MIC 303INDUSTRIAL AND ENVIRONMENTAL MICROBIOLOGY

AIR MICROBIOLOGY

Air Microbiology

Variable microflora.Air is not a medium for microbial growth but carrier for particular matter dust and droplet which may be laid with microorganisms.Type of microorganisms in air is depend on source of contamination. Ex: Burning. Caughing. Sneezing. Dust particle from earth surface and droplet of

rain.

Three types of contaminant according to physical properties:

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Definition in Air Microbiology

Aerosol: Dispersion in air of solid particles of microscopic size.Dust: Solid particulate capable of temporary suspension in air. Dust are usually derived from larger masses through the application of physical force.Fumes: Solid particles produced by condensation from the gaseous phase. Fumes are usually derived from the heating of a solid to its melting point and the subsequent cooling of the gas produced.Smokes: Particles resulting from incomplete combustion of organic matter consisting predominantly of carbon and oxides of carbon.Mists: Dispersion in air of liquid droplets usually large enough to be seen by the naked eye.

Definition in Air Microbiology

Vapour: Gaseous phase of a substance that usually exists as a liquid or solid at normal room temperature and pressure.Gas: A substance which does not normally exist as a liquid or solid at normal room temperature and pressure.

Collection and enumeration of airborne microorganisms

Two principle methods:1) Passive sampling.2) Active sampling.

Passive Sampling is usually done using Settling plate technique. Done by placing and exposed sterile agar plate in room

for several minutes and incubating the plate. visible colonies to develop and be counted, represent

individual dust particle in the air and indicates air quality.

Advantages: settle plates are inexpensive and easy use, requiring

no special equipment. They are useful for qualitative analysis of airborne

microorganisms and the data they produce may detect underlying trends in airborne contamination and provide early warning of problems.

They are also useful for directly monitoring airborne contamination of specific surfaces.

Passive Sampling

Disadvantages: only really capable of monitoring viable biological

particles that sediment out of the air and settle onto a surface over the time of exposure.

not detect smaller particles or droplets suspended in the air and they cannot sample specific volumes of air, so the results are not quantitative.

They are also vulnerable to interference and contamination from non-airborne sources and the agar growth medium in the plates may deteriorate if they are exposed for too long.

Active Sampling

Active monitoring requires the use of a microbiological air sampler to physically draw a known volume of air over, or through, a particle collection device.

Three main types:1) Impringers.2) Impactors.3) Filtration technique.

Active Sampling (Impringers technique)

use a liquid medium for particle collection. sampled air is drawn by a suction pump through a narrow inlet tube into a small flask containing the collection medium. This accelerates the air towards the surface of the collection medium and the flow rate is determined by the diameter of the inlet tube. When the air hits the surface of the liquid, it changes direction abruptly and any suspended particles are impinged into the collection liquid. Once the sampling is complete the collection liquid can be cultured to enumerate viable microorganisms. Since the sample volume can be calculated using the flow rate and sampling time, the result is quantitative.

Active Sampling (Impringers technique)

Advantages: the liquid collection medium means that the sample can

be analysed using a variety of methods, including molecular techniques such as PCR, so that results can be obtained more rapidly.

Disadvantages: Traditional designs are usually made of glass, which is

undesirable in food and pharmaceutical production sites. Impingement into liquids may also damage some

microbial cells and affect viability and overlong sampling times may allow some cells to multiply in the liquid collection medium.

Active Sampling (Impactors technique)

use a solid or adhesive medium, such as agar, for particle collection, requires the use of a microbiological air sampler to physically draw a known volume of air over, or through, a particle collection device.air is drawn into a sampling head by a pump or fan and accelerated, usually through a perforated plate (sieve samplers), or through a narrow slit (slit samplers). This produces laminar air flow onto the collection surface, often a standard agar plate or contact plate filled with a suitable agar medium. The agar plate can be removed and incubated.After incubation, counting the number of visible colonies gives a direct quantitative estimate of the number of colony forming units in the sampled air.

Active Sampling (Impactors technique)Advantages: convenience and pre-poured, gamma-irradiated contact

plates and standard petri dishes from specialist suppliers can be used with them to minimise the risk of contamination and variation.

They are also able to handle higher flow rates and the large sample volumes necessary to monitor air quality in clean rooms where the number of microbes present is likely to be very low.

Disadvantages: care must be taken not to allow agar plates to remain in the

sampler heads for too long, or the medium may dry out and deteriorate.

Microbial cells may also be damaged by mechanical stress during the sampling process and lose viability.

Active Sampling

Sieve Impactor Sampler

Slit Sampler

Active Sampling (Filtration technique)

used alternative is filtration, where the air is drawn by a pump or vacuum line through a membrane filter.The filter medium may be polycarbonate or cellulose acetate, which can be incubated directly by transferring onto the surface of an agar medium, or gelatine, which can be dissolved and analysed by culture or rapid methods. Advantage: accurate and reliable and portable filtration samplers designed for the pharmaceutical industry are available. Disadvantage: Filtration is less convenient than impaction-based sampling and may cause dehydration stress in the trapped microorganisms.

Membrane Filter for

Dust Aerosol

Sampling

Active Sampling (Filtration technique)

AIR QUALITY

Target Air Quality

Air Quality

Outdoor Air. Microorganisms usually found in outdoor air are

algae, protozoa, yeast, molds and bacteria.Indoor Air. Microorganisms population in indoor air usually

bacteria, molds and fungi.Factors influencing degree of contamination: Crowdling. Ventilation. Types of Activity. Airborne disease of men – avian flu and

tuberculosis outbreak.

Causes of Air PollutionOutdoor Air Automative discharge Gaseous discharge of factories Open burning Volcanic eruption Jet fuel discharge Waste combustions

Indoor Air Crowding Ventilation Aerosol discharge Organic solvent vapour Coughing and sneezing Type of activity

AIR BORNE DISEASES OF

MAN

Air Borne Diseases of Man

The medium of transfer is the air, in which the microbes, usually breathed, coughed, or sneezed out in droplets, pass from person to person. This group of infections includes some of the most important diseases which affect mankind. Urban and rural outdoor environments contain infections, allergens, irritants and chemical toxins that can reduce the quality of life and cause disease. Inhaled air pollution is directed at the the nose, throat and lungs. The exposed airway allows hazardous pollutants to enter the body and all tissues are ultimately exposed.

Air Borne Diseases of ManExamples of air borne diseases:

Cough, Influenza, Tuberculosis - The lung is the most common site of injury by airborne pollutants. Acute effects, however, may also include non-respiratory signs and symptoms, which may depend upon toxicological characteristics of the substances and host-related factors.Environmental Tobacco Smoke frequent upper respiratory infections, otitis media;

persistent middle-ear effusion; asthma onset, increased severity; recurrent pneumonia, bronchitis.

All the compounds found in "mainstream" smoke, the smoke inhaled by the active smoker or passive smoker → the emission from the burning end of the cigarette, cigar, or pipe.

Air Borne Diseases of ManExamples of air borne diseases:

Sick building syndrome (SBS) is a combination of a syndrome associated with

an individual's place of work (office building) or residence.

most of the sick building syndrome is related to poor indoor air quality.

frequently pinned down to flaws in the heating, ventilation or air conditioning (HVAC) systems.