This study determined the prevalence of the eaeA gene and its relationship to serotype and type of verotoxin produced in a collection of 432 verotoxigenic Escherichia coli (VTEC) obtained from the faeces of healthy cows and calves in a systematic random survey involving 80 dairy farms in Southwest Ontario. A PCR amplification procedure involving primer pairs which target the conserved central region of the O157:H7 eaeA. gene showed that 151 (35·2%) strains were positive for the eaeA gene. All isolates (9–21 for each O group) of O groups 5, 26, 69, 84, 103, 111, 145 and 157 were positive, whereas all isolates (7–34 for each O group) of O groups 113, 132, and 153 and serotype O156:NM (38 isolates) were negative for eaeA. Seventy-three percent of 130 isolates of eaeA-positive serotypes produced VT1 only compared with 20% of 253 isolates of eaeA-negative serotypes. We conclude that there is a strong association between certain O groups and the eaeA gene, that serotypes of eaeA-positive and eaeA-negative VTEC implicated in human and cattle disease are present at high frequency in the faeces of healthy cattle, that VT1 is more frequently associated with eaeA-positive than with eaeA-negative serogroups, and that the eaeA gene is more frequently found in VTEC from calves compared with VTEC from adult cattle.

In February 1992, an outbreak of cholera occurred among persons who had flown on a commercial airline flight from South America to Los Angeles. This study was conducted to determine the magnitude and the cause of the outbreak. Passengers were interviewed and laboratory specimens were collected to determine the magnitude of the outbreak. A case-control study was performed to determine the vehicle of infection. Seventy-five of the 336 passengers in the United States had cholera; 10 were hospitalized and one died. Cold seafood salad, served between Lima, Peru and Los Angeles, California, was the vehicle of infection (odds ratio, 11·6; 95% confidence interval, 3·3–44·5). This was the largest airline-associated outbreak of cholera ever reported and demonstrates the potential for airline-associated spread of cholera from epidemic areas to other parts of the world. Physicians should obtain a travel history and consider cholera in patients with diarrhoea who have travelled from cholera-affected countries. This outbreak also highlights the risks associated with eating cold foods prepared in cholera-affected countries.

Neisseria gonorrhoeae were collected from men attending out-patient clinics in Dubai. The susceptibility to a range of therapeutic antibiotics and their auxotype and serotype was determined. The plasmid content of all penicillinase-producing strains was also analysed. Thirty-six strains of N. gonorrhoeae were isolated from specimens collected from 79 patients over a 24-day period. Of the 36 isolates, 9 (25%) were penicillinase-producing N. gonorrhoeae (PPNG) and 15 (42%) were chromosomally resistant N. gonorrhoeae (CMRNG). CMRNG exhibited higher levels of resistance to cefuroxime, chloramphenicol, tetracycline and erythromycin than PPNG. All isolates were susceptible to ceftriaxone and spectinomycin. Three (8%) isolates showed reduced susceptibility (MIC, ≥ 0·25 mg/1) to ciprofloxacin. Six isolates of PPNG carried the 4·4 MD and three the 3·2 MD penicillinase encoding plasmid. The total gonococcal population was phenotypically diverse, with 12 serovars, 6 auxotypes and 21 A/S classes. Gonorrhoea was found to be a major cause of urethritis in Dubai and the strains exhibited high levels of resistance to penicillin.

Two common forms of invasive disease due to Haemophilus influenzae type b (Hib) are epiglottitis and meningitis. It is not known why some children develop epiglottitis and others meningitis. To examine the hypothesis that epiglottitis occurs in children who may have been previously exposed to Hib, and who would therefore exhibit a more vigorous antibody response in convalescence, we measured levels of antibody to Hib capsule in 92 children. Geometric mean convalescent-phase IgG, IgA, IgM and total antibody levels were significantly higher in 45 children with epiglottitis than in 47 with meningitis, even after adjustment for age differences (mean total antibody, 95% confidence intervals: meningitis 0·38, 0·34–0·43; epiglottitis: 2·25, 2·0–2·54 μg/ml). However, contrary to previous reports, a poor antibody response was only observed in a minority of children with meningitis; the antibody response of the majority was indistinguishable from that observed in children with epiglottitis.

Traditionally the enteric pathogen Yersinia enterocolitica has been differentiated into biogroups. Despite being considered as non-pathogenic, biogroup 1A isolates have constituted a sizeable fraction of strains from patients with gastroenteritis in many reports. To establish a potential clinical significance for biogroup 1A isolates of Y. enterocolitica, clinical disease in patients with gastroenteritis excreting such isolates was compared with symptoms among patients found infected with pathogenic biogroups. Clinical data and isolates of 66 patients from whom Y. enterocolitica had been isolated by direct plating were available for study. There was an association between patient age below 3 years and infection with ‘pathogenic’ Y. enterocolitica. The severity of gastroenteritis and other symptoms, however, did not depend on the biogroup, or the presence of the virulence plasmid in the yersinia strain isolated from the patients. Strains belonging to biogroup 1A of Y. enterocolitica showed two clusters of ribotypes, one of which encompassed most isolates recovered from humans, the other being associated with environmental isolates. This might indicate the existence of human-adapted and potentially pathogenic strains among biogroup 1A of Y. enterocolitica.

Digital image processing (DIP) of bacterial smears is a new method of analysing the composition of the gut microbial flora. This method provides the opportunity to compare and evaluate differences in the complex highly concentrated anaerobic fraction of gut microbial flora, based on micromorphological differences. There is ample evidence that this fraction can be characterized as related or unrelated to the host organism by its immunogenicity. In this study germfree ND2 mice were associated with either related (rodent) SPF microflora (SPF-MF) or unrelated human MF (HUM-MF). DIP analysis was performed on original SPF-MF and HUM-MF and on the faeces of ex-germfree mice 4 weeks after association. The micromorphological pattern of highly concentrated anaerobic bacteria in faeces of HUM-MF associated ex-germfree mice was significantly different from SPF-MF associated counterparts with regard to the scores for elongation (P < 0·01) and morphological variety (P < 0·05). Moreover, gross morphological variability was present between individual HUM-MF associated mice but not between individual SPF-MF associated animals. No differences were found between original SPF and HUM-MF. The data are discussed with regard to differences in the presence of (non-)immunogenic bacteria and the ability for related and unrelated flora to colonize the murine gut. This study provides evidence that murine host specificity of microbial flora may not only be reflected in the number of non-immunogenic bacteria but also in the micromorphological pattern of highly concentrated anaerobic bacteria in faeces measured by DIP analysis.

Genetic relationships amongst 115 mainly Australian isolates of Mycobacterium avium were assessed using multilocus enzyme electrophoresis (MEE). The isolates were divided into 58 electrophoretic types (ETs), with a mean genetic diversity of 0·29. Isolates from humans were closely related to but distinct from those cultured from birds, whilst some porcine isolates belonged to the same ETs as certain human isolates. Pulsed field gel electrophoresis (PFGE) was used to differentiate related isolates, and those from birds and some from other animals, including pigs, were distinguished from the human isolates. The results of MEE and PFGE suggested that certain strains of M. avium may be transmitted between birds and pigs, but there was no clear evidence of transmission to humans. The serovar of the M. avium isolates was not obviously related to their ET assignment or their PFGE type.

The effects of influenza A and B and RSV on mortality in England and Wales were assessed by regression analysis for the period 1975–90. Morbidity data from sentinel practices were used to calculate 4-weekly rates of aggregated upper respiratory tract infections (URTI); PHLS laboratory reports were used as indices of infection, and 4-weekly death rates from all causes, excluding childbirths, were used to study relationships with mortality. Deaths correlated strongly with influenza A and B reports, temperature, and interactions between aggregated URTI and temperature, and RSV outbreaks and temperature. Estimates of ‘seasonal’ 4-weekly mortality associated with URTI were made by substituting into primary regression models the mean of annual trough consultation rates for aggregated URTI and baseline values for RSV and influenza. Peak 4-weekly mortality associated with URTIs was estimated at c. 24000 and c. 28000 during combined influenza and RSV epidemics of 1975–6 and 1989–90 respectively. Secondary regression analysis was carried out with the estimated ‘seasonal’ 4-weekly deaths associated with URTI as dependant variable and laboratory data as regressors. Estimated excess mortality associated with influenza was considerable even during years without major epidemics. Overall during the 15 winters the estimated mortality associated with RSV was 60–80 % more than that associated with influenza. The modelling permits only a crude estimate of RSV associated mortality. None the less it suggests that RSV is an important cause of winter mortality.

The prevalence of antibody to measles virus in 759 children aged 11–18 years attending a secondary school in Cumbria was measured using a salivary IgG antibody capture assay. Serum IgG antibody levels were measured using a plaque reduction neutralization assay in subjects whose saliva was antibody negative. Vaccination histories were obtained from the child health computer and general practice records. A total of 662 pupils (87 % of those tested) had detectable measles-specific IgG in saliva. Of the remaining 97, 82 provided blood samples and 29 had serum neutralizing antibody levels above 200 mlU/ml. After adjusting for non-participation rates, the proportion considered non-immune (no IgG in saliva and ≤ 200 mlU/ml in serum) was 9 % overall, ranging from 6 % in vaccinated children to 20 % in unvaccinated children. Measles-mumps-rubella vaccine was given to 50 children of whom 38 provided post-vaccination serum and 32 saliva samples. Thirty (79 %) had a fourfold or greater rise in serum neutralizing antibody and 28 (88 %) developed IgG antibody in saliva. Half of the children considered non-immune by antibody testing would have been overlooked in a selective vaccination programme targeted at those without a history of prior vaccination. A programme targeted at all school children should substantially reduce the proportion non-immune since a primary or booster response was achieved in three quarters of previously vaccinated children with low antibody levels and in all unvaccinated children. While it is feasible to screen a school-sized population for immunity to measles relatively quickly using a salivary IgG assay, a simple inexpensive field assay would need to be developed before salivary screening and selective vaccination could substitute for universal vaccination of populations at risk of measles outbreaks. The salivary IgG assay provided a sensitive measure of a booster response to vaccination.

Complex hepatitis B (HBV) epidemiology makes it difficult to evaluate and compare effectiveness of different immunization policies. A method for doing so is presented using a mathematical model of HBV transmission dynamics which can represent universal infant and adolescent vaccination strategies and those targeted at genito-urinary (GU) clinic attenders and infants born to infectious mothers. Model structure, epidemiological underpinning, and parameterization, are described. Data from the UK National Survey of Sexual Attitudes and Lifestyles is used to define patterns of sexual activity and GU clinic attendance; data deficiencies are discussed, in particular that of UK seroprevalence of HBV markers stratified by age, sex, and risk factors. General model predictions of endemic HBV marker prevalence in homosexual and heterosexual populations seem consistent with published UK data. The simulations exhibit non-linearities in the impact of different vaccination strategies. Estimated number of carriers prevented per vaccine dose for each strategy provides a measure of costs and benefits, varying temporally over the course of a programme, and with level of vaccine coverage. Screening before vaccination markedly increases payback per dose in homosexuals but not in heterosexuals; mass infant vaccination gives the poorest effectiveness ratio and vaccination of infants after antenatal screening the best; in general, increasing vaccine coverage yields lower pay-back per dose. The model provides a useful framework for evaluating costs and benefits of immunization programmes, but for precise quantitative comparison more UK epidemiological data is urgently needed.

One thousand one hundred and sixty-one non-polio enterovirus strains, isolated during regular screening of Finnish sewage specimens, were analysed for serotype distribution seasonally through 20 years, and the findings were compared with similar data based on 1681 clinical isolates. Coxsackievirus B4 (CBV-4), CBV-5, echovirus 11 (EV-11), EV-6, CBV-2 and CBV-3 were the most common serotypes in sewage, whilst CBV-5, EV-11, coxsackievirus A9, EV-22, CBV-3 and EV-30 were the most common clinical isolates. Reasons for the differences are not known but several explanations are possible. Seasonal variation of enterovirus occurrence in both sources showed an expected peak in the autumn with a trough in the spring. The occurrence of enteroviruses was closely correlated with monthly recordings of mean relative humidity. A further observation concerning the clinical specimens in Finland was the relative excess of some serotypes, such as echovirus 22 and coxsackievirus A9, and paucity of others, for instance, echoviruses 4 and 9, when compared to published data from other countries. This is consistent with the idea of geographically restricted circulation of enteroviruses.