Centenary of the UCT Faculty of Health Sciences
The effect of physiological concentrations of bile acids on in vitro growth of Mycobacterium tuberculosis
Objectives. We examined the effect of physiological concentrations of bile acids on the in vitro growth of Mycobacterium tuberculosis (MTB).
Methods. The 4 major bile acids, lithocolic acid, cholic acid, deoxycholic acid and chenodeoxycholic acid, were added to individual Lowenstein-Jensen (LJ) culture media at physiological concentrations. A combined LJ medium was also prepared using all 4 bile acids. These were double-diluted 4 times by the addition of LJ media. Each culture medium was inoculated with the H37Rv strain of MTB and incubated at 37°C for 8 weeks. MTB growth was measured at 2 and 8 weeks in a semiquantitative fashion using cut-offs of >5, >10, >20, >100 colony-forming units.
Results. All lithocolic acid cultures showed uninhibited TB growth at 2 and 8 weeks. Chenodeoxycholic acid, deoxycholic acid and cholic acid alone, and in combination, showed concentration-dependent inhibition of MTB growth at 2 and 8 weeks. Four cultures were lost to contamination.
Conclusions. Certain bile acids alone and in combination, at physiological concentrations, inhibit the growth of MTB in vitro. This might explain why intestinal TB occurs in the ileocaecum in the majority of cases and why gallbladder TB is very rare.
David Epstein, Division of Gastroenterology, Department of Medicine, University of Cape Town and Groote Schuur Hospital, Cape Town
Kiki Mistry, University College Medical School, London, UK
Andrew Whitelaw, National Health Laboratory Service, Groote Schuur Hospital and Division of Medical Microbiology, University of Cape Town
Gill Watermeyer, Division of Gastroenterology, Department of Medicine, University of Cape Town and Groote Schuur Hospital, Cape Town
Keith Pettengell, Parklands Hospital, Durban
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Date published: 2012-05-23
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