Mycobacterium & NTM 🫁 Flashcards
Mycobacterium tuberculosis and Non-Tuberculosis Mycobacteria
aka Koch’s bacillus
Mycobacterium tuberculosis
Major virulence factor of Mycobacterium tuberculosis
cord factor
Mycobac generation time?
> 12hrs - grows slowly bc of their hydrophobic cell surface
Mycobac pH requirement on (culture media)
6.5-6.8
2 GROUPS OF MYCOBACTERIA:
- Mycobacterium tuberculosis complex (MTC)
- Nontuberculosis mycobacteria (NTM, MOTT)
Mycobacterium tuberculosis major virulence factor
cord factor
Which of the following is (are) fluorescent stain(s) used in the detection of the mycobacteria?
a. Auramine-rhodamine
b. Kinyoun’s
c. Ziehl-Neelsen
d. Both b and c
Auramine-rhodamine
A nonpigmented mycobacterium is isolated that reduces nitrate
to nitrite and is niacin-positive. You should suspect:
a. M. kansasii
b. M. xenopi
c. M. tuberculosis
d. M. avium complex
c. M. tuberculosis
The causative agent of Hansen disease:
a. Is highly contagious
b. Readily grows on most mycobacterial media
c. Grows best at core body temperature (37°C)
d. None of the above
d. None of the above
The skin test for tuberculosis:
a. Detects antibodies to mycobacterial antigens
b. Detects a cell-mediated immune response to mycobacterial
antigens
c. Uses the bacillus of Calmette-Guérin strain as the antigen
source
d. Both a and b
b. Detects a cell-mediated immune response to mycobacterial
antigens
what are the MYCOBACTERIUM TUBERCULOSIS COMPLEX ??
(TBACM)
- Mycobacterium tuberculosis
- Mycobacterium bovis
- Mycobacterium africanum
- Mycobacterium canetti
- Mycobacterium microti
It has the longest replication time among the
mycobacteria (20-22 hours)
Mycobacterium tuberculosis
ID:
Culture: slow growing, buff in color raised and
dry – “cauliflower colonies”, rough colonies
exhibit “cording”
(curved strands of bacilli)
Mycobacterium tuberculosis
ID:
Biochemical tests:
o** (+)** niacin and nitrate reduction😌
o growth on T2H
o (-) 68°C catalase test 😉
o It is inhibited by nitroimidazopyran (NAP)
Mycobacterium tuberculosis
✍️Macrophage destroys intracellular mycobacteria
✍️Macrophage destroys intracellular mycobacteria
Part 1/2
✍️MTB does not produce toxin.
The pathologic features of TB are the result of hypersensitivity reaction to mycobacterial antigen.
Which causes :
⬇️ Antigen
⬆️ Hypersensitivity
✅Granuloma
✅Calcification - as granuloma healing occurs - with scar formation as a reminder of the past infection.
Part 2/2 (MTB)
⬆️ Antigen
⬆️ Hypersensitivity reaction:
✅Tissue necrosis – from enzymes of degenerating macrophages
✅No granuloma formation
✅ Necrosis – caseous material at the primary lesion
✍️After healing, the bacilli are not totally eradicated and will stay in granulomas for months or
years
✍️Overall, children account for most cases of miliary TB, but it is also a common form of
TB in HIV-infected individuals
✍️ Miliary TB:
seeding of many organs outside pulmonary tree
✅It is also known as tuberculosis spondylitis or skeletal TB of the spine
✅It is a grave form of tuberculosis caused by the invasion of M. tuberculosis into the
spinal vertebrae
Pott’s disease
💊Anti-TB drugs
Primary drugs:
RIPES
Rifampin (Rifampicin)
Isoniazid
Pyrazinamide
Ethambutol
Streptomycin
💉Anti-TB drugs
Secondary drugs:
✅ Injectable drugs: Amikacin, Capreomycin, Kanamycin
✅Fluoroquinolones: Ciprofloxacin, Ofloxacin, Levofloxacin, Moxifloxacin
How long is the TB treatment process?
(6 months) since slow grower…
✍️MULTIDRUG RESISTANT MYCOBACTERIUM TUBERCULOSIS (MDR-TB)
Happens when :
✅Happens if the patient is on multidrug therapy and fails to complete the course of medication
✅Acquired by spontaneous mutation as a result of inappropriate use of antimicrobial drugs and
lack of patient compliance
Primary MDR-TB is resistant to?
Rifampin and Isoniazid
Extensively drug-resistant tuberculosis (XDR-TB) is resistant to?
Resistance to Rifampin and Isoniazid + Fluoroquinolones + one of the injectable
drugs
What mycobacterium spp. is the TB vaccine derived from?
Mycobacterium bovis
It produces TB in cattle, dogs, cats, swine, parrots, and humans
Mycobacterium bovis
Mycobacterium bovis mode of transmission
✅ingestion of contaminated milk from infected cows
✅exposure to infected animals and their carcasses
resembles “water droplets” in Middlebrook media
Mycobacterium bovis
ID
Biochemical tests:
o (-) niacin and nitrate reduction🦠
o No growth in the presence of T2H
o (-) 68°C catalase test
Mycobacterium bovis
Associates with human cases of TB in tropical Africa
Mycobacterium africanum
✅Smooth strain of M. tuberculosis and grows more rapidly (6 days)
✅First human isolate was from a cervical lymph node and from AIDS patient with mesenteric
tuberculosis
✅Biochemical test: (+) niacin and reduced nitrate to nitrite
Mycobacterium canetti
✅ Isolated from TB patients in both immunocompetent and immunocompromised individuals
Mycobacterium microti
also known as MOTT?
NONTUBERCULOSIS MYCOBACTERIA (NTM)
✅Chronic pulmonary disease resembling TB is the usual clinical presentation
✅Found in soil and water
✅Opportunistic pathogens
NONTUBERCULOSIS MYCOBACTERIA (NTM) AKA MOTT
☀️💡Photochromogen color
Nonpigmented (dark)
Yellow pigment (light)
M. kansasii
M. asiaticum
M. marinum
M. simiae
🌃☀️Scotochromogen color
Yellow to orange pigment in dark,,
, but will intensify when exposed to constant light source .
M. gordonae
M. szulgai
M. scrofulaceum
M. flavescens
M. xenopi
✍️Non-photochromogen spp.
M. avium complex
M. ulcerans
M. terrae complex
M. gastri
M. haemophilum
✍️Rapid Growers spp. - Pigment variable
M. fortuitum
M. chelonae
M. smegmatis
M. phlei
M. abscecuss
M. mucogenicum
✍️Group 1-2-3 are slow growers!!!
Group 4- rapid growers - sila smegmatis etc.
Group I – Photochromogen
Group II – Scotochromogen
Group III – Non-photochromogen
- aka “Wood pigeon bacilli”
- rapid grower or slow grower?
- M. avium subsp. SILVATICUM
- slow grower
✅Causative agent of Johne’s disease (inflammatory bowel disease)
✅Also isolated from bowel mucosa of patients with Crohn’s disease
Mycobacterium subsp. paratuberculosis
Also known as the “Yellow bacilli”
🔬Microscopy: long rods with distinct cross-banding
———–“Shepherd’s crook”————–
Mycobacterium kansasii
(Photochromogenic colonies)
AKA “Buruli ulcer” - painless nodule under the skin after previous trauma that does not heal
Mycobacterium ulcerans
- Previously known as M. aquae, also known as:
——- “Tap water bacillus”——-
Mycobacterium gordonae
-CONTAMINATES TAP WATER
✅can be either non-photochromogen or scotochromogen ‼️
✅Recovered from hot and cold-water taps, especially water storage tanks of hospitals, and from
birds
✅First isolated from African toad
Mycobacterium xenopi
LEPROSY / HANSEN DISEASE causative agent
Mycobacterium leprae
✅cause of crippling of the hand
✅ERYTHEMA NODOSUM LEPROSUM
LEPROSY / HANSEN DISEASE
by: M. leprae
🦠Bacteria ID:
✅Aerobic, acid-fast rods
✅CANNOT be cultured in vitro. Can only be cultured in certain animals
:
-🐁Mouse footpad
- Armadillo
- 🙈Monkeys
Mycobacterium leprae
REMEMBER!
✍️Mycobacterium leprae
✅Leprosy
✅Hansen disease
✅Armadillos
✅Erythema nodusum leprosum
leprae
✍️Calcified granulomas are generally considered a sign of past or latent TB infection, as they indicate that the body has walled off the active infection and the ** disease is no longer active or contagious. **
(RANKE’S COMPLEX)
✍️Calcified granulomas are generally considered a sign of past or latent TB infection, as they indicate that the body has walled off the active infection and the disease is no longer active or contagious.
(RANKE’S COMPLEX)
in MTB why is Cord factor the mot important virulence factor?
✅inhibits neutrophil migration and damages mitochondria
✅may be responsible for release of tumor necrosis factor ➡️ “cachexia”
✍️Specimens for Mycobact
✅sputum,
✅gastric lavage,
✅urine
✅bronchoscopy specimens,
✅fecal specimens
✅body fluids:
(pleural, pericardial, peritoneal, synovial, CSF), blood, wound, skin lesion aspirates, or tissue
term used - removal of normal microbiota or other bacterial contaminants from sputum
specimen
Decontamination
The term that involves splitting of the sulfide bonds in mucin that may trap mycobacteria, liquefying mucus of sputum
Digestion
✍️* After decontamination, mycobacteria are concentrated by centrifugation
✍️* Over treatment with decontamination agents may result in fewer positive cultures
✍️* Failure to isolate mycobacteria from patient with signs and symptoms of disease may indicate
overtreatment of decontamination
—SPECIMEN COLLECTION AND HANDLING—-
The most common decontamination agent on sputum - Serves as both a decontaminant and digestant
- 2-4% NaOH
✍️* N-Acetyl-L-Cysteine and NaOH
-Both a decontaminant and a
digestant agent
-NALC is also known as
dithiothreitol – a digestion agent
stain more sensitive than carbol fuchsin
🔬(+) result: bright yellow-orange bacilli against a dark
background
Auramine-Rhodamine Flurochrome
✍️INTERPRETATION OF STAINING RESULTS:✍️
✅ View a minimum of 300 fields before a slide is called negative.
✅ AFB can be transferred from one slide to another via immersion oil - stained bacilli can float off the slide and can contribute to a false-positive of the next slide.
✅ If at least 2 of the first 3 sputum direct smears are positive, then 3 specimens are often sufficient to
confirm diagnosis.
✅ If none or only 1 of the first 3 sputum smear is positive, additional specimens are needed for culture confirmation.
AKA: Mantoux Test
✅It detects a patient’s cell-mediated immune response to the bacterial antigens in a type IV
hypersensitivity reaction
✅This test does not differentiate active disease from infection
✅A reactive (+) result indicates past environmental exposure to M. tuberculosis or a previous
tuberculosis vaccination
✅Presence of hard, dense, raised wheal
(induration) that is 10 mm or larger after 48 hours
TUBERCULIN SKIN TEST
-Uses Tuberculin purified protein derivative (PPD)
most commonly used biochemical test to identify MTB
Niacin Accumulation (Nicotinic acid) Test
-95% of M. tuberculosis isolates produce free niacin
✅(+) result: Yellow – indicates accumulation of free niacin
- Detects the production of nitroreductase, which converts nitrate to nitrite
Nitrate Reduction Test
(+) result: Red color forms
✅Positive: M. tuberculosis, M. kansasii, M. szulgai, M. fortuitum
Heat-stable catalase is a catalase that is
resistant to heat at ________? cooled
and reacted with hydrogen peroxide
✅ (+) result: column of bubbles with a height of
more than ⬆️45 mm
68°C for 20 minutes
Negative:
o M. tuberculosis complex
o M. gastri
o M. haemophilum
o M. marinum
Used to differentiate between the species of non-photochromogens and scotochromogens
Tween 80 Hydrolysis
✅(+) result: Pink color due to unbound neutral red (from
amber color to pink)
- It detects the ability of mycobacteria to convert ferric ammonium
citrate to an iron oxide
Useful in distinguishing M. chelonae from other rapid growing
NTM
Iron Uptake
✍️Growth on MacConkey Agar without Crystal Violet
*✅M. fortuitum-chelonae complex can grow on MacConkey agar without crystal viole
✅Most rapid test for identification of common mycobacterial species
Nucleic Acid Hybridization Test
✅For M. tuberculosis complex, M. avium complex, M. intracellulare, M. kansasii, M. gordonae
✅ Required inoculum: single colony (1 mm diameter)
- Designed to detect M. tuberculosis complex bacilli directly from the patient
specimens
Direct Nucleic Acid Amplification Test
BACTE ID
*✅ It invades peripheral nerve and skin cells, and becomes obligately intracellular parasite
*✅ Mostly found in Schwann cells that surround peripheral nerve axons and in mononuclear
phagocytes
*✅🔬Microscopy: rod shape exhibiting “cigar pocket/pocket fence” arrangement
Mycobacterium leprae
appears as “cigar pocket/pocket fence” arrangement
Mycobacterium leprae
✍️HANSEN’S DISEASE/LEPROSY
Transmission:
✅ inhalation
✅ with infected skin
✅ arthropod bite
✅ through breast milk
✅ vertical transmission
🐋
- 2 Forms of Leprosy?
- Tuberculoid Leprosy - localized
(+) Lepromin test - Lepromatous Leprosy - systemic
* (-) Lepromin test
