Three members of family A, who had diarrhoea on 20 October, lived on a small arable farm which had 10 cattle. Manure from the animals was used to fertilize the ground for growing potatoes which were then offered for retail sale, unwashed, directly from the farm. The mother from family B bought potatoes, which were covered with manure, from family A in early November and over the subsequent 10 days she became ill with diarrhoea and her daughter and son both became ill with bloody diarrhoea. The mother from family C visited family B while the daughter from the latter family was symptomatic; the mother developed diarrhoea several days later. The mother and two sons from family D visited family B while the son from the latter family was symptomatic; the first son developed bloody diarrhoea 6 days later which progressed to development of haemolytic-uraemic syndrome. Direct culture of faecal samples onto cefixime rhamnose sorbitol MacConkey agar failed to isolate E. coli O157 from any of the symptomatic patients, and direct culture onto cefixime tellurite sorbitol MacConkey agar isolated the organism from only one patient. In contrast, a combination of isolation of E. coli O157 by immunomagnetic separation and detection of E. coli O157-specific secretory IgA, suggested E. coli O157 infection in all eight symptomatic patients, but not in any of the family members who were not ill. Two children who excreted the organism for 60 and 89 days respectively were the only two patients who did not develop a secretory IgA response. E. coli O157 was not isolated from potatoes from the farm and faecal samples from the farm animals were not available for examination. The study illustrates the need to use the most sensitive methods available during the investigation and follow up of cases of E. coli O157 infection.

In a survey examining the causes of travellers' diarrhoea treated in Tokyo between July 1986 and December 1995, Aeromonas species were isolated from 1265 (5·5%) of 23215 travellers returning from developing countries. Aeromonas species were the fourth most frequent enteropathogen isolated, following enterotoxigenic E. coli (8·5%), Salmonella spp. (7·6%) and Plesiomonas shigelloides (5·6%). Aeromonas species were found in 1191 (5·6%) of 21257 patients with diarrhoea and in 74 (3·8%) of 1958 healthy individuals without diarrhoea. Mixed infection was observed in 512 (40·5%) cases. No significant difference in the prevalence of Aeromonas by year, season, age distributions, or sex was observed, but a slight difference was noted depending on the country where the travellers visited. Of the 1265 Aeromonas isolates, 893 strains (70·6%) were A. veronii biovar sobria, 330 (26·1%) were A. hydrophila, and 42 (3·3%) were A. caviae. The clinical symptoms of patients from whom Aeromonas species was isolated as the only potential enteric pathogen were almost similar, which were watery diarrhoea (about 60%), abdominal cramps (43%), fever (around 15%), and nausea or vomiting (13%). Although the severity of illness was milder than that of enterotoxigenic E. coli alone, these data suggest that Aeromonas species are important enteric pathogens in travellers' diarrhoea.

Consumers in the United States continue to eat raw or undercooked foods of animal origin despite public health warnings following several well-publicized outbreaks. We investigated an outbreak of Salmonella serotype Typhimurium infection in 158 patients in Wisconsin during the 1994 Christmas holiday period. To determine the vehicle and source of the outbreak, we conducted cohort and case-control studies, and environmental investigations in butcher shop A. Eating raw ground beef purchased from butcher shop A was the only item significantly associated with illness [cohort study: relative risk=5·8, 95% confidence interval (CI)=1·5–21·8; case control study: odds ratio=46·2, 95% CI=3·8–2751]. Inadequate cleaning and sanitization of the meat grinder in butcher shop A likely resulted in sustained contamination of ground beef during an 8-day interval. Consumer education, coupled with hazard reduction efforts at multiple stages in the food processing chain, will continue to play an important role in the control of foodborne illness.

Klebsiella infection has been considered to be an uncommon cause of meningitis. To determine its incidence and clinical features, we reviewed the microbiologic records of cerebrospinal fluid (CSF) and blood cultures and the medical records of patients with bacterial meningitis admitted between 1981 and 1995. Klebsiella meningitis was diagnosed in 79 patients with 83 episodes. All patients had klebsiella isolated from CSF and/or blood and typical symptoms and signs of acute bacterial meningitis. Of these, 74 were over 16 years of age and 2 of the 5 children were infants. There was an increased prevalence rate of klebsiella meningitis after 1986. Of the 83 episodes, only 9 occurred between 1981 and 1986, accounting for 7·8% of 115 cases with CSF and/or blood culture-proven acute bacterial meningitis, whereas in 1987–95, there were 74 episodes accounting for 17·7% of 419 bacteriologically proven cases. K. pneumoniae accounted for 69 episodes, K. oxytoca, 11 episodes and K. ozaenae, 3 episodes. Male gender, diabetes mellitus and liver cirrhosis were commonly associated with K. pneumoniae meningitis. Neurosurgical procedures were frequently associated with K. oxytoca meningitis. All three patients with K. ozaenae meningitis had a primary disease of the nasopharyngeal pathway. The mortality rate due to K. pneumoniae was 48·5%, K. oxytoca, 10% and K. ozaenae, 0%. In patients with K. pneumoniae meningitis, poor prognostic factors included age over 60 years, diabetes mellitus, bacteremia and severe neurological deficits on the first day of treatment.

During a cholera surveillance programme, Vibrio furnissii was isolated in late January and early February 1994 from stool samples collected from 14 persons of whom six had diarrhoea. The remaining eight persons were healthy family members or neighbours to cholera cases. No common source of infection was found. Strains isolated from stool samples each showed typical biochemical reactions of V. furnissii including gas production. Each isolate, except one, agglutinated O-antisera yielding a total of eight different serotypes. Most isolates were sensitive to 10 antibiotics tested, except to ampicillin and the vibriostatic agent O/129 (10 μg). Eight of 14 (57%) strains carried plasmids in the size range 2·6–88 kb, however, no correlation was found between antibiotic susceptibility patterns and plasmid content. Altogether, seven closely related HindIII ribotypes were observed among the 14 V. furnissii isolates studied. V. furnissii strains isolated from family members and other persons living close together often showed different ribotypes suggesting that the isolation was not associated with neighbourhood. Serotyping, plasmid profiling and ribotyping revealed a high strain diversity within V. furnissii, however, the importance of V. furnissii as an enteric pathogen remains to be elucidated.

Data on prevalence and determinants of Helicobacter pylori infection in well-defined populations are scarce. We investigated the prevalence and determinants of active H. pylori infection in a population of out-patients attending a general practitioner in Southern Germany. Infection status was determined by [13C]urea breath test. In addition, information on potential risk factors and medical history was collected.

Five hundred and one of the 531 eligible patients participated in the study (response rate of 94·4%). In total, 117 of the 501 patients had a positive [13C]urea breath test (23·4%). Prevalence of H. pylori infection increased with age from 10·8% (95% CI 5·7–18·1%) in the age group 15–29 years to 30·8% (95% CI 22·1–40·6%) in the age group 60–79 years and was 20·3%, 30·4% and 28·2% for the age groups 30–39, 40–49 and 50–59 years, respectively. Education and childhood living conditions, especially the number of siblings, were identified as additional independent determinants of infection.

The clinical and molecular epidemiology of glycopeptide-resistant Enterococcus faecium was investigated during an outbreak on a renal unit. Forty-nine patients were colonized or infected during a 15-month period. Sites of colonization included faeces, urine, intravenous (IV) catheter tips and wound swabs. Ten patients had infections, which included five bacteraemias and three episodes of peritonitis. Pulsed-field gel electrophoresis of 43 patient isolates of glycopeptide-resistant E. faecium identified seven strains during the first 7 months of the outbreak. Three of these strains affected five or more patients. One strain accounted for 17/43 isolates. Isolates that were possibly related to another renal unit strain were cultured from patients at two other Manchester hospitals. These isolates were epidemiologically-related, and may represent a single Manchester epidemic strain. Of five patients who had multiple isolates of glycopeptide-resistant E. faecium, three had isolates representing a single strain and two were colonized or infected by more than one strain.

In order to determine antibody levels against Streptococcus pneumoniae (pneumococcus) and Haemophilus influenzae type b (Hib) in a population of splenectomized subjects, 561 persons in a Danish county, splenectomized between 1984 and 1993 were identified. Two hundred and thirty-five were alive and 149 participated in the study. Each person donated a blood sample for antibody determination by ELISA. Though vaccine coverage among the 149 persons was 91% only 52% had ‘protective’ levels of pneumococcal antibodies. Despite recommendations for regular follow-up on pneumococcal antibody levels this had only been carried out in 4% of the subjects. Splenectomized subjects who needed pneumococcal revaccination were significantly more likely to have received their initial vaccination less than 14 days before or after splenectomy, as recommended, than those not requiring revaccination. Therefore, the timing of initial pneumococcal vaccination in relation to splenectomy seems to be important. All persons had Hib antibody levels higher than 0·15 μg/ml and 60% had levels higher than 1 μg/ml, which are the levels thought to provide short term and long term protection, respectively. In total, 37% of the 149 persons tested had pneumococcal and Hib antibody levels thought to correlate with protection from serious infections.

Glycopeptide resistance in enterococci is now a cause of clinical concern in the United States and Europe. However, details of vancomycin resistance in enterococci in Japan have been unknown. We measured minimum inhibitory concentrations (MICs) of various antimicrobial agents for a total of 218 clinical strains of enterococci isolated in our hospital in 1995–6 in addition to 15 strains with known genotypic markers of resistance. We also screened vancomycin resistance genes using a single step multiplex-PCR.

In clinical isolates, only two strains of Enterococcus gallinarum were of intermediate resistance to vancomycin (MIC, 8 μg/ml), while the others were all susceptible. Glycopeptides (vancomycin and teicoplanin) and streptogramins (RP 58500 and RPR 106972) showed potent antimicrobial effects for the isolates. In addition, ampicillin was also potent for Enterococcus faecalis, while ampicillin, minocycline and gentamicin were potent for Enterococcus avium. No vanA or vanB genes were detected, while vanC1 and vanC23 genes were detected from two and four strains, respectively. Our results suggest that incidence of VRE in Japan may be estimated as still very low at this time.

Many aspects of the natural history of tuberculosis are poorly understood. Though it is recognized that clinical tuberculosis may follow shortly after initial infection (‘primary’ disease), or many years thereafter through either endogenous reactivation or after reinfection, the relative importance of these mechanisms is often disputed. The issue is complicated by the fact that the risks of developing disease are age-dependent, and reflect infection risks which may change over time.

This paper estimates the age-dependent risks of developing tuberculosis using an age-structured deterministic model of the dynamics of tuberculous infection and disease in England and Wales since 1900. The work extends the classical studies of Sutherland and colleagues. The best estimates of the risks of developing ‘primary’ disease (within 5 years of initial infection) were approximately 4%, 9% and 14% for individuals infected at ages 0–10, 15 years and over 20 years respectively, and a previous infection appeared to impart little protection against (further) reinfection, but 16–41% protection against disease subsequent to reinfection for adolescents and adults. We also provide evidence that reinfection made an important contribution to tuberculous morbidity in the past, as (i) exclusion of exogenous disease from the model considerably worsened the fit to observed notification rates, and (ii) the dramatic decline in the risk of tuberculous infection from 1950 in England and Wales accelerated the decline in morbidity among all individuals, even among the older age groups with a high prevalence of tuberculous infection. We conclude that the risk of infection is the single most important factor affecting the magnitude of the tuberculous morbidity in a population, as it determines both the age pattern of initial infection (and hence the risk of developing disease) and the risk of reinfection.

The aim of this study, carried out in 1993, was to evaluate diphtheria immunity in Siena. Diphtheria antitoxin levels were measured by means of the immunoenzymatic test (ELISA) in serum samples of 602 apparently healthy subjects (239 males and 363 females) of all ages residing in Siena. According to widely used criteria, 6% of the total population were susceptible to diphtheria (antibody levels <0·01 IU/ml), 71% had basic protection (0·01–0·09 IU/ml) and 23% were fully protected ([ges ]0·1 IU/ml). The results suggested that a high proportion of young population had a protective level of immunity against diphtheria, that susceptibility increased with age and a smaller proportion of males (2·9%) than females (8·3%) were unprotected; this difference was statistically significant. Our results suggest that it may be useful to revaccinate adults with low levels of diphtheria toxoid so that the percentage that remains unprotected does not put the community at risk of an outbreak of diphtheria.

A simulation model was constructed to assess the relative costs and cost-effectiveness of different screening and vaccination strategies for dealing with hospital incidents of varicella exposure, compared with current policies, using data from published sources and a hospital survey. The mean number of incidents per hospital year was 3·9, and the mean annual cost of managing these incidents was £5170. Vaccination of all staff would reduce annual incidents to 2·2 at a net cost of £48900 per incident averted. Screening all staff for previous varicella, testing those who are uncertain or report no previous varicella, and vaccinating those who test negative for VZV antibodies, reduces annual incidents to 2·3 and gives net savings of £440 per incident averted. Sensitivity analyses do not greatly alter the ranking of the options. Some form of VZV vaccination strategy for health care workers may well prove a cost-effective use of health care resources.

The prevalence of hepatitis B virus markers in the adult Swedish population was investigated according to age, sex, origin and demographic stratum. Sera were collected from 3382 persons in 1990–1. The sera were selected on a statistical basis considered to be representative of the Swedish population from adults aged [les ]18 years. Two of the sera (0·06%) were found to be hepatitis B surface antigen positive. The two hepatitis B carriers were of non-Scandinavian origin as were (8·9%) of those tested. A total of 90 persons had a marker of previous, hepatitis B virus infection, i.e. antibodies against hepatitis B core antigen. Of these, 66 (2·0%) were of Scandinavian origin and 24 (18·1%) from highly endemic areas. The overall hepatitis B virus marker prevalence was 2·7%. The highest age-specific prevalence of hepatitis B markers in those of Scandinavian origin was in those born in 1939 and earlier. In this age-group, women had a significantly higher prevalence (3·6%) than males (1·9%). The lowest prevalence was found in those born in 1970 and later. No significant, age-related differences between younger or older persons, or between men and women, could be found in persons of non-Scandinavian origin. The results showed significant differences in exposure to hepatitis B virus among the indigenous population, compared with those of non-Scandinavian extraction. The results do not support the proposal to include hepatitis B vaccination in the Swedish immunization schedule.

An outbreak of gastroenteritis in the infant–toddler unit of a child care centre (CCC) in Pretoria, South Africa, was investigated for possible viral enteropathogens. Rotavirus was found in association with seven (70%) diarrhoeal episodes. Co-infection with rotavirus and human astrovirus (HAstV) was demonstrated in two of these episodes, and rotavirus, HAstV and enteric adenovirus (EAd) co-infection in another. Rotavirus occurred alone in four of the diarrhoeal episodes, while HAstV and EAd were each detected alone in one episode. Two HAstV and one rotavirus asymptomatic infection episodes also occurred. Overall, 8 of 10 children had rotavirus infections, of which 7 were symptomatic, 6 of 10 children had HAstV infections (4 symptomatic), and 2 of 10 children had EAd infection, both symptomatic. These results highlight the diversity of viral enteropathogens that may be associated with a diarrhoeal outbreak in a CCC and emphasize the need to investigate the possibility that multiple enteropathogens may simultaneously cause a single outbreak of diarrhoea.

A population-based case-control study to determine social and behavioural risk factors for Taenia solium cysticercosis in humans was carried out in a rural area, Shandong province, China. Forty-eight cases with cysticercosis were ascertained through a prevalence survey conducted among 7281 persons in 1993. For each case, four controls residing in the same village and matched for age and sex were randomly selected. Information regarding demographic, social and behavioural factors was collected during house visits through interviews and direct observation. Risk factors strongly associated with human cysticercosis included poor personal hygiene, being unable to recognize cysticerci-containing meat, poor pig-raising practices and a history of passing tapeworm proglottides. The results indicate that health education in combination with chemotherapy for taeniasis is required for the control of cysticercosis in humans.

We compared the prevalence of salmonella in faecal samples from finishing pigs and in feed samples from swine herds in North Carolina, USA. Farms were either finishing sites using all-in/all-out management of buildings in multiple-site systems (14 farms) or farrow-to-finish systems using continuous flow management of finishing barns (15 farms). The two groups of herds differed with respect to several management variables. Salmonella were isolated from 565 of 2288 (24·6%) faecal samples and from at least 1 faecal sample on 24 of 29 (83%) farms. Predominant serotypes were S. derby, S. typhimurium (including copenhagen), S. heidelberg, S. worthington and S. mbandaka. Fewer farrow-to-finish farms were detected as positive compared with all-in/all-out farms. Prevalence was lower for pigs raised on slotted floors compared with all other floor types, and was highest for pigs raised on dirt lots. Modern methods of raising pigs in multiple-site production systems, using all-in/all-out management of finishing pigs, appear to have no benefit in reducing the prevalence of salmonella compared with conventional farrow-to-finish systems.

Samples of rectal faeces were collected immediately after slaughter from 400 cattle each month for a 1-year period and from 1000 each of sheep, pigs and poultry over the same period. Samples were examined for Escherichia coli O157 by enrichment culture in buffered peptone water with vancomycin, cefixime and cefsulodin followed by immunomagnetic separation and culture of magnetic particles onto cefixime tellurite sorbitol MacConkey agar. E. coli O157 was isolated from 752 (15·7%) of 4800 cattle, 22 (2·2%) of 1000 sheep and from 4 (0·4%) of 1000 pigs, but not from any of 1000 chickens. Of the cattle sampled, 1840 (38·4%) were prime beef animals, 1661 (34·6%) were dairy animals being culled and the status could not be determined for the other 1299 (27%) animals. E. coli O157 was found in 246 (13·4%) of the 1840 beef cattle and 268 (16·1%) of the 1661 dairy cattle. The monthly prevalence of E. coli O157 in cattle was 4·8–36·8% and was at its highest in spring and late summer. Seventeen of the 22 isolates from sheep were also made over the summer period. All E. coli O157 isolates from sheep and 749 (99·6%) of the 752 E. coli O157 isolates from cattle were verocytotoxigenic as determined by Vero cell assay and DNA hybridization, eaeA gene positive, contained a 92 kb plasmid and were thus typical of strains causing infections in man. In contrast isolates from pigs were non-toxigenic, eaeA gene negative and did not contain a 92 kb plasmid and would, therefore, be unlikely to be a source of infection for man.

The persistence of Escherichia coli O157[ratio ]H7 in cattle and the farm environment was investigated on eight Ontario dairy farms positive for E. coli O157[ratio ]H7 in a longitudinal study commenced one year previously. Faecal samples from cows, calves, humans, cats, rodents, wild birds, a composite fly sample and numerous composite and individual environmental samples were cultured and tested for verotoxin-producing E. coli (VTEC). VTEC isolates were serotyped and E. coli O157[ratio ]H7 isolates were phage typed. E. coli O157[ratio ]H7 phage type 34 was isolated from one calf on each of two farms. The same phage type had been isolated on one of these farms 12 months earlier. Most E. coli O157[ratio ]H7-positive animals and farms became culture-negative within 2 and 3 months, respectively. E. coli O157[ratio ]H7 was not isolated from any environmental samples, although evidence of VTEC was found in composite samples from calf feeders (19·1%), calf barn surfaces (18%), cow feeders (14·9%), flies (12·5%), cow barn surfaces (11·3%), and individual milk filters (12·5%). VTEC belonging to 21 non-O157 serotypes were isolated from 24 cows (8·2%), 21 calves (18·3%), 2 cow feeder samples (3·0%), and 1 calf feeder sample (4·8%). Shedding of E. coli O157[ratio ]H7 by infected dairy cattle appears to be transient and persistence of E. coli O157[ratio ]H7 was not demonstrated from the farm environment sites tested.

Sixty-three Staphylococcus aureus isolates recovered from bovine sources in the USA and the Republic of Ireland were characterized by multilocus enzyme electrophoresis (MLEE), ribotyping, and random amplified polymorphic DNA polymerase chain reaction (RAPD–PCR) typing at two separate laboratories. The S. aureus isolates were assigned by MLEE to 10 electrophoretic types (ETs) (Index of Discrimination, D=0·779). In contrast, the same isolates were assigned to 13 ribotypes (D=0·888), and to 12 RAPD types (D=0·898). A common clone, ET3, of worldwide distribution, was represented by six distinct combinations of ribotypes and RAPD types. S. aureus clones recovered from cows in Ireland were also associated with mastitis in dairy cows in the USA. These findings are consistent with the hypothesis that only a few specialized clones of S. aureus are responsible for the majority of cases of bovine mastitis, and that these clones have a broad geographic distribution.

Human echinococcosis remains a very serious public health problem worldwide, although a decline in incidence has been observed in some endemic areas during the last decades. However, in some non-endemic areas an increase in new cases and new foci of animal echinococcosis were registered during the same time. In Dalmatia, a well known endemic area of hydatidosis in the most Mediterranean part of Croatia, from the mid-1950s until present a decrease of incidence of over 70% has been registered. Age, sex and occupational category specific incidence as well as lethality rate have remained the same as before. Migrations from rural to urban regions seem to be the most important parameter in the changing epidemiology of human hydatidosis in Dalmatia.