Humic and fulvic acids stimulate the growth of Mycobacterium avium

Abstract

Mycobacterium avium, an environmental, opportunistic pathogenic mycobacterium, has been isolated frequently and in high numbers from waters in Finland and from acid, brown water swamps of the southeastern coastal USA. M. avium has also been recovered in high numbers from Finnish drinking water and frequently isolated from Finnish AIDS patients. Boreal forests and brown water swamps are similar in that they are rich in humic and fulvic acids and of low pH and dissolved oxygen. Growth of representative isolates of M. avium in natural water was stimulated markedly by the addition of humic and fulvic acids. Further, the M. avium isolates grew at pH levels as low at 4.0 and at oxygen levels equal to 4% of atmospheric levels. The high numbers of M. avium in boreal waters and brown water swamps are likely due to their ability to proliferate in those humic- and fulvic-rich, acidic, micro-aerobic environments.

Characterization of biofilm formation by clinical isolates of Mycobacterium avium

“…Humic acid, however, was associated with less biofilm formation. The differences between our results and those of Kirschner et al (1992) might result from the strains used or the contents of the medium. It is possible that, because humic acid chelates cations, including Ca 2þ and Mg 2þ , it decreased the number of divalent cations available for efficient biofilm formation.…”

“…Since M. avium has been shown to establish biofilms in the water systems of urban areas, as well as on the walls of public saunas, one wonders whether those conditions linked with biofilms in vitro are present in the environments in which M. avium biofilms have been identified. Of note is the fact that increased amounts of zinc have been found in urban water systems (Kirschner et al, 1992). In addition, we believe that other sources of carbon besides those tested can be associated with M. avium biofilm formation.…”

“…For example, Pseudomonas aeruginosa uses organic acids as a source of carbon to form biofilm (O'Toole et al, 2000). In addition, Kirschner et al (1992) showed that M. avium grows better in water rich in zinc and humic acid. Our work demonstrates that M. avium establishes more stable biofilms in the presence of Ca 2þ , Mg 2þ and Zn 2þ , but not Fe 2þ .…”

Survival of Environmental Mycobacteria in Acanthamoeba polyphaga

“…Mycobacterium mucogenicum, Mycobacterium kansasii, M. gordonae, Mycobacterium flavescens, Mycobacterium aurum, Mycobacterium fortuitum, Mycobacterium peregrinum, and Mycobacterium chelonae have been isolated from public potable water (17,47,76). In water, M. avium and Mycobacterium intracellulare can survive, even under low oxygen tension (13,41). Furthermore, M. intracellulare can remain viable for a year in deionized sterile water (6).…”

High incidence of Mycobacterium avium subspecies hominissuis infection in a zoo population of bongo antelopes (Tragelaphus eurycerus)

“…10 Both bark mulch and peat are materials with low pH (5.0-3.5), which suppresses the growth of the majority of bacteria but represents ideal conditions for mycobacteria. 4,8 Although the possibility of the bark mulch being the source of infection has been considered, there is no convincing evidence to support such a causal relationship. The MIRU-VNTR analysis of Mah isolates found in storage bark mulch revealed genotypes that differed in the number of tandem repeats in 1 or more loci from the predominant genotype detected in the bongo antelopes and environment.…”