Between February 1988 and March 1989 chicken carcases delivered to the kitchen of a long stay psycho–geriatric hospital were screened every week for salmonella contamination. While 214 of 477 (45▒) individual carcases carried one or more salmonella types, every single consignment examined contained affected carcases.

Simultaneously sewers draining the residential accommodation and excluding kitchen effluent, were also monitored. Thirty out of 79 (38▒) of Moore's swabs were positive for salmonella. There was a statistically significant association between the salmonella types isolated from chicken and those isolated from sewers the following week.

Following a change in kitchen policy to order only cooked chicken there was a significant reduction in the isolation of salmonella from the sewers.

Since 1987, the number of cases of salmonellosis caused by Salmonella enteritidis has considerably increased in Western Europe. Comparison of endemic animal strains isolated in Belgium from 1976–84 with strains isolated from 1987 on shows that the strains which cause the current epidemic have no features distinguishing them from the previously–isolated strains and that furthermore, they do not constitute a bacterial clone. They belong to 13 different lysotypes and in most cases remain sensitive to antibiotics. Nevertheless, the lysotype 33 which belongs to the phage type 4 [1] has increased significatively. It encompasses 37 % of the animal strains isolated in Belgium from 1987–9, but only 7% of the strains isolated from 1976–84.

It is worth noting that the endemic as well as the epidemic strains contain a virulence plasmid sharing sequence similarities with the FIB and FIIA plasmid replicons and with the VirA and VirB virulence regions of the S. typhimurium virulent plasmid: pIP1350.

Of 2210 salmonella isolates referred to the New Zealand Communicable Disease Centre for epidemiological surveillance during 1987, 147 (6·7%) were resistant to one or more of 10 antibiotics. Resistance to streptomycin was most common (4·5%). followed by sulphamethoxazole (3·4%), tetracycline (3·3%), ampicillin (1·5%). and kanamycin (1·4%). Resistance to cephalothin, chloramphenicol, gentamicin and trimethoprim occurred in less than 1 % of isolates. There was no resistance to norfloxacin. Isolates from human sources were significantly (P < 0·001) more resistant (10%) than those from other sources (3·2%). The majority of resistant isolates were resistant to more than one antibiotic, but multiresistance to five or more antibiotics occurred only among human isolates. Comparison of these results with data from earlier years shows that there has been little change in the incidence of resistance among salmonella in this country over the last 10 years. The prevalence of antibiotic resistance among salmonella in New Zealand is low relative to many other countries.

The distribution of Salmonella enteritidis phage types in Canada is described; 606 of 674 strains examined were of human origin. Typable strains of all sources, constituted 99·6% (671/674) of all strains examined, and were representative of 15 different phage types. Five phage types (8, 13, 4, 13a and 1) accounted for 92·4% of the total. Phage type 8 consistently showed the highest incidence in human (69·96%) and non-human (72·05%) sources and appeared to be the most common in North America. Phage type 4, the most prevalent in the UK, is infrequent in Canada (38/674). The distribution of phage types showed regional variation among infrequent phage types, whereas the common type, 8, was observed in different frequencies in all provinces. Examination of 29 outbreaks of S. enteritidis representing 254 isolates for humans revealed 5 different phage types, the highest number of outbreaks (11) were type 8. A study of these outbreaks and the animal-host-associations of the common phage types, 8 and 13, indicated that contaminated poultry appeared to be the most common source of human infection in Canada.

When Specific Pathogen–Free hens were infected with Salmonella enteritidis PT4 by direct administration into the crop, the age of the bird at infection was found to have an effect on both pathogenesis and antibody response. Birds at 20 weeks of age showed no adverse signs and developed high titres of antibodies of the IgM class, while those which were 1 year old at infection developed relatively little antibody arid had acute septicaemia, with 6 of 10 birds either dying or having to be humanely destroyed. The implication of these results for the control of salmonella infections in poultry is discussed.

The main aim of this study was to measure and explain geographic variations in the incidence of Legionnaires' disease in Scotland, particularly to help understand the source of non–outbreak infection.

Between 1978 and 1986 the overall mean annual incidence rate was 7·9 per million (range 3·1–20·2), and for non–outbreak, non-travel cases it was 5·6. There were geographical variations by health board, by city and within cities, e.g. the mean annual incidence rate per million for non–travel, non–outbreak disease was 1·2 in Tayside Health Board, 3·7 in Lanarkshire, 5·6 in Lothian and 14·4 in Greater Glasgow. In Greater Glasgow Health Board non–travel cases lived in and around the city centre and in some postcode sectors there, the mean annual incidence rate exceeded 100. Travel–related cases lived in peripheral areas.

These variations could not be explained by differences in access to and use of diagnostic services, surveillance, or host susceptibility (as reflected by socio–economic status and frequency of other respiratory disease). The explanation probably lay in environmental factors, though differences in agent virulence were not excluded.

The two main conclusions are, that non–outbreak cases were not truly sporadic, and that the spacetime variations in incidence support the hypothesis that cooling towers were an important source of infection for not–nravel, non-outbreak cases. If so such infection is potentially preventable.

Two collections of trimethoprim R plasmids, isolated from strains of Escherichia coliduring 1978–83 and 1987–8 respectively, were retrospectively screened with specific biotinylated DNA probesfor the presence of genes encoding particular DHFR enzymes. The results confirmed that the type I DHFR gene was the predominant plasmid-encoded gene conferring trimethoprim resistance in strains of E. coli from the Nottingham area of the UK, but indicated that genes encoding the more recently recognized types of DHFR enzymes haappeared in the bacterial gene pool and could be recognized with increased frequency in the latter plasmid collection. Thiswasparticularly true of the type IIIa and type VII enzymes which together accounted for 27 % of the trimethoprim R plasmid examined in 1987–8.

The cell-surface hydrophobicity of 100 urinary isolates of Staphylococcus saprophyticus, cultured from symptomatic females in the general population, was assessed using a two-phase aqueous: hydrocarbon system. Relatively strong cell-surface hydrophobicity was exhibited by 79 isolates using the criteria employed, while only 2 of the remaining 21 isolates failed to demonstrate any detectable hydrophobicity. Cell-surface hydrophobicity may be a virulence factor of S. saprophyticus. important in adherence of the organism to uroepithelia. Additionally, the data support the concept that cell-surface hydrophobicity may be a useful predictor of clinical significance of coagulase-negative staphylococci isoated from clinical sources.

A hospital-based case-control diarrhoea survey was conducted in Cairo. Egypt to determine the age-specific frequency of campylobacter infection among diarrhoeic and non-diarrhoeic children aged new born to 5 years. Campylobacter was the most common bacterial enteropathogen isolated from diarrhoeic stools. The overall prevalence of campylobacter isolations was 25·9% from stools of 143 diarrhoeic children compared to 15·2% of 132 non-diarrhoeic control children (P = 0·028) during the 4-month period of study. Children less than 1 year of age were at greatest risk of campylobacter infection with 32·6% of diarrhoeic patients culture positive, compared to 14·3% of controls. Asymptomatic shedding in controls was positively associated with a recent diarrhoeal episode (P = 0·019) and may be an important source of new infections.

Diarrhoeal diseases are primary contributors to millions of deaths annually. Yet, little is known about the evolutionary reasons for the differences in virulence among gastrointestinal pathogens. Applying the comparative, cost/benefit approach of evolutionary biology this paper proposes that waterborne transmission should favour evolution towards high virulence. This hypothesis is supported by a cross-specific test, which shows that waterborne transmission is strongly correlated with the virulence of bacterial gastrointestinal pathogens of humans. Alternative explanations of this correlation are not supported by available data. These findings bear on public health policy because they draw attention to a previously unrecognized long-range benefit gained from purification of water supplies: diarrhoeal pathogens may evolve to lower levels of virulence.

More than 12800 clinical isolates from 115373 in-patient specimens obtained at the Sir Charles Gairdner Hospital, Perth, Western Australia, were identified and analysed statistically for relationships with usage of three generations of cephalosporins over the 5-year period from July 1984 to June 1989. A positive relationship between cephalosporin usage and significantly increasing isolation rates for those species capable of producing chromosomal β-lactamases was observed. Simultaneously, a small increase in the isolation frequency of non-chromosomal β-lactamase-producing strains was noted and no correlation with cephalosporin usage was demonstrated. The trend toward predomination in the hospital environment of strains possessing substantial cephalosporin resistance has implications for future antimicrobial policy, choice of empiric therapy and the predictive value of standard antimicrobial susceptibility tests.

Between 1 October 1986 and 31 March 1987, 55 cases of meningococcal disease were identified in the South-West of England, an attack rate of 1·54 per 100000 during the study period. Antibiotics used in the treatment of the disease successfully eliminated nasopharyngeal carriage of meningococci in 13 out of 14 cases without use of rifampicin. The overall meningococcal carriage rate in 384 close contacts was 18·2% and the carriage rate of strains indistinguishable from the associated case strain was 11·1%. The carriage rate of indistinguishable strains in household contacts (16·0%) was higher than the carriage rate in contacts living at other addresses (7·0%, P > 0·05). A 2·day course of rifampicin successfully eradicated meningococci from 46 (98%) of 47 colonized contacts.

In one third of cases groupable meningococci were isolated from at least one household contact; 92% of these isolates were of the same serogroup as the associated case strain. When a meningococcus is not isolated from a deep site in a clinical case of meningococcal disease, culture of serogroup A or C strains from nasopharyngeal swabs of the case or of household contacts is an indication that the close contact group should be offered meningococcal A + C vaccine in addition to chemoprophylaxis. The failure in this and other studies to isolate meningococci from any household contact in the majority of cases may be due either to the relative insensitivity of nasopharyngeal swabbing in detecting meningococcal carriage or to the acquisition of meningococci by most index cases from sources outside the household.

Since 1984 a change in the epidemiological pattern of meningococcal disease in Italy has occurred with a predominance of Neisseria meningitidis of serogroup C (76%), serotype 2a and a high proportion of strains resistant to sulphonamides (71%). In order to understand better the epidemiology of the group C N. meningitidis strains responsible for the disease over the last years in Italy, we studied the genetic features of phenotypically closely related strains, by enzyme electrophoresis. The results showed that the genetic and the phenotypic characteristics of the 57 strains studied were similar, suggesting the spread of a single clone during recent years in our country.

This result is in agreement with the circulation of strains typical of epidemic situations, despite the decreasing incidence of meningoccal disease in Italy.

The possibility of micro-epidemics of severe leptospirosis occurring on the island of Barbados was investigated by examining the space-time clustering of the disease in 212 laboratory-confirmed cases admitted to Queen Elizabeth Hospital, Bridgetown, over a 7-year period. A series of 109 patients with symptoms compatible with leptospirosis but shown to be otherwise by laboratory examination were also examined for comparison. No significant space-time clustering was found among the leptospirosis cases, indicating no evidence for micro-epidemics. By comparison, statistically significant clustering was apparent among the smaller non-leptospirosis series. Possible explanations for the absence of observed micro-epidemics of leptospirosis are discussed.

About 2·3% (16/700) of faecal specimens from renal transplant recipients and patients having home haemodialysis as well as patients attending their general practitioners with symptoms of gastroenteritis yielded Listeria species 40% of positive faeces contained more than one Listeria species or serovar. The proportion of positive specimens was similar in all three patient groups. Listeria were isolated from 5·6% (10/177) of renal transplant recipients on one or more occasions over the period of a year. The commonest species was L. monocytogenes and type 4b the commonest serovar. Carriage was more common in July and August than other times of year, and less than 28 weeks in duration. In renal transplant recipients carriage was positively related to treatment with ranitidine, consumption of more than three types of cheese in the previous 20 months, and consumption of English cheddar cheese more than once per week.

Sentinel herds at 34 farms were used to study the epidemiology of bluetongue and related orbiviruses in Oman. The results indicate that bluetongue virus (BTV) is widespread and is enzootic in Northern Oman. At least three BTV serotypes (3, 4 and 22) were present at the time of the study. Antibodies to epizootic haemorrhagic disease of deer virus (EHDV) type 2 and EHDV-318 were also detected but were less prevalent. Entomological investigations identified the presence of 16 species of Culicoides. The peak seasonal incidence of the BTV vector C. imicola and the EHDV vectors C. schultzei (group) midges at Rumais in Northern Oman correlated closely with the spring rains in that area. However, both species of midge were also present in lower numbers throughout the year. Four species of Omani midge, C. arabiensis, C. ibriensis, C. neoschultzei and C. buettikeri are new to science.

Embryonated chicken eggs were used as a model for assessing the teratogenic potential of several Palyam serogroup orbiviruses. Infection of 4-day-old embryonated chicken eggs via the yolk sac with eight of the viruses resulted in deaths or congenital deformities which included retarded development, arthrogryposis and reduced feathering. Statistical analysis showed that the viruses could be divided into three groups: those that caused death (Gweru virus isolates 866/77 and 1726/7776 and Apies River virus), those that caused deaths only when large amounts of virus were inoculated (Gweru isolate AR11869 and Marondera virus) and those that caused death and deformities (Abadina, Kasba, Nyabira, Petevo and Vellore viruses). Differences in pathogenic potential were noted between isolates identified as the same serotype by serological tests.

Human rotavirus isolates from 1100 stool samples were analyzed by polyacrylamide gel electrophoresis, and 48 different migration patterns were detected. Heterogeneity in the migration of segment 10 was observed in both long and short electropherotypes in which three long and two short patterns were identified. In spite of these variations all short and long electropherotypes were subgrouped by enzyme immunoassay as subgroups I and II respectively. Mixed infections were detected in 17% of cases and the subgrouping correlated with the corresponding electropherotypes. The same electropherotypes were present in severe, mild and asymptomatic cases and no electropherotype was particularly associated with greater virulence. Furthermore, the electropherotypes isolated from nosocomial asymptomatic cases were the same as those detected from those admitted with severe diarrheoa. It seems unlikely that electropherotyping can be used to identify more virulent strains of rotavirus.

An outbreak of hepatitis A involved more than 50 residents of a group of villages in the late spring and summer of 1989. The only food that was common to all the laboratory-confirmed cases was bread, purchased either unwrapped or as rolls, sandwiches or filled rolls, and supplied either directly from one shop or indirectly through its subsidiary outlets. It was concluded that this bread was the most likely vehicle of transmission of the hepatitis A virus and that the bread was contaminated by soiled hands which were inadequately washed because of painful skin lesions. Comprehensive control measures were successful in limiting further spread of the infection. This outbreak highlights the transmissibility of hepatitis A virus on food. The use of disposable gloves when handling food which is to be consumed without further cooking would prevent transmission of this or other infectious agents by this route.