A medium for the detection of Lancefield Group D cocci in skimmed milk powder by measurement of conductivity changes

摘要

A selective medium for the detection of Lancefield Group D cocci in skimmed milk powder by conductivity measurements was developed and evaluated using the Bactometer M123 and Malthus 128H systems. This medium promoted large changes in conductance and capacitance. The calibration curve of detection times vs concentration of Lancefield Group D cocci showed a linear correlation coefficient of 0.93 and the method gave comparable results in both conductivity instruments. Naturally contaminated samples containingc.103cfu/g of Lancefield Group D cocci gave detection times within 16–18 h which was sufficiently rapid for the medium to be used for the routine screening of skimmed milk powde