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microbiological investigations identified a small German salami stick as the vehicle of infection and the product was withdrawn from sale.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.

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.

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.

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.

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.

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.

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.

Lipopolysaccharide (LPS) extracts obtained from Treponema hyodysenteriae of serogroups A, B, D and E, and from T. innocens were examined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), silver-staining, and immunoblotting with hyperimmune rabbit sera. All organisms possessed multiple LPS bands, but their position and number differed.

Immunoblotting of LPS with grouping sera identified three or four major antigenic LPS components in the 10-42 kDa range in all organisms: these components were largely specific to each type-organism of a serogroup, and presumably represented group antigens. Although some minor cross-reactivity occurred between LPS from organisms in the different groups, this was insufficient to merit changes to the current LPS serogrouping system for T. hyodysenteriae. Besides this LPS ‘complex’, other higher-molecular-weight material which appeared to be a common component of the treponemes examined was present in low concentrations. Organisms with different serotypes within a serogroup apparently possessed common LPS bands, but also had unique LPS bands which may account for their serotype specificity. One ‘untypable’ organism lacked group-specific LPS and was thought to be a mutant of a group B organism. The loss of serogroup LPS by the isolate suggested that this material is an external component of the cell wall. The availability of an atypical organism lacking LPS components may facilitate further studies on the pathogenesis of swine dysentery.

In October 1985, six cases of legionnaires' disease were associated with a police headquarters building. Four were amongst staff who worked in or visited the communications wing of the headquarters and two cases occurred in the local community. A case-control study implicated the operations room of the communications wing as the main area associated with infection. This wing was air-conditioned and smoke tracer studies showed that drift from the exhaust as well as from the base of the cooling tower entered the main air-intake which serviced the air-conditioning system. Legionella pneumophila serogroup 1 subgroup pontiac was isolated from water and sludge in the cooling tower pond. Contaminated drift from the top of the cooling tower was probably responsible for the two community cases. An additional discovery was that symptoms suggestive of the sick-building syndrome were associated with working in this wing.

Infections caused by mycobacteria other than Mycobacterium tuberculosis (MOTT) have often been described as common in AIDS patients. To evaluate whether infections with MOTT are specific for HIV related immunosuppression or are also frequent in patients with immunosuppression of different aetiology, data on the frequency of isolation from immunosuppressed patients with HIV infection are important. Blood, stool and urine specimens from 134 patients with non-HIV related immunosuppression, and from 55 immunocompetent subjects were examined for mycobacteria. MOTT have been isolated from one immunocompetent person but from none of the immunosuppressed patients. Since in AIDS patients an initial colonization of the gastrointestinal tract (GI-tract) with MOTT is common, GI-tract biopsy specimens from an additional 80 patients were examined microscopically and histologically for mycobacteria. Mycobacteria were not isolated from these specimens.

In the same period of time 72 AIDS patients have been examined: 7 (10%) had infections with M. tuberculosis whereas MOTT have been isolated from 16 (22%) of these patients. Mycobacteria have been found only rarely in immunocompetent patients and have not been isolated from patients with non-HIV related immunosuppression. The isolation of MOTT is highly correlated with an HIV-related immunosuppression.

A total of 250 cerebrospinal fluid (CSF) specimens were analyzed using a rapid enzyme immunoassay (Pharmacia Meningitis ETA-Test) (EIA) for the detection of antigens of Haemophilus influenzae type b, Neisseria meningitidis (serogroups A, B, C) and Streptococcus pneumoniae (25 selected types). The test is performed in less than 1 h and read by the naked eye. EIA and coagglutination (CoA) were compared with a constructed reference that comprised samples which were either positive by culture and/or on direct microscopy (DM), or in which there were positive results with both EIA and CoA for the bacteria covered by the assays. Using this reference for CSF samples assayed in a period between two meningococcal meningitis epidemics, the sensitivity was 0·86 for EIA and 0·69 for CoA, the specificity 0·95 (EIA) and 0·97 (CoA), the predictive value for a positive result 0·81 (ETA) and 0·87 (CoA) and, the predictive value for a negative result 0·96 (EIA) and 0·93 (CoA). Antibiotics had been given to 54% of the patients before admission. All of the 56 samples that were positive in any of the tests taken during an epidemic of group A meningococcal disease were detected by EIA; CoA was negative in 45% and culture/DM was negative in 32%. Sequential dilutions of two CSF samples from which H. influenzae type b had been isolated, showed the EIA to be 16–32 times more sensitive than CoA. With both technical feasibility and good sensitivity and specificity, the EIA seems to be useful and reliable for the rapid diagnosis of bacterial meningitis, especially in situations where pretreatment with antibiotics are likely.

During the last week of May 1986, a 1-week prospective study on antibiotic utilization in surgical patients was held in 104 (42%) of the 247 Belgian acute care hospitals. All surgical patients with a post-operative stay of at least 3 days were studied, involving 3112 patients. Each patient was observed for 7 days, starting from the day before surgery. Antibiotics were administered to 71·9% of all patients; 21·9% received therapeutic antibiotics and 52·9% prophylactic antibiotics; 2·9% received both. Of the 1285 patients undergoing a surgical procedure with no indication for antimicrobial prophylaxis, 50·7% nevertheless received prophylaxis; 92·8% of patients with a generally recognized indication for prophylaxis received antibiotic prophylaxis. Less than one fifth (17·1 %) of all prophylactic courses were stopped on the day of the intervention whilst 26·3% were continued up to the fifth post-operative day or beyond. The most frequently prescribed drugs for this indication included first and second generation cephalosporins and nitroimidazoles. The number of different generic drugs utilized per hospital ranged from 1 to 18 (mean: 7·7).

Selective decontamination of the digestive tract (SDD) employs oral antibiotics to eliminate aerobic Gram-negative bacilli while retaining the anaerobic flora. A combination of SDD and parenteral cefotaxime has recently been reported to strikingly reduce the incidence of infection in patients treated in an intensive therapy unit. The present study describes the effects of SDB and of cefotaxime on the immune response of mice to protein antigens. The in vivo cellular response to ovalbumin and sheep red blood cells was unchanged. However, SDD appeared to decrease the in vitro mitogenic response of spleen cells to phytohaemagglutinin, and cefotaxime similarly affected the response to Concanavalin A. The antibody response to sheep red blood cells was increased in the period after discontinuation of SDD. The antibody response was otherwise not affected. These results indicate that SDD is unlikely to have adverse effects on the immune response to protein antigens.

The overall pattern and consequences of myxomatosis in wild rabbit populations were studied at three farmland sites in lowland southern England and upland central Wales between 1971 and 1978. When results from all years were combined, the disease showed a clear two-peaked annual cycle, with a main autumn peak between August and January, and a subsidiary spring peak during February to April.

Rabbit fleas, the main vectors of myxomatosis in Britain, were present on full-grown rabbits in sufficient numbers for transmission to occur throughout the year, but the observed seasonal pattern of the disease appeared to be influenced by seasonal mass movements of these fleas. However other factors were also important including the timing and success of the main rabbit breeding season, the proportion of rabbits which had recovered from the disease and the timing and extent of autumn rabbit mortality from other causes.

Significantly more males than females, and more adults and immatures than juveniles, were observed to be infected by myxomatosis. Only 25–27% of the total populations were seen to be infected during outbreaks. Using two independent methods of calculation, it was estimated that between 47 and 69% of infected rabbits died from the disease (much lower than the expected 90–95% for fully susceptible rabbits with the partly attenuated virus strains that predominated). Thus it was estimated that 12–19% of the total rabbit populations were known to have died directly or indirectly from myxomatosis.

Although the effects of myxomatosis were much less than during the 1950s and 1960s, it continued to be an important mortality factor. It may still have a regulatory effect on rabbit numbers, with autumn/winter peaks of disease reducing the numbers of rabbits present at the start of the breeding season.

In the spring term of 1985 there was a protracted outbreak of upper respiratory tract febrile illness consistent with a clinical diagnosis of influenza in a boys' boarding school, which lasted from 23 January to 29 March. Although influenza virus infection was confirmed in 89% of cases in the first half of the term, 53% of the cases which occurred in the second half of the term had no evidence of infection with influenza virus. Between 5 February and 31 March 28 boys presented with skin rashes consistent with a clinical diagnosis of erythema infectiosum; 68% of these were associated with parvovirus B19. Investigation of the cases of clinical influenza with no identified respiratory pathogen revealed a 58% infection rate with B19. B19 DNA was identified in either throat swabs or acute stage bloods of nine pupils with influenza-like symptoms.

Cohort studies revealed that 44% of pupils aged 15–16 years were immune before the outbreak compared with only 17% of pupils aged 11–12 years. Infection in the younger group was common and was associated with influenzalike illnesses as well as rashes. Forty-eight per cent of those who did not report any symptoms were also infected with B19.

In March 1988 a general practitioner notified two cases of hepatitis A in a private boarding school. Epidemiological investigation, including testing for salivary antibodies revealed a further five cases and established immunity to, and recent infection with, hepatitis A virus (HAV). The pattern of the outbreak was described. A number of practices which would encourage cross-infection were corrected. Normal human immunoglobulin was given to contacts.

Repeat salivary testing 10 weeks later revealed that two more boys had becomereactive for anti-HAV, though at a low titre. These may have been serologicalresponses to HAV infection modified by the passive immunization.

A total of 1786 blood donors were screened for the presence of anti-hepatitis A antibod (anti HAV). 64·5% of the donors were found to be positive. The prevalence of the antibody was found to be age-related, 55% at 18 years and 75% at 65 years. No relationship was noted between the presence of antibody, foreign travel or a specific destination. Assay of antibody levels in selected seropositive individuals gave a mean level of 5· IU/ml.

The prevalence of infection in this selected population is important in thecontext of passive immunization with normal human immunoglobulin and for defining a policy of immunization with hepatitis A vaccines, which are currently undergoing clinical trials.

Firemen have been considered at occupational risk of hepatitis (HBV) infection, but proof is lacking. The aim of this study was to assess the degree of risk by determining the prevalence of serological markers of past infection with HBV in members of the West Yorkshire Fire Service. Sera from 173 firemen, 9·3% of the brigade, were tested for antibodies to HBV surface antigen and to core antigen. Those containing anti-HBs≥10 IU/L or anti-core antibody, were also tested for antibody to HBe antigen. The presence of more than one marker was used to define past infection. One sample satisfied this criterion, giving a prevalence rate of 0·6%. This compares with a rate of 1% in London blood donors. We conclude that the group shows no evidence of having been at increased risk of HBV infection. A comprehensive vaccination policy for firemen might be questionable

The efficacy and acceptability of yeast-derived recombinant hepatitis B vaccine given by the intradermal route was investigated in 221 health care volunteers. Two hundred and sixteen received a full course of three doses of vaccine. Only one subject was withdrawn because of a significant adverse reaction (psoriasis). The vaccine stimulated an antibody response in 81%. The response to the vaccine was better in women than in men (87% compared with 71%, p = 0·007) and in women below the age of 40 years compared with older women (94% compared with 76%, p = 0·01). For men the response showed a sequential decline with age for each decade (90% responders from age 29 or less, 72% aged 30—39 and 65% aged 40 or more, p = 0·04). Retrospective enquiry showed that over 90% had found the intradermal route acceptable and 59% would prefer vaccine by the intradermal route in preference to intramuscular notwithstanding local reactions. Although the seroconversion rate was of a high order in younger women the antibody titres were not high with only 9 of 215 recipients developing titres >1000 mIU/ml, a level which could be expected to ensure prolonged immunity. A fourth intradermal dose of vaccine given to 60 volunteers who had shown a low response (<38 mIU/ml) or no serological response to a three-dose course stimulated a good booster effect (to 150—600 mIU/ml) in only 5 (8%).

Sera from an outbreak of acute respiratory illness in a boys boarding school originally thought to have been due to psittacosis (1) have been re-examined and evidence is presented that suggests that the outbreak was caused by Chlamydia pneumoniae, strain TWAR (2).