Staphylococcal phages may be divided into three broad divisions:

(1) Phages lysing coagulase-positive staphylococci with a restricted host range. Phages in this division may be further divided into five lytic groups I, II, III, IV and Miscellaneous.

(2) ‘Polyvalent’ phages; phages with a wide host range among coagulase-positive cocci, and sometimes also active on coagulase-negative strains.

(3) Phages lysing only coagulase-negative staphylococci.

Within each division the phages can be further grouped by their serological reactions. Nine serological groups have been defined. Phages of any single serological group also share other characteristics, e.g. stability, and the ability to form lysogenic systems.

1. A new method for the preservation of bacteria by drying is described.

2. Marked differences between organisms were found with respect to the relationship between growth phase and recoveries after drying.

3. Recoveries of several strains of neisseriae and vibrios, both immediately after drying and after storage, were considerably higher than any previously recorded for similar species of these genera.

The infectivity of Brucella suis for the guinea-pig by the respiratory route has been studied. Br. Suis was dispersed in airborne particles of various sizes from single organisms to 12μ in diameter, and it was found that the infectivity decreased 600-fold with increasing particle size within this range. It is suggested that this is due to the ability of Br. Suis to multiply rapidly on the surface of the lower reaches of the respiratory tract.

Coliforms were readily obtained from many soils. In samples taken from sites exposed to animal contamination Bact. coli type I occurred predominantly. A large number of samples taken from grassy banks, only remotely exposed to contamination, were found to contain intermediates. It was found that the greater the probable degree of contamination of the soil the higher was the proportion of Bact. coli type I, and that the less the probable degree of contamination the higher was the proportion of intermediates. It is difficult to explain this merely on the basis of the prolonged survival of intermediates in soil, and it would appear obvious that the source of these intermediates lay elsewhere than in animal faeces. The numbers in which they were found in soil, however, were not of the order expected of bacteria living in their natural environment, and consequently it was equally difficult to conclude that these intermediates were actively established in soil.

The main object of the experiment which this note describes was to determine whether influenza virus could be preserved by the ‘peptone-plug’ method of drying which has recently been found to be very effective for bacteria (Annear, 1956). Two other methods of preservation were also compared in parallel with it: (a) the centrifugal freeze-drying technique (Fry & Greaves, 1951) and (b) deep-freezing.

1. The 6 hr. soluble antigen production test for comparing the infectivity of influenza virus preparations is described in detail. Dilutions of the preparations are inoculated intra-allantoically into groups of fertile eggs, and after 6 hr. of incubation the amounts of soluble antigen formed in their chorio-allantoic membranes are determined. Reproducible results can be obtained.

2. The similar test, in which haemagglutinins in the chorio-allantoic membranes are measured 6 hr. after inoculation of seed virus, is less accurate and less sensitive.

3. Eggs of different ages of incubation form different amounts of soluble antigen in their chorio-allantoic membranes in 6 hr. when inoculated with the same amounts of virus.

An interference phenomenon was produced by the intraperitoneal injection of broth culture dilutions of Pasteurella pestis grown at 28° C. into small white rats.

At a critical level of approximately 106Past. pestis L37 marked interference was produced. Doses of 104 or 107 killed rats readily.

Interference was produced by the addition of killed organisms, a cell-free vaccine or a live vaccine, to small lethal doses of L37.

Non-specific interference was produced by the intravenous injection of Indian ink prior to the intraperitoneal challenge with Past. pestis L37.

1. The clinical findings and environmental factors of 138 families infected with Microsporum canis are recorded.

2. Of the 171 children suffering from tinea capitis, 25% had lesions which remained localized, 51% had local spread of infection and 24% had a generalized spread, involving most of the scalp.

3. The clinical pattern of the infection was not associated with the sex or age of the child, nor with the source of infection.

4. In 30.5% of the families there was a definite cat source of infection, in 3.6% a definite dog source and in 13.9% a definite human source. A further 20.3% had a probable animal source, and 7.9% a probable human source, while in 23.9% no obvious source of infection could be found.

5. The social status of 95 families was investigated. In 4.2% the breadwinner was a farmer, in 12.6% he belonged to the professional and managerial group, in 60% he was a skilled labourer and in 22.1% an unskilled labourer. The houses of 75 families were visited. House conditions were classed as good in 58%, fair in 33% and poor in 9%. It is suggested that ringworm due to M. canis in New Zealand is not associated with poverty or poor conditions and no stigma should be attached to the development of an infection.

6. Evidence for the following types of transmission of infection was obtained: cat to child; dog to child; child to child; child to adult; cat to cat; child to cat; dog to cat; cat to dog.

7. The findings of the investigation are discussed. It is suggested that human infections with M. canis are part of a complicated network resulting from the commensal relationship of the cat to man. Better care of cats so that kittens are not allowed to stray would assist in the control of human infections.

Gordon & Turner (1955) reported that glucose and other sugars intensify the protective action of glycine against the heat-inactivation of complement, so that in their presence the concentration of glycine required to protect complement against inactivation at 55° C. is greatly reduced. Moreover, when high concentrations of glycine (e.g. 10%) were used, higher temperatures were required to inactivate complement if the glycine was dissolved in a high concentration of a sugar. They also showed that although this intensification is a property of a wide range of sugars, it is not shown by the corresponding alcohols, although inositol is exceptional in causing marked intensification. No explanation was offered for these findings and further experiments have been undertaken to throw light on them.

1. After inoculation of eggs with a large dose (108·6 ID50) of influenza virus, chorio-allantoic membranes harvested from the 3rd to at least the 21st hr. (but not at the 1st or 2nd hr.) gave rise to large amounts of soluble antigen in 6 hr. in the chorio-allantoic membranes of sub-inoculated eggs (6 hr. soluble antigen production test). These amounts were larger than resulted from inoculation of equivalent numbers of ID50 of standard allantoic fluid virus. By the conventional 72 hr. test, the infectivity of the chorio-allantoic membranes increased 1 hr. later, at the 4th hr. after inoculation.

2. Allantoic fluids and chorio-allantoic membranes harvested from passages of very large and of small amounts of influenza virus were tested by 6 hr. soluble antigen production. The relative amounts of soluble antigen formed by different seeds appeared to be determined by their ID50: HA ratios, irrespective of whether they were allantoic fluid or chorio-allantoic membrane preparations. Larger amounts of soluble antigen were formed in 6 hr. per ID50 inoculated by preparations having lower ID50: HA ratios, i.e. containing larger amounts of ‘incomplete’ virus, and vice versa.

3. It is suggested that high infectivity in the 6 hr. soluble antigen test per ID50 inoculated is due to a content of ‘incomplete’ virus, or of virus precursors: possibly these are in fact the same.

4. More particles of an incomplete virus preparation than of standard allantoic fluid virus must be inoculated to produce a given amount of soluble antigen in 6 hr. It is suggested that a process resembling multiplicity reactivation must occur in cells infected with more than one particle of ‘incomplete’ virus.

The biological characters of eight strains of the Newcastle disease virus, isolated in different parts of the world between 1933 and 1951, have been studied and compared in detail.

Two types of the virus have been distinguished, one from the Newcastle disease prevalent in Europe and Australia, the other from that occurring in the United States of America.

Viruses of the first type are highly virulent, multiply rapidly and successively develop the properties of infectivity, haemagglutination and haemolysis. Their haemagglutination pattern is constant and wide; they profoundly modify human group O erythrocytes, and they are antigenically homogeneous.

Viruses of the second type are of weaker virulence. They grow at a slower rate in the allantoic cavity of the chick embryo, and the development of their characters is retarded; they have a reduced haemagglutination pattern and only a minimum capacity to modify human group O cells. Antigenically strains of the second type are homogeneous.

From haemagglutination inhibition and absorption studies it is concluded that major antigens are shared by both types, and that the first type possesses one or more antigens lacking in the second.

The highly virulent Canadian TWISS strain possesses the characters of the first type and an antigenic constitution with features of both types.

The significance of the results is discussed in relation to the ecology of Newcastle disease.

Air-borne bacteria collected from occupied schoolrooms and cultivated aerobically on serum agar yielded a mean count of' general bacterial flora' (principally various micrococci) of about 70 colonies/cu.ft. with a 95% range of 19–251 colonies/cu.ft. Of a number of other occupied places examined, none except busy public offices yielded as high an average count.

When the air samples were cultivated on a medium designed to suppress micrococci, a count of 1.0–1.5 colonies of streptococci/cu.ft. was observed. About 25 % of the streptococci were levan-producing Streptococcus salivarius.

An analysis was made of factors that might affect the number of bacteria found in the classroom air. The principal findings were that Str. salivarius was correlated with the amount of talking among the room occupants and that the general count was correlated with the ventilation rate and to a less extent with talking. Both counts were correlated less strongly with the general level of activity among the occupants.

In classrooms with ultra-violet irradiation, the numbers of Str. salivarius were reduced and the correlation with talking was less than in the unirradiated rooms, being little greater than the small correlation with activity.

It was concluded that most of the Str. salivarius in the air of the schoolrooms were derived directly from the upper respiratory tract of the occupants, and these seemed to be sensitive to ultra-violet irradiation. A smaller proportion were probably dispersed from secondary reservoirs and were less sensitive to the irradiation.

Most of the organisms comprised in the general bacterial flora were probably derived from such secondary reservoirs as clothing, but some, including the enterococci, were almost certainly derived from floor dust. We are greatly indebted to Mrs Eileen Woods for her help in the computations on which this paper is based.

Titrations of the same preparations of myxoma virus have been made on the chorioallantoic membranes of developing chick embryos and by the intradermal inoculation of rabbits. Six strains of widely differing virulence for the rabbit were used.

No differences were found in the infectivity of different strains for either the rabbit or the egg, even though the severity of the symptoms produced in the rabbit varied greatly with different strains; and although some had never previously been inoculated in eggs and one had been subjected to seventy-five serial passages on the chorioallantoic membrane.

The egg was less sensitive than the rabbit, the mean number of infections per dose for rabbits relative to eggs being 2.46, taken over all strains. This ratio did not differ significantly between strains of myxoma virus.

There was evidence of some host variation in rabbit susceptibility and a great deal of variation in egg susceptibility. The maximum value for the average probability that an infectious unit would produce a lesion in the rabbit skin was about 0.6, and the maximum value for the average probability that an infectious unit would produce a pock on the chorioallantoic membrane was 0.25.

Titration of several closely spaced dilutions of different strains of the virus on the chorioallantoic membrane showed a reasonably close approximation to a proportional relationship between the pock count and the virus dilution. The change with dilution in the proportion of failures to infect rabbits approximated to expectation. Both lines of evidence are consistent with the hypothesis that a pock or skin lesion is initiated by one infective unit of virus, and that the infective unit is stable with dilution.

Sections of chorio-allantoic membranes fixed at intervals after infection with large doses of vaccinia virus showed almost homogeneous areas appearing in the cytoplasm after 4 hr.; these areas contained immature forms of virus which had a thin surface membrane and an eccentric ‘nucleoid’, and were surrounded by mitochondria. Mature forms of virus, having a larger central nucleus-like structure and a thicker cortex, were first found in areas of virus growth 10 hr. after inoculation. Similar immature and mature forms were found in cells infected with fowl-pox, myxomatosis and ectromelia viruses. It is concluded that the immature forms are of low infectivity or not infective.

An attempt has been made to assess the value of counts of bacteria in the air of occupied rooms as indices of the risks of air-borne cross-infection in these rooms. Data collected during a field trial of ultra-violet irradiation in schoolrooms have been analysed to establish the correlation between counts of Streptococcus salivarius or of the general flora and classroom secondary attack rates for measles and the incidence of four groups of respiratory affections. Variations in classroom environment and child age and behaviour were taken into account in the analysis.

The Str. salivarius count has been shown to be significantly related to the risk of classroom transfer of measles, but not to the incidence of respiratory disease. For the general flora counts the reverse was true.

A discussion of these results in the light of the effects of ultra-violet air disinfection on the incidence of presumably air-borne diseases leads to the conclusion that the Str. salivarius count may reasonably be taken as index of the risk of classroom transfer of measles, but that no such assumption is possible about the value of general flora counts in the measurement of air hygiene in relation to respiratory diseases.

Six strains of bluetongue virus were compared by cross complement-fixation tests performed on Perspex sheets according to the method of Fulton & Dumbell using antigens derived from crude saline extracts, and acetone and ether extracts, of infected suckling mouse brains. Only minor differences were encountered with the former and no significant differences with the latter. The reasons for this are discussed.

In the neutralization tests important differences were demonstrated between strains.

There is evidence that the soluble antigen is composed of particles of varying size, that the smaller particles are responsible for the marked overlapping in the complement-fixation tests, and that increasing complexity associated with increasing particle size may be concerned with increasing serological specificity.

Variation in host susceptibility results in flattening of the quantal response curve obtained in dilution counting experiments. This departure from the exponential curve obtained with uniform hosts is found primarily at the lower dilutions, where the infection rates are high. The test proposed by Moran, for the detection of host variability, may easily fail to detect quite appreciable heterogeneity with the numbers of observations that are likely to be available in practice. Examination of the response curves corresponding to various theoretical distributions of susceptibility suggests that detection of heterogeneity is unlikely unless the probability that a particle can initiate infection is distributed with a low mean and considerable positive skewness.

The problem is related to that of estimating the standard deviation of a tolerance distribution from quantal response data. This suggests an alternative test, based on the Spearman-Kärber method, which, however, appears to be no better than Moran's test. Both methods provide estimates of the variability of the susceptibility distribution.

Proof of the existence of multiplication of myxoma virus in mosquitoes has been sought by a variety of experiments with Aedes aegypti and Anopheles annulipes. All were completely negative. All features of transmission are compatible with a purely mechanical and none is compatible with a ‘biological’ mechanism.

In mechanical transmission important features of the infected animal host are the number and accessibility of viruliferous skin lesions, and the location and concentration of virus in these lesions.

By inducing mosquitoes to probe through infectious skin lesions and subsequently permitting them to make many successive probes on marked skin sites on the backs of susceptible rabbits, it has been possible to obtain quantitative information on the median minimum virus load of probing mosquitoes, and the rates of loss due to probing and the passage of time.

A preparation of myxoma virus suspended in normal rabbit serum had a half-lifetime of 11 days at 4° C., 5 days at 18–20° C., and 31 hr. at 27–28° C. Apart from losses due to probing (about 12% of the virus load per probe) viable virus on the proboscis of the mosquito probably disappears at about the same rates.

1. An M-producing strain of Streptococcus pyogenes type-12 was shown to be carried on the surface of apparently healthy tonsils for at least 3 years.

2. Loss of M substance in a strain of type-3 in a tonsillar carrier was shown to be by gradual replacement of matt forms by glossy variants. This pair of naturally occurring variants showed very different growth rates as mixtures in liquid media.

3. Under suitable conditions, glossy variants regularly appeared and replaced the M-producing strain from which they were derived in these and all other strains of type-3 and type-12 tested from a wide variety of sources.

4. It is suggested that the selection of variants by the differential nutrient value of the micro-environment is the deciding factor in carrier strains showing loss of M substance.

An investigation in an urban area of south-east Kent of 160 patients who had had either pneumonia or unexplained fever during the period from the end of 1948 to the beginning of 1954 revealed that twenty-three (14%) had probably had Q fever.

A comparison of the epidemiological histories of patients who had had Q fever with those of the remainder showed that the use of a household supply of raw milk was commoner among the former.

Occupational exposure to animals (or animal products), visits to potentially infectious places, or residence near potential sources of infection were not significantly more frequent among the Q-fever cases as compared with the controls.

The isolation of Rickettsia burneti from the bulked milk of some local herds supplying retail dairies in the towns, together with the general epidemiological evidence, suggested that Q fever in the towns was predominantly milk-borne.