The role of home-made ice cream as a vehicle of Salmonella enteritidis phage type 4 infection from fresh shell eggs.

A family outbreak of Salmonella enteritidis PT4 infection is described in which home-made ice cream was identified as the vehicle of infection. The ice cream contained approximately 10(5) S. enteritidis PT4 organisms per gm and was probably contaminated by an infected shell egg containing between 10(5)-10(8) organisms. The continued relevance of the Chief Medical Officer's warning on the use of raw shell eggs is highlighted. Home-made ice cream using the same recipe as ice cream that had been incriminated as the cause of the family outbreak of S. enteritidis PT4 infection was used to study the growth of the organism that might have occurred in the 3-4 h it took to prepare the product. When the inoculum was in the stationary phase, as it would be from shell or other cross contamination, there was a lag phase of 3 h before growth occurred at room temperature. Even when actively multiplying organisms were introduced, as may be found in an infected egg, there was less than 3 log(10) increase in the salmonella count in 4 h at room temperature. It was, therefore, given the high S. enteritidis count, unlikely that the ice cream was cross-contaminated. By contrast, raspberry sorbet at pH 3.73 proved to be lethal to a large inoculum of S. enteritidis and may be a relatively safe raw egg containing product.

Case-control study of infections with Salmonella enteritidis phage type 4 in England.

OBJECTIVE: To determine the source of indigenous sporadic infection with Salmonella enteritidis phage type 4. DESIGN: Case-control study of primary sporadic cases identified by the Public Health Laboratory Service between 1 August and 30 September 1988. SETTING: PHLS Communicable Disease Surveillance Centre, Division of Enteric Pathogens, 11 PHLS laboratories, and 42 local authority environmental health departments in England. SUBJECTS: 232 Patients (cases) with confirmed primary sporadic infection, for 160 of whom (88 female) (median age 30 years, age range 4 months to 85 years) data were obtained by questionnaire about consumption of fresh eggs, egg products, precooked chicken, and minced meat in the three days and one week before onset of the symptoms. Up to three controls, matched for neighbourhood, age, and sex (if aged greater than 11 years), were asked the same questions for the same calendar period. MAIN OUTCOME MEASURE: Association of primary sporadic infection with consumption of suspected food items. RESULTS: Illness due to S enteritidis phage type 4 was significantly associated with consumption of raw shell egg products (homemade mayonnaise, ice cream, and milk drinks containing eggs) (matched p = 0.02) and shop bought sandwiches containing mayonnaise (matched p = 0.00004) or eggs (matched p = 0.02). Illness was also significantly associated with eating lightly cooked eggs (unmatched p = 0.02), but not soft boiled eggs, and precooked hot chicken (matched p = 0.006). Reported consumption of eggs was not appreciably different between cases and controls before or after the median date of interview. CONCLUSIONS: Fresh shell eggs, egg products, and precooked hot chicken are vehicles of S enteritidis phage type 4 infection in indigenous sporadic cases. Public health education and reduction in contamination of eggs and infection of poultry with S enteritidis are needed to reduce the incidence of human infection.

Two outbreaks of Salmonella enteritidis phage type 4 infection associated with the consumption of fresh shell-egg products.

In 1988 there were two outbreaks of infection with Salmonella enteritidis phage type 4 in adjacent local authorities. The first affected 18 of 75 helpers and guests who attended a private function. Investigations revealed that home-made vanilla ice-cream containing uncooked eggs was the vehicle of infection and the causative organism was identified at the premises of the egg producer. The second affected 84 of 422 delegates attending a conference dinner, and 12 of 50 hotel staff at risk. A dessert made with lightly-cooked egg yolk and raw egg white was associated with infection, and the epidemic strain was cultured from the shell of an egg and an environmental sample from the producer's farm. It is of interest that one outbreak involved free-range and one battery-produced eggs, and that in one the vehicle was prepared at home and in the other in commercial premises. In neither incident was any deficiency in standards of egg production or catering practice discovered.

Campylobacters in man and the environment in Hull and East Yorkshire.

Campylobacter organisms isolated from water samples taken weekly from ponds and land-drains in the City of Hull were compared with isolates from humans. Of 314 campylobacter organisms isolated from patients, 237 (75.5%) of the strains were identified as typical Campylobacter jejuni, whilst of 125 identified strains isolated from the water samples, 85 (68%) resembled C. jejuni in most respects but were hippurate hydrolysis negative by the Hwang and Ederer method. The ponds and land drains in the city were therefore not a source of campylobacteriosis in the people living near these water courses. The atypical C. jejuni strains isolated from the environment may be mistaken for the C. jejuni strains which cause human infection. It is therefore essential that such strains are fully identified before attributing human and animal infections to their ingestion.

The pathogenicity of environmental campylobacters--a human volunteer experiment.

Three human volunteer experiments were performed in which river water expected to contain campylobacter organisms was ingested. Despite the ingestion of over 44,000 organisms in one experiment, the subject did not suffer any symptoms, nor were campylobacter organisms excreted, nor was an antibody response to the ingested strains detected. The campylobacter organisms ingested resembled Campylobacter jejuni on colonial and microscopic morphology but were hippurate negative, and were distinct from C. coli. These environmental campylobacter strains appear to be non-pathogenic, however they may be mistaken for C. jejuni or C. coli if they are not fully identified.

Specific and non-specific resistance to aminoglycosides in Escherichia coli.

The turbidimetric responses of a strain of Escherichia coli K12 to gentamicin and tobramycin were investigated. Both agents showed antibacterial activity below the conventionally measured minimum inhibitory concentration, but exposure to such subinhibitory concentrations of either agent generated a bacterial population which was able to grow in previously inhibitory concentrations at a rate equivalent to that of the parent culture. The increase in resistance was non-specific in that both aminoglycosides were equally affected, and was unstable on multiple passage in drug-free broth. The response to tobramycin was unaffected by the presence of an R factor conferring gentamicin resistance, but exposure of the R factor bearing strain to gentamicin caused a concomitant increase in the resistance to tobramycin, apparently by a non-specific adaptive mechanism similar to that observed with the parent strain. It is suggested that prior treatment of a gentamicin-resistant organism with gentamicin (as may occur during blind therapy) may adversely affect the subsequent response to other aminoglycosides.