Two isolations of Arizona from humans were made in Sheffield in 1966. The first was from a 3-year-old girl with a history of gastro-enteritis; the second was from her 5-year-old brother who was a symptomless excretor. Infection was traced to pet terrapins recently purchased from a local pet shop. The relative epidemiological significance of Arizona infection and the potential hazard of pet terrapins has been reviewed.

We wish to thank Dr V. G. S. Damms for his help and co-operation and for allowing us to publish details of his patients, Dr J. G. Wallace for his work on the preliminary identification of the organism, and Dr Joan Taylor and Dr E. H. Gillespie for their helpful advice and criticism.

Two strains of enzootic pneumonia, which are regularly free from mycoplasmas other than Mycoplasma suipneumoniae, were transmitted experimentally to a total of 22 pigs. M. suipneumoniae was recovered in liquid medium from the lung lesions in 20 of these animals (91%).

Twelve field outbreaks of enzootic pneumonia were likewise examined for M. suipneumoniae: from each outbreak, cases were selected where many mycoplasmas with the morphology of M. suipneumoniae were seen in touch preparations made from the lung lesions. M. suipneumoniae was recovered from only two of these outbreaks, but M. hyorhinis was obtained from nine of them.

To establish whether the outbreaks yielding only M. hyorhinis were indeed enzootic pneumonia, material from five of them was used in disease-transmission experiments: enzootic pneumonia was induced in every instance, and M. suipneumoniae was recovered from three of the five transmitted strains.

It is concluded that M. hyorhinis is commonly present in the lung lesions of enzootic pneumonia and that this mycoplasma may often prevent the isolation of M. suipneumoniae. The problem of recovering M. suipneumoniae in this situation is made more difficult by the fact that in no instance where M. suipneumoniae was isolated directly in liquid medium was it cultured in parallel on solid medium.

The results of a combined clinical and laboratory study of respiratory infections among members of an Australian Antarctic expedition are presented. Virus isolation and serological methods were employed, but the aetiological agent or agents responsible for respiratory infections in this group were not revealed.

The clinical findings were correlated with published and unpublished studies on comparable communities, and the following broad pattern of the epidemiology of respiratory tract infections in such groups has emerged. The assembly on board ship of a party from widely separated areas often leads to infections after embarkation. On long voyages these infections may burn out, but frequently new cases are still appearing when the party arrives in Antarctica. Symptoms in sufferers at this time become more severe, suggesting that the sudden environmental change from the warmth of an air-conditioned ship to the harsher Antarctic conditions may influence the course of the respiratory infections. With isolation established in Antarctica, further cases rarely appear. On exposure to the relief party, however, infections can be expected, and it is noted that morbidity is usually low and symptoms are mild, indicating an apparent heightened resistance to infection in the acclimatized party while still on the ice.

This study has further shown that most of these men, on returning to urban societies, contracted moderately severe upper respiratory tract infections in contrast to their apparent resistance when under Antarctic conditions.

The suitability of these groups for experimental study, including the inoculation of volunteers, was discussed and suggestions were made for future work.

Trimethoprim, a 2,4-diaminopyrimidine derivative which inhibits the growth of some bacteria by interfering with folic acid synthesis, inhibited the growth of several strains of the trachoma agent. Inhibition was most clearly demonstrated by measuring prolongation of mean death time of groups of chick embryos inoculated with a single lethal dose of agent. Over a certain range, prolongation was proportional to the logarithm of concentration of inhibitor; higher concentrations were toxic for the embryo. On a weight basis, trimethoprim was not as active as sulphafurazole. Inoculation in conjunction with sulphafurazole resulted in slight potentiation of activity. A related pyrimidine derivative, the antimalarial drug pyrimethamine, also significantly inhibited the growth of one strain of trachoma.

In cell culture, trimethoprim decreased the number of inclusions formed by a suspension of the trachoma agent and induced morphological changes in the inclusions similar to those caused by sulphafurazole.

Inhibition of the growth of the trachoma agent in the chick embryo was reversed by leucovorin calcium. It is concluded that, as with bacteria, the drug acts by blocking the folio acid cycle and that the trachoma agent most probably contains a dihydrofolate reductase.

The possibility of developing a living oral cholera vaccine with naturally avirulent El Tor cultures isolated in a Middle East country or from water sources in Calcutta in the absence of cholera El Tor in these areas has been further studied.

In an extended series of experiments the markedly low pathogenicity of the proposed vaccine strains in laboratory animals has been confirmed. The vaccine strains have been shown to get established and multiply regularly in the ligated intestinal loops of adult rabbits and in the intestine of infant rabbits without producing pathogenic reactions.

The apathogenic character of the vaccine strains has been found to be stable. When propagated serially in these two laboratory models of experimental cholera the vaccine strains show no enhancement of pathogenicity.

Intra-intestinal administration of the live vaccine has been shown to protect adult rabbits fully in the intestinal loop test. Immunized animals were also protected against challenge with V. cholerae strains, though to a somewhat lesser extent. Protective immunity could not, however, be demonstrated in infant rabbits probably because of the immunity-forming mechanism being still rudimentary.

Immunization with live vaccine was found to inhibit the growth of homologous strains in the ligated intestinal loop of the adult rabbit. The growth rate of pathogenic V. eltor and V. cholerae strains was also seen to be markedly reduced throughout the 24 hr. period of observation, but more markedly during the first 4–8 hr. However, the total count of pathogenic V. eltor and V. cholerae strains at 24 hr. after inoculation in ligated ileal loops of immunized rabbits reached levels that invariably caused inflammation and accumulation of fluid in normal rabbits' loops. The absence of gut-inflammatory reaction in immunized rabbits under these conditions has been discussed in relation to the nature of the immunity produced by administration of live vaccine.

Pigs were infected by the intranasal instillation of a large dose (ca. 107·0 ID 50) of a highly virulent strain of African swine fever virus (ASFV) and the progress of the infection was studied by the ‘routine titration approach’ (Mims, 1964) using pig bone marrow cultures.

Virus growth was established within 16–24 hr. in the retropharyngeal but not in the alimentary or nasal mucosae or the tonsils. By 24–40 hr. the virus was consistently present in the retropharyngeal lymph nodes, almost invariably the medials; titres in these nodes exceeded those in the associated mucosa by 48–72 hr. Generalization, presumed to have occurred via the tracheal lymph ducts and the blood stream, was generally demonstrable after 72 hr., i.e. by the time of the onset of pyrexia or 24 hr. prior to this.

On average 11% of the total infectivity in the blood was present in the plasma, with the rest assumed to be cell-associated. A mean of about 45% of the total infectivity was recovered in erythrocyte fractions in which the concentration of leucocytes had been materially reduced; fractions with increased leucocyte counts contained relatively little virus and it was concluded that the great majority of circulating virus was closely associated with the erythrocytes. Adsorption of ASFV to normal pig erythrocytes was demonstrated in vitro.

The greatest concentrations of virus were recorded in the lymph nodes, especially those of the cephalic region, and in the spleen, where titres commonly attained 108·0 to 109·0 HAD 50/g. and exceeded those in the blood. They were, therefore, thought to be the source of much circulating virus, although there was some evidence that the liver, lungs and bone marrow may also have contributed, at least in some animals. There was no evidence that the mucosae of the alimentary and respiratory tracts or the kidney, myocardium and brain were a source of significant amounts of virus. The virus demonstrable in Peyer's patches did not exceed that in the intervening ileal mucosa.

Although contact transmission of ASF does not normally occur during the first 12–24 hr. of fever, considerable amounts of virus were usually present in the nasal and intestinal mucosae at 72 hr. It was probable that this infectivity was due to the blood content and that excretion did not occur until the epithelium was breached.

Three pigs, all of which had lesions of a portal cirrhosis, showed a delayed or restricted generalization of virus, in comparison with the other twenty-eight animals which behaved according to a regular pattern.

We are grateful to Mrs M. O'Sullivan and Mrs E. Douglas for painstaking technical assistance and to Mr C. S. Rampton, A.I.M.L.T., for the preparation of the figures.

Experiments have been made in several supermarkets, shops and cafés to determine the bacterial counts on slicing machines, carving knives and can-openers after contact with various cooked and canned meats, and to find a simple, quick and effective cleaning method for such articles of equipment. The importance of personal effort in cleaning rather than a reliance on the known attributes of detergent/disinfectants is stressed. The methods available for testing the efficiency of cleaning procedures are outlined.

In vitro tests have shown that the detergent/disinfectant used in the present study at a concentration of 0·75 % (w/v) was satisfactory. This concentration was the minimum inhibitory concentration for Salmonella paratyphi B, which was the most resistant of fifteen strains of bacteria studied.

The design of slicing machines and can-openers is discussed in relation to safety in use and ease of cleaning. Recommendations concerning the necessity of regular and effective cleaning of food-handling equipment and storage of cooked and canned meats before and after slicing are given.

As many cultures of Staph. aureus untypable by the international basic-set phages at RTD were typed by a block of 20 extra phages at RTD as by the basic set at RTD × 1000. Reproducibility of the lytic patterns was as good with the extra phages at RTD as with the basic-set phages at RTD, and better than with the basic-set phages at RTD × 1000.

A method of assessing redundancy in any set of phages is presented, and a ‘3-strong differences’ rule is suggested for discriminating between cultures of staphylococci from patterns of phage lysis by the combined set of phages at RTD.

Experience with the combined set of phages suggests that it may be possible to improve the phage-typing of staphylococci by substituting a larger series of phages used only at RTD, for the present set of 22 phages used at RTD and RTD × 1000.

A cylinder filled with medium is described, with which prints are made of floors or other surfaces. After a print has been made a slice is cut off the medium, put in a Petri dish and incubated. With one filled cylinder about twenty prints can be made. The method can be used for quantitative bacteriological testing of floors, and the effect of treatment with disinfectants can also be checked in a simple way. Preference was given to disinfection with Halamid.

Details of confirmed outbreaks of food poisoning due to heat-sensitive Cl. welckii are given. In 4/5 incidents heat-sensitive Cl. welckii were isolated in large numbers from the majority of the faeces. In the remaining outbreak the faecal samples were not collected until 7–9 days after the illness. The causative organism was isolated from the food in 3/5 instances.

In addition four outbreaks of food poisoning in which both heat-sensitive and heat-resistant Cl. welckii were isolated are described.

The role of heat-sensitive Cl. welckii in food poisoning outbreaks is discussed and a suggested method of examining faeces for Cl. welchii is given.

We are indeed grateful for the assistance given in collecting faecal specimens and obtaining detailed information on the food preparation, etc., by Drs G. C. Turner, J. Epsom, J. G. Wallace, P. J. Wormald, H. D. Holt, D. G. Fleck, J. M. Graham, E. Tanner and J. D. Abbott. We would also like to thank Mrs I. Batty of the Wellcome Research Laboratory for carrying out toxicological examinations for us.

One of us (R.G.A.S.) is attached to the Commonwealth Department of Health, Australia, and is at present the holder of a Public Service Board Postgraduate scholarship.

Following inoculation of Murray Valley encephalitis virus into calves there was an early transient IgM response. The appearance of IgG was only slightly later than the first appearance of IgM in three calves, and in one calf IgG was detected before IgM. The secondary response was characterized by the more rapid appearance of IgG and the virtual absence of IgM. The IgG was of the electrophoretically fast type; there was an almost insignificant amount of antibody activity in electrophoretically slow fractions. IgM and slow IgG had no complement-fixing activity. IgM and IgG showed different cross-reactions to other group B arboviruses. The different cross-reactions, and the appearance of IgG before IgM in one animal suggests that the switch-over from IgM to IgG synthesis in the response is not the result of either a total or a random proportion of cells producing IgM, changing to IgG production. The fact that the IgG was almost exclusively of fast electrophoretic mobility suggested that the virus antigenic components were strongly basic, and as this is contrary to the chromatographic properties of arboviruses, it is suggested that the virus particles must be broken down before making contact with the factors determining the type of immunoglobulin formed.

Norbormide at 1·0 and 0·5% and zinc phosphide at 5·0 and 2·5% were each tested in four types of cereal bait, after prebaiting and as direct poisons, against infestations of R. norvegicus on forty-eight farms in Montgomeryshire.

The relative success of treatments was measured by the reduction in the number of takes from wheat baits put down for 2 days, 13 or 16 days before, and 5 days after, poisoning.

Treatments with zinc phosphide were significantly more successful than those with norbormide, irrespective of the cereal bait, concentration of poison or method of treatment used, and in spite of conditions on many farms that partially restricted the distribution of the baits containing zinc phosphide.

Differences between these results and results of laboratory tests with the same rodenticides are discussed.

Norbormide is recommended for use in situations where zinc phosphide cannot be used efficiently without risk to livestock.

We are indebted to Messrs Tavolek Laboratories Limited, Slough, for the free supply of norbormide made available early in the trial; also to Messrs. Lloyd and Pritchard, who were responsible for all the treatments; to Miss E. J. Taylor and Miss P. Cullen for assistance with some of the census baiting, and to J. H. Greaves for permission to examine original data and present them in Table 3.

Sheep infected with FMDV strains of different epizootiological origin developed a carrier state which persisted in the majority of animals for 1–5 months.

The sites of virus persistence and multiplication in the convalescent animal were identified by titration of suspensions of mucosae and epithelia taken post mortem. Virus was recovered most frequently and in highest titre from the tonsillar area and less frequently from the pharynx and dorsal surface of the soft palate. No virus was found in samples taken from the nasal passages, the trachea or the rumen.

Injections of virus in calves up to about 5 weeks of age caused either the production of both IgM and IgG, or the production of only IgG, or no detectable antibody. In all but one case priming for a secondary response occurred even in the absence of a detectable primary response. These results suggest that in the young calf immunological memory is more readily induced than IgG synthesis. IgM appeared by the 7th or 10th day, which was similar to the response in older calves. IgG was more variable in its appearances but was usually considerably delayed relative to the response in older calves. In general only low levels of IgM were formed in the primary response and it was virtually absent from the secondary responses. Higher levels of IgM were formed after reovirus inoculation than after Murray Valley encephalitis virus or Getah viruses. The delay in appearance of IgG was more pronounced in response to Getah than to reovirus or Murray Valley encephalitis virus. High levels of maternally derived passive antibody inhibited the development of an active response, although in one animal a response occurred in the presence of low levels of passive antibody.

The coagulability of the plasma of blood taken from the retro-orbital sinus of untreated and warfarin-treated wild house mice (Mus musculus L.) was determined. Individual differences were observed in the resting clotting times of animals drawn from three different sources, so-called ‘normal’ (N) mice, home-bred warfarin resistant (HBR) mice and field-caught suspected warfarin resistant (FR) mice. Mice from the three sources also showed wide individual variation in response to injected doses of 1, 5 and 50 mg. of warfarin/kg, body weight. The overall response shown by HBR and FR mice, particularly females, was less than that shown by N animals. Some FR females failed to respond to a dose of 100 mg. of warfarin/kg, body weight.

Normal mice showed a similar response to two identical doses of warfarin (1, 5 or 50 mg./kg. body weight) given at an interval of 3 weeks. They developed a tolerance to repeated daily injected doses of 1 mg. of warfarin/kg, body weight but not to the higher doses (5 and 50 mg./kg.) to which some HBR animals became tolerant.

In comparative 21-day feeding tests with 0·025% warfarin in medium oatmeal, the mortality in N, HBR and FR mice was 100% (27), 64·5% (40/62) and 22·7% (10/44) respectively. Whereas the plasma of all N mice was rendered uncoagulable after 3 days and the animals died within 12 days, the clotting times of the surviving HBR and FR mice (24/59 males and 32/47 females) either were not at any stage appreciably increased or had declined to near normal values by the end of the test period.

In similar tests with 0·025% warfarin in oatmeal bait containing 5% mineral oil, it was found that the clotting ability of the plasma of N, HBR and FR mice was impaired earlier and that mortality in HBR and FR animals was significantly higher (62/67, 92·5% and 7/8, 87·5% respectively).

Three of seven HBR mice died after prolonged feeding on various warfarin baits but only after 186, 197 and 209 days respectively. The inclusion of mineral oil in bait containing 0-0·25% warfarin was more effective in decreasing the coagulability of the blood of these mice than either increasing the concentration of warfarin (to 0·1 and 0·2%) or including sulphaquinoxaline or corn oil.

Studies on mice given warfarin by injection and in feed indicated that in females the level of resistance to warfarin may be assessed on the basis of their response to a single injected dose of warfarin.

In nine laboratories 1% lactose ricinoleate broth has been investigated as a possible alternative to brilliant green bile broth as a confirmatory medium for coliform organisms and Escherichia coli.

Although the results varied considerably from one laboratory to another, in the sum of the results and in the majority of the participating laboratories 1% lactose ricinoleate produced fewer false negative reactions than brilliant green bile broth as a confirmatory medium at both 37 and 44° C.

Although both media are satisfactory, 1% lactose ricinoleate broth can be recommended as an alternative to brilliant green bile broth for the confirmation of coliform organisms and Esch. coli from presumptive positive tubes in the examination of water samples, as it is not subject to the known variability of brilliant green and ox-bile.

The incidence of antibiotic resistant strains of Sh. sonnei isolated in the London area is described. Strains were tested for their ability to transfer resistance to Most strains were resistant to sulphonamide and this resistance was transferable.

An increasing proportion of strains was resistant to 800 µg./ml. of streptomycin, but transferable streptomycin resistance was less common and often associated with tetracycline resistance.

The proportion of strains resistant to tetracycline fluctuated but this resistance was always transferred.

Ampicillin resistance was common; only those strains resistant to 500µg./ml. transferred this resistance.

Resistance to other antibiotics was very rare.