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Summary The incidence of gastroenteritis on a passenger ship is reviewed and discussed in relation to the agents of infection from stool specimens, the bacteriological condition of food samples, and the practice of galley hygiene.

Summary Clostridium welchii type A is a common agent of food poisoning when allowed to proliferate to large numbers in cooked foods, usually meat and poultry. The main factors of importance are survival of the spores, frequently found on raw products, through the cooking process, and possible contamination of cooked meats transferred to unclean containers; subsequent germination of spores and rapid multiplication of the vegetative cells during long slow cooling and non-refrigerated storage lead to heavy contamination. The toxin responsible is different from the soluble antigens, and its formation in the intestine is associated with sporulation. Large numbers of Cl. welchii of the same serological types in food and faeces is the main diagnostic factor. Important preventive measures are rapid cooling and cold storage to prevent growth. Bacillus cereus is an aerobic sporulating organism commonly found in cereals. Outbreaks described from Europe have a different aetiology with regard to food vehicles, incubation period and symptoms from those that have been reported recently in the U.K. from fried and boiled rice. The spores survive through cooking procedures and grow out to cells which sporulate readily in the cooked food and which are assumed to produce toxin in the food. Large numbers of B. cereus are found in foods causing illness and, as with Cl. welchii, the main preventive measure is inhibition of growth by quick cooling and cold storage of foods cooked ahead of requirements. A comparative table of the characteristics and clinical symptoms of Cl. welchii and B. cereus is given.

1. By means of phage typing of Bact. typhosum, the source of infection in a boy who drank water from a polluted stream was traced backwards via water, sewage effluent, crude sewage and faecal specimens to unsuspected typhoid carriers in a large institution.2. A nurse in the institution contracted typhoid fever, caused by the same phage type (C) of Bact. typhosum as was found (a) in the stools of typhoid carriers in the wards in which she was on duty, (b) in the crude sewage and sewage effluent from the institution, (c) in the stream into which the sewage effluent discharged, and (d) in the stools of the boy who drank the stream water. The nurse's sister, who had had an attack of typhoid fever a few months earlier, was infected with a different type (E 1) of Bact. typhosum and was therefore not the source of her sister's infection.3.The laboratory technique is described for the examination of (a) samples of water, sewage effluent and crude sewage, using different selective and enrichment media, (b) large numbers of faecal specimens for enteric organisms by a preliminary pooling of specimens in batches of six or seven, and further examination of the individual specimens comprising a positive batch, thus effecting a saving of time and economy of media.We wish to thank the Medical Officers of Health, sanitary inspector and the medical and nursing staff of the institution for their enthusiastic co-operation in the investigation.

1. Outbreaks of mild food poisoning have been investigated in which heat-resistantCl. welchiiappeared to be the causative organism. The outbreaks were characterized by colic and diarrhoea without vomiting, commencing 8–20 hr. after ingestion of the contaminated food.2. The strains ofCl. welchiiconcerned are only feebly toxigenic, and apart from the heat-resistance of their spores, and some colonial characters, fit well intoCl. welchiiType A. The toxin production and the serology of the strains is uniform within an outbreak.3. Mild food poisoning similar to that seen in natural epidemics has been produced in volunteers by ingestion of cultures of heat-resistantCl. welchiiisolated from contaminated meat.4. Infection is almost invariably due to meat which has been boiled, steamed, braised, stewed or insufficiently roasted, allowed to cool slowly, and eaten the next day, either cold or reheated.5. Outbreaks of this kind should be prevented by cooking meat immediately before consumption; or, if this is impossible, by cooling the cooked meat rapidly and keeping it refrigerated until it is required for use.

1. When toxic filtrates derived from coagulase-positive staphylococci including twelve food-poisoning strains, thirty pyogenic strains of human and twelve of animal origin were applied to isolated rabbit gutin vitro, two characteristic responses were obtained, associated with the α- and β-lytic titres respectively, and abolished by the corresponding antisera. They were independent of the origin of the strains.2. A non-specific response is also described which is thought to be due to the peptone in the medium.3. No effect that could be attributed to enterotoxin, such as was reported by Anderson (1953), was observed and it is concluded that isolated rabbit gut is unlikely to prove a useful indicator of its presence.We are indebted to Drs Mary Barber, J. M. Talbot, F. C. O. Valentine and H. Williams Smith for strains; to Dr R. E. O. Williams for strains and bacteriophage typing; to Prof. C. E. Dolman and Messrs Burroughs Wellcome for strains and antisera; to Mr F. Crisp of the Division of Experimental Biology, National Institute for Medical Research, Medical Research Council, for rabbit gut; and Dr H. O. Schild for continued interest and practical help.

Summary The resistance of vegetative cells of CI. welchii to low pH was tested in gastric juice and in peptone water of pH 1·5–3·6. The results showed that, for any given strain the death rate increased with decreasing pH; the death rate was dependent on the age of the culture—for cells grown in cooked-meat medium a 5-hr culture was more susceptible to low pH than a 24-hr culture of the same strain; the cells were more susceptible to gastric juice than to peptone water of the same pH.

Experiments carried out by the British Egg Marketing Board in order to establish a heat treatment which would effectively pasteurize liquid whole egg are described.The results of large scale bakery trials and subsequent trade demands indicate that the recommended pasteurization treatment gives a product of a satisfactory baking performance.It is recommended that for the adequate pasteurization of whole-egg products, a temperature of 64·4°C. (148° F.) for the minimum holding time of 2·5 min. should be used.

Two methods for the detection of salmonellae in foods were compared in 179 imported meat and egg samples. The number of positive samples and replications, and the number of strains and kinds of serotypes were statistically comparable by both the direct enrichment method of the Food Hygiene Laboratory in England, and the pre-enrichment method devised for processed foods in the United States. Boneless frozen beef, veal, and horsemeat imported from five countries for consumption in England were found to have salmonellae present in 48 of 116 (41%) samples. Dried egg products imported from three countries were observed to have salmonellae in 10 of 63 (16%) samples. The high incidence of salmonellae isolated from imported foods illustrated the existence of an international health hazard resulting from the continuous introduction of exogenous strains of pathogenic microorganisms on a large scale.

1. In good quality raw milk reducing methylene blue at 37–38° C. members of the coliform group andStaph. aureuswere among the commonest organisms present at the time of reduction. Other types of staphylococci, micrococci, and certain streptococci were not infrequently present in smaller numbers. In any given milk one type of organism tended to assume predominance.2. Using the modified test described by Wilsonet al.(1), various organisms isolated from milk at the time of reduction were examined for their rate of decolorization of methylene blue when growing in pure culture in raw “sterile” milk (milk freshly drawn from the healthy udder under aseptic conditions and having a plate count on milk agar at 37° C. of 200–300 per ml.). The most rapidly reducing organisms belonged to the coliform group. Following them, in decreasing order, cameStr. lactisand some of the faecal streptococci,Staph. aureus, Staph. albus, Staph. citreus, some micrococci, group C haemolytic streptococci and some strains ofStr. agalactiae, and aerobic spore-bearers

The conditions of heating necessary to destroy salmonellae in liquid whole egg have been compared with those necessary to destroy the activity of the α-amylase of whole egg. All conditions of pasteurizing from the mildest at 61·1° C. (142° F.) for 1 min. to the most severe at 65·5° C. (150° F.) for 5 min. eliminated Salm. typhimurium. The heat-resistant strain of Salm. senftenberg N.C.T.C. 9959 (775 W) was not recovered after heating at 64·4° C. (148° F.) for 2½ min. and at the lower temperatures when the heating period was 3 min. or more. The activity of α-amylase was also destroyed by heating at 64·4° C. (148° F.) for 2½ min. but not at lower temperatures.Because the baking properties of egg are not impaired by heating at 64·4° C. (148° F.) for 2½ min. it is proposed that the inactivation of the α-amylase of whole egg can be used as a test for controlling the pasteurization process, and a routine test has been developed which can be completed within 1 hr.

The results just described for Greater London compare very favourably with those of similar surveys carried out in the United States by Hopkins & Kelly (1919), Smith (1923), and Layson, Huffer & Brannon (1936) (see also Report, 1934). The figures recorded in Table 7 show that approximately 50% of bottles from the large, the small rotary, and the steam sterilization plants conformed to a standard of less than 600 colonies per pint bottle, or approximately 1 colony per ml. capacity.The figures for the small rotary plants were not so good as for the large plants, there being a greater proportion of high counts among these. The same was even truer of the steam sterilization plants, in which about a quarter of the bottles were grossly contaminated. The results with the plants using hand-washing only were bad, none of them falling below the 2500 mark.The general conclusions to be drawn from this survey are that equally good results may be obtained in large or in small rotary plants relying on treatment with hot caustic detergent as in plants employing steam sterilization, and that the uniformly best results are obtained in properly designed and operated plants of the spray type.

SUMMARY The cleaning and bactericidal efficiencies of a number of detergents were estimated by laboratory tests, the techniques of which are described. Field trials with some of the detergents in a small and a large canteen gave results similar to those obtained in the laboratory. The ability of Salmonella paratyphi B to survive and grow after inoculation into samples of used dish water obtained from a small canteen was demonstrated.

Quantitative observations were made on the rate of disinfection ofBacterium coliand of the spores ofBacillus subtilisby caustic soda at different temperatures and different concentrations. The tests were carried out in the presence of 1/1000 milk. It was found that:(1) WithBact. colithe concentration coefficientnwas about 2·7, and the temperature coefficient θ10°C.about 2.(2) WithB. subtilisspores the concentration coefficientnwas about 1·75 and the temperature coefficient θ10°C.about 1·5.(3) WithBact. colithe values for the reaction velocity constantktended to be irregular at 40° C. and withB. subtilisspores at 70° C, suggesting that at these temperatures some additional factor, presumably heat coagulation of the protein, was beginning to affect the results.(4) With both organisms the value of the reaction velocity constantkwas relatively slow at the start and tended to increase progressively during the course of disinfection. Whether it diminished again as sterility was approached could not be ascertained for technical reasons.(5) With both organisms the presence of 1/1000 milk did not seem to affect the rate of disinfection as compared with distilled water.(6) One experiment withBact. colisuggested that the rate of disinfection was affected appreciably by the number of organisms present. Increasing the number of organisms in the suspension 100 times diminished the value ofkby about one-third.(7) The value ofkwas about 3,000,000 times greater withBact. colithan withB. subtilisspores.(8) If the mean value ofnis taken as 2·2, it follows that doubling the concentration of caustic soda increases the reaction velocity by 4·6 times. If, for example, with a given concentration of caustic soda sterility was reached in 9 min., then doubling the concentration would reduce this time to 2 min., while halving the concentration would increase it to about 40 min.(9) If the mean value of θ10°C.is taken as 1·75, it follows that a rise of 10° C. in the temperature increases the reaction velocity 1·75 times. If, for example, with a given temperature sterility was reached in 9 min., then raising the temperature 10° C. (18° F.) would reduce this time to about 5 min., while lowering the temperature 10° C. would increase it to about 15 min. With temperatures, however, of over 40° C. (104° F.) the rate of destruction of yegetative organisms, and with temperatures of over 70° C. (158° F.) the rate of destruction of sporing organisms in the presence of caustic soda is probably increased by the effect of the heat itself.(10) A comparison of our figures for caustic soda with those of Chick for phenol shows that a 0°05% solution of caustic soda at 20° C. destroyedBact. coliabout five times as fast as a 0°5% solution of phenol at 20° C. destroyedBact. paratyphosumB, and that a 5% solution of caustic soda at 30° C. destroyedB. subtilisspores nearly three times as fast as a 5 % solution of phenol at 33·3° C. destroyed anthrax spores. The superiority of caustic soda over phenol, particularly at concentrations likely to be used in practice, is manifest.(11) Discussing the standardization of disinfectants, we conclude that the value ofktaken in the middle stage of the reaction, or from the beginning of disinfection to about the end of the middle stage, affords the most suitable measure of comparison. This is essentially the same conclusion as that reached by Withell (1942), who uses as his index the time necessary to destroy 50% of the organisms.

For many years there have been outbreaks of para typhoid fever associated with the .consumption of imitation cream cakes and other confectionery made in commercial bakeries. One suspected means of entry of the paratyphoid bacillus into these bakeries has been contaminated products in common use (Cockburn et al., 1951 ; Thomson, 1953). In 1954 two of us investigated a series of outbreaks of paratyphoid fever associated with bakeries where one small batch of Chinese frozen whole egg, used in all the bakeries concerned, was thought to have been contaminated, but where only a small amount was available for examination (Newell, 1955 ; Smith and Hobbs, 1955 ; Newell et al., 1955). Various salmonellae were found, but not Salmonella paratyphi B. In the present report are recorded two outbreaks of paratyphoid fever in August, 1955, one in the Worthing area and the other in the Weymouth area ; bakery pro ducts were suspected of being directly responsible for the infection, and a batch of Chinese frozen whole egg used in the two bakeries appeared, on epidemiological grounds, to be the source of contamination. The epi demiological observations were confirmed by the isola tion of the same phage type of Salm. paratyphi B from unopened cans of the egg, from some of the bakery staff, and from the patients.

Excretion ofEscherichia coli 04 affecting babies with diarrhea, was investigated in a neonatal nursery. Two episodes of infection occurred separated by a period of about three months. In the second outbreak of 21 babies excretingE. coli 04, 11 had diarrhea and 10 appeared to be healthy. Diarrhea occurred more frequently in preterm infants fed by means of nasogastric tubes than in those who were bottle and breast fed. Washings from the feeding tubes in culture showedE. coli 04 in two tubes andPseud monas andStaphylococcus aureus in others. Measures taken to control the spread of infection are described. Hand hygiene was considered to be particularly important.

1. A bacteriological laboratory was provided in the medical departments of two passenger ships—a modern luxury liner cruising in the Mediterranean for 1 month and an older vessel, now out of commission, on a 3 months round voyage through the tropics. Galley hygiene in relation to gastro-enteritis was investigated on both ships.2. 125 samples of water and iced water were examined. Samples of water chlorinated on the ships were usually satisfactory. Many port waters sampled from the barge or hosepipe were contaminated—some mildly, some profusely. A fault in an ice-making machine led to pollution of ice used for various purposes. Swimming-bath water was usually mildly polluted only; occasionally in the tropics when the baths were very popular the count rose to 1600 Esch. coli per 100 ml.3. Thirty-five samples of milk, ice-cream and churn washings were examined. English liquid pasteurized milk stored in the cold gave satisfactory results, but the rehydrated dried milk used exclusively on the round voyage through the tropics and swabs from the apparatus used in its preparation were contaminated with Esch. coli. Ice-cream samples from ship I gave satisfactory results, and of two samples of ice-cream powder examined on ship II one was satisfactory and the other gave a poor result. Occasional churns which had been superficially cleaned but not sterilized had a high general and Esch. coli count.4. 189 samples of food were examined, twenty-two for general and coliform counts only. Results were variable according to foodstuff and atmospheric temperature. Some cold cooked meatstuffs gave low counts and absence of coliform bacilli in 1/10 g.; others had plate counts of 300,000 to 25 million per gram with Esch. coli in 1/1000 dilution, e.g. crayfish ready for the table. Salmonellae were not found in any samples but occasionally small numbers of coagulase-positive staphylococci and non-haemolytic Cl. welchii were isolated.5. Sixteen samples of imitation cream and washings from savoy bags were examined. Samples from freshly opened cans of cream gave satisfactory results. In whipped cream and in cream from cakes and sweets, Esch. coli was found in 1/1000 dilutions, and rinsings from savoy bags in use gave probable numbers of Esch. coli of 18,000 + / 100 ml. Counts were still high after the bags had been washed and dried and they were far from sterile even after ‘boiling’ and drying.6. Twenty-three samples of wash water from salad vegetables and fruit had high counts of Esch. coli. After these articles had been washed in water containing 80 p.p.m. sodium hypochiorite, coliform organisms were not found in 100 ml. of water. Potassium permanganate was considered to be of doubtful value. The results of laboratory experiments to confirm the concentration of hypochiorite and time necessary to destroy Esch. coli on lettuce and watercress are shown in Tables 3 and 4.7. Results from forty-four samples of wash and rinse waters from dish-washing machines and one bowl showed that the temperatures were often too low; with temperatures above 50° C. coliform bacilli were absent in 1 ml. quantities, but waters at temperatures below 42° C. gave probable Esch. coli counts of 1800 + / 100 ml. The bacteriological condition of the crockery and cutlery varied according to the wash and rinse waters. Rinses from metal dish covers gave poor results, with 1800+ Esch. coli per 100 ml. of rinse and occasionally Cl. welchii and coagulase-positive staphylococci. Wash and rinse waters, with temperatures of 35°ndash;42° C. used for pots and pans gave probable Esch. coli counts of 1800 + /100 ml.8. Rinse waters from twenty cloths used in the galleys, pantries and dining rooms were nearly all heavily contaminated with Esch. coli, with probable numbers of 18,000 + /100 ml.; these counts were reduced to negligible figures by soaking the cloths in chloride of lime.9. Swabs were taken from thirty-eight cutting-boards and twenty-six surfaces of sinks, shelves and miscellaneous articles. Many boards were heavily contaminated, the probable number of Esch. coli being 18,000 + /100 ml. of diluent; lecithinase-positive clostridia were found also. The boards could be sterilized by brushing with a stout wire brush followed by chlorination.Other surfaces, and swabs from various knives in the kitchen, including the blade of the slicing machine, frequently gave high counts of Esch. coli.10. 329 swabs from nostrils and fingers of saloon and galley staffs yielded one cutlure of coagulase-positive staphylococci from 111 nasal swabs and three cultures of coagulase-positive staphylococci and seven of Esch. coli from 218 finger swabs from twenty-seven men.11. Twenty-eight faecal specimens were examined from fifty-four cases of gastro-enteritis reported on the Mediterranean cruises; salmonellae were not found, but heat-resistant Cl. welchii was isolated from six samples (21%), and the clinical picture was that of Cl. welchii food poisoning.12. 121 faeces samples from 137 patients with gastro-enteritis were examined chiefly for salmonellae and coagulase-positive staphylococci on the outward leg of the round voyage through the tropics. Salm. typhimurium was isolated from a clinical case and Cl. welchii from one typical case of food poisoning. On the return journey all samples were examined also for Cl. welchii; of thirty-five stool samples from thirty-five patients, six (17%) yielded lecithinase-positive clostridia; salmonellae were not found.13. Heat-resistant strains of Cl. welchii were also isolated from two chopping-boards, a knife, cold beef, brawn, two wiping cloths, a dish cover, two samples of pie and corned beef.

SUMMARYThe use of a gamma radiation process for the elimination ofSalmonellafrom frozen meat is considered with particular reference to the treatment of boned-out horsemeat and kangaroo meat imported into the UK and intended for use as pet meat.Examination of dose/survival curves produced for several serotypes ofSalmonellain frozen meat shows that a radiation dose of 0·6 Mrad. will reduce a population by at least a factor of 105. The influence on the radiation resistance of salmonellas of such factors as preirradiation growth in the meat and temperature during irradiation have been examined and considered. It is also demonstrated with both preinoculated and naturally contaminated meat that postirradiation storage in the frozen state does not lead to the revival of irradiated salmonellas.The properties ofSalmonellasurvivors deliberately produced in meat using conditions of irradiation designed to simulate a commercial process are studied after six recycling treatments through the process. There were no important changes in characteristics normally used for identification ofSalmonellabut radiation resistance was lowered. Survivors grownin situin meat after irradiation showed an abnormally long lag phase, and removal of competitive microflora in meat by the radiation treatment can influence the growth of salmonellas.

It has been known for some time that egg products may contain members of the Salmonella group capable of causing food poisoning, and the position has been rendered more serious by the recent discovery of S. paratyphi B in some of the samples of egg products imported into the United Kingdom. Attempts to destroy salmonellae in liquid egg by pasteurization before freezing or drying have met with considerable success but the process requires careful control. In any case, at the present time most of the frozen whole egg consumed in the United Kingdom has not been pasteurized. The tins in which the frozen product is distributed hold up to 20 kg, and are therefore of a size suitable for treatment with γ-radiation. After treatment of small samples of frozen whole egg with 2 MeV cathode rays it was concluded that a dose of about 0·3–0·5 Mrad would destroy the numbers of salmonellae normally encountered in the product without impairing the baking qualities of the material. Whole tins, each containing 10 kg of infected material, were therefore irradiated in the frozen state with Co 60 γ-rays. Two tins were treated at each of three dose levels of 0·3, 0·4 and 0·5 Mrad. No salmonellae were detected in duplicate samples of 25 g of material taken from each of the tins after irradiation. If the effectiveness of the treatment is confirmed, the process has obvious attractions since it dispenses with the need to thaw or otherwise to handle the product. The paper also contains a general discussion on the irradiation of eggs and egg products.

Experiments were made to find out whether the common communion cup is likely to serve as a vehicle for the transmission of infection.A silver chalice and sacramental wine containing 14·5% of alcohol were used. Observations with volunteers showed that the number of organisms deposited on the rim of the chalice varied from person to person, but was usually quite small—less than 100.Rotation of the cup was of no benefit except to those partaking during the first round, since the saliva deposited on the rim by each person in turn remained to contaminate the cup during the second round, and the combined effect of the alcohol and the silver of the chalice was not rapid enough to destroy the contaminating organisms before rotation of the cup was completed.On the other hand the use of a linen cloth or purificator led to a diminution of about 90% in the bacterial count of the cup.Organisms in saliva deposited on the interior of the dry chalice suffered some diminution in numbers within 8 min., presumably as the result of the disinfectant action of the silver, but the effect was too small to be of significance.When suspended in wine and deposited on the internal surface of the chalice Escherichia coli suffered a substantial reduction within 3 min., Streptococcus pyogenes was destroyed completely; but Staphylococcus aureus was affected to a much less extent.Various experiments designed to measure the disinfectant action of wine, and of silver and wine together, showed that the augmenting effect of silver on the disinfectant action of the alcohol was quite small. Strep. pyogenes proved to be far more sensitive to alcohol than Esch. coli, Staph. aureus and Serratia marcescens. Under the conditions of the experiment these last three organisms were not destroyed for 10–12 min., whereas Strep. pyogenes perished within 1½ min.The results of our work are in general agreement with those of previous workers, and show that the organisms deposited on the rim of the communion cup are not destroyed within the short time—5 sec. as an average—elapsing between the partaking of the sacrament by each successive communicant.It must therefore be admitted that the common communion cup may serve as a means of transmitting infection. Reasons are given, however, for believing that the risk of transmission is very small, and probably much smaller than that of contracting infection by other methods in any gathering of people.Such risk as there is could be greatly diminished by the use of a purificator for wiping the cup between each communicant, and could be abolished completely by substituting individual cups or by the practice of intinction.

Studies on the use of gamma radiation for the elimination of salmonellae from whole egg, frozen horse-meat, desiccated coconut and bone meal show the extent to which the nature of the medium influences the resistance of these organisms to gamma radiation. There is also a variation in radiation resistance between different serotypes; S. typhi-murium was consistently the most resistant of those examined.Based on experiments with artificially inoculated or naturally contaminated products, and also on dose/survival curve data, the dose requirement for the elimination of salmonellae from frozen whole egg is estimated at 0·5 Mrad., which gives a 107 reduction in numbers of S. typhi-murium; for frozen horsemeat 0·65 Mrad., giving a 105 reduction; and for bone meal between 0·5 and 0·75 Mrad., giving between 105 and 108 reduction. A dose of 0·45 Mrad. appears effective for desiccated coconut, with a reduction of 103, but such a radiation dose affects the quality of this product.We are grateful to Dr E. S. Anderson of the Enteric Reference Laboratory for phage typing and for the provision of a strain of S. typhi-murium for experi ments. Also we thank Dr Joan Taylor of the Salmonella Reference Laboratory for the serological typing of salmonellae, and Miss M. E. Smith and other colleagues of the Food Hygiene Laboratory who carried out the routine bacteriological examination.We wish to thank Mr N. C. Roberts of J. Rannoch Ltd. for his co-operation in the large-scale frozen egg experiment, and also Mrs G. M. Ison of S. Wallace Ltd. in respect of the experiment on frozen horse-meat.

1. The growth in synthetic cream of certain pathogenic bacteria may be inhibited by two methods:(a) By limiting the ingredients to cooking fat or other fatty material, excluding margarine or butter, emulsifying agent such as methyl cellulose, sugar and salt. The cream must not then be left in contact with confectionery from which nutritive material may be absorbed. This last condition renders the method impracticable as a means of control.(b) By the addition to synthetic cream, including those containing milk and egg, of a bacteriostatic agent such as hydrogen peroxide.2. Contaminants may grow in emulsified fats in the absence of protein. These are probably lipolytic organisms which are able to utilize the products split from the fat. Organisms such as coagulase-positive staphylococci, Salmonella paratyphi B, and Bacterium coli, tend to die out within 24 hr. or after a few days in creams lacking protein.3. The concentration of H2O2 necessary to inhibit the growth of test organisms is dependent on the ingredients of the cream. In the presence of butter, milk and egg yolk at least three times the concentration of H2O2 is necessary as when emulsified fat without added protein is used. The suggestion is made that concentrations of H2O2 from 0·005 to 0·02% should be added to all commercially produced synthetic cream, the actual concentration used depending on the constituents of the cream.4. To prevent the growth of contaminating organisms in commercially produced synthetic cream, H2O2 should be added immediately after pasteurization and cooling when the bacterial count is still low. Even comparatively high concentrations of H2O2 will not inhibit or control the growth of bacteria already present in large numbers.5. The inhibiting power of 0·012% of H2O2 remained effective in a fat-emulsion cream and also in a laboratory cream containing margarine, egg and milk for 3 weeks at + 4 and 20° C.; at higher temperatures of storage the stability of the oxidizing agent is doubtful.6. Since synthetic cream is exposed to so many different sources of contamination, particularly in the bakery, and since there is no method of controlling the growth of pathogenic organisms that have gained access to it other than by the addition of a bacteriostatic agent, it is strongly recommended that the present regulations on preservatives should be altered to allow the addition of H2O2 in suitable concentration to synthetic cream.We are grateful to all those who have helped in the supplies of material, and in particular we wish to thank the Public Health Department, St Pancras Town Hall; Mr E. Capstick, United Dairies Ltd.; Mr J. Valentine Backes, President, Bakery Allied Traders' Association; and also Messrs Bakcos Catering Supplies Ltd., A. Bellamy and Co. Ltd., Farma Cream Products Ltd., Krema Ltd., Malga Products Ltd., Ramsay, Braddon and Co. Ltd., Quality Foods Ltd., Sunnyside Products Ltd., Unicream Ltd., and Vitacream Ltd.We are indebted to Mr L. Bailey for his technical assistance.

SUMMARYSalmonella senftenberg was isolated from 168 patients and staff of a general hospital whereas it was isolated from only seven other sources (four of which were unquestionably associated with the hospital) in the surrounding area during the same period. It was isolated in the hospital in 19 of the 48 months of the period. Two clear-cut episodes were recognized against a background of sporadic isolation. Four-fifths of the patients and staff excreting the organism had no symptoms. Only two are known to have been severely ill, though in some patients very ill for other reasons life may have been shortened a little.The original source of the organism, whether from the farm or from raw materials such as meat or poultry, was not found.

1. Of 1552 strains ofStaph. pyogenestested by the slide-agglutination technique, using the absorbed and unabsorbed sera suggested by Cowan, 74% of strains were identified while 26% remained untyped. Of untyped strains, half were inagglutinable while the remainder gave ‘indefinite’ results and remained unclassified. The introduction of two new sera, used diluted but unabsorbed, considerably reduced the number of untyped organisms but made little difference to the proportion of ‘indefinite’ strains. The method was simple and quick, but the variety of cross-reactions often prevented a clearcut differentiation of strains and the number of types identifiable was limited.2. Of three methods of agglutination, titrations on glass slides were preferred because by this technique end-points were clearer than those obtained in a water-bath or by the method for determination of Vi antibody.3. Agglutination of seventeen strains ofStaph. pyogeneswith homologous and heterologous sera showed that the use of unabsorbed sera was of limited value for typing because of the marked cross-reactions.4. Christie & Keogh's division ofStaph. pyogenesinto nine types was promising but their absorbing methods allowed much antigenic overlap.5. Experiments with absorbed sera showed that no single strain ofStaph. pyogenescould be used successfully to absorb all sera. There appeared to be groups or pairs of types in which serologically the individual members resembled each other very closely and yet were not identical. In these instances the absorption of a serum by a heterologous strain nearly related to the homologous strain proved of most value in the preparation of specific sera.6. A set of seventeen absorbed sera was prepared from Cowan's three types ofStaph. pyogenes, from six of Christie & Keogh's type strains and from eight additional strains freshly isolated from staphylococcal lesions. With some absorbed sera there was specific agglutination with the homologous strain and no heterologous reactions, other sera reacted with several strains and could not be made specific.7. Seven specific serological types were recognized while a further eight types showed less specific reactions and were identifiable by a pattern of reactions. A number of strains differed slightly one from another in their agglutination reactions, and it was not possible to decide whether these were additional types or variants within types.8. In a small series of experiments the precipitin reaction, using unabsorbed sera, seemed of little value in the differentiation of strains ofStaph. pyogenes.9. Of 259 coagulase-positive strains examined during 1946 and 1947, all were identified by agglutination reactions, although they varied in their specificity; 67.5% of these strains were identified by staphylococcal bacteriophage reactions.10. A preliminary comparison of serological and bacteriophage types showed a fairly regular but not complete correlation between the results obtained by the two methods. A number of serological types were regularly lysed by the same bacteriophage filtrates; a few were consistently untypable by phage indicating that filtrates had not as yet been found for them or that the strains were phage resistant.Others which were not clear-cut in their reactions and which were recognized by patterns of reactions with both sera and phage filtrates did not always show a close correlation in the typing results.11. The application of both serological and bacteriophage typing to the investigation of outbreaks of staphylococcal infection has proved to be of value in tracing sources and paths of spread of infection. In several instances the use of both methods of typing has led to conclusions which would not have been warranted if one method alone had been used.

SUMMARYA comparison was made of beef cooked in conventional and moist air (Rapidaire) ovens. In both large (ca.4·5 kg.) and small (ca.2·7 kg.) joints, spores ofClostridium welchiisurvived after cooking but vegetative cells,Escherichia coli, andStaphylococcus aureus, did not, regardless of the type of oven usedCooling at room temperature after cooking permitted growth ofCl. welchii. Although some multiplication also occurred in the centre of large roasts cooled under refrigeration, the viable counts were considered too low to constitute a potential health risk

SUMMARYDetails of confirmed outbreaks of food poisoning due to heat-sensitive Cl. welckii are given. In 4/5 incidents heat-sensitive Cl.welckiiwere 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.welckiiwere isolated are described.The role of heat-sensitive Cl.welckiiin food poisoning outbreaks is discussed and a suggested method of examining faeces for Cl.welchiiis 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.

Causes and Effects of Columnaris-type Diseases in Fish: Species of Corynebacterium and Pasteurella isolated from Diseased Salmon, Trout and Rudd