INTERNAL QUALITY-CONTROL SAMPLES FOR WATER BACTERIOLOGY

A method is described for the preparation and application of a bacteri ological quality control system for use with tests for plate counts an d the enumeration of indicator organisms in water. Statistical limits are obtained and control charts prepared which are analagous to those used in analytical chemistry and clinical biochemistry laboratories. T his approach has been applied successfully in this laboratory but need s to be tested more widely. Such numerically-based systems have seldom been attempted in microbiology, especially where multiple organisms h ave been included for the simultaneous control of several tests.