Investigations were performed by the Laboratory of Enteric Pathogens on Vero cytotoxin-producing Escherichia coli (VTEC) in England and Wales from 1992–4. Bacterial isolates, faeces and sera obtained from patients with diarrhoea, bloody diarrhoea and haemolytic uraemic syndrome were examined. Using serotyping, Vero cytotoxin gene probing and serodiagnostic tests for E. coli O157, evidence of infection was detected in 543, 434 and 491 individuals in 1992, 1993 and 1994 respectively; VTEC of serogroup O157 were isolated from 470, 385 and 411 cases. The O157 VTEC strains belonged to at least 19 different phage types (PT) although 84% belonged to PT2, PT49, PT8, PT1 or PT4. Antibodies to E. coli O157 lipopolysaccharide were detected in 13% of the cases. The average annual rate of infection with O157 VTEC was 0·83/100000 and 12% of the 1458 individuals with evidence of infection with VTEC or E. coli O157 developed haemolytic uraemic syndrome. There were at least 18 general outbreaks and many family outbreaks.

Salmonella enterica Enteritidis in chickens serves as a reservoir for salmonellosis in humans and the structure of its lipopolysaccharide (LPS) has been used to assess invasiveness. Culture from chick spleens generated colonies with an unusual wrinkled morphology, and it is designated the lacy phenotype. To characterize the nature of the morphological change, three isogenic variants were compared. Only the lacy phenotype produced a temperature-dependent cell surface matrix composed of several proteins in association with LPS high molecular weight O-antigen.

Flagellin and a 35 kDa protein were identified as specific proteinaceous components of matrix. Both proteins cross-reacted with a monoclonal antibody previously determined to specifically detect the g-epitope of the Enteritidis monophasic flagella (H-antigen). These results suggest that O-antigen in association with protein contributes to cross-reactivity between molecules. The lacy phenotype was more organ invasive in 5-day-old chicks than isogenic variants producing low molecular weight O-antigen. However, it was no more efficient at contaminating eggs after oral inoculation of hens than a variant that completely lacked O-antigen, thus the lacy phenotype is classified as an intermediately invasive organism. The distinctive colonial phenotype of SE6-E21lacy was used to investigate environmental factors that decreased O/C ratios and contributed to attenuation. In so doing, it was found that growth in complement at 46°C caused matrix producing cells to hyperflagellate and migrate across agar surfaces. These results suggest that the structure of O-antigen might influence the secretion and/or the function of Enteritidis cell-surface proteins. The data also reveal a greater heterogeneity than has been assumed in the phenotype, and possibly the infectious behaviour, of Enteritidis.

During the period 1989–94, 4620 strains of Streptococcus pneumoniae (4063 from blood and 557 from cerebrospinal fluid), from cases of invasive disease in Denmark, were received for capsular typing and penicillin susceptibility testing. During the study period the incidence of bacteraemic pneumococcal disease increased from 10 to 18 cases per 100000 inhabitants per year. The highest rates were seen in the very young, age less than 5 years (23/100000/year, in 1994), and in the elderly, age greater than 60 years (55/100000/year, in 1994). The annual number of cases of meningitis did not vary.

Overall, 92% (93% blood, 87% CSF) of isolates and 94% of all childhood isolates belonged to the 23 vaccine types. The capsular types occurring most commonly among the 4123 pneumococcal strains from adults were types 1, 4, 14, 6A+6B, 7F, 9V, 3, 12F, and 8 (in order of frequency). The ten most frequently occurring types from children (6A+6B, 18C, 14, 1, 7F, 19F, 9V, 4, and 23F) covered 84% of the cases of bacteraemia and meningitis. Reduced susceptibility to penicillin was rare (< 1%).

Restriction fragment length polymorphism of the gene encoding rRNA (ribotyping) was used in combination with conventional epidemiological markers to study phenotypic variations among Streptococcus agalactiae of bovine origin and the possible epidemiological interrelationship between the bovine and human reservoirs of Streptococcus agalactiae.

The bovine material constituted 53 strains (9 antigen combinations) isolated from 11 herds. Herds with a uniform as well as heterogenic antigenic pattern were included. Furthermore, strains isolated in the course of time from the same persistently infected quarters were examined. The human material constituted 16 strains, 4 each of 4 serotypes, isolated from healthy carriers. Finally, nine serotype- and the group reference strains were examined. All strains were serotyped by double diffusion in agarose gel, biotyped (lactose ±), and ribotyped using two restriction enzymes, Hind III and Hha I.

All isolates could be typed by ribotyping and seven ribotypes were identified among the reference strains. The restriction enzymes used alone or in combination gave typing results that allowed discrimination between and within serotype. Combined use of serotype, HindIII and HhaI ribotypes produced 11 types among the 16 human strains. Ribotype analysis discriminated between herds infected with the same serotype. Strains of varying antigenic patterns from the same herd had the same ribotype. Phenotypic variations in serotype observed in persistent intramammary infection were not related to genetic changes as monitored by ribotype. Two ribotypes were represented among both bovine and human strains. The discriminating capability of lactose fermentation was of limited value.

Over a 9-day period in February 1995, 16 newborn babies (age range 2–11 days) and 3 infants (24, 47 and 180 days of age) in a neonatal nursery ward developed diarrhoea accompanied by pyrexia and weight loss. Known enteropathogens were not detected in their stools but Escherichia coli displaying aggregative adherence to HEp-2 cells (enteroaggregative E. coli) were found in 12 (63%) ill infants and in none of 5 well neonates (P = 0·02). The illness lasted 3–9 days (mean 5·2) in 16 babies, whereas in 3 neonates it showed a protracted course of 18–20 days. The source of infection and the mode of transmission remained unclear. The outbreak isolates manifested properties common in this new group of diarrhoeagenic E. coli: mannose-resistant haemagglutination, haemolysis on blood agar, and clump formation in liquid culture medium. They belonged to the O4 E. coli serogroup and expressed multiple antibiotic resistance.

Campylobacter jejuni serogroup reference strains and collections of sporadic and outbreak- associated isolates were examined for restriction fragment length polymorphisms (RFLPs), using C. jejuni random chromosomal and 16S rRNA gene probes. A collection of 48 Penner (HS) and 14 Lior (HL) serogroup reference strains, plus 10 clinical isolates, generated 35 RFLP and 26 ribotype patterns. In combination the two loci generated 48 distinct genotypes. Both probes were able to differentiate between certain random isolates of the same HS/HL serogroups but greater discrimination was obtained with RFLP than with ribotyping. Genotyping distinguished accurately between related and unrelated strains when applied to several outbreaks. Genotypic analysis of C. jejuni by restriction fragment length polymorphisms is a valuable technique for epidemiological typing. Chromosomal variation detected by the two unlinked probe loci provides some information about the genetic relationship between isolates.

The pefA gene which encoded the serotype associated plasmid (SAP) mediated fimbrial major subunit antigen of Salmonella enterica serotype Typhimurium shared genetic identity with 128 of 706 salmonella isolates as demonstrated by dot (colony) hybridization. Seventy-seven of 113 isolates of Typhimurium and individual isolates of serotypes Bovis-morbificans, Cholerae-suis and Enteritidis phage type 9b hybridized pefA strongly, whereas 48 isolates of Enteritidis hybridized pefA weakly and one Enteritidis isolate of phage type 14b failed to hybridize. Individual isolates of 294 serotypes and 247 individual isolates of serotype Dublin did not hybridize pefA. Southern hybridization of plasmids extracted from Enteritidis demonstrated that the pefA gene probe hybridized strongly an atypical SAP of 80 kb in size harboured by one Enteritidis isolate of phage-type 9b, whereas the typical SAP of 58 kb in size harboured by 48 Enteritidis isolates hybridized weakly. One Enteritidis isolate of phage type 14b which failed to hybridize pefA in dot (colony) hybridization experiments was demonstrated to be plasmid free. A cosmid library of Enteritidis phage type 4 expressed in Escherichia coli K12 was screened by hybridization for the presence of pef sequences. Recombinant clones which were deduced to harbour the entire pef operon elaborated a PEF-like fimbrial structure at the cell surface. The PEF-like fimbrial antigen was purified from one cosmid clone and used in western blot experiments with sera from chickens infected with Enteritidis phage-type 4. Seroconversion to the fimbrial antigen was observed which indicated that the Enteritidis PEF-like fimbrial structure was expressed at some stage during infection. Nucleotide sequence analysis demonstrated that the pefA alleles of Typhimurium and Enteritidis phage-type 4 shared 76% DNA nucleotide and 82% deduced amino acid sequence identity.

From September 1991 until August 1993 an epidemiological study involving 20 Dutch broiler farms was conducted to identify risk factors and risk reducing measures for Campylobacter infections in broiler flocks. Campylobacter spp. were detected in 64 (57%) of the 112 broiler flocks and in 25 (63%) of the 40 broiler cycles examined. Univariate analysis of farm management data was performed followed by logistic regression analysis of selected risk and risk reducing factors. The presence of other farm animals, including pigs, cattle, sheep and fowl, other than broilers, was found to be independently associated with an increased risk of Campylobacter infections in broiler flocks (odds ratio (OR) = 1181; P = 0041). Further, the results indicate that application of specific hygiene measures during the rearing period, such as washing hands before tending the broiler flocks, the use of separate boots for each broiler house and the use of footbath disinfection when entering a broiler house, may significantly reduce the risk of Campylobacter infections in broiler flocks.

A retrospective study of 191 cases of septic arthritis was undertaken at Royal Darwin Hospital in the tropical north of Australia. Incidence was 9·2 per 100000 overall and 29·1 per 100000 in Aboriginal Australians (RR 6·6; 95% CI 5·0–8·9). Males were affected more than females (RR 1·6; 95% CI 1·2–2·1). There was no previous joint disease or medical illness in 54%. The commonest joints involved were the knee (54%) and hip (13%). Significant age associations were infected hips in those under 15 years and infected knees in those over 45 years. Seventy-two percent of infections were haematogenous. Causative organisms included Staphylococcus aureus (37%), Streptococcus pyogenes (16%) and Neisseria gonorrhoeae (12%). Unusual infections included three melioidosis cases. Polyarthritis occurred in 17%, with N. gonorrhoeae (11/23) more likely to present as polyarthritis than other organisms (22/168) (OR 6·0; 95% CI 2·1–16·7). Univariate and multivariate analysis showed the hip to be at greater risk for S. aureus than other joints. Open arthrotomy was a more successful treatment procedure than arthroscopic washout or needle aspiration.

From February to July of 1994, 328 faecal samples from 32 herds were collected and verotoxin-producing Escherichia coli (VTEC) found on 84% of the farms. The proportion of animals infected varied from 0–63%. VTEC were recovered from 52 (20%) of 257 cows and from 16 (23%) of 71 calves. Although the VTEC belonged to 25 different serogroups, 7 (O8. O20, O22, O77, O113, O126 and O162) accounted for 46% of strains. Nearly 45% of the 83 bovine VTEC strains belonged to serogroups associated with haemorrhagic colitis and haemolytic uraernic syndrome in humans. However, only 2 (2%) of 83 VTEC strains isolated from cattle belonged to enterohaemorrhagic E. coli (EHEC) serotypes (O26:H11 and O157:H7), and only 8 (10%) were positive for the attaching and effacing E. coli (eae) gene sequence. Polymerase chain reaction (PCR) showed that 17 (20%) of VTEC strains carried VT1 genes. 43 (52%) possessed VT2 genes, and 23 (28%) carried both VT1 and VT2 genes. Characterization of VTEC isolates revelated a heterogeneous population in terms of serogroup and toxin type in the positive herds. This study confirms that healthy cattle are a reservoir of VTEC, but, the absence of eae genes in most bovine VTEC strains suggests that they may be less virulent for humans than eae-positive EHEC.

An outbreak of gastroenteritis occurred in Italy among 39 persons who had attended a private supper. All guests were previously healthy, young, non-pregnant adults; 18 (46%) had symptoms, mostly gastrointestinal (78%), with a short incubation period. Four were hospitalized with acute febrile gastroenteritis, two of whom had blood cultures positive for Listeria monocytogenes. No other microorganisms were recovered from the hospitalized patients' specimens. Epidemiological investigation identified rice salad as the most likely vehicle of the food-borne outbreak. L. monocytogenes was isolated from three leftover foods, the kitchen freezer and blender. Isolates from the patients, the foods and the freezer were indistinguishable: serotype l/2b, same phage type and multilocus enzyme electrophoretic type. Eight (36%) of 22 guests tested were found to have antibodies against L. monocytogenes, compared with none of 11 controls from the general population. This point source outbreak was probably caused by infection with L. monocytogenes. Unusual features included the high attack rate among immunocompetent adults and the predominance of gastrointestinal symptoms.

In recent years infection caused by Salmonella serotype Enteritidis (SE) phage type 4 has spread through Europe but has been uncommon in the USA. The first recognized outbreak of this strain in the USA occurred in a Chinese restaurant in El Paso, Texas, in April 1993; no source was identified. In September 1993, a second outbreak caused by SE phage type 4 was associated with the same restaurant. To determine the cause of the second outbreak, we compared food exposures of the 19 patients with that of two control groups. Egg rolls were the only item significantly associated with illness in both analyses (first control group: oddsratio [OR] 8·2, 95% confidence interval [CI] 2·3–31·6; second control group: OR 13·1, 95% CI 2·1–97·0). Retrospective analysis of the April outbreak also implicated egg rolls (OR 32·4, 95% CI 9·1–126·6). Egg roll batter was made from pooled shell eggs and was left at room temperature throughout the day. These two outbreaks of SE phage type 4 likely could have been prevented by using pasteurized eggs and safe food preparation practices.

Using a direct isolation method Listeria spp. were detected in 101 (47·4%) of 213 houses investigated. L. monocytogenes was present in 45 houses (21·1%). Listeria spp. occurred at all sampling sites. Dish-cloths (37%) and surface samples round the drain in the bathroom (27·2%) were most frequently contaminated. Highest numbers (c. 104 c.f.u./object) were found in dish-cloths and washing-up brushes. Lower levels (up to 103 c.f.u./object) were obtained from kitchen sinks, refrigerator vegetable compartment samples and tooth brushes. In total, 132 isolations of Listeria spp. were made from 871 samples. L. innocua (53%) and L. monocytogenes (41%) were the predominant species in the positive samples. Other Listeria spp. were found in only 6% of the positive samples.

As part of the management of an outbreak of meningococcal infection, 119 school contacts of an index case were swabbed for nasopharyngeal carriage. In a cohort study, risk factors for Neisseria meningitidis carriage were ascertained by means of a questionnaire, completed by 114 (96%) of those swabbed.

Twenty five (21%) cultures were identified as ‘neisseria positive’; of which there were 18 (15%) Neisseria meningitidis isolates, 2 (2%) Neisseria lactamica isolates and 5 (4%) showed contaminants only. Two (2%) carriers were identified as harbouring the implicated outbreak strain. Single variable analysis identified six statistically significant risk factors for meningococcal carriage; increasing age, female sex, manual social class, personal smoking, regular attendance at a discotheque and rhinorrhoea. Multivariate analysis, using logistic regression modelling, found that of these six variables only age, sex and social class remained statistically significant when the other factors were controlled for. Nevertheless the role of smoking, social events and respiratory/viral infections in nasopharyngeal carriage, and other plausible mechanisms whereby age, sex and social class might exert their effect, could usefully be investigated further.

An increase in the number of human isolates of Salmonella virchow phage type (PT) 26 in England and Wales during 1994 was investigated. A national case control study was conducted which included 88 cases and 182 controls. The cases were mostly young adults (median age 26) and 13 (15%) were admitted to hospital. Acquisition of S. virchow PT 26 was associated with the consumption of any chicken (OR 2·5, CI 1·1–5·8), of chicken curry from restaurants and take aways (OR 2·9, CI 1·4–6·1), and of some other diverse types of pre-prepared chicken (OR 3·8, CI 1·9–7·6). Halal chicken was associated (P = 0·006) with illness in a subset. There were negative associations with contact with animals (OR 0·47, CI 0·23–0·95) and with the consumption of chicken cooked whole (OR 0·37, CI 0·21–0·66). The increase in S. virchow PT 26 may be due to changing epizoology and may be an indicator of what will become the dominant salmonella strain in poultry in future years. The increasing incidence of S. virchow PT 26 is of particular concern because of its association with more invasive disease in humans.

Cholera is one of the three diseases subject to the International Health Regulations. After a period of over 30 years, the seventh pandemic of cholera, which started in South East Asia in 1961, still shows no sign of a decline. On the contrary, it has increased its severity and invaded many other countries in Africa and Latin America. In the last two years, there has been a recrudescence of the disease in South East Asia and Western Pacific Regions. The discovery of a new strain of Vibrio cholerae 0139 in these regions is causing concern in view of its potential to cause major epidemics and higher mortality. Hong Kong had two intensive outbreaks of cholera in the last two years. The cause of these outbreaks was not clear, but adverse environmental conditions and increasing pollution of coastal waters have been implicated. The spread of cholera knows no geographical boundaries. There is a need for intensified efforts among health authorities in the affected areas to prevent the international spread of the disease.

The occurrence of epidemics of vaccine-preventable diseases, and the immunization coverage required to prevent them, is affected by the presence of households and heterogeneity in the community. We consider a community where individuals live in households and are of different types, according to infectivity and/or susceptibility to infection. We describe a method for computing the critical immunization coverage to prevent epidemics in such communities and discuss the effectiveness of immunization strategies. In a heterogeneous community where individuals live in households several immunization strategies are possible and we examine strategies targeting households, randomly selected individuals, or groups with highly intense transmission, such as school children. We compare estimates of the critical immunization coverage if we assume that disease is spread solely by random mixing with estimates which result if we assume the effects of the household structure. Estimates made under these two sets of assumptions differ. The results provide insights into the community effects of vaccination, and the household structure of the community should be taken into account when designing immunization policies.

The ability to produce large quantities of bioflim on solid surfaces in vitro is believed to distinguish potentially pathogenic strains of Staphylococcus epidermidis from commensals. Bioflim consists of staphylococcal cells encased in a matrix of extracellular polysaccharide (also referred to as slime), firmly adherent to each other and to the underlying surface structure. The association of slime with colonization of catheter surfaces in vivo has been examined extensively. Less attention has been paid to the contribution of slime to infections that occur in the absence of an inserted device. In a mouse model of subcutaneous infection without an implanted device 10 S. epidermidis strains (5 slime-positive, 5 slime-negative) produced abscesses; thus a foreign body is not essential for the expression of virulence by S. epidermidis. Biofilm-positive strains produced significantly more abscesses, that persisted longer than biofilm-negative strains. In these chronic infections, large numbers of staphylococci were associated with macrophages and viable staphylococci were cultured from specimens of pus collected at autopsy. Thus slime or components of slime appear to delay the clearance of S. epidermidis from host tissues, possibly by interfering with intracellular killing mechanisms. However, differences in the capacity to produce abscesses, within both the slime-positive and slime-negative groups, indicate that other factors also contribute to the virulence of S. epidermidis.

Prevalence of brucella-specific antibodies was measured in 597 persons in high-risk occupations living in 10 regions of Lebanon using the standard agglutination test (SAT), anti-human globulin (Coombs') test (AHGT) and enzyme-linked immunosorbent assay (ELISA) for measuring immunoglobulin G (IgG), IgM and IgA. The study population consisted of butchers (54%) farmers (35%), laboratory technicians (8%), abbatoir workers (2%) and veterinarians (1%), with 82% males and 18% females. The overall seroprevalence based on SAT and AHGT titres of ≥ 80 was 1·7% and 15%, respectively, but seroprevalence varied by region from 0–5% in SAT and from 3·4–34% for AHGT. The overall seroprevalence based on ELISA IgG (OD≥0·6), IgM (OD≥0·6) and IgA (OD≥0·3) was 57, 61 and 26%, respectively. The highest seroprevalence was noted in Biqaa (34%), Kisrwan (24%), Shouf (21%), Sidon (16%) and Aley (12) regions. Nineteen percent of those surveyed reported symptoms that could be associated with brucellosis. We conclude that exposure to brucellosis is high among persons in high-risk occupations from all surveyed regions in Lebanon. Such findings should be used to design control measures especially now that the 17 years of civil strife is over.

Pulsed-field gel electrophoresis (PFGE) of Cpo I-digested genomic DNA and ribotyping (Bgl I) were applied to 60 Vibrio cholerae strains including 48 V. cholerae O139 from Thailand to compare their value in differentiating strains of the present V. cholerae O139 epidemic. PFGE patters were divided into groups A and B representing five and four subtypes, respectively, while ribotyping showed four different patterns. PFGE group B subtypes were only presented among O139 isolates from Thailand, whereas four O139 strains from Bangladesh and India showed identical PFGE group A subtypes observed in O139 isolates from Thailand. Two nontoxigenic O139 isolates from Thailand showed different and unique PFGE types as did five V. cholerae non-Ol non-O139 isolates containing a gene virulence complex found in V. cholerae O139. These results indicate that PFGE (Cpo I) can resolve recent evolutionary divergence within V. cholerae O139 and offers a useful supplementary tool for following the progressing V. cholerae O139 epidemic.