Wild Norway rats (Rattus norvegicus) from several habitats were tested for their susceptibility and resistance to warfarin. Animals were fed 0·005% warfarin in ground oatmeal for periods varying from 1 to 12 days. Rats having no prior exposure to anticoagulants were shown to be susceptible, none having survived a 6-day feeding period. Resistant rats were found on two farms where anticoagulant materials had been used intensively for about 20 years.

Salmonella typhimurium strain 1566 administered to mice by the intraperitoneal route was considerably more lethal than the same dose administered subcutane-ously. This could be measured hi terms of mortality, infectivity and mean survival time of those mice that died.

After one passage of influenza A2/Singapore/l/57 virus in mice treated with 150 mg./kg./day of aminoadamantane, a partially drug-resistant strain of virus was detected in 1 of 12 mice. The isolation rate of aminoadamantane-resistant viruses increased to 8 after three passages in drug-treated mice. Some virus strains showed a 500-fold increase in resistance to aminoadamantane and to the structurally related compounds α-methyl-1-adamantane methylamine and 2-adamantanamine sulphate. No aminoadamantane-resistant viruses were detected after passage of influenza four times in mice treated with lower (15 or 1·5 mg./kg./day) concentrations of aminoadamantane. Aminoadamantane had no detectable effect on the development of lung lesions in mice infected with the drug-resistant influenza strain, whereas lung lesions were reduced in aminoadamantane treated mice infected with a control strain of influenza A2/Singapore virus. No differences were detected in the buoyant density in caesium chloride, morphology or serology between control and aminoadamantane-resistant strains of virus. These drug-resistant influenza viruses may be useful for detailed studies of the mode of action of aminoadamantane.

Relative rates of proportionate mortality from cancer of six sites based on total cancer deaths and the proportions expected in all towns, and from four types of cardiovascular disease based on total deaths from all causes, have been related in the 80 county boroughs of England and Wales to the sources of water supply and to the average hardness of water in. the towns. The sources of water, from upland surfaces, artesian wells and rivers, were classified in eight groups, and significant associations were found for cancers of the stomach, oesophagus, prostate, male bladder and female breast, and for hypertensive and chronic rheumatic heart disease. No associations were apparent with intestinal cancer, vascular disease of the nervous system or arteriosclerotic heart disease. Hardness or softness of the water was classified in seven groups and significant associations were found for the same diseases as for source of water, none being evident for coronary disease.

Data for mortality from cancer of the cervix in England and Wales by 5-year age groups and four quinquennia (1951–70) are analysed. The logarithms of the mortality rates are regressed on age group, epoch of death and epoch of birth. The factors obtained are considered in relation to particular features of the mortality pattern, such as the reversal of trend in certain age groups.

A total of 3217 strains of coagulase-negative staphylococci and micrococci were tested for susceptibility to a collection of phages isolated from coagulase-negative cocci; it was concluded that a useful typing scheme could be developed. Of the strains of Baird-Parker's biotype 1, 72% were lysed by one or more phages, although rather a large proportion of strains are lysed by many phages to give a complex typing pattern.

Normal persons commonly yield 10 or more distinguishable strains of coagulase-negative cocci in cultures from the nose and the skin.

The morphological, cultural, biochemical, serological and pathogenic properties of two bacterial strains of the group designated ‘Br. suis biotype 5’ were examined. Both strains were found to be atypical of the genus Brucella in many of these characteristics. No serological relationship to known brucella strains could be detected. On the basis of the evidence obtained the two strains examined were classified as Moraxella duplex and the status of ‘Br. suis biotype 5’ questioned.

In a factory population the occurrence of reactions to tetanus toxoid was recorded after 6740 injections. The incidence of general reactions was 0·3 % and of local reactions 2·6%. The local reaction rate to the first injection of the basic immunization course was 0·9%, to the second injection 2·7%, and to the third injection 7·4%. To booster injections the rate was 1·6%. The local reaction rate was appreciably higher in women than in men – 14·4 % and 5·7 % respectively in the case of the third injection – and the incidence among women increased with age.

Tetanus vaccine containing 10 Lf of toxoid caused fewer reactions than one containing 20 Lf, but a reduction in the content of aluminium adjuvant did not affect the reaction rate.

Almost all reactors were found to have a satisfactory serum antitoxin concentration at the time of the reaction or developed a satisfactory immunity within 1–6 months.

Skin tests were made in 32 hypersensitive patients. Neither the diluent, thiomersal preservative, nor the culture medium appeared to be responsible for hypersensitivity. The degree of hypersensitivity elicited by a special highly purified toxoid was only very slightly less than that elicited by the commercially pure toxoid. It is suggested that reactions are largely due to the toxoid antigen itself rather than to impurities or other components of the vaccine.

The European rabbit flea Spilopsyllus cuniculi (Dale) was first released on Macquarie Island in December 1968. The flea has survived and bred on the island and about 30% of the rabbits sampled from the original release area in January 1972 were flea-infested.

The nature of the antibody response of cattle to the antigen of Yersinia enterocolitica IX cross-reacting with Brucella spp. was examined. Density-gradient ultracentrifugation, ion-exchange chromatography, antibody adsorption and elution and disulphide bond reduction tests showed that both 19 S IgM and 7 S IgG1 and IgG2 antibodies were produced in response to the cross-reacting antigen. The highest titres of cross-reacting antibodies were detected by the agglutination and Coombs antiglobulin tests. Production of complement-fixing and precipitating antibodies cross-reacting with Br. abortus was transient and high titres were not attained.

In contrast, although infection with Br. abortus also evoked cross-reacting antibodies of the IgM and IgG classes, much higher titres were produced in the complement fixation and precipitation tests and these persisted for long periods. At all stages of the serological response to both organisms, the two infections could be differentiated by the quantitative Rose Bengal plate test.

Newcastle disease virus has been shown to survive when airborne in small particles, both in the laboratory and in the open air. Field outbreaks have been studied and viable virus has been recovered from the open air short distances downwind of infected premises. Vaccination of birds leads to a great reduction in the amount of virus liberated into the air.

A survey of the staphylococcal infections occurring in a general hospital over a period of four and a half years showed that multiple-resistant strains of phage type 77 were endemic in the medical and surgical wards. Strains of this phage type were uncommon among patients attending the casualty department, and those found were usually either fully sensitive to antibiotics or resistant to benzyl-penicillin only. Regular monitoring of patients admitted to the intensive-care unit showed that 58 % of staphylococcal infections in such patients were present at the time of admission to the unit. Although the wards thus constituted a significant reservoir of infection for the intensive-care unit, there was no evidence to suggest that the return of patients from the unit to the wards was responsible for the transfer of infection in the opposite direction. The possibility of reducing the numbers of multiple-resistant staphylococci in the general wards, by the screening of all new admissions for the presence of tetracycline-resistant strains, appears to be impracticable in this area.

Strontium selenite A broth incubated at 37° C., and strontium chloride B broth incubated at 43° C., have been found an effective combination for the isolation of Salmonella, Arizona and Edwardsiella from human faeces.

Direct plating on deoxycholate citrate agar was superior to enrichment methods for the isolation of Shigella species.

Strontium selenite A broth was suitable for the isolation of Salmonella and Arizona bacteria at both 37° and 43° C.

Strontium chloride B broth incubated at 43° C. was best for the isolation of Salmonella and Edwardsiella.

Modified bismuth sulphite agar, although superior to D.c. agar for the growth of Salmonella and Arizona bacteria, was unsuitable for Edwardsiella and Shigella species.

A considerable difference was observed in the distribution of Salmonella, Arizona and Edwardsiella serotypes isolated from humans in remote areas, when compared with isolations from more densely populated urban and agricultural centres.

Epidemiological and zoogeographical aspects of host–parasite associations between humans, animals and pathogenic Enterobacteriaceae in Western Australia are discussed.

A survey was conducted in 1971 in healthy reptiles supplied to the Central Animal Laboratory of Nijmegen for experimental animal research. In order to determine which salmonella serotypes occur, and whether there are several serotypes per animal, several strains of each positive sample were typed.

It was found that 160 of 169 samples contained salmonellas or lactose-negative Arizonas or both, and 95 different serotypes were isolated.

Of 127 animals examined individually, 67 were carriers of more than one sero-type, 42 animals having two types, 21 three types and 4 animals four types.

Three enrichment methods were compared. These were tetrathionate broth incubated at 37° C. (T37) and at 43° C. (T43), and selenite broth incubated at 37° C. (SB). All were incubated for 48 hr. before subculture on brilliant-green agar plates. The enrichment methods T37, T43 and SB produced 99, 125 and 123 positive samples respectively, when taken separately. The combinations of T 37 and T43, T37 and SB, and T43 and SB produced 145, 142 and 150 positive samples respectively.

The yield of serotypes in comparable samples showed no difference between the three enrichment methods. With the use of two methods the yield increased by about 38 % compared with one method, and the combination of three methods showed an increase in serotype yield of about 64 % compared with one method. A distinct preference by serotypes for definite enrichment methods was not proved.

During a laboratory study of diarrhoea in a large urban area during the years 1953–68, 5319 Sonne dysentery infections in 2620 households and six cases of Flexner dysentery in five households were confirmed. The annual incidence per 10,000 population fluctuated between 2 and 31 with an average of 12.

Shigella sonnei was found in 10% of new cases of diarrhoea investigated. Plural infections were found in 58% of the households studied and 30% of all contacts examined were shown to be infected. Among these contacts the infection rate was higher for children (42%) than adults (20%), and higher for adult females (24%) than males (16%). The duration of infection was under 2 weeks in nearly half the index cases followed up and longer than 2 months in only 3%, Intermittent excretion was observed in 15%. Repeated Sonne dysentery infection and illness was observed after intervals as short as 5 months. Antibiotic sensitivity was recorded after 1955 and colicine typing after 1960. Changes in antibiotic sensitivity were noted. Children of primary-school age were most susceptible to Sonne dysentery, but symptoms in ill cases were as severe in adults as in children. During years of high incidence cases were concentrated within a small number of primary schools.

Sh. sonnei infections were compared with salmonella infections studied concurrently. Sonne dysentery was a winter disease and most cases were under 11 years old, and case-to-case infection was the usual means of spread. Salmonellosis was prevalent in summer and affected nearly as many adults as children, often persons sharing an article of food. It was more prolonged and severe than Sonne dysentery, but less infectious. In all these respects S. typhimurium occupied an intermediate place between Sonne dysentery and ‘other salmonellas’.

Sera from 218 of 1574 (14%) small mammals collected in the Yukon Territory between 14 May and 13 August 1972 neutralized a Yukon strain of California encephalitis virus (snowshoe-hare subtype). These included 133 of 319 (42%) snowshoe hares (Lepus americanus), 84 of 1243 (7%) ground squirrels (Citellus undulatus) and 1 of 12 (8%) tree squirrels (Tamiasciurus hudsonicus). California encephalitis virus (snow-shoe hare subtype) was isolated from four pools of unengorged Aedes communis mosquitoes collected near Whitehorse (61° N., 135° W.) and on one occasion each from pools of the same species collected at Hunker Creek (64° N., 138° W.) and at mile 125, Dempster Highway (66° N., 138° W.) during July 1972. Replication of a Yukon strain of California encephalitis virus was observed in wild-caught Culiseta inornata and Aedes canadensis mosquitoes after intrathoracic injection and holding at temperatures of 80°, 50° and 40° F.

Two hundred and sixty strains of Pseudomonas aeruginosa were isolated from patients of the Asaf Harofe Government Hospital. The strains were typed by phage technique and 64 of them were also typed according to pyocine sensitivity. The two methods proved complementary, and reduced the number of untypable strains. Phage typing was performed with both routine test dilution (RTD) and more concentrated phage suspensions. The most reliable results were obtained at 100 RTD.

Cultures of Staphylococcus aureus showing unstable resistance to kanamycin, streptomycin, lincomycin and penicillin have been preserved by drying. Particular attention has been paid to organisms showing linked resistance to pairs of these antibiotics. Recoveries of viable cells from the desiccates was high and the proportion of resistant and sensitive cells was maintained both during storage and during heating. The preservation of the organisms on ceramic beads stored in air over silica gel promises to be an effective and convenient method for maintaining staphylococcal desiccates during studies of unstable antibiotic resistance.

A significant proportion of a consignment of branded Parma Ham was found to have ‘blown’ tins; the associated bacterial flora was therefore investigated. No Salmonella or Shigella were found. Clostridium welchii type A and Clostridium bifermentans were isolated in moderate numbers only from enrichment cultures of the ham. Staphylococcus spp. and coryneform bacteria were obtained from all tins and Group D streptococci were present in a few. No food-poisoning cases were associated with this ham.