Mycobacterium Tuberculosis Lab14

Mycobacterium tuberculosis

Specimen collection tubercle bacilli are not always found in large numbers nor are they found even in obvious disease Therefore mulyiple specimens have to be collected wherever possible. 1-sputum morning samples /3 separate samples taken on 3 days is recommended (thick green /yellow with blood).

2-gastric washing (children) 3-urine morning sample for 3 days ore 24hr collection 4-pleural fluid 5- tissues lymphonodes –endometrial scrapings 6-C.S.F

Processing of specimens A) liquefies(4% NaoH) B) decontamination C) concentration

TB-staining (ZN-stain) method 1-flood the smear with carbol fuchsin for 5-10 min 2- wash 3-decolorurise by acid alchol(3% acid) 4-wash 5-flood with counter stain (MB or Mgreen) for 1 min mb= methylene blue /m-g = malachite green) 6-wash 7-dry and examine (*100 lense) (

Result acid fast organisms red / bright red or pink non AF (blue or green)

(af = acid fast )

Culture 1-Lowenstein Jensen (LJ media) cultures are incubated at 37C for up to 8 weeks 2-animal inculation (guinea pigs) 3-molecular(PCR)

Nitrate Substrate Broth AFB AFB = asid fast baselli

+ve

-ve