1Contribution No. 308, Department of Dairy Science, and contribution No. 390, Department of Bacteriology, Kansas Agricultural Experiment Station, Manhattan; supported in part by research grant E-3157 from the National Institutes of Health, and the Public Health Service.
2Department of Dairy Science, Kansas State University.
3Department of Bacteriology, Kansas State University.
4Kansas State Board of Health, Division of Public Health Laboratories. The authors thank Ranjit S. Kadan, graduate student, Department of Dairy Science, for his help in preparing this manuscript.