Occurrence of actinomycetes in indoor air in Rio de Janeiro, Brazil

Indoor air quality is a relatively new research area in Brazil, and year by year is gaining the attention of researchers from many areas, including microbiology and chemistry. In the present work, 59 air samples were collected, using an Andersen sampler of six stages, in different points of Rio de Janeiro city, in Brazil. Colony counts of actinomycetes, bacteria and fungi were performed, showing that the actinomycetes, despite being less numerous, have a high concentration, around 90%, in the three last stages of the Andersen sampler. The occurrence of actinomycetes in the analyzed indoor environments was, on average, 11 CFU/m3, reaching maximum values of 127 CFU/m3. Sixty strains of actinomycetes were isolated from these samples and separated in six morphological groups. One strain of each group was used in some taxonomic tests, including the diaminopimelic acid analysis (DAP) and morphological tests. The results obtained indicated that the six strains belong to the Streptomyces genus. Although the conditions recommended by the Brazilian legislation were used, the Nocardia group and the thermophilic actinomycetes were not found in this study. However, depending on the species, the Streptomyces can also be considered pathogenic agents. The present results emphasize the need for special care with the indoor air quality.