MICROBIOLOGY Study Guide - 2012

CHAPTER 10. MICROBIAL ECOLOGY

10.3. AIR MICROFLORA

Microorganisms do not multiply in the air due to an insufficiency of moisture and nutrients. In addition, sunlight and desiccation have a detrimental effect on them. Nevertheless, the air always contains a certain number of microorganisms that enter it from the soil, the surfaces of plants and animals, and industrial waste products.

The numerical and species composition of air microflora is small, varies within certain limits, and is dynamic. A large number of microorganisms is present in the air of large cities, much fewer in rural areas, and the fewest are found in the air above forests, mountains, and seas. Microbial contamination of indoor air depends on the level of illumination, the degree of cleaning, the number of people present, the frequency of ventilation, etc.

The species composition of air microflora depends on solar radiation, meteorological precipitation, Temperature, population density, etc. The most frequent inhabitants of the air are micrococci, sarcinae, fungal spores, and bacilli. Indoor air predominantly contains microorganisms from the human Upper Respiratory Tract and Skin, including pathogens, specifically the causative agents of tuberculosis, diphtheria, pertussis, scarlet fever, measles, Influenza, and the common cold. The release of pathogenic microorganisms can be indirectly assessed by the presence of sanitary-indicator Microorganisms in the air—such as Staphylococcus aureus and hemolytic streptococci. The sanitary and microbiological condition of indoor air is evaluated by the total microbial count, which is the number of Bacteria found in 1 m³ of air. The air in rooms with poor sanitary and technical characteristics may contain up to 45—60 х 10³ microbial Cells per 1 m³, whereas those with good characteristics contain no more than 1—5 х 10².

In the production workshops of food enterprises, it is necessary to monitor air cleanliness and periodically control the air microflora. To reduce microbial contamination of the air, it is essential to carry out daily wet cleaning of the premises combined with ventilation and purification (filtration) of the incoming air. To disinfect the air in certain production workshops, starter culture rooms, operating theaters, isolation boxes, and cold rooms, ultraviolet lamps are installed. Chemical air purification using disinfectants is also quite effective.