Centenary of the UCT Faculty of Health Sciences

The effect of physiological concentrations of bile acids on in vitro growth of Mycobacterium tuberculosis

David Epstein, Kiki Mistry, Andrew Whitelaw, Gill Watermeyer, Keith Pettengell

Abstract


Background. Intestinal tuberculosis occurs mainly in the terminal ileum and caecum, where the concentration of bile acids is lowest, and rarely in the upper digestive tract.
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.

Authors' affiliations

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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Keywords

tuberculosis, bile acids, bile salts

Cite this article

South African Medical Journal 2012;102(6):522-524.

Article History

Date submitted: 2012-02-22
Date published: 2012-05-23

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