Yersinia enterocolitica biotype 1, serotype O.10K was isolated from 19 patients in the paediatric wards of a district general hospital over a period of 3 months. Fifteen cases were patients on the medical ward. Shortly afterwards. Y. enterocolitica biotype 1, serotype 0.6,30 was isolated from a further 17 patients on this ward in 1 month. The same serotypes of Y. enterocolitica were isolated from the pasteurized milk supplied to the ward. Epidemiological evidence indicated that contaminated pasteurized milk was the source of the yersinia organisms exereted by the patients.

Pasteurized bottled milk supplied by a single dairy was frequently found to be contaminated with Yersinia spp. Investigations were carried out at the dairy in an effort to pinpoint the source of these organisms. Viable counts obtained from milk bottle rinses indicated that bottle washing was often unsatisfactory, and on one occasion Y. frederiksenii was isolated from the pooled rinse water of six bottles. Samples of milk were taken on arrival at the dairy and at various stages following pasteurization. Heat resistance tests carried out on strains of yersinia isolated from pasteurized milk indicated that they would not survive the pasteurization process. However two strains of yersinia were isolated from a sample of milk taken immediately after pasteurization but before bottling. The thermograph indicated that the time/temperature conditions applied during pasteurization were adequate. The presence of yersinia strains in the milk at this stage therefore suggests that undetectable levels of raw milk were being allowed to contaminate the pasteurized milk. The absence of yersinia in cartoned samples produced on the same day as contaminated bottled samples indicated that environmental contamination of the bottle filler valve also may have occurred at times. Results of this investigation indicate that increased vigilance is required to ensure proper operation of pasteurizers and bottle washers.

A large outbreak of Legionnaires’ disease was associated with Stafford District General Hospital. A total of 68 confirmed cases was treated in hospital and 22 of these patients died. A further 35 patients, 14 of whom were treated at home, were suspected cases of Legionnaires’ disease. All these patients had visited the hospital during April 1985. Epidemiological investigations demonstrated that there had been a high risk of acquiring the disease in the out patient department (OPD), but no risk in other parts of the hospital. The epidemic strain of Legionella pneumophila, serogroup 1, subgroup Pontiac la was isolated from the cooling water system of one of the air conditioning plants. This plant served several departments of the hospital including the OPD. The water in the cooling tower and a chiller unit which cooled the air entering the OPD were contaminated with legionellae. Bacteriological and engineering investigations showed how the chiller unit could have been contaminated and how an aerosol containing legionellae could have been generated in the U–trap below the chiller unit. These results, together with the epidemiological evidence, suggest that the chiller unit was most likely to have been the major source of the outbreak.

Nearly one third of hospital staff had legionella antibodies. These staff were likely to have worked in areas of the hospital ventilated by the contaminated air conditioning plant, but not necessarily the OPD. There was evidence that a small proportion of these staff had a mild legionellosis and that these ‘influenza–like’ illnesses had been spread over a 5–month period. A possible explanation of this finding is that small amounts of aerosol from cooling tower sources could have entered the air–intake and been distributed throughout the areas of the hospital served by this ventilation system. Legionellae, subsequently found to be of the epidemic strain, had been found in the cooling tower pond in November 1984 and thus it is possible that staff were exposed to low doses of contaminated aerosol over several months.

Control measures are described, but it was later apparent that the outbreak had ended before these interventions were introduced. The investigations revealed faults in the design of the ventilation system.

The colonization, survival and control of Legionella pneumophila in a hospital hot–water system was examined. The organism was consistently isolated from calorifier drain–water samples at temperatures of 50°C or below, despite previous chlorination of the system. When the temperature of one of two linked calorifiers was raised to 60°C, by closing off the cold–water feed, the legionella count decreased from c. 104 c.f.u./l to an undetectable level. However, 10 min after turning on the cold–water feed which produced a fall in calorifier temperature, the count in the calorifier drain water returned to its original level. Investigations revealed that the cold–water supply was continually feeding the calorifiers with L. pneumophila. Simple modifications in the design of the system were made so that the cold–water feed no longer exceeds 20°C; these measures have considerably reduced the number of L. pneumophila reaching the calorifiers.

The largest recorded outbreak of foodborne botulism in the United Kingdom occurred in June 1989. A total of 27 patients was affected; one patient died. Twenty-five of the patients had eaten one brand of hazelnut yoghurt in the week before the onset of symptoms. This yoghurt contained hazelnut conserve sweetened with aspartame rather than sugar. Clostridium botulinum type B toxin was detected in a blown can of hazelnut conserve, opened and unopened cartons of hazelnut yoghurt, and one faecal specimen. Cl. botulinum type B was subsequently cultured from both opened and unopened cartons of the hazelnut yoghurt and from one faecal specimen. Investigations indicated that the processing of the conserve was inadequate to destroy Cl. botulinum spores. Control measures included the cessation of all yoghurt production by the implicated producer, the withdrawal of the firm's yoghurts from sale, the recall of cans of the hazelnut conserve, and advice to the general public to avoid the consumption of all hazelnut yoghurts.

Infant mice were used for the evaluation of the efficacy of bismuth subaslicylate (BSS) in the prevention the growth of Campylobacter jejuni in the intestine. The MIC90 of ten C. jejuni strains was 900 μg/ml. Of three dosage regimens tested, continuous treatment before and after the bacterial challenge, mimicking the way BSS is used in the prevention of traveller's diarrhoea, was the most effective. Growth inhibition was dose dependent; the high dose of 2000 μg per day was more effective than 300 μg per day. After cessation of treatment, campylobacter counts increased to the same level as in the control animals.

A new scheme for phagetyping campylobacters has been evaluated using strains isolated from five outbreaks. The phagetyping results have been compared with the results of Penner serotyping, Lior serotyping and Preston biotyping. Phagetyping recognized the causative strains in all of the incidents and also differentiated these strains from animal and environmental strains isolated during these investigations. In some outbreaks phagetyping proved to be more discriminatory than serotyping or biotyping, e.g. strains of Penner serotype 2, and serogroup 4, 13, 16, 50 were subdivided by this method. Phagetyping is to be recommended for typing strains from outbreaks and although the results indicate that it may be used alone we advocate that it should be used in conjunction with one of the established typing methods.

Chickens given orally at 4 days of age a smooth spectinomycin resistant mutant (Spcr) of Salmonella typhimurium strain F98 excreted the organism in their faeces for approximately 4 weeks. Following oral administration of a nalidixic acid resistant (Nalr) mutant of the same strain 4 weeks later when later when the chickens had virtually cleared themselves of the first infection, these chickens excreted far fewer salmonella organisms and for a shorter time than did a previously uninfected control group of chickens which were infected at the same time with the Nalr mutant. Chickens inoculated intramuscularly at 4 days developed a similar immunity to challenge and also excreted the immunizing strain in their faeces. In contrast intramuscular inoculation or incorporation into the food of formalin-killed S. typhimurium organisms had little lasting effect on the faecal excretion of the challenge strain. Two attenuated mutants of strain F98 Nalr were produced: one was a rough strain produced by lytic bacteriophage and the other was an aro A auxotrophic mutant which had been cured of the 85 kilobase–pair virulence–associated plasmid. These mutants were avirulent for chickens, mice, calves and man and when ingested by human volunteers did not persist in the faeces. When inoculated intramuscularly into chickens they produced an early reduction in faecal excretion of the challenge strain (Spcr) which was not maintained. Oral administration of both strains produced reductions in faecal excretion of the challenge strain. This was much more noticeable with the rough strain which was itself excreted for a much longer period than the parent strain.

Oral administration to newly hatched chickens or to chicks up to 5 days of age with an avirulent, rough, spectinomycin–resistant mutant of Salmonella typhimurium strain F98 inhibited the colonization of a nalidixic acid–resistant mutant of the same strain administered by the same route 1 day later. The second strain passed rapidly through the alimentary tract and persisted in the caeca of only a few chickens. Resistance to colonization did not develop until 24 h after inoculation of the first strain but was still evident if the second strain was inoculated up to 7 days later. Resistance occurred in 5 different breeds of chicken and in chickens reared on 5 different diets. Protection was evident against a very high challenge dose and could be produced by the introduction of small numbers of the first strain. Pre–colonization of chicks with the first strain of F98 reduced faecal excretion of the second strain over many weeks, whether chickens were challenged directly or by contact with other infected chickens. The rough strain F98 produced protection against only a few S. typhimurium strains and not against other serotypes. However, strains of S. infantis and S. heidelberg, chosen because they colonized the chicken alimentary tract better than did F98, produced inhibition of a wider range of serotypes.

A quantitative carbon source growth assay, comprising ten carbon sources, was used to compare acinetobacter strains from three hospitals. The strains had been obtained during episodes of increased prevalence of isolations and were, for each hospital, assumed to be epidemiologically related. This assumption was supported by the electrophoretic protein profiles of the strains. Univariate analysis of growth data showed significant differences between strains from the three hospitals. Moreover, cluster analysis revealed that the major pattern in the data was related to the epidemiological origin of the strains. Exceptions to the epidemic-related pattern were observed. Thus, apart from epidemiological factors, other factors might contribute to carbon source growth profiles of the strains. It is concluded that the carbon growth assay may be useful to distinguish roughly between acinetobacter strains from different sites of origin. Further studies are required to analyse additional factors which influence carbon source growth of strains.

Twenty–four cultures comprising 20 clinical isolates of ‘Klebsiella aerogenes’ from two hospitals, a reference strain of ‘K. aerogenes’ and the type strains of three other Klebsiella species, were characterized by one–dimensional sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) 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 12 protein types. Comparison with established typing methods indicated that the level of discrimination of SDS–PAGE was similar to that achieved with conventional typing methods but the strains were grouped differently. Protein typing sub–divided five serotype K3 isolates that could also be distinguished by phage typing. Conversely, three strains of protein type 11 were clearly distinguishable by both serotyping and phage typing. We conclude that high–resolution SDS–PAGE of proteins provides an effective adjunct to other methods for typing isolates of ‘K. aerogenes’.

Five cases of clinical Q fever were identified amongst students and staff of a Somerset secondary school between 23 October 1987 and 21 December 1987. Five goats which were kept at the school were found to have antibodies to Coxiella burnetii phase II.

A cross-sectional study was conducted at the school in July 1988. A single CF test was used to identify evidence of prior infection, and a self-administered questionnaire was used to collect data on exposure variables and illness during 1987.

Four hundred and ninety-nine eligible subjects took part in the study, and serological information was obtained from 461 of these. Eighty-seven subjects (18·9%) had CF titres of 20 or greater. It was estimated that only 1 in every 30 individuals with evidence of past C. burnetii infection had been recognized as a clinical case of Q fever.

Antibody positive subjects were more likely to have been off school sick and to report having suffered chest pain than negative subjects.

Contact with school animals, specifically cleaning the school poultry, collecting their eggs and visiting a school goat on the day of kidding, was associated with the presence of antibodies to C. burnetii. However a large proportion of the antibody positives (24·2%) had no known contact with the school animals. Spread of organisms, either wind-borne or in straw or manure, may have been responsible for the high prevalence of unexplained infection.

Human respiratory tract chlamydial infections have been studied in Cambridge-shire for many years, but until recently we have been unable to distinguish between infection with Chlamydia psittaci Or Chlamydia pneumoniae (TWAR). In this study, we have employed the micro-immunofluorescence (micro-IF) test for this purpose and to look for the relative incidence of C. psittaci and C. pneumoniae infections in Cambridgeshire. Among 50 patients with community-acquired respiratory tract symptoms whose serum samples had Chlamydia complement fixation test titres ≥ 64, 25 had evidence of recent C. psittaci or C. pneumoniae infection. Nineteen (76%) of the 25 patients had evidence of recent C. psittaci infection and of these 16 (84%) had recently had contact with birds. Six patients (24%) had evidence of recent C. pneumoniae infection, and of these, only two (33% had recently had contact with birds). While C. psittaci was grown from several of the birds associated with human C. psittaci infection, it was not cultured from any of the birds in contact with the two human C. pnemoniae cases.

An IgM capture enzyme-linked immunosorbent assay for rubella-specific IgM was used to assess the avidity of specific IgM by comparing the results obtained with and without a mild protein denaturant in the washing fluid used after incubation of IgM with rubella haemagglutinating antigen. An avidity index (AI) was calculated with AIs < 50% considered to indicate low avidity. Sera from recent primary rubella, rubella reinfection and from patients persistently reactive for specific IgM were tested. Urea and diethylamine (DEA) were compared as the protein denaturants. Twenty-six of 28 sera from cases of primary rubella gave an AI < 50% with DEA, compared with 25 of 28 with urea. Seventeen of 20 sera from cases of reinfection gave an AI > 50% with DEA whereas only 14 of 20 had a similarly high avidity with urea. Eight of 10 sera from 4 cases of persistent specific IgM reactivity gave AIs > 50% with DEA, although this was reduced to 5 when urea was used. Thus a difference has been demonstrated between the avidity of specific IgM in primary infection from that demonstrated after a secondary antigenic challenge (reinfection). This may help in serologically distinguishing primary infection from reinfection.

One thousand three hundred and twenty adults at risk of occupational exposure to hepatitis B were immunized using genetically engineered surface antigen and their antibody response (anti-HBs IU/1) assessed. Sex was known for all subjects and age for 1120 (range from 17–71 years). Seven hundred and sixty-four subjects were immunized in the local Department of Occupational Health, the remainder mainly by general practitioners.

Analysis of ‘good responders’ (anti-HBs > 100 IU/1) according to age and sex showed that increasing age and male sex had independent adverse effects on the likelihood of developing a satisfactory level of antibody to HBsAg. Furthermore even those most likely to respond well (young women), had a 1/5 to 1/6 failure rate to achieve > 100 IU/1 anti-HBs.

Of 63 persons who received a fourth dose of vaccine, 26 developed anti-HBs titres > 100 IU/1 when tested after 6 months. Subjects who had a low level of anti-HBs following primary immunization were more likely to develop > 100 IU/1 anti-HBs following a booster dose than were non-responders (< 10 IU/1).

A population of 488 HBsAg carrier individuals, from central Italy, classified on the basis of biochemical, clinical and histological parameters, was analysed for the presence of HBV-DNA in serum and its relationship with HBeAg/anti-HBe markers. The prevalence of HBV-DNA was 32·8% in chronic patients with biopsy-proven liver disease, and 20 and 4·3% respectively in asymptomatic carriers with and without altered ALT levels. The values in chronic patients were correlated with the histological activity.

Concordance of HBV-DNA presence and HBeAg positivity was observed in only 61·4% of cases. However HBV-DNA prevalence in sera of anti-HBe positive individuals was very low in asymptomatic carriers with normal ALT levels (2·5%). Higher values were observed in anti-HBe positive chronic patients (15·8%) and in carriers occasionally found with changes in ALT without any other clinical sign of illness (16·7%). These data would indicate that HBV-DNA is the serological marker which is most closely related to liver disease.

The ability of three avian viruses to elicit antibody response in humans was surveyed for the purpose of identifying zoonotic diseases. Antibody levels in people associated with poultry were compared to those in people having limited poultry association. Antibody levels to three avian viruses: infectious bursal disease virus, a birnavirus; Newcastle disease virus, a paramyxovirus; and avian infectious bronchitis virus, a coronavirus were determined by enzyme–linked immunosorbent assays (ELISA). Differences between the two study groups were evident: people having a known association with poultry showed significantly higher levels of antibodies to Newcastle disease and avian infectious bronchitis virus. Antibodies detected may be due to virus exposure rather than zoonoses.