European Society of Mycobacteriology - Instituto Nacional de Saúde ...

PP-98
PEA PRODUCTION BY MYCOBACTERIA AND ITS
APPLICATION IN A RAPID DRUG SUSCEPTIBILITY TEST.
McNerney, Ruth 1 , Turner, Claire 2 , Mallard, Kim 1 , O’Sullivan, Denise 1
1 - London School of Hygiene & Tropical Medicine
2 - Cranfield University
Metabolites produced during bacterial growth may be used to monitor the impact of drugs on bacteria. We have investigated
volatile organic compounds emitted by mycobacteria growing on Lowenstein Jensen (LJ). Mass spectrometry
determined one of the major volatile compounds from M. bovis BCG to be phenylethyl alcohol (PEA), a bacteriostatic
compound that is a reversible inhibitor of DNA synthesis. PEA production was also observed in mycobacteria other than
tuberculosis (MOTT). That such a compound is produced in quantity by mycobacteria growing on LJ is surprising and may
explain the limited growth of mycobacteria on this media. PEA is only produced during bacterial growth and monitoring
production during exposure may provide a means of determining susceptibility to antimicrobial compounds. To test this
hypothesis, bacteria were placed on LJ slopes containing drug and incubated at 37C. Headspace vapors from the culture
tubes were analysed using the zNose, an ultra-rapid capillary gas chromatograph coupled to a SAW detector. The test
required no sample preparation and each slope was tested in less than 2 minutes. To minimize the risk of creating infected
aerosols culture tube caps incorporated a PTFE/silicone septum enabling air to be drawn from the tube without removing
the cap. Samples collected were heat sterilized during testing. Headspace samples from drug containing slopes were
compared to control slopes without drug. The incubation time required for differentiation between positive and negative
samples or ‘growth’ and ‘no growth’ depended on the size of the inoculum and the species of mycobacteria and ranged
from hours to a few days. MOTT could be differentiated from M. tuberculosis complex bacilli by continued production of
PEA in the presence of 500ug/ml para-nitrobenozic acid. We conclude that detection of volatile metabolites emitted by
mycobacteria growing on Lowenstein Jensen offers a simple, rapid alternative to assess their drug susceptibility.
170 ESM 2009