<prompt> Radio mi metric BACTEC detect growth of M tuberculosis in how much time -1 week2-3 week4-8 week10 weeks  <response>: Ans. is b1 i.e., 2-3 weeks Laboratory diagnosis of T.B. T.B. Specimens Decontamination and concentration of specimens Smear Culture Nucleic acid amplification Immunodiagnosis o Sputum o Urine o Pleural fluid o CSF o Joint fluid o As sputum and other specimens frequently contain many bacteria fungi that would rapidly overgrow mycobacteria on culture, they should be destroyed o Methods y Petroffs method M.C. y Flotation method y Autoclave method y Treatment with antiformin, Na2CO3 or hypochlorite y Detergents like tergitol o Ziehl-Neelsen staining o Fluorescence microscopy using auramine-rhodamine stain more sensitive rapid Solid medium o L.J. medium 4-8 wk for growth Liquid media o BACTEC-460 Radiomimetic growth detection Within 2-3 wks. o PCR o Ligase chain reaction o R.N.A. specific PCR o Not very useful o Enzyme immune assay for detection of antibody to mycobacterial lipoarabinomannan o Definitive diagnosis depends on isolation and identification of M. tuberculosis from a diagnostic specimen. Remember y Sputum is best collected in the morning before any meal. y Sputum sampling on three days increases the chances of detection. y If sputum is not produced, bronchial washing, brushing or biopsies and early morning gastric aspirate may be examined. y At least 10000 HP bacilli should be present per ml of sputum for the demonstration in a direct smear. y Culture can detect 10-100 bacilli per ml. o For culture o For microscopy - - 10-100 bacilli per ml. 10000 104 bacilli perml. 