The characteristics of Gram-negative organisms and some of the underlying reasons for their adjuvant action with diphtheria toxoid are described.

The adjuvant effect was shown by an earlier production of antitoxin, with a maintained differential advantage over controls, but with the usual decline in titre with passage of time. The adjuvant effect only occurred with a primary stimulus. There was no adsorption between toxoid and vaccine and mixture of the two was not necessary, but the vaccine had to be given simultaneously with or within 24 hr. following injection of the toxoid. There was evidence for believing that these adjuvants decreased the minimal stimulating dose of antigen and caused hyperplasia of antibody-producing cells. No direct link could be found between the characteristic stress symptoms caused by lipopolysaccharides and their ability to enhance antibody formation.

The growth curves of young mice experimentally infected with L. australis A, L. australis B, L. grippotyphosa or L. icterohaemorrhagiae fell into two types, a ‘lethal’ pattern of continued weight loss until death, or a ‘carrier’ pattern of retardation of weight gain. The ‘carrier’ pattern could be changed to the ‘lethal’ by increasing the size of the infecting dose of a given serotype, or vice versa. Infection with L. icterohaemorrhagiae in newborn mice was fatal, while adults became carriers; susceptibility to infection with L. australis B decreased with increasing age.

The numbers of infecting leptospirae and the age of the mouse determined the outcome of infection with a given serotype in a standard test animal. The basis of species susceptibility is unknown, but it is suggested that variation in the ability to produce lesions is the basis of the differences in virulence between serotypes. The ‘host of election’ in leptospirosis is regarded as the result of a quantitative rather than qualitative adaptation of host and parasite to one another.

The growth of L. australis B in the kidneys of young mice which become carriers was followed after experimental intraperitoneal infection. There was a primary growth corresponding to generalized acute infection and terminated at the time of appearance of antibody. A secondary growth bf leptospirae followed in the kidneys alone about 7–10 days after infection, coinciding with the onset of leptospiruria and recovery from infection. Subsequently mice carried about 106–107 leptospirae in their kidneys permanently.

The leptospirae in the urine or in the kidneys of carriers were resistant to the action of antibody in the serum or urine of the host animal, or in rabbit antisera prepared against mouse-renal leptospirae or against cultured leptospirae of the infecting strain. No antigenic differences were detected between renal and cultured leptospirae. An analogous situation is the growth in vitro of leptospirae in homologous antiserum. The mechanism permitting growth of leptospirae in homologous antiserum in vivo or in vitro is unknown.

The carrier condition results from the ability of virulent leptospirae to (i) grow in the host and produce lesions in the primary, acute generalized infection, (ii) grow in renal tubules in the presence of antibody.

Fluorescent antibody techniques were used for detection of plague antigens in infected mouse carcasses stored at 4°–5° C., 20°–25° C. (room temperature) and 370° C. for periods as long as 340 days in certain cases. Tissues of two guinea-pigs infected with Pasteurella pestis were examined after 7 years storage at room temperature. The efficacy of the fluorescent antibody test was compared with blood agar plate culture and animal inoculation during periods in which viable plague bacilli were presumed to be present, and compared with Larson's modified Ascoli test for the presence of soluble plague antigens during periods in which plague bacteria were presumed to be non-viable.

Fluorescent antibody tests were superior to animal inoculation or cultural methods in detection of P. pestis antigens in mouse carcasses stored for 4 days or longer at 37° C., for 8 days or longer at 20°–25° C. (room temperature), and for 34 days or longer at 4°–5° C. Upon examination of specimens presumed to lack viable plague organisms the fluorescent antibody test and precipitin tests were approximately equal in efficiency for detection of plague antigens in carcasses stored for 16–82 days at 37° C. and for 16–82 days at 20°–25° C. Ten of 21 mice stored for longer periods (140 and 340 days) at 4°–5° C. were negative by precipitin tests, whereas 19 of the same 21 rodents were positive by fluorescent antibody tests. In addition, after 7 years storage at room temperature tissues of two plague-infected guinea-pigs were negative by Larson's modified Ascoli test but positive by the fluorescent antibody test.

1. The nasal carriage of Staph. aureus and its relation to disease was studied in new recruits, boy apprentices and trained men of the Royal Air Force.

2. The proportions of Staph. aureus that were penicillin-resistant ranged from 15% in new recruits to 29% in trained men. In a school for apprentices the rate in new arrivals was 18%, and 23% for boys after the initial training. We were unable to find when these changes occurred.

3. 31% of strains isolated from septic lesions were penicillin-resistant and the rate was similar in all types of unit. Resistant strains were not apparently more virulent than sensitive strains.

4. About 1% of all strains isolated were resistant to tetracycline and streptomycin and much smaller proportions to chloramphenicol and erythromycin.

5. The phage-group distribution was similar for nasal and lesion strains, but nearly half the penicillin-resistant lesion strains belonged to Group I, and types 52A and 3C/55/71 were much commoner in lesions than in the nose.

6. Penicillin-resistant strains were more readily acquired and more rapidly lost than the sensitive strains.

7. Nasal carriers suffered from septic lesions more frequently than non-carriers, and those with a lesion tended to suffer further lesions. There was no evidence of cross-infection among bedroom contacts.

8. The proportion of penicillin-resistant strains rose from 30 to 40% between admission to and discharge from service hospitals. Resistant strains were not carried for long after discharge.

9. Penicillin treatment resulted in a fall in the total carrier rate and a rise in the resistance rate. Phage type analysis showed that this was mainly due to elimination of sensitive strains and recolonization with resistant strains.

We are greatly indebted to Miss Susan Green for the large amount of work that she did in the laboratory. We should like to thank also many Royal Air Force medical officers for their assistance, in particular Wing Commander E. S. Odbert, Wing Commander M. White, Squadron Leader M. Shearer and Flight Lieutenant A. J. Zuckerman; and the Director-General of the Royal Air Force Medical Services for permission to publish the results.

In 1956–58 septic lesions in men of the R.A.F. accounted for about 3% of all admissions to sick-quarters or hospital and about 5% of admissions excluding respiratory disease; 1% of all men in the service were admitted with sepsis each year. Incidence fell with age, particularly up to the age of 25 years. The rates for women were about 50% higher.

Recruits experienced more than twice as much sepsis as trained men and boy apprentices. Officers had only half the admission rate of other ranks. These contrasts could have been explained by differences in age. There was no evidence of seasonal variation in the incidence of sepsis, but in recruits and boy apprentices epidemics of sepsis unrelated to season occurred.

I am indebted to Dr J. C. McDonald and Professor R. E. O. Williams for helpful criticism, to Professor P. Armitage for statistical advice and to the Director-General, Royal Air Force Medical Services, for permission to publish the results.

Detailed instructions are given for the preparation of a purified and stabilized suspension of vaccinia elementary bodies. This is intended to take the place of crude glycerinated calf or sheep lymph vaccine. The technique consists of a series of procedures involving mechanical disintegration of the skin pulp, maintenance of dispersion by means of a non-ionic detergent, fractional centrifugation and bacterial disinfection. Stability of the purified virus is secured by suspending it in a dilute buffer containing peptone and polyvinylpyrrolidone. Experiments are described which illustrate the remarkable heat resistance of the virus in this suspending medium. The PVP-peptone also serves as an excellent menstruum for lyophilization. Production of this vaccine should be well within the competence of any properly equipped virus laboratory. Clinical trials are in progress.

All the work involved in the performance of the tissue culture assays was carried out by my former assistant Mr Edmund Bischoff. It is a pleasure to acknowledge both his technical skill and his enthusiasm. Mr T. C. Campbell provided the crude calf pulp used in the preparation of some of the purified suspensions.

Minimal quantities of active vaccinia virus in the form of a purified elementary body suspension were injected subcutaneously into rabbits. The amount administered was about 10 minimal infective doses as measured by intracutaneous titration and tissue culture assay: this is equivalent to about 1·3± 10−5μg of virus protein. The immune response to this minimal quantity of virus was determined by complement-fixation and virus neutralization tests and also by skin sensitivity tests. The results indicated that viral proliferation occurred to an extent sufficient to sensitize the tissues to the virus protein. Measurable amounts of antibody could also be detected in about one half of the experimental animals. A second inoculation of virus produced a considerable augmentation of the immune response. Viral proliferation must have taken place in order to evoke this immunity, but infection always remained at the subclinical level. The results were much improved when the infecting does of virus was incorporated in an adjuvant. DPT-polio vaccine functioned well as adjuvant but equally good results were obtained with a solution of polyvinylpyrrolidone. The latter substance also has valuable properties as a protective colloid and is thus able to maintain the viability of the virus over long periods of time.

On the evidence provided by these experiments it is suggested that an adequate immunity to smallpox might be achieved in man by similar methods. A primary sensitization could be achieved by incorporating a very small amount of active virus in one of the prophylactics given as a routine in the early months of life. This could be followed by normal jennerian vaccination a few months later; or the second inoculation of virus could also be incorporated in amultivalent prophylactic. For adults, a somewhat similar two-stage immunization would be required.

It is hoped that the publication of these preliminary experiments will encourage other investigators to continue what promises to be an important line of research.

All assays involving the use of monkey kidney tissue cultures were carried out by my former assistant Mr Edmund Bischoff. His help is gratefully acknowledged.

1. Salmonella heidelberg infection in humans was traced to one cow excreting the organism in milk.

2. The cow was clinically normal and infection was confined to the right hind-quarter of the udder.

3. The affected quarter had numerous haemorrhagic foci but there was no inflammatory response to the infection.

4. Histological preparations suggested that Streptococcus uberis was causing a chronic mastitis in all four quarters.

The usefulness of the meningococcal CF test was assessed by investigating sera from (a) patients with meningococcal meningitis from whom meningococci had been isolated, and (b) patients with aseptic meningitis in whom no virus aetiology had been demonstrated and from whose C.S.F. no bacteria had been isolated.

Meningococcal CF antibodies were relatively strain-specific; cross-reacting anti-bodies to heterologous strains were irregular both qualitatively and quantitatively.

Positive meningococcal CF tests were obtained in 8 cases of aseptic meningitis, 3 showing a predominance of lymphocytes and 5 a predominance of polymorpho-nuclears in C.S.F. As a result of these positive tests, the cases of lymphocytic aseptic meningitis were given energetic antibiotic therapy to avoid the possibility of more chronic infection.

We wish to thank many clinical and bacteriological colleagues for their co-operation, and Prof. S. Graham for details of one case. We are grateful to Dr Patricia Bradstreet, Standards Laboratory for Serological Reagents, London, N.W. 9, for meningococcal agglutination results, and to Miss C. Gourlay for valuable technical assistance.

Long-chain fatty acids are not appreciably bactericidal to tubercle bacilli at neutral pH, but become so even in slightly acid solution. In this way tubercle bacilli, normally resistant to 0·1 N hydrochloric acid (pH 1·0), are rapidly killed at this pH if traces of fatty acid are present, such as can be found inside test tubes that have been plugged with cotton wool and sterilized by dry heat.

The lethal effect is largely prevented by non-ionic, cationic, and to a lesser extent anionic detergents, which probably take up the fatty acid into the micelles so that it can no longer attack the bacilli.

The various fatty acids identified in the deposit from heated cotton wool were tested individually and found to be bactericidal. They comprised the usual C12 to C18 saturated acids and also oleic acid. The latter, however, showed no particular lethal toxicity in excess of that shown by, for example, palmitic acid. Shorter chained fatty acids than those represented in the deposit were less lethal.

We wish to thank Dr A. T. James for the chromatographic analyses and for advice; Dr R. J. W. Rees for carrying out counts of total acid-fast bacilli in two experiments; Messrs. Robinson & Sons Ltd, Chesterfield, for information on the industrial processes involved in the preparation of cotton wool; Mr E. J. Latham for advice on preparing glassware; and Dr J. Marks for helpful criticism of the manuscript.