Mycobacteria

Question 1

general characteristics of MB

Answer 1

acid fast bacilli
poor stain, pleiomorphic, AF positive
obligate aerobe 
slow growing
complex cell wall
   outer layer of PPD, cord factor

Question 2

growth requires?

Answer 2

NH3
glycerol for carbon
Fe++
CO2 and fatty acids inc growth

Question 3

MB susceptible to? tolerant to?

Answer 3

susc. to heat and resistant to freezing

Question 4

what are the natural habitates of obligate pathogens, free saphrocytes, and transient commensial?

Answer 4

OP- humans and animals

FS- water and enviro

TC - WNL flora may or may not cz dz

Question 5

photochromogenic

Answer 5

slow grow, orange with UV

Question 6

scotochromogenic

Answer 6

slow grow, pigments in the dark

Question 7

nonchromogenic

Answer 7

no pigment , slow

Question 8

rapid growers

Answer 8

less than 7 d

Question 9

what is special about the relatedness of mycobacterium?

Answer 9

present identically but not all TB. serious DNA homology

Question 10

only virulence factor of MB?

Answer 10

fac intracellular parasite

NON- MOTILE
NO CAPSULE
NO PILI
NO TOXINS (except ulcer)

Question 11

pathogenesis of TB

Answer 11

contact with alveolar macrophages. organism multiplies in phagosomes and their maturation is inhibited. infected macrophage attract naive immune cells. forms a cavity granuloma.

carry infected macroph to lymph nodes. can go through the blood to anywhere while still asymptomatic

anerobic caseous center kills macrophages and they heal and leave fibrous calcified regions = see on XR

dormant pathogen in caseous tissue left behind. remain dormant

Question 12

when do you develop PPD positive?

Answer 12

when you start adaptive response 3-8 weeks

Question 13

when will TB recur?

Answer 13

when immunized wanes and it replicates and escapes from granuloma. disseminates through lungs or distant tissues via lymphatics

also TB less likely to activate in the young - but will int he old

Question 14

problems with PPD

Answer 14

nonspecific. lots of cross reactivity. false positives. also with vax.

false neg if immunocomp or taking steroids etc

Question 15

invirto TB testing

Answer 15

not affected by vax. correlates well with TB

uses TB peptides to see how much INF gamma secreted.

detects latent and active

a postive test is when you have a reactive immune system and you have latent or active tb

a neg is non reactive and you don’t have it

Question 16

mycobacterium kansasii

Answer 16

slow photochromogenic
not P2P
in tap water
#2 risk to have non tuberculin pulm dz
inc risk in smokers and inc age

Question 17

MAC

Answer 17

slow, nonchrom
water, soil, plants
low pathogenicity
***must have previous lung dz to have***
elderly women get it if don't smoke - nodular bronchi or Windemeres
No P2P
inc risk with aids

Question 18

M. fortium/cheloie/abcessus

Answer 18

rapid growers. 
****SOFT TISSUE INFECTION AFTER TRAUMA*** must have a first event
other things are rare
nosocomial infections
resistant to abx

Question 19

M. leprae

Answer 19

obligate intracell parasite 
cell wall has complex glycoproteins that are unresponsive to lymph and macrophages
capsule has PGL1 for survival
slow grow
hosts- humans and armadillos
P2P via aerosols (skin unlikely)
mucous membranes
long incubation period

Question 20

stages of leprosy

Answer 20

1. tuberculoid form: not infectious, no AFB on skin, L skin test POSTIVE
2. borderline: balance between host and parasite
3. Lipromatous form: VERY INFECTIOUS, increased AFB with vacuolated macrophages; FOAM CELLS; AFB in peripheral blood, and ** NEGATIVE SKIN TEST = IMMUNOLOGICAL ANERGY*(**