Mice killed shortly after receiving 1300–3000 spores of Clostridium botulinum type C per os were incubated at one of four chosen temperatures together with bottles of cooked meat medium seeded with a similar inoculum. After incubation the rotting carcasses were homogenized. Sterile membrane filtrates of the homogenates (10–20.8%, w/v) and pure cultures were then titrated for toxicity. A temperature of 37 °C produced less toxicity in most carcasses than in cultures. At 30 °C, however, toxicity (often 2× 105 to 2× 106 mouse intraperitoneal LD/g or ml) was roughly similar in both systems, and some carcasses and cultures were still toxic (2× 104 to 2× 105 LD/g or ml) after 349 days. Surprisingly, at 23 °C, though greatly reduced in the cultures, toxicity was high in many carcasses for at least 28 days. Little or no toxin was produced in either system at 16 °C. Unfiltered homogenates (17·8–22·5%, w/v; dose 0·25 ml per os) of toxic carcasses incubated at 30 °C for 7 days invariably produced death from botulism, often within as little as 4 h, but a 1 in 10 dilution produced less than 100% mortality.

Ureaplasma urealyticum organisms (ureaplasmas) and Mycoplasma hominis organisms (mycoplasmas) were sought in mid-stream urines collected from 200 men and 200 women attending hospital with conditions of a non-venereal nature. In addition, the urines from 100 male and 100 female healthy volunteers were examined. Overall, ureaplasmas were isolated four times more often than mycoplasmas. In individuals less than 50 years of age, the organisms were found in about 20 % of men and about 40 % of women. In individuals 50 years or older, they were found about one-third to one-half as frequently. Centrifugation of urine and examination of the resuspended deposit did not increase the isolation rates. In men, the numbers of organisms in the urine were usually small (< 103 c.c.u./ml) with less than tenfold more in the urine of women. The occurrence of 51– > 1000 leucocytes per mm3 in some of the urines was not associated with either the presence or an increased number of ureaplasmas/mycoplasmas, whereas they were associated with the presence of 105 or more bacteria/ml. The significance of these findings in the context of defining the role of ureaplasmas/mycoplasmas in genital-tract disease is discussed.

An analysis of the meteorological conditions showed that the first outbreaks of myxomatosis in S.E.England in 1953 could have resulted from wind carriage of insects infected with myxoma virus from northern France. South-easterly winds on the night 11–12 August would have carried the insects 120–160 km from the Départements of Nord, Pas de Calais and Somme across the English Channel to near Edenbridge, Kent. The flight would have taken 6·5–8·5 h at wind speeds of 15–22 km h−1. On the night 11–12 August, temperatures increased with height (inversion) up to 500 m; at ground level temperature was around 19 °C and at 500 m was 25 °C. Insects would have travelled up to the top of the inversion arriving on 12 August as the inversion declined. Two or possibly three generations of infection would have taken place before the disease was seen around the middle of September 1953. The most likely insect was the mosquito Anopheles atroparvus which breeds along the coastal marshes of England and northern France and which has been shown experimentally and in the field to transmit myxoma virus mechanically.

The antibiotic resistance of Mycoplasma mycoides ssp. mycoides strain T1 was investigated. This strain was resistant to high levels ( > 100 μg ml−1) of rifampicin and nalidixic acid. It was sensitive to streptomycin, spectinomycin and novobiocin; however, single step mutants with high levels of resistance ( > 100 μg ml−1) were readily isolated. With erythromycin and tylosin for which the minimum inhibitory concentration (MIC) for the parent strain was < 0·1 μg ml−1, mutants resistant to > 100 μg ml−1 were obtained in two and three steps respectively. The MIC of tetracycline in single step resistant mutants (0·6 μg ml−1) was tenfold higher than the parent strain, but could not be increased further. There was only a twofold increase in resistance to chloramphenicol in single step mutants. The frequency of resistant mutants varied with the antibiotic and was between 4× 10minuss;6 and 2× 10−8. The mutation rate to antibiotic resistance to streptomycin, spectinomycin, novobiocin, erythromycin and tylosin was between 3× 10−8 and 5× 10−9 per cell per generation. There was a fivefold decrease in mutation rate to resistance to 60 μg ml−1 streptomycin compared to that to 20 μg ml−1.

The mite fauna of dust from cloth-covered seats of four passenger trains and bedding from a British Rail linen store in Glasgow was investigated; 22 samples containing 4488 mg of dust from a total surface area of 5·5 m2 were taken. Sixteen samples were positive for mites and 33 specimens belonging to 10 species were found. The most common species were Dermatophagoides pteronyssinus (Trouessart), Glycyphagus domesticus (De Geer), G. destructor (Schrank) and Euroglyphus maynei (Cooreman). The species composition bore considerable resemblance to that of house dust (although the density of mites was far lower) and the mites have probably been transported from homes via clothing and pets. Only five intact specimens, which may have been alive at the time of sampling, were found. The dust from trains consisted mostly of particles of soot. Very few skin scales, the food source of house dust mites, were detected. The small numbers of intact mites found and the absence of an identifiable food source make it unlikely that permanent populations of mites survive in upholstered seats on trains.

A strain of Mycoplasma californicum successfully infected an experimentally inoculated ovine mammary gland causing a severe mastitis. The condition lasted for about 25 days, and resulted in atrophy and loss of milk production in the gland. Four experimentally infected ewes, treated over a 3-day period with various regimes of the antibiotics oxytetracycline or tylosin during the acute stage of infection, successfully eliminated the infection. Two others similarly treated with combined intramammary and intramuscular tiamulin or with intramammary Bay Vp2674, did not eliminate the infection; but another ewe treated with intramuscular as well as intramammary Bay Vp2674, did resolve the infection. The two ewes that were unsuccessfully treated with antibiotics at the acute stage did respond to tylosin or oxytetracycline at a later stage of infection. Measurement of antibiotic concentrations demonstrated that the persistence of inhibitory levels in the milk varied between the antibiotics and were influenced by the extent of parenteral treatment.

Of 2356 strains of Salmonella typhi isolated in Britain in the 8-year period 1978–85, 2345 (99·53%) were sensitive to all antibiotics tested and 11 (0·47%) were chloramphenicol-resistant; chloramphenicol resistance was plasmid-mediated in 6 strains. It is concluded that chloramphenicol remains a satisfactory first-line choice of drug for tyrphoid fever in Britain.

The administration per-orally to mice of the non-absorbable antibiotics polymyxin E, tobramycin and amphotericin B resulted in the elimination of detectable aerobic gram-negative rods from the faecal flora without affecting the total viable aerobic count. The addition of parental cefotaxime to the regime caused a fall in the number of aerobic lactobacilli and an increase in the number of enterococci. The rise was associated with the translocation of viable enterococci to the mesenteric lymph nodes and the spleen. The changes induced by cefotaxime were reversed when the antibiotic was withdrawn. Following withdrawal of all antibiotics the total aerobic faecal flora increased to above normal levels, but there was no associated diarrhoea. Attempts to implant exogenous enterobacteria into the digestive tract resulted in only low level colonization both in treated mice and in control mice. These results may have implications for the use of this antibiotic regime for selective decontamination of the digestive tract in humans, particularly those who are immunocompromised.

The consumption of bi-valve mollusean shellfish has been associated with outbreaks of viral gastroenteritis and hepatitis A. Investigations were undertaken to determine the heat inactivation conditions necessary to render shellfish such as cockles safe for the consumer. Conditions for the laboratory maintenance of live cockles are described. In preliminary experiments either poliovirus (106 TCID50/ml seawater) or hepatitis A virus (HAV) (approx. 104 RFU/ml seawater) was introduced into the shellfish tank. Following 48 h filter feeding, virus was recovered from cockles using an adsorption-elution extraction procedure. Titres of virus recovered ranged from 104 to 105 TCID50/ml of shellfish extract for poliovirus and from 103 to 105 RFU/ml of shellfish extract for HAV. Active ingestion of the virus from the seawater was demonstrated by recovering virus from within cockle guts. To quantify recovered HAV, end-point dilutions and an adaptation of a radioimmunofocus assay (RIFA) were compared. The tests were of similar sensitivity but the RIFA has the advantage of being relatively rapid, shortening the time taken to complete an experiment by as much as 4 weeks.