Test 1: lecture 6: mycobacterium Flashcards
what stain is used for mycobacteria
Ziehl-neelsen staining
the outer membrane of mycobacteria contain ___ and ___
mycolic acid
lipo-arabino-mannan
what shape is mycobacteria
gram + bacilli
(acid fast +)
what three bacteria are acid fast +
mycobacterium
nocardia
rhodococcus
(all gram + rods)
what type of bacteria are non acid fast
corynebacterium
actinomyces
dermatophilus
trueperella
(gram + rods of the actinomycetia family, no spores)
list the gram + rods
mycobacteria are important causes of human and animal ___
tuberculosis disease
what kind of animals are highly susceptible to TB?
elephants
can transfer from human to elephant to human
mycobacteria course of disease in most healthy individuals is ___ as long as immune function is maintained
asymptomatic
the function of what in the host is crucial for containment of mycobacteria
CD4+ T cells, IFNg, macrophage microbicidal mechanisms
TB lesions form ___ that have central caseating necrosis
surrounded by ____ and T cells
granulomas
‘epithelioid’ macrophages
(caused by mycobacteria gram + rod, acid fast +)
Johne’s disease is caused by ___
Mycobacterium avium subsp. Paratuberculosis
Mycobacterium avium subsp. Paratuberculosis causes ___
johne’s disease in cattle
mycobacteria cause debulitating ___ in cattle
Debilitating enteritis in cattle –
acquired during first 6 months of life, clinical disease appears 2-8 years later. Organisms shed before onset of clinical symptoms
3 important disease of mycobacteria
1) Leprosy
2) Tuberculosis
3) Paratuberculosis (Johne’s disease→ cattle)
(gram + rods, acid fast +)
sunlight promotes the production of ___ by macrophages
Vit D → IFN gamma in macrophages
4 important species of mycobacteria
1) M. leprae - - - - - - - leprosy in humans.
2) M. tuberculosis - - - TB in humans.
3) M. bovis - - TB in cattle, other animals & humans.
4) M. avium:
* *subspecies avium** - - -TB in chickens, other birds, some animals & in
(immunocompromised) humans.
* *subspecies paratuberculosis** – paratuberculosis (Johne’s Disease) of ruminants; infection of humans is controversial
___ cause leprosy in humans
1) M. leprae - - - - - - - leprosy in humans.
(gram + rod, acid fast +)
___ cause TB in humans
Mycobacteria tuberculosis
___ cause TB in cattle, other animals and humans
mycobacteria bovis
___ cause TB in chickens
Mycobacteria avium subspecies avium
(gram + rod, acid fast +)
___ cause paratuberculosis in ruminants
Mycobacteria avium subspecies paratuberculosis
(Johne’s Disease)
(might cause Crohn’s disease in humans??)
what are the two important subspecies of Mycobacteria avium
- *subspecies avium -** - -TB in chickens, other birds, some animals & in
(immunocompromised) humans.
subspecies paratuberculosis – paratuberculosis (Johne’s Disease) of ruminants; infection of humans is controversial
Ziel-Neelsen method is used for ___
mycobacteria are gram + but their cell wall do not react well with decolorization are appear weird gram - looking
bacteria is dyed with carbolfuchsin, then steamed, then decolorized with acidified alcohol (95% EtOH- 3 % HCl), then counterstained and produce Red rod shaped bacteria
steps of acid fast stain
bacteria is dyed with carbolfuchsin, then steamed, then decolorized with acidified alcohol (95% EtOH- 3 % HCl), then counterstained and produce Red rod shaped bacteria
ziehl-nellsen
acid fast staining
(mycobacteria, nocardia, rhodococcus all acid fast +, gram + rods)
besides for acid fast stain what is another way to identify mycobacteria
auramine fluorescent stain
auramine and rhodamine are flurochromes
(non specific fluorescence can cause a problem in clinical specimens)
(mycobacteria, nocardia and rhodococcus are gram + rods, + acid fast)
auramine fluorescent stain used to stain for mycobacterium
(gram + rod, acid fast +)
___ help stabilize mycobacteria cell wall
lipoarabino mannan
also have fatty acid mycolic acid
___ give mycobacteria cell wall its hydrophobic character
mycolic acid → fatty acid
lipoarabino mannan
compare the make up of the cell wall of Gram +, gram - and mycobacteria
gram + → open faced sandwhich → thick peptidoglycan
gram - → LPS outer layer and thin peptidoglycan in a periplasmic space
mycobacteria → gram + rods, acid fast +→ thick outer membrane of mycolic acid and lipoarabino mannan, thin peptidoglycan
what are three tubercle bacilli
Mycobacteria tuberculosis
M. bovis
M avium (subspecies avium and subspecies paratuberculosis)
(mycobacteria, nocardia and rhodococcus are all acid fast +, rod shaped gram +)
properties of tubercle bacilli
non motile aerobes
no spores
straight or slightly curved rods
sometimes filamentous
multiply slowly (14-24 hrs)
takes > 3-4 weeks to grow in culture
tubercle bacilli such as ___ multiply every ___
M. tuberculosis, M. bovis and M avium
12-14 hrs (slow growing)
tubercle bacilli such as ___ take ___ to grow in culture
M. tuberculosis, M. bovis and M avium
> 3-4 weeks
tubercle bacilli are aerobes or anaerobes?
non motile aerobes
how to grow mycobacteria in culture
lowenstein- jensen agar
high lipids and contain egg products, glycerol, potato flour and salt
malachite green in used to inhibit the growth of other bacteria → mycobacteria very slow growing, need to kill off other bacteria to allow them to grow
lowenstein-jensen agar is used to grow
mycobacterium
very slow growing → malachite green added to kill off other bacteria
high in lipids, glycerol, salt and potato flour
mycobacteria can survive moderate ___
heat but will be killed by pasteurization
mycobacteria is resistant to ___
desiccation (drying)
most aqueous disinfectants→ acids and bases
___ is used to kill mycobacteria
phenol and alcohol
direct sunlight
2 common resistant TB strains
MDR - multi-drug resistant
XDR- extensively drug resistant
____is defined as resistance to isoniazid and rifampin, plus resistance to any fluoroquinolone and at least one of three injectable second-line anti-TB drugs
XDR TB
Packy of Oregon Zoo had ___
TB
got it from humans and could pass to other elephants and humans
3 routes of infection for TB
inhalation
ingestion
percutaneous
(TB caused by mycobacteria→ gram + rod, acid fast +)
ingestion of mycobacteria leads to lesions in the ___
intestinal tract, lymph nodes, liver, and spleen
(would happen a lot before milk pasteurization)
what route of infection of TB is rare
percutaneous → infection after skin inoculation cause lesions in the skin, skin draining lymph nodes
TB caused by mycobacteria (gram + rod, acid fast +)
miliary TB
rare
granulomas form in the lungs of immuncompromised cattle
caused by mycobacteria (gram + rods, acid fast +)
BCG
Bacillus Calmette Guerin (BCG) vaccine for TB
not used in animals because it can cause false positive TB skin tests
most effective for childhood tuberculous meningitis and miliary disease
are there vaccines for TB
not really
can use Bacillus Calmette Guerin (BCG) vaccine but causes false positive TB skin test and not very effective
immune response to M. Tb and M. bovis
bacteria infect macrophages and dendritic cells that activate CD4 Tcells to produce IFN gamma and TNF alpha which leads to increased macrophages and granuloma formation
how does skin test for TB work
delayed hypersensitivity response
inoculated with a PPD (purified protein derivative)
if previous exposure memory T cells will release IFN gamma and cause tissue swelling
will get response if had TB in past or if they had BCG vaccination
what kind of diagnostic test for mycobacteria TB
chest xray
acid fast staining and culture
PPD skin test
IFN gamma release assays → Elisa testing
QuantiFERON-TB Gold and T-SPOT.TB
IFN gamma release assays
testing for memory cells for antigens of M. bovis and M. avium that release INF gamma
will not cause false positive if previous BCG vaccination
how to control TB in food production
cull infected animals and monitor for lesions although most cattle show no lesions
(caused by mycobacteria → gram + rods, acid fast +)
why is it not recommended to treat TB in pets
requires multiple antibiotics over a long course
Isoniazid, rifampin, ethambutol, pyrazinamide.
can lead to resistance
what drugs are used to treat TB
Isoniazid, rifampin, ethambutol, pyrazinamide.
long treatment 6-12 months!
MAP
Mycobacterium avium subspecies paratuberculosis
Johne’s disease
(gram +, short thick rods, acid fast +)
bacteria produce mycobactin that allows bacteria to scavenge iron from their environment
parasitic pathogen
takes 6-12 weeks to grow in culture
how long does it take to grow Johne’s disease in culture
Mycobacterium avium subspecies paratuberculosis (MAP) (gram +, short fat rods, acid fast +)
6-12 weeks
what type of gram + rod are obligate parasitic pathogens?
Mycobacterium avium subspecies paratuberculosis (MAP)
Johne’s disease
produce mycobactin that steal iron from the host
resistance of MAP
same things as tubercle bacilli → moderate resistance to heat, resistance to drying, fair resistance to disinfectants such as acids and bases, killed by alcohol, sensitive to direct sunlight
but
can survive for 250 days in the environment, can’t replicate but just sits there waiting for a host
wasting
cachexia
Johne’s disease
caused by Mycobacterium avium subspecies paratuberculosis (MAP)
gram + short rods, acid fast +
chronic, debilitating enteritis in cattle, sheep, goats and other ruminants resulting in diarrhea, cachexia (wasting), and eventual death.
leads to decreased milk production
symptoms start 2 years after infection
around 22% of dairy and 8% of beef infected
transmitted by fecal/oral route, in utero and during milking
chronic, debilitating enteritis in cattle, sheep, goats and other ruminants resulting in diarrhea, cachexia (wasting), and eventual death.
Johne’s disease
caused by Mycobacterium avium subspecies paratuberculosis (MAP)
gram + short rods, acid fast +
pathogenesis of johne’s disease
caused by Mycobacterium avium subspecies paratuberculosis (MAP)
gram + short rods, acid fast +
eaten by macrophages in peyer’s patches and intestinal mucosa → resistant to being killed and will slowly replicate which cause inflammation and granuloma formation in the wall of the intestine
caused by Mycobacterium avium subspecies paratuberculosis (MAP)
johne’s disease
gram + short rods, acid fast +
3 ways to diagnose Johne’s disease
Fecal culture, 12-16 wks
– most sensitive & most reliable
Serum antibody tests
– less expensive, faster
– becomes more reliable as disease progresses
PCR
– fast, as sensitive as fecal culture but expensive.
is there a vaccine for Johne’s disease
yes but not really used
does not stop infection or shedding, more prevents calves from getting it
causes false positive tests
how to treat Johne’s disease
drugs not very effective- expensive don’t really work
cull infected
move babies away from adults
very hard to remove
caused by Mycobacterium avium subspecies paratuberculosis (MAP)
MAP infection common in humans with __disease.
Crohn’s
Mycobacterium avium subspecies paratuberculosis (MAP)
(gram + short thick rod, acid fast +)
