No abstract

An outbreak of gastroenteritis caused by calicivirus began amongst residents and staff of an old persons home 24 hours after the proprietor's dog had been sick. Serological evidence suggests that the calicivirus isolated from one of the cases may be capable of infecting dogs as well as man. The virus strain responsible for this outbreak differs antigenically from those associated with two other outbreaks in the U.K. and one in Japan. The characteristic morphology of calicivirus is lost if stool is stored at -70 degrees C.

The surviving populations of Campylobacter jejuni serotypes following freezing or heat were found to be more sensitive to rifampicin and sodium deoxycholate on subsequent culture. Thus while control cultures had an IC50 of greater than 20 micrograms/ml rifampicin those of injured cells were less than 5 micrograms/ml. Treatment with EDTA caused almost identical changes in resistance suggesting that the altered resistance pattern of injured cells was due to loss of the barrier properties of the bacterial outer membrane.

The number of reported cases of food poisoning and food-borne disease continues to increase in most countries. The published figures are recognized as being only a small fraction of the true total and the problem is clearly both very large and international.Of the variety of micro-organisms responsible for outbreaks, Salmonella spp. are by far the most frequently incriminated and in the United Kingdom these organisms cause over 90% of cases (Epidemiology, 1986). The almost universal presence of these organisms in certain common foods, their ability to grow in a wide variety of foodstuffs over a substantial temperature range, the ease with which dissemination occurs from person to person and the prolonged period of excretion following recovery are the properties which, taken together, distinguish Salmonella spp. from other food-poisoning organisms. It is because of these characteristics that salmonellas are really the only food-poisoning organisms in which human beings as carriers pose potential problems as sources of outbreaks. This review is, therefore, confined to a consideration of the practical significance of the faecal carriage of salmonellas by asymptomatic food handlers, to an evaluation of the degree of risk, if any, that such a person may pose and to an assessment as to whether the time and money devoted to the investigation and exclusion of such persons is well spent.