Response: Antibodies not protective. Cell-mediated immunity required.
Vaccine / Prevention: BCG Vaccine only administered to high-risk folks. Protection is relative -- not absolute. It prevents bacteremia and dissemination.
Innoculate with live, attenuated M. Bovine strain.
Must be TB-free before getting the vaccine:
100 TU skin test must come back negative. If positive, then we assume the patient has already been exposed.
3 months later, test for hypersensitivity. Test again. Then you can give vaccine.
The BCG vaccine renders the PPD skin test useless.
PPD SKIN TEST: Indicates whether or not you have been exposed to Tuberculosis before.
The BCG vaccine renders the test useless.
1 TU: Very dilute, used with young people, people with demonstrated hypersensitivities, or people showing ocular tuberculosis.
5 TU:
TINE Screening Test. Injected intradermally. If positive after 48 hrs, then do a Mantoux to verify.
Mantoux Test: Diagnostic for TB. Use pen to outline the zone of induration.
> 10 mm: Positive TB test. Has been exposed before.
5-9 mm: Cross-reacting. May be infected with another Mycobacterium.
< 5 mm: Negative TB test.
HIGH-RISK: > 5 mm is positive. For immunocompromised.
LOW-RISK (health-care workers): > 10 mm is positive.
NO-RISK: Healthy businessman having no situational exposure. > 15 mm is positive.
250 TU: Used for prognostic purposes only, to check for adequate cell-mediated response. High amount required in order to elicit a response above baseline presence of the antigen.
Treatment: Multi-Drug Resistance is a big problem! Common to treat with 4 antibiotics. MDR has an 80% mortality rate.
Popular drug-combo: Isoniazid, Rifampin, Pyrazinamide, Ethambutol.
Primary Resistance: Primary infection shows resistance.
Secondary Resistance: Resistance arises in a reactivation disease.
MYCOBACTERIUM AVIUM COMPLEX (MAC):
RUNYON GROUPING: Individual manifestations.
GROUP I: Photochromogenic
M. Kansasii:
Pulmonary disease with single cavitation.
Number one mycobacterium in Nebraska.
PPD: Kansasii is cross-reacting, thus a cross-reacting PPD test does not preclude this organism.
M. Marinum: Likes water and pools, swimming pools. Cutaneous skin lesions.
PPD: Marinum is cross-reacting, thus a cross reacting PPD test does not preclude this organism.
GROUP II: Scotochromogenic
M. Scrofulaceum: Produces cervical lymphadenitis in kids.
Lymph node is usually removed.
PPD: Usually a negative PPD test, i.e. < 5 mm.
GROUP III: Non-Chromogenic
M. AVIUM-INTRACELLULARE: Emerged from HIV epidemic.
ORAL portal of entry with AIDS, usually ------> GI Tract ------> Bacteremia, with concurrent severe anemia, although it is evidently not due to the MAI.
Fatal in AIDS patients. Usually from liver dysfunction.
Pulmonary manifestations identical to Tb.
SENSITIN SKIN TEST: Can be used for MAI. It cross reacts with Tb, but you want to look for the one that yields the larger diameter. If MAI yields the larger diameter, then it is Tb that is cross reacting and the infection is actually MAI.
GROUP IV: Rapid Growers
M. Fortuitum: Cutaneous lesions resembling more of an abscess than an ulcer.
NON-RUNYON:
M. Ulcerans, slow-grower.
Epidemiology / At Risk (GENERAL): Ubiquitous in nature.
A high dose of the bug is needed for infection.
Processing:
Stain: Acid Fast
Culture: Require two to three weeks at least to grow out.
Virulence:
Obligate intracellular parasites
Catalase
Treatment: Generally resistant organisms. Multiple antibiotics required for treatment.
MYCOBACTERIUM LEPRAE:
Epidemiology / At Risk:
Manifestations: LEPROSY
Tuberculoid Leprosy: Small, organized tuberculoid lesions (granulomas) on skin.
Hypopigmented lesions. Cannot be distinguished from contact dermatitis.
Skin, nerves.
Cutaneous anesthesia results from occupations of nerves.
Lepromatous Leprosy: Unable to mount cellular response (anergic) to the bugs, resulting in much worse skin lesions.
No granulomas are formed. "Lepra" cells can be seen.
Affects skin, nerves, eyes.
Processing:
Specimen:
Stain: Acid-Fast
Culture: Has never successfully been grown up in culture!
Can use Armadillo or Mouse footpad models for live hosts.
Identification:
Virulence:
Obligate Intracellular Parasite inside Macrophages. Can inhibit macrophage phagolysosome fusion.
CD8+ Suppressor Cells prevent Granuloma formation in Lepromatous form.
Phenolic glycolipid appears to be key antigen.
Host Immune Response:
Vaccine / Prevention:
SKIN TEST: Antigen was sequestered from Armadillos, who are quite affected Leprosy.
Skin Test can be used only for prognosis. A good (> 10 mm) response indicates that patient can mount a good response, so lepromatous form should result.
Treatment: Sulfa drugs.
Facultative Intracellular Parasites
Catalase (+)
MYCOBACTERIUM TUBERCULOSIS, MYCOBACTERIUM BOVIS: Acid-Fast Rods
Name-Derivation: Forms tubercles in lung.
Epidemiology / At Risk: COMMUNICABLE during primary infection.
Approx. 10 million new cases every year.
Low treatment compliance and thus multi-drug resistance is a big problem.
Urban / HIV / poverty / AIDS
Caring for a single TB patient is extremely expensive.
Manifestations: TUBERCULOSIS
Primary Pulmonary Tuberculosis: Very small number of bugs needed to infect.
Bugs live intracellularly in macrophages. They are strict aerobes and thus prefer the apical lobe of the lung.
Hilar Lymphadenopathy: Macrophages carry the bugs to the hilar lymph nodes.
Unproductive cough, low-grade fever, anorexia, night sweats, fatigue.
Localized granulomas, tubercles, formed in lung.
Miliary Tuberculosis: Disseminated tuberculosis that results from bacteremia.
Likes to go to kidneys, bones, meninges.
Reactivation Tuberculosis: Occurs when quiescent granuloma reactivates. You never get rid of the bug. Seen in immuno-compromised cases, or just spontaneously.
Processing:
Specimen: Not easy to get bugs. Collected by spraying warm saline and withdrawing, right when patient awakes.
Use N-Acetyl-L-Cysteine, an anti-mucus agent, to free bugs from the macrophages in the sputum. Then apply NaOH to remove contaminants. Then centrifuge and resuspend the sediment in a phosphate buffer.
Stain: Acid-Fast Smear is done on the suspension from the prepared specimen above. Acid-Fast rods is not diagnostic, as it may be some other Mycobacterium species.
Culture: Must be obtained to verify M. Tuberculosis. Takes 3-8 weeks for culture results.
Lowenstein-Jensen Medium: Selective medium inhibits growth of normal flora. Penicillin added.
Rough Colonies = More Virulent! This is just like with B. Anthracis.
Liquid Bactec: Faster method, 1-2 weeks. Look for radioactive byproduct of metabolism.
Luciferase gene in phage is used for antibiotic susceptibility testing. Luciferase product releases light when bug is alive and replicating.
Thus, loss of light = susceptible.
Identification:
Strict Aerobes
NIACIN:
M. TUBERCULOSIS: Niacin(+)
M. bovis: Niacin(-)
Virulence:
Obligate Intracellular Parasite: Thus cell mediated immunity is required for defense. Can only replicate within macrophages.
Catalase, Peroxidase
Cord Factor: Lipid. Causes serpentine arrangement of growth.
Inhibits PMN migration
Activates Complement
damages mitochondria
Protect against dessication.
Sulfatides: Glycolipids in cell wall.
Wax-D: Mycolic acid with a little peptidoglycan. Acts as an adjuvant. It is a component of Freund's adjuvant.
Freund's Incomplete Adjuvant: Contains Wax-D.
Freund's Complete Adjuvant: Simple dead M. TUBERCULOSIS, used in animals only.
Siderophores:
Exochelin = extracellular factor released to get Fe+2 from environment.
Mycobactin: Membrane bound, binds to the exochelin to bring it in.
Proteins: Tuberculin is antigenic and immunogenic (but not protective).
Peptidoglycans: arabinagalactans. Antigenic, responsible for hypersensitivity reaction, and contributes to caseous necrosis.
Host Immune Response: Antibodies not protective. Cell-mediated immunity required.
Vaccine / Prevention: BCG Vaccine only administered to high-risk folks. Protection is relative -- not absolute. It prevents bacteremia and dissemination.
Innoculate with live, attenuated M. Bovine strain.
Must be TB-free before getting the vaccine:
100 TU skin test must come back negative. If positive, then we assume the patient has already been exposed.
3 months later, test for hypersensitivity. Test again. Then you can give vaccine.
The BCG vaccine renders the PPD skin test useless.
PPD SKIN TEST: Indicates whether or not you have been exposed to Tuberculosis before.
The BCG vaccine renders the test useless.
1 TU: Very dilute, used with young people, people with demonstrated hypersensitivities, or people showing ocular tuberculosis.
5 TU:
TINE Screening Test. Injected intradermally. If positive after 48 hrs, then do a Mantoux to verify.
Mantoux Test: Diagnostic for TB. Use pen to outline the zone of induration.
> 10 mm: Positive TB test. Has been exposed before.
5-9 mm: Cross-reacting. May be infected with another Mycobacterium.
< 5 mm: Negative TB test.
HIGH-RISK: > 5 mm is positive. For immunocompromised.
LOW-RISK (health-care workers): > 10 mm is positive.
NO-RISK: Healthy businessman having no situational exposure. > 15 mm is positive.
250 TU: Used for prognostic purposes only, to check for adequate cell-mediated response. High amount required in order to elicit a response above baseline presence of the antigen.
Treatment: Multi-Drug Resistance is a big problem! Common to treat with 4 antibiotics. MDR has an 80% mortality rate.
Popular drug-combo: Isoniazid, Rifampin, Pyrazinamide, Ethambutol.
Primary Resistance: Primary infection shows resistance.
Secondary Resistance: Resistance arises in a reactivation disease.
MYCOBACTERIUM AVIUM COMPLEX (MAC):
RUNYON GROUPING: Individual manifestations.
GROUP I: Photochromogenic
M. Kansasii:
Pulmonary disease with single cavitation.
Number one mycobacterium in Nebraska.
PPD: Kansasii is cross-reacting, thus a cross-reacting PPD test does not preclude this organism.
M. Marinum: Likes water and pools, swimming pools. Cutaneous skin lesions.
PPD: Marinum is cross-reacting, thus a cross reacting PPD test does not preclude this organism.
GROUP II: Scotochromogenic
M. Scrofulaceum: Produces cervical lymphadenitis in kids.
Lymph node is usually removed.
PPD: Usually a negative PPD test, i.e. < 5 mm.
GROUP III: Non-Chromogenic
M. AVIUM-INTRACELLULARE: Emerged from HIV epidemic.
ORAL portal of entry with AIDS, usually ------> GI Tract ------> Bacteremia, with concurrent severe anemia, although it is evidently not due to the MAI.
Fatal in AIDS patients. Usually from liver dysfunction.
Pulmonary manifestations identical to Tb.
SENSITIN SKIN TEST: Can be used for MAI. It cross reacts with Tb, but you want to look for the one that yields the larger diameter. If MAI yields the larger diameter, then it is Tb that is cross reacting and the infection is actually MAI.
GROUP IV: Rapid Growers
M. Fortuitum: Cutaneous lesions resembling more of an abscess than an ulcer.
NON-RUNYON:
M. Ulcerans, slow-grower.
Epidemiology / At Risk (GENERAL): Ubiquitous in nature.
A high dose of the bug is needed for infection.
Processing:
Stain: Acid Fast
Culture: Require two to three weeks at least to grow out.
Virulence:
Obligate intracellular parasites
Catalase
Treatment: Generally resistant organisms. Multiple antibiotics required for treatment.
MYCOBACTERIUM LEPRAE:
Epidemiology / At Risk:
Manifestations: LEPROSY
Tuberculoid Leprosy: Small, organized tuberculoid lesions (granulomas) on skin.
Hypopigmented lesions. Cannot be distinguished from contact dermatitis.
Skin, nerves.
Cutaneous anesthesia results from occupations of nerves.
Lepromatous Leprosy: Unable to mount cellular response (anergic) to the bugs, resulting in much worse skin lesions.
No granulomas are formed. "Lepra" cells can be seen.
Affects skin, nerves, eyes.
Processing:
Specimen:
Stain: Acid-Fast
Culture: Has never successfully been grown up in culture!
Can use Armadillo or Mouse footpad models for live hosts.
Identification:
Virulence:
Obligate Intracellular Parasite inside Macrophages. Can inhibit macrophage phagolysosome fusion.
CD8+ Suppressor Cells prevent Granuloma formation in Lepromatous form.
Phenolic glycolipid appears to be key antigen.
Host Immune Response:
Vaccine / Prevention:
SKIN TEST: Antigen was sequestered from Armadillos, who are quite affected Leprosy.
Skin Test can be used only for prognosis. A good (> 10 mm) response indicates that patient can mount a good response, so lepromatous form should result.
Treatment: Sulfa drugs.