Semi‐automated counting of bacteria and somatic cells in milk using epifluorescence microscopy and television image analysis

An epifluorescent microscope fitted with a ‘Chalnicon’ closed circuit television camera linked to an Optomax System III image analyser was used to count bacteria and somatic cells on membrane filters prepared from milk by the direct epifluorescent filter technique (DEFT). For both bacteria and somatic cells, the semi‐automated DEFT count of low count milk exceeded the visual DEFT count but this difference became proportionately less as the count increased. There was close agreement between the semi‐automated and visual DEFT counts over the range 10 5 ‐5 times 10 6 /ml for bacteria and 3 times 10 5 ‐5 times 10 6 /ml for somatic cells. The semi‐automated DEFT count of bacteria and somatic cells correlated well with the plate count and Coulter count respectively, with correlation coefficients of 0.83 and 0.81.