Vibrio cholerae and enteric bacteria in oyster-producing areas of two urban estuaries in Australia.

Three sampling sites in oyster-producing areas of 2 estuaries were monitored at intervals of about 2 weeks for 1 year. Oysters (Crassostrea commercialis), water and sediment were examined for Vibrio cholerae, Escherichia coli and Salmonella. V. cholerae was detected in 20, 30 and 11% of oyster, water and sediment samples respectively. The highest incidence was in the autumn (March-May), with few isolations from July to October. Most isolates were non-O1 serotypes. The presence of V. cholerae and the enteric bacteria appeared to be influenced by different, but perhaps overlapping, sets of factors in these high salinity waters. There was no relationship between rainfall or salinity and the detection of V. cholerae, whereas high counts of E. coli in oysters and the presence of Salmonella were correlated wtih rainfall and, to a lesser degree, reduced salinity. High counts of E. coli were correlated with V. cholerae isolations from water and with the presence of Salmonella. Oysters concentrated E. coli effectively. The counts of E. coli in oysters were 7.3 times higher than those in water. Examination of 8 batches of purified and unpurified oysters indicated that purification reduces the incidence of V. cholerae. However V. cholerae was detected in 3 of 25 market samples of oysters, demonstrating that it can be present in oysters throughout the distribution system. The highest V. cholerae count observed in oysters was 3/g.

Serotyping of Campylobacter jejuni from an outbreak of enteritis implicating chicken.

An outbreak of campylobacter enteritis involving 7 of 17 people over a period of 5 days followed a dinner at a restaurant. A chicken casserole dish was implicated with a food-specific attack rate of 58%. Campylobacter jejuni Penner serotype 18/21/29, resistant to metronidazole, was isolated from 3 of 4 symptomatic patients and from three raw fresh chicken samples closely associated with the implicated chicken. Numbers of C. jejuni in the chicken ranged from 5.3 X 10(1) to 7.5 X 10(2) colony forming units per square centimeter of surface area. This is the first outbreak of campylobacter enteritis reported in Australia in which C. jejuni has been isolated from both human and food sources and the isolates serologically confirmed as identical.

Campylobacter jejuni: incidence in processed broilers and biotype distribution in human and broiler isolates.

Campylobacter jejuni was isolated from 18 of 40 processed broiler carcasses and 134 of 327 cloacal swabs obtained at four processing plants in Sydney, Australia. Three of four flocks examined carried C. jejuni. Eighty-two percent of chicken and 98% of human isolates from the area were of identical biotypes.

Demonstration of Viral Contamination of Oysters Responsible for an Outbreak of Viral Gastroenteritis.

Two viruses, echovirus type 8 and a reovirus, were isolated from a batch of oysters responsible for an outbreak of gastroenteritis. Characteristics of the illness, detection of Norwalk virus in the feces of one of the victims and other factors indicated strongly that the illness was due to infection with Norwalk virus. Examination of the implicated oysters and a fecal specimen from a victim failed to provide evidence of the involvement of any other causative agent. Thus laboratory evidence of human enteric virus contamination of a batch of food responsible for a viral illness has been provided.

An Australia-wide outbreak of gastroenteritis from oysters caused by Norwalk virus.

At least 2000 persons were involved in an Australia-wide outbreak of oyster-associated food poisoning in June and July, 1978. At the time, this episode presented a major health risk to the community as a whole and has subsequently posed a serious economic problem for the oyster farming and distributing industry. Although bacteriological investigations indicated some batches of oysters were contaminated by sewage, no bacterial cause could be established. The causative organism was shown to be Norwalk virus, a known cause of acute non-bacterial gastroenteritis. This virus was found in 39% of faecal specimens examined by electron microscopy and an antibody response was demonstrated by immune electron microscopy in 75% of paired sera tested. Norwalk virus has not been identified previously outside the United States of America and has not been linked to food-borne gastroenteritis before. Purification of oysters and other measures have been instituted to prevent a recurrence of the outbreak.