Bacteria are natural inhabitants of most environments. They are isolated from virtually any surface and liquids. Bacteria proliferate when both environmental and nutritional conditions are favourable.
Bacteria can be categorised into 2 groups. The gram positive and gram negative depending on their color after gram stain test.
A Few Facts About Bacteria In Indoor Environment
- The numbers of bacteria are generally higher in naturally ventilated than in mechanically ventilated buildings
- The concentration of airborne bacteria correlate positively with the number of occupants. The higher the occupation density the higher the concentration of viable airborne bacteria
- Generally, the dominant types of bacteria in buildings are the Gram-positive bacteria such as Stapphylococcus epidermis, Micrococcus luteus (from skin) and Staphylococcus aureus (from nasal membranes and skin). Other Gram-positive bacteria found in indoor environment but not in large numbers are Bacillus spp.
- Gram-negative bacteria are less abundant indoors than Gram-positive bacteria. Elevated levels of Gram-negative bacteria are indicators of very wet conditions. Gram negative bacteria include species of Pseudomonas, Acinetobacter, Alcaligenes, and Flavobacterium
- A small number of mesophilic Streptomyces and Actinomycetes are occasionary found in buildings with dampness problems.