Which value should be used as the lethal concentration 50 (LC₅₀) with bacteria?

Abstract

Computations of lethal concentration 50 (LC₅₀) of a data-set of a toxicity study on an herbicide against a cyanobacterium were performed by general linear regression, Spearman-Karber and probit transformation methods, for evaluation of the methods used. It is shown that the linear regression method yields some faulty LC₅₀ value, while both of Spearman-Karber and probit methods yield similar and statistically respectable LC₅₀ values. In the Spearman-Karber method, a prerequisite of some uniform dose-interval of test-chemical and tiring calculations were involved. But, the probit method is less tiring and additionally computed LC₂₅ and LC₇₅ values help assess the solicited accuracy of the LC₅₀ value and other test-statistics, including minimum inhibitory concentration (MIC), highest-permissive concentration (HPC), and a few more with respect to lethal concentration 100 (LC₁₀₀) without prerequisite of any uniform dose-interval of test-chemical. Further, the redundancy of computations of standard error (SE) and 95% confidence limits (CL) of the LC₅₀ value is suggested, as CL values are so wide to spoil LC₅₀ accuracy that is solicited in toxicology.