The supernatant fluids of batch and continuous cultures of Brucella strains contained up to 100 mg/i of soluble RNA which could be recovered by precipitation with lysozyme. This RNA fraction had many of the properties of ribosomal RNA and was single-stranded, sensitive to ribonuclease, with an approximate sedimentation constant of 5S, a molecular weight of about 35000 daltons and an adenine; guanine; cytosine; uracil content of 17·5 26·5 33; 23 mol% respectively. RNA fractions from lysozyme precipitates evoked high titres of Brucella agglutinins on injection into rabbits and induced acute inflammatory responses in guinea-pig skin. Highly purified RNA fractions prepared by phenol extraction of lysozyme precipitates did not evoke antibodies to Brucella abortus.

A deterministic model to compare various control strategies for parasites having two hosts is presented. When applied to Echinococcus granulosus, Taenia hydatigena and T. ovis, the model shows that maximum progress would be achieved when both the difinitive and the intermediate host are treated simultaneously. This type of model may prove of value in studies on the control of other towhost parasites.

The influence of pH arid temperature on the efficiency of chlorine inactivation of two unrelated picornaviruses in a typical urban wastewater effluent was examined. Temperature, unlike pH, had relatively little effect on the rate of inactivation. The pH effect was complex and the two viruses differed. The f2 coliphage was more sensitive to chlorine at low pH, but at all values there was a threshold above which additional chlorine resulted in very rapid inactivation. The amount of chlorine required for this was less at low than at high pH, although at pH values above 7 the extent of inactivation was about the same. There was no apparent correlation between pH and rate of inactivation of poliovirus but there was a suggestion that at a pH close to the isoelectric point of the virus it was less sensitive to chlorination.

A split-product influenza A vaccine which contained an influenza B strain (B/Hong Kong/8/73) and two influenza A strains, antigenically identical with A/Fort Dix/741/76 (HswlNl) and A/Victoria/3/75 (H3N2), was offered to personnel of the CPHL. Changes in the antibody status were followed with serum samples collected from 153 participants on the day of vaccination and 1, 13 and 18 months thereafter. During the two epidemic seasons in the trial period there were only four serological influenza A infections (2·6%) among the vaccinees. This is one eighth of the corresponding infection rate (22%) in the general population estimated on the basis of other indices.

The vaccinees' antibody response was strongly influenced by the age of the individual subjects. During the trial period the decrease in the antibody titres slowed down. The geometric mean titres of homologous HI antibodies were still substantially higher at the end of the period than at the beginning. This also applied to heterologous antibodies against H1N1 viruses in persons born between 1926 and 1952. In participants born after 1952, the vaccine was not able to evoke these antibodies, and in participants born in or before 1925 the boosting effect was poor.

Bromine chloride, chlorine and peracetic acid inactivated f2 coliphage in effluent but in order to achieve 99·99% inactivation the three disinfectants were required at about 1, 10 and 100 mg/l respectively. The activity of chlorine was halved by the presence of added organic matter, whereas bromine chloride and peracetic acid were very little affected. When a second successive dose of virus was added to the reaction mixture, the virus was inactivated only by peracetic acid despite the fact that in the chlorine-treated effluent residual chlorine was detected. The addition of a second dose of disinfectant inactivated residual virus in the same way as the first dose.

A large outbreak of streptococcal skin infection occurred late in the summer of 1978 in a factory which undertakes the slaughter, preparation and packing of chickens. In all, 103 episodes of infection occurred in 82 workers from a total factory establishment of 347. The highest incidence of infection was in the packing department where there was an attack rate of 44 %. The routes of introduction of infection into and spread within the factory remain mostly unknown. Following the identification of cases and carriers and the institution of appropriate treatment and control measures the outbreak quickly declined. The responsible organism in the outbreak was Streptococcus pyogenes T-type 3/1 3/B3264, provisional M-type ‘R78/55’. This is the first poultry factory outbreak in England to be reported.

The changes in the titres of immunoconglutinin (IK), conglutinin and heterophile antibodies were measured in calves vaccinated with Br. abortus Strain 19. The IK titres rose rapidly following vaccination but returned to normal within ten weeks.

A survey of the sera of over 300 cattle showed no significant correlation between the Brucella STA titre and of these ‘non-specific’ indicators. It is concluded that they are of little assistance in the serodiagnosis of brucellosis.

Fifteen strains of Escherichia coli which had been collected in previous studies from animals and meat were studied.

They belonged to serotypes considered enterotoxigenic and were examined for the production of the heat-labile and heat-stable enterotoxins. Only one of these strains (O8. Hnt) isolated from a Cheshire produced heat-labile enterotoxin. Another strain (O8.H9) isolated from a cowpat in another part of Cheshire gave results suggesting production of small amounts of the heat-stable enterotoxin. The ecological aspects of these results are discussed.

One hundred and ninety-eight prostitutes (mean age 41·8 years) and 117 control women of low socio-economic class (mean age 43·8 years) were tested by solid-phase radioimmunoassay for hepatitis B surface antigen (HBsAg), its antibody (anti-HBs) and antibody to hepatitis B core antigen (anti-HBc). The prevalence of HBsAg was higher among prostitutes (11% v. 4%, P ∼ 0·06). This difference was accounted for by the higher infection rate of prostitutes to hepatitis B virus (HBV) (97% v. 45%, P < 10−6), since the proportion of HBsAg carriers among those infected was practically the same between the two groups (11% v 9%). Among the previously infected prostitutes who did not become carriers the majority (75%) were positive for both anti-HBc and anti-HBs, whereas among control women about half (52%) were positive only for anti-HBc.

A comparison was made of the heat resistance of Bacillus cereus spores at 95° C. Spores of serotype 1 strains were more resistant than those of the other types tested. However, there was little difference in the growth rate of the various serotypes in boiled rice at 22° C. Most samples of uncooked rice contained multiple serotypes of B. cereus.

These results indicate that the cooking procedure used for the preparation of cooked rice is likely to be selective for certain serotypes, and this is the most likely reason why type 1 is the most common serotype implicated in outbreaks of food poisoning and can be isolated from many routine samples of cooked rice.

Campylobacter jejuni was isolated from the stools of 148 patients with symptoms and 57 symptomless subjects, and from a milk sock filter, following an outbreak of enteritis associated with consumption of unpasteurized milk. The incubation period rantged from 2–11 days with a peak at 5 days. There were no secondary cases. The attack rate was around 50% Cases occured in all age groups but were maximal in the 1–10 age group. Recovery from symptoms was complete in the majority in less than 1 week. No long term excretors were indentified. There were no differences between culture positive individuals, with or without symptoms, in age or sex distribution or duration of excretion.

Laboratory feeding tests were carried out to determine the efficacy of the anticoagulant rodenticide bromadiolone against Rattus norvegicus, R. rattus and Mus musculus. Using 0·005% bromadiolone, complete kills of R. norvegicus and R. rattus not resistant to warfarin were obtained after exposure to the poison for 1 and 5 days respectively. Warfarin-resistant R. norvegicus were all killed in 4 days, and resistant M. musculus in 12 days. In general, the results resembled those obtained with difenacoum. Acceptance of bromadiolone was very good.

Seven different flotation fluids were assessed for their efficiency in recovering Toxocara canis ova from artificially seeded soil samples. Using the most efficient (a saturated solution of magnesium sulphate plus 5 % potassium iodide) 25 g amounts of 234 environmental soil samples were examined for the presence of Toxocara spp. and Toxascaris ova. Twenty-six samples (11·1 %) yielded ova of one or other species. There was no discernible pattern of distribution of positives with relation to the source of the samples. The maximum number of ova recovered in any one sample was 19. All the ova recovered from the environment were considered viable and potentially infective.

Five quarters of the udders of two lactating cows were infected by intramammary inoculation with Campylabacter coli/jejuni in doses ranging from 2·6 colony-forming units (c.f.u.) to 3·8 × 109 c.f.u. The infected quarters developed clinical mastitis and the campylobacters were reisolated in large numbers from the milk. The milk from the uninfected quarters, and blood and faeces remained free of the organisms. The campylobacters could only be isolated by incubation of culture plates in a microaerobic atmosphere. The results showed that C. coli/jejuni can cause mastitis in the cow and that the bovine udder is a potential source of C. coli/jejuni in raw milk.

Examination of the faeces of 50 babies born at home showed that bottle-fed babies carried significantly more Klebsiella, Proteus and Pseudomonas spp. and antibiotic-resistant Escherichia coli than did breast-fed babies. Bottle-fed babies born in hospital had a less mixed faecal flora than bottle-fed babies born at home. The possibility that bacterial contamination of home-prepared feeds may account for these differences requires investigation.

A study of serological, bacteriocine and phage typing of Serratia marcescens was made. Specific O-antisera of adequate titre were relatively simple to prepare but H-antisera exhibited many heterologous agglutination reactions amongst the type strains. Most of these cross-reactions were not reproduced when immobilization tests with H-sera were performed. Direct haemagglutination tests were used to establish the presence of fimbriae amongst the H-type strains and the results of agglutination tests with non-fimbriate variants of strains indicated that fimbrial antibody in high titre was present in some sera.

Replicate typing of 100 pairs of cultures by the phage-typing method indicated that small variations in pattern were common and that larger variations occurred occasionally. Therefore differences in pattern of less than two strong reactions should not be taken as evidence that strains can be distinguished.

Cultures of S. marcescens, 273 in total, from six outbreaks of infection in British and European hospitals were typed by O-serology, H agglutination and immobilization tests, phage typing and bacteriocine susceptibility by a cross-streaking method. The typability of strains by each method was high but the results suggested that no single method was sufficiently discriminating to be used alone for typing. Comparison of the H-type and typing patterns of members of the same O serogroup from incidents of infection showed that reliable results were obtained by H-typing or by phage and bacteriocine typing after the application of the appropriate ‘difference’ rule.

The greatest discrimination between strains of the same 0-group was obtained by the use of H-typing or phage typing.

This technique for the cultural examination of urine provides, within 24 hours, using a single Petri dish, the colonial appearance of any bacteria present on MacConkey agar and on blood agar, a rough colony count of the bacteria present, their sensitivity to four chemotherapeutic agents, isolated colonies from which further sensitivity tests can be done if necessary and the opportunity to scrutinize contaminating organisms that, even thought present in only small numbers, may be of help in diagnostic problems.

Four populations of small wild British rodents were studied by capture-re-capture methods over a period of three years. Samples of blood were taken from these animals and tested for antibodies to nine viruses. Animals were removed from another 11 sites around the UK, and immunosuppressed. Samples of tissue from these animals were tested for the presence of viruses by passage in laboratory mice and serum samples from some of them were tested for antibody to the nine viruses. Indications were found of the possible influence of epizootic outbreaks of certain diseases on animal populations.

Hospital food was examined for the presence of Klebsiella species. Salads and cold meat were most frequently contaminated, often containing more than 103 organisms per g. Klebsiella species were also widely distributed in the kitchen environment which was considered, at least in part, to be the source of the organisms in food.

By the use of serological and bacteriocin typing, intestinal carriage of strains ingested in food could be demonstrated.

Topical medicaments used by patients with diseases of the skin were examined for microbial contamination. Ps. aeruginosa was isolated from stock pots of a diluted emulsifying ointment used as a soap substitute in the bath. Cross-con tamination between patients and medicament was subsequently shown to have occurred.