WEEK 7: MYCOBACTERIA Flashcards
- Non-motile, non-spore forming slender, slightly curved or straight, rod- shaped organisms that have tendency to clump
- The cell wall has extremely high lipid content; thus, mycobacterial cells resist staining with commonly used basic aniline dyes, such as those used in the Gram stain, at room temperature.
- take up dye with increased staining time or application of heat but resist decolorization with acid-ethanol
- This characteristic is referred to as acid fastness—hence, the term AFB
- are strictly aerobic, but increased carbon dioxide (CO2) will enhance the growth of some species.
Mycobacteria
Mycobacterium tuberculosis Complex (5)
M. tuberculosis
M. bovis
M. africanum
M. canettii
M. microti
The primary source of BCG (Bacillus CalmetteGuérin) vaccine
M. bovis
A PPD skin test is reactive if the induration is?
20mm
are acquired from persons with active disease who are excreting viable bacilli by
coughing, sneezing or talking.
Tubercle bacilli
is usually a disease of the respiratory tract
TB
an unexplained pleural effusion with mononuclear pleurocytosis, manifests as cough, fever, and chest pain, resembling the presentation
of bacterial pneumonia
Pleurisy
an organization of lymphocytes, macrophages, fibroblasts, and capillaries.
granuloma
refers to the seeding of many organs outside the pulmonary tree with AFB through hematogenous spread
Miliary TB
- TB is usually a disease of the respiratory tract.
- Tubercle bacilli are acquired from persons with active disease who are excreting viable bacilli by coughing, sneezing or talking.
- hard tubercle or granuloma may be formed
- The granuloma is an organization of lymphocytes, macrophages, fibroblasts, and capillaries.
- With granuloma formation, healing occurs, as well as fibrosis, encapsulation, and
calcification, with scar formation as a reminder of the past infection. - In infected individuals, there is a potential for reactivation of TB.
- Clinical diagnosis of primary TB: positive PPD skin test.
diagnosis is confirmed by stained smear and culture of sputum, gastric aspirates, or bronchoscopy specimens.
Mycobacterium tuberculosis
Skeletal TB of the spine is referred to as?
Pott disease
- Colonies are typically raised, with a dry, rough
appearance. - The colonies are nonpigmented and classically described as being buff-colored
- Optimal growth occurs at 35° C to 37° C.
- Positive for niacin accumulation
- reduction of nitrate to nitrite
- Production of catalase
- Grows on thiophene-2-carboxylic acid hydrazide
(T2H)
Mycobacterium tuberculosis
➢ 21 days of incubation at 37° C.
➢ niacin-negative
➢ do not reduce nitrate
➢ do not grow in the presence of (T2H)
thiophene-2-carboxylic acid hydrazide
Mycobacterium bovis
- Miliary TB refers to the seeding of many organs
outside the pulmonary tree with AFB through hematogenous spread. - Almost any organ of the body can be infected by
M. tuberculosis - Pleurisy, an unexplained pleural effusion with
mononuclear pleurocytosis, manifests as cough, fever, and chest pain, resembling the presentation of bacterial pneumonia. - Lymphadenitis
- Genitourinary TB
- Skeletal TB of the spine is referred to as Pott disease.
- Meningitis
- Cerebrospinal fluid (CSF) examination usually reveals an elevated protein level, decreased glucose level, and a predominance of lymphocytes
Extrapulmonary Tuberculosis
TRUE OR FALSE
Almost any organ of the body can be infected by
M. tuberculosis.
TRUE
- TB primarily in cattle but also in other ruminants,
as well as in dogs, cats, swine, parrots, and
humans. - The disease in humans closely resembles that
caused by M. tuberculosis and is treated similarly.
Mycobacterium bovis
- Vank’s disease
- resistant to at least two of the most powerful first anti-TB drugs, INH and RMP
MDR-TB
M. bacteremicum
M. canariasense
M. cosmeticum
M. monacense
M. neoaurum
M. mageritense/M. wolinskyi Group
M. mageritense
M. wolinskyi
Early Pigmented
resistant to INH and RMP plus any fluoroquinolones and at least one injectable second line drugs (amikacin, kanamycin, or capreomycin)
XDR-TB
- atypical mycobacteria or mycobacteria other than
tuberculosis (mott) - found in the environment that colonize the skin,
respiratory tract and gi of healthy individuals - chronic pulmonary disease resembling tb
- non transmissible from person to person
- aids contributed to incidence to ntm disease
Non-tuberculous Mycobacteria
M. bohemicum
M. celatum
M. genavense
M. haemophilum
M. heidelbergense
M. interjectum
M. intermedium
M. kansasii
M. lentiflavum
M. malmoense
M. marinum
M. scrofulaceum
M. simiae
M. szulgai
M. terrae complex (M. arupense, M. heraklionense, M. kumamotense)
M. ulcerans
M. xenopi
Slow Growers (Other than Mycobacterium avium
Complex)
- M. intracellulare
- environmental saprophytes and have been
recovered from soil, water, house dust, and other
environmental sources - is a cause of disease in poultry and
swine - Zoonotic - the cells are short, coccobacillary, and uniformly stained, without beading or banding
- production of a heatstable catalase and the ability
to grow on media containing 2 μg/mL of T2H
Mycobacterium avium complex
- M. fortuitum Group
M boenickei
M. brisbanense
M. fortuitum
M. houstonense
M. neworleansense
M. peregrinum
M. porcinum
M. senegalense
M. septicum
M. setense
- M. chelonae/M. abscessus Group
M. abscessus subsp. abscessus
M. abscessus subsp. bolletii
M. chelonae
M. franklinii
M. immunogenum
M. salmoniphilum
- M. mucogenicum Group
M. aubagnense
M. mucogenicum
M. phocaicum
- M. smegmatis Group
M. goodii
M. smegmatis
Rapid Growers
NTM colonies that
develop pigment
on exposure to
light after being
grown in the dark
and take longer
than 7 days to
appear on solid
media
are slow-growing NTM that produce colonies that require light to form pigment.
I. Photochromogens
NTM colonies that
develop pigment
in the dark or light
and take longer
than 7 days to
appear on solid
media
are slow-growing NTM that produce pigmented colonies whether grown in the dark or the light.
II. Scotochromogen
- chronic pulmonary disease and cervical lymphadenitis
- resistant to isoniazid, streptomycin, p-aminosalicylic acid, and rifampin and susceptible
to ethambutol and cycloserine. - short coccobacillus without cross bands on
acid-fast–stained smears. - Colonies are smooth glistening, and opaque, with
dense centers
Mycobacterium malmoense
NTM colonies that
are nonpigmented
regardless of whether they are grown in the dark
or light and take
longer than 7 days to appear on solid media
are slow-growing NTM that produce unpigmented colonies whether grown
in the dark or the light.
III. Nonphotochromogens
NTM colonies that grow on solid media and take fewer than 7 days to appear
IV. Rapid growers
- Causative agent of Johne disease, an intestinal
infection occurring as a chronic diarrhea in cattle,
sheep, goats, and other ruminants. - very slow growth rate (3 to 4 months)
- Needs mycobactin-supplemented medium for
primary isolation
Mycobacterium avium subsp. paratuberculosis
- cause of disseminated infections in patients with
AIDS - enteritis and genital and soft tissue infections
- Middlebrook 7H11 agar supplemented with
mycobactin. - heat-stable catalase, pyrazinamidase, and urease
- positive
Mycobacterium genavense
- a multidrug regimen of isoniazid, rifampin, and
ethambutol is currently recommended - long rods with distinct crossbanding
- colonies appear smooth to rough, with characteristic wavy edges and dark centers when grown on Middlebrook 7H10 agar
- Colonies are photochromogenic
- With prolonged exposure to light, most strains
form dark red crystals of β–carotene on the surface
of and inside the colony. - strongly catalase-positive
- hydrolyze Tween 80 in 3 days
- strong nitrate reduction
- Pyrazinamidase production
Mycobacterium kansasii
- Submandibular lymphadenitis, subcutaneous nodules, painful swellings, ulcers progressing to abscesses, and draining fistulas are often the clinical manifestations.
- A unique characteristic of this organism is its requirement for hemoglobin or hemin for growth.
- chocolate (CHOC) agar, Mueller-Hinton agar with
5% Fildes enrichment, and Löwenstein-Jensen (LJ)
medium containing 2% ferric ammonium citrate.
Middlebrook 7H10 agar with an X factor disk - Optimal growth temperature is 28° C to 32° C; little or no growth occurs at 37° C.
- cells are strongly acid-fast, short, occasionally
curved bacilli without banding or beading, and
arranged in tight clusters or cords
Mycobacterium haemophilum.
- cervical lymphadenitis in children
- resistant to isoniazid, streptomycin, ethambutol,
and p-aminosalicylic acid when tested in vitro. - The organism grows slowly (4 to 6 weeks) at incubation temperatures ranging from 25° to 37° C
Mycobacterium scrofulaceum
- isolated from the lymph nodes of monkeys
- Colonies on Middlebrook 7H10 agar are thin,
transparent or tiny, and filamentous
Mycobacterium simiae
- is a rare cause of mycobacteriosis, also referred to as Buruli ulcer
- acid-fast cells are long, without beading or
crossbanding
Mycobacterium ulcerans
- has been implicated in
diseases of fish and isolated from aquariums. - Cutaneous infections in humans occur when traumatized skin comes into contact with salt water
or inadequately chlorinated fresh water containing
the organism. - tender red or blue-red subcutaneous nodule, or
swimming pool granuloma, usually occurs on the
elbow, knee, toe, or finger - susceptible to rifampin and ethambutol, resistant
to isoniazid and pyrazinamide, and partially
resistant or intermediate to streptomycin - Cells of _______ are moderately long to long
rods with cross barring. - is photochromogenic; young colonies
- Colonies grown in or exposed to light develop a
deep yellow color. - Growth is optimum at incubation temperatures of
28° C to 32° C. - none reduces nitrate or produces heat-stable
catalase - The organisms hydrolyze Tween 80 and produce
urease and pyrazinamidase.
Mycobacterium marinum
- recovered from hot and cold-water taps (including
water storage tanks of hospitals) - susceptible to the quinolones (ciprofloxacin,
ofloxacin); some isolates are susceptible to vancomycin, erythromycin, or cefuroxime - Colonies on Middlebrook 7H10 agar are small,
with dense centers and filamentous edges. - cornmeal-glycerol agar reveals distinctive round
colonies with branching and filamentous extensions;
aerial hyphae are usually seen in rough colonies. - Young colonies grown on cornmeal agar have a
bird’s nest appearance, with characteristic stick-like
projections.
Mycobacterium xenopi
seen in patients with cystic fibrosis (CF)
M. abscessus
have been associated with a variety of infections of the skin, lungs, bone, central
nervous system, and prosthetic heart valves.
M. chelonae
- M. abscessus subsp. abscessus (formerly M.
abscessus), M. chelonae, and M. fortuitum. - M. chelonae have been associated with a variety
of infections of the skin, lungs, bone, central
nervous system, and
prosthetic heart valves. - M. abscessus seen in patients with cystic fibrosis
(CF) - tap water is an important reservoir
- positive 3-day arylsulfatase test, no reduction of
nitrate, and growth on MacConkey agar without
crystal violet
Mycobacterium chelonae–Mycobacterium abscessus Group
- M. ____, M. peregrinum, and an unnamed third species.
- isolated from water, soil, and dust
- associated with localized cutaneous infections
- Middlebrook 7H11 agars after 1 to 2 days of
incubation colonies with branching filamentous
extensions and rough colonies with short aerial
hyphae. - pleomorphic, ranging from long and tapered to
short, thick rods partially acid-fast - positive 3-day arylsulfatase test and reduction of
nitrate
Mycobacterium fortuitum Group
- contains two species, M.
smegmatis and M. goodie. - M. smegmatis has been implicated in rare cases
of pulmonary, skin, soft tissue, and bone infections. - cells are long and tapered or short rods with irregular acid fastness. Occasionally rods are curved with branching or Y-shaped forms; swollen, with deeper staining, beaded, or ovoid forms are sometimes seen.
- Colonies appearing on egg medium after 2 to 4 days are usually rough, wrinkled, or coarsely folded; smooth, glistening, butyrous colonies may also be
seen. - negative arylsulfatase reaction, positive iron
uptake, ability to reduce nitrate, and growth in the
presence of 5% NaCl and on MacConkey agar without crystal violet
Mycobacterium smegmatis Group
appear to be more commonly diagnostic than washing or biopsy, possibly because of an inhibitory effect on the mycobacteria by lidocaine used in adults during bronchoscopy or
of dilution of the specimen with saline
Brushings
- this is recommended because children have difficulty producing sputum
- should be obtained in the morning after an overnight fast
gastric aspiration
specimen should be neutralized with ________ _______ or another
buffer to pH __.0 as soon as possible after specimen collection.
sodium carbonate, 7.0
stool patients with AIDS, who may be at risk for developing disseminated mycobacterial disease resulting from ____________ _________ _______
Mycobacterium avium complex
0 (1) to liquefy the sample through digestion of the
proteinaceous material
0 (2) to allow the chemical decontaminating agent to contact and kill the nonmycobacterial organisms
Digestion and Decontamination of Specimens
Usual concentration 2%, 3%, or 4%—serves as a digestant and decontaminating agent
Sodium Hydroxide
0 A combination of a liquefying agent, such as N-acetyl-L-cysteine (NALC) or dithiothreitol, plus NaOH is commonly used.
0 Treatment with mucolytic agents such as NALC splits mucoprotein, allowing greater sedimentation
N-Acetyl-L-cysteine
- Another digestant-decontamination benzalkonium chloride
(Zephiran) combined with trisodium phosphate (Z-TSP). - TSP liquefies sputum rapidly
- shortens the exposure time and effectively
destroys many contaminants, with little bactericidal effect on the
tubercle bacilli.
Benzalkonium Chloride
5%, is used to decontaminate specimens contaminated with Pseudomonas aeruginosa, such as sputum specimens from patients with Cystic fibrosis.
Oxalic Acid
The conventional acid-fast staining methods (2)
Ziehl-Neelsen and Kinyoun stains
In Ziehl-Neelsen and Kinyoun stains, what is the primary stain, decolorizing agent, and counterstain?
carbolfuchsin
acid-alcohol
methylene blue
staining procedure involves the application of heat with the carbolfuchsin stain
Ziehl-Neelsen
acid-fast stain is a cold stain
Kinyoun
what is the minimum amount of field before a slide is called negative?
300 fields
replication time of M. tuberculosis
20 to 22 hours
Most pathogenic mycobacteria require how many weeks of incubation?
2 to 6 weeks
growth of M. tuberculosis is enhanced by an atmosphere of?
5% to 10% CO2
Mycobacteria require a pH between?
6.5 and 6.8
does not grow on media used routinely to isolate mycobacteria and requires extended incubation (6 to 8
weeks)
M. genavense
fails to grow on artificial media.
M. leprae
Serum albumin agar media, such as Middlebrook 7H10
and 7H11 agars
Agar-Based Media
also contains 0.1% casein
hydrolysate, which improves the recovery of isoniazid-
resistant strains of M. tuberculosis
Middlebrook 7H11 medium
TRUE OR FLASE
Mycobacterium spp. grow more rapidly in solid
medium
FLASE (LIQUID MEDIA)
2 nonselective liquid media used for subculturing
stock strains
Middlebrook 7H9 broth and Dubos Tween albumin
have a variable appearance, with glossy whitish colonies
often occurring with smaller translucent colonies
Colonies of Mycobacterium avium complex
most commonly used biochemical test for the identification of MTB
niacin
In Iron Uptake, what color does the colonies appear in a positive reaction?
rusty brown
The test is most useful in
distinguishing M. chelonae, which is generally negative
Iron Uptake
Most members of the genus Mycobacterium possess this
enzyme
arylsulfatase
- Detection of urease activity can be used to distinguish
M. scrofulaceum, urease-positive, from M. gordonae,
urease-negative. - A pink to red color is indicative of a positive reaction.
Urease
- is a precursor in the synthesis of chloramphenicol.
- selectively inhibits the M. tuberculosis complex
NAP
this organism is susceptible to lower concentrations of T2H than MTB
M. bovis
- High salt concentration (5% NaCl) in egg-based media (e.g., LJ) inhibits the growth of most mycobacteria.
- M. flavescens, M. triviale, and most rapidly growing Mycobacterium spp. are exceptions that do grow in the presence of 5% NaCl.
Sodium Chloride Tolerance
has been used for many years to determine an
individual’s exposure to M. tuberculosis
tuberculin skin test