The objective of the study was to assess whether genotypic characterization by means of DNA-fingerprinting pattern (DFP) and multilocus enzyme electrophoresis (MEE) profile as compared to phenotypic characterization would improve the differentiation of Neisseria meningitidis strains associated with outbreaks from strains associated with sporadic cases of meningococcal disease. In addition, the differentiation of serogroup C carrier strains from those associated with an outbreak of serogroup C meningococcal disease was investigated.

A total of 118 N. meningitidis strains were available for the study: 59 from patients involved in outbreaks of meningococcal disease (2 serogroup B and 2 serogroup C), 37 from patients considered to be sporadic cases and 22 serogroup C carrier strains.

Among the 59 strains from patients involved in outbreaks the 4 strains isolated from the patient registered as the first in each outbreak were designated the index strains. Among the remaining 55 outbreak strains 52 were either DFP-identical or DFP-indistinguishable when compared with the one relevant out of the 4 index strains. This was only the case for 17 of the 37 strains isolated from sporadic cases caused by the same serogroup of meningococci during the outbreak periods, and 5 of the 22 meningococcal strains isolated from healthy carriers. Among the 56 (52 + 4) DFP-identical or DFP-indistinguishable outbreak strains 5 different electrophoretic types were identified by MEE.

Among 59 assumed outbreak strains a total of 4 were identified as genotypically distinct. Among the 37 mainly DFP-indistinguishable or DFP-different strains from sporadic cases 17 different ETs were identified, and among the 22 mainly DFP-different carrier strains 13 different ETs were identified. Two strains among those selected from sporadic cases were identical to the outbreak strain. None of the local serogroup C carrier strains isolated during the outbreak of serogroup C disease were identical to the outbreak strain.

Both DNA-fingerprinting and MEE improved the differentiation of meningococci when compared with phenotypic characterization. The results indicate that tracing a virulent strain within an open group of contacts is irrelevant.

A total of 125 strains of Neisseria meningitidis recovered in the course of outbreaks from patients with systemic disease in 11 African countries between 1989 and 1994 were analysed by serogrouping, serotyping and multilocus enzyme electrophoresis. Of the 125 patient strains 115 (92%) belonged to the clone-complex of serogroup A meningococci, designated subgroup III. Among the remaining strains, 4 were also serogroup A, but belonged to the clonal groups I and IV-1 (2 strains each), whilst 6 strains (4 serogroup C and 2 serogroup W135) represented clones of the ET-37 complex. Our results indicated that the second pandemic caused by clones of subgroup III is still spreading in Africa. Towards the West it has reached Niger, Mali, Guinea and The Gambia, and towards the South, the Central African Republic, Uganda, Rwanda, Burundi, Tanzania and Zambia.

Epidemic cholera reached Guatemala in July 1991. By mid-1993, Guatemala ranked third in the hemisphere in reported cases of cholera. We conducted a case-control study with two age-, sex-, and neighbourhood-matched controls per patient in periurban Guatemala City. Twenty-six patients hospitalized for cholera and 52 controls were enrolled. Seven (47%) of 15 stool cultures obtained after admission yielded toxigenic Vibrio cholerae Ol. All seven were resistant to furazolidone, sulfisoxazole, and streptomycin, and differed substantially by pulsed-field gel electrophoresis from the Latin American epidemic strain dominant in the hemisphere since 1991. In univariate analysis, illness was associated with consumption of left-over rice (odds ratio [OR] = 7·0, 95% confidence interval [CI] = 1·4–36), flavored ices (‘helados’) (OR = 3·6, CI = 1·1–12), and street-vended non-carbonated beverages (OR = 3·8, CI = 1·2–12) and food items (OR = 11·0, CI = 2·3–54). Street-vended food items remained significantly associated with illness in multivariate analysis (OR = 6·5, CI = 1·4–31). Illness was not associated with drinking municipal tap water. Maintaining water safety is important, but slowing the epidemic in Guatemala City and elsewhere may also require improvement in street vendor food handling and hygiene.

Ribotyping performed with six restriction endonucleases was used to study the molecular epidemiology of shigellosis in Asturias, Spain. The series included Shigella sonnei from 34 sporadic cases, 3 outbreaks and 3 reference strains, and S. flexneri from 13 sporadic cases and 1 reference strain. The S. sonnei strains were grouped into 5 ribotypes with Sal I, 4 with Hind III and Pvu II, 3 with Bgl II and EcoR I and 2 with Hinc II (Discriminatory Index (DI) between 0·54 and 0·14); the S. flexneri into 5 ribotypes with Sal I, Hinc II and Hind III, and 4 with the other enzymes (DI = 0·71–0·63). The combination of results for 2 or more enzymes facilitated an additional discrimination, the highest values in S. sonnei were for the 6 enzymes (16 types, DI = 0·91) and in S. flexneri for some combinations of 3 or more enzymes (7 types, DI = 0·81). Ribotypes with the 6 enzymes defined 16 clonal lines in S. sonnei and 7 in S. flexneri, which showed a different degree of genetic heterogeneity, and all the lines of each species falling into a different cluster. No line appeared as clearly endemic in the bowels of Asturian people.

An assay was developed for the specific detection of Salmonella enterica serotype Enteritidis, using a novel application of the polymerase chain reaction (PCR). This PCR assay is based on the mismatch amplification mutation assay, an allele-specific reaction, and can discriminate Enteritidis from all other salmonella. PCR primers were selected to amplify a 351-base pair (bp) DNA fragment from the salmonella plasmid virulence A (spvA) gene of Enteritidis. A single base difference at position 272 is present between the nucleotide sequence of the spvA gene of Enteritidis and other salmonellae. The downstream PCR primer, that encompasses position 272 of the Enteritidis spvA gene, was designed to contain a single base mismatch at the penultimate position, resulting in a l-base mismatch with Enteritidis and a 2-base mismatch with other salmonellae that harbour the virulence plasmid. The upstream primer was completely homologous with the region immediately 5′ to the spvA gene. When these primers were used and the annealing and extension reactions were performed at the same temperature, the PCR assay was specific for Enteritidis; no PCR product was detected for 40 other serotypes and 28 different genera examined. In pure culture, 120 colony forming units (c.f.u.) could be detected; a PCR product was observed from template derived from a 5 h enrichment broth culture of chicken seeded with 1 c.f.u. per gram of Enteritidis. This PCR assay is specific, reproducible, and less time consuming than the standard bacteriological methods used to detect Enteritidis.

Bivalve molluscs, (cockles, mussels, scallops and oysters) were examined according to EC shellfish bed classification regulations for faecal coliforms, Escherichia coli and salmonella, and for coliforms and campylobacter which are not specified by these regulations. Salmonella serotypes were detected in 8% of 433 molluscs. Seven salmonella isolations (2%) were made from category A beds, nominally suitable for immediate consumption according to E. coli counts. A higher percentage of salmonella isolates (6%) was detected in shellfish which require relaying or depuration prior to eating. In another survey, thermophilic Campylobacter spp. were found in 42% of 380 shellfish. These findings show that shellfish bed classification on the basis of indicator organisms alone is not sufficient to assure the absence of bacterial, and no doubt viral, pathogens. Depuration and end product specifications which require the absence of salmonellae are an essential part of these regulations. Microbiologists may wish to consider whether tests for pathogens such as salmonella and campylobacter should be included when determining the suitability of shellfish for human consumption.

In an outbreak of plasmid-free Salmonella enteritidis phage type 4 (PT4) food poisoning at a hospital for mentally handicapped people in July 1990, 101 residents and 8 staff were affected and a cohort study implicated beef rissoles cooked by deep-fat frying as the vehicle of infection (relative risk 2·92, 95% confidence interval 1·73–4·93, P ≪ 0·001). Replication of the cooking process demonstrated that the rissoles achieved core temperatures of only 48–60 °C despite external temperatures of 91–95 °C and an oil temperature of 142–154 °C. No residual food was available for microbiological testing but plasmid-containing S. enteritidis PT 4 was isolated in shell eggs from the hospital kitchen.

Two consecutive community outbreaks of Salmonella enteritidis phage type 4 (PT4) traced to the same bakery occurred in Cardiff, Wales during August–September 1992. In the first outbreak, illness was associated with eating custard slices (odds ratio 23·8, 95% confidence interval 6·5–94·4, P < 0·0001), and in the second, with eating fresh cream cakes (odds ratio 15·8, 95% confidence interval 1·6–374, P = 0·004). Environmental investigations implicated cross-contamination during preparation of the cold-custard mix as the cause of the first outbreak, and inadequate cleaning and disinfection of nozzles used for piping cream in the second outbreak. S. enteritidis PT4 was isolated from fresh cream sponge cake retained by a case and from two fresh cream cakes and four environmental swabs obtained at the bakery. This incident illustrates the hazard of widespread environmental contamination with salmonella and the need for thorough environmental cleansing of any premises implicated in an outbreak of food poisoning.

A 9-month trial of a simple typing scheme for ‘thermophilic’ enteric campylobacter isolates at a large Public Health Laboratory is described. Resistotyping was performed with six agents in a method modified by Bolton and colleagues from an earlier scheme, and biotyping was performed by a modified Lior scheme involving three tests. Reproducibility was excellent in both schemes, with test variation < 2%. Five household clusters and one larger presumptive milk-borne outbreak were identified in this scheme, and confirmed in pyrolysis mass spectrometry. The 328 isolates from new patients, excluding duplication from these clusters, were divided into 35 resistotypes with the largest group comprising 22% of isolates. In combined bio- and resistotyping, 86 types were found, with the largest group comprising 9·5% of isolates. The results are contrasted with salmonella sero- and phage-typing, where, on the same basis, the 176 isolates in the same period were divided into 40 groups, with the largest comprising 45% of isolates. Resistotyping, with or without additional biotyping, proved to be a convenient, simple, rapid, highly discriminatory, reproducible and inexpensive method well suited to use in local laboratories. It is a strong candidate for first-line national and local surveillance of campylobacter infections, fulfilling a need for monitoring of this important cause of enteric disease.

Ribotyping with the restriction enzyme XbaI was used to study the dynamics of carriage of non-encapsulated Haemophilus influenzae (NCHi) in Aboriginal infants at risk of otitis media. Carriage rates of NCHi in the infants in the community were very high; the median age for detection was 50 days and colonization was virtually 100% by 120 days of age and persisted at a high level throughout the first year of life [1]. Eighteen different ribotypes of NCHi were identified from 34 positive swabs taken from 3 infants over a period of 9 months. The same ribotypes were recovered for up to 3 months from consecutive swabs of individual infants, and 12 of 27 swabs (44·4%) yielded two ribotypes from four colonies typed. Statistical analysis suggested that most swabs would have been positive for two ribotypes if enough colonies had been typed although the second most frequent ribotype was detected on average in only 13% of strains. Early colonization and carriage of multiple ribotypes of NCHi may help to explain the chronicity of carriage and thus the persistence of otitis media in Aboriginal infants.

An outbreak of legionellosis associated with a hotel in Sydney, Australia, and the subsequent epidemiological and environmental investigations are described. Four cases of Legionnaires' disease were notified to the Public Health Unit. A cross-sectional study of 184 people who attended a seminar at the hotel was carried out. Serological and questionnaire data were obtained for 152 (83%) of these. Twenty-eight (18%) respondents reported symptoms compatible with legionellosis. Thirty-three subjects (22%) had indirect fluorescent antibody (IFA) titres to Legionella pneumophila serogroup 1 (Lp-1) of 128 or higher. The only site which those with symptoms of legionellosis and IFA titre ≥128 were more likely to have visited than controls was the hotel car park (adjusted odds ratio [OR] 14·7, 95% confidence interval [CI]: 1·8–123·1). Those with symptoms compatible with legionellosis, but whose IFA titres were < 128 were also more likely to have visited the hotel car park (adjusted OR 4·4, 95% CI: 1·5–12·9). Seroprevalence of Lp-1 antibodies was higher in those who attended the seminar than in a population sample of similar age. Findings suggested that the 4 cases represented a small fraction of all those infected, and highlighted difficulties in defining illness caused by Lp-1 and in interpreting serology.

Twenty-one patients considered to have acute poststreptococcal glomerulo-nephritis were encountered during 35 years of general practice. In ten of them good evidence of active streptococcal infection at the time of discovery of nephritis was recorded. The more complete the data the more convincing was the evidence of active infection.

In over half of those whose urines were routinely cultured pathogens were isolated and over a third were treated for infection of the urinary tract. Such infections were associated with adverse effects and prolonged illness.

As compared with children, adults in general had a longer history of ill-health, were less likely to present with acute infections and more likely to have urinary tract infections and prolonged illness.

Vigorous antistreptococcal treatment was followed by rapid recovery in those patients so treated whose illnesses were not complicated by urinary tract infections.

Concurrent streptococcal infection and secondary infection of the urinary tract may contribute more to the onset of acute poststreptococcal glomerulo-nephritis and to its course than is currently believed.

A study was carried out to determine the incidence and seroprevalence of Norwalk virus (NV) in the Pretoria area, South Africa, using a recombinant NV (rNV) immunoassay for the detection of serum IgG antibodies. Maternal antibody was detectable in infants' sera up to approximately 6 months of age. Infection with NV was detected serologically in the second year of life and the seroprevalence of NV IgG rose from 37·1% at 7–11 months of age to 62·1% by the age of 40 years. No significant differences in seroprevalence of NV IgG antibody was evident between subjects of European or African ethnic origin, where overall seroprevalence rates were 56·4% and 53·9% respectively.

Weaner pigs (n = 72) were fed 1 of 4 diets. These were based on either cooked rice and animal protein, cooked rice and lupin, wheat and lupin, or wheat and animal protein. Twenty-six of the pigs were slaughtered after 1 month. Those fed the highly digestible cooked rice and animal protein diet had drier colonic contents and faeces, lighter large intestines, and the contents of their large intestines had increased pH values and decreased total VFA concentrations. The other 46 pigs were orally challenged with broth cultures of Serpulina hyodysenteriae, and were monitored for faecal excretion of the spirochaetes, and for the development of swine dysentery (SD). None of 18 pigs fed the cooked rice and animal protein diet developed colonic changes or disease, whereas most pigs on the other diets developed mucohaemorrhagic colitis and dysentery. The reduced fermentation that occurred in the large intestines of pigs fed cooked rice and animal protein was associated with a subsequent failure of colonization by S. hyodysenteriae, and resultant protection against SD.

No animals tested were positive for feline leukaemia virus antigen and Chlamydia psittaci antibodies, but all were positive for antibodies to feline calicivirus (FCV), feline herpesvirus 1 (FHV1) and rotavirus. They had antibodies to feline parvovirus (96%), feline coronavirus (84%) and cowpox virus (2%). Antibody to feline immunodeficiency virus (FIV) was found in 53% of animals, which were less likely to be infected with Haemobartonella felis, and had higher FHV antibody titres than cats without FIV. FCV was isolated from 51% cats and FHV1 and feline reovirus each from 4%. H. felis was present in 42% of animals, and antibody to Toxoplasma gondii in 62%. Clinical abnormality had a significant association with FIV and feline calicivirus infections, but sex, age, social status and feeding group had no significant association with prevalence of any parasites. Toxocara cati and Toxascaris leonina eggs were found, respectively, in 91% and 82% of animals tested.

A multidrug resistant (MDR) variety of Salmonella typhi emerged as the cause of epidemic typhoid fever in some Asian countries including India, during the late 1980s. We faced the epidemic from April 1990 to the first quarter of 1993. However, during this period we continued to isolate chloramphenicol sensitive (CS) S. typhi also. The relative prevalences showed that the frequency of CS variety was unaffected by the epidemic of MDR variety. This is an unusual epidemiological pattern, which indicates that there may have been factors which favoured the epidemic of the MDR variety but not the CS one.