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

GL-5
SURROUNDED BY MYCOBACTERIA
Joseph O. Falkinham, III
Department of Biological Sciences
Virginia Tech
Blacksburg, Virginia 24061-0406
Phone 1-540-231-5931
FAX 1-540-231-9307
E-mail jofiii@vt.edu
Humans, animals, and plants are surrounded by mycobacteria. The environmental opportunistic mycobacteria (also called
nontuberculous or atypical mycobacteria) include over 100 species; many of which cause disease. Infections include cervical
lymphadenitis in children and pulmonary disease and skin infections in adults. Evidence that the environment was
the source of human disease was gained from the identity of DNA fingerprints of mycobacterial isolates from patients
and either their household water or potting soils. Recently, a number of reports have documented a dramatic increase
in pulmonary disease caused by these mycobacteria amongst elderly and slender men and women who lack all of the
classic predisposing risk factors (e.g., smoking, exposure to dusts). Although slowly growing with generation times of
one-half to one day, the environmental opportunistic mycobacteria survive, grow, and persist in a number of habitats
that are shared with humans and animals. The environmental opportunistic mycobacteria are oligotrophs; able to grow
in water containing greater than 50 µg AOC/L. Survival and persistence in the environment is due, in part, to the thick,
impermeable, hydrophobic, lipid-rich envelope of mycobacterial cells. Although the hydrophobic wall reduces the rate of
transfer or hydrophilic nutrients, it promotes attachment to surfaces where mycobacteria form biofilms. Hydrophobicity
also contributes to disinfectant- (e.g., chlorine and biocides) and antibiotic-resistance. For example, mycobacteria entering
a water treatment system on particulates survive disinfection and grow during travel in the distribution system in the
absence of competitors. Hydrophobicity also promotes the aerosolization of mycobacteria from water to air in environments
such as showers and hot tubs in the home and occupations where aerosols are generated.
30 ESM 2009