To determine risk factors for cholera in an epidemic-disease area in South America, a case–control investigation was performed in Guayaquil, Ecuador, in July 1991. Residents > 5 years old who were hospitalized for treatment of acute, watery diarrhoea and two matched controls for each were interviewed regarding sources of water and food, and eating, drinking, and hygienic habits. Interviewers inspected homes of case-patients and controls to document water treatment, food-handling, and hygienic practices. Faecal specimens and shellfish were cultured for Vibrio cholerae O 1. Isolates were tested for susceptibility to a variety of antimicrobial agents. Drinking unboiled water (odds ratio [OR] = 4.0, confidence interval [CI] = 1.8–7.5), drinking a beverage from a street vendor (OR = 2.8, CI = 1.3–5.9), eating raw seafood (OR = 3.4, CI = 1.4–11.5), and eating cooked crab (OR = 5.1, CI = 1.4–19.2) were associated with illness. Always boiling drinking water at home (OR = 0.5, CI = 0.2–0.9) was protective against illness. The presence of soap in either the kitchen (OR = 0.3, CI = 0.2–0.8) or bathroom (OR = 0.4, CI = 0.2–0.9) at home was also protective. V. cholerae O 1 was recovered from a pooled sample of a bivalve mollusc and from 68% of stool samples from case-patients. Thirty-six percent of the isolates from stool specimens were resistant to multiple antimicrobial agents. Specific prevention measures may prevent transmission through these vehicles in the future. The appearance of antimicrobial resistance suggests the need for changes in current methods of prevention and treatment.

The effects of ingested Salmonella enteritidis (SE) dose on incubation period and on the severity and duration of illness were estimated in a cohort of 169 persons who developed gastroenteritis after eating hollandaise sauce made from grade–A shell eggs. The cohort was divided into three groups based on self–reported dose of sauce ingested. As dose increased, median incubation period decreased (37 h in the low exposure group 21 h in the medium exposure group v. 17·5 h. in the high exposure group, P = 0.006) and greater proportions reported body aches (71 v. 85 v. 94%, P = 0.0009) and vomiting (21 v. 56 v. 57%, P = 0.002). Among 118 case-persons who completed a follow–up questionnaire, increased dose was associated with increases in median weight loss in kilograms (3.2 v. 4.5 v. 5.0, P = 0.0001), maximum daily number of stools (12.5 v. 15.0 v. 20.0, P = 0.02), subjective rating of illness severity (P = 0.0007), and the number of days of confinement to bed (3.0 v. 6.5, P = 0.04). In this outbreak, ingested dose was an important determinant of the incubation period, symptoms and severity of acute salmonellosis.

Plasmids were found in 1022 of 1089 (94%) of drug–sensitive strains of Salmonella enteritidis phage type 4 from humans (sporadic and outbreak cases), poultry (chickens) and eggs in England and Wales in the 5-year period 1988–92 and 25 plasmid profile patterns were identified. Strains characterized by a single plasmid of 38 MDa predominated ( = plasmid profile type SE 38), comprising over 90% of isolates from humans, 70% from poultry and 92% from eggs. Eleven profile types were identified in strains from humans, 21 in strains from poultry and 3 in strains from eggs. Eight of the 11 patterns identified in human isolates were found in strains from poultry and 2 in strains from eggs. In contrast 15 patterns seen in poultry were not found in strains from humans. Four percent of strains from humans and 13% from poultry did not carry the 38 MDa plasmid but all strains from eggs were found to carry this plasmid. The second most common profile type in strains isolated between 1981 and 1988 was not identified in strains isolated from 1988–92. It is concluded that plasmid profile typing is a useful method for rapid differentiation within phage type 4 of S. enteritidis but that methods which can discriminate within the predominant profile type, SE 38, are now required.

The important role of plasmid genes in assessing virulence for BALB/c mice in salmonella, and the difficulty of using standard techniques to detect them, led us to develop a detection method by gene amplification.

One hundred and forty–three strains (71 serovars) of salmonella and 35 strains of other species were tested using specific oligonucleotide primers. The amplification products were identified by a specific oligonucleotide probe. Forty-nine salmonella strains from ten serovars (S. abortus ovis, S. choleraesuis, S. dublin, S. enteritidis, S. gallinarum / pullorum, S. hessarek, S. typhimurium, S. IIIa 48:z4, z23, S. IV 43: z4, z23:-, S. V 28:a:-) produced a positive and specific response.

Because of various origins of the strains possessing the gene sought and the diversity of the responses, both from one serovar to another and in the same serovar, this search has its place among the epidemiological markers in general use. This method appears well suited to the research and detection of plasmid genes associated with mouse virulence in salmonella.

A total of 675 stdrains of Salmonella bareilly received from different parts of India and France during 1959–92 were phage typed using six bacteriophages. Overall ttypability achieved was 90·8% with 23 distinctphage types excluding a group of untypable strains. Phage types have been defined in octal code. Simpson's coefficient was applied for diversity index having a value of 0·839. This system was found to be reproducible, stable and epidemiologically useful.

The electrophoretic variations of carboxylesterase B and of esterases A, C and I, the presence of mannose resistant haemagglutinin, α–haemolysin, cytotoxic necrotizing factor type 1 (CNF1) and certain O antigens were compared in 150 strains of Escherichia coli responsible for extra-intestinal infections. Electrophoretic mobilities of outer membrane proteins (OMP) were also studied for strains belonging to O4, O6, O7, O8 and O75 serogroups. Fast migrating allozymes of carboxylesterase B (pattern B1) were correlated with slow migrating allozymes of esterase C, serogroups O7 and O8, lack of virulence factor, and particular OMP patterns, whereas slow migrating allozymes of carboxylesterase B (pattern B2) were correlated with fast migrating allozymes of esterase C, serogroups O2, O4, O6, O18 and O75, virulence factor production, and distinct OMP patterns. Allozymes of esterases A and I were not clearly correlated with the distribution of virulence factors. The pattern B2 was more strongly associated with CNF1 than with α–haemolysin and mannose resistant haemagglutinin. These results substantiate the view that the electrophoretic pattern B2 of carboxylesterase B identified most of the highly pathogenic strains implicated in extra-intestinal infection of humans.

One hundred and eighty–one stool specimens from patients with various types of diarrhoea (135 patients) or from non-diarrhoeal controls (23 acute medical patients, 23 inflammatory bowel disease in remission) were investigated using a colony–blot DNA hybridization assay for the presence of Verocytotoxin–producing (VTEC), enteroaggregative (EAggEC) and diffusely adherent (DAEC) Escherichia coli. Twelve patients had probe–positive EAggEC in the stool and 8 of these had diarrhoea, 6 following recent travel. Eight patients had DAEC, 7 of whom had travellers diarrhoea. Six of 10 (60%) travellers with gastroenteritis, but without a recognized enteric pathogen, were positive for EAggEC (4) or DAEC (2). Five of 10 (50%) travellers with gastroenteritis related to a recognized enteric pathogen also had DAEC identified in their stool. Of the 23 acute medical control patients 11 had been abroad, 4 of these were immigrants and had EAggEC. VTEC were not found and, with one exception, immunoassays for antibodies to E. coli O 157 and O 2 lipopolysaccharides were negative.

Aerosol infection (AI) of Porton outbreak mice with Listeria species, exhibiting varying degrees of virulence, was compared with gastric intubation (GI) on the basis of numbers of deaths. 50% lethal dose (LD50) and pattern of listerial infection. The AI route appeared to be more sensitive, efficient and consistent than GI in that it required 105 fewer micro-organisms to obtain infection and death then ensued within 4 days, with GI deaths usually occurring on day 7. All the virulent strains tested caused 100% mortality by AI, while virulent and avirulent strains were indistinguishable by GI. Bacterial counts in the livers and spleens of infected mice were consistent with the relative virulence of the infectious agent using AI but not in GI mice. There were higher numbers of micro-organisms and more widespread lesions in the organs of AI mice than in GI. Results indicate that AI is an accurate in vivo indicator of virulence in listeria and using AI, bacterial counts in the liver and spleen could replace LD50 tests, thereby reducing the number of animals required for in vivo virulence testing.

During the period 1961–91 a total of 567 635 strains of Staphylococcus aureus from hospitalized patients in Denmark have been characterized according to their antibiotic resistance, site of isolation and phage type. Strains of phage group II (typed by the phages 3A, 3C, 55 and 71) have been analysed further. The occurrence of group II strains was relatively constant (approximately 16%) from 1961 until 1983. Since then the frequency of group II strains increased; in 1991 they accounted for 22.7% of all S. aureus strains isolated. Strains of group II can, on the basis of their phage types, be divided in four subgroups: 3A, 71, 71 + and the ‘rest of group II’. Furthermore, within these groups strains may differ from one another in respect to their sensitivity to phages.

The increased isolation of group II strains during recent years was because of an increase in strains of subgroups 71 + and the ‘rest of group II strains’. In 1991 these two subgroups accounted for 89.7% of all group II strains. Furthermore, an increasing number of group II strains, 71.4% in 1991, was typable only at RTD × 100. The increase in the number of group II strains was even throughout Denmark. All four subgroups of group II have, during the observation period, become more frequently resistant to penicillin and/or tetracycline. Strains typed at 100 × RTD of subgroup 71 + and the ‘rest of group II’ are more frequently antibiotic resistant than the rest of the group II strains.

Strains of the increasing subgroups occurred most often in abscesses.

Ribotyping, with homologous or heterologous (Escherichia coli) r–RNA, of the propagating strains for phages of the international set for strains of Staphylococcus aureus of human origin was undertaken to determine the discrimination of this typing method. Ribotyping could distinguish between strains of different phage groups, but could not distinguish between seven phage group III strains of different phage type. Ribotyping may be a useful adjunct to phage typing in S. aureus but is unlikely to replace it as the primary method of epidemiological typing.

This report describes a double outbreak of staphylococcal scalded skin syndrome (SSSS) in which two distinct tetracycline-resistant strains of Staphylococcus aureus producing different exfoliative toxins were involved. In the first phase the daytime staff of the delivery unit and eczematous skin conditions in midwives were implicated as the probable source. In the second phase a source within a post-natal ward was suggested with local cross-infection. In the final phase both sources were epidemiologically linked to cases of SSSS. Because early discharge was the policy of the unit many cases presented in the community rather than in the hospital.

Confirmation of epidemiological findings was provided by additional laboratory studies. Two distinct strains of S. aureus could be defined, differing in phage-typing patterns, the exfoliative toxin produced, plasmid profile, cadmium resistance and bacteriocin production. Strict care in hand washing with a chlorhexidine-containing detergent was an important control measure.

To investigate the joint association of patient and strain characteristics with the outcome of meningococcal disease (MD), data were collected on 563 consecutive cases of MD reported between 1989 and 1990 in The Netherlands. The meningococcal isolates were characterized with regard to their surface characteristics. Sequelae occurred in 8.5% of the patients, and were only associated with the presence of bacteraemia. The case-fatality rate was 7.7%. Infants aged ≤ 5 months and patients in the age-groups of 10–19 years and ≥ 50 years had an increased risk for a fatal outcome compared with children from 6 months to 9 years old (Odds Ratios [ORs]: 5.1, 3.4 and 9.8, respectively). The OR for females versus males was 2.3. The ORs for patients with bacteraemia, or a combination of bacteraemia and meningitis, compared with meningitic patients, were 2.3 and 3.1. Meningococcal strain characteristics did not influence the case-fatality rate substantially. In conclusion, host factors were found to be determinants for a fatal outcome of MD in The Netherlands from 1989 to 1990.

Aminoglycoside resistance patterns of 147 Serratia marcescens strains of clinical origin were studied. All strains analysed belonged to three different bacterial populations. The periods of study and the institutions the strains were isolated from correlated significantly with the resistance patterns shown by the strains. The most frequent resistance patterns found were the following: ACC (6')-I at the Hospital Infantil de México (Children's Hospital of México), and ANT (2″) +AAC(6′)-I at the Instituto Nacional de Pediatría (INPed or National Institute of Pediatrics) in Mexico City. Furthermore, the isolation frequency of aminoglycoside-sensitive strains decreased remarkably at the INPed over a 12-year period. These results suggest that there has been a selection of Serratia marcescens strains that are very resistant to aminoglycosides.

Yersinia enterocolitica is a recognized cause of gastroenteritis in northern Europe. During October 1988-January 1990, a prospective case-control study was performed to address risk factors associated with sporadic. Y. enterocolitica infections in southeastern Norway. Sixty-seven case-patients (mean age 23.4 years, range 8 months-88 years) and 132, age-, sex- and geographically-matched controls were enrolled in the study. Multivariate analysis of the data showed that persons with Y. enterocolitica infection reported having eaten significantly more pork items(3.79 v. 2.30 meals, P = 0.02) and sausage (2.84 v. 2.20 meals, P = 0.03) in the 2 weeks before illness onset than their matched controls; only one patient had eaten raw pork. Patients were also more likely than controls to report a preference for eating meat prepared raw or rare (47 v. 27%, P = 0.01), and to report drinking untreated water (39 v. 25%, P = 0.01) in the 2 weeks before illness onset. Each of these factors was independently associated with disease, suggesting a link between yersiniosis and consumption of undercooked pork and sausage products and untreated water. Efforts should be directed towards developing techniques to reduce Y. enterocolitica contamination of pork and educating consumers about (1) proper handling and preparation of pork items and (2) the hazards of drinking untreated water.

Water was cultured from 39 of 48 hospitals (7 Halifax hospitals and 32 non-Halifax hospitals) in the province of Nova Scotia and from 90 residences (74 private dwellings, 16 apartments) in Halifax to determine the frequency of legionella contamination. Six of seven Halifax hospitals had Legionellaceae isolated from their potable water compared with 3 of 32 non-Halifax hospitals (P < 0.0001). Overall. 19 of 59 (32%) of the water samples from Halifax hospitals were positive for legionellae compared with 5 of 480 (1%) samples from non-Halifax hospitals (P < 0.0000). Five of the six positive Halifax hospitals had Legionella pneumophila serogroup 1 and 1 had L. longbeachae serogroup 2 recovered from their potable water. Legionella contamination was associated with older, larger (> 50 beds) hospitals with total system recirculation. These hospitals also had water with a higher pH and calcium content but lower sodium, potassium, nitrate, iron and copper content.

Fourteen of the 225 (6.2%) water samples from Halifax residences were positive for legionellae – 8% (6/74) of the single family dwellings were positive, compared with 25% (4/16) apartments. The positivity rate of 15.7% for the 19 electric hot-water heaters in Halifax homes was not significantly different from the 32% positivity for Halifax hospitals. L. longbeachae accounted for 2 of the 14 isolates of legionellae from Halifax homes.

The gastric-adapted bacterium Helicobacter pylori plays an important role in gastritis and ulcer disease, but no phenotypic typing scheme presently exists for this organism. With a view to the development of genotypic typing, we have compared isolates of H. pylori from gastritis or ulcer patients with those from subjects exhibiting no disease. Variation was analysed at the urease genes, ureA and ureCD, by employing PCR-generated probes in genomic Southern blot hybridizations. Whilst ureA restriction fragments provided a fourfold subgrouping of strains, ureCD fragments were considerably more discriminatory. Twenty-four combined ureACD profiles were generated with Hind III, subdividing the 64 strains into 11 types and 13 single profiles. The most prevalent profile (UI) was found in 33% of strains, almost all from gastritis or ulcer patients. On the other hand strains isolated from asymptomatic individuals had the most diverse ureACD profiles. A key finding from this set of isolates was that strains of H. pylori associated with general gastroduodenal disease were genetically more homogeneous than strains carried by people without disease symptoms.

Large-scale surveys of immunity to vaccine-preventable diseases may be limited by the inconvenience and expense involved in collection of blood by venepuncture. An alternative method of collecting blood on filter paper for measurement of immunity to diphtheria and tetanus is described. The precut filter disks (Elisadiscs), originally developed for serological diagnosis of disease in pigs, have advantages over previously described methods in that they allow safe handling of minimal volumes of blood (5 μl) which can be conveniently quantified.

To compare values obtained by venepuncture and fingerprick, paired samples were collected from 60 subjects and diphtheria and tetanus antitoxin concentrations were measured by ELISA. There was no significant difference detected between samples collected by the two methods.

The results suggest that Elisadiscs are a reliable alternative to venepuncture for monitoring immunity to diphtheria and tetanus and would be useful for sample collection in remote areas and from children.

Of 41 coagulase-negative staphylococcal isolates from cases of ovine mastitis, 80% were speciated by the ‘API-Staph SYSTEM’ and 90% by a combination of biochemical tests. Staphylococcus simulans and Staph. xylosus were the two most prevalent species.

Staphylococcus aureus (n = 75) isolated from mammary secretions of cows with subclinical and clinical mastitis from several geographic locations in the USA were examined using polymerase chain reaction-based DNA fingerprinting. DNA fingerprints were produced using a synthetic oligonucleotide primer (5‘GTAACGCC3’) to produce a distinct spectrum of amplified DNA fragments facilitating a high degree of resolution for differentiating S. aureus strains. PCR-based DNA fingerprinting grouped the 75 S. aureus isolates into 19 distinct profiles. The technique differentiated closely related strains within and between geographic locations. Findings suggest that certain types are found across geographic regions suggesting a common clonal type. Within herd data suggest heterogeneity among subclinical and clinical isolates of S. aureus strains. Compared to existing typing methods, PCR-based DNA fingerprinting is easy to perform and interpret. Use of PCR-based DNA fingerprinting may allow for a more detailed investigation of the epidemiology of S. aureus mastitis in dairy cows.

Results of serotyping on 291 astrovirus-positive stools collected between 1976 and 1992 showed that about two-thirds (64.9%) were serotype 1. Infections were more frequent in the fourth quarter of the year and there was a suggestion that during the past 5 years serotype 1 has occurred with greater frequency in alternate years. Evidence is provided for the existence of two new serotypes, 6 and 7.