A Comparison of Seitz and Millipore Membrane Filters for the Enumeration of Fecal Coliforms

In a comparison of two commonly used membrane filters for enumerating fecal coliform bacteria it was demonstrated that Seitz type M filters recovered statistically more colonies of bacteria than did Millipore HAWG 047S1 filters from pure cultures of Escherichia coli incubated at 44 °C. The membranes were grown on 0.4 % Teepol agar. On incubation at 37°C no significant discrepancy was found. As a reference method was used pour plating in plate count agar (Difco). It was demonstrated that incubation at 44°C did not per se inhibit propagation of fecal coliforms. Both types of filters examined were sterilized by the manufacturers with ethylene oxide. The discrepancy found can therefore not be due to sterilization procedures.