Environmental factors affecting the occurrence of mycobacteria in brook sediments

Abstract

E. IIVANAINEN, P.J. MARTIKAINEN, P. VÄ Ä NÄ NE N A N D M .-L . K AT I LA . 1999. The occurrence of mycobacteria was studied in aerobic brook sediments from 39 drainage areas in Finland. The culturable counts of mycobacteria were related to climatic conditions, characteristics of the drainage area, chemical characteristics of the sediment and water, culturable counts of other heterotrophic bacteria, and microbial respiration rate in the sediment. The counts of mycobacteria varied from 1·1 × 10 2 to 1·5 × 10 4 cfu g −1 dry weight of sediment. They correlated positively with the proportion of the drainage area consisting of peatland, total content of C, content of Pb, microbial respiration rate in the sediment, and chemical oxygen demand of the water. The correlations of the mycobacterial counts with pH of sediment and alkalinity of water were negative. The results of the present sediment study and of the forest soil study published earlier strongly suggest that an increase in acidity increases the counts of mycobacteria and decreases the counts and activity of other heterotrophic bacteria. Mycobacterial counts were more than 100 times higher (per dry weight) in forest soils with pH 3·5-4·3 than in sediments with pH 4·5-6·3.

Acid Resistance inMycobacterium tuberculosis

“…In general, the fast-growing, saprophytic mycobacteria grow over a wider pH range than the pathogenic, slow-growing mycobacteria (16,69). This may reflect that the environments in which saprophytic mycobacteria reside, such as soil and water, are often acidic (43). Remarkably, mycobacterial species were found greatly enriched in extremely acidic volcanic rock at pH 1 (100).…”

Does Neutralization of Gastric Aspirates from Children with Suspected Intrathoracic Tuberculosis Affect Mycobacterial Yields on MGIT Culture?

“…This pH helps mycobacteria to survive inside the phagocytic vacuole of host macrophages, where the intraphagosomal pH is mildly acidic, i.e., pH 6.1 to 6.5. Saprophytic bacteria grow in soil and aquatic habitats and can withstand very acidic conditions (pH 3.5 to 4.3) (17,18) owing to their cell walls, which are rigid. Nevertheless, the strong acidic pH of gastric aspirates (usually between 1.5 and 3.5) might contain the overgrowth of most nonpathogenic bacteria, fungi, and parasites, but mycobacteria can survive in this hostile environment.…”

Characterization of Mycobacterium bohemicum Isolated from Human, Veterinary, and Environmental Sources

“…From 1989 through 1996, we isolated unidentifiable mycobacteria from specimens taken from four human patients and one goat. Isolates shown to be similar by means of gas liquid chromatography (GLC) analyses of cellular fatty acid and alcohol composition and biochemical testing (12) were also detected among environmental isolates grown from water taken from Finnish streams in 1990 (4). These isolates have recently been verified as M. bohemicum by partial sequencing of the 16S rRNA gene.…”