An outbreak of Salmonella typhimurium DT 124 infection which affected 101 people in England in December 1987 and January 1988 was detected through surveillance of laboratory reports from medical microbiology laboratories of the NHS and PHLS. Within 1 week of noting the increase in reports, epidemiological and microbiological investigations identified a small German salami stick as the vehicle of infection and the product was withdrawn from sale. The epidemiological investigation highlighted the occurrence of a long incubation period, bloody diarrhoea. Prompt recognition and investigation of the outbreak prevented further cases of severe infection.

Pathogenic Vibrio species are naturally-occurring bacteria in freshwater and saline aquatic environments. Counts of free-living bacteria in water are generally less than required to induce disease. Increases in number of organisms towards an infective dose can occur as water temperatures rise seasonally followed by growth and concentration of bacteria on higher animals, such as chitinous plankton, or accumulation by shellfish and seafood. Pathogenic Vibrio species must elaborate a series of virulence factors to elicit disease in humans.

Activities which predispose diarrhoeal and extraintestinal infections include ingestion of seafood and shellfish and occupational or recreational exposure to natural aquatic environments, especially those above 20 °C. Travel to areas endemic for diseases due to pathogenic Vibrio species may be associated with infections. Host risk factors strongly associated with infections are lack of gastric acid and liver disorders.

Involvement of pathogenic Vibrio species in cases of diarrhoea should be suspected especially if infection is associated with ingestion of seafood or shellfish, raw or undercooked, in the previous 72 h.

Vibrio species should be suspected in any acute infection associated with wounds sustained or exposed in the marine or estuarine environment. Laboratories serving coastal areas where infection due to pathogenic Vibrio species are most likely to occur should consider routine use of TCBS agar and other detection regimens for culture of Vibrio species from faeces, blood and samples from wound and ear infections.

Enterococcisensu stricto form part of the normal gut flora (1) and may be found in the mouth, vagina and anterior urethra (2). They are opportunist pathogens which can cause serious infection including endocarditis. Nosocomial enterococcal infection appears to be increasing both in the UK (Public Health Laboratory Service [PHLS] Communicable Disease Surveillance Centre [CDSC], unpublished) and the USA (3) and to correspond to usage of broad spectrum β-lactam antimicrobial agents (4−7) and invasive surgical devices (8, 9). At the same time, the incidence of enterococci resistant or tolerant to previously commonly employed antimicrobial agents or their synergistic combinations is increasing and is compromising therapy of serious enterococcal infection. Strains of enterococci with high-level resistance to streptomycin and kanamycin (minimal inhibitory concentrations [MICs] > 2000 mg/L) were first reported in 1970 (10, 11) and rapidly became widespread (8, 12−14).

Strains ofSalmonella enteritidis, S. typhimurium and S. senftenberg inoculated into the yolks of shell eggs were found to survive forms of cooking where some of the yolk remained liquid. Survival was largely independent of the size of the initial inoculum. The organisms also grew rapidly in eggs stored at room temperature and after 2 days the number of cells per gram of yolk exceeded log 8·0. With this level of contamination viable cells could be recovered from eggs cooked in any manner.

Two small flocks of egg-laying hens, naturally infected with Salmonella enteritidis. were housed in individual cages so that their eggs could be identified. During a longitudinal study where the contents of 1119 eggs were examined, 11 were positive for S. enteritidis. One isolate was phage type (PT) 33 the others were PT4. The production of infected eggs was clustered though intermittent. The positive eggs. which were produced by 10 of the 35 hens, were all found to contain fewer than 10 salmonellas. Some birds were also apparently carrying S. hadar PT14 as this organism was isolated from the contents of six Cracked eggs.

A hospital outbreak of multiply-resistant Salmonella heidelberg infection, which affected 17 patients and 2 staff, is described. The tangible cost of the outbreak was estimated at £21 151, £17989 (85·1%) of which was borne by the hospital. The cost to the Microbiology Department was £3596 (17·0% of the total). A detailed analysis of the costs and implications for staffing disruption is given and a comparison is made with the costs of preventive activities. Ways of containing expenses in the event of an outbreak and the economic implications for clinical budgeting and privatization of the laboratory service are considered.

In February 1989 the largest reported outbreak to date in the United Kingdom of Salmonella enteritidis phage type 4 (PT4) infection occurred following a wedding reception at a hotel. One hundred and seventy-three people met the case definition of illness of whom 118 had the organism isolated from their stools. A further 17 were found to be S. enteritidis PT4 positive, but were asymptomatic. Lightly-cooked, egg-based sauces were the epidemiologically proven vehicles of infection. Investigations showed this outbreak to be the first to implicate imported European eggs as the source of infection. An unusual feature of this outbreak was a reported incubation period of less than 3 h for some of the confirmed cases of salmonellosis.

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.

Salmonella typhimurium 49a infection in a large dairy herd persisted for 3·5 years. Illness initially occurred in cows and calves but latterly although there were fewer clinical cases milk filters were culturally positive on 26 out of 73 samplings. Three associated human disease incidents occurred. Individual milk samples identified one cow as an excreter and the organism was recovered from the mammary gland of this animal at slaughter. Correlation between calving pattern, the times of calving and the occurrence of positive milk filters suggest that the cow may have been excreting the organism intermittently from the udder for 2·5 years.

The presence of enterotoxigenic and enteropathogenicEscherichia coli (ETEC and EPEC, respectively) was investigated in stool specimens of 1082 preschool children with diarrhoea and in stools of 335 healthy controls in localities in southern Yugoslavia, as well as in 566 children with diarrhoea and in 231 controls living in northern part of the country, during the seasonal peak (August— November) of enteric diseases in 1986.

ETEC were found in 114 (10·5%) children with diarrhoea and in 14 (4·2%) controls (P < 0·001) in the southern part, and in 26 (4·6%) ill children and one (0·4%) well child (P < 0·005) in the northern part of Yugoslavia. EPEC were isolated from stools of 85 (7·9%) children with diarrhoea and of 14 (4·2%) well children (P < 0·05) in localities of southern Yugoslavia, and from 22 (3·9%) ill children and from 10 (4·3%) controls in northern Yugoslavia. Nineteen EPEC strains expressed localized adherence to HEp-2 tissue culture cells; all were isolated from stools of ill children.

In southern Yugoslavia, where other enteropathogens were sought, the most commonly found agents in ill children were shigellae (17·5%), rotavirus (11·8%), ETEC, and EPEC. Potential pathogens were detected in 44·5 % cases of sporadic diarrhoea and in 15·8% controls.

This study revealed that ETEC were associated with acute diarrhoeal disease in Yugoslav preschool children. On the other hand, the diagnosis of EPEC-diarrhoea by routine determination of serogroup established the association of these agents with sporadic diarrhoea only in the 0-2 years age categories in all investigated localities. In the less developed southern part of Yugoslavia bacteria were the predominant causative agents of enteric illness during the seasonal peak of this disease.

An index of discrimination was used to assess the discriminatory power of biotyping for salmonellas of selected serotypes. Three collections of phage-typed strains of Salmonella typhimurium and Salmonella paratyphi B, previously tested for biotype, were examined. The results established that the discrimination index was high when full biotyping alone was used for differentiation of strains from international series. When biotyping was combined with phage typing, the discrimination achieved was greater than for either method used alone. These findings confirm that biotyping affords excellent discrimination of strains of S. typhimurium and S. paratyphi B and indicate that the results obtained from biotyping can be interpreted with confidence.

Salmonella enteritidis accounted for 55% of the 27478 salmonellae isolated from humans in England and Wales during 1988. Within this serotype phage type 24 has increased from 24 isolations in 1987 to 201 in 1988. The high frequency of drug resistance in this phage type has been shown to be due to the presence of plasmids belonging to Inc N and coding for resistance to a range of antimicrobial drugs among which resistance to ampicillin, streptomycin, tetracycline (AST) and T predominate. These plasmids are phage-type determining and convert strains of phage type 4 to phage type 24.

An outbreak of Salmonella paratyphi B infection in the UK associated with a fish-and-chip shop is reported. The source of infection for the first three cases was believed to be a food handler who was infected overseas 6 years earlier. His wife whose faeces and urine were originally culture negative continued to run the shop but subsequently her faeces became positive on one occasion. She was considered to have been the source of two further cases, and secondary household spread of infection from these two cases resulted in one symptomatic and two asymptomatic infections. A second household contact of the proprietor also became a faecal excretor 2 months later. We recommend that food handlers living in households or in intimate contact with eases or carriers of S. paratyphi B should be put off work until all household contacts cease excreting the organism.

We reviewed data from the Vessel Sanitation Program (VSP), established by the US Public Health Service in 1975, to describe the epidemiology of shipboard diarrhoeal outbreaks, determine the risk of outbreak-related illness among cruise ship passengers, and evaluate changes in rates and patterns of shipboard diarrhoeal illness since the VSP was implemented. When the programme began, none of the cruise ships passed periodic VSP sanitation inspections; since 1978, more than 50% of ships have met the standard each year. On cruises lasting 3–15 days and having at least 100 passengers, diarrhoeal disease outbreaks investigated by the Centers for Disease Control decreased from 8·1 to 3·0 per 10 million passenger days between 1975–79 and 1980–85. The proportion of outbreaks due to bacterial pathogens (36%) did not change. Seafood cocktail was implicated in 8 of 13 documented food-borne outbreaks. The risk of diarrhoeal disease outbreaks on cruise ships appears to have decreased since implementation of the VSP but has not been eliminated.

A point source outbreak of haemorrhagic colitis due to Escherichia coli O 157. H7 producing verocytotoxin (VT), took place following a christening party in Birmingham in June 1987. Twenty-six people were affected, six were admitted to hospital and one developed haemolytic uraemic syndrome: there were no deaths. VT + E. coli O 157. H7 was isolated from 13 (57%) of 23 faecal specimens from affected people and from 3 (9%) of 33 specimens from asymptomatic people. Free VT was detected in the faeces of one further asymptomatic person. Illness was associated with eating turkey-roll sandwiches (P < 0·001) suggesting that cold meats might be an important source of infection.

Cheese made from sheep milk was implicated in food-poisoning incidents in December 1984 and January 1985. Bacteriological examination of batches of cheese failed to reveal a viable pathogen but enterotoxin A produced by Staphylococcus aureus was present. This was the first time that enterotoxin was detected in a food produced in the UK which was associated with poisoning and from which viable Staph. aureus could not be isolated. Subsequent detailed examination of milk, yoghurt and cheese from the same producer revealed that contamination with Staph. aureus was associated with post-infection carriage as well as clinical illness in ewes on the farm. Strains producing enterotoxin A were still intermittently present in the bulk milk used for cheese production nearly 2 years afterwards, apparently in the absence of clinical illness in the sheep. The possible effects of heat treatment are discussed. Any changes in legislation should cover all non-human mammalian milk used for human consumption.

Vero-cytotoxin (VT) producing Escherichia coli serogroup O157 have been isolated from patients with diarrhoea, haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS). A phage-typing scheme developed in Canada has been used to type 155 VT+ E. coli O157 serogroup isolated from sporadic infections in the UK since 1983, and 48 strains from HC or HUS outbreaks. Twelve phage types were identified of which three, types 49, 51 and 52, have not been found in North America. All strains carried a 60 × 10 plasmid and most VT1+VT2+ strains also had a 5 × 10 plasmid coding for colicin D production. The majority of strains producing both VT1 and VT2 belonged to phage type 1, or the related types 4, 8 and 14. Most strains producing only VT2 belonged to types 2 or 49. Four outbreaks were included in the survey. Three had strains of a single phage type while strains from the fourth outbreak were more variable. The distribution of phage types throughout the UK showed no marked geographical variations.

Hospital isolates of Enterobacter cloacae were analysed by polyacrylamide gel electrophoresis for enzyme polymorphism and the results were compared with established serotyping, phage typing and biotyping techniques. Initially, the diversity of electromorphs of 13 enzymes was determined on a representative set of 62 distinct strains. Two broad clusters of strains were found in the species, and analysis by serotype suggested a limited diversity within the most frequent o serotvpes. A subset of three enzymes, lactate dehydrogenase, 6-phosphogluconate dehydrogenase, glutamate dehydrogenase and an unidentified marker, were selected and used to type groups of hospital isolates. There was good general agreement between the two systems, although the enzyme method failed to distinguish between some strains with the same serotype. This method provided useful epidemiological information and, in the absence of established typing systems, it is a practical approach to subdividing the species.

Eight non-O157: H7 Vero cytotoxin (VT)-produeing Escherichia coli (VTEC) strains isolated from ill persons and nine bovine and lamb strains of serogroups matching the human strains, were characterized for various properties known to be associated with E. coli virulence. Five different serogroups were represented: O5. O55, O103, O111 and O153. The bovine and lamb strains produced VT1, while 3 human strains produced VT1, 3 produced VT2 and 2 were positive for both VT1 and VT2. The strains were non-haemolytic on horse blood agar, did not produce either heat stable toxin A (STA) or heat labile toxin (LT), and were non-invasive. The CVD419 probe which has been proposed to identify enterohaemorrhagic E. coli (EHEC) hybridized with all of the 05 and 0103 strains, none of the 055 and 0153 strains, and 3 of the 4 0111 strains. The strains carried several different sized plasmids and hybridization of Southern blots with the CVD419 probe identified plasmids ranging in size from 42 × 10 to 90 × 10. The strains did not hybridize with the enteroadherence factor (EAF) probe derived from an enteropathogenic strain and associated with the ability to give localized adherence to HEp-2 cells. Nevertheless five of the strains adhered in a localized pattern to HEp-2 cells and Intestine 407 cells. Adhesion to either HEp-2 or Intestine 407 cells did not correlate with hybridization with the CVD419 probe or haemagglutinating properties.

Twenty cultures comprising 13 clinical isolates of Enterobacter cloacae from two hospitals. the type and another reference stain of E. cloacae and the type strains of four other Enterobacter sp. and of Escherichia coli, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDSPAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis of a numerical analysis which divided the clinical isolates into nine clearly defined protein types. Comparison with established typing methods indicated that the discrimination of SDS-PAGE was similar to that achieved with conventional typing methods and all strain groups recognized by combined sero/phage typing were also found by SDS-PAGE. In addition, protein typing sub-divided a group of four serotype O3 isolates that were difficult to distinguish by phage typing. We conclude that high-resolution SDS-PAGE of proteins provides an effective method of typing isolates of E. cloacae.