The genomic DNA of 39 strains of Salmonella typhi isolated from local residents and patients who had visited countries in the Asian region was analysed for restriction fragment length polymorphisms (RFLP). Pulsed-field gel electrophoretic (PFGE) analysis of Xba I- and Spe I-generated genomic restriction fragments established 22 PFGE types whereas phage typing differentiated the 39 isolates into 9 distinct phage types. This study showed that PFGE is more discriminatory than phage typing as it is capable of subtyping S. typhi strains of the same phage types. Genetic relatedness among the isolates was determined. Seven major clusters were identified at SABSof > 0–80 and the remaining 13 isolates were distributed into minor clusters which were related at SABS of less than O.80. In conclusion, PFGE analysis in conjunction with distance matrix analysis served as a useful tool for delineating common S. typhi phage types of diverse origins from different geographical localesand separated in time.

Salmonella enteritidis PT4 was recovered from fingers following the breaking of intact shell eggs artificially contaminated in the contents with the bacterium. Kitchen utensils used to mix egg dishes were salmonella-positive, sometimes after washing. Following the preparation of batter or the mixing of eggs, S. enteritidis was recovered from work surfaces over 40 cm from the mixing bowl. The bacterium survived well in thin, dry films of either batter or egg and, from an initial level of one cell per cm2, could be recovered from formica work surfaces 24 h after contamination.

Eighty-nine Salmonella enteritidis phage type 25/17 strains isolated from a localized outbreak in the German state Nordrhein-Westfalen (outbreak NWI) could not be further differentiated by biochemotyping and plasmid pattern analysis. They were submitted to a complex typing system consisting of modern physico-chemical analytical procedures. In lipopolysaccharide pattern analysis the strains proved to be homogeneous. In multilocus enzyme electrophoresis, outer membrane and whole cell protein pattern (WCPP) analysis, and Fourier transform infrared (FT–IR) spectroscopy (increasing extent of differentiation in the given order) strains deviating from each basal pattern were found. The extent of correspondence in these deviations was satisfactory.

Forty-six strains of the same sero- and phage type, however, obtained from different outbreaks, were additionally typed. The results obtained with them indicate that the data of the first group were not restricted to strains from outbreak NWI, but of general validity.

It was found that both WCPP and FT–IR represent valuable methods for the sub-grouping of bacteria.

A comprehensive analysis of the epidemiology of salmonellosis in a major hospital in Hong Kong from 1982–93 is reported. The trend of salmonella isolations over the past 12 years and changes in the occurrence of individual serotypes are delineated. A total of 5328 isolates were analyzed. Groups B (Salmonella typhimurium and S. derby) and E (S. anatum) were the commonest serogroups isolated from the intestinal tract in all age groups. A significant increase in the isolation of group D salmonellae has been observed since 1989. This is accounted for by a substantial rise in S. enteritidis isolation as seen in Western countries, despite a concomitant decrease of S. typhi. The extraintestinal isolation index (EII) is proposed as an index of the virulence potential of individual serotypes and serogroups. Group D salmonella was found to be the most invasive serogroup. While group D was the predominant serogroup isolated from extraintestinal sites in patients older than 1 year, group B serotypes (especially S. typhimurium) were more frequently seen in infants younger than 12 months.

The study was conducted to isolate and characterize campylobacter, enterotoxigenic Escherichia coli-labile toxin (ETEC-LT), shigella and salmonella in flies and water.

The material for the study, flies (n = 300) and water samples (n = 148), was collected from different localities in and around Lahore, Pakistan. Cultivation of the samples was performed on conventional standard media. Membrane filtration technique was used for water prior to culture. Determination of ETEC-LT was done by GM1 ELISA.

Results of our study showed that flies and water were reservoirs for all the four pathogens, campylobacter, ETEC-LT, shigella and salmonella. Flies from the village were carrying fewer enteropathogens, while water from the village was found to be more contaminated as compared to the city. Campylobacter and ETEC-LT were the most frequently isolated pathogens in both flies and water.

Thus the incidence of diarrhoeal disease in children of developing countries may be decreased by providing plenty of safe drinking water, improving excreta disposal, toilet facilities and giving education in personal hygiene.

Discriminatory typing methods are invaluable in the investigation of outbreaks of infectious diseases. Single primers were used to generate randomly amplified polymorphic DNA (RAPD) profiles from Klebsiella pneumoniae isolates of various serotype and K. pneumoniae isolates from cases of sepsis at a Malaysian hospital and two English hospitals. RAPD profiles of acceptable reproducibility, a maximum of three minor band variations, were produced using a rapid DNA extraction method. RAPD typing of K. pneumoniae was shown to be as discriminatory as restriction fragment length polymorphism analysis using pulsed field gel electrophoresis yet quicker and less costly. The findings suggest that RAPD typing may be a useful tool for the epidemiological typing of K. pneumoniae.

Twenty-two reference isolates and 30 local isolates of group A Streptococci were classified into 36 electrophoretic types (ET) on the basis of allozyme variation at 27 enzyme loci. Local isolates were characterized by a high frequency of M-non typable strains. M-type and ET were more closely associated in local isolates from an endemically-infected population; nevertheless, amongst the local isolates there were also strains of the same ET type with different M-types. A possible explanation is that genetic exchange between strains may introduce different M-types into strains of defined ET when these are exposed to strong selection in the presence of heavy loads of infection.

In contrast to the reported clustering of strains associated with toxic shock-like syndrome into two closely related ET clones, we found no relationship of ET phenotype to acute poststreptococcal glomerulonephritis or rheumatic fever.

Staphylococcus aureus strains of type 95 in Denmark have increased to a frequency of 20% of the total S. aureus population. A clonal origin and possible subdivision of these strains have been discussed. In the present investigation 35 epidemiologically unrelated S. aureus strains of type 95 as well as reference strains of other types have been analysed by other typing techniques including lectintyping, multilocus enzyme electrophoresis and pulsed-field gel electrophoresis of genomic restriction fragments. No subdivision could be achieved based on any of these methods and a clonal origin seems therefore possible.

Human infections with pathogenic strains of Yersinia enterocolitica have been linked to contact with dogs excreting these microorganisms. This study examines the carriage and transmission of Y. enterocolitica biotype 4, serotype 03 in dogs. Fourteen 6-month-old cross-bred dogs were separated into 5 groups, 2 containing 4 dogs (I and II) and the others 2 dogs (III-V). Each of the 4 dogs in Group I and 2 of the dogs in Group II were inoculated orally with the test strain. Bacteriological examination of faecal samples showed that dogs can be readily infected and can carry the organism for up to 23 days. The two in-contact dogs in Group II started to shed the test organism after 5 days. Subsequent transfer of these dogs to Group III and those in Group III to Group IV showed that Y. enterocoliticabiotype 4, serotype 03 can be readily transmitted between dogs. At no time did any of the dogs show clinical signs of infection. Group V served as a negative control for the trial. These findings suggest that dogs can carry Y. enterocoliticabiotype 4, serotype 03 asymptomatically and hence might act as a potential source of infection for people.

Although there has been a considerable amount of research conducted into Bacillus anthracis, the causative agent of anthrax, the data are widely disseminated in the scientific literature and are therefore not always easy to assimilate. In view of continuing concern about potential anthrax contamination in environmental materials and sites, this review brings together the currently available information relating to the health hazards from B. anthracis. The relevance of the available information for risk assessment purposes is assessed.

Enzyme immunoassays (EIA) were used to measure serum antibodies to Cryptosporidium in four immunocompetent adults with recent proven cryptosporidial infection, 379 healthy children and 73 adult volunteers in Melbourne, Australia, and 205 children in Papua New Guinea (PNG) (47 healthy children; 158 with pneumonia). Antibodies peaked 3–6 weeks after infection and fell to baseline within a few months. A high level (5000 EIA units/ml) or a significant change between paired sera, of IgG or IgM, were taken as evidence of recent infection and found in 24% of PNG children and in 8% of children and 5% of adults in Melbourne. Among PNG children with pneumonia who had high cryptosporidial antibody levels, those with measles (6/8) were significantly more likely (P = 0·002) to have diarrhoea than the remainder (4/28). Symptomatic cryptosporidiosis may be associated with transient immune suppression due to viral infection. This study indicates that serological surveys can contribute to an understanding of the epidemiology of cryptosporidosis.

In 1993 New York and Texas each reported a human rabies case traced to a rare variant of rabies virus found in an uncommon species of bat. This study examined the epidemiology of bat rabies in New York State. Demographic, species, and animal-contact information for bats submitted for rabies testing from 1988–92 was analysed.

The prevalence of rabies in 6810 bats was 4·6%. Nearly 90% of the 308 rabid bats identified to species were the common big brown bat (Eptesicus fuscus), which comprised 62% of all submissions. Only 25 submissions were silver-haired bats (Lasionycterus noctivagans), the species associated with the two 1993 human cases of rabies, and only two of these bats were positive. Rabies was most prevalent in female bats, in bats submitted because of human or animal contact, and in animals tested during September and October.

These results highlight the unusual circumstances surrounding the recent human rabies cases in the United States. A species of bat rarely encountered by humans, and contributing little to the total rabies cases in bats, has been implicated in the majority of the indigenously acquired human rabies cases in the United States. The factors contributing to the transmission of this rare rabies variant remain unclear.

A common source outbreak of small round structure virus (SRSV) gastroenteritis affected 81 patients and 114 staff in four hospitals served by one central hospital kitchen. Eating salad items was found to be significantly associated with illness. In a cohort study of a staff buffet function eating turkey salad sandwiches was associated with illness (relative risk = 2·4; 95% CI = 1·4–4·1; P = 0·003), and a case control study of patients in one hospital showed an odds ratio of 6·6 (95% CI = 1·0–71·6; P = 0·04) for eating tuna salad and becoming ill. One of two food handlers who prepared the salads became ill the day following food preparation; she also had a young child at home who had been ill with a gastrointestinal illness during the previous two days. Contamination of food by mechanical transmission of the virus from the child via clothes and hands of the mother, or pre-symptomatic faecal excretion in the mother are possible explanations of contamination of food.

A total of 3522 samples of serum, collected anonymously from women attending an antenatal clinic, was tested for hepatitis B surface antigen and antibody to hepatitis C. The prevalence of anti-HCV was low; only five confirmed positives were found (0·14%). The prevalence of hepatitis B overall was 0·56%, but was 1·04% in women from immigrant groups. Hepatitis B carriage is therefore four times more common than hepatitis C carriage in the antenatal population comprised of various ethnic origins. The patterns of infection in the two viruses are reversed, hepatitis B being more common in Asian, S.E. Asian and West Indian mothers and hepatitis C being more common in mothers of white Caucasian origin. Routine antenatal screening for anti-HCV is discussed.

This study demonstrates a very high prevalence of antibodies to hepatitis C virus among Icelandic intravenous (i.v.) drug users. Of 152 identified i.v. drug users 95 (63%) were shown to have antibodies to the hepatitis C virus. In contrast the seroprevalence in the general Icelandic population is low, (0·2%). Almost all cases of hepatitis C virus infection in Iceland are due to i.v. drug use or to use of infected blood or blood products. Sporadic cases with unexplained modes of transmission, a significant portion of hepatitis C infections elsewhere, are virtually non-existent in Iceland. The results of this study are consistent with the hypothesis that the sporadic community-acquired cases could be caused by blood transfer due to bites from insect vectors such as mosquitoes which are not found in Iceland.

A seroepidemiological survey was conducted in Singapore to assess the prevalence of antibody to human parvovirus B19. Sera were collected from 600 healthy individuals between 6 months and over 50 years of age and tested for IgG antibody against B19 virus by antigen capture indirect immunosorbent assay. The overall seropositivity rate was 16·2%. All the children under 5 years of age were seronegative. Antibody prevalence increased gradually from 3·5% in school children (5–14 years of age) to 7·7% in age group 15–19 years and then to 10·3% in young adults (20–24 years of age). In the age group 25–34 years the prevalence was 28% and in the age group over 35 years 65% had parvovirus B19 antibody. The results of the survey indicate that there has been very low incidence of B19 virus infection in Singapore during the last two decades.

An epidemiological study of hepatitis A and enteroviruses was conducted in a military diving training school, by evaluating the viral contamination of water using an ultrafiltration concentration technique, and assessing seroconversion and the presence of virus in stool specimens obtained from 109 divers and 48 controls. Three of 29 water specimens were positive for enterovirus by cell culture and 9 by molecular hybridization. There was little or no risk of virus infection during the training course (49 h exposure) because there was no significant difference between divers and controls for both viral isolation and seroconversion. However, a higher percentage of coxsackievirus B4 and B5 seropositive divers suggests that these were more exposed during previous water training. No hepatitis A virus (HAV) detection and no seroconversion to HAV was observed. The rate of HAV seropositive subjects was 17% in this 24·5-year-old population

Several methods for demonstrating antibody to Crimean-Congo haemorrhagic fever virus were compared on serum samples taken from 101 patients during the acute stage of illness and at intervals for up to 59 months thereafter, with emphasis on early detection of the immune response. The deaths of 23 patients on days 5–14 of illness were ascribed to the effects of the disease; two patients died later from other causes. Very few of the patients who died from the acute illness mounted an antibody response detectable by the methods tested. Four patients who died and 18 who recovered were treated with immune plasma collected from recovered patients. Treated patients acquired IgG antibody from the plasma, but it was possible to discern the onset of an endogenous IgM response in those individuals who survived the disease by all of the methods tested. Indirect immunofluorescence (IF) tests detected IgM and/or IgG antibodies at the earliest on day 4 of illness in about 10% of patients who survived the disease, and by day 9 all survivors had antibodies demonstrable by IF. A biotin-streptavidin IF technique offered no advantage over the standard IF test for the early detection of IgG antibody, but demonstrated higher antibody titles and detected IgM antibody earlier in about a quarter of the patients tested. An IgM-capture enzyme-linked immunoassay (ELISA) and an IgG sandwich ELISA demonstrated higher antibody titres than did IF tests, and detected antibody responses at an earlier stage of infection than did IF tests in about one-fifth of patients, but the reverse was true in a similar proportion of instances. A competition ELISA, which detected total antibody activity, produced lower titres than did the IgM and IgG ELISAs, but yielded results which were in close agreement with the findings in IF tests. It was concluded that the IF tests were most convenient for use in making a rapid serodiagnosis of the disease.

Sensitivity, specificity and predictive values of an enzyme-linked immunosorbent assay (ELISA) for detecting antibodies against bovine leukaemia virus (BLV) were evaluated using a representative sample of 145 serum pools, comprising from 3 to 48 individual sera. The sample was constituted according to the frequency distribution of the negative and positive pools analysed during a screening involving the whole cattle population of Belgium. Sensitivity and specificity were estimated to 88·9% and 100% and the predicted negative and positive values were 99·9% and 100%, respectively. These results indicate the use of serum pools is suitable for the detection of BLV infected herds in eradication campaigns.