BACTRIOLOGY OF AIR.pptx

BACTRIOLOGY OF AIR.pptx

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  BACTERIOLOGY OF AIR Name:Jabed Ahmed Choudhury ID: SH20MLTGNG42 Program: BSc.MLT Kaziranga University
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  INTRODUCTION • Air isnot 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 • Eg. Coughing, Sneezing
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  Microbial Content OfAir The microbial content of the air one breathes in is important, particularly when it contains pathogens. The microbial, particularly bacterial, content of air depends on the location, that is, whether it is outdoor air or indoor air
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  Airborne infection: Transmissionof infection produced by respiratory droplets less than 5 μm in size Droplet infection: Transmission of infection produced by respiratory droplets larger than 5 μm in size
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  Essential Conditions ForBacteriological Examination Of Air 1. Surgical operation theater 2. In hospital wards in which there is an outbreak of cross-infection 3. Premises where food articles are prepared and packed 4. Premises where pharmaceutical materials are prepared
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  Measurement of AirContamination The methods for bacteriological examination of air are of two types 1. Sedimentation 'settle plate' method 2. Slit sampler
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  Sedimentation 'settle plate'method Definition: A means of estimating the number of bacteriapresent in the air by permitting bacteria to 'settle'on open petri dishes (containing culture media) overa fixed duration. Droplet nuclei require more time to settle than larger particles.
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  Method: Open platesof culture media are exposed for specific periods, for example, half to one hour; then the plates are incubated at 37°C for 24 hours and the number of colonies counted ❑The method is specially used for testing the air in surgical theatres and hospital wards
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  Fig.: Bacterial Growthafter Incubation
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  Blood Agar PlatingTechnique For Air Sampling ⮚The sterile Blood agar plates were transported to operation theatres in sealed plastic bags ⮚The plates were labelled with sample number, site within the operation theatre, time and date of sample collection and control plates were kept to monitor any prior contamination of plates ⮚During air sampling sterile gloves, mouth mask and protective gown were worn to prevent self-contamination of the blood agar plate
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  ⮚The index ofmicrobial air contamination was based on the count of the microbial fallout on to petridishes left open to the air according to the 1/1/1 scheme ⮚For 1 hour, 1meter above the floor, at least 1m away from walls or any obstacle ⮚After this exposure, the plates were covered with their lids and taken to Microbiology laboratory ⮚Incubated in incubator at 37°C for 24 hours ⮚The culture plates that showed discrete macroscopic colonies were counted using digital colony counter
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  Formula for Conversionof Colony Count (on settle plate) to Counts / m3 CFU/m3 = a × 1000 p×t× 0.2 a = The number of colonies on Settle plate p = The surface measurement of plate used t = Time of exposure of settle plate ★The concentration of airborne bacteria was expressed as colony forming units per cubic meter (cfu/m3)
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  Slit Sampler Method •The Slit sampler was developed by Bourdillon (1941). • In this a rotating petridish containing suitable nutrient agar media is placed under a slit through which air is drawn.
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  • Sampling isdone for short time to avoid the interference of growth of one colony with another. Slit sampler is one of several sampling methods used for quantitation of biological aerosols • In this method, particles from the air are impinged directly on a rotating agar plate, the plate is incubated, and the colonies that develop from the bacteria-laden particles are counted • Highly efficient device and can collect upto 95% of the water droplet particles sprayed into air