A single predominant toxigenic clone has been implicated in a sustained outbreak of antibiotic-associated diarrhea that affected elderly patients. The "endemic" clone transmitted for the 25-month study period was linked to an index case shedding a toxigenic EP type 1 strain that occurred 21 months prior to the initial outbreak on the medical teaching unit. The patient environment in the affected units was found to be contaminated with the same clone, possibly due to shedding of organisms by fecally incontinent symptomatic patients. The extrinsic factors contributing to the endemic transmission of this one clone still are not well understood.

Six selective isolation media were evaluated for their ability to support the growth of Campylobacterjejuni. Colony counts of 70 isolated strains of C. jejuni and recovery studies on these strains in simulated positive feces samples demonstrated that Bolton and Hutchinson' charcoal, cefoperazone, deoxycholate agar and Karmali's charcoal-based selective medium produced the highest recovery rates with the greatest suppression of other fecal flora. C. jejuni colonies were more easily recognized on charcoal-based selective medium. A clinical evaluation performed on 2,780 human, animal, and avian feces specimens confirmed the results of the laboratory investigation. From human samples, 4 more strains of C. jejuni were isolated on charcoal-based selective medium than were isolated on Skirrow medium, and 19 more strains of C. jejuni or C. coli were isolated on charcoal-based selective medium from animal specimens. Suppression of normal fecal fora was also greater on charcoal-based selective medium.

Three instances of Serratia marcescens septicemia in two patients following infusion of platelet concentrates stored at 22 C, and the isolation of the organism from one unit of a platelet concentrate, led to a study to determine the possible sources of such contamination. Cultures of the available blood products, derived from the same blood donations used to prepare the suspect platelet concentrates, yielded Serratia marcescens from two units of cryoprecipitate and from one unit of red blood cells. All other available blood products were sterile. Serratia marcescens was isolated in considerable numbers from 82 per cent of the vacuum tubes from one manufacturer's lot in use in the transfusion center at the time of the septic episodes. Six other lots of vacuum tubes prepared by the same manufacturer in use at the same time were sterile. The organism was not found in samples from other equipment, materials or personnel involved in the preparation of the blood products. Simulation of the blood collection technique using vacuum tubes from the contaminated lot, when filled from an in‐line needle as used following the blood collection procedure, gave contamination of the primary pack with Serratia marcescens in five of the six experiments attempted. The contaminated vacuum tubes were thus considered the most likely source of contamination of the platelet concentrates.