In 1961 and 1962 a Working Party of the Public Health Laboratory Service, in which twenty-two laboratories participated, investigated the occurrence of salmonellae in abattoirs, meat factories, butchers' shops and meat products, and their association with human infections.

Thirty-two abattoirs were studied. Salmonellae were isolated from 930 (21%) of 4496 swabs of abattoir drains. There was great variation between different abattoirs, but in general salmonellae were found most frequently in those which slaughtered a high proportion of cattle and a low proportion of sheep; more sero-types were isolated from bacon factories than from abattoirs which slaughtered more than one species of animal. Of 11,347 tissue specimens collected at abattoirs, 218 (1·92%) yielded salmonellae.

Drain swabs from butchers' shops were examined and 73 (6·5%) of 1117 swabs were positive. Meat and meat products were less commonly contaminated but 0·8% of 4127 samples yielded salmonellae.

Salmonella typhimurium was the serotype isolated most frequently from all sources. It was often shown that the same serotypes or phage-types were occurring in abattoirs and in human cases in an area at the same time. In eight food-poisoning incidents, involving a total of 281 cases and excreters, there was convincing evidence that meat or a meat product was the vehicle of infection; in a further twenty-three incidents the organisms causing disease were isolated from sources which suggested that infection might have been meat-borne.

The evidence collected suggests that cattle introduce salmonellae into abattoirs more often than other species of animals. The importance of pigs as a source of human infection is confirmed. Sheep are not a source of salmonella infection in man from meat and meat products, whereas meat from pigs, cattle and calves is a source of infection and is responsible for both sporadic cases and outbreaks of disease.

We wish to thank the many medical officers of health who co-operated in this study. The public health inspectors and abattoir staffs who collected the specimens are too numerous to mention by name, but their invaluable assistance is most gratefully acknowledged. Among the medical officers who assisted us in the survey were: Dr A. Armit (Bridport M.B. and R.D.), Prof. D. B. Bradshaw (Leeds C.B.), Dr C. B. Crane (York C.B.), Dr J. Douglas (Bradford C.B.), Dr A. B. R. Finn (Guildford M.B.), Dr R. A. Good (Winchester M.B.), Dr G. B. Hopkins (Wimborne and Cranborne R.D.), Dr E. W. Kinsey (Caernarvon M.B.), Dr I. B. Lawrence (Dorchester M.B. and R.D.), Dr R. A. Leader (Ipswich C.B.), Dr Mary Lennox (Barry M.B.), Dr V. P. McDonagh (Keighley M.B.), Dr H. E. Nutten (Beccles M.B.), Dr G. O'Donnell (Worcester C.B.), Dr E. J. O'Keeffe (Wareham M.B. and Wareham and Purbeck R.D.), Dr N. F. Pearson (Sturminster Newton R.D.), Dr W. P. Phillips (Cardiff C.B.), Dr T. H. Pierce (Llandudno U.D.), Dr J. L. Rennie (Carlisle C.B.), Dr C. L. Sharp (Bedford M.B.), Dr E. F. Shennan (Evesham U.D.), Dr J. Stevenson-Logan (Southend-on-Sea C.B.), Dr D. W. Wauchob (Blackpool C.B.), Dr J. Walker (Lancashire C.C.), Dr J. V. Walker (Darlington C.B.), Dr R. B. Walker (Kingsbridge R.D.), Dr E. J. Gordon Wallace (Weymouth M.B.), Dr C. Robertson Wilson (Lancashire C.C.), Dr E. M. Wright (Salisbury M.B.), Dr Alfred Yarrow (South East Essex).

The survival and persistence of Shigella sonnei and S. flexneri in various food preparations were studied. The length of survival and the rate of decrease in surviving fractions varied considerably depending upon the menstruum and the holding temperature. This study points out the potential hazards involved in consuming food products that may be contaminated by shigellae.

1. An outbreak of food poisoning due to Salmonella typhi-murium phage-type la is described.

2. Bread and (or) bakery confectionery eaten by all but two of the victims, had originated from a particular bakery firm.

3. S. typhi-murium phage-type 1a was found in the stools of an apprentice baker, a female packer of cakes and bread, and in three female counter-hands. The apprentice baker was responsible for the preparation and decoration of the confectionery which was distributed to the branch-shops and other establishments throughout the area.

4. S. typhi-murium was not found in any of the raw materials used at the bakehouse.

5. The cases which arose at a residential school for cripples gave a ratio of six cases to eight symptomless excretors.

6. Seven weeks after the start of the outbreak the last of the infected food-handlers was considered to be free from infection and fit to return to work.

Twelve weeks later the last member of the public was declared to be negative.

Thanks are expressed to Dr Joan Taylor of the Salmonella Reference Laboratory for her advice and assistance in the preparation of this paper, and to the staffs of the Public Health Laboratory and Public Health Department, Edmonton, N. 9, for their help and co-operation during the investigation.

A rapid 18 hr. technique has been developed for detecting salmonella contaminated carcass and boneless meats. It is based on 43° C. selenite enrichment of samples, followed by immunofluorescent detection of salmonella cells in the enrichment. In tests with 286 meat samples the rapid and conventional techniques agreed in the detection of 93 positive and 149 negative samples. The two tests failed to agree for the remaining 44 samples. The rapid technique thus lacks precision, but could be used as a rapid ‘presumptive’ salmonella test, so that contaminated material could be prevented from reaching the processing lines of food factories.

We thank Dr Betty Hobbs of the Food Hygiene Laboratory for kindly sup plying the meat samples used in this investigation, Dr Patricia Bradstreet of the Standards Laboratory for Serological Reagents for the salmonella diagnostic antisera and Mr R. Kenworthy for performing the goat injections.

A survey of rinderpest-neutralizing antibody was carried out on the sera of 315 hippopotamuses which were shot in the Queen Elizabeth Park, Uganda. No serological positives were found in animals aged 11 years or less but about 4% were detected in the age class 13–25 years. In the 28–41 years age class the proportion of positives rose to about 36%. All except one of the positive sera were titrated, the figures obtained being comparable to those in other recently infected species of wild ungulates.

It was concluded that the heat-stable antibody in hippopotamuses resulted from inapparent infections with rinderpest virus during epizootics which passed through the areas of Lake George and Lake Albert in the years 1920/21, 1931/33 and 1944/45. No record was available of clinically recognizable rinderpest in the hippopotamus population but deaths due to other causes were mentioned briefly.

Comment was made on the stability of rinderpest-neutralizing antibody over periods of about 30 years.

One of us (R. M. L) is grateful to the Nuffield Foundation for financial support. Thanks are due to Drs S. S. Stone and W. P. Heuschele (Agricultural Research Service, United States Department of Agriculture) for their assistance in organizing the collection of serum samples.

This paper is published by permission of Mr H. R. Binns, C.M.G., O.B.E., Director, E.A.V.R.O.

Semliki Forest virus was passaged 10 times in series in calf kindly cells, starting with virus passaged in the mouse brain (MB virus). A variant was obtained (termed CK virus). The two viruses were antigenically indistinguishable. When grown on L cells, CK virus formed smaller plaques than MB virus. In parallel growth curve studies in calf kidney cells, a small inoculum of CK virus grew more rapidly and to a higher final titre than a comparable inoculum of MB virus, and usually stimulated production of less interferon. Pre-treatment of cells with calf interferon reduced the growth of both viruses, but especially that of MB virus. The results are considered in relation to the phenomenon of virus adaptation. It is suggested that such differences between the two variants in their relative sensitivity to and production of interferon could have played a part in the emergence of CK virus as the predominant type during serial passages in calf cells.

I wish to thank Mr H. Moores and Mr R. Sims for skilful technical assistance.

A previously unidentified type of Mycoplasma found as a contaminant in tissue cultures and in a culture of Eaton agent, is identical with a newly recognized human oral type.

I am indebted to Drs Herdersheê and Chanock for sending me their cultures and relevant information.

1. Non-specific stimulation of mice by a detergent lacking in vitro antibacterial activity, Triton WR 1339, produces a steady state in the course of experimental tuberculosis at about the same level as specific immunization, and does so independently of delayed allergy.

2. This effect is achieved in a much shorter time than is required by the normal immunological processes and the relative duration of enhanced resistance in each case is yet to be worked out.

3. Triton fails to enhance an existing, specifically acquired immunity.

4. There is no evidence so far that the mechanism involved is the same in both instances. If it were found to be the same, then the present concept of a specific cellular immunity would need to be revised.

An attempt has been made to study quantitatively the mechanisms by which infectious materials may enter the body by the upper respiratory tract and be shed during a cold.

The rapid clearance of tracers, spores of B. mycoides and bacteriophage type T3, has been measured after adding them in small drops to the nose, conjunctiva and mouth.

Tracers placed in the nose pass rapidly down the throat, but are found in only small amounts in the saliva. They are dispersed by blowing the nose and, more efficiently, by sneezing. Nearly all are shed as coarse droplets. About 0·1% are shed in droplets small enough to remain airborne and just over half of these are in the size range likely to be trapped in the upper respiratory tract. The droplets are apparently formed mainly in the nose. The larger amounts of droplets formed in the mouth carried relatively few infectious particles.

Testing by experiments in a model system it was concluded that most of the coarse droplets produced by a sneeze or by an experimental spray fall rapidly to the floor. A few of the larger droplets were trapped on a moistened microscope slide intended to mimic the possible trapping of droplets on the conjunctive. The spores in these represented only a small proportion of those found in droplets which remained airborne and were collected by an air sampler.

We wish to thank Miss P. D. Ball for technical assistance and Dr J. E. Lovelock for helpful discussion in the early stages of this work. We are also grateful to Sir Victor Negus and Dr B. Wyke for discussing the physiology of the nose with us, and to Mr K. R. May for his advice on methods of air sampling. The air samplers were loaned by the Microbiological Research Establishment, Porton, and the photographs taken by the Chemical Defence Experimental Establishment, Porton.

1. Simultaneous active and passive immunization of guinea-pigs using tetanus toxoid adsorbed on to aluminium hydroxide produced a higher antitoxin response than simultaneous immunization using plain toxoid. The response was also better than that produced by plain toxoid alone.

2. A 24 hr. interval between the injection of plain toxoid and the subsequent injection of antitoxin gave no better results than when toxoid and antitoxin were given at the same time.

3. The response to simultaneous immunization, using adsorbed toxoid, of guinea-pigs sensitized to horse serum, was superior in the first 6 weeks to that of guinea-pigs which had not been sensitized.

4. The suggestion that simultaneous active and passive immunization of man should be performed with adsorbed toxoid rather than plain toxoid is supported by these results.

1. Individually caged wild house-mice (Mus musculus L.) were fed 0·025% warfarin in a pinhead oatmeal/oil/sugar base. In all, 345 mice were tested for a fixed period ranging between 4 and 28 days.

2. There was considerable variation in the susceptibility of individual mice. The lowest effective dosage was 26·1 mg./kg. of body weight in 4 days and the highest dosage survived was 1067·2 mg./kg. eaten over 21 days.

3. The time required to obtain a 100% kill of house-mouse populations with 0·025% warfarin under field conditions is discussed.

We thank the Director of the United States Department of the Interior, Fish and Wildlife Service, for permission to quote from the Quarterly Report of that Service.

Cultures of C. albicans have been classified into two groups by means of a double diffusion precipitin test employing rabbit antisera and polysaccharide extracts. In the present series it has been found that 75% of cultures belong to group A and 25% to group B, and it is suggested that the higher incidence of group B strains occurring in the sputum of hospital in-patients with chest disease may be the result of reinfection by attenuated forms which persist in the environment.

My thanks are due to many colleagues who provided me with the strains of C. albicans, and to Prof. H. Hare for helpful criticism in the preparation of this paper.