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.

The action of two antibiotics, penicillin and chloramphenicol, on bacterial growth and endotoxin liberation was studied in 18 strains of Neissevia meningitidis isolated from blood and CSF of patients with meningococcal infections. The antibiotics were administered both separately and in combined form in doses equivalent to 1 MIC and 100 MIC. Penicillin was found to produce a faster and more intense bactericidal effect than chloramphenicol during the first hour, whereas at 12 h these differences were not significant. This could explain the initial worsening observed in some infected patients when large doses of penicillin are administered. An increased liberation of endotoxin after adding penicillin was observed in six of the strains studied, whereas the remaining 12 did not show significant increases. The six strains (belonging to serogroup B) were known to have an enhanced capacity for spontaneous endotoxin liberation.

Over 5700 hens eggs from 15 flocks naturally infected with Salmonella enteritidis were examined individually for the presence of the organism in either egg contents or on shells. Thirty-two eggs (0·6%) were positive in the contents. In the majority, levels of contamination were low. Three eggs, however, were found to contain many thousands of cells. In eggs where it was possible to identify the site of contamination, the albumen was more frequently positive than the yolk. Storage at room temperature had no significant effect on the prevalence of salmonella-positive eggs but those held for more than 21 days were more likely (P < 0·01) to be heavily contaminated. In batches of eggs where both shells and contents were examined, 1·1% were positive on the former site and 0·9% in the latter.

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.

The main objective of this study was to assess whether the capacity of Neisseria meningitidis to release endotoxin depends upon the type of strain or upon bacterial mass. Endotoxin release was studied in 32 strains isolated from patients with meningococcal infections and in 49 from asymptomatic carriers, using a quantitative test (limulus test with a chromogenic substrate). The results show that the strains from patients release significantly higher amounts of endotoxin than strains from carriers regardless of serogroup and isolation site. No correlation was found between stage of bacterial growth and the amount of endotoxin liberated. These findings suggest that endotoxin liberation is a characteristic of certain strains of N. meningitidis and is not determined simply by bacterial mass.

Between November 1988 and January 1989, a total of 155 people in 36 reported outbreaks suffered gastrointestinal symptoms associated with eating Stilton cheese, produced from unpasteurized cow's milk in the English midlands. Symptoms were suggestive of a staphylococcal illness but extensive laboratory testing of cheeses implicated in several of the outbreaks failed to detect any pathogen, toxin or chemical. Control measures were implemented, and included a voluntary withdrawal of the implicated Stilton cheese from sale on 23 January 1989 and a subsequent decision to use pasteurized milk in production of the cheese.

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.

Over a 2-year period, 25 families comprising of 181 individuals of all ages were longitudinally observed for the excretion of Campylobacter species. Faecal samples were taken from all persons with diarrhoea. Specimens were also taken from apparently healthy individuals and from domestic animals living within the confines of the study families at monthly intervals.

The overall diarrhoea attack rate was 19 episodes per 100 person-years with peak incidence in the 1- to 4-year-old age group (76/100 person-years). Eight (11·5%) of the total episodes were campylobacter-associated and the overall rate of campylobacter positive diarrhoeal episodes were 2·2 per 100 person-years. Of the 1002 stool samples from healthy individuals 32 (3·2/100 samples) were positive for campylobacter. The organism was most frequently isolated from children under 1 year of age both during diarrhoeal episodes (11·5 per 100 person-years) and non-diarrhoeal (11·1 per 100 samples). Multiple infections in a family were rare. In 19·4% of the occasions one or more animals were campylobacter positive. However, only in 7·7% of these occasions was a human infection recorded within 1 month after the animal was found to be positive.

The study showed that the epidemiology of campylobacteriosis in this community was distinct compared to that observed in developed countries.

In the development of a surveillance programme for infectious diseases in Belgium, a national network of microbiological laboratories has been responsible, since February 1983, for the weekly registration of certain pathogenic agents. Thus, the main epidemiological features of a selected number of infections in Belgium can be characterized.

In order to elucidate the effect of ceftriaxone therapy on the morphology of gut microflora, 11 human volunteers were treated with ceftriaxone, 1 g daily, given intramuscularly in one dose. Treatment continued for 5 days. Faecal microflora was analysed by digital image processing before, during and after the treatment period.

We derived simple numerical parameters which describe the morphologic composition of the flora. They were significantly influenced by the antibiotic, and returned to their baseline values more than 7 days after treatment was stopped. The procedure holds promise for clinical application.

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.

It had already been shown with a single virulent strain (A42) of Fusobacterium necrophorum that suspension of the fusobacteria in sub-lethal doses of broth cultures of other bacteria reduced the minimum infective dose (> 106 organisms) for mice by subcutaneous inoculation, sometimes to < 10 organisms. The present study extended the known range of bacteria with strong infectivity-enhancing properties to include Bacillus cereus, Klebsiella oxytoca and Staphylococcus aureus; and of those with weaker effect to include Bacillus subtilis, ‘Bacteroides melaninogenicus’, Clostridium sporogenes, Pasteurella haemolytica, and Proteus mirabilis.

The study also showed that five further virulent strains of F. necrophorum closely resembled A42 in respect of striking susceptibility to infectivity enhancement by Escherichia coli, Actinomyces (Corynebacterium) pyogenes and S. aureus. One further strain (A6) of F. necrophorum resembled A42 in respect of strong infectivity enhancement by A. pyogenes, S. aureus, B. cereus and K. oxytoca but differed from it and the other five strains in being only slightly affected by E. coli.

This work was a necessary prelude to the development of a method, based on infectivity enhancement, for the detection and isolation of F. necrophorum present in small numbers in heavily contaminated material such as faeces.

The isolation of Fusobacterium necrophorum present in small numbers in heavily contaminated material such as faeces or soil is hampered by the lack of an efficient selective medium and by the high minimum infective dose of the organism. A sensitive method for the detection and isolation of faecal strains of F. necrophorum type A was based on the subcutaneous injection of faeces, suspended (5% w/v) in broth culture of Actinomyces (Corynebacterium) pyogenes or Staphylococcus aureus to increase fusobacterial infectivity, into mice pretreated with clostridial antitoxins. When necrobacillosis developed F. necrophorum was identified microscopically in tissue from the advancing edge of the lesion and isolated on a partly selective medium.

The enhancement of fusobacterial infectivity produced by A. pyogenes and by S. aureus was high, but the latter was slightly the more efficient, enabling as few as 80 F. necrophorum organisms/g of faeces to be detected.

Use of the method showed that 3 of 16 wallabies had F. necrophorum in their faeces at the time of examination. Numerous epidemiological applications are suggested.

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.

We conducted a 4-year retrospective cohort study to better define the risk of haemolytic anaemia and haemolytic uraemic syndrome (HUS) in children following sporadic gastrointestinal infection with the O 157.H7 serotype of Escherichia coli. Of the 72 children infected with this organism, 9 (12·5%) developed haemolytic anaemia, 6 of whom had HUS. No child in a cohort of 72 age-matched controls with Campylobacter jejuni gastroenteritis developed haemolytic anaemia (P = 0·003). Females had a significantly greater risk of developing haemolytic anaemia after E. coli O 157.H7 infection than did males (8/29 females v. 1/43 males; P = 0·003). In a logistic regression model, female gender emerged as the only statistically significant risk factor for haemolytic anaemia (odds ratio 3·85; 95% confidence interval 1·24–12). These results are consistent with recent reports of a moderate increase in the risk of HUS for females.

Esterase electrophoretic typing and restriction fragment length polymorphism of ribosomal DNA regions (ribotyping) were used to differentiate 102 Pseudomonas aeruginosa clinical isolates obtained from chronic lung infection in 23 patients with cystic fibrosis (CF) and two reference strains (including the type strain ATCC 10145). Twenty-five zymotypes were obtained with the former method and 16 ribotypes with the latter. Combination of the two typing systems led to the finding of 30 different types. Our data highlights the physiopathological complexity of P. aeruginosa infection in CF as, in six individual cases, several types were found among isolates from a given patient. On the other hand, two unique types were found in two and three patients respectively, raising the possibility of crossinfections.

The performance of agar-contact plates and an alginate-swab method for sampling food surfaces before and after cleaning was compared. Contact plates were more convenient, and were at least as sensitive as the swabbing method. To assess cleaning efficiency repeated sampling was carried out in selected premises, and several cleaning methods were introduced for trial periods. Some surfaces, notably wood and polypropylene, were particularly difficult to clean. For these scrubbing with a nylon brush was the best method. Other surfaces were more easily cleaned, and generally the methods introduced as part of this study were better than the original method used in the premises. Paper proved to be unpopular, and cleaning solutions applied with it did no better than those cleaned with a multiuse cloth kept soaking in a detergent and hypochlorite solution.

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.

A slide agglutination (SA) test was developed to determine the serogroup of isolates of Treponema hyodysenteriae of serogroups A to F. Rabbit antisera which are normally used for serogrouping T. hyodysenteriae in an agarose gel doublediffusion precipitation test (AGDP) were not suitable for SA because they agglutinated isolates from more than one serogroup. The agglutination reaction was made serogroup-specific by cross-absorbing the typing sera for serogroups A to F with whole treponemes from the other 5 of these 6 serogroups of T. hyodysenteriae. The absorbed sera were reacted in slide agglutination tests with 33 isolates of T. hyodysenteriae and with four non-T. hyodysenteriae intestinal spirochaetes. None of the non-T. hyodysenteriae isolates agglutinated, but 27 of the 33 isolates of T. hyodysenteriae did. The results for 26 of the 27 agglutination reactions agreed with the serogroup as determined in AGDP. One of the 6 isolates of T. hyodysenteriae which failed to react in slide agglutination was of serogroup B, 1 of serogroup D, 1 each were from new serogroups G, H and I, and 1 was untypable in AGDP.