The ADG held its first International Symposium at Churchill College, Cambridge, in July 1979. The second symposium was also held at Churchill College on 30-31 July, 1981, and this, the third, took place at the same college on 30-31 July, . 1983. The meeting was structured in a format which we hoped would appeal to the full range of our membership. The philosophy of the ADG is that medical microbiologists, veterinarians, toxicologists and dental bacteriologists have much to learn from each other and can best be achieved by bringing these various disciplines together frequently and in informal surroundings. Again the symposium was very generously sponsored by May and Baker Limited who met all costs of the meeting and entertained us splendidly. David Jackson and Donald Bedford were re- sponsible for coordinating with the ADG on behalf of May and Baker and, as usual, gave us their full cooperation. This book contains the full-length papers, followed by the posters presented at the meeting. This book also serves as a vehicle for the abstracts of the first meeting of the Society for Intestinal Microbial Ecology and Disease, SIMED, held in Boston, Massachusetts. An introduction to this new society by its President, Sydney M. Finegold, M.D., precedes the abstracts. M.J. Hill VI CONTENTS Preface v List of contributors VIII Introduction to the Anaerobe Discussion Group M.J. Hill XI A guinea-pig model demonstrating synergy between Escherichia coli and Bacteroides fragilis in infected surgical wounds.