Great strides have been made towards the control of poliomyelitis since the introduction of the two poliovaccines – inactivated poliovirus vaccine (IPV), which was licensed in the United States in 1954, and live attenuated oral poliovaccine (OPV), in 1961. Today a large majority of physicians and other health–care workers in industrialized countries never see a patient with paralytic poliomyelitis. Unfortunately, this is far from the situation in many developing countries, particularly in tropical and subtropical climates, where hundreds of thousands of children still become paralysed victims, year in and year out.

A study was made of the persistence of different Salmonella serotypes in hens' egg albumen in vitro at 4, 20 and 30 °C. The majority of serotypes remained viable but did not increase in numbers at 20 and 30 °C for 42 days. At 4 °C many of the serotypes died out.

The addition of ferric ammonium citrate on the 42nd day of incubation induced multiplication of organisms incubated at 20 and 30 °C, but not at 4 °C. The pH and glucose concentration of the albumen diminished only when heavy growth occurred.

Salmonella enteritidis remained viable on the air cell membrane in vitro for 17 days at 4, 20 and 30 °C. Thirty percent of the organisms also remained motile in albumen for 42 days at 25 °C and up to 5% of the cells remained motile for up to 20 days at 4 °C.

A collection of Salmonella enteritidis strains isolated in Switzerland (1965–90) was characterized. The phage type and plasmid profile of isolates were compared with the copy number and insertion loci of the DNA insertion element IS200. Three clonal lines of S. enteritidis were identified by IS200 profile; the various phage types were subtypes reproducibly associated with one of these lines. All human and poultry isolates contained a 38 Mda plasmid which hybridized with a mouse virulence-associated gene probe. In S. enteritidis, the IS200 profile is a race-specific molecular marker of the chromosome, and may be particularly applicable for studying the epidemiology of less common serovars.

Legionella isolates recovered in 21 different Spanish provinces over 8 years from both clinical (67 isolates) and environmental (181) samples, mostly from case-associated buildings, are described: 92·5% of clinical isolates were L. pneumophila serogroup 1 (SGI), only five isolates belonging to other species or serogroups: two L. pneumophila SG6, two SG8 and one L. bozemanii SG1 not clearly related with clinical infection.

L. pneumophila SG1 accounted for 53·6% of isolates from the environment, followed by SG8 (27·6%). SG3 (9·4%) and SG6 (7·2%). Three isolates were labelled as SG8/10.

Subtyping of L. pneumophila SG1 by the standardized panel of monoclonal antibodies revealed 90·3% of clinical and 78·3% of environmental isolates as belonging to Pontiac subgroup. Pontiac isolates were further divided into 55·3% Philadelphia 1 or Allentown 1, 21·9% Benidorm 030E and 20·4% Knoxville 1.

Characterization of samples from four outbreaks in which both clinical and environmental isolates had been recovered permitted the recognition of three Philadelphia 1 or Allentown 1 and one Knoxville 1 strains as the aetiological agents.

An outbreak of typhoid caused by Salmonella typhi of the same Vi-phage type (D1) and of the same antibiogram was reported in a large psychiatric institution in Singapore. A total of 95 (4·8%) of the 1965 inmates were infected, 47 with symptoms and 48 asymptomatic. Transmission was through close person-to-person contact and not through contaminated food or water. The source of infection could not be established. The outbreak was brought under control by maintaining a high standard of environmental sanitation, active search for fever and diarrhoeal cases, identification of asymptomatic cases by rectal swabbing, and isolation of those found to be infected. Mass immunization with two doses of heat-phenol inactivated typhoid vaccine was also carried out concurrently. The vaccine was found to have an efficacy of 65·8% in preventing clinical illness.

Epidemiological features of an outbreak of group B:15:P1.16 meningococcal disease (MD) in Frederiksborg country, Denmark, 1987–9, were investigated. The study comprised 149 cases notified during the outbreak and the two preceding years; 115 were confirmed by the isolation of Neisseria meningitidis. In 1989 the incidence had increased to 14·1 per 100 000 population. Among group B strains, B:15:P1.16 accounted for 80% (77/97). The overall mortality rate was 10% (15/149). Regarding cases due to group B:15:P1.16 strains a significant time-space clustering, which exclusively occurred within the 10–19 years age group, was demonstrated. The link between cases within clusters was indirect or unknown, except for ten patients with contact to one particular school. The prophylactic measures used included administration of rifampicin to household contacts. During the outbreak the proportion of secondary cases was high (6–15%). All secondary cases occurred outside the household indicating that the household had been protected.

Multilocus enzyme electrophoretic analysis was employed to assess the genetic relatedness of Neisseria gonorrhoeae. Based on the diversity of electromorphs at 9 enzyme loci, 16 electrophoretic types (ETs) were estabilished amongst the 65 isolates. The average number of alleles per enzyme locus was 1·7 and the mean genetic diversity per locus was 0·212. The majority of isolates belonged to either ET1 (32·3%) or ET2 (16·9%). No specific correlation of ETs was seen with serovars as the major types, ETs 1 and 2, were found distributed amongst the various serovars. Major serovars such as Bacjk (IB-1/2) and Bajk (IB-3/6) were each represented by 6 or 8 ETs respectively. Analysis of the genetic relationships of ETs to each other showed some clustering of subgroups that were more closely related than others.

The extended phage-typing scheme described for Campylobacter jejuni and Campylobacter coli has established 46 different phage types using 19 typing phages. Altogether 754 campylobacter isolates, 672 C. jejuni and 82 C. coli, isolated from human and non-human sources received from 17 different countries were phage-typed. Overall, 80·6% of the total isolates were typable. Among typable strains, 9 phage types (3, 5, 10, 11, 18, 19, 23, 26 and 44) represented 57·0% of the strains, 21·3% of the strains belonged to another 37 phage types and the remaining 2·3% of isolates were designated atypical. The most common phage type 11 (140/754) was frequently observed among C. jejuni isolates from human (113/561) and non-human sources (18/111). whereas type 44 was frequent among C. coli isolates from human (22/59) and from non-human sources (8/23). A study of the animal host-associations of common phage types showed that contaminated cattle and poultry appear to be the most common sources of human infection. The greatest variety of phage types was observed in Canada (24 phage types), followed by Portugal (17 types) and the UK (14 types), reflecting the larger sample sizes from these countries. Phage type 11 was encountered in 12 different countries and prevalence of other phage types varied from one country to another. The number of isolates typable with the scheme varied from 93·2% (261/280) in Canada to 61% (47/77) in Thailand. However, the number and diversity of phage types makes phage typing the method of choice in epidemiological studies of campylobacter infections.

An indirect ELISA developed for the serological detection of Salmonella typhimurium in chickens using lipopolysaccharide as detecting antigen has been evaluated further in experimental infections. Following oral infection of 24-week-old laying hens with an invasive strain of S. typhimurium, high titres of specific circulating IgG were induced which were maintained for 20 weeks. Similar IgG titres were found in egg yolk. When 4-day-old chickens were infected high antibody titres persisted for 45 weeks. Chickens inoculated orally or intramuscularly with different numbers of S. typhimurium organisms showed graded serum IgG responses to LPS. The IgG titres in experimentally infected in-bred lines of chickens which showed greater genetic resistance to salmonella infection were significantly lower than those found in more susceptible lines. Oral and intramuscular infection with 18 different types of enterobacteria, including avian pathogenic E. coli, Citrobacter spp., Klebsiella spp., Proteus spp. and citrobacter-like organisms possessing some salmonella LPS (none possessed the 0–4 antigen) and flagella antigens, did not induce S. typhimurium LPS-specific IgG responses. Chickens infected orally with rough or non-flagellate mutants of S. typhimurium did not induce high titres of LPS or flagella-specific IgG respectively. Sera obtained from S. typhimurium-infected chickens showed much higher titres against S. typhimurium LPS than with those antigens from other serotypes, including S. enteritidis.

Strains of Salmonella enterica serovar berta (S. berta) from Denmark and seven other countries have been characterized with the aim of developing a rational typing strategy in connection with outbreak investigations.

Biotyping divided the strains into H2S-positive (90%) and H2S-negative (10%) biovars. Six percent of the strains were resistant to one or more antimicrobial agents. Eighty-eight percent of the strains carried plasmids and 52 different plasmid profiles were recognized. Six of the common plasmid sizes in these profiles were shown by restriction enzyme analyses to contain more than one plasmid species. More than 90% of the strains had the same ribotype with the restriction enzymes Sma I and EcoR I and the same whole cell protein profile. Outer membrane protein profiles and isoenzyme profiles were identical in all S. berta analysed.

Plasmid profiling in combination with restriction enzyme analysis of plasmids seemed to be the most rational typing strategy for S. berta. The results indicated that S. berta strains regardless of geographical source or host are possibly clonal in nature.

Fifty–two strains of Helicobacter pylori were examined by DNA restriction endonuclease digestion, ribosomal (r)RNA gene probe hybridization and bio–typing. Most (49) strains originated from gastric (antral) biopsies of patients before or after elective surgery for duodenal ulcers. Chromosomal DNA Hind III ribopatterns showed 9 strain clusters of which the largest contained 12 strains each with 3 common bands (1·50, 3·45, and 4·26 kb) but which were heterogeneous with respect to biotype and total digest pattern. Isolates from post–operative patients with either healed or recurrent ulcers showed ribopattern heterogeneity and exhibited a similar distribution of H. pylori ribopattern types; no single type predominated in any patient group or was more highly associated with recurrent ulcers than with healed ulcers. Multiple isolates from two surgical patients had only minor genomic variations in each set whereas isolates from two brothers had different ribopatterns. We conclude that Hind III ribopatterns in conjunction with total digest patterns might provide the basis for future epidemiological typing studies.

The faecal Escherichia coli flora was studied in 89 infants. Each infant was followed with a mean of 12 faecal samples (range 5–21) between 0 and 18 months of age. All isolates were assayed for P fimbriae and biochemically phenotyped and the persistence of each strain (phenotype) in the infant's gut was determined. In a subset of strains the occurrence of type 1 fimbriae and adherence to HeLa cells was studied. Thirty-one per cent of isolates belonging to strains colonizing for longer than 6 months expressed P fimbriae compared to 19% of the isolates from strains colonizing 1–6 months or transient strains colonizing less than 1 month. Type 1 fimbriae and adherence to HeLa cells occurred similarly often in all groups of strains. We conclude that P fimbriae, but not type 1 fimbriae or HeLa cell adherence seemed to contribute to the ability of the E. coli strain to colonize the human intestine.

Faecal swabs obtained from a random sample of 1131 cows and 659 calves on 100 southern Ontario dairy farms were examined for verocytotoxigenic Escherichia coli (VTEC) using a Vero cell assay. Five isolates from each positive culture were tested similarly. Positive colonies were examined with DNA probes for Shiga-like toxin I (SLT-I) and SLT-II sequences. Probe-negative colonies were tested for neutralization of verocytotoxicity using anti-SLT-I and anti-SLT-IIv antisera. Colonies showing no neutralization response were examined in a polymerase chain reaction procedure. Colonies positive by any test were confirmed to be E. coli biochemically, serotyped, biotyped and tested for antimicrobial resistance. Faecal culture supernatants which were positive in the Vero cell assay, but culture negative, were examined using the neutralization assay. Animals were classified positive by faecal culture supernatant or by positive VTEC isolate. The prevalence rates of VTEC infection in cows and calves were estimated to be 9·5 and 24·7%, respectively. The proportion of animals infected on each farm ranged from 0 to 60% for cows and 0 to 100% for calves. Of 206 VTEC isolates identified, few were of serotypes which have been isolated from humans and none were E. coli O 157. H7.

We determined the natural history of the colonization of our hospital's potable water by culturing water approximately biweekly from 20 sites throughout the hospital for 4 years. Overall, 545 (24.7%) of the 2200 samples grew Legionella pneumophila. During hyperchlorination, 11·7% of the samples were positive while 41·6% were positive in the absence of chlorination. There was no seasonal trend towards positivity, but there was marked inter-site variation in the semi-quantitative culture results. However, a single strain of legionella (as defined by plasmid profiling) tended to persist at a site. Such a site was a unique ecological niche in that different sites in the same wing were populated by distinct strains.

The two wings of our hospital had a significantly different distribution of strains of legionella – plasmid profile type III predominated in the Victoria Wing while types II and VI predominated in Centennial Wing. Twenty-four of our 28 cases of nosocomial Legionnaires' disease occurred in the Centennial Wing. Three of the four cases in the Victoria Wing were caused by plasmid profile type III while 18 of the 24 isolates from patients who acquired their infection in the Centennial Wing were type II. We conclude that each water outlet serves as its own ecological niche of L. pneumophila.

A 12-month survey on the incidence of campylobacter infection in 1217 patients with diarrhoea was carried out in Jeddah, Saudi Arabia. Campylobacters were isolated from 55 (4·5%) patients, second in prevalence to salmonellas (6·2%). Shigellas were isolated from 4·2% of patients. Campylobacter isolation rates were high in children of all ages, as well as in young adults (36·5% of all isolates were from adults aged 20–39 years). Isolation rates peaked in September and November. Analysis of the results showed that 69% were Campylobacter jejuni (mostly biotype IV) and 31% C. coli. Serogroups 5 and 23 (Penner scheme) and phage type 125 (Preston scheme) were most frequently isolated. Resistance to erythromycin and tetracycline was observed in 7·3 and 32·7% of the isolates. Campylobacters are an important cause of bacterial enteritis in Saudi Arabia, both in adults and in children, and should be sought routinely.

Greek military recruits (993) were examined for carriage of meningococci during July 1990. Blood, saliva and throat swab specimens were obtained and each recruit answered a questionnaire providing information on age, education (a measure of socioeconomic level), place of residence, smoking habits and recent infections.

The overall carriage rate was 25% but differed between the two camps: 79/432 (18%) in Camp A and 168/561 (30%) in Camp B (P < 0·0005). In Camp B, there were significantly higher proportions of recruits who were non-secretors (P < 0·0005), and/or heavy smokers (P < 0·0005). They were also younger ( < 19 years old) (P < 0·001), and on the whole had fewer years of education (P < 0·0005). By univariate analysis, carriage was significantly associated with smoking. By multiple logistic regression analysis, carriage was associated with smoking (P < 0·001), age (P < 0·01) and the camp in which the recruits were based (P < 0·01). Among recruits in Camp B, 15/38 (40%) of those with recent viral infections were carriers compared with 30% for the camp in general.

Salmonella arizonae are rarely isolated in the UK. Since 1966 there have been sixty-six isolates from humans of whom 35% gave a recent history of foreign travel. Terrapins and snakes are potential sources of infection.

An outbreak of salmonellosis in calves was monitored for persistence of Salmonella typhimurium excretion in faeces and the effect of treatment with apramycin. Prior to treatment apramycin-resistant Escherichia coli were present but all S. typhimurium isolates were sensitive. Following the treatment of six calves with apramycin, apramycin-resistant S. typhimurium were isolated from two treated calves and one untreated calf. Plasmid profiles of E. coli and S. typhimurium were compared and plasmids conferring resistance to apramycin and several other antibiotics were transferred by conjugation in vitro from calf E. coli and S. typhimurium isolates to E. coli K-12 and from E. coli to S. typhimurium. The plasmids conjugated with high frequency in vitro from E. coli to S. typhimurium, and hybridized to a DNA probe specific for the gene encoding aminoglycoside acetyltransferase 3-IV (AAC(3)-IV) which confers resistance to apramycin, gentamicin, netilmicin and tobramycin.

Infectious diarrhoea is common in young Australian Aborigines [1–3] and is one of the main causes for their unsatisfactory health standards with consequent widespread failure to thrive and undernutrition [4–5]. Most published reports relate to patients in hospital or to hospital admission statistics and give little indication of the extent or severity of diarrhoeal disease in children in Aboriginal communities.

The present investigation involved more than 100 Aboriginal children up to 5 years of age living in remote communities in the tropical north of Western Australia who were studied prospectively over a 12–month period.

A discrimination index was applied to assess the value of biotyping and resistotyping, used alone or together, for the subspecific discrimination of Escherichia coli. The index was high when 599 strains from a wide variety of sources were examined by full biotyping with 10 tests. Although the discrimination achieved was lower when a sub-collection of 333 strains was examined, that finding probably indicated that many of the latter strains were of urinary origin and represented a limited number of uropathogenic clones. Combined biotyping and resistotyping provided a higher level of strain discrimination than either method used on its own. Results suggest that these typing methods may be used with confidence for the discrimination of strains of E. coli.