by gwilson on Apr.12, 2013, under Uncategorized
In Micro, we teach techniques through student projects. Early in the semester we studied Gram negative rods from foods to learn the basics of aseptic technique, pipetting and viable counts via pour plates, staining, microscopy, selective media, bacterial testing and identification, etc. Our most recent project needed to center on Gram positive cocci, so our four groups in lab chose where to do their sampling. We stayed away from places dangerous bacteria might be easily encountered, and then we sampled like crazy to see what we might recover and identify. Whether credit cards or cell phones or feet or fingertips, the groups all found Gram positive cocci and began their characterization. The result was nearly 40 unique isolates for us to investigate.
Identifying bacteria can be a long, laborious and expensive process. My students do some basic tests to get a feel for how the process is done. But we never go test-by-test, day-by-day to definitively identify our isolates. Instead, we use BD-BBL Crystal (R) Rapid ID panels. Students inoculate the panels with their culture, snap them closed, and then toss them in the incubator overnight. For Gram positive cocci, we use the GP panels, good for a wide range of cocci and bacilli. Each panel is designed to give answers for 30 separate tests useful for identification. We have manual readers that students can use to interpret test results (based on color charts provided). But when we renovated labs a few years back we built into the budget an automated panel reader that interfaces with a computer and provides two important functions: reading all 30 tests and interpreting their results to generate an identification. It was well worth the expense.
Today I came in and read results for over 1000 biochemical tests and identified over 30 bacteria in less than half an hour. When my students come in Tuesday, they will be able to add that information to their lab reports (research posters) and analyze that information to complete their posters. Sure beats having to make the media for those tests and wash the sterilized remnants later!