[Assessment of bacterial counts in the meat-processing industry. II. The plate-loop method and the droplet method...

Two methods used in making bacterial counts of meat and surfaces are discussed. When the plate-loop method is used, dilutions are prepared with calibrated loops in spotting tiles. These loops are also used to swab droplets of these dilutions on quadrants of previously dried agar plates. A formula is presented, which may be used in calculating bacterial counts. When the droplet method is adopted, an apparatus is used to prepare dilutions in tubes containing liquid agar. Drops of agar then are transferred into empty Petri dishes by this apparatus. After incubation, the colonies which have grown in these droplets are counted by a viewer included in the apparatus. Both the plate-loop method and the droplet method (if slightly modified) were found to satisfy the criteria simplicity, reliability and saving time and material. This only holds good when accurate counts are made and when bacterial counts are more than 2,500 bacteria per gram or per sq. cm. When these conditions are complied with, the two methods are suited for routine studies of large numbers of samples.