- Miles and Misra method
The Miles and Misra Method (or surface viable count) is a technique used in Microbiology to determine the number of colony forming units in a bacterial suspension or homogenate. The technique was first described in 1938 by Miles, Misra and Irwin who at the time were working at the LSHTM. The Miles and Misra method has been shown to be precise.
- A calibrated dropping pipette, or automatic pipette, delivering drops of 20μl.
- Petri dishes containing nutrient agar or other appropriate medium.
- Phosphate Buffered Saline (PBS) or other appropriate diluent.
- Bacterial suspension or homogenate.
- The inoculum / suspension is serially diluted by adding 1x of suspension to 9x of diluent. When the quantity of bacteria is unknown, dilutions should be made to at least 10-8.
- Three plates are needed for each dilution series, for statistical reasons an average of at least 3 counts are needed.
- The surface of the plates need to be sufficiently dry to allow a 20μl drop to be absorbed in 15-20 minutes.
- Plates are divided into equal sectors (it is possible to use up to 8 per plate). The sectors are labelled with the dilutions.
- In each sector, 1 x 20 μl of the appropriate dilution is dropped onto the surface of the agar and the drop allowed to spread naturally. In the original description of the method a drop from a height of 2.5 cm spread over an area of 1.5-2.0 cm. It is important to avoid touching the surface of the agar with the pipette.
- The plates are left upright on the bench to dry before inversion and incubation at 37°C for 18 – 24 hours (or appropriate incubation conditions considering the organism and agar used).
- Each sector is observed for growth, high concentrations will give a confluent growth over the area of the drop, or a large number of small/merged colonies. Colonies are counted in the sector where the highest number of full-size discrete colonies can be seen (usually sectors containing between 2-20 colonies are counted).
- The following equation is used to calculate the number of colony forming units (CFU) per ml from the original aliquot / sample:
- CFU per ml = Average number of colonies for a dilution x 50 x dilution factor.
- ^ Miles, AA; Misra, SS, Irwin, JO (1938 Nov). "The estimation of the bactericidal power of the blood.". The Journal of hygiene 38 (6): 732–49. PMID 20475467.
- ^ Hedges, AJ (2002 Jun 25). "Estimating the precision of serial dilutions and viable bacterial counts.". International journal of food microbiology 76 (3): 207–14. PMID 12051477.
Wikimedia Foundation. 2010.
Look at other dictionaries:
Colony-forming unit — For the human hematopoietic cell, see Hematopoietic stem cell. In microbiology, colony forming unit (CFU or cfu) is a measure of viable bacterial or fungal numbers. Unlike direct microscopic counts where all cells, dead and living, are counted,… … Wikipedia
Company rule in India — For usage, see British Empire in India Company rule in India Colony of the East India Company ↓ … Wikipedia
Varanasi — Infobox Indian Jurisdiction native name = Varanasi locator position = left latd=25.282 |longd=82.9563 state name = Uttar Pradesh district = Varanasi leader title = Mayor leader name = Kaushalendra Singh altitude = 80.71 population as of = 2001… … Wikipedia
Antibiotic sensitivity — determination.Ideal antibiotic therapy is based on determination of the aetiological agent and its relevant antibiotic sensitivity. Empiric treatment is often started before laboratory microbiological reports are available when treatment should… … Wikipedia
India — /in dee euh/, n. 1. Hindi, Bharat. a republic in S Asia: a union comprising 25 states and 7 union territories; formerly a British colony; gained independence Aug. 15, 1947; became a republic within the Commonwealth of Nations Jan. 26, 1950.… … Universalium
Desalination — This article is about removing salt from water. For soil desalination, see Soil salinity control. Water desalination Methods Distillation Multi stage flash distillation (MSF) Multiple effect distillation (MED|ME) Vapor compression (VC) Ion… … Wikipedia
Asia — /ay zheuh, ay sheuh/, n. a continent bounded by Europe and the Arctic, Pacific, and Indian oceans. 2,896,700,000; ab. 16,000,000 sq. mi. (41,440,000 sq. km). * * * I Largest continent on Earth. It is bounded by the Arctic Ocean, the Pacific Ocean … Universalium
South Asian arts — Literary, performing, and visual arts of India, Pakistan, Bangladesh, and Sri Lanka. Myths of the popular gods, Vishnu and Shiva, in the Puranas (ancient tales) and the Mahabharata and Ramayana epics, supply material for representational and… … Universalium
Indus Valley Civilization — Extent of the Indus Valley Civilization … Wikipedia
Space elevator — A space elevator for Earth would consist of a cable anchored to the Earth s equator, reaching into space. By attaching a counterweight at the end (or by further extending the cable upward for the same purpose), the center of mass is kept well… … Wikipedia