Simulation of MICROBACT Strip Assay Using Colored Liquids to Demonstrate Identification of Unknown Gram-Negative Organisms in Undergraduate Laboratory

Abstract

Identification of unknown microorganisms to the species level is an important component of a microbiology course. Modern technologies such as matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and 16S rRNA gene sequencing offer a rapid species level identification when compared to conventional phenotype-based methods, however they rely on a well-established taxonomy database and phenotypic assays can still play an important role in species determination. Another major limitation is the up-front cost of purchasing these modern specialized instruments and the requirement of skilled personnel to operate specialized equipment and software, which makes them unsuitable to use in the undergraduate teaching laboratory. Commercial biochemical identification systems such as the Oxoid Microbact™ GNB 12A/12E/24E kit is used for the identification of Enterobacteriaceae and other Gram negative bacteria in clinical and veterinary diagnostic laboratories, and food industries for disease control and treatment. In this article, we describe a method of reliably simulating this Microbact™ strip assay using artificial color liquids (which are affordable and easy to source) for the demonstration of phenotypic characterization of unknown Gram negative organisms while providing a safe teaching environment as no bacteria are used, familiarizing students with the concept of using Microbact™ 12A kit to identify a range of unknown Gram negative organisms.