Phage adsorption by resistant staphylococci was studied.

Staphylococcal cultures previously allowed to adsorb phage to which they were resistant remained as sensitive to their appropriate phages as normal cultures of the same strains.

When pooled related and unrelated phages were incubated with their propagating strains, the results resembled those obtained when these phages were incubated separately with the same strains.

The lytic effects of thirty-two phages at test dilutions were tested singly and when pooled into five mixtures. All the phage-propagating strains and over 500 strains received for typing were tested. The results were in agreement.

Thirty-two phages at their test dilution in nutrient broth remained stable, whether pooled or not, at 0 to + 5° C. for various times. Briefly summarized, serological group A phages were stable for at least 1 month, and group B phages were stable for only 2–3 weeks.

Broth cultures of staphylococci incubated for 18 hr. at 30° C. were as phage-sensitive as the same cultures when left at room temperature for 24 hr.

A new method of phage typing staphylococci by means of phage pools, as satisfactory as the standard method, and less laborious, is described.

1. Colonies of wild Rattus norvegicus Berkenhout were kept in closed rooms containing nesting sites. The conditions permitted breeding.

2. Seventy-six experiments, each lasting 6–35 days, were done to test the rats' food preferences. In each experiment except two, a choice was given between two foods, both available in excess. In the two exceptional experiments a choice between three foods was given.

3. Although marked preferences were shown, a food was rarely quite rejected in favour of an alternative.

4. Among cereals, wholemeal was preferred to wheat grains, but wheat grains were preferred to white flour; little or no white flour was eaten if wholemeal was available. Wheat germ was eaten only in small quantities when an alternative cereal was available, but in larger quantities if the alternative was sugar or a sugar-cereal mixture.

5. The addition of sugar or saccharin to cereals increased acceptability; sugar was preferred to saccharin.

6. The addition of arachis oil to wholemeal or wheat increased acceptability.

7. Cod-liver oil at 2·4 % acted as a deterrent.

8. Total calorific intake remained steady over short periods, but over several weeks rose as the mass of the rat colony increased. The higher the mean weight of the rats in a colony, the lower the calorific intake per unit weight of rat.

9. The amount of food eaten was partly determined by its calorigenic capacity: in particular, wet foods were eaten in much larger quantities than dry foods.

10. The food preferences of wild rats differ in several respects from those of white Rattus norvegicus.

11. Apart from palatability or flavour, the main factors influencing food preference were (a) previous experience and probably (b) the nutritional value of the food. The effect of previous experience was often observed when rats, accustomed to one food, gradually changed from the accustomed food to another. The stages of a change to a new food, or the establishment of a particular preference, varied, and are discussed in detail.

The way in which rats and mice eat whole grains of wheat, barley, oats and maize has been studied.

Rats (Rattus norvegicus and R. rattus) hold grains with the long axis parallel to that of the body and eat the germ end of the grain in preference to the rest.

Mice (Mus musculus) hold grains with the long axis at right angles to that of the body and attack first the cheeks of all grains except maize, of which only the germ and scutellum are eaten.

It is suggested that texture is in the main responsible for the selection of a particular part of a grain.

Biochemical and serological investigations were made upon Bact. coli O 55 B 5 strains isolated from infants with diarrhoea and vomiting. On the basis of their reactions with six fermentable substances and of their H antigen types, the strains could be differentiated into three sero-fermentative types, I, II and III, which comprised, respectively, those having H6, H2 and H7 antigens.

We wish to acknowledge our thanks and indebtedness to the following: the Chairman and Members of the Tottenham Group Hospital Management Committee, and Dr T. H. C. Benians, Dr W. I. Leslie and Dr R. Swyer, for facilities for research in the laboratory and wards of St Ann's General Hospital; Mr L. G. C. Maslen for most valuable advice and assistance; the entire laboratory staff for their willing and efficient help.

Fusiformis is a multicellular organism having the cytological characters of the Eubacteria, and normally reproducing by fission.

A few cells of all the strains examined pass through the L cycle; usually the initiation of this process follows the patterns described in Proteus and the Morax-Axenfeld bacillus. It has not so far been possible to grow these L-forms of Fusiformis in culture without immediate reversion to the bacillary form.

The stable forms described by other workers appear to be produced by a process analogous to the sexual conjugation seen in the Actinomyces.

The evidence suggests that passage through the L cycle is a normal function of Fusiformis in its natural habitat.

Quantitative methods have been used in several investigations by Kabat and his colleagues (1945–50) in the study of serological relations of various preparations of blood-group substances. The investigations have taken twoforms: (1) the amounts of antibody nitrogen precipitated from a standard volume of an antiserum by varying amounts of the blood-group substances have been plotted against the amount of blood-group substance added; (2) the hexosamine has been measured in the precipitates formed with antiserum in the zone of antibody excess and the ratio of hexosamine precipitated to hexosamine in the blood-group substance added has been calculated; the amount of methyl-pentose precipitated has also been measured (Kabat, Baer &Knaub, 1949) and the ratio of methyl-pentose precipitated to methyl-pentose added hasbeen calculated.

1. Among infants attending Child Welfare Clinics there was a steady decline in the incidence of nasal carriage of Staph. aureus over the first year of life.

2. Infants born in hospital showed a much higher incidence of Staph. aureus in the first 2 months of life than infants born at home. A similar difference was also very distinct in the later part of the first year of life.

3. Mothers delivered 2 weeks to 2 months previously had a higher incidence of nasal carriage of Staph. aureus when delivered in hospital than when delivered at home. After this interval the incidence was similar in all groups of mothers throughout the rest of the year.

4. In the first few months of life there was a tendency for carriage in infants to be associated with carriage in the mother, but towards the end of the year there was no such relationship. This association appeared most clearly in infants born at home and in infants 2–5 months old born in hospital F.

5. A very high proportion (25 out of 30) of the strains tested from infants born in hospital F less than 5 months previously were penicillin-resistant. Infants born at home had a much lower incidence of resistant strains.

6. A high proportion of strains of Staph. aureus isolated from mothers delivered in hospital F were resistant throughout the first year. Strains from mothers delivered in hospital C or at home showed a much lower proportion of resistant strains.

7. Phage-typing showed a great variety of types, but those found among the penicillin-resistant strains were rather less varied than among the sensitive strains. When Staph. aureus was found both in infant and mother, although the same phage type was commonly present in both, in 16 out of 35 couples different types were found.

8. Investigation in maternity hospitals C and F showed a high proportion of penicillin-resistant strains of Staph. aureus among the nurses and infants and in the dust of the nurseries, but not among the mothers. There was no important difference between the two hospitals as regards the incidence of resistant strains isolated from nurses and infants in spite of the differences found in babies from the two hospitals when swabbed at the clinics.

9. The significance of these results is discussed.

1. Outbreaks of mild food poisoning have been investigated in which heat-resistant Cl. welchii appeared to be the causative organism. The outbreaks were characterized by colic and diarrhoea without vomiting, commencing 8–20 hr. after ingestion of the contaminated food.

2. The strains of Cl. welchii concerned are only feebly toxigenic, and apart from the heat-resistance of their spores, and some colonial characters, fit well into Cl. welchii Type A. The toxin production and the serology of the strains is uniform within an outbreak.

3. Mild food poisoning similar to that seen in natural epidemics has been produced in volunteers by ingestion of cultures of heat-resistant Cl. welchii isolated from contaminated meat.

4. Infection is almost invariably due to meat which has been boiled, steamed, braised, stewed or insufficiently roasted, allowed to cool slowly, and eaten the next day, either cold or reheated.

5. Outbreaks of this kind should be prevented by cooking meat immediately before consumption; or, if this is impossible, by cooling the cooked meat rapidly and keeping it refrigerated until it is required for use.

During the investigation of a number of epidemics of Clostridium welchii food poisoning (Hobbs, Smith, Oakley, Warrack & Cruickshank, 1953) the opportunity arose of examining some 500 different strains of Cl. welchii for toxigenicity. Work on so large a scale made it essential to develop a routinefor this purpose, and after several trials we devised the folio whig sequence of tests, which have proved entirely satisfactory in our hands, and may be of interest to others.

1. An electrophoretically homogeneous antigen preparation extracted from a strain (LII) of Pseudomonas aeruginosa by trichloracetic acid inhibits four phages active against this strain, and two phages (5 and 14) to which it is resistant but which attack a mutant strain LIII–3 bi.

2. An extract prepared in the same way from strain LIII–3 bi has no antigenic or inhibitory properties. Lysis of LIII–3 bi organisms by chloroform, however, yields a potent inhibitor active against several phages.

3. TCA extracts from immunologically distinct Ps. strains AII, BII and GII also inhibit phages 5 and 14 to which these strains are resistant.

4. The effect of a third phage (13) on Ps. LIII–3 bi is activated by the extract from strain LII which normally inhibits phages 5 and 14. Prolonged contact with very dilute solutions of the extract also causes activation of phage 5. Activation of phage 14 has not been observed.

5. The above findings are discussed in relation to current theories of phage action and phage inhibition.

1. When coagulase-positive staphylococci are grown on nutrient agar containing fresh mammalian serum and haemoglobin, discrete areas of clearing appear in the medium near to the growth.

2. These ‘plaques’ are due to proteolysis, the haemoglobin acting as a chromoprotein indicator substrate. For convenience the effect is referred to as ‘proteoclast’.

3. The effect is due to the interaction of a diffusible product of the staphylococci with constituents of normal sera. The staphylococcal factor has been obtained in a bacterium-free filtrate and its interaction with serum studied quantitatively. It resists boiling.

4. The number of plaques produced under defined conditions showed a linear correlation with the amount of serum used, but not with the amount of filtrate.

5. By means of serial filtration through Gradocol membranes it was shown that one factor in normal serum required for the proteoclast effect is particulate, having a size of the order 20–70 m μ diameter.

6. It was found that a third factor present in fresh sera was also required.

7. Serum was rendered inactive by conditions of heating and ultra-violet irradiation similar to those required to sterilize vegetative bacteria and viruses.

8. It is suggested that the proteoclast effect is due either to a non-pathogenic virus, or to a hitherto unrecognized particulate enzyme precursor present in sera and activated by the staphylococcal factor.

1. Glycine, alanine, and several isomers of alanine, DL-glutamic acid and DL-aspartic acid, when added to fresh guinea-pig serum and allowed to stand on the bench for half an hour, will protect the complement of this serum from destruction by heating at 55 and 56° C. for half an hour, but most of the complement activity is destroyed by heating at 57° C. and it is completely destroyed at 58° C. after half an hour.

2. Derivatives of glycine do not have any protective effect.

3. Various substances of high molecular weight, that might be described as ‘protective colloids’ do not have any protective effect.

4. How these amino-acids when added to serum alter the heat-lability of the complement is not understood.