Between 1 August and 15 September 2000, 361 cases of Salmonella enterica serotype Typhimurium definitive phage type (DT) 104, resistant to ampicillin, chloramphenicol, streptomycin, sulphonamides, spectinomycin and tetracycline (R-type ACSSuSpT), were identified in England and Wales residents. Molecular typing of 258 isolates of S. Typhimurium DT104 R-type ACSSuSpT showed that, although isolates were indistinguishable by pulsed-field gel electrophoresis, 67% (174/258) were characterized by a particular plasmid profile. A statistically significant association between illness and consumption of lettuce away from home was demonstrated (OR=7·28; 95% CI=2·25–23·57; P=0·0006) in an unmatched case–control study. Environmental investigations revealed that a number of food outlets implicated in the outbreak had common suppliers of salad vegetables. No implicated foods were available for microbiological testing. An environmental audit of three farms that might have supplied salad vegetables to the implicated outlets did not reveal any unsafe agricultural practices. The complexity of the food supply chain and the lack of identifying markers on salad stuffs made tracking salad vegetables back to their origin extremely difficult in most instances. This has implications for public health since food hazard warnings and product withdrawal are contingent on accurate identification of the suspect product.

The meningococcal capsule is the primary virulence factor with systemic isolates requiring full expression of the capsule but with capability to down-regulate the capsule in order to invade. The meningococcal capsular operon is composed of a number of genes that are involved in capsular synthesis and transport. Differences in capsular synthesis genes may allow discrimination between meningococcal serogroups whereas absence of genes for either synthesis or transport imply that the meningococcus is unencapsulated. Although mechanisms such as slipped-strand mispairing and acquisition of insertion sequences have been demonstrated to be involved in regulation of capsular expression, few studies have addressed the mechanisms of capsular expression in carrier isolates. Following a community-based intervention programme for an outbreak of meningococcal disease, we collected meningococcal carrier isolates from the intervention area and control areas. We undertook genetic analysis of the capsular operon and the mechanisms of capsular regulation, together with an investigation of the potential of capsular genes to identify the genogroup of non-serogroupable isolates. Use of the siaD gene allowed the discrimination of 30/89 (34%) non-serogroupable isolates into B, C, W135 and Y with a siaA gene PCR permitting the characterization of a further 6 isolates whose capsules contained sialic acid. Slipped-strand mispairing was evident in only 4 of 13 genogroupable B isolates and the insertion sequence IS1301 was found in 2 of 36 siaA-positive isolates. Of 51 non-genogroupable isolates 25 (49%) were shown to be ctrA negative. There was a higher percentage of ctrA-positive isolates (P<0·001) amongst meningococcal strains obtained from those sampled in non-intervention schools than those sampled at intervention schools. The ctrA-negative isolates warrant further investigation of their genotypic organization since such avirulent strains may be important in conferring natural protection against invasive disease. We found that after mass antibiotic prophylaxis, recolonization occurs preferentially with non-pathogenic meningococcal strains. This has implications for assessment of the benefits of mass antibiotic and vaccination programmes for outbreak control. Previously expressed concerns of increased risk due to removal of protective flora may have been overstated.

A case control study comprising 282 cases and 319 matched controls was conducted in Denmark during 1996–7. Two estimates of the odds ratio (OR) were determined for each risk factor with and without ‘protective factors’ fitted into the final model. Consumption of undercooked poultry (OR 4·5; 8·2), consumption of red meat at a barbecue (OR 2·3; 4·1), consumption of grapes (OR 1·6; 2·8) and drinking unpasteurized milk (OR 2·3; 11·8) were identified as risk factors in both models. Frequent consumption of pork chops (OR 4·4) and daily contact with domestic animals and pets were identified as risk factors in one of the two models only. Finally, foreign travel was found to be a significant risk factor (OR 2·5). Seasonal and regional interaction was observed for several risk factors and the time elapsed from interviewing of cases to interviewing of controls seemed to influence the effect of certain seasonal dependent risk factors.

While searching for Escherichia coli O157 in the aquatic environment of Calcutta using an immunodetection procedure, we fortuitously detected five strains of Citrobacter braakii, which cross-reacted with the commercially available O157 polyvalent antiserum. The five C. braakii isolates gave positive results when a sensitive dot-ELISA was performed with E. coli O157 monoclonal antibody. Further, the O157 monoclonal antibody recognized the bands of proteinase K treated whole cells of lipopolysaccharide of all the C. braakii isolates. Apart from weak reactions with two or three of the DNA probes, all the C. braakii strains did not hybridize with the other probes spanning the minimum region required for O157 O-antigen biosynthesis. These strains did not possess any of the virulence genes that are commonly found in the Shiga toxin-producing E. coli (STEC) specially the serotype O157[ratio ]H7. Therefore, it appears that the serological cross-reaction between C. braakii and E. coli O157 antiserum is based on structural mimicry between the O-polysaccharide of C. braakii and E. coli O157.

An outbreak of febrile gastroenteritis affected consumers of on-farm manufactured dairy products from a summer farm in Sweden. Symptoms included diarrhoea, fever, stomach cramps and vomiting in 88, 60, 54 and 21% of cases identified. The median incubation period was 31 h. A cohort study with 33 consumers showed an attack rate of 52% and an association between the total amount of product eaten and illness (P=0·07). Twenty-seven of 32 (84%) stool samples cultured for Listeria monocytogenes tested positive, although there was no association between clinical disease and the isolation of L. monocytogenes. In addition, gene sequences for VTEC and ETEC were detected in 6 and 1 subjects, respectively. Bacteriological analysis of cheese samples revealed heavy contamination with L. monocytogenes and coagulase positive staphylococci in all of them and gene markers for VTEC in one of them. Molecular profiles for L. monocytogenes isolated from dairy products, stool samples and an abscess from 1 patient who developed septic arthritis were identical. Results of both microbiological and epidemiological analyses point to L. monocytogenes as the most likely cause of this outbreak. The finding of markers for VTEC in some humans and cheese samples means that a mixed aetiology at least in some cases cannot be conclusively ruled out.

Despite being the commonest bacterial cause of infectious intestinal disease (IID) in England and Wales, outbreaks of campylobacter infection are rarely reported. However, data from the Campylobacter Sentinel Surveillance Scheme suggested that outbreaks might be more common than was previously suspected, since a high proportion of cases reported other illness in the home or in the community at the same time as their illness. To identify factors that might lead to these apparent outbreaks, the exposures of cases of Campylobacter jejuni infection reporting other illness, either in the home or the community, were compared with those for cases not reporting other illness using case–case methodology. Illness in the home was associated with consuming organic meats in the winter, having contact with a pet suffering from diarrhoea or visiting a farm in the 2 weeks before the onset of symptoms. Illness in the community was associated with the consumption of foods in restaurants or drinking unpasteurized milk. Prevention of campylobacter infection requires that better methods of outbreak detection and investigation are developed, which in turn should lead to a better understanding of risk factors.

Sylvatic small mammals were captured in rural habitats near Uppsala, Sweden, to measure the prevalence of bartonella infections, characterize bacterial isolates and identify their host range, and increase our understanding of host–pathogen ecology. During 7 nights of trapping at 3 localities, 236 small mammals were captured (trap success 30%). Bartonella were isolated from bloods of Apodemus flavicollis (19 of 110 tested), Apodemus sylvaticus (6/25), Clethrionomys glareolus (9/60), Microtus agrestis (1/3), Mus musculus (1/18), and Sorex araneus (3/20). Nucleotide sequencing (a 338 bp fragment of the gltA gene) of 40 isolates yielded 6 unique genotypes. Five of the 6 genotypes were most similar to other known bartonella isolated from Old World small-mammal hosts. The most frequent genotype (83%) was isolated from A. flavicollis and M. musculus and was identical to Bartonella grahamii, a recently demonstrated human pathogen. These two hosts were most frequently captured in and around human structures and work places, thus providing conditions that could potentially lead to frequent human infections.

Sixty-six broiler flocks were sampled to determine the presence of Campylobacter spp. at slaughter in 1998. Thirty flocks (45%) tested positive and C. jejuni was identified in all isolates. Combined pulsed-field gel electrophoresis/amplified fragment length polymorphism (PFGE/AFLP) subtyping of 177 isolates from 24 positive flocks revealed 62 subtypes; 16 flocks harboured more than one subtype. When subtyping 101 clinical C. jejuni isolates collected in the same time period and area, 60 PFGE/AFLP types were identified. Comparison of subtypes from poultry and human isolates revealed three shared PFGE/AFLP types, which were present in 11 human isolates. Fifty per cent of all poultry isolates and 39% of all human isolates were resistant to ciprofloxacin. The present study confirms the increase in ciprofloxacin resistance in both human and poultry C. jejuni isolates in Austria, as observed in several countries worldwide. A small number of human isolates shared PFGE/AFLP types with poultry isolates, however, further studies should also focus on the identification of other sources of C. jejuni infection in humans.

On 18 February 2002, the Communicable Disease Unit was notified by the local Public Health Service Laboratory of a child with a positive skin swab for Pseudomonas aeruginosa. This child had attended the local swimming pool and played on an inflatable, subsequently presenting to a Primary Care Nurse Practitioner with folliculitis. A total of 35 cases was identified during the outbreak. This paper describes a case–control study and microbiological sampling of the cases, the suspected inflatable and a survey of 10 swimming pool inflatables in the local area. The odds ratio for developing folliculitis following use of the inflatable was 12 (95% CI 1·05–136·80). The strain of P. aeruginosa found on the inflatable was identical to that obtained from skin swabs of cases. Nine of 10 (90%) of the inflatables sampled were colonized by P. aeruginosa. Attention should be given to the problem of routine decontamination of swimming pool inflatables. P. aeruginosa folliculitis needs to be considered in the differential diagnosis of skin rashes in children, especially in Primary Care.

Fcγ-receptor (FcγR) polymorphisms have been associated with acquisition and severity of invasive meningococcal disease. We studied FcγR polymorphisms in a population with a high incidence of meningococcal disease. Fifty meningococcal disease patients aged 14–60 years, with bacteriologically confirmed disease and without detected complement deficiency, together with 100 healthy adult controls were included in the study. Clinical and bacteriological data were collected prior to FcγRIIa and FcγRIIIb genotyping, which was performed by polymerase chain reaction. The distribution of the FcγRIIa and FcγRIIIb allotypes and their allele frequencies were not significantly different amongst the patients and the controls. The combination FcγRIIa-R/R and FcγRIIIb-Na2/Na2 was less common among patients than controls (OR=0·11, Fisher's exact P=0·05). No significant association was found between the two FcγRs and severity of disease, meningococcal serogroup, age groups or gender. In contrast to previous findings, our study indicates that in Norwegian teenagers and adults, the FcγRIIa and FcγRIIIb allotypes are not decisive for the acquisition or for the severity of meningococcal disease.

We report the isolation and characterization of 16 Leptospira spp. strains isolated from small rodents captured in 11 different regions of inland Croatia. Large NotI and SgrAI restriction fragment allowed us to assign 10 isolates to the serovar istrica, 5 isolates to the serovar tsaratsovo and 1 isolate to the serovar lora. The phylogenetic analysis conducted from the sequences of the first 330 bp from the 16S rDNA gene revealed that the strains belonged to three different species, L. borgpetersenii, L. kirschneri and L. interrogans. Carrier rates in eight rodent species varied from 0 to 71·4%. Mus musculus showed the highest infection level and confirmed its role as a major reservoir of the serogroup Sejroë. For the first time we reported the occurrence of serovars tsaratsovo and lora in Croatia.

An outbreak of salmonellosis, involving cases of infection with Salmonella enteritidis phage types (PT) 5c and 6a, occurred across Scotland between May and August 2000. In total, 70 outbreak cases were microbiologically confirmed. Preliminary investigation suggested that consumption of food, especially chicken dishes, from Chinese restaurants or take-aways (food businesses) was a risk factor for infection. A matched case-control study demonstrated a statistically significant association (OR 22·4, P=0·0024) between infection and consumption of food from Chinese food businesses. A cohort study of novel design suggested that chicken was an important vehicle of infection. However the result did not reach statistical significance (OR 1·7, P=0·3). Extensive environmental investigation was unable to identify the source of the suspected contaminated chicken.

Longitudinal carriage studies of colonizing bacteria such as Neisseria meningitidis can provide important insights into the transmission dynamics of these organisms. Carriage is detected by culturing from a nasopharyngeal swab, but the sensitivity of this technique is low and varies between studies. This paper applies a statistical method for estimating the sensitivity of swabbing, infection rate, recovery rate and initial prevalence of carriage to three longitudinal carriage studies of N. meningitidis. These parameters and 95% confidence intervals were estimated using maximum likelihood techniques. The sensitivity of swabbing was estimated to be 60–83% and this should be taken into account when interpreting carriage studies. The estimates of force of infection and recovery rates seem to be consistent with estimates from more traditional methods. Differences in the parameter estimates between datasets may be due to differences in study design. This method could be used to assist in the design of future carriage studies.

We collected diarrhoea specimens in two hospitals in southern Thailand in 1999 to examine whether infection by the Vibrio parahaemolyticus pandemic clone is prevalent. V. parahaemolyticus was isolated from 317 specimens. Seventy-six per cent of the isolated strains had the pandemic clone-specific characteristics (tdh+, trh−, and an unique toxRS sequence detectable by GS-PCR) and an associated characteristic (the ORF8 sequence of f237 phage). These strains belonged to the three pandemic servovars with the O3[ratio ]K6 strains being dominant and three other serovars (O1[ratio ]K25, O1[ratio ]K41 and O4[ratio ]K12). We also found O1[ratio ]K25 and O1[ratio ]K41 strains with the pandemic clone-specific characteristics among the strains isolated from the international travellers who left Thailand and three other Asian countries between 1998 and 1999, verifying pandemic potential of these strains. The results demonstrate prevalence of infection by the pandemic clone in southern Thailand and suggest emergence of various serovariants in this area and their implication in international spread.

An identifying characteristic of Staphylococcus aureus is the production of staphylocoagulase (coagulase). The aim of this study was to determine the clonal distribution of coagulase gene (coa) variants within populations of S. aureus defined by multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and protein A variation. The N-terminal region of the coa gene from 43 methicillin-susceptible (MSSA) and 252 methicillin-resistant (MRSA) S. aureus human isolates and 9 animal S. aureus isolates was amplified and digested with HinfI. Twelve types were identified amongst the MSSA isolates and the majority (93%) of MRSA isolates were assigned to 5 of the 12 types. MLST and PFGE analysis identified epidemic populations of MRSA and each epidemic population was characterized by a different coagulase type. Nine of the 12 MLST-defined clonal complex ancestral genotypes recently described each carried a different coagulase type suggesting that coagulase evolution and the evolution of the clonal complexes are intimately related.

This study was conducted to determine the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in Malaysian hospitals. A total of 264 MRSA isolates from eight hospitals were subjected to typing by pulsed-field gel electrophoresis (PFGE) of SmaI restricted DNA. Antibiotic disk susceptibility testing was also carried out to determine their resistance patterns. Thirty-one PFGE pattern types were identified. Three major pattern types A, ZC and K were found with type A the predominant profile in c. 80% of strains and present in all hospitals. Unlike type A, other DNA pattern types were unique to the hospitals in which they were isolated. PFGE type A also consisted of strains that were multiply antibiotic resistant. The presence of a single predominant PFGE type in Malaysian hospitals is an important finding which suggests that inter-hospital spread of MRSA had occurred frequently and regularly.

To quantify the host genetic component of meningococcal disease (MD) susceptibility, the sibling risk ratio (λs) was calculated as the ratio of observed MD cases among 845 siblings of 443 UK Caucasian cases to that expected, calculated from age-calendar year specific rates for England and Wales. Twenty-seven siblings contracted MD compared with an expected 0·89, generating a λs value of 30·3. Overestimation of λs due to Neisseria meningitidis exposure was minimized by excluding siblings with MD onset within set time points of the index case. Irrespective of whether siblings contracted MD more than 1, 3, 6, 9 or 12 months after the index case, the λs varied slightly (λs range: 8·2–11·9), suggesting that host genetic factors may contribute approximately one third of the total λs. Social class distribution did not differ between MD cases and the general population of England and Wales. This study is the first to calculate λs for MD and establishes that susceptibility to MD has a significant host genetic component.

Neonatal tetanus (NT) elimination, <1 case per 1000 live births (LB), was assessed at district level in Zimbabwe using a combined lot quality assurance–cluster sampling survey (LQA–CS). Three of the highest risk districts were selected. NT was considered eliminated if fewer than a specified number of NT deaths (proxy for NT cases) were found in the sample determined using operating characteristic curves and tables. TT2+ vaccine coverage was measured in mothers who gave birth 1–13 months before the survey and women aged 15–49 years. NT was considered as eliminated, TT2+ coverage was 78% (95% CI 71–82%) in women aged 15–49 and 83% (95% CI 76–89%) in mothers. The survey cost US$ 30000 excluding costs of consultants. NT incidence was below the elimination threshold (<1/1000 LB) in the surveyed districts and probably in all districts. LQA–CS is a practical, relatively cost effective field method which can be applied in an African setting to assess NT elimination status.

Identification of factors influencing success of Helicobacter pylori (HP) eradication is important for clinical practice. We have prospectively conducted an HP eradication study in the Aichi Cancer Center with a total of 142 patients available for analysis. The overall success rate was 61·3% (95% confidence interval 52·7–69·3%). Smoking during the medication for eradication significantly decreased the success rate (42·9%), whereas smoking cessation during the treatment was associated with a similar rate as for non-smokers (66·7%). We also examined links between an eradication outcome and polymorphisms of Le, Se, IL1A, IL1B, IL1RN and MPO genes, but with one exception none showed any association. The non-functional le allele of Le polymorphisms, leading to decreased expression of Leb antigen to which HP attaches with adhesin, showed a beneficial effect for success. Although further clarification is necessary, our study indicated that smoking cessation and Le gene polymorphisms may affect the success rate of HP eradication.