Tuesday, October 2, 2012

Non culturable Pathogenic Bacteria: Challenge to laboratory diagnosis of disease

Culture is one of the most widely used laboratory diagnostic tool.  Culture helps microbiologist for the identification and characterisation of the causative agents of the disease.  To perform antimicrobial susceptiblity test also, microbiologist have to grow the bacteria in the laboratory media (though now antimicrobial resistance can be assessed better by Molecular diagnostic tools).

Due to the specific nutritional requirements of bacteria, a single media can not support the growth of all be bacteria so there are various bacteriologic media to help for the growth of specific bacteria. But still there are some bacteria which can not be cultured (or grown) in the bacteriologic media available till date:
  1. T. pallidum has not yet been grown in bacteriologic media or in cell culture. (But non pathogenic treponemes can be cultured).  Diagnosis is made by Microscopy and serology
  2. M. leprae has not yet been grown in the laboratory either on artificial media or in cell culture. It can be grown in the mouse footpad or in the armadillo.
  3. Chlamydia trachomatis It can not be grown in artificial medium but most be grown in living cells.
    Bacteria that can be cultured: but rarely cultured in Standard Clinical Laboratory
  4. Coxiella burnetti (causative agent of Q Fever): Risk of Laboratory acquired infections is very high, cultivation of Coxiella burnetti must be done in a biosafety level 3 containment facility (facility not available in standard clinical laboratory).
  5. Rickettsia (they are the fastidious bacteria that are obligate, intracellular parasite), and causes Rickettsial pox, Rocky Mountain Spotted fever, Typhus fever: They can be cultured in embroyonated egg or tissue culture, the risk of laboratory acquired infection is extremely high, so culture rarerly done.

To be continued…..

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