Plasmid profiles and resistance to antimicrobial agents among Salmonella enteritidis isolates from human beings and poultry in the midwestern United States.

In the study reported here, 121 Salmonella enteritidis isolates from human beings and 467 isolates from nonhuman sources were analyzed for plasmid pattern and susceptibility to a panel of antimicrobial agents commonly used as biologic markers. A significant (P < 0.05) number of isolates from nonhuman sources were resistant to beta-lactam antibiotics and tetracycline. Resistance to aminoglycosides, quinolones, and trimethoprim/sulfamethoxazole was uncommon. Of the 588 isolates, 445 (76%) were resistant to 2 or more antimicrobial agents. Sixty of 121 (50%) S enteritidis isolates from human beings were susceptible to all 12 antimicrobial agents, but 425 of 467 (91%) S enteritidis isolates from nonhuman sources expressed resistance to 1 or more of the antimicrobial agents used in the study. Analysis of plasmid profiles revealed that significantly (P < 0.05) more isolates from nonhuman sources had high molecular weight plasmids than did isolates from human beings. Isolates from ceca of chickens were associated with patterns of low molecular weight plasmids. Analysis of results of the study revealed similarities among S enteritidis from human beings and eggs, as determined on the basis of plasmid profiles and antibiotic susceptibility patterns, which may implicate eggs as one of the potential sources for infection of human beings. In addition, periodic monitoring of a substantial number of Salmonella isolates to detect drug resistance may be a prudent practice for use in revising the list of antimicrobial agents commonly used in human beings and other animals.

Role of Norwalk virus in two foodborne outbreaks of gastroenteritis: definitive virus association.

Two separate food-associated outbreaks of gastroenteritis occurred among Erie County, New York residents in June 1986. In one outbreak, cases of illness were estimated to have occurred in 50% of the approximately 700 persons in 13 groups who ate at an out-of-county restaurant during a seven-day period, and, in the second outbreak, illness occurred in 26 (30%) of 87 persons who attended a graduation party held in a private home. Laboratory investigation included serology (blocking radioimmunoassay) to determine seroconversion to Norwalk virus and an enzyme immunoassay for detection of Norwalk virus antigen in stools, which the investigators have found to be more specific for Norwalk virus than serology. Seroconversion to Norwalk virus occurred in 11 (79%) of 14 restaurant-related cases and seven (100%) of seven graduation party cases. Seroconversion to Norwalk virus antigen was also found in four (40%) of 10 food handlers at the restaurant and in two (100%) of two food handlers at the graduation party. Antigen was detected in the stools of three (20%) of 15 restaurant-related cases and four (67%) of six graduation party cases. No stools for viral analyses were available for testing from food handlers. All seven of the patients with Norwalk virus-positive stools were also positive by seroconversion. Widespread availability of reagents for stool antigen detection would result in confirmation of more outbreaks due to Norwalk virus and in a more timely manner.

School-based measles outbreaks: correlation of age at immunization with risk of disease.

During the Spring of 1978, students with a history of previous measles vaccination accounted for over three-forths of 203 cases of measles in a metropolitan county. Seventy cases occurred in two schools where 99% of the students were vaccinated. We analyzed countywide data to determine past patterns of measles vaccination, including outbreak control and vaccination update clinics. We also examined records of children from the two schools to assess the relationship between disease incidence and age at vaccination. When susceptibility was determined by trained health workers rather than by parents, fewer doses of measles vaccine were estimated to be needed. The majority of cases occurred among children 5 to 9 years old. Attack rates were higher for children vaccinated at 12 months of age or younger than for those vaccinated at 13 months of age or older. There were no significant differences in attack rates among children vaccinated at 13 months of age or older. These findings support recommendations for delaying routine measles vaccination until after 12 months of age and suggest that, during outbreaks, all children vaccinated prior to 13 months of age be revaccinated.

An epidemic of pediculosis capitis.

An epidemic due to Pediculus humanus capitis occurred in the public schools of Buffalo, New York, in the winter of 1973. A survey at one elementary school showed that 20% of whites and no blacks were infested, and a city-wide prevalence survey during the academic year September 1972 to May 1973 showed that 7.2% of all pupils were infested. An epidemiological investigation showed that sex, age, race, socioeconomic status, crowding, method of closeting garments, and family size influenced the distribution of pediculosis but that hair length apparently was not a factor. Poverty and ignorance appeared to contribute to the persistence of infestation.

Foodborne hepatitis A infection: a report of two urban restaurant-associated outbreaks.

The cities of Portland, Oregon, and Buffalo, New York, each experienced a restaurant-associated foodborne outbreak of viral hepatitis type A during 1975. Although there were several food handlers ill with viral hepatitis A in each of the restaurants involved, each outbreak was the apparent result of food contamination by a single food handler. In the Buffalo outbreak, food contamination was documented to have occurred for a brief period of time six days prior to onset of any symptoms in the index case. These outbreaks point out the uncommon occurrence of food contamination by individuals ill with type A viral hepatitis, the usefulness of two types of food questionnaires in identifying the vehicle(s) of transmission, and the apparent lack of benefit of widespread immune serum globulin administration as a control measure in this setting.