Exploring Tuberculosis' Resistance to Disinfection

Fischell Department of Bioengineering professor and chair William Bentley (joint, University of Maryland Biotechnology Institute) has recently published research in Applied Microbiology & Biotechnology discussing the response of tuberculosis to disinfection with bleach. The article, titled "Global Transcriptome Analysis of the Mycobacterium bovis BCG Response to Sodium Hypochlorite," is a collaboration with Dr. Freshteh Toghrol (Microarray Research Laboratory, U.S. Environmental Protection Agency), Dr. Hyeung-Jin Jang (Department of Biochemistry, Kyung Hee University, Seoul) and Dr. Chantal Nde (Center for Biosystems Research, University of Maryland Biotechnology Institute).

Tuberculosis is a common and often deadly infectious disease caused by mycobacteria (gram positive bacteria), mainly Mycobacterium tuberculosis, and infrequently by other subspecies of the M. tuberculosis complex, such as M. bovis. M. bovis is the causative agent of tuberculosis in cattle, but it can also jump the species barrier to infect humans. Sodium hypochlorite (bleach) is routinely used in hospitals and health care facilities for surface sterilization to prevent the spread of tuberculosis; however, how exactly bleach acts on M. bovis and how the organism develops a resistance to it have not been explained.

In the study, Bentley and his colleagues performed a global toxicogenomic analysis (one which examines an organism's genetic response to toxins) of the M. bovis response to exposure to sodium hypochlorite after 10 and 20 minutes. M. bovis growth was monitored by measuring the quantity of ATP (energy used for cellular functions) it produced over a short exposure time (10-60 minutes).

The results revealed significant regulation of oxidative stress response genes of M. bovis, such as oxidoreductase (an enzyme that catalyzes the transfer of electrons from one molecule to another), peroxidase (an enzyme that catalyzes a reaction to reduce toxicity), heat shock proteins, lipid transport, and metabolism genes. The group interpreted this response as a potentially more lethal interplay between fatty acid metabolism, sulfur metabolism, and oxidative stress. This study shows that the treatment of M. bovis with bleach slows the biosynthesis of outer cell wall mycolic acids, which play a role in tuberculosis's increased resistance to chemical damage and dehydration, and also induces oxidative damage.

This article was adapted from the original published by the University of Maryland Biotechnology Institute.

Published December 8, 2009