Importance to maintain water quality
Introduction
The most likely number techniques is a means of estimating the density of viable microorganisms in a sample. It is based on sowing base seguhential volumes 10 (10, 1.0, 0.1, 0.01 etc.) To obtain an approximate value already tested in estimated populations of microorganisms, especially in cases where the density found is predominant. In the NMP a series of tubes is used and the precision of the result will depend on the number of tubes used by dilution. It consists of successive tests: presumptive, confirmative and final. The values obtained are confronted with a table indicating the bacteria NMP per ml or sample gr.
Developing
The tubes are examined at 24 and 48 hours of incubation either at 35 + 2 ° C. Through statistical tables, the calculation of the most probable number (NMP) of total coliform organisms that may be present at 100 ml of sample is carried out, from the numbers of the tubes that give positive confirmative results. This method is applicable for all types of water, including those that contain an appreciable amount of suspended matter, salty waters or salobres and sediments and mud sludge. Total coliforms: Total coliforms are enterobacteriaceae lactose-positive.
And constitute a group of bacteria that are defined more by the tests used for isolation than by taxonomic criteria. Fecal coliforms: Escherichia Coli is a subgroup of coliform fecal bacteria. This type of bacteria is found in large quantities in the intestines of hot blood people and animals. Some strains, however, can cause disease. Fermentation: biochemical process by which an organic substance is transformed into another, generally simpler, by the action of a ferment. Multiple tubos fermentation: in the multiple pipe fermentation technique.
The results are expressed in terms of the most probable number (NMP) in 100 ml. This number is based on certain probability formulas and is an estimate of the average coliform density in the sample. The coliforms are made up of several bacterial genres of the enterobacteriacee family and the classical definition of this group is based on lactose fermentation. When the multi -pipe fermentation technique is used, the coliform group is defined as: gram negative bacteria, optional anaerobias, not sporulated, in the form of a cane, lactose fermenters with gas and acid production in 48 hours at a temperature of 35 ° C.
Fecal coliforms also ferment lactose with acid and gas production at 44.5 ° C. In the multiple pipe fermentation technique, the results are expressed in terms of the most probable number (NMP) in 100 ml. This number is based on certain probability formulas and is an estimate of the average coliform density in the sample. The accuracy of each test is the function of: the number of dilutions made depending on the analyst’s experience and the origin of the sample; It is inversely proportional. Presence of gas and turbidity in some or all tubes with the highest inoculum, directly proportional.
conclusion
Absence of gas and turbidity in some or all tubes with less inoculum, inversely proportional. The technique has 3 phases: presumptive, confirmative and complete. In the presumptive phase, the triptose lauril broth and the confirmative phase for total coliforms use the bright bile green broth and for fecal coliforms the EC broth. The complete phase is done to keep quality control and allows to establish or not the presence of coliforms. The Mug Sulfate Truptose Lauril Broth is used to recover the largest number of microorganisms in the sample, while the bright green green bile breast (shill) is used in the confirmatory phase.
References
Marquez, a. P. Yo., Davila, c. M. L., Ku-Pech, p., & Segovia, P. T. (1994). Health quality of water supplies for human consumption in Campeche. Public Health of Mexico, 36 (6), 655-661.
Marked, l., Azario, r., Metzler, c., & Garcia, M. D. C. (2004). Turbidity as a basic indicator of water water quality from surface sources. Proposals regarding the study of the water treatment system and distribution in the city of Concepción del Uruguay (Entre Ríos, Argentina). Hygiene and Environmental Health Magazine, 4, 72-82.
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