The serum opacity reaction (SOR) is produced by some streptococci of group A, but not by streptococci of groups B, C, D, F and G. The production of this reaction was found to be closely related to serotype as determined by M and T antigens. The SOR of an individual strain was found to be consistently stable over a period of time both in strains maintained in the laboratory and in strains isolated sequentially from individual patients following streptococcal infections. Strains for which the demonstration of an M-antigen by the precipitin method was difficult or impossible in general produced a SOR, while strains more easily typable generally failed to produce this reaction. Laboratory selected variants of type 12 strains showed an inverse relationship between M protein and lipoproteinase production, whereas M positive and M negative variants of other serotypes showed no variability with respect to lipoproteinase production.

Visits have been made to thirty operating suites in the British Isles. Each suite was visited three times at approximately 4-month intervals and observations made on an average of five half-day working sessions on each occasion. Measurements were made of air temperature, humidity, air movement and radiation temperature and many details of the suites and working conditions recorded. At suitable intervals the operating room staff were questioned as to their feelings of thermal comfort using Bedford's 7-point scale. Over 2500 sets of replies were obtained. Visible sweating was also noted.

The effect on comfort and the extent of visible sweating of the many items recorded was then explored by means of a sequential multiple regression analysis. Although air temperature was by far the most important factor affecting thermal comfort, all the variables named above exerted a significant effect. In addition, a number of other conditions including age, sex and race produced minor differences.

Surgeons and anaesthetists were found to differ from other staff in their thermal preferences, the surgeons liking a cooler and the anaesthetists a warmer environment. Although most surgeons were comfortable at temperatures around 66·5°F. (19°C.), at 50% relative humidity and 25 ft./min. air movement with the average amount of thermal radiation from the operating room lamp, it would be necessary to keep the temperature down to 64·5°F. (18°C.) if no more than one surgeon in twenty was to be uncomfortably hot. At this temperature nearly half the anaesthetists, who mostly preferred temperatures around 71°F. (21·5°C.), would feel too cold. Variation in the clothing worn by different staff members seems to be the only way of resolving this difficulty.

The average temperature in the operating rooms visited was over 72°F. (22°C.), and 75°F. (24°C.) was exceeded on about 25% of occasions.

Evidence was presented to support a hypothesis that competition between antibody molecules can be an important factor in vaccinia virus neutralization.

It has been shown that there is little difference in the virus neutralizing properties of 7 S and 19 S antibody and it has been further postulated that in the context of protective immunity the proportions of antibodies having neutralizing and interfering effects is likely to be more important than the absolute concentration of neutralizing antibody or the type of immunoglobulin in which it is present.

In three separate series, samples were examined for salmonellas by culture in selenite F broths incubated at 37 and 43° C. The samples used were:

(1) Gauze swabs placed in sewage.

(2) Gauze swabs placed in drains in abattoirs.

(3) Sewage-polluted river water.

In each series the higher temperature gave better results.

The modification of tetrathionate broth for incubation at 43° C. and the adjustment of the incubation temperature to suit more inhibitory enrichment broths is discussed. The medium of Rappaport, Konforti & Navon (1956) is not suited to incubation at 43° C.

We should like to acknowledge the help of Prof. Scott Thomson in the preparation of this paper, and the capable technical assistance of Mr T. R. Liddington and Mr John Morgan. We are also indebted to Dr H. Campbell, Senior Lecturer in Medical Statistics in the Welsh National School of Medicine, for his advice and to Mr M. C. Finniear, Deputy Public Analyst of the Glamorgan County Public Health Laboratory, for the calculation of molar tetrathionate in Rolfe's tetrathionate broth.

1. An explosive outbreak of gastroenteritis that affected 40–50% of people in a town of 10,800 inhabitants (Montrose) is described.

2. There is epidemiological evidence that the outbreak was water-borne. The chlorination of the water supply was faulty at the time of the outbreak.

3. Echovirus type 30 and two types of Coxsackie B viruses were isolated from sixteen out of thirty-two patients examined.

4. Shigella sonnei was isolated from the faeces of 110 out of 262 patients and contacts examined. Fifty-six strains tested for colicine activity were all colicine type 4 and had the same antibiotic sensitivity pattern.

5. This particular strain of Shigella sonnei (Montrose strain) spread to surrounding areas, although it disappeared quickly from Montrose.

6. The problem of inactivating virus in water supplies contaminated with sewage is discussed briefly.

We wish to acknowledge the help given by the general practitioners of Montrose and the staff of the Public Health Department of the County of Angus in the collection of specimens and information during the outbreak. We would also like to thank the Laboratory staffs of the diagnostic laboratory and virus laboratory of the Bacteriology Department, University of Dundee and the staff of the laboratory, Stracathro Hospital, for invaluable assistance. We are indebted to Dr R. R. Gillies, Epidemiology Unit, Bacteriology Department, University of Edinburgh, who kindly carried out colicine typing for us and supplied us with strains from his collection, and to Dr R. M. Gordon, Senior Medical Officer, Scottish Home and Health Department and Mr H. F. Scrimgeour, M.I.C.E., A.I.W.E., Engineering Inspector Scottish Development Department, for their assistance during the investigation.

Plaque neutralization on HEp 2 cells was used to determine the relationship between vaccinia, rabbitpox, cowpox and ectromelia using both 7 S and 19 S antibody. It was shown that for the strains of virus used vaccinia and rabbitpox were very similar but cowpox and particularly ectromelia were clearly distinguishable. The cross-titration relationships were the same for 7 S and 19 S antibody.

The titration slopes and kinetics of cross-neutralizations were interpreted on the basis of a hypothesis of antibody competition put forward in the preceding paper. It was tentatively concluded that these four viruses share a common critical antigen for neutralization and that differences in the structure or presentation of neighbouring antigens could give rise to some of the observed effects.

A comparison was undertaken of several serological tests in determining the response of chickens and turkeys experimentally infected with the A 514 strain of Mycoplasma gallisepticum.

After a single intratracheal inoculation of chickens with a culture of the organism, the highest titres were obtained by the indirect complement fixation (ICF) test, followed by the tube agglutination (TA), haemagglutination inhibition (HI), slide agglutination (SA) and metabolic inhibition (MI) tests. By all these tests positive titres were observed within the first week and peak titres between the first and second weeks. At 5 months there was no positive reaction by the ICF test but most chickens gave positive readings by the TA, HI and SA tests for at least 14 months after infection, but turkey sera became negative by all tests after 3 months.

A disadvantage of the ICF test was that sera up to a dilution of 1/8 and 1/16 for chicken and turkey respectively were anticomplementary, and in turkeys this masked the ICF titre, which presumably was low following one intratracheal inoculation. Titres in turkeys with the TA, HI and SA tests followed the pattern seen with chickens and were generally lower than those found by other workers probably because of the avirulent nature of the inoculum used.

The WB test was the least sensitive of the agglutination tests but is useful as a flock test which can be undertaken on the farm.

The MI test gave the lowest titres of all and antibodies could be detected for only 4 months following one intratracheal inoculation. Even with serum prepared by multiple inoculations in chickens the titre was never higher than 1/32 compared with 1/1024 for serum similarly prepared in rabbits.

Precipitins were detected by the agar gel method in the sera of chickens and turkeys after two intratracheal inoculations but in only some of the chickens and none of the turkeys after one inoculation.

By all tests higher titres were observed with chicken than turkey sera and antibodies persisted for a longer time.

Re-infection of chickens when antibodies to the initial infection had become low, and of turkeys when antibodies were no longer detectable, gave rise to an anamnestic response with titres which were higher than before.

Antiserum to M. gallisepticum prepared in chickens is comparable with that prepared in rabbits except for low titres by the MI test.

An investigation was carried out on the influence of the mode of transport at ca. 21° C. on the fate of S. typhimurium, E. coli, Ps. aeruginosa, Staph. aureus, Str. pyogenes and spores of B. cereus collected from surfaces by swabbing with cotton and alginate.

Transport at relative humidity 0·58–0·95 leads to losses in viable counts sometimes exceeding two log cycles. In Stuart's medium and Ringer-calgon particularly Enterobacteriaceae showed growth when transported at 21° C. Reduction of the pH value of Stuart's medium led to losses of far over one log cycle in some types of bacteria and could therefore not be recommended.

Slight chilling of the medium, e.g. to 12° C., and insulation during transport appeared to maintain counts of the organisms studied at their original level in both Stuart's medium and Ringer calgon for 10–12 hr.

Wet spores of fourteen strains of Clostridium, representing eight species, were enumerated in four different types of thioglycollate agar and in a similar medium in which thioglycollate was replaced by cysteine-HCl. Thioglycollate appeared to be toxic, in principle, to almost all strains tested, although the degree of toxicity was influenced by other components of the medium. These experiments entirely confirm earlier observations and must lead to the conclusion that the use of thioglycollate in sterility test media should be discontinued and that cysteine-HCl should be used as the redox potential reducing compound instead.

Suspensions of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Klebsiella aerogenes and micrococci were tested for survival on drying and after drying in the atmosphere. The proportion of Gram-negative bacilli that died during drying was greater than that of the Gram-positive cocci, but survival after drying was similar in the two groups of organisms. There were considerable differences in the death-rates on drying of different strains of bacteria, which were consistent on replicate sampling.

A suspension of Ps. aeruginosa prepared from cells which had survived one drying showed a considerably higher proportion of survivors on a second drying; suspensions prepared from subcultures of the dried cells, however, showed a death-rate on drying which was similar to that of the original culture.

Strains of Ps. aeruginosa isolated from floor dust showed a significantly higher proportion of survivors immediately after drying than strains from patients, but the proportion of survivors after 24 hr. of exposure to the atmosphere was approximately the same in the two groups.

Tests were made for survival of Ps. aeruginosa and Staph. aureus in deionized water, tap water, physiological saline and Ringer's solution. In deionized water, Ps. aeruginosa showed a rapid initial loss but some survival for several weeks; Staph. aureus, on the other hand, showed an initial increase in numbers but no survivors after 48 hr. In Ringer's solution all strains of Ps. aeruginosa multiplied rapidly and survived for many weeks; Staph. aureus died rapidly and no strain could be detected after 4 days.

We are grateful to Dr M. T. Parker and Mrs E. Asheshov for the typing of strains of Pseudomonas aeruginosa.

Poliovirus type 1, strain LSc2ab, was directly sprayed in a static air cabinet at 20° C. and sampled afterwards with impingers. Virus inactivation during spraying was maximal in dry air; during storage maximal decay occurred at moderate humidity.

With regard to the mechanism of the inactivation the following facts have been observed: (1) The RNA in the virus decays simultaneously with the whole virus particle. (2) Oxidation does not play any significant role. (3) Incubation with L-cystine protects the virus against inactivation at 50° C. in aqueous suspension, but not against decay in aerosols.

On the strength of these observations it is concluded that in aerosols denatura-tion of the viral RNA is the cause of the inactivation of poliovirus. The decay in aerosols has some features in common with the thermal inactivation in aqueous suspensions at room temperature.

Oxoid dehydrated MacConkey broth was compared with laboratory prepared MacConkey broth, Teepol broth and three modifications of glutamic acid media, by participants in eleven laboratories. A variety of chlorinated and unchlorinated water samples were used. The Oxoid MacConkey broth was shown to be a satisfactory standard for comparison. Teepol broth was found to be a satisfactory alternative to MacConkey broth. Gray's improved glutamate medium was shown to be the best of the glutamate media and it gave results superior in most respects to MacConkey broth. In particular more Escherichia coli were obtained as well as more coliform organisms. Organisms surviving marginal chlorination were recovered more readily. Growth was sometimes slower than in MacConkey broth but this could possibly be improved by closer attention to pH adjustment and mineral composition.

Two strains of rubella virus multiplied in organ cultures of human embryonic trachea, nasal epithelium, pharynx, larynx, skin and brain derived from foetuses aged 15–28 weeks. Growth curve experiments conducted on cultures of nasal epithelium and trachea showed that virus appeared in the culture fluid 72 hr. after inoculation and thereafter rose to titres varying from 10 to 103·7TCD50/ml. These titres persisted for periods up to 34 days after inoculation. Intracelmlar and organ culture fluid virus titres were shown to be similar in specimens tested in both the early and late stages of the growth curve. No degenerative changes or loss of ciliary activity was observed in these cultures.

We are grateful to Dr H. E. M. Kay and his staff (Royal Marsden Hospital), for the supply of human embryos; Dr D. A. J. Tyrrell (M.R.C. Common Cold Research Unit, Salisbury) for his encouragement, and Miss G. E. Fairbairn (St Thomas’s Hospital) for the histological preparations.

This research was supported by a grant from the Medical Research Council.

A field survey conducted amongst children in a semi-rural area of Ceylon has revealed a high rate of Schick negative conversion early in life. A high carrier rate of C. diphtheriae in cutaneous ulcers which probably accounts for this early Schick conversion has been detected. The role of cutaneous diphtheria and that of non-toxigenic organisms in the acquisition of natural immunity to the disease is discussed.

Colony counts on mice given the same number of Salmonella always differ considerably. However, the standard error of the mean log count does not increase after the first 1·5 hr. of infection until the 8th or 10th day. These infections therefore appear to pass through an initial stage lasting a few hours, in which a varying proportion of the inoculum is killed, followed by a prolonged second stage in which the scatter in individual colony counts remains constant.

An investigation was carried out into the bacteriological performance of three air-conditioning plants in a hospital ward. Two of these plants had the facility for recirculating part of the ward air.

An equation has been derived comparing the concentration of bacteria which would be expected to be given off by the humidifiers in the ventilation system, with the concentration of bacteria in the recirculatory tank. The bacterial particles given off by these humidifiers were of nuclei droplet size, and were found to penetrate the filters used with a fair degree of ease. Although the number of bacteria in the humidifier water remained insignificant with a constant overflow of water into the recirculatory tank, on one occasion a build-up of bacteria was demonstrated when the overflow ceased. For hospital use humidifiers of a non-recirculatory type should be used.

The concentration of bacteria on the surface of the recirculatory ducts was assessed, as also were those on the surface of the supply ducts under full fresh air and recirculation. The concentration of bacteria in the supply ducts was low and the use of terminal filters was not merited, although care should be taken to prevent the build-up of bacteria in inlet grills and diffusers. The bacterial concentration in the exhaust ducts was found to be quite high. It was therefore thought that in critical areas, where the ventilation plant may be shut off, the use of some device to prevent reversed air flow may be necessary.

The count of various types of micro-organisms in the fresh air and two-thirds recirculated air are given along with their size distribution. The results of the effect of filtration on the concentration of bacterial particles throughout the air-conditioning plant is given under full fresh air and recirculation. These concentrations appear quite satisfactory. It was found that one set of filters had been overgrown by mould because of free water being brought over from the humidifier. Measures have been suggested to overcome this. When primary or prefinal filtration was approximately 90% efficient to Aloxite 50 (B.S. 2831 Test Dust no. 2) it was demonstrated that a fair approximation to the final filtration figure could be obtained by reference to the quoted efficiency of the final filter to Aloxite 50. After similar primary filtration it was demonstrated that the final filtration of filters against recirculated and fresh air was approximately the same. Owing to the higher number of Staph. aureus in recirculated air, higher efficiency filtration may be required.

Standards of filtration efficiency for critical and non-critical zones are suggested.

A material (LS) analogous to that described by Craigie & Wishart (1936a) has been detected in extracts of vaccinia-infected rabbit dermis. Gel-diffusion tests on this material support the view that it is a single substance possessing two distinct serologically reactive sites. The tests also show that under some conditions rabbit LS may give two lines of precipitation against suitable antisera and that this is not due usually to the dissociation of LS into discrete L and S substances.

A study of vaccinia-infected sheep dermis failed to give evidence of a single LS substance. Instead two chemically different substances were isolated, one having the serological specificity of L, the other that of S. The physical, chemical and quantitative serological properties of sheep S were such that it could not have arisen by degradation of an LS material similar to that found in vaccinia-infected rabbit dermis. On this evidence it is suggested that vaccinia virus is not necessarily synthesized in the same way in different host tissues.

Four cows were inoculated via the udder with the 1836 strain of Mycoplasma bovigenitalium. The serological response was investigated using the complement-fixation and serum plate agglutination tests. A heterologous response to M. mycoides was observed, associated with an increase in the anti-γ-globulin titres in the cow's serum. The heterologous response persisted in one cow for 6 weeks after infection. The nature of the immunoglobulin response was characterized by density gradient centrifugation, and by mercaptoethanol and rivanol treatment of the serum and was found to consist entirely of 19 S γ-globulins.

The Mycoplasma persisted in the udder for the 18 weeks duration of the experiment. The Mycoplasma was not isolated from the blood. One of the cows became lame with swollen joints; Bacillus cereus was isolated from the joints and blood.

A commercial swine fattening ration containing animal origin ingredients was shown to be related to the salmonella excretion of market pigs being sent to slaughter from a well-managed farm. When similar animals from this farm were fed a ration of much lower salmonella content, due to exclusion of ingredients of animal origin, their excretion declined as measured by both rectal and caecal swabs. When subsequent lots of pigs consumed a pelleted weaner ration and the special supplement only, before being exposed to a supplement containing the usual level of contamination, they seemed to be refractory to infection. Probably, this was a function of age at first exposure.

With prospective methods it was possible to show that salmonellas from the abattoir environment could infect pigs, that they would excrete them within a very short time, and that organisms from this source could be demonstrated at slaughter and shown to be a cause of carcass contamination.

While these findings support the view that the build-up of salmonellas hi pigs is by contact with a contaminated environment, they indicate that the primary source of the contamination is most probably the salmonella-excreting pig which has consumed contaminated feed ingredients on its farm of origin.

If the great majority of pigs went to slaughter salmonella-free they would not serve as a source of infection to other pigs being sent to slaughter. Their intestinal contents could not contaminate carcass sides in the slaughtering process. This should help to prevent the contamination with salmonellas of the food preparation area of both homes and commercial eating establishments.

Rabbits were immunized by multiple intradermal injections followed by six intravenous doses of vaccinia virus inactivated by heating to 65° C. Particular attention was paid to confirming that the virus used was fully inactivated and incapable of reactivation. The immunized rabbits developed neutralizing and other antibodies to a titre comparable with those developed in response to live virus, but multiple intravenous injections were required to elicit a maximum titre. A qualitatively different response was seen only in immunodiffusion tests in agar gel where two or three fewer lines developed with antisera to heated virus than with those to live virus. The rabbits were subsequently challenged intradermally either with vaccinia and cowpox or with rabbitpox. They showed some immunity to vaccinia and cowpox, compared with normal controls, but less than that elicited by live virus. Their resistance to lethal doses of rabbitpox was life-saving though some rabbits did develop lesions. Later rechallenge of the rabbits showed that they had not developed further immunity, in distinction from the normal controls. The implications of these findings are discussed.

I wish to thank the National Fund for Research into Poliomyelitis and Other Crippling Diseases for their generous support in providing a Research Fellowship during which this work was done. I wish to thank also Professor A. W. Downie F.R.S. and the Staff of the Department of Bacteriology, University of Liverpool, for their encouragement and assistance respectively.