material was transferred to each of 3 tubes containing 9 ml uvm medium and to one tube containing 9 ml phosphate buffered saline pbs at ph 7 0 one ml of the 10 fold diluted material was transferred to each of 3 tubes containing 9 ml uvm medium and to one tube containing 9 ml pbs one ml of the 100 fold diluted material was transferred to each of 3 tubes containing 9 ml uvm medium i e a 3 tube most probable number procedure mpn was used with 10 1 0 1 and 0 01 ml stomached frankfurters in each set of tubes the remainder of the sample was split into 4 volumes of about 70 ml each in sterile 25 u00d7 200 mm tubes all tubes were incubated at 35 u00b0 c for 24 hours to enrich any l monocytogenes to detect l monocytogenes a 0 1 ml portion from each uvm tube was transferred to a tube containing 9 ml fraser 39 s broth and incubated 48 hours at 35 u00b0 c positive tubes were detected by darkening of the medium and viable cell number per frankfurter were determined from a 3 place mpn table the results.