Evaluation of Millipore Swab-Membrane Filter Kits

A laboratory performance evaluation was done on the Millipore Total-Count (TC) and SPC swab-membrane filter kits which are designed to monitor sanitary conditions on food contact surfaces and eating utensils. Hand-shaking was as effective as vortexing for dislodging bacteria from the cotton swab in vials of Millipore buffer, but bacteria were unstable in the Millipore buffer even when refrigerated at 4°C. These results indicate that the Millipore swab-membrane filter kits could be used by public health officials but both swabbing and sampling should be completed in the field and the samplers returned to the laboratory for incubation, enumeration and proper disposal. Compared to the standard pour plate, recovery of unstressed Escherichia coli cells by the TC sampler was accurate provided not more than 125 colonies were on the membrane filter of the sampler. In comparing the two kits for recovery of stressed bacteria, the Millipore TC sampler was able to recover chlorine-stressed but not heat-stressed cells, whereas the opposite results were obtained with the SPC sampler. Hence, the availability of two different Millipore kits, neither of which recovers all types of stressed bacterial cells, indicates the need for designing a newer media formulation that could accomplish this effectively using just one sampler. Once these criteria have been met, the Millipore swab-membrane filter kit could replace the more tedious and time-consuming standard method currently used for monitoring sanitary conditions related to public health.