Biochemical Profile-Based Microbial Identification Systems

Abstract

The first step in microbial identification is the phenotypic assessment of the growing colony. In many cases, colonial morphology such as color, shape, size, hemolytic reaction, and growth characteristics on various selective and differential media can place an organism in a single family, genus, or even species level. In fact, assessing the ability of an organism to grow on various laboratory media along with its oxygen requirements coupled with Gram stain morphology as well as a few rapid tests such as catalase, oxidase, coagulase, and indole often provides preliminary identification for many clinically significant isolates. For example, it is very likely that an organism that grows on MacConkey agar plate and ferments lactose is a member of the family Enterobacteriaceae or an oxidase-positive non-lactose fermenting Gram-negative rod that has distinct grape odor is likely to be Pseudomonas aeruginosa.