Introduction of Air Microbiology
Air microbiology is the study of microorganisms present in the atmospheric air that may be either bacteria, archaea, fungi, and viruses. It is a subarea of environmental microbiology. Here we discuss the presence of bacteria in the air. Demonstration estimation of the number of bacteria carrying particles in the air is significant and its bacteria load variation in the following situations.
- In the premises where safe working depends on the bacterial content in air being kept at a very low level and premises where certain foods or pharmaceutical materials are prepared, the monitoring of density of microbial pathogens in the air is a priority.
- The number of bacteria in the air at any given time depends on the number of person presents, the amount of their body movement and the amount of disturbance of their clothing, etc.
- The infections that can be transmitted through air include wound infections, tuberculosis, anthrax, streptococcal and staphylococcal infections.
- The settle plate method and slit sampler method are two methods used for routine bacteriological examination of the air.
- We concern here with the Settle plate method.
Principle of settle plate method for Air Microbiology
In the settle plate method, Petri dishes containing an agar medium of known surface are left open for a measured period of time. Large bacteria-carrying dust particles settle onto the medium. The plates are incubated and a count of the colonies bacteria capable of growth on the medium.
Requirements of settle plate method for Air Microbiology
Equipment and other accessories required are as follows-
- Petri plates of nutrient agar
- Plate microscope
- Set of biochemical tests for identification bacteria is there is the growth of organisms
The procedure of settle plate method for Air Microbiology
- Prepare nutrients agar media, pour it into the plate and dry off any surface moisture.
- Remove the cover of the Petri dish in its chosen position for the measured period of time, and then replace its lid.
- Incubate the plates aerobically for 24 hours at 37°C.
- Count the colonies, preferably with the use of a plate microscope.
- Perform biochemical tests depending on the nature of the organism.
- For example, in the case of Staphylococcus aureus perform, a Gram stain, Catalase test, coagulase test while in the case of Pseudomonas aeruginosa oxidase test, TSI, SIM, urease hydrolyzation, and citrate utilization test.
Quality Control of settle plate method for Air Microbiology
The Petri dish agar plates should remain open for a specified and adequate time.
Observations for of settle plate method for Air Microbiology
Observe the colonies growth on the medium after incubation.
Results and Interpenetration of settle plate method for Air Microbiology
The growth rate on the medium in a given time indicates the bacterial load a given area.
Organisms can be isolated using respective biochemical tests.
In the case of Mycobacterium tuberculosis, long incubation with a selective medium is needed.
List of bacteria commonly found in air
- Staphylococcus aureus
- Streptococcus pyogens
- Mycobacterium tuberculosis
- Pseudomonas aeruginosa
- Bacillus anthracis
- Bacillus subtilis
- Proteus vulgaris
- The number of bacteria in the air given time is dependent on the number of presents, the amount of their body movement, and the amount of disturbance of their clothing, etc.
- The settle part method and slit sampler are the two methods used for routine bacteriological examination of the air.