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A serial dilution is the step-wise dilution of a substance in solution, either by using a constant dilution factor, or by using a variable factor between dilutions. If the dilution factor at each step is constant, this results in a geometric progression of the concentration in a logarithmic fashion.
In this method a measured sub-sample (perhaps 10 ml) is diluted with 100 ml of sterile growth medium and an aliquot of 10 ml is then decanted into each of ten tubes. The remaining 10 ml is then diluted again and the process repeated. At the end of 5 dilutions this produces 50 tubes covering the dilution range of 1:10 through to 1:10000.
Serial dilution of a solution results, after each dilution step, in fewer molecules of the original substance per litre of solution. Eventually, a solution will be diluted beyond any likelihood of finding a single molecule of the original substance in a litre of the total dilution product. The "Korsakovian" method may also be used.
Titer (American English) or titre (British English) is a way of expressing concentration. [1] Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positive or negative.
Dilution has been used as a method to grow and identify bacteria since the 1870s, and as a method of testing the susceptibility of bacteria to antibiotics since 1929, also by Alexander Fleming. [25] The way of determining susceptibility changed from how turbid the solution was, to the pH (in 1942), to optical instruments. [ 25 ]
The MPN method involves taking the original solution or sample, and subdividing it by orders of magnitude (frequently 10× or 2×), and assessing presence/absence in multiple subdivisions. The degree of dilution at which absence begins to appear indicates that the items have been diluted so much that there are many subsamples in which none appear.
Depending on the expected density and viability of microbes present in a liquid sample, physical methods to increase the gradient as for example serial dilution or centrifugation may be chosen. In order to isolate organisms in materials with high microbial content, such as sewage, soil or stool, serial dilutions will increase the chance of ...
The reported count is the number of colonies counted multiplied by the dilution used for the counted plate A high TVC count indicates a high concentration of micro-organisms which may indicate poor quality for drinking water or foodstuff. In food microbiology it is used as a benchmark for the evaluation of the shelf-life of foodstuffs [1]