Six strains of Str. pyogenes and four strains of Staph. aureus were found to grow well from large or small inocula in fresh human serum; four strains of E. coli failed to grow from large inocula and were killed when the inocula were small. Ps. pyocyanea, Proteus and Str. viridans sometimes grew and sometimes failed to grow in fresh serum.

In serum which had been treated with trypsin or heated at 56° C. for 1 hr. the Gram-negative bacilli grew readily, and growth was still better in serum which had been heated and then trypsinized. Heating at 56° C. and treatment with proteolytic enzymes were shown to destroy complement and to inactivate the bactericidal activity of fresh serum against a Shigella highly sensitive to the properdin system. It is suggested that these changes might be enough to explain the conversion of serum by proteolytic enzymes into a suitable medium for the growth of coliform bacilli. This change might be brought about by bacterial or leucocytic enzymes. Fibrinolytic serum from a cadaver was found to retain at least a part of its complement and bactericidal activity.

Strains of E. coli, Ps. pyocyanea, Proteus, Staph. aureus and Str. pyogenes were tested for growth in burn slough suspension and blister fluid. In slough suspension all strains grew well, but the Gram-negative bacilli grew rather more vigorously than the Gram-positive cocci. In blister fluid E. coli was killed and other strains grew.

These findings are discussed in relation to wound sepsis.

An easily prepared and readily reproducible culture medium for general use is described. A wide range of standard media can be prepared from it by simple modifications.

We should like to thank Mr P. D. Laverack and Mr D. Garwes for their exellent technical assistance, and Marmite Ltd. for much useful information about their product.

The physical behaviour of aerosols atomized into stirred settling chambers, or into rotating drums, was examined by a radioactive tracer method and by a light scatter method. With suitable corrections, there was no difference between the two methods of measuring of physical decay. The tracer method is advantageous in that the data so obtained are on an absolute basis, whereas data from scattered light measurements are relative. The latter method, however, is less time consuming, provides an immediate notification of instrument performance and does not require that material be removed from the aerosol chamber for sampling purposes.

1. The course of events following the feeding of salmonella-free pigs on food naturally contaminated with salmonellae has been followed. The pigs were killed at varying times after the commencement of the experiment and their organs examined for salmonellae.

2. None of the pigs showed any signs of ill-health and no pathological lesions were observed in them when they were killed. Salmonellae were found, however, in very small numbers in the mesenteric lymph nodes of some of them but not in any of their other internal organs or in their muscular tissue. The longer the pigs were fed on the contaminated food the more likely were their mesenteric lymph nodes to be infected.

3. Salmonellae were isolated from time to time from the faeces of the pigs but there was no suggestion of any of the pigs becoming permanent faecal excreters of these organisms.

4. Six pigs were retained for a short time after the use of the contaminated food was discontinued. Salmonellae were never found in their faeces and when they were killed the mesenteric lymph nodes of only one of them was found to be infected.

5. The results are discussed from the agricultural and public health viewpoints.

Suspensions and dried preparations of vaccinia virus were exposed to γ-rays in cobalt-60 sources. Suspensions completely inactivated by 6–8 × 105 rad. retained measurable immunogenicity. Dried preparations could not be completely in-activated even by doses of 11 × 106 rad., although the inactivation apparently followed first-order kinetics until about one particle in 107 survived, suggesting that the populations of vaccinia virus in the preparations were heterogeneous.

The potency in man of eight different commercial vaccines and an experimental vaccine, as judged by the antibody response after the primary course of two injections and after a booster dose 9–12 months later, was compared. All the vaccines produced good responses to Types 2 and 3 but some were less satisfactory for Type 1. The relation of potency to protection in man is discussed and the use of one of the vaccines as a minimum standard for this country is suggested.

Single and multi-jet liquid impingers and membrane-filters were found to be efficient sampling devices for aerosols generated from suspensions of the virus of foot-and-mouth disease (FMD). Concentration of the aerosol samples with an adsorbent, Attaclay, facilitated the detection of small amounts of virus. Sodium dodecyl sulphate could be used for elution as the virus of FMD is resistant to this anionic detergent.

The penetration of these aerosols through various air filtration media was determined using impinger samplers. A glass fibre paper was found to be the most efficient with a virus penetration of less than 0·001%.

We wish to thank Dr D. W. Henderson and Dr H. M. Darlow, of M.R.E. and Mr R. G. Dorman of C.D.E. Porton for valuable prefatory discussions and advice. We are also indebted to Miss S. Cartwright for inoculating mice, to Miss M. Shoobridge and Mr S. Taylor for technical assistance, and to Vokes Ltd. for supplying materials.

It was shown in this work that the electrophoretic mobility of the MEF1 strain of poliovirus was increased approximately 25% after interrupted inactivation with formaldehyde. This is in accordance with past observations on the behaviour of formaldehyde-treated proteins. The residual live virus had the same mobility as the ‘killed’ virus, thus indicating that the surfaces of all the virus particles have been affected to the same degree by the inactivating agent.

Gel precipitin tests performed on the different samples obtained by zone electro-phoresis showed, in addition to the main antigen, the presence of a small amount of a second component of slightly higher mobility, and, as it occurs in the main fraction and the sample thereafter it probably has a slightly higher mobility than the main component.

The antigenic properties of the different fractions as shown by the production of antibodies in guinea-pigs correspond with the presence of precipitating antigen in the samples in the region of highest antigen concentration. The faint antigenicities of the fractions obtained from the regions higher up in the zone electrophoresis column are due to small amounts of virus antigen similar to that found in the column on electrophoresis of untreated MEF1 virus, bearing in mind that the inactivated virus was concentrated approximately 2000 times for zone electrophoresis.

1. Pathogenic bacteria are removed from air by relatively simple filters having an efficiency of 99·9% for 5-μ particles.

2. To prevent ingress of contaminated air from other parts of the hospital an operating-room should be pressurized by a flow of filtered air. An input flow of 1200 cu. ft. (34 cu. m.) per min. will ensure this if mechanical exhaust fans are replaced by pressure-relief valves.

3. Other rooms of the suite should be ventilated in this way with flow rates depending on door area, and with pressure gradients adjusted by relief-valve loadings to cause air flow from dirtier to cleaner zones.

4. All openings between the rooms of an operating-suite should be fitted with doors to prevent airborne cross-contamination and high-level loss of ventilating air.

5. The relative merits of turbulent and downward-displacement ventilation have been studied and are discussed. The choice between them depends on the sites from which pathogenic bacteria are mainly disseminated during operations; these are not yet fully understood but the available evidence favours the displacement system. Methods for producing turbulent and displacement ventilation are described.

6. Discomfort from overheating of operating-rooms is largely due to faulty design and siting of sterilizing equipment. In Britain, if these faults are avoided, ventilation without cooling equipment can give comfortable conditions except on very rare occasions.

Measurements to assess the performance of the ventilating system have been carried out in a series of twenty six operating theatres using nitrous oxide as a gaseous tracer to simulate the movement of airborne bacterial contamination. In order to prevent local clouds of contamination derived from the activities of the operating-team persisting in the neighbourhood of the operating-site it is desirable that there should be appreciable air movement in the centre of the room. Downward displacement, ‘piston type’, ventilation systems may be an exception to this but the indications for their use are not clear. Other points discussed include the necessity for the limitation of the volume of mechanical exhaust if adequate positive pressure is to be maintained in the theatre and the need to control heat dissipation from sterilizers, autoclaves and other sources.

Threads were infected with the spores of four species of bacteria and put inside rubber gloves which were sealed into plastic bags and irradiated with electrons or gamma rays. A dose of 1·5 Mrad. killed approximately 99·99% of the spores of each species and a dose of 2·5 Mrad. appeared to give an adequate margin of safety for sterilization. Spores were similarly killed inside plastic tubing and within the lumen of hypodermic needles.

The tensile strength of the gloves decreased with increasing doses of radiation so that the rough, solution-dipped gloves tested were significantly weaker after 8·0 Mrad., but the smooth gloves tested still complied with the British Standard after 30 Mrad. When vacuum-packed before irradiation, rough gloves were still satisfactory after 16 Mrad., and smooth gloves were apparently unaffected by 30 Mrad.; they could, therefore, be sterilized six and twelve times, respectively.

Radiation gives dependable sterilization of rubber gloves, and the use of a sealed plastic package obviates subsequent contamination. The possibility of using disposable radiation-sterilized gloves is discussed, the use of a plastic radiation indicator suggested and the practical applications of radiation sterilization in the hospital considered.

1. It has been shown that cows infected with brucellosis of the udder can usually be detected by an application of a modified milk ring test, based on the finding that milks from infected cows, in addition to showing a high bulk MRT titre also show considerable quarter variations. The effects of adult vaccination with strain 19 vaccine on the MRT are reported; low bulk titres with uniformity between quarters, except at the beginning and end of lactation and immediately following vaccinations, were observed, thus making differentiation between vaccinated and infected cows possible.

2. In a survey of raw milk samples from three areas in southern Scotland, 3·5, 5·3 and 9·0% of samples were shown to be infected with Br. abortus.

During the 8½ years, February 1951 to July 1959, 672 strains of myxoma virus were recovered from the field in Australia, all but thirteen, which were derived from mosquito pools, being extracted from the tissues of infected wild rabbits. These were tested for virulence by the intradermal inoculation of small groups of rabbits with a small dose of virus. Based primarily on survival times, strains have been allocated to five grades of virulence, ranging from very high to very low. In spite of inadequate sampling during the first 5 years there has clearly been a trend from a predominance of highly virulent strains in the initial epizootics to a mixture of strains of virulence varying from very high (rarely) to very low. For the last 6 years the proportion of strains allotted to the different virulence grades has remained almost constant, just over half the strains tested each year being classified as moderately virulent.