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Flashcards in Mycobacterium Deck (57):


aerobic, non spore forming, pleomorphic rods, variable pathogenic potential

mycelia acid is long chasing FA attached to peptodiglocan, similar to gram + organisms

Lipoarabinomannan (LAM) similar to LPS, binds to TLR-2, high lips content in membrane so the waxy lipid coat makes them hydrophobic and sturdy

Acid fast to stain!

They look like nagatively stained rods on cytology


slow growing

produce tubercles (M. tuberculosis) or not (M. avium)
-highly pathogenis
facultative, obligate intracellular
- M. Boris spread to humans once cattle milk was ingested


acid fast

ziehl-nielson stain (hot acid fast), or Fite-Farco stain (leproid bacteria use sulphuric acid instead of alcohol to decolorize)

heat fix, cover its carbofuschin primary stain x 5 min over flame, rinse, add decolonizing agent (acid alcohol), rinse, counter stain with methylene blue

mycobacteria hold on to carbofuschin stain and look red


culture of mycobacteria

-lowenstein-jensen (uses egg to solids)
-middlebrook media (solid or liquid agar)
-malachite green

8 weeks of incubation required

5% sheep blood, Lowenstein sense, or ogawa egg yolk to grow rapidly growing strains


culture of mycobacteria

-lowenstein-jensen (uses egg to solids)
-middlebrook media (solid or liquid agar) - liquid produces radioactive C02 within 2 weeks
-malachite green

8 weeks of incubation required

5% sheep blood, Lowenstein sense, or ogawa egg yolk to grow rapidly growing strains

innculate immediately

disinfect around the outside of the transport media


M. tuberculosis epidemology

affected 1/3 of world ppopulations
- humans are natural host, spread from sputum
-anthropozoonosis is transmission from human to animals
-banded mongoose and meerkats are getting it from humans, whoa re the only reservoir host


risk factors for M. TB

being in populated areas, close contact with infected people, fed unprocessed meat or milk in areas of endemic disease; dogs have higher incidence, cats seem to be resistant


M. bovis

bovine TB; worldwide distribution
milk is ideal medium - through GIT, not aerosolized droplet; doesn't persist in environment
- reservoir hosts maintain disease


M. bovis

bovine TB; worldwide distribution
milk is ideal medium - through GIT, not aerosolized droplet; doesn't persist in environment
- reservoir hosts maintain disease
-cats are more susceptible as cats eat raw meat and are around dairy cattle and milk


wildlife reervoirs

US: white tailed deer, U: badgers; NZ: reservoir host (brush tail possums), amplifier host, dead end host


M microti

3rd part of TB complex; in Great Britain rom rural avid hunting cats


three routes of exposure?



primary complex is what?

granuloma formation at initial site, spread to Las. i.e. in lungs then spreads to hilar LNs


Incomplete complex is what?

no primary lesion with LN localization


pathogenesis of M. TB

immune response:
-macrophages and cytotoxic T cells eliminate bacteria --> healing and fibrosis; respiratory burst then release of proinflamm cytokines, triggers IFN-gamma production.
---> healing fibrosis

-defective cell mediated immunity --> persistent focal or disseminated disease...


M. TB clinical features

resulting from trauma
nodules o head, neck, limbs with foul odor

respiratory involvement caused by M. Tb. bronchooneumoia

GI involement mot often from M. Boris (tonsiar enlargement, weight loss, anemia, abdominal; effusion,weight loss

disseminated: plural or pericardial effusions, abdominal masses, choroiditis and retinal detachment in cats


Acid fast bacteria is __ in M. tuberculosis and __ in M. microti

extracellular, intracellular


guinea pigs are sensitive/resistant

sensitive - death in 6-8 wks


PPD stands for what and what does it do?

purified protein derivative; delayed type hypersensitivity, bacilli calmette guerin (BCG) vaccine is attenuated M. Bovis in both humans and dogs to induce resistance

this vax can be used for testing, but if previously vaccinated, may be falsely postivie


tuberculin testing

concave pinnae or intradermal, read at 48-72 hours.
positive is raised, necrotic ulcer at 10-14 days
if erythema resolves by 72 hours, it's negative. can see ulcer at 18-21 days

caudal ofold tuberculin test, followed by comparative cervial test, or interferon hammer test to differentiate between M. bovis (these cattle are culled) and M. avium (not culled)


serologic testing

ELISA can test body fluids

animal inoculation with intraperitonieal suspension from suspected cases and if they die, you know it's M. TB

PCR can be positive without gross lesions but risk of false negatives, false pasties if rhodococcus species is there (environmental contaminant)

used for invonclusive skin test, risk for vaccine interference though.

antigen-specific interferon gamma production measures lymphocyte response to m. Bovis and avium species


M. tuberculosis complex management

get treatment started! multi drug therapy; risk of spread --> euthanasia

humans treated based on active disease or exposure - prophylactic tx for 6-9 mos

Dogs: rifampin, isoniazid, streptomycin
Cat: surgical excision, rifampin, quinolone, clarithro or azithromycin

rifampin alone can lead to rapidly developing resistance


t/f: M. microti has high risk of zoonosis

F ; single cutaneous lesions have best prognosis; take chest radiographs and look for disseminated disease


t/f: M. TB is reportable



m. bovis in cats

not major risk to humans


M. microti

usually from rodents


M. avium complex

opportunistic, does not produce true tubercles, slow growing, can sometimes disseminate


three M. avium subspecies

1. M. avium subs. paratuberculosis cattle (Johne's)
2. M. avium subs. hominisuis - swine humans
3. M. avium subs.


M. avium complex

Abyssinian and somali cats are at risk for disseminated disease
most likelyyo to cause bacteremia


MAC etiology

-acidic pH 5.0-5.5, organic matter, swamps, coasts, bird feces

-transmission via infected meat
-persistent in water, present on biofilms, recirculating water systems in hospitals, not killed by chlorine


prevalence of MAC

uncommon in dogs and cats, poultry and swine most susceptible, deep granulomatous indistinguishable from tubercle bacilli


m. avium paraTB

high prevalence in Johne's dz, dogs with GI disease, feral cats on farms

ingest via environment, food, viscera

dissemination can occur without a primary site

binds TLR2, increases IL10, hides from immune system


what cat breeds are at risk for disseminated mycobacterial disease?

Abyssinian and somali cats


t/f: glucocorticoids can be used in systemically ill patients with MAC



MAC prevention:

do not feed raw meat or unpasteurized milk, vaccines (live BCG, recombinant, false-positive skin test is a risk )


How to disinfect?

glutaraldehyde 2%, ethyl and isopropyl alcohol, no tap water as final rinse! manually pre clean with neutral detergent


feline leprosy: 3 forms

granulomatous, nodular, cutaneous or SQ mucobacteiral infection'

-found in temperate coastal areas

-features: related to M. avium; esp. young adult cats, traumatic inoculation and results in painless SQ mass, can rapidly grow and spread to regional LN. usually stays localized

3 forms:
1. young cats - M. leparaemurium (rat)
2. older cat (M. visible -USA); aka Mycobacterium lepraefelis
3. Novel strain (M. sp. strain tarwin in victoria)

ddx: TB, opportunistic mycobacteria, foreign body, mycotic infections, neoplasia


candidates mycobacterium lepraefelis

related to M/ visible, develops generalized nodular disease, slow to develop over month and years


candidatus mycobacterium tarwinense

victoria, australia - head, ocular lesions


tissue culture is helpful in which type of mycobacterium?

slow growing...negative for fastidious

-ogawa's egg yolk or M lepraemurium

difficult to grow


histopath reoponses

tuberculoid response - caseous necrosis, fewer organisms

lepromatous leproy
multibacillary, sheets of foamy macrophages, no necrosis


prognosis of feline leprosy:

lepraemurium - good
tarwinense - good
lepraefelis - poor


humans infected with ___

m. leprae


risk of death is high in which type of feline leprosy?

mycobacterium lepraefelis


canine leproid granulomas

healthy dogs, confined to head - inset mechanical vector?

-readily seen on cytology 9negative stated bacilli on diff quick or on ziehl-nielson) but causative agent hasn't been cultured
-2-5 cm in diameter nd ulcerate, no systemic illness, can have 2ndary staph pseudintermedius
-esp. boxers

-histo: pyogranulomatous dermatiiss, multinucleate histolytic giant cells
-no public health risk
-spontaneous resolution in 1-3 months
-rifampin and clarithromycin or azithroycine or doxycycline
-treat until lesions are resolved


rapidly growing opportunistic

ubiquitous, free living, harmless, in soil, tap water, growth within 7 days

causes mycobacterial panniclitis when barrier is impaired


rapidly growing opportunistic

US: fortuitous
Australia smegmatis - find it "down under"


mycobacterial panniuclitis = Rapidly growing mycobacteria

requires triglycerides for growth; protection from immune response;

-trauma not always reported
-can look like catifhgt abscesses, plaques or nodules at site of injury
-skin thins, then punctate fistulae and watery exudate from th ulcerated areas
- don't always see draining tracts in dogs, persist for months

commonly on inguinal fat pad, spreads throughout trunk and subcutis; solitary nodule usually but immune suppressed individuals have worse manifestation

Prognosis: good, start empiric antibiotics - doxycycline and/or quinolone, clarithromycin

NO CLAVAMOX - even if sensitive in vitro, don't pick it with these guys!

use highest dose possble

FNA of closed SQ lesions - disinfect with 70% alcohol so you don't grow the contaminant.

fite faraco stain is preferred, as they are not as acid fast as other species

culture on 5% sheep blood agar or lowensein Jensen agar, 2-3 days after inoculation but can't take longer


which strains cause pneumonia?

M fortuitous, or M. chelonae; bath water in cats, aspiration


m. tuberculosis, bovis and microti

slo growtin


Canine leproid granuloma species



rapidly growing mycobacteria

M. fortuitous (US), smegmatis (Aus)


botryomycosis is what?

staph bacteria causing a nodular lesion


where to collect sample from cytology and culture?

disinfect surface and FNA from the purple dimple! want to find a micro abscess in it. can use ultrasound to find a Lucent area. be far from draining tract.


so, you treat a cat with it in the fat pad...with pradofloxacin, erythromycin - and now you're gonna excise it. what's your protocol maximize complete resolution and minimize leaving behind any contaminated tissue?

en bloc resection of fat pad and skin, change surgical pack and gloves, and then close it

treat it like cancer.

treat with IV ahminoglycosides, which kill mycobacterium, but we don't use it because of the length of time needed to treat. preload with IVFluids and give highest dose of gentamicin and amikacin prep, periop, post op (for 24 hours). or use laser surgery

microaerophyllic environments so hyperbaric O2 facilitate aminoglycosides and FQs


RM treats dogs with:

clarithromycin, fluroquinolones, but inconsistent response


hard ones to see on histo grow rapidly, but those you can see, you can't grow