The standard membrane filtration method of the UK has been modified in order to improve its specificity for enumerating Escherichia coli in the subtropical waters of Hong Kong. This involves incorporating into the membrane lauryl sulphate (mLS) method either an in situ urease test (the mLS-UA method), or an in situ β-glucuronidase test (the mLS-GUD method). The false-positive errors of the mLS-UA and mLS-GUD methods are low, ranging from 3–5%. A comparison between the membrane filtration (mLS-UA) method and the multiple tube technique in testing E. coli in subtropical beach-waters has demonstrated that the former can give much more precise counts, and is the method of choice for such a purpose. The mLS-GUD method, for which automated counting of E. coli colonies is possible, is a good alternative to mLS-UA in routine enumeration of this bacterial indicator in environmental waters.

Small rodent (vole) sera were collected from three different locations in Norway. One of these was within the distribution area for Ixodes ricinus, and a tick-borne encephalitis (TBE) virus strain had been isolated from ticks collected there (Traavik & Mehl, 1977). The two other locations were outside the I. ricinus area, one in southern Norway, the other at nearly 70° N. The sera were tested for TBE antibodies by hemagglutination inhibition (HI), hemolysis-in-gel (HIG) and complement fixation (CFT). All sera were also tested for HI antibodies to Uukuniemi (UUK) virus, and some positive TBE HI reactions were verified by separation of immunoglobulins and serum lipoproteins in NaBr gradients.

Animals containing TBE virus antibodies reacting in all three serological tests and animals with UUK HI antibodies were detected only from the location within the I. ricinus area. From the two locations outside the I. ricinus area we found animals which had antibodies reacting with TBE virus in HI and HIG, but not in CFT. Antibodies to UUK were not detected. The results indicate that flavivirus(es) related to, but not identical with TBE viruses are transmitted by other vectors than I. ricinus in parts of Norway.

Although knowledge of principles determining variation is imperfect, some progress has been made and further help may be obtained from some of the newer conceptions about combining affinities regulating normal growth. There are reasons to believe that growth depends on a rhythmic cycle of synthesis, peculiar to living protein, whereby at each successive stage one particular “building stone” is selected for synthesis, with rejection of all others. There is also some evidence that the surface of a growing bacterium passes through periodic phases. Additional light on the activities of the bacterial surface is thrown by the new conception of enzymes which regards them not as fixed chemical entities but as chemico-physical “centres of activity.”

Some of the principles which are gradually coming to light in bacterial variation may ultimately be of assistance in the much more obscure problem of explaining the change from the normal mammalian cell to its malignant variant. I refer in particular to conceptions, which I have discussed in the preceding part of this article, about the mechanism of cellular growth and the nature of a cell's combining affinities.

In the preceding reports on infant mortality in counties during 1908 (Cd. 5263), in 241 urban areas in 1907–10 (Cd. 6909), and in Lancashire (Cd. 7511), the chief environmental circumstances favouring excessive infant mortality have been enumerated and to some extent discussed.

A new salmonella subgenus I serotype is described. Strain C.S. 1608/73, serotype 67: r: 1, 2, was isolated from activated sewage sludge and was assigned the name S. crossness. The serotype is biochemically atypical in its ability to utilize sucrose and this ability appears to be controlled by a transferable plasmid.

In laboratory experiments the acute eye irritation produced by exposure to tap water was not significantly increased when chlorine compounds were added to the water at concentrations of 1 mg./l. The greatest irritation was produced by 2 mg. Cl2/1. as NH2C1. The addition of NaCl at concentrations above about 0·5% abolished the irritant effect of tap water, and prevented irritation even when 1 mg. Cl2/1. was present.

In a field experiment involving two swimming baths, one with fresh and the other with saline water (0·5 % NaCl), eye irritation in the saline bath was significantly lower than in the freshwater bath only when the swimming time did not exceed 30 min.

(1) The graphic method is more easy of application and requires less mathematical knowledge than the extended analytical method.

(2) In our experience it produces smooth curves of px and Ex.

(3) The analytical in the selection of the best process of interpolation appeals to the graphic method.

(4) While either the analytical or graphic process may in unskilful or careless hands give erroneous results, owing to errors in working out, the analytical process, unlike the graphic, presents a wide choice of methods, which although accurately worked out, give incomparable results.

(5) The facts given in the table on page 321 and in Fig. 1 A and B and table on page 317 show that almost identical results are obtained by the graphic method and by the improved extended analytical method. We regard this as important testimony to the accuracy of each of these methods, and at the same time as indicating the inaccuracy of the analytical methods giving different results.

(6) As the results obtained by the modified short analytical method and by the combined analytical and graphic method approximate so closely to those obtained by the detailed graphic method, either of them may safely be adopted by those who cannot spare time for working out a detailed Life Table by the graphic method.

(7) Every published Life Table should give exact details of the method of its construction, in order that the comparability of data and results may be tested. Much confusion has arisen, and important errors in comparison between different Life Tables have been produced, by the use of different methods of construction and the non-publication of details of methods.

1. By titration against horse serum and its protein fractions anti-horse sera can be divided into three groups, according to the antibodies responsible for the main or earliest particulating zone, namely the sera containing antibodies against (a) globulin only, (b) albumin only, and (c) both globulin and albumin.

2. For the quantitative estimation of a protein fraction in a horse serum it is necessary to use an antiserum containing a main zone antibody acting with that protein only.

This is illustrated in experiments, designed to show the increased globulin content of diphtheria antitoxin, in which antisera containing antibodies against both globulin and albumin failed to register an increase in the globulin content.

Fluorescein dispersed as powder into the air of occupied rooms was extracted in measurable quantities from dust after as many as twenty previous sweepings.

The value of fluorescein in showing the rate of removal of dust from occupied environments is discussed in relation to the transfer of infection.

Desert rodents often have been used successfully as laboratory animals in parasitology (Abdel Azim & Cowper, 1950; Adler & Feldman-Muhsam, 1952; Delanoe, 1929; Kuntz & Malakatis, 1954; Nicolle, Anderson & Colas-Belcour, 1927; Sergent & Poncet, 1951 a, b) and virology (Durand & Laigret, 1932; Gear & Davis, 1942; Noury, 1948; Snyder, Zarafonetis & Liu, 1945; Van Rooyen & Danskin, 1944; Zarafonetis, 1945). However, with the exception of investigations into the role of some of these animals as mammalian reservoirs of plague (Ristorcelli, 1938; Tikhomirova, 1934; Wassilieff, 1933), no reports have been found of their use for experimental bacterial infections.

In recent years immunity reactions have come to be regarded more particularly from the physico-chemical standpoint. Many of the phenomena occurring in immunity reactions are shown to be of the nature of colloidal chemical processes, and the laws which govern such processes have been found to hold, at least partially, for reactions occurring in sera, which belong to the class of colloidal protein solutions. Thus the application to immunity reactions, of such conceptions as viscosity and surface tension, has afforded a more reasonable explanation of these reactions. In the following paper special reference will be made to the surface tension, changes of which play an important part in all immunity reactions.

The immediate dispersal of a fluid delivered to anaesthetized mice by the intranasal and intra-oral techniques has been studied by means of a radio-active tracer method. The results clearly show that the intra-orally inoculated animal accepts a larger proportion of the total volume inoculated and that a significantly higher fraction of this reaches the lungs than in mice inoculated by the intra-nasal technique.

The authors would like to thank Dr I. Friedmann and Dr H. A. B. Simons for having made this work possible; also, Mr D. Arnott for a generous gift of labelled di-iodofluorescein, and Dr D. A. Osborn and Dr K. Weinbren for helpful suggestions.

1. Temperature influences the rate at which glycerinated lymph deteriorates in accordance with the law of Arrhenius, expressing the effect of temperature upon chemical action; the rate of deterioration increasing three times per 10° rise in temperature.

2. Dry powdered calf vaccine in sealed glass capillary tubes still gave rise to typical vesicles after exposure to a temperature of 100°C. for from 5 to 10 minutes.

3. The vaccine virus can withstand positive osmosis for 24 hours or more, and negative osmosis for 8 weeks or more, at room temperature.

4. It appears doubtful whether the vaccine virus will pass through a Berkefeld V filter even when a stored vaccine emulsion is used for filtration. If any virus does pass through it only does so exceptionally and in small quantities.

5. When a glycerinated vaccine emulsion is filtered, white flocculi frequently form in the filtrate. These are at first minute, but subsequently adhere and form a macroscopic sediment. This sediment, when inoculated on calves, does not cause vesiculation.

Microscopically these flocculi, in hanging drop preparations, resemble the vaccine bodies described by one or more observers.

A serious outbreak of staphylococcal infections in the maternity units in Blackburn was investigated. There were considerably more than one hundred cases of breast abscesses altogether, well over half of which occurred in primiparae. Staphylococcus aureus, phage type 80, was the predominating organism throughout the outbreak and at the peak period during the early part of the outbreak this type was responsible for nearly 80% of the infections.

After the introduction of a number of procedures for the general reduction of cross-infection the incidence of breast abscess fell markedly and a controlled trial of an antibacterial cream, containing neomycin and hibitane, which was applied to the nasal mucosa of all infants and mothers in the test group of patients, was undertaken. The conditions obtaining in the test and control groups were identical in every way except that the control patients did not receive the neomycin-hibitane cream. There were about 1250 mothers and infants each in the test and control groups; the incidence of breast abscesses in the test group was 0·8% and in the control group it was 2·7%. The method adopted for the detection and treatment of carriers among the nursing staff broke down on two occasions; this fact and the emergence of an unforeseen source resulted in a larger number of infections than should have occurred. Had it not been for these incidents there is little doubt that the trial would have shown more conclusively the effectiveness of the neomycinhibitane cream, by the method laid down, in reducing cross-infection.

Investigation of the bacterial flora on the nasal mucosa of over 1000 infants in the control group yielded results of considerable interest. Of 300 cases where there was early colonization by Staph. albus, this organism established its dominating position in 70% of the cases and it was not subsequently displaced by Staph. aureus. The significance of this observation and the evidence favouring nasal dissemination of Staph.aureus as the most important cause of hospital cross-infection are discussed.

In this paper the term B. coli is used in its most restricted sense, and as implying organisms having all the characters of the typical B. coli communis. It is a well-ascertained fact that B. coli, even when the term is so restricted, exhibit very varying virulence.

We quantified the potential impact of different social distancing and self-isolation scenarios on the coronavirus disease 2019 (COVID-19) pandemic trajectory in Saudi Arabia and compared the modelling results to the confirmed epidemic trajectory. Using the susceptible, exposed, infected, quarantined and self-isolated, requiring hospitalisation, recovered/immune individuals, fatalities model, we assessed the impact of a non-pharmacological interventions’ subset. An unmitigated scenario (baseline), mitigation scenarios (25% reduction in social contact/twofold increase in self-isolation) and enhanced mitigation scenarios (50% reduction in social contact/twofold increase in self-isolation) were assessed and compared to the actual epidemic trajectory. For the unmitigated scenario, mitigation scenarios, enhanced mitigation scenarios and actual observed epidemic, the peak daily incidence rates (per 10 000 population) were 77.00, 16.00, 9.00 and 1.14 on days 71, 54, 35 and 136, respectively. The peak fatality rates were 35.00, 13.00, 5.00 and 0.016 on days 150, 125, 60 and 155, respectively. The R0 was 1.15, 1.14, 1.22 and 2.50, respectively. Aggressive implementation of social distancing and self-isolation contributed to the downward trend of the disease. We recommend using extensive models that comprehensively consider the natural history of COVID-19, social and behavioural patterns, age-specific data, actual network topology and population to elucidate the epidemic's magnitude and trajectory.