The effect of formulation of parenteral solutions on microbial growth--measurement of D- and z-values

In order to assess the sterilization conditions for parenteral solutions, the microbial inactivation kinetics of steam resistant spores of Clostridium sporogenes were evaluated. The D-value or death rate kinetics as well as z-values were obtained for several formulation categories of solutions employing a miniature steam retort. Amino acid and heparin solutions provided appreciable microbial resistance as demonstrated by resulting high D- and low z-values. The addition of electrolytes to carbohydrate solutions resulted in increased microbial resistance compared to carbohydrate solutions without electrolytes. A categorization of solutions and their potential impact on microbial thermal resistance will be presented.