Since 1977, Vibrio cholerae O1 has been isolated from the Australian aquatic environment and periodically cholera cases have occurred following exposure to these environments. To study the relationships between clinical isolates and environmental isolates from rivers and aquatic life, widely distributed throughout the country, a wide range of molecular typing methods were employed. In this paper we report the analysis of the 180 Australian isolates (10 clinical and 170 environmental) using ribotyping. Seven ribotype patterns were observed among the Australian inaba isolates, 2 of which included all clinical inaba isolates and 84% environmental inaba isolates collected from 9 rivers and creeks in eastern Australia during an 8-year period. Isolates from epidemiologically related clinical cases, asymptomatic household contacts and sewage were indistinguishable. The ogawa isolates were more diverse, with 9 ribotypes observed among 24 isolates from 8 rivers during the same period. Ribotype patterns were not shared between the serotypes with the exception of one ogawa isolate which could be distinguished using PFGE. Ribotyping has been useful in confirming an association between epidemiologically related clinical isolates and the aquatic environment and the persistence of several clones of the O1 serovar in the Australian environment during an 8-year period.

For identification of lipopolysaccharide (LPS)-associated epitopes of Legionella pneumophila serogroup 1, LPS of strain Philadelphia 1 was investigated using monoclonal antibodies (MAbs). The O-specific chain of LPS is a homopolymer of 5-acetamidino-7-acetamido-8-O-acetyl-3,5,7,9-tetradeoxy-D-glycero-L-galacto-nonulosonic acid. At least four immunoaccessible epitopes were recognized by different MAbs on the intact LPS. After O-deacetylation of LPS, the reactivity of one of the MAbs (MAb 3/1) was lost, indicating thus that the corresponding epitope is associated with the 8-O-acetyl group. Since the reactivity pattern of the MAb 3/1 is identical with those of the MAb 2 which was considered as a virulence marker for serogroup 1, this epitope may be involved in mediating virulence in L. pneumophila. Four MAbs specific to strains of serogroup 1 other than the monoclonal subtype Philadelphia recognized epitopes on the O-deacetylated LPS of strain Philadelphia 1 and, therefore, the virulence-associated epitope blocks recognition of the immunodeterminants that are accessible on the intact LPS of the strains lacking this epitope.

An overview of serologieal and virological studies on poliomyelitis in the Netherlands between two epidemics in 1978 and 1992 is given. Three unvaccinated patients acquired poliomyelitis abroad. In the Netherlands vaccination coverage with quadruple DPT–IPV vaccine is very high. The strong immunogenicity of inactivated poliovirus vaccine was confirmed in a cohort of children, reflected in age-stratified antibody profiles of the population. Adults born in the pre vaccination era appeared in general protected, but 10–25% of persons born between 1930 and 1945 lacked neutralizing antibodies. Revaccination induced a booster type of antibody response in 75–90% of such persons, indicating immunological memory and protection.

Virological studies on adopted children from other countries, patients with indications for viral examination, and river waters showed that the Netherlands was regularly exposed to polio virus (PV), without signs of indigenous transmission. Persons found to carry PV or their close contacts had travelled to a PV endemic country. Most of 557 isolates were vaccine-derived, only 8% were wild type viruses. Despite their presence, up to 1992 the well-known susceptibles for PV in the Netherlands were shielded by the herd immunity of the Dutch population.

After instituting laboratory screening for Escherichia coli O157. H7, a Connecticut hospital isolated the organism from four persons in September 1993. As a result, an outbreak of E. coli O157.H7 associated with a country club was detected. The club had served hamburger from the same shipment at two picnics. Attendees of two picnics were interviewed, stool cultures were obtained from symptomatic persons, and the remaining hamburger was cultured. Twenty (22%) of 89 persons who ate hamburger became ill, compared with 1 of 60 who did not eat hamburger (relative risk = 13·5, 95% confidence interval 3·2–56·3). Among persons who ate hamburgers, illness was strongly associated with eating hamburger that was not thoroughly cooked (P < 0·001). All 20 samples from 5 remaining boxes of patties yielded E. coli O157.H7. Isolates from hamburger and case-patients were indistinguishable by pulsed-field gel electrophoresis. Heightened surveillance can rapidly identify outbreaks and may mitigate their impact. However, continued review of food safety issues is necessary if E. coli O157.H7 outbreaks are to be prevented.

Specimens from 181 patients with diarrhoea were examined by a Military General Hospital in a 3-month period during deployment of troops to Saudi Arabia in 1990/1. DNA probes for heat labile (LT) and heat stable (ST) enterotoxin genes identified enterotoxigenic Escherichia coli (ETEC) in 47 of the specimens (26%) and 49 ETEC strains were isolated. The majority (55%) belonged to a novel ETEC serotype having the O-antigen 159 and a flagellar antigen designated as a provisional new type. They produced ST and the coli surface associated antigen (CS)6. Strains of serotype O6:H16 represented 22% of the ETEC examined. They produced ST, LT and CSS together with either CS1 or CS2. The remaining ETEC belonged to seven O:H serotypes. Overall, ST was the only enterotoxin gene identified in 73% of the ETEC and 67% of the strains expressed CS6 in the absence of other colonization antigens. Resistance to three or more antibiotics was observed in 53% of the ETEC, including most of the O159 strains.

The presence of Legionella spp. in the water of a Portuguese spa was ascertained during the spa season, between May and November. Simultaneously the prevalance of anti-legionella antibodies in people attending the spa was also investigated. The antibody titres of 172 randomly selected patients and 42 therapists were determined, and compared with a control group of 503 blood donors. Legionellae were present in the spa water at low concentrations, generally lower than 103 c.f.u./1. A total of 92 strains representing eight different species or serogroups were isolated; the predominant isolates belonged to Legionella pneumophila serogroup 6 and to L. londiniensis.

During the study, no clinical cases of Legionnaires' disease were observed, and the antibody titres were generally low in the groups studied. However, the antibody titres of the patients increased slightly during their stay at the spa, approaching the values for the therapists. Mean antibody titres in the groups related with the spa were significantly higher than those in the blood donors against five of the seven legionella antigens tested. The largest number of elevated antibody titres in the exposed groups were to the L. pneumophila sg 5 and sg 6 antigens.

Certain health risks have been associated with recreational exposure to faecally polluted water. Canoeing in certain South African waters is considered to be a high risk activity with regard to schistosomiasis. gastroenteritis and possibly hepatitis. In a cross-sectional study, a serosurvey was conducted amongst canoeists to ascertain whether or not they had a higher seroprevalence to hepatitis A virus. Norwalk virus and Schistosoma spp. than non-canoeists. In comparisons between the two groups, a significant association could not be demonstrated between canoeing and antibody response to hepatitis A and Norwalk viruses (P-values for age-adjusted χ2 were 0·083 and 0·219 respectively), but a significant association could be demonstrated between canoeing and the antibody response to Schistosoma spp. (P > 0·001: age-adjusted).

This survey defined the pattern of invasive Haemophilus influenzae infections during 1990–2 in six regions in England and Wales during the pre-vaccination era providing a baseline against which any changes in patterns of disease due to the introduction of the Haemophilus influenzae type b vaccination programme can be monitored. A total of 946 cases of invasive Haemophilus influenzae were recorded during the survey period of which almost 90 % were due to type b and most of the remainder were non-typeable. Type b infections occurred predominantly in children less than 5 years of age (88%) with the highest attack rate in male infants in the 6–11 month age group. Diagnostic category varied with both age and serotype; meningitis was the commonest presentation overall but pneumonia and bacteraemia were more common in adults and non-typeable isolates. Mortality was highest in neonates and the elderly (over 65 years of age) who were more likely to have an underlying predisposing condition than older children and adults. Children under 5 years of age had a higher case fatality rate for non-typeable than for type b infections. Ampicillin resistance was 15% and there were no cefotaxime resistant type b isolates.

Adhesion to HEp-2 cells has been shown to correlate with enteropathogenicity for Aeromonas species. Such adhesion is thought to reflect the ability of strains to adhere to human intestinal enterocytes, although HEp-2 cells are not of intestinal origin. In this study strains of Aeromonas veronii biotype sobria isolated from various sources were investigated in parallel assays for their ability to adhere to HEp-2 cells and to an intestinal cell line (Caco-2). Quantitative assays showed identical adhesion values were obtained with both cell lines. Adhesion was best when bacteria were grown at 22 °C compared with 37 °C and 7 °C. Some environmental isolates showed greater adhesion when grown at 7 °C than when grown at 37 °C. Filamentous structures on these strains are also optimally expressed under the above conditions (reported elsewhere). Mechanical shearing or trypsin treatment to remove surface structures from several adhesive strains grown at 22 °C decreased adhesion to cell lines by 50–80% providing further indirect evidence that filamentous adhesins may play a role in cell adhesion for this Aeromonas species.

In N'Djamena, capital of Chad, measles vaccination coverage of 12–23-month-old children fell from 61% in 1990 to 15% in 1993. A community survey of measles after an outbreak in 1993 showed that among children < 5 years of age, the mean monthly attack rate was 37 per 1000 (95% CI, 32–43) and the mean case fatality rate was 7·4%. Measles incidence was highest (77/1000/month) in children aged 9–11 months and fell among children > 3 years of age. Incidence rates were high (56/1000/month) among 6–8-month-old children, but only 3 deaths occurred in this age group. Measles vaccine efficacy, estimated by comparing attack rates in unvaccinated and vaccinated children, was 71 % (95% CI, 59–80%). Extrapolation of the results to the city population indicated that an estimated 19000 cases and > 1000 measles-associated deaths occurred in 1993. This preventable morbidity and mortality, in a city where coverage was formerly among the highest in Africa, shows the need for sustained global commitment to preventive health care.

During a large measles outbreak in Quebec City in 1989, two investigations conducted in parallel evaluated the relative risk of measles and measles vaccine effectiveness with respect to age at vaccination. The study was a school-based case-control study including 563 cases and 1126 classmate controls. The second was a cohort study of the siblings of school cases including 493 siblings aged between 1 and 19 years. The relative risks (RR) of measles were similar in both settings and the trend towards increased vaccine efficacy with increasing age at vaccination was highly significant (P < 0·001). Vaccine efficacy rose from 85% in children vaccinated at 12 months of age to ≥ 94% in those vaccinated at 15 months and older. Even for children vaccinated at or after 18 months of age. the RR of measles was reduced when compared with children vaccinated between 15 and 17 months of age (RR 0·61. CI 95% 0·33–1·15). Small changes in the timing of initial measles vaccination can have a major impact on vaccine efficacy.

In this study, the in vitro susceptibility of 209 campylobacter strains to the quinolones nalidixic acid, flumequine, ciprofloxacin, enrofloxacin, and to ampicillin, tetracycline and erythromycin was tested by the disk diffusion method. The strains were isolated from poultry abattoir effluent (DWA) and two sewage purification plants (SPA and SPB). Sewage purification plant SPA received mixed sewage, including that from a poultry abattoir, whereas SPB did not receive sewage from any meat-processing industry. The quinolone resistance of the DWA isolates ranged from 28% for enrofloxacin to 50% for nalidixic acid. The strains isolated from the sewage purification plants were more susceptible to the quinolones with a range of 11–18% quinolone resistance for SPB isolates to 17–33% quinolone resistance for SPA isolates. The susceptibility criteria as recommended by National Committee Clinical Laboratory Standards (USA) cannot readily be employed for campylobacter isolates. This investigation shows that the resistance of campylobacter bacteria is highest in the plant receiving sewage from a poultry slaughterhouse. Monitoring of antibiotic resistance of aquatic Campylobacter spp. is important, as surface waters are recognized as possible sources of infection.

The purpose of this study was to DNA fingerprint the majority (64 %) of isolates received at the Pertussis Reference Laboratory during the 1993 whooping cough epidemic by pulsed field gel electrophoresis of Xba I - generated restriction digests. Two DNA restriction patterns, types 1 and 3, predominated (40% and 23%. respectively, of 180 isolates) but type 2, identified in a previous study was notably absent. Twenty-one new DNA types occurred (24% of isolates), some being atypical as bands 155–230 kb were no longer conserved, but there was no statistically significant difference in their incidence in the upswing (June-September) compared to the downswing (October-December) phase of the epidemic. There was a relatively high proportion of new types, compared to type 1. at the peak (September). About 50% of isolates received were from the North Western Region, where 44% of isolates were DNA type 1. Whereas only 1 out of 10 isolates from Scotland were of this type, suggesting some geographic variation. Statistically significant findings included a higher proportion of isolates from female patients (P < 0·01), most marked in the 12–24 months age group (P < 0·05); a higher proportion of infants under 12 months requiring hospital admission compared to older children (P < 0·05); and a greater number of isolates from unvaccinated children (P < 0·01). Analysis of serotype according to four age groups (under 3 months, 3–12 months, 12–24 months and above 2 years) showed statistically significant differences (P < 0·05) with a noticeably lower proportion (38%) of serotype 1,3 in 3–12 months age group and higher prevalence (74%) of serotype 1,3 in the 12–24 months age group. There was no correlation between DNA type and serotype.

Twenty-seven isolates of Burholderia pseudomallei (formerly Pseudomonas pseudomallei) from ten patients with recurrent melioidosis were analysed by RAPD. In two cases RAPD patterns in recurrent isolates differed from the original isolates; one was considered a likely reinfection while the other may represent relapse from one of two strains initially infecting the patient. In two cases where a change in antibiotic resistance had occurred between original and relapse isolates, slight changes in RAPD patterns were found with one of the four primers used. In the other six cases the relapse was clearly due to the original strain re-emerging unchanged, with identical RAPD patterns with all four primers.

Mathematical models are potentially useful tools to aid in the design of control programmes for parasitic diseases. In this paper, a fully age structured epidemiological model of human schistosomiasis is developed and parameterized, and used to predict trends in infection prevalence, intensity and prevalence of heavy infections over age and time during several rounds of mass and age targeted treatment. The model is validated against data from a Schistosoma mansoni control programme in Kenya.

In this study the distribution of phenotypes of campylobacter strains in sewage and surface waters was investigated by subtyping and by speciation of isolates from various aquatic environments. These environments included two municipal sewage plants (SPA and SPB) and waste water from a poultry abattoir (WWA). Both the sewage plants SPA and SPB collected domestic and industrial waste, and SPA received drain water from WWA. SPB received no waste water from any meat-processing plant. The isolates were speciated by PCR and subtyped by PCR/RFLP based on the flagellin PCR products.

From all three reservoirs, no Campylobacter lari was isolated, and approximately 80% of the isolates could be identified as C. jejuni and the rest belonged to the C. coli species. The PCR/RFLP typing technique has a high discrimination level and was reproducible between two separate laboratories. The 182 isolates tested yielded 22 distinct Dde I profiles. The results indicate that strains with profiles found in poultry are also detectable in waste water presumed to be solely from domestic and human sources. In addition some strains were unique to the known poultry-related sources, suggesting that avian-specific strains, non-pathogenic to man, may exist in the environment. In contrast some strains were unique to human waste indicating the potential importance of non-poultry sources of infection. No seasonality was observed in the profile distribution. So, at least in the Netherlands, it is unlikely that infections caused by contaminated surface waters contribute to the seasonality of human campylobacteriosis.

In November and December 1992, an outbreak of waterborne cryptosporidiosis occurred in Bradford, a city in the North of England. In all 125 cases were involved, the majority of whom lived in part of the city which received its drinking water supply from a single water treatment works. A case control study demonstrated an association between illness and the consumption of tapwater from this source; those drinking large volumes being more likely to have been ill. Treated water from the defined source yielded cryptosporidial oocysts. Heavy rainfall was recorded in the catchment area of the reservoir supplying raw water to the treatment works, immediately prior to the probable time of infection, based on dates of onset of illness.

Examination of neck skin and caecal samples taken at a commercial processing plant from 15 randomly chosen poultry flocks showed that all flocks were contaminated initially with thermophilic Campylobacter spp., even in the apparent absence of caecal carriage. During processing, numbers of campylobacter on skin samples were reduced by between 10 and 1000-fold.

To improve hygiene control generally, chlorinated-water sprays were used to limit microbial contamination on equipment and working surfaces. In addition, chlorine concentrations in process water were increased and any unnecessary carcass contact surfaces in the processing plant were removed. When comparing flocks before and after the changes, it was found that numbers of campylobacter on packaged carcasses were significantly lower after the changes had been made (P 0·001). In practice, however, the reduction would be likely to have little impact on consumer exposure to campylobacter infection.

The susceptibility of laboratory reared Zimbabwean Amblyomma hebraeum and A. variegatum ticks to infection with geographically distinct Cowdria ruminantium strains was investigated by feeding both species simultaneously on individual sheep infected with one of the four strains (Crystal Springs [Zimbabwe], Ball 3 [South Africa]. Gardel [Guadeloupe] and Nigeria [Nigeria]). A. hebraeum ticks demonstrated a high susceptibility to infection with all four C. ruminantium strains. In comparison. A. variegatum were less susceptible to infection with the Crystal Springs and Ball 3 strains (P < 0·001), but showed a similar susceptibility to the Gardel and Nigeria strains. The differences in susceptibility of A. variegatum to infection with the four strains of C. ruminantium correlated with the origin of these strains. The consistently higher susceptibility of A. hebraeum ticks to infection with geographically different C. ruminantium strains may be one explanation for the observation that heartwater is a more serious problem where A. hebraeiun is the vector of the disease.

We report a marked increase in the rate of notifications of tuberculosis in young adults in the London Borough of Lambeth. Analysis of notifications made to the Proper Officer over a 10-year period showed that the age specific notification rate in the cohort aged 20–44 years increased from 30/100000 in 1983 to 51/100000 in 1992. Analysis of St. Thomas' Hospital laboratory records of patients seen between 1984 and 1991 from whom Mycobacterium tuberculosis was isolated showed an increase in the number of patients of African origin from five in the first half of the study period (1984–7) to 25 in the second half (1988–91): 21 of these 25 had immigrated into England within 4 years of their illness. This finding is being further investigated in a prospective study of ethnicity, travel history and date of immigration of Lambeth residents notified with tuberculosis.