Application of Median Lethal Concentration (LC50) of Pathogenic Microorganisms and Their Antigens in Vaccine Development

Abstract Objective: Lack of ideal mathematical models to qualify and quantify both pathogenicity, and virulence is a dreadful setback in development of new antimicrobials and vaccines against resistance pathogenic microorganisms.Hence, the modified arithmetical formula of Reed and Muenchhas been integrated with other formulas and used to determine bacterial colony forming unit/ viral concentration, virulence and immunogenicity from LC50s established in the laboratories. Results: Microorganisms’antigens tested are Staphylococcus aureus, Streptococcuspneumonia, Pseudomonas aeruginosa in mice and rat, Edwardsiellaictaluri, Aeromonashydrophila, Aeromonasveronii in fish, New Castle Disease virus in chicken, Sheep Pox Virus, Foot-and-Mouth Disease Virus and Hepatitis A virus in vitro, respectively. The LC50s for the pathogens using different routes of administrations are 1.93 x 103(sheep poxvirus) and 1.75 x 1010 for Staphylococcus aureus (ATCC29213) in rat respectively. Titre index (TI) equals N log10 LC50 and provides protection against lethal dose in graded fashion which translates to protection index. N is the number of vaccine dose that could neutralize the LC50. Hence, parasite inoculum of 103 to 1011could be used as basis for determination of median lethal dose(LD50), LC50 and median bacterial concentrations (BC50)determination, pathogenic dose for immune stimulation should be sought at concentrations less than LC10.