A modification of the growth-inhibition test for identifying Mycoplasma species is described. The modification simplifies the screening of a large number of strains for one species. Experiments showed that it was effective and specific when used to identify M. mycoides var. mycoides. Its use in studying the epidemiology of contagious bovine pleuropneumonia is discussed.

This work was financed in part by the United States of America Agency for International Development under the terms of the CCTA/AID Joint Project 16 for research on contagious bovine pleuropneumonia.

We wish to thank Dr R. H. Leach for the various bovine mycoplasma cultures.

Two hundred and twenty-two infants and fifty-one staff were examined for carriage of Staphylococcus pyogenes and Gram-negative bacilli, and the presence of these bacteria in the ward environment was also investigated. Staphylococci were phage-typed and tested for sensitivity to antibiotics. Assessment of clinical infection caused by these bacteria was made.

Infant carriage of Staphylococcus pyogenes was maximal on the sixth day, 73·1 % of umbilical swabs yielding significant growth. Carriage of Gram-negative bacilli was maximal on the fifth day, 31·7% of umbilical swabs being positive. Where special nursing was enforced, i.e. premature baby unit, isolation of Gram-negative bacilli was very infrequent.

The low nasal carriage of staphylococci seen in infants and nursing staff is attributed to traces of penicillinase-resistant penicillins in the ward air.

Staphylococcus pyogenes was recovered from 23 % of ward surfaces, and constituted 0·7% of the air-borne flora. In contrast, Gram-negative bacilli were recovered from 4·7 % of surfaces, and composed only 0·15% of the air-borne flora.

Phage group I constituted 73·0, 44·9 and 41·2% of strains from infants, staff and ward environment respectively.

Antibiograms were grouped into three categories, A, B and C. Category A (sensitive to chloramphenicol, erythromycin and methicillin but penicillin-resistant) composed 79·0% of infants' strains, being found mostly in group I, but was rare among staff strains.

Of 54 specimens taken from 40 infants showing evidence of infection, Staphylococcus pyogenes was isolated from 16, of which 14 were category A. Gram-negative bacilli were isolated 7 times. Only 21 infants required antibiotic therapy (9·3%) and none were infected with Gram-negative bacilli—this contrasts with the frequency of these bacilli in nursery infection today.

Ward air is considered to be the main depot of Staphylococcus pyogenes. Infant ‘dispersers’ are probably the principal source of the air-borne staphylococci. Infants and staff abstract from the air those staphylococci which become their colonizing strains. No transfer is thought to occur from the staff to the infants. Transmission of Gram-negative bacilli is similar in that the infants are the principal source and the air the main depot of these bacteria. Nasal colonization by Gram-negative bacilli is low, this is possibly due to poor colonizing properties. Infant umbilical carriage almost certainly results from endogenous faecal spread.

We are grateful to Dr J. C. Gould, Director, Central Microbiological Laboratories, Edinburgh, for his continued interest and advice, and to Mr J. C. Ferguson and Mrs M. M. Winton for skilled technical assistance. This study would not have been completed without the co-operation of Sisters McCartney and Struthers and their nursing staff.

1. When mice are infected intraperitoneally with Langat virus only a small proportion develop clinical encephalitis, but all mice have substantial titres of virus in the brain and also incontrovertible histological evidence of encephalitis.

2. When specific antibody is given intraperitoneally or intravenously to mice during the first 3 days after intraperitoneal infection with Langat virus, the viraemia (normally maximal during this period) is depressed, the production of antibody is depressed or delayed, and the incidence of clinical encephalomyelitis is increased significantly.

3. Specific antibody given intraperitoneally or intracerebrally before infection, protects the animals from encephalitis.

4. These findings are discussed in terms of the histology of the central nervous system of the affected mice.

We are very grateful to Miss S. J. Illavia, B.Sc., and to Miss G. E. Fairbairn for their skilled technical assistance; and to Mr S. Peto of the Microbiological Research Establishment for statistical advice.

This work was made possible by a generous grant from the Wellcome Trust and the Endowment Funds of St Thomas's Hospital

1. Irradiation in a whole body dose of 200 rads or more increased the sensitivity of mice to intraperitoneal infection with Langat virus so that the LD 50 was increased to about the intracerebral LD 50.

2. In mice given 500 rads before infection: (a) viraemia was prolonged by about 5 days; (b) the IgM response was depressed; (c) the IgG response was delayed by about 3 days and depressed in titre; (d) virus concentration in the brain rose continuously until death on about the tenth day while in the controls it reached a peak on the fifth day then subsided; (e) histological changes in the CNS were delayed and minimal even at death; (f) irradiated mice died with little evidence of paralysis while the controls died with severe paralysis.

3. In irradiated mice, protection was observed when antibody was administered on the third day following infection. Antibody given on the 3 days after infection to control mice aggravated the disease.

4. The results in this and the preceding paper are discussed in relation to the pathogenesis of encephalitis. It is concluded that neuronal damage is caused both by virus multiplication in neurones and by damage superimposed by inflammatory changes with associated oedema and hypoxia. The inflammatory changes appear to be due to an allergic reaction to virus-antibody complexes formed in the circulation and in the central nervous system.

We are grateful to Miss S. J. Illavia, B.Sc., and Miss G. E. Fairbairn for their skilled technical assistance; to the Department of Radiotherapy at St Thomas's Hospital for providing time and staff to help with the irradiation experiments; and to Mr S. Peto of the Microbiological Research Establishment for statistical advice.

This work was made possible by a generous grant from the Wellcome Trust and the Endowment Funds of St Thomas's Hospital.

1. From the Municipal abattoir, specimens of liver, spleen, lymph node, surface meat, bile and faeces from a sheep and a bovine, were examined fortnightly for 14 months for the presence of possible pathogenic bacteria. The results suggest that slaughtering procedures are satisfactory.

2. Offal, consisting mainly of tripe and intestine, is eaten in large quantities by the Bantu population and is both nutritious and economical. The high incidence of salmonella isolations in the tripe (48%) and intestines (29%), and faecal E. coli and Cl. welchii, show that this commodity is distributed in an inadequately cleansed condition.

3. Faecal E. coli was isolated from 86% of samples of sour milk collected from street pedlars.

4. Dog faeces collected from the township pavements yielded 21% salmonellas, and faeces from fowls sold live by shopkeepers 14%.

5. From the offal specimens, S. typhimurium (23%) and S. london (18%) were the salmonella types most frequently isolated. S. dublin was isolated on only one occasion.

6. Throughout the survey no shigellas were isolated.

7. The significance of the Cl. welchii, coagulase positive Staphylococcus aureus and B. cereus isolations from the various specimens tested is not known.

8. It is emphasized that although there is a definite need for improved treatment of the offal before distribution to the consumer, the resulting increase in cost must not be such as to deprive the population of this important source of protein.

We wish to thank the Director of this Institute, Professor J. H. S. Gear, for permission to publish this paper, Dr P. J. Meara, Director of the City of Johannesburg Abattoir and Livestock Market Department for facilities granted, and Mr C. J. Franklin for collecting all the abattoir specimens. Our thanks are also due to Dr A. Smith, Medical Officer of Health, and Dr I. H. F. Spencer of the Johannesburg City Health Department for help and advice; to Mr A. J. MacG. Bryce for collecting all the specimens from the Soweto township; to Mrs Leonie Jonk for typing the salmonella organisms and Mr R. G. Robinson for investigating the micro-organisms' sensitivity to antibiotics.

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.

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.

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 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.

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.

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.

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.

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 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.

A method is described for the testing of strains of Sh. sonnei for antibiotic resistance, colicine type and drug resistance transfer using a multiple inoculator.

The examination of 731 strains of Sh. sonnei isolated from convalescent cases and their family contacts showed that about 5% of individuals were excreting organisms which differed from the infecting strain by a single transferable antibiotic resistance determinant. It is suggested that the acquisition of such resistance may occur in 13% of family incidents.