in Seattle, on a standardized single-disk method for antibiotic susceptibility testing ".. . consolidate(s) and update(s) previous descriptions of the method and provide(s) a concise outline for its performance and interpretation." Clinical microbiologists were relieved that finally a disk diffusion method had been standardized, could be used with ease, and provided reliable results as compared with minimum inhibitory concentration tests. The pivotal role of Hans Ericsson's theoretical and practical studies (H. Ericsson and G. Svartz-Malmberg, Antibiot. Chemother. 6:41-74, 1959), as well as earlier reports by some of the authors of the publications cited, must be mentioned as a matter of fairness. Most of the recommendations given are still valid today even though some of the antimicrobial agents are obsolete, new ones have been added, some zone sizes had to be modified, and new media were designed for Haemophilus influenzae and Neisseria gonorrhoeae. Recommendations of the National Committee for Clinical Laboratory Standards continue to be based on this publication; the "Kirby-Bauer" method is, among the many disk methods used in other countries, still the one that has been researched most thoroughly and updated continuously.

The minimum bactericidal concentration of oxacillin for Staphylococcus aureus was shown to be considerably influenced by technical and definitional factors, particularly by the survival of some organisms on the walls of test tubes and by the growth phase of the inoculum. Attention to technical detail greatly improved reproducibility, and log-phase cultures of all strains showed >99.9%o killing in 24 h, at or close to the minimum inhibitory concentration, including

Seven laboratories participated in a collaborative study to

Predominant bacterial flora resident in subgingival plaque was characterized and evaluated in relation to the etiology of periodontal disease. Small groups of clinically and radiographically identified periodontal patients and control subjects were studied. A comprehensive inventory of cultivable flora was made. The most common group of organisms were the Gram‐positive rods, the majority of which were Actinomyces. A larger proportion of anaerobic Gram‐negative rods were isolated than indicated in the results of previous studies. Considerable variability in floral content was found in different sites in the same patient. However, no statistically significant differences were observed in the flora between clinically normal and pathological sites of the same patients. A significantly greater number of facultative Actinomyces was present in the flora of periodontal patients as compared to control subjects. Sera from the same nine subjects were assayed by indirect immunofluorescence for circulating antibodies to 12 strains of plaque bacteria. No differences in antibody titers were observed between sera from periodontal patients and control subjects.

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