Gastrointestinal disorders of varying severity were observed in 239 (53%) of 455 campers and staff members at a coed summer camp in Sullivan County, New York, during July 1981. Five of seven hospitalized patients had appendectomies before the disease was recognized as yersiniosis. Yersinia enterocolitica serogroup O:8 (American strain) was isolated from 37 (54%) of 69 persons examined, including the head cook and 3 others of the 11-person kitchen staff. Of 48 food, water, and environmental samples collected from the camp area, Y. enterocolitica isolates belonging to the same serogroup and biogroup as the human isolates were recovered from dissolved powdered milk, a milk dispenser, and turkey chow mein. This laboratory finding supported the epidemiological data indicating a correlation between consumption of these foods and illness. Y. enterocolitica isolates of the same biogroup as the O:8 isolates but belonging to serogroup O:34 were also isolated from six campers and two samples of dissolved powdered milk. Pathogenicity studies on the Yersinia isolates were performed with three in vitro tests (calcium dependency, autoagglutination, and HeLa cell infection) and one in vivo test (intraperitoneal challenge of mice). Most of the serogroup O:8 human isolates and the chow mein isolate were positive in all four tests. Milk isolates of serogroup O:8 were positive in the in vitro tests but were relatively avirulent in mice, whereas serogroup O:34 isolates, regardless of source, were negative in all four tests.

Fecal specimens for Yersinia screening were obtained from a variety of wild mammals, birds, reptiles, fish, and invertebrates throughout New York state. One specimen from each of 1,426 animals was examined. A total of 148 isolates of Yersinia enterocolitica and related species were obtained from 133 (9.3%) of the animals. Y. enterocolitica was isolated from 100 (7%) of the animals tested, including 81 (10%) of 812 mammals and 19 (3.3%) of 573 birds. Y. intermedia, Y.frederiksenii, and Y. kristensenii were isolated from 39 (2.7%), 5 (0.35%), and 4 (0.28%) animals, respectively. The 81 Y. enterocolitica isolates from mammals belonged to 15 serogroups and included three pathogens: two isolates of typical serogroup 0:8, the "American strain," one from a gray fox (Urocyon cinereoargenteus) and one from a porcupine (Erethizon dorsatum); and one isolate of serogroup 0:3, bacteriophage type IXb, the "Canadian strain," from a gray fox. The most prevalent serogroups recovered from mammals were 0:6,31 (16 isolates) and 0:5,27 (6 isolates). The 19 isolates of Y. enterocolitica from birds belonged to nine serogroups and included one serogroup 0:6,31 isolate from a common grackle (Quiscalus quiscula) and two serogroup 0:5,27 isolates from great horned owls (Bubo virginianus).

colleges and universities in various parts of New York State (NYS) reported outbreaks of conjunctivitis affecting at least 1,500 students of both sexes. Of the 125 conjunctival swabs tested in our laboratory, organisms identified as nontypable Streptococculs pneumoniae were isolated in pure culture from 24% and in combination with other organisms from 22%. Although bile-soluble and susceptible to optochin, the isolates had a drycolony appearance and no typable capsule with the Neufeld capsular-swelling test. Mouse passage of four representative NYS isolates did not stimulate production of a typable capsule. We subsequently chose to refer to these isolates as S. pneumoniae-like organisms. Of primary importance to our study, all NYS isolates tested were similar in biochemical and immunological reactions, antibiotic susceptibility, and virulence in mice. Of 18 strains referred to us from three other outbreaks (California, 1980; NYS, 1981; Illinois, 1981), four of the six tested biochemically gave the same biochemical reactions as the four NYS isolates, and 16 of the 18 tested immunologically reacted strongly with antisera produced against those four isolates, showing line(s) of identity with each other and with the NYS isolates.

Nonspecific cell-mediated immunity to a relatively virulent strain of Escherichia coli was studied in mice infected with Staphylococcus aureus and elicited with specific antigens. The infected and elicited mice were protected against as intraperitoneal challenge by E. coli for an observation period of 7 days, whereas normal mice, given the same number of bacteria, died within 18 to 24 h. However, the amount of time elapsing between elicitation and challenge greatly affected the rate of protection. Little or no protection was observed in mice injected with S. aureus but not elicited or in mice injected with staphylococcal antigens but not infected with staphylococci.