Detection of bacterial nitrate reductase activity by the use of a powdered reagent and rapid swab methods as compared to the conventional test.

A rapid swab method using either a dry or moist swab soaked with potassium nitrate/benzalkonium chloride solution, and a method employing a single powdered reagent were assessed as possible alternatives to the conventional test for the detection of bacterial nitrate reductase activity. Results obtained by the use of the powdered reagent agreed 100% with those obtained by the conventional method. The moist swab method had a sensitivity and predictive value of the negative test of 80% and 73%, respectively. The dry swab method was least sensitive (72%) and had the lowest predictive value of the negative test (66%). The use of the single powdered reagent, which has a long shelf life, is a reliable alternative to the use of conventional reagents A and B. Results obtained by the rapid swab methods were inferior to those obtained by the conventional method.