Overcoming the Inflexibility of Most-Probable-Number Procedures

The design of most-probable-number (MPN) experiments is restricted by the availability and completeness of tables for certain dilution ratio and replicate number combinations. The results presented in this paper are from a computer program, the Most Probable Number Enumeration System (MPNES), which generates solutions and confidence limits (P = 0.05) for population estimates of MPN data. Tables generated by MPNES agreed with existing tables yet MPNES was able to generate other tables and discrete solutions for design combinations that have not been published. The program was also used to generate population estimates from fractional ba se dilution ratios. The MPNES increases the accuracy of MPN estimates by decreasing the base dilution ratio, by increasing the number of replicates per dilution or by correcting for constantly inaccurate diluent volumes. The MPNES program also adjusts for inoculation volume and initial dilution ratios. In this way, MPN experiments can be designed to better measure the organism of interest rather than have the design dictated by