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Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Poster Abstracts
82
2-POS
Board 2
Rapid Identification of Mycobacterium Tuberculosis Bacilli from Clinical Samples Using
Maldi-Tof Mass Spectrometry
Mousumi Banerjee
, Nelson D. Soares, Jonathan Blackburn.
University of Cape Town, Cape Town, Western Cape, South Africa.
Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI- TOF MS)
has become a regular diagnostic tool in clinical microbiology to identify bacterial species
(Biotyping) along with conventional phenotyping and gene sequencing. However, the limitation
in sensitivity (105-106 bacteria /
l) and time consuming culture based amplification makes this
method expensive and sometimes complicated particularly, for the slow growing bacteria like M.
tuberculosis. In the past 6 months, I have been working on development of a rapid, highly
sensitive and comparatively less expensive method to identify M. tuberculosis bacilli in clinical
isolates using commercial MALDI-TOF instrument. In this method we have identified key
surface lipids and the membrane protein markers from limited number of bacilli after extracting
them with organic solvent; this MALDI data suggests the set of identified lipids is sufficient to
discriminate M.bovis BCG from M.smegmatis bacilli although further work is required to
explore this differentiation in more quantitative detail. The key lipids were then fragmented by
MS-MS and searched against an ‘in-house’ generated database. The identified protein markers
are now being confirmed by ‘state-of –art’ LC-MS/MS, with resultant peptide mass spectra being
matched against a universal database for identification of the parent proteins. MALDI-TOF
signal enhancement was achieved by decreasing the noise level by changing laser diameter, laser
power and number of laser shots. So far we have been successful in identifying as low as an
estimated 10 bacilli, which is encouraging for the future identification of bacteria in aerosolised
samples.