An outbreak of Salmonella enterica serotype Typhimurium belonging to phage type (PT) 193 occurred in autumn 1995 and involved 83 individuals in a large area of Northern Italy (Lombardy Region). Epidemiological and microbiological investigations of strains isolated from clinical and food specimens revealed that the vehicle was a batch of salami, produced on 4 September 1995 by a local firm. The outbreak was contained when the batch was withdrawn from sale. Insufficient ripening of the salami had allowed the salmonella to survive, emphasizing the need to define criteria for the ripening process of foods such as salami.

A collection of Salmonella enterica serotype Typhimurium human strains isolated in Northern Sardinia (Italy) was examined for the insertion sequence IS200, phage type, antibiotic profile, ribotyping polymorphisms and plasmid profile. All clinical isolates studied contained from 4 to 10 copies of the IS200 element. IS200 permitted to discriminate Typhimurium strains and to identify five IS200 types, some of them circulating in Sardinia at least since 1900. Strains belonging to phage DT104 predominated and correlated with a specific IS200 pattern.

Salmonella enterica serotype Enteritidis isolates of phage types (PTs) PT1, PT4, PT13a and PT22 derived from sporadic cases and outbreaks of food poisoning in Japan during 1994 and 1995 were analysed by pulsed-field gel electrophoresis (PFGE). While PT1 strains from 5 different outbreaks showed 14 PFGE patterns, 5 PFGE patterns were observed among PT4 isolates from 5 different outbreaks and 6 independent isolates from imported chicken. Interestingly, 8 out of 9 PT4 strains associated with foreign travel to Southeast Asia were indistinguishable in PFGE pattern from 5 independent isolates of imported chicken from England. Although both PT13a and PT22 were first reported in Japan in 1994, PT22 showed various PFGE patterns compared to PT13a which had the same pattern within an outbreak, unlike PT1. These results could indicate that multiple clonal lines of PT1 and PT22 had already spread while relatively fewer clonal lines of PT4 and PT13a might exist in Japan.

We describe here an examination of the validity of molecular types of Campylobacter jejuni as defined by separation of SmaI-digested DNA using pulsed-field gel electrophoresis (PFGE), recently suggested as part of a molecular subtyping scheme. Thirty-four Danish strains from humans, water, poultry and cattle were assigned to one of six SmaI ‘profile groups’ (PGs), with two additional strains included as genotypically distinct controls. The interstrain relationships were reexamined by PFGE of SalI, KpnI and BamHI-digested DNA, and also by serotyping with heat-stable antigens. All outbreak-related strains were indistinguishable by all criteria, as were two sets of two randomly-isolated human strains. Two groups of indistinguishable isolates contained randomly isolated strains from more than one source (poultry, humans and/or cattle), a finding with significant epidemiological connotations. All ‘genetically identical’ strains belonged to the same serotype, whereas genetic differences were detected between strains assigned to the same SmaI PG but differing in serotype. We conclude that PFGE-based genetic fingerprinting can yield invaluable data for epidemiological studies of sporadic C. jejuni infection, but that results based on one restriction site polymorphism must be checked with another enzyme.

Certain strains of verotoxigenic Escherichia coli (VTEC), and in particular those belonging to serogroup O157, cause attaching and effacing (AE) lesions of the host gut mucosa during pathogenesis. The mechanisms involved with bacterial attachment and the destruction of microvilli are determined by a cluster of genes within the LEE region, which also encode five secreted proteins. Sera from patients with antibodies to the lipopolysaccharide (LPS) of E. coli O157 and other VTEC were tested for antibodies to these secreted proteins. Twenty-one of 34 (62%) sera with antibodies to the lipopolysaccharide (LPS) of E. coli O157 also contained antibodies to one or more of the secreted proteins. Five of 12 sera containing antibodies to the LPS of a range of other VTEC serogroups also contained antibodies to 1 or more of the 5 secreted proteins, as did 16 of 70 (23%) sera from patients with haemolytic uraemic syndrome (HUS), haemorrhagic colitis (HC) or diarrhoea, but without bacteriological evidence of infection with VTEC and which did not contain antibodies to VTEC serogroups O5, O115, O145, O153 or O157. The detection of serum antibodies to secreted proteins may provide additional information for interpreting the results of established lipopolysaccharide-based VTEC serology.

The prevalence of Clostridium botulinum type E gene in fish and fishery products of commercial importance in Finland was determined using a quantitative PCR analysis. The contamination level in 438 raw fish samples from intestines, surface and whole fish and 208 fish roe samples varied from 10–40% and from 4–14% respectively, depending on the fish species studied. The presence of C. botulinum in European wild freshwater fish and roe was demonstrated for the first time by isolation of the organism from PCR-positive samples. Five percent of 214 vacuum-packed and 3% of 123 air-packed fishery product samples examined at retail level were positive for the botulinum neurotoxin type E gene. A contamination level of 10% in vacuum-packed hot-smoked whitefish was detected. The results demonstrate that C. botulinum type E poses a serious health risk for those consuming fishery products from the Baltic Sea area.

Between March and May 1996 Stenotrophomonas maltophilia was cultured from endotracheal aspirate samples from five preterm infants in a neonatal intensive care unit (NICU). Four infants were superficially colonized, but a fifth died due to S. maltophilia septicaemia. S. maltophilia was cultured from tap water from three outlets in the NICU including one with a previously unnoticed defective sink drain. Water from these outlets was used to wash the preterm infants. Environmental and clinical S. maltophilia isolates yielded identical banding patterns on random arbitrary polymorphic DNA (RAPD) PCR analysis. The outbreak was controlled by reinforcement of hand disinfection, limitation of the use of tap water for hand washing and by using sterile water to wash the preterm infants. We conclude that tap water should not be used for washing preterm infants in the NICU, unless steps are taken to prevent microbial growth in the outlets.

Since 1992, the proportion of culture-confirmed meningococcal infections compared with numbers of notified cases of meningococcal disease has decreased in England and Wales. As most meningococcal strain characterization methods depend on a clinical isolate, this has resulted in a loss of epidemiological information. To address this problem, and to aid non-culture diagnosis, a semi-nested PCR protocol for the amplification of the meningococcal porB gene from clinical specimens was developed. This gene encodes the meningococcal serotyping antigen; strain typing data was provided by hybridization of allele-specific oligonucleotide probes to the digoxigenin-labelled porB amplicon in a ‘PCR ELISA’. This assay was specific for meningococcal DNA and sensitivities of 0·81 for cerebrospinal fluid (CSF), 0·57 for serum, and 0·62 for whole blood taken from patients with proven meningococcal infection were obtained.

Fourteen cases of meningococcal disease (MD) occurred in August–September 1996 in western Sydney, Australia. Seven of the 10 young adults affected had a direct or indirect link with a local nightclub. Ten of 11 systemic meningococcal isolates had the phenotype C[ratio ]2a[ratio ]P1.5 and showed close genetic relationship by pulsed-fleld gel electrophoresis (PFGE). Organisms of this phenotype have not previously caused outbreaks in Australia, but have been associated with outbreaks and hyperendemic serogroup C MD in Europe, Canada, and the United States.

This is the largest cluster of serogroup C MD reported in urban Australia, and the first involving a nightclub. The strain differentiation results were available rapidly enough to augment epidemiological investigations on a daily basis. Public health staff could thus establish links between cases quickly, follow the spread of new cases in the community, give accurate information to health officials and the press, and utilize existing knowledge about the characteristics of this phenotype to predict likely developments during the outbreak and afterwards. The strain differentiation data was also very helpful when the role of vaccination was considered, and existing guidelines on the management of outbreaks of MD could be used effectively for the first time in western Sydney.

Variation in the genomic location and copy number of the insertion element IS1181 in methicillin-resistant Staphylococcus aureus (MRSA) was investigated. Sixty-three isolates representing the Jevons type strain (NCTC 10442), phage-propagating strains, and epidemic strains were examined. A PCR amplicon of the insertion element was used to probe genomic restriction endonuclease digests. HindIII genomic digests gave 25 distinct IS1181 patterns, while EcoRI digests gave 20 patterns. EMRSA-01, -02, -04, -06, -07, -09, -10, -11, -13 and -14 contained the element but could not be subtyped by profiling it. EMRSA-16 did not contain IS1181, consistent with a unique evolutionary origin for this major UK epidemic strain. Marked heterogeneity was observed among isolates of EMRSA-03. Each EMRSA-03 strain examined gave a unique pattern, thereby allowing subtyping of an important epidemic phage type for the purposes of hospital cross-infection control.

A review of empirical studies and the development of a simple theoretical framework are used to explore the relationship between Haemophilus influenzae type b (Hib) carriage and disease within populations. The models emphasize the distinction between asymptomatic and symptomatic infection. Maximum likelihood methods are used to estimate parameter values of the models and to evaluate whether models of infection and disease are satisfactory. The low incidence of carriage suggests that persistence of infection is only compatible with the absence of acquired immunity to asymptomatic infection. The slight decline in carriage rates amongst adults is compatible with acquired immunity, but could be a consequence of reduced contacts. The low rate of disease observed in adulthood cannot be explained if protection from disease is a product of previous detectable exposure to Hib alone. We estimate an Ro of 3·3 for Hib in developed countries, which suggests that current immunization programmes may eliminate the infection. Analysis of the disease data set suggests the absence of maternal immunity and increased susceptibility to disease in the oldest age classes.

The study objective was to investigate prevalence and determinants of current Helicobacter pylori infection in an asymptomatic population of middle-aged to elderly people. A cross-sectional study was conducted among 337 participants of a general education programme of the University of Ulm aged 50–85 years. Prevalence of infection as determined by means of the [13C]urea breath test was 34·8% (95% CI 29·6–40·3%) ; overall, 33·8% (95% CI 23·0–46·0) in the age group 50–59 years, 32·4% (95% CI 25·4–39·9) in the age group 60–69 years and 41·0% (95% CI 30·0–52·7) in the age group 70–85 years. Duration of school education of the father, sharing a bed with parents or siblings during childhood, and the area in which participants had grown up were independent determinants of current infection status in a multivariable analysis. We conclude that the prevalence of current H. pylori infection in healthy elderly subjects may not be as high as seroprevalence studies have suggested. Socioeconomic characteristics of childhood living conditions appear to be important determinants of infection status even at older age.

Fifteen cohorts of healthy bathers were recruited at four Lake Leman beaches between 3 July and 23 August 1996 to assess the public health importance of cercarial dermatitis in Geneva, Switzerland. Telephone follow-up interviews were carried out after 2–7 days. Overall, 153 bathers out of 555 reported probable cercarial dermatitis at follow-up. Median daily attack rate was 27·7% (2·2–57·7%). Of the cases, 11·1% noticed more than 30 skin lesions, 19·6% described severe itching, 50·3% used a drug treatment, 3·9% visited a doctor and 15% claimed they would reduce their bathing activities. History of cercarial dermatitis, time spent in the water, hour of the day, barometric pressure and maximum daily atmospheric temperature predicted disease occurrence in multivariate analysis. While a benign disease, cercarial dermatitis may have a negative impact on the local water recreation industry. The identification of risk factors for the disease may help produce better preventive recommendations for the bathers.

Rubella infections, notified by general practitioners on the basis of a clinical diagnosis, were investigated by testing blood and saliva samples for specific IgM. Overall 52 (29%) of 178 cases with appropriately timed blood specimens were confirmed as recent rubella by IgM serology. Only 2 (3%) of 74 cases in children under 5 years were confirmed compared to 50 (48%) of 104 cases in older children and adults. The confirmation rate was lower (6 %) in those with documented vaccination history than in those without (42%). The specificity of saliva rubella IgM testing compared to testing corresponding blood samples was 99%. The overall sensitivity of saliva rubella IgM testing was 81%. This rose to 90% if results from inappropriately timed specimens and specimens taking more than 1 week to reach the laboratory were excluded. A corresponding saliva rubella IgG test was 98% sensitive and 100% specific. Of 126 rubella IgM negative cases, 25 (20%) were positive for parvovirus B19 IgM. This study confirmed that rubella surveillance based on clinical reports is not specific. It also demonstrated that saliva samples, if taken 7–42 days after onset of illness and transported rapidly to the laboratory, are a feasible alternative to blood samples for rubella surveillance.

Rotavirus gastroenteritis should soon be a vaccine-preventable disease. In a 10-year survey of rotavirus gastroenteritis conducted at the Prince of Wales Hospital (PWH), 2281 cases were detected of which 2213 (97%) occurred in children <5 years old. A consistent epidemic occurred each winter during the months of December and January. Of all laboratory-confirmed cases, 78% were community-acquired with a mean hospital stay of 4·7 days. The estimated incidence of rotavirus-attributed hospitalization was 2/1000 children <5 years old. Over the 10 years, rotavirus was responsible for one death, and contributory to three other deaths. On average each year, 195 children <5 years old were hospitalized for a total of 917 days in PWH, accounting for an estimated expenditure of HK$2·8 (∼US$0·4) million on hospitalization costs. The annual financial burden for rotavirus gastroenteritis for the whole of Hong Kong could be in excess of HK$9·6 (∼US$1·2) million.

Age-specific patterns of rotavirus infection were investigated using a randomly selected and representative sample of sera from a suburban community of São Paulo, Brazil screened for class-specific antibodies to group A rotavirus. Age-serology of anti-rotavirus IgG showed primary infection predominant in young infants with a median age of around 18 months consistent with IgM serology suggesting highest rates of recent infection between ages 4 and 48 months. Anti-rotavirus serum IgA prevalence increased gradually with age. Paired samples from infants, collected 1 month apart, indicated high exposure rates with seroconversion occurring in several infants during the reported low transmission season. Between 5 and 10% of adults had elevated IgM levels indicative of recent infection and, potentially, of an important contribution adults may play to rotavirus transmission. Further understanding of the dynamics of rotavirus transmission within populations, at group and serotype level, would benefit the design and monitoring of future immunization programmes.