PCR as a specific, sensitive and simple method suitable for diagnostics

PCR technology is a widespread method that has not reached students laboratory in anything else than a typical amplification reaction. We describe a simple application of PCR in pathogen diagnostics that enables students to identify which ampicillin‐resistant organism is present in a cell culture. This experiment has been performed for one year in two “Experimental Biochemistry and Molecular Biology” courses with Biological and Chemical undergraduates. Using specific primers from the Escherichia coli β‐lactamase gene, they have been able to selectively amplify a β‐lactamase DNA fragment in E. coli but not in Staphylococcus aureus and, using different annealing temperatures, test the reaction specificity. By solving the “Study Questions”, students understood the specificity and sensitivity of the method, as well as the rationale that should be applied when a molecular weight pattern is used for calculating unknown DNA sizes.