MYCOBACTERIUM OTHER THAN TUBERCULOSIS Flashcards
• It is medically important to characterize and separate M. tuberculosis from all other species of mycobacteria.
RUNYON CLASSIFICATION
Common mycobacteria
M. tuberculosis
M. leprae
M. avium complex
M. bovis
________on Middlebrook Agar
Mycobacteria pathogenic for humans can be differentiated
(Runyon Groups)
Photochromogenic M. kansasii
Mycobacteria pathogenic for humans can be differentiated
(Runyon Groups) by:
speed of growth (all are slower than most other pathogens) and by
• production of chromogenic pigments (in light, in dark, or none)
New Species Identified: Two new species,(2), were identified between January 2020 and October 2022.
These species were isolated from human sputum samples and are associated with respiratory diseases
Mycobacterium vicinigordonae and Mycobacterium senriense
Breakthrough Antibiotic: Researchers at the National University of Singapore have developed a novel antibiotic named______.
This antibiotic shows promise against hard-to-treat mycobacterial lung infections, particularly those caused by Mycobacterium abscessus.
It disrupts bacterial defenses and exhibits a low frequency of resistance, making it a potentially safer and more effective treatment
COE-PNH2
Opportunistic Mycobacterial Disease
Lymphadenopathy
AIDS related
M. avium complex
M. avium complex
• similar to M. tuberculosis
• the primary cause of tuberculosis in cattle
• Humans can acquire it from cattle by drinking______ if the cow has not been vaccinated
Mycobacterium bovis
unpasteurized milk
• A unique identifying characteristic - it is
susceptible to Thiophene-2-carboxylic acid hydrozide (TCH or T2H),
niacin negative, &
do not reduce nitrate.
M bovis
is resistant to TCH.
Mtb
Source of Bacille Calmette-Guerin (BCG) vaccine
M bovis
Mycobacterium leprae
• Morphology is similar to
M. tuberculosis
• Unculturable on artificial media
Mycobacterium leprae
M leprae
• animal experiments:
• optimal growth temp.
armadillos, mouse’ footpads
30°C
• never been grown in-vitro cultivation due to a loss or disruption of many of the genes required for metabolism
M leprae
M leprae
- a unique carbohydrate antigenic determinant
• surface lipid, phenolic glycolipid 1 (PGL-1)
• surface lipid, phenolic glycolipid 1 (PGL-1) - a unique carbohydrate antigenic determinant
M leprae
M leprae
- a skin test reagent
• leprosin-A
Pathogenesis
• Principal target cell is the Schwann cell (neurolemmocytes, principal glia of the PNS)
Mycobacterium leprae
are capable of intracellular growth
• Resulting in nerve damage: anesthesia, muscle paralysis
• M. leprae
• Repeated injuries/infections of the anesthetic extremities leads to gradual destruction
M leprae
• Infiltration of the bacilli in the skin and cutaneous nerves leads to the formation of visible lesions.
M leprae
Disease progression primarily depends on host’s immune responses - immunological spectrum of the disease
M leprae
Few erythematous or hypopigmented plaques with flat centers and raised, demarcated borders;
peripheral nerve damage with complete sensory loss: visible enlargement of nerves
Tuberculoid Leprosy
Infiltration of lymphocytes around center of epithelial cells; presence of Lang-hans’ cells: few or no acid-fast bacilli observed
Tuberculoid Leprosy
Infectivity - Low
Immune response
Delayed hypersensitivity - Reactivity to lepromin
Immunoglobulin level - Normal
Erythema nodosum leprosum - Absent
Tubercoid leprosy
Infectivity - High
Immune response
Delayed hypersensitivity — Non-Reactivity to lepromin
Immunoglobulin levels - Hypergammaglobinemia
Erythema nodosum leprosum - usually present
Lepromatous Leprosy
Predominantly “foamy” macrophages with few lymphocytes; lack of Lang-hans’ cells; numerous acid-fast bacilli in skin lesions and internal organs
Lepromatous Leprosy
Many erythematous macules, papules, or nodules extensive tissue destruction (e.g., nasal cartilage, bones, ears); diffuse nerve involvement wit/ patchy sensory loss; lack of nerve enlargement
Lepromatous Leprosy
Laboratory Investigation
• Clinical diagnosis - confirmed by _________and by the detection of ______in nasal discharges, scrapings from the nasal mucosa and slit-skin smears
histological examination of skin biopsies
acid-fast bacilli
Laboratory Investigation
- obtained from obvious lesions, the ear lobes and apparently unaffected skin.
Smears
Laboratory Investigation
Stain with_______ method
• number of bacilli seen in OlO recorded as bacillary index
Ziehl-Neelsen
Laboratory Investigation
: patients with clinically active leprosy but no bacilli are seen on slit-skin smear examination
“Paucibacillary” disease
Laboratory Investigation
: those who are bacilli positive at any site
• “Multibacillary” disease
Laboratory Diagnosis
• The number of AFB present/OlF after examination of the entire smear
• Bacteriologic Index (BI)
Laboratory Diagnosis
• The number of solid-staining cells/100 total bacilli examined
• Morphologic index (MI)
Laboratory Diagnosis
aid the clinician in determining the progress of the disease
BI & MI:
Laboratory Diagnosis
- those with dense, uniform staining of the entire bacillus with even sides and rounded ends in which length of the bacillus is at least 5x the width of the bacillus.
Solid-staining cells
Mycobacterium leprae
• Treatment:
•__________- 6-month therapy
• Rifampicin 600 mg*
• Dapsone 100 mg**
Paucibacillary leprosy
Mycobacterium leprae
________- 12-month therapy
• Rifampicin 600 mg*
• Dapsone 100 mg**
• Clofazimine 300 mg* and 50 mg**
Multibacillary leprosy
Runyon Group / (Slow-Growing
M. kansasii
M. marinum
M. simiae
Runyon Group II (Slow-Growing
M. szulgai
M. scrofulaceum
M. xenop
Runyon Group III (Slow-Growing
M. avium complex
M. genavense
M. haemophilum
M. malmoense
Runyon Group IV (Rapid Growers)
M. fortuitum
M. chelonae
M. abscessus
M. mucogenicum
