The effect of a community intervention programme of antibiotics and meningitis vaccine on pharyngeal carriage of Neisseria meningitidis was investigated. Carriage rates were determined in pupils at both secondary schools (ages 11–18 years) included in the community intervention programme and compared with two schools outside the area matched for socio-economic status. A total of 1869 pupils were studied 6 months after the programmes, and 2457 pupils after 11 months.

Six months after the programme was completed there was a 72% reduction in pharyngeal carriage of Neisseria meningitidis in pupils attending the schools in the intervention area compared with pupils in the control schools. After 11 months this difference persisted in the 11–14 age group but not in the 15–18 age group. No resistance to the antibiotics used in the programme was found.

A community intervention programme of antibiotics and vaccine for the control of meningococcal disease led to a long-term reduction in Neisseria meningitidis carriage in some age groups.

Meningococcal acquisition is a prerequisite for invasive disease. Three hundred and eleven male marine commando recruits were studied throughout 29 weeks of basic training to identify factors influencing meningococcal carriage and acquisition including troop number, season, smoking, respiratory infection, antibiotic usage and nasopharyngeal bacterial interference flora.

A high carriage rate on entry to training (118/311, 37·9%) and subsequent sustained high rates of meningococcal acquisition were found. Of the potential factors examined, only active and passive smoking were found to be associated significantly with meningococcal carriage on entry. The association between active smoking and meningococcal carriage was dose-dependent, with odds ratios (OR) of 2·2 (95% CIs 1·0–4·8) and 7·2 (95% CIs 2·3–22·9) for light and heavy smokers respectively. Passive smoking predisposed independently to carriage (OR 1·8, 95% CIs 1·1–3·0). Active and passive smoking combined to give an attributable risk for meningococcal carriage of 33%. In contrast, despite a high and sustained rate of meningococcal acquisition in the study population, none of the risk factors investigated, including active smoking, was associated significantly with meningococcal acquisition. No cases of meningococcal disease occurred during the 16-month study period. Therefore smoking may increase the duration of meningococcal carriage rather than the rate of acquisition, consistent with the increased risk of meningococcal disease from passive as opposed to active smoking. Public health measures that reduce the prevalence of smoking should reduce the risk of meningococcal disease.

In a comparative study, isolates of methicillin-resistant Staphylococcus aureus (MRSA) with known pulsed-field gel electrophoresis (PFGE) and bacteriophage type were analysed by polymerase chain reaction (PCR) and restriction fragment length polymorphisms (RFLP) for additional discriminatory subtyping information. PFGE was previously performed using standardized, commercially available kits and pre-programmed software. Isolates were examined for coagulase (coa) and protein A (spa) gene polymorphisms following PCR amplification of the coa hypervariable and spa repeat regions. Coa gene RFLPs produced a total of 38 distinct combined patterns after digestion with HaeIII and AluI and identified the predominant epidemic (EMRSA) types 15 and 16. A unique HaeIII restriction site was identified by RFLP and sequence analysis in the coa gene for EMRSA 15 but not EMRSA 16. The spa gene PCR yielded a total of 14 different profiles ranging from 3–18 repeats with the 2 predominant EMRSA types falling into 2 distinct groups. PCR detection of coa and spa polymorphisms offer a rapid preliminary strain identification and discriminatory subtyping information for surveillance of MRSA.

An increase in the incidence of invasive and non-invasive infections caused by group A β-haemolytic streptococci (GAS) was noted in and around the town of Glynneath (population approx. 4000) in West Glamorgan, South Wales between 1 January and 30 June 1995. A total of 133 cases was ascertained with 127 (96%) occurring between 1 March and 30 June 1995. Six patients had invasive disease (one died) and all presented at the peak of the outbreak. There were 127 non-invasive cases of whom 7 were hospitalized. The outbreak was investigated to determine its extent and whether it was caused by a single M-serotype of GAS. Serotyping showed that 13 different M-serotypes were involved with the M1 serotype predominating. The overall incidence of GAS invasive disease in West Glamorgan (population 365000) increased sevenfold from a crude incidence of 0·5/105 per year in 1994 to 3·5/105 per year in 1995, but fell back to 0·75/105 per year in 1996. Eighty-two (80%) out of 102 individuals affected by GAS replied to a health questionnaire; sore throat was the commonest symptom reported (97%). Thirty-nine of these index cases identified at least one other member of their household who had experienced similar symptoms. The interval between the onset of illness in members of a single household was 0·83 days with a mean of 22 days. The mean duration of illness was 13·5 days and 61% of patients were treated with penicillin V for a mean duration of 9·3 days. Twenty-one per cent of GAS isolates were erythromycin-resistant and the M4 and M6 serotypes were especially resistant to erythromycin (87·5 and 100% resistance, respectively). Penicillin V failed to eradicate GAS from the throats of 25% of assessable patients. In this community, an outbreak of non-invasive disease caused by GAS was linked in time and place with an outbreak of serious invasive disease.

Previous respiratory tract infections (RTI) and antibiotics consumption as possible risk factors for extended duration of PRP carriage were investigated in 24 children (cases) with previous carriage of penicillin-resistant pneumococci (PRP) for a duration exceeding 120 days (median 168 days) and a control group of 53 children with a duration of PRP carriage less than 90 days (median 21 days). The cases had experienced 0·99 episodes of acute otitis media (AOM) per life-year compared to 0·79 episodes in the controls (P=0·32). For antibiotic-treated RTI other than AOM, the corresponding numbers were 0·49 and 0·29 episodes per life-year, respectively (P=0·01). No differences in antibiotic consumption in the 3 months preceding the carriage, nor during the carriage period were noted. Other factors than impaired host defence to respiratory tract pathogens or antibiotics consumption seem to be more important in determining the duration of PRP carriage.

In recent decades, several epidemiological studies have been published on acute otitis media (AOM), indicating that the occurrence of AOM is increasing. However, the comparison between the surveys is complicated and biased by several factors, e.g. variable study demography and design and dissimilar diagnostic criteria. The present study was performed with an identical set-up in 1978–9 and 1994–5 to find out potential changes in the occurrence of AOM. All the attacks of AOM among children under 10 years diagnosed by a physician during the 12-month periods 1 June, 1978 to 31 May 1979 and 1 June 1994 to 31 May 1995 were registered retrospectively in two Finnish municipalities. The incidence rate (total number of AOM attacks per 100 child years) was 19 (95% CI 18–21) in 1978–9 and 32 (95% CI 30–34) in 1994–5. The increase in the occurrence of AOM was 68% (95% CI 53–79%, P<0·001).

The emergence of Vibrio cholerae O139 in 1992 and reports of an increasing number of other non-O1 serogroups being associated with diarrhoea, stimulated us to characterize V. cholerae non-O1 non-O139 strains received at the National Institute of Infectious Diseases, Japan for serotyping. Ribotyping with the restriction enzyme BglI of 103 epidemiological unrelated mainly clinical strains representing 10 O-serotypes yielded 67 different typing patterns. Ribotype similarity within each serotype was compared by using the Dice coefficient (Sd) and different levels of homogeneity were observed (serotypes O5, O41 and O17, Sd between 82 and 90%; serotypes O13 and O141 Sd of 72; and O2, O6, O7, O11, O24 Sd of 62–66%). By cluster analysis, the strains were divided into several clusters of low similarity suggesting a high level of genetic diversity. A low degree of similarity between serotypes and ribotypes was found as strains within a specific serotypes often did not cluster but clustered with strains from other serotypes. However, epidemiological unrelated O5 strains showed identical or closely related ribotypes suggesting that these strains have undergone few genetic changes and may correspond to a clonal line. Surprisingly, 10 of 16 O141 strains studied contained a cholera toxin (CT) gene, including 7 strains recovered from stool and water samples in the United States. This is to our knowledge the first report of CT-positive clinical O141 strains. The closely related ribotypes shown by eight CT-positive strains is disturbing and suggest that these strains may be of a clonal origin and have the potential to cause cholera-like disease. Despite the low degree of correlation found between ribotypes and serotypes, both methods appears to be valuable techniques in studying the epidemiology of emerging serotypes of V. cholerae.

The prevalence of campylobacter gastroenteritis has been estimated by bacterial isolation using selective culture. However, there is evidence that certain species and strains are not recovered on selective agars. We have therefore compared direct PCR assays of faecal samples with campylobacter culture, and explored the potential of PCR for simultaneous detection and identification to the species level. Two hundred unselected faecal samples from cases of acute gastroenteritis were cultured on modified charcoal cefoperazone deoxycholate agar and subjected to DNA extraction and PCR assay. Culture on CCDA indicated that 16 of the 200 samples contained ‘Campylobacter spp.’. By contrast, PCR assays detected campylobacters in 19 of the 200 samples, including 15 of the culture-positive samples, and further identified them as: C. jejuni (16), C. coli (2) and C. hyointestinalis (1). These results show that PCR offers a different perspective on the incidence and identity of campylobacters in human gastroenteritis.

The relative frequency of salmonella strains isolated from hospitalized and non-hospitalized patients in Southern Israel changed during the period, 1994–6. Salmonella enterica serotype Typhimurium definitive phage-type 104 (DT104) appeared in Israel in 1994 and became the most prevalent strain in 1996. An outbreak of enteritis due to Salmonella enterica serotype Agona occurred in Israel, in October 1994 and lasted for 4 months. The relative frequency of Salmonella enterica serotype Enteritidis remained almost constant during these years, with seasonal fluctuations only.

The importance of the increase in the prevalence of Typhimurium DT104 has been the epidemic spread of a multiresistant strain of R-type ACT (A, ampicillin; C, chloramphenicol; T, tetracycline) belonging to this phage-type. Since 1995 the frequency of Typhimurium DT104 isolates that possess, in addition to the above R-type, a chromosomally encoded resistance to the quinolone drug, nalidixic acid, increased tenfold. In 1996, 27% of the Typhimurium DT104 isolates were of R-type ACTN. S. Enteritidis exhibited over 95% susceptibility to at least eight of the most commonly used antibiotic drugs, and none of the isolates was resistant to quinolone or fluoroquinoline.

To determine risk factors associated with the occurrence of sporadic cases of Salmonella enteritidis infections among children in France, we conducted a matched case-control study. Cases were identified between 1 March and 30 September 1995. One hundred and five pairs of cases and controls matched for age and place of residence were interviewed. In the 1–5 years age group, illness was associated with the consumption of raw eggs or undercooked egg- containing foods (OR 2·4, 95% CI 1·2–4·8). Storing eggs more than 2 weeks after purchase was associated with Salmonella enteritidis infection (OR 3·8, 95% CI 1·4–10·2), particularly during the summer period (OR 6·0, 95% CI 1·3–26·8). Cases were more likely to report a case of diarrhoea in the household 10·3 days before the onset of symptoms, particularly in the age group [les ]1 year (P=0·01). This study confirms the link between eggs and the occurrence of sporadic cases of Salmonella enteritidis among children, highlights the potential role of prolonged egg storage and underlines the role of person-to-person transmission in infants.

The epidemiological progression of human salmonellosis in Norway is parallel to trends noted elsewhere in Europe. During the past two decades, the number of reported cases has increased steadily, with a special sharp rise in the early 1980s due to the emergence of Salmonella enteritidis, followed by a levelling off in recent years. However, in contrast to the situation in most other European countries, about 90% of the cases from whom a travel history is available, have acquired their infection abroad. The incidence of indigenous salmonella infections as well as the prevalence of the microorganism in the domestic food chain, are both comparatively low. In 1993–4, a national case-control study of sporadic indigenous salmonella infections was conducted to identify preventable risk factors and guide preventive efforts. Ninety-four case patients and 226 matched population controls were enrolled. The study failed to demonstrate any statistically significant association between salmonellosis and consumption of domestically produced red meat, poultry or eggs. The only factor which remained independently associated with an increased risk in conditional logistic regression analysis, was consumption of poultry purchased abroad during holiday visits to neighbouring countries. A separate analysis of Salmonella typhimurium infections incriminated food from catering establishments and foreign travel among household members, in addition to imported poultry.

One hundred and six Yersinia enterocolitica serogroup O[ratio ]3, biotype 4 isolated from human and porcine samples in 1984 and in the years 1993–5 were examined by pulsed-field gel electrophoresis (PFGE). The genomic profiles produced by the enzymes NotI and XbaI were studied. Sixteen (A–P) and 8 (1·8) different pulsotypes were obtained, respectively. By combining the pulsotypes produced by both NotI and XbaI 24 different types were distinguished. The two major types, designated as A1 and B1, comprised 36% of all strains tested. The proportions of pulsotypes A1 and B1 were, 35·9 and 25·6%, respectively, among strains isolated in 1984. The corresponding figures among the strains isolated in 1993–5 were 35·8 and 41·8%. Nine pulsotypes were found only in 1984 and nine only in 1993–5. The proportions of the major pulsotypes, A1 and B1, in human isolates were 42·9 and 35·7% and in porcine isolates 22·2 and 36·1% respectively. Six types were found among both human and porcine isolates, 8 only among human strains and 10 only among porcine strains.

The Escherichia coli flora of infants in developed countries is dominated by one or a few strains which persist for prolonged periods of time, but no longitudinal studies have been performed in developing countries. To this end, we studied the rectal enterobacterial flora in 22 home-delivered Pakistani infants during their first 6 months of life. Three colonies were isolated and species typed on each of 11 sampling occasions. E. coli isolates were strain typed using electromorphic typing of cytoplasmic enzymes, and their O serogroups were determined. There was a very rapid turnover of enterobacterial strains in the rectal flora of individual infants. On average, 8·5 different E. coli strains were found per infant, and several biotypes of other enterobacteria. Less than 50% of the infants were colonized with E. coli from their mothers, but strains of maternal origin were four times more likely to persists in the infants' flora than other E. coli strains. Enterobacteria other than E. coli were always of non-maternal origin, and Enterobacter cloacae and Klebsiella pneumoniae biotypes recovered from contaminated feeds were later identified in the infants' rectal flora. An early colonization with klebsiella or enterobacter was significantly associated with diarrhoea during the neonatal period, although these bacteria were not likely to be the cause of the disease. The results suggest that poor hygienic conditions result in an unstable and diverse enterobacterial flora, which may influence infant health.

Resident and transient Escherichia coli strains were identified in the rectal flora of 22 Pakistani infants followed from birth to 6 months of age. All strains were tested for O-antigen expression, adhesin specificity (P fimbriae, other mannose-resistant adhesins or type 1 fimbriae) and adherence to the colonic cell line HT-29. Resident strains displayed higher mannose- resistant adherence to HT-29 cells, and expressed P fimbriae (P=0·0036) as well as other mannose-resistant adhesins (P=0·012) more often than transient strains. In strains acquired during the first month of life, P fimbriae were 12 times more frequent in resident than in transient strains (P=0·0006). The O-antigen distribution did not differ between resident and transient strains, and none of the resident P-fimbriated strains belonged to previously recognized uropathogenic clones. The results suggest that adhesins mediating adherence to intestinal epithelial cells, especially P fimbriae, enhance the persistence of E. coli in the large intestine of infants.

To determine the occupational significance of tick-borne zoonoses we sought serological evidence of Lyme borreliosis, human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) in a representative sample of farmworkers. Although around 20% reported ticks on their domestic and companion animals, few (<2% per year) reported being bitten by ticks. Seroprevalence of Lyme borreliosis (0·2%), HME (0·2%) and HGE (1·5%) was low. Those seropositive for HGE were no more likely to report tick bites nor more likely to report ticks on their animals. This study provides evidence that farmworkers in England are exposed to tick-borne zoonoses but that they are uncommon. Since the severity of these diseases is linked to delays in diagnosis and treatment, clinicians should be aware of these diagnoses in patients from rural communities, with or without a self-reported history of tick bite.

Although food handlers are often implicated as the source of infection in outbreaks of food-borne viral gastroenteritis, little is known about the timing of infectivity in relation to illness. We investigated a gastroenteritis outbreak among employees of a manufacturing company and found an association (RR=14·1, 95% CI=2·0–97·3) between disease and eating sandwiches prepared by 6 food handlers, 1 of whom reported gastroenteritis which had subsided 4 days earlier. Norwalk-like viruses were detected by electron microscopy or reverse transcriptase-polymerase chain reaction (RT-PCR) in stool specimens from several company employees, the sick food handler whose specimen was obtained 10 days after resolution of illness, and an asymptomatic food handler. All RT-PCR product sequences were identical, suggesting a common source of infection. These data support observations from recent volunteer studies that current recommendations to exclude food handlers from work for 48–72 h after recovery from illness may not always prevent transmission of Norwalk-like viruses because virus can be shed up to 10 days after illness or while exhibiting no symptoms.

To assess the relative importance of ulcerative and non-ulcerative sexually transmitted disease in the transmission of HIV, a seroprevalence study was conducted on 2210 patients at the sexually transmitted diseases (STD) clinic of the S. Maria e S. Gallicano Hospital in Rome, between 1989 and 1994. Among male patients, by univariate analysis, strong predictors of HIV infection were homosexuality, sexual exposure to a HIV-positive partner, hepatitis B virus infection, and positive syphilis serology. An increased risk was estimated for patients with past genital herpes (odds ratio (OR) 3·86, 95% confidence intervals (CI) 0·40–18·2), and primary syphilis (OR 5·79, 95% CI 0·59–28·6). By multivariate analysis, a positive association was found with homosexuality (OR 6·9, 95% CI 2·9–16·5), and positive syphilis serology (OR 3·5, 95% CI 1·3–9·2). An adjusted OR of 2·41 was calculated for current and/or past genital herpes. These results, although not conclusive, suggest a role of ulcerative diseases as risk factors for prevalent HIV infection, and indicate that positive syphilis serology is an unbiased criterion for identifying individuals at increased risk of HIV infection.

Surveillance of hepatitis A in residents of Eastern Sydney Health Area identified substantial epidemics in homosexual males in 1991–2 with a peak rate of 520 per 100000 recorded in males aged 25–29 years, and again in 1995–6, with a peak rate of 405 per 100000 per year in males aged 30–34 years. During 1994–5 an epidemic was detected among disadvantaged youth associated with injecting drug use; peak rates of 200 per 100000 per year were reported in males aged 25–29 years and of 64 per 100000 per year among females aged 20–24 years. The epidemiology of hepatitis A in these inner suburbs of Sydney is characterized by very few childhood cases and recurrent epidemics among homosexual men. Identified risk groups need to be targeted with appropriate messages regarding the importance of hygiene and vaccination in preventing hepatitis A. However, poor access to health services among disadvantaged youth and a constant influx of young homosexual males into these inner suburbs present major challenges to hepatitis A control.

Mass vaccination can change the epidemiological dynamics of infectious diseases. It may result in a limited persistence of natural and vaccine-induced immunity and a higher mean age of infection, which may lead to a greater risk of complications. The epidemiological situation should be monitored and immunosurveillance based on the assessment of specific antibodies against vaccine-preventable diseases in human serum is one of the tools. In order to estimate the immunity of the Dutch population reliably, a large-scale, population-based, collection of serum samples was established (8359 sera in a nation-wide sampling and 1589 sera from municipalities with low vaccine coverage). In contrast to collecting residual sera from laboratories, this approach gains extensive information by means of a questionnaire regarding the determinants of the immune status and the risk factors for the transmission of infectious diseases in general. The population-based approach gives a better guarantee that the data are representative than collecting sera from laboratories does.

In 1989–91 anti-measles vaccination campaigns were conducted in several Italian regions to vaccinate all children aged between 13 months and 10–12 years without a history of measles or measles vaccination. This study was conducted to evaluate serological status after the mass vaccination campaigns. In 1994, capillary blood samples were collected from randomly selected children, aged 2–14 years, living in 13 local health units. Antibody titres were determined by ELISA. Blood spot samples were analysed for 4114 (75·6%) of 5440 selected children. Among the 835 that reported measles before 1990, 806 (96·5%) were immune and of the 2798 vaccinated, 2665 (95·2%) were immune. The Edmoston–Zagreb (E–Z) strain vaccine was associated with a lower level of immunity than the Schwarz (SW) strain. A history of measles identified almost all immune children. Vaccination with the SW strain conferred persistent immunity (at least 5 years) in 98% of vaccinees. The strategy was able to unite natural and induced immunity.