Occurrence of mycobacteria in biofilm samples

The occurrence of mycobacteria was studied in 50 biofilm samples from water treatment plants, domestic water supply systems and aquaria. Mycobacteria were found in 90% of the samples and their densities usually ranged between 10(3) and 10(4) cfu/cm2 (maximum density 5.6 x 10(6) cfu/cm2). Organic substances such as plastics and rubber were usually colonized by larger numbers of mycobacteria than inorganic substances such as copper and glass. The highest mycobacterial densities were found on plastic surfaces which were continuously perfused with water at temperatures between 22 and 30 degrees C. The species identified include Mycobacterium chelonae, M. flavescens, M. fortuitum, M. gordonae, M. kansasii, and M. terrae/nonchromogenicum. The occurrence in microcolonies indicate that biofilms may be an important replication site of aquatic mycobacteria.