23.2: Introduction

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Identification of unknown bacterial isolates is an important part of clinical diagnostics, research, quality control, etc. There are many characteristics of individual bacteria that aid in their identification. These can be as simple as observing unique cultural characteristics like colony pigmentation and metabolic characteristics like sugar fermentation. Today, clinical isolates can be identified by utilizing sophisticated metabolic and genetic tests. The state of the art is MALDI-TOF (Matrix Assisted Laser Desorption Ionization Time-of-Flight), a mass spectrometry method. This method places a bacterial isolate into a matrix material to stabilize it and then a laser is focused on the sample causing ionization of proteins in the sample. The ions are analyzed and a “mass spectrum” of the proteins is produced. The bacterial “fingerprint” spectra can be compared with large databases of bacteria and identification of bacteria can be done in minutes.

However, most clinical labs utilize a combination of high-tech methods and traditional cultural methods to identify bacteria. These low-tech methods are important in situations where high-tech equipment (costing hundreds of thousands of dollars) is not available or when an isolate doesn’t match anything in the database, or exhibits unexpected growth patterns or test results.

During the next few labs you will perform the appropriate tests on an unknown isolate in order to identify it.

Contributors and Attributions

Kelly C. Burke (College of the Canyons)