Haemagglutination-inhibiting antibodies against A, A′ and A2 strains of influenza virus and against one strain of influenza B were estimated in sera from blood donors in Sydney in February 1958 and in April and October 1961.

The A2 antibody increased substantially while both A and A′ antibodies declined slightly. There was a great decline in influenza B antibody during the same period.

Thanks are due to Dr Phyllis M. Rountree who suggested this study. Miss Patricia Taylor gave excellent technical assistance in the early part of this work.

A simple method for the isolation of pox virus hybrids on the C.A.M. has been described. One parental virus was used as a heat-inactivated suspension. The other parent was used in the active state, but at a temperature higher than its ceiling temperature. Under these conditions the inactive parent was reactivated so that pocks resulted only from the cells infected with both parental viruses. Many of these pocks were unlike those of either parent. Such lesions were found to contain a high proportion of hybrids. In these experiments, alastrim was crossed with rabbit pox and variola major with cowpox.

The term ‘heat-tethered’ has been used to describe virus whose intracellular cycle of development has been arrested by incubation at too high a temperature. Heat-tethered virus has interesting properties and two of these have been described. When the temperature is lowered, heat-tethered virus will start to grow again. Its reactivating potential has been mentioned above. A more detailed account of the properties of heat-tethered virus is being prepared.

The characters of seven clones of virus derived from mixed infections with alastrim and rabbit pox have been described. One clone was shown to behave as rabbit pox in respect of all its markers. The other six were found to be distinct new types of virus, each having a different combination of the parental characters. The reasons for accepting these viruses as hybrids have been discussed. An analysis of the pairwise crosses between individual markers suggested that each of the nine markers was capable of segregating independently.

The characterization of 16 clones of virus derived from mixed infections with variola major and cowpox has been described. This work has involved the description of the plaques produced by variola major in chick embryo monolayers, and a more detailed study of the effects of raised temperature on pock production by pox viruses on the C.A.M.

Two of the variola major—cowpox clones were found to correspond to cowpox virus, while the other 14 shared various combinations of parental characters. Among them there were 10 distinct new types of virus. Evidence of the stability of these viruses has been presented.

Analysis of the combination of characters encountered among the hybrids has given good evidence that all the eight marker characters used segregate independently. A particular instance of this was the character of chick embryo virulence which, among the hybrid viruses, was shown to be unrelated either to ceiling temperature or speed of plaque formation.

The significance of these findings in relation to the general problem of virulence has been briefly discussed. The possibility that vaccinia may have originated as a hybrid of variola and cowpox has lso been considered.

Virological and serological studies on an outbreak of aseptic meningitis in association with Coxsackie B5 virus, and Coxsackie A9 virus to a lesser extent, are reported. Coxsackie B5 virus was isolated from spinal fluids of 60 patients and Coxsackie A 9 virus from one spinal fluid. Fifty Coxsackie B 5 and 13 Coxsackie A 9 viruses were recovered from patients' faeces. The evidence that the epidemic was caused by these viruses was confirmed by determination of neutralizing antibody in paired sera.

The plaque variants of Coxsackie B5 virus isolated from the faecal specimens and the poor antibody response in Coxsackie A 9 infection were reported as points of virological and serological interest.

The residential home was investigated to study the endemic virus population. During this study, oral poliovirus vaccine was given to the children and the effect of vaccination on endemic enteroviruses and adenoviruses was investigated. In the light of these findings, the problem of virus interference is discussed. The health of the children is related to their virus infections.

We are indebted to Prof. S. D. M. Court and Prof. C. A. Green for the active interest they have taken in this investigation; to Miss J. McQuillin, B.Sc., F.I.M.L.T., for her technical assistance; also to the matron of the home and her staff for their co-operation in supplying the specimens, and to Mr L. J. Whitlock of the Royal Victoria Infirmary and his staff for arranging their transport to the laboratory.

Complement-fixation tests with psittacosis-trachoma group antigens, if set up with complement prepared from guinea-pigs cross-infected with any of the Bedsonia agents, may give completely false positive results. The use of C.F. positive or C.F. inhibition positive samples of guinea-pig sera as a source of complement can induce also a significant increase or decrease, respectively, of the actual C.F. titres in Bedsonia-positive serum samples tested. Observations made both in routine serology and in experimental studies show the necessity of testing carefully, for possible presence of Bedsonia titres, individual sera of guinea-pigs intended for use as source of complement in C.F. tests performed with Bedsonia group antigens.

I have pleasure in thanking Dr F. B. Gordon and Dr E. Weiss for the valuable suggestions made and HM3 C.O. Wiese for the technical assistance.

Group-reactive ether soluble psittacosis and boiled mouse pneumonitis antigens were tested in parallel, with 85 serum specimens. The results indicate that the group-specific C.F. antigens of these organisms are indistinguishable when tested against sera of trachoma patients, monkeys infected with trachoma or against sera of other individuals.

Sera of rabbits immunized with viable trachoma-inclusion conjunctivitis (TRIC) organisms, grown in tissue culture, were absorbed with boiled elementary body suspension of mouse pneumonitis agent, which removed the group reactive antibodies, and resulted in a species-specific anti-TRIC serum.

The absorbed and unabsorbed TRIC sera were titrated against purified E.B. suspensions, which were prepared both from yolk and from tissue culture grown organisms, of homologous TRIC strains and from other heterologous Bedsonia organisms.

Results of absorption experiments indicate that group reactive antigens prepared from mouse pneumonitis and psittacosis are indistinguishable by C.F. test from the group-specific component of the TRIC antigens. The species-specific antigen of the TRIC agents was well distinguished from the species-specific antigen of the psittacosis agent. However, the C.F. test did not distinguish the strains isolated from trachoma from those isolated from cases of inclusion conjunctivitis.

The stabilizing effect of sucrose and albumin upon the species-specific C.F. antigen of purified elementary bodies of TRIC organisms was found to be pronounced.

Our attempts to produce a species-specific antigen preparation, free from group component, failed.

We have pleasure in thanking Dr F. B. Gordon for suggestions; Dr B. V. Birtašević, Mr H. R. Dressler, Dr E. S. Murray and Dr A. J. Vargosko for procuring sera of patients or organisms grown in tissue culture; Dr T. A. Strike for the help with statistical computations; HMC P. R. Hill, HM3 C.O. Wiese and Mr B. L. Ward for invaluable technical assistance.

A complement fixation test with rabbit antisera was used to differentiate 82 cultures of Mycoplasma from man, mammalian cell cultures, laboratory rats and mice, cattle, goats, poultry, embryonated eggs and sewage.

Seventeen serotypes were distinguished, 5 from man, 1 from mammalian cell cultures, 4 from rats and mice, 4 from cattle and goats, 2 from poultry and one saprophytic. Most of these corresponded to recognized species of Mycoplasma, but 1 of human origin (represented by 1 strain, Navel), and 1 from tissue cultures (5 strains), may represent new species. R38, one of the serotypes from rats, could be distinguished from the species M. arthritidis, but is probably an antigenic variant rather than a distinct species. Two species hitherto recognized as distinct, M. arthritidis and M. hominis type 2, could not be distinguished and appear to constitute a single species. These findings illustrate the necessity, from the viewpoint of taxonomy, of comparing mycoplasma strains by serological methods.

The serotypes of human and animal origin were largely host-specific. Exceptions were the inclusion of M. arthritidis from rats and M. hominis type 2 from man in a single serotype, the finding of a bovine organism among the strains isolated from goats and of a saprophytic strain in a rat.

In relation to the aetiology of disease in man and animals, the isolation of an endogenous Mycoplasma from embryonated eggs used to passage infective material illustrates the importance of identifying these organisms serologically. The demonstration of mixed mycoplasma infections in lesions in two rats shows the necessity of adequately purifying all cultures of Mycoplasma before examination.

I would like to thank those workers mentioned in Table 1 who kindly provided the cultures which they isolated. In addition I wish to thank the following who sent cultures: Prof. A. C. Ruys and Dr D. Herderscheê (Amsterdam) for G2, Prof. H. E. Morton (Philadelphia) for Campo and 07, Dr D. G. ff. Edward (Beckenham) for Campo (PG27), M. bovigenitalium (PG11), M. iners, and M. gallinarum, Dr R. G. Wittler for H606 and Miss A. G. Newnham for A36, TU, PSU4 and TC727.

My thanks are also due to Dr L. H. Collier of this Institute, Dr G. W. Csonka (London), Prof. A. E. Macdonald (Aberdeen), Dr J. Payne (Edmonton, Alberta), Mr A. A. Tuffrey (Carshalton) and Dr D. Weisinger (Basle) who provided material from which PPLO were isolated. I gratefully acknowledge all the information so generously supplied by these workers about the strains or material provided.

I am indebted to Miss A. G. Newnham for carrying out an agglutination test on the avian strains.

Part of this work was carried out by the author under the author aegis of the Medical Research Council Working Party on Non-Specific Urethritis with the aid of a grant from the U.S. Public Health Service.

Early in 1963 neomycin-resistant Staph. aureus appeared in the burns of patients in a burns unit; after a period of 7 weeks three-quarters of the strains of Staph. aureus isolated from patients in the unit were resistant to neomycin, and after 22 weeks almost half of the patients in the burns wards were carrying the organism on their burns. When treatment with neomycin and kanamycin was stopped in the Burns Unit, neomycin-resistant strains gradually diminished in numbers and were no longer found in the ward after 6 months.

The neomycin-resistant staphylococci appeared during controlled trials of local neomycin and systemic kanamycin, and were much more frequently isolated from the burns of patients treated with these antibiotics than from patients in the control series.

During the previous 9 years local neomycin application had been used on many patients; though all staphylococci were tested for sensitivity to neomycin for a considerable part of this time, no resistant staphylococci were found.

All the neomycin-resistant staphylococci showed a pattern of inhibition by phages 6, 47, 54 and 77, and many also by phages 7, 53, 75 and 75B at 1000 R.T.D. No neomycin-sensitive staphylococci with this phage pattern were found at the time when resistant strains first appeared (though two such strains were found later); it seemed likely, therefore, that the resistant strain was introduced from outside the hospital. Preliminary tests of habituation to neomycin of sensitive strains with the phage inhibition pattern are described.

Back mutation to sensitivity was not found in tests on neomycin-resistant staphylococci.

Staph. aureus from burns of in-patients were tested for egg yolk reaction during three periods; in 1958 and in 1960 approximately 80 % of the strains gave a negative reaction (EY-), but in 1962 only 36 % of the strains were egg yolk negative.

Staphylococci of phage group III were more commonly EY- than those of other groups isolated from burns. Within each of groups I and III, however, there were patterns predominantly EY- and others predominantly egg yolk positive (EY+); in group I the majority of strains isolated in 1960 were of phage type 52 and EY-, while those isolated in 1962 were predominantly of phage type 80 or related patterns which were always EY+.

Most of the staphylococci in burns were resistant to penicillin, tetracycline and erythromycin; within groups I and III, the staphylococci which were EY- were also more commonly resistant than EY+ strains to these three antibiotics.

Most of the staphylococci from burns were mercuric chloride resistant (presumptive epidemic strains); of the mercuric chloride sensitive staphylococci, the proportion of EY+ strains was greater than that of EY- strains.

1. Extracts containing non-infective soluble antigens have been prepared from the tissues of mice infected with a pantropic or any of three neurotropic strains of Rift Valley fever virus. The antigens were detectable by complement-fixation and gel-precipitin tests using antisera prepared in mice.

2. The extracts appeared to contain at least two antigens separable by electrophoresis and distinguishable by Ouchterlony tests. The faster migrating minor antigen occurs sparsely and was not further examined.

3. No distinction, physical or immunological, was observed between the major antigen derived from the four strains.

4. In gel diffusion-filtration experiments with granulated 7 % agarose, the major antigen appeared to be polydisperse containing particles with diffusion rates ranging from at least as low as that of Burnupena cincta haemocyanin to almost as high as that of haemoglobin.

5. Centrifugal analysis indicated the presence of particles having sedimentation constants of about 8, 29 and greater than 100 Svedberg units. These particles have a density of about 1·27 g./ml. If all the particles of the major antigen are spherical, with a density of 1·27 g./ml., the three size groups have diameters of about 7–8, 14 and < 26 mμ.

6. The diffusion coefficient of the smallest particle was estimated to be 6·06x 10−7 cm.2/sec. corresponding to a sphere 7 mμ in diameter, or 4·78 x 10−7 cm.2/ corresponding to a sphere 9 mμ in diameter depending on which of two values for the diffusion coefficient of mouse γ-globulin is used in the calculation.

7. In density gradient zone electrophoresis at pH 8·6, the principal antigen migrated at about the same rate as haemoglobin and appreciably slower than the virus. The authors are indebted to Prof. A. Kipps for his continued interest in this work, and to Dr T. H. Mead for valuable criticism of this paper. This investigation was supported in part by a Public Health Service research grant Al 04044–02 from the National Institute of Health, Bethesda, U.S.A.

The pathogenesis of rinderpest virus was studied in twenty-nine grade cattle, which were infected by the intranasal route with a virulent strain of virus recently isolated in East Africa (RGK/1). These animals were killed or died at intervals of 1–16 days after infection and a number of tissues from each of them (usually 21) was titrated for virus infectivity in monolayer cultures of primary bovine kidney cells.

Temperature reactions were first detected on the 3rd to 5th days (mean 4·1), mouth lesions on the 6th to 9th and diarrhoea on the 8th or 9th days, following infection. The course of the disease was divided into four phases, viz. incubation (days 1–4), prodromal (days 5–7), mucosal (days 8–12) and early convalescence (days 13–16). Virus proliferation in different tissues was related to these clinical phases, detailed results being presented in tabular and graphical form.

No primary multiplication was detected in the nasal mucosa but virus was demonstrable within 48 hr. in its associated lymph nodes. Low-level viraemia began on the 2nd or 3rd days after infection and generalization had occurred by the end of the incubation period. The virus had established itself at this time throughout the alimentary tract and, sometimes, in the lungs.

The prodromal phase was characterized by plateaux of high virus titres in the lymphopoietic and lympho-epithelial tissues; there was a descending gradient from the cephalic nodes to the superficial lymph and haemolymph nodes of the body, to the visceral lymph nodes and spleen. There was a similar gradient in the titre of virus in the mucosae of the gastro-intestinal tract—from caecum to colon, to ileum and pylorus. Virus first appeared in the turbinate mucosa on the 5th day, post-infection and lung titres were high towards the end of this period. Some virus proliferation may have occurred in the liver, but none was certainly demonstrable in the kidney, myocardium or brain.

The mucosal phase began with continuing high titres of virus in all the major sites of proliferation, but a decline set in from the 9th day onwards. This at first involved the cephalic lymph nodes but soon extended to the spleen and other lymphopoietic tissues. It was most delayed in lympho-epithelial structures such as the tonsil, lung and gastro-intestinal mucosae. It was suggested that the decline in virus titres was due to the destruction of susceptible cells, accompanied by the local production and later circulation of antibody. Neutralizing antibody was present in the serum on and after the 9th day.

During the early convalescent period virus had disappeared from four animals, with the exception of one recovery from the lung tissue. Antibody titres were high during this time.

These results were discussed with reference to previously existing information on the distribution of rinderpest virus in infected cattle. An attempt was made to correlate them with published information on the pathogenesis of human measles and canine distemper. The data were also used to explain some previously reported observations on the excretion of rinderpest virus by experimentally infected cattle.

This study would not have been possible without the enthusiastic co-operation of Messrs C. S. Rampton, A.I.M.L.T., R. F. Staple, A.I.M.L.T., and R. Pillinger, F.I.M.L.T., in organizing and carrying out a very considerable number of laborious titrations. Dr B. Liess helped with some of the animals killed at earlier stages of the infection. Our junior African staff gave invaluable assistance with their careful and efficient handling of many thousands of tissue cultures; amongst them we should particularly like to mention Mr Francis Ngugi and Mr Harrison Agili.

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