Myobacteria Flashcards
describe mycobacteria
- unicellular and branched rods
- G+ve
- complex cell wall (cont sugars, proteins and LOT OF LIPID)
how can mycobacteria be stained and identified?
Acid fast staining-Ziehl Neelson stain: -stain carbol fuchsin -destain acid alcohol -counterstain methylene blue mycobacteria= RED (everything else=blue)
what is found in cell walls of Mycobacteria?
mycolic acid (protective, waxy coat) outside peptidoglycan layer
what are the two groups of Mycobacteria?
which group is pathogenic?
1) fast growers (1-2 days on plates)
2) slow growers (several weeks)- PATHOGENIC group
M.bovis causes?
bovine TB
M.avium is what type of pathogen?
where is it found?
- opportunistic pathogen
- ub in env
M.paratuberculosis affects what?
ruminants
M.ulcerans affects who?
causes what?
humans
causes ulcers
M.leprae affects who?
humans
M.marinum affects who?
fish, frogs and humans
significance of TB
- global emergency
- 35000 deaths a week
- high incidence in HIV individuals
outcomes after TB exposure
1) EXPOSURE, NO INF
- TB cleared before it gets past INNATE immune defences
2) EXPOSURE, INF, NEVER DISEASE
- if immunocompetent, 90% DON’T get disease
3) EXPOSURE, INF, DISEASE, +/- DEATH
- asymptomatic latent period
how do you test for TB?
Heaf/Mantoux test- antigen is placed on skin, punch is used to punch it into skin
may form INFLAMMATORY response
how does TB exit the host?
by causing TB infection/disease
describe the pathogenesis of TB
- aerosol travels to alveoli of lungs
- M.tuberculosis engulfed by alveolar macrophages
- if activated due to an acquired immune response host clears bacteria or contains infection
- if unactivated (child or immunocompromised), bac survive and replicate in macrophages—> attracts more PMN & T cells—> damage tissue, form granulomatous tubercle
what can be used to diagnose TB?
1) X ray
2) microscopy of sputum looking for acid fast rods
3) culture sputum samples(media con egg or oleic acid or albumin)
4) PCR
what happens when the granuloma (tubercle) grows?
it eventually breaks into the airway of lung, is coughed up and O bacteria are released-
TRANSMISSION
how is the granuloma formation capable of stopping TB progressing?
may contain the infection and stop TB development BUT can also aid transmission (granuloma coughed up—>transmitted)
what HOST FACTORS determine how someone responds to TB infection?
- HIV status
- immunodeficiency
- genetic immunodeficiency
- substance abuse
- malnutrition
what BACTERIAL FACTORS determine how someone responds to TB infection?
- small differences in STRAIN VIRULENCE
TB symptoms?
- fever
- weight loss
- weakness
- PERSISTENT COUGH (due to inflammatory response)
where can TB spread (15% of cases)?
CNS, lymphatic system, genitourinary systems, bones etc
TB prevention?
BCG Vaccine
TB treatment?
MULTI DRUG AB treatment (~6 months)
4 main ABs are 1st line
how effective is the BGC vaccine?
efficacy varies by geographic location and population
- works well in children
- protects against leprosy
describe AB resistance for TB
resistance = inc common
some strains are resistant to ALL 4 FRONTLINE DRUGS called EXTENSIVELY DRUG RESISTANT TB
what causes resistance in TB?
- failure to take all medications
- failure to be provided w/ steady supply of medication
what causes leprosy?
M. leprae
how can we grow M.leprae?
cannot be cultivatable, but can be grwon in armadillos, squirrel ears & mouse footpads
what type of parasite is it?
intracellular, grows in macrophages and Schwann cells (—> nerve damage)
how is M.leprae transmitted?
- little known
- most who come into contact are NOT infected
- those w/ leprosy have high counts in nasal discharge
what % of infected individuals get the leprosy?
5%
what are the 2 clinical manifestations of leprosy?
1) TUBERCULOID
-few bacilli in tissue, mild disease, few skin lesions
Host response: strong immune response, low antibody, tuberculoid GRANULOMA forms to CONTAIN the infection
2) LEPROMATOUS
- severe, huge nos of bacilli in tissue, multiple lesions, skin nodules packed with bacteria. Nerve damage, loss of extremities, DEATH
Host response: poor immune response, high antibody, FOAM CELL GRANULOMA
how is leprosy prevented?
BCG vaccine
how is leprosy treated?
ABs (Dapsone), treatment may be for life
describe resistance to M.leprae
increasing O need multi drug therapy
