With the displaced Poissonđ63Īssumption for fj and for fj, we set V„ = Vf = fj, leading to Sj =đ64įj-ky/fj. Numerical value of k is addressed later). At this point it suffices to state that k exists (theđ62 The factor k is a function of the geometry of the serialđ61ĭilution experiment. Of 'spread' is a substitute for the notion of variance (that we cannotđ59Ĭompute) and is weak hence, no harm is done in adjusting it with ađ60įudge factor k. Where Sj = fj-k-JVn, and k only modifies the spread ^/Vf. f- is the observed (counted) number of colonies on plate j of the serial dilution process, for which the true number of colonies is n- with a mean j Due to uncounted colonies in the measuring process (i.e., merging of colonies that are counted as one colony due to overcrowding), f, 1đ57 The concept of Sj is given with Poisson and a shifted-Poisson probability density functions for the true n-, and for the counted (measured) f j, respectively. The following assumptions are made: (i) The true fj (when no colonies are miscounted) is described by a Poisson probability for which the variance equals the mean (Forbes et al., 2011), (ii) The probability density function for fj (with the effect of merging of nearby colonies) is aįig. The challenge is met in an ad-hoc manner. The challenge is to obtain an estimate of Sj from a single measurement fj of the jth Petri dish. Journal homepage: Estimation method for serial dilution experimentsĪvishai Ben-David a,* f j. Journal of Microbiological Methods xxx (2014) xxx-xxxĬontents lists available at ScienceDirect The method maintains this accuracy even in the presence of dilution errors of up to 10% (for both the aliquot and diluent volumes), microbial counts between 1 colony-forming units, dilution ratios from 2 to 100, and plate size to colony size ratios between 6.25 to 200. The proposed approach shows relative accuracy well within ☐.1log10 from data produced by computer simulations. The required inputs are the plate size, the microbial colony size, and the serial dilution factors. The estimate of the optimal count given by our method can be used to narrow the search for the best (optimal) dilution plate and saves time. Our method selects the best agar plate with which to estimate the microbial counts, and takes into account the colony size and plate area that both contribute to the likelihood of miscounting the number of colonies on a plate. The number (concentration) of viable microbial organisms is estimated from a single dilution plate (assay) without a need for replicate plates. A simple method is presented to estimate the microbial counts obtained with the serial dilution technique for microorganisms that can grow on bacteriological media and develop into a colony. Titration of microorganisms in infectious or environmental samples is a corner stone of quantitative microbiology. Abstract of research paper on Biological sciences, author of scientific article - Avishai Ben-David, Charles E.

Four Fold Serial Dilutions