bluuebunny/crossref_metadata_2025_split huggingface dataset:
The growth of micro-organismsin vivowith particular reference to the relation between dose and latent period
Authors: Meynell G. G. , Meynell Elinor W. 
Published: May 2009

The growth ofSalmonella typhimuriumin mice was studied by performing viable counts on pooled viscera and, in the case of fatally infected mice, by determining the relation between size of dose and mean death time. The results suggested that this system conformed to a general model which postulates (a) that the organisms causing the response (death in the present experiments) increasein vivoat a rate which is constant for all doses, and (b) that the response is certain to occur when their number reaches a constant figure. It follows that logarithm of dose (for doses > 1 ED50) should be linearly related to mean latent period (the interval between inoculation and response). A search of the literature showed that this relation was observed in many reported infective systems.The interpretation of the observations on partially resistant mice (LD50= 102.5−106organisms) was not straightforward for the hypothesis of independent action (Meynell & Stocker, 1957) states that only a random fraction of the inoculum usually initiates each response. Multiplication of this fraction is considered to cause a reduction in host resistance so that other organisms survivingin vivobegan to increase in numbers and to contribute to the fatal infection. The observations showed that this could well occur as (i) the counts on all mice, whether fatally infected or not, increased exponentially for 2–3 days after inoculation; (ii) the growth curves of fatally infected mice showed exponential increase of the whole inoculum as postulated; and (iii) the length of the death time was found to be determined by the growth of the whole inoculum and not by the predicted random fraction. The viable count per fatally infected mouse at the time of death was approximately constant at 108.75organisms. There was no evidence that the course of the infection was influenced by organisms which may have been killedin vivoas the requirements of the model were satisfied by the observed behaviour of the viable organisms alone. The rate of increase of organisms in a fatally infected animal was found to be less, the greater the LD50of the host; which suggested that the degree of host resistance was determined by successive random events occurring after inoculation.The latent period/log dose curve provides a new test of the hypothesis of independent action, since this predicts that most responses to doses equal to or less than 1 ED50are each initiated by only one inoculated organism. Hence, the latent period should become approximately constant at such doses. This was found to be so in the present experiments.The authors are grateful to the Medical Research Council for meeting part of the expenses of this work by a grant to G. G. M. They also wish to acknowledge the help of Dr W. R. Bryan, Dr B. Mandel, Dr D. B. W. Reid and Dr G. T. Stewart who provided unpublished data.
Airborne micro-organisms: a technique for studying their survival
Authors: Harper G. J. , Hood A. M. , Morton J. D. 
Published: May 2009

The concentration of viable cells in an aerosol of micro-organisms is reduced by physical loss and biological decay. To study biological decay it is necessary to distinguish between the two processes. The preferred way of doing this is to mix the test aerosol with a tracer which is subject only to physical loss: the tracer and test cells should be mixed before dissemination.The recommended tracers for bacterial clouds are bacteria made radioactive by growing on a medium containing 32P, then killed with formaldehyde and washed. To ensure closest identity of physical behaviour it is necessary that the tracer should be of the same species as the cells under test.We are grateful to Mr E. O. Powell for helpful comment during the preparation of this paper.
Leptospiral infection rates of wild rats in Britain
Authors: Broom J. C. 
Published: May 2009

1. Microscopical examination of the kidneys of 850 Rattus norvegicus killed in various parts of England and Wales showed an infection rate of 43% with leptospires, assumed to be Leptospira icterohaemorrhagiae for reasons stated.2. Infection rates calculated from the whole series were the same for rural, urban and sewer rats, but there were some local differences as between one area and another for both surface and sewer rats.3. An unusual feature was the finding of a 35% infection rate among young rats.4. In another series of 219 rats taken alive, agglutination tests and kidney cultures gave an infection rate of 43%. Kidney sections of 69 of these rats were also examined microscopically and the results of the different methods of examination were analysed.5. A similar survey was made on R. rattus. Only 2 of 88 caught in London were positive, compared with 31 of 35 killed in other towns. An additional 98 R. rattus killed during the fumigation of ocean-going steamers were examined, and 69 were found to be infected.I should like to record my thanks to the following members of staff at the Infestation Control Division of the Ministry of Agriculture, Fisheries and Food, Tolworth, Surbiton, Surrey, for their help in this survey: Mr C. J. Armour, Dr E. W. Bentley, Dr W. P. Crowcroft, Mr R. A. Davis, Miss Y. Larthe and Miss M. Lawrence. Also to the following Field Officers of the Ministry who supplied material for this investigation: Mr A. F. R. Brown, Mr R. J. Clark, Mr G. R. Hill, Mr A. C. Hopkins, Mr R. S. Jailler, Miss B. B. Jones, Miss M. Neve, Mrs J. C. Russell and Mr S. R. Surtees.I wish also to acknowledge the valuable assistance received from members of my technical staff, especially Miss Joan Messum and Mr R. J. Reed.
Studies of the loss of viability of bacterial aerosols: III. Factors affecting death rates of certain non-pathogens
Authors: Ferry Ronald M. , Brown William F. , Damon Edwin B. 
Published: May 2009

1. Additional quantitative studies of the survival of micro-organisms in aerosols are reported.2. Substitution of nitrogen for oxygen in the ambient medium decreases k′2, the rate of secondary loss of viability ofM. candidus, Esch. coliandS. marcescens, by 30–50%.3. The rate of primary decay (k′1) ofEsch. colidoes not appear to be affected by a similar change of atmosphere.4. The rate of secondary decay, k′2, ofM. candidusappears to increase two-to three-fold for 10°C. increments in temperature.5. Treatment of suspensions ofEsch. coliwith petroleum ether alone or containing lipid material increases k′1in aerosols generated from such suspensions.6. Treatment ofMyco. phleiwith petroleum ether appears to lower resistance to subsequent sonic irradiation.These observations are consistent with the hypothesis that differences in the physical and chemical structure of micro-organisms are reflected in constants k′1, k′2and b.We gratefully acknowledge the effective interest of two former assistants, T. Grant Maple and Eugene Mills, as well as the careful, effective, and conscientious work of our technical assistants, Ann Barr, Nora Galins, Cynthia Hartwig, Grace C. Leigh, Elizabeth Neidhardt, Paulette Slaney and Martha Szerslip, who have at different times helped secure the data presented here. Mrs Joseph J. Ecker deserves special thanks for care in the preparation of the manuscript.
The Type Classification of Staphylococcus Aureus: a Comparison of Phage-Typing with Serological Typing
Authors: Oeding Per , Williams R. E. O. 
Published: May 2009

A comparison has been made between the bacteriophage and serological methods for identifying types among coagulase-positive staphylococci. In only a few cases was one particular serotype clearly related to a particular phage-type, and in several cases single ‘types’ recognized by one method contained several different ‘types’ when tested by the second method. Nevertheless, when sets of strains isolated in the investigation of epidemics or of the nose and skin carrier state of particular individuals were tested by the two methods, consistent results were obtained: an individual combination of phage-type and serotype appeared to be stable.The principal advantages of phage-typing are the facts that it is able to recognize more types than the serological method, and that the distinctions between the types are based on a greater number of different reactions. The advantages of the serological method are the smaller number of untypable strains and its greater technical simplicity.Thanks are due to Miss Joan Rippon, Ph.D., for assistance in the analysis of the phage-typing results.
An Insecticide-Bait-Box Method for the Control of Sylvatic Plague Vectors
Authors: Kartman Leo 
Published: May 2009

Field trials were conducted in the San Francisco Bay region to test the effectiveness of 5 and 10% DDT powder in rodent bait-boxes against fleas on native wild rodents and in the rodent nests. The principal species concerned were known flea vectors of sylvatic plague, Malaraeus telchinum and Hystrichopsylla linsdalei, and the meadow vole, Microtus californicus, an important plague reservoir. Preliminary trials with the bait-boxes showed that Microtus and other small native rodents would enter them quite readily and feed upon rolled oats. About 90 g of either 5 or 10% DDT powder, placed on the floor boards of the bait-boxes, was picked up by the rodents and resulted in effective immediate control of all flea species. Residual control of all flea species on Microtus (with the possible exception of Hystrichopsylla linsdalei) was obtained over a period of several months. Analyses of Microtus nests showed considerable amounts of DDT which had been transported to them by the rodents. All flea species in nests were effectively controlled by 5% DDT for at least 132 days after the DDT was removed from the area.The field work was performed by Alva R. Kinney and Robert L. Martin. The fleas were identified by Harold E. Stark. The DDT analyses of rodent nests were done by the personnel of the Technical Development Laboratories, CDC, Savannah, Georgia, under the direction of J. A. Jensen.
Numerical Studies on Some Contagious Distributions
Authors: Spicer C. C. , Lipton S. 
Published: May 2009

A numerical investigation of three contagious distributions characteristic of epidemic data has been made using an electronic computer.All three show a modified threshold effect such that the proportion of a community affected tends to 100% as its size increases though there is no abrupt change of form.We would like to thank Mr M. J. R. Healy for assistance with one of the programmes, and Miss Molly Fretton for her help with the computing.
The influence of temperature and humidity on spore formation and germination inBacillus anthracis
Authors: Davies D. G. 
Published: May 2009

Experiments performed on spore formation inB. anthracis, in a wide range of closed atmospheres of chemically controlled humidity, showed that the sporing time ofB. anthracisis prolonged considerably as the humidity decreases, both at 26 and 37° C. The effect is less noticeable at the lower temperature.Experiments performed on spore germination in the same organism showed that a temperature range of 20–44° C. permitted germination of the five strains tested. Above a temperature of 39° C. and below 30° C. germination time lengthened considerably.Experiments performed on the influence of humidity on spore germination, both at 26 and 37° C. showed that no germination could take place at a relative humidity of 80% or below. Germination time was considerably prolonged when the humidity value fell below 100%.This work formed part of a thesis for the degree of M.D. in Bristol University. I wish to thank Dr G. S. Wilson for his advice in preparing this paper.
An outbreak of infection with Salmonella typhimurium in a general hospital
Authors: Datta Naomi , Pridie R. B. , Anderson E. S. 
Published: May 2009

An outbreak of Salmonella typhimurium infection in a large general hospital is described. The outbreak was spread over some 20 weeks and gave rise to 102 cases of enteritis and there were at least 150 symptomless excreters of the organism.Evidence is presented to support the view that the method of spread was by cross-infection, not by contamination of food in bulk. Control measures, which ultimately brought the outbreak to an end, were instituted on this basis.We wish to thank Dr A. J. H. Tomlinson and his staff at the Public Health Laboratory, County HallS.E. 1 for the generous assistance they gave us in examining all the specimens from the hospital staff during the outbreak. The resources of the Department of Bacteriology of the Postgraduate Medical School were at that time largely devoted to teaching and adequate investigations could not have been made without this help. Dr Tomlinson also gave us much advice both during and after the outbreak for which we are most grateful.Dr E. S. Anderson, Director of the Central Enteric Reference Laboratory and Bureau, Colindale, London, N.W. 9, very kindly undertook the phage-typing of many of the strains of Salmonella typhimurium isolated and we wish to express our thanks to him for this and other help he gave us in the investigation of the outbreak.Our thanks are also due to Dr Joan Taylor, Director of the Salmonella Reference Laboratory, Colindale, for her help and interest.Discussions with Dr R. M. Fry and Dr Joan Boissard in Cambridge in connexion with their investigations of a similar outbreak were most interesting and valuable and it gives us pleasure to thank them.We also acknowledge gratefully the help and co-operation of our colleagues at Hammersmith Hospital, especially Dr C. E. Roberts, the Medical Superintendent, and of those at the Postgraduate Medical School.
Ethylene oxide sterilization in hospital practice
Authors: Freeman M. A. R. , Barwell C. F. 
Published: May 2009

A non-explosive mixture of ethylene oxide and Arcton 12 is described. This mixture is now available commercially in this country.A sterilizing chamber and related equipment for use with this gas and a sterilizing technique are also described.Some applications of ethylene oxide sterilization are briefly discussed.
Some factors affecting preservability of freeze-dried bacteria
Authors: Obayashi Yoji , Ota Sunao , Arai Shiro 
Published: May 2009

1. The use of sodium glutamate as a medium for freeze-drying Lact. bifidus significantly enhanced the stability of the dried product, especially the heat stability.2. The optimal concentration of sodium glutamate, as a drying medium, was found to depend on the bacilliary concentration; the higher the concentration of the bacilliary suspension used the higher was found to be the optimal concentration of the sodium glutamate.3. It was possible to classify various drying media according to the degree of sublimation of the product during the process of freeze-drying. Two types were observed; in the first, which included sodium glutamate and glucose, the sublimation rate diminished with the increasing concentration of the medium, whereas in the second group, which included polyvinyl pyrrolidon K 90 (PVP), soluble starch and dextran, no such diminution was observed when the concentration of the medium was increased.4. By the combination of sodium glutamate or glucose with a medium belonging to the second group sublimation was found to be promoted.5. The stabifity-conferring effect of sodium glutamate on dried Lact. bifidus was markedly enhanced when the glutamate was combined with a drying medium belonging to the second group. This effect is attributed to a desiccation-promoting property of the latter medium.6. Lact. bifidus as a freeze-dried preparation showed a somewhat better survival rate when sealed in air than when sealed in vacuo. In the case of other anaerobic organisms tested there was no significant difference in the survival rates under the two methods of storage.
A comparison between the intranasal and intracerebral infection of mice with Bordetella pertussis
Authors: Standfast A. F. B. , Dolby Jean M. 
Published: May 2009

1. The main differences between intracerebral and intranasal infections in mice with virulent strains of Bordetella pertussis are in: (1) the responses to small in fecting doses (< 1 LD 50); (2) the action of antisera in controlling infection; (3) the action of toxin on brain and lung; and (4) the rates of increase of the viable count. The two infections can run concurrently in the same mouse without any demonstrable interference.2. The terminal viable count in the lung and brain is c. 108 organisms.3. In the brain there is no sublethal infection with virulent strains; probably even single organisms can grow up to the critical level and kill the mouse. In the lung sublethal infections are found in which the count rises to a figure below the critical level and then declines.4. The action of ‘intranasal’ antiserum is to reduce a lethal infection to a sublethal one in the lung but there is no effect in the brain. ‘Intracerebral’ antisera cannot act until the blood-brain barrier becomes leaky, when they are able to reduce the viable count and eventually sterilize the brain. In the lung ‘intracerebral’ sera have no action against lethal infections but can control small infections (<I LD 50). The sublethal intranasal test measures this effect but it also measures the action of ‘intranasal’ sera and so cannot be used to distinguish the two types of sera and hence the two antigens.
Infection of mice by the respiratory route with Salmonella typhimurium
Authors: Darlowa H. M. , Bale W. R. , Carter G. B. 
Published: May 2009

Experiments have been described in which mice were infected by the inhalation of a mono-dispersed aerosol of Salm. typhimurium. The disease so produced was characterized by a specific primary pneumonia. The lethal dose was very much smaller than that required by ingestion, and was approximately equal to the intraperitoneal lethal dose. Possible implications have been discussed.The authors wish to thank Mr S. Peacock for his invaluable help in the operation of the Henderson apparatus, and Messrs A. V. Lowle and C. M. R. Pitman for technical assistance. We also wish to thank Dr J. S. Paterson for supplying some of the bacterial strains, and for much advice and encouragement.
The epidemiology of the common cold II. Cross-infection and immunity
Authors: Lidwell O. M. , Williams R. E. O. 
Published: May 2009

Analysis by epidemiological methods of the spread of the common cold among office workers and their families has failed to account for more than a fraction of the infections as a consequence of known exposure to infected individuals. Infections too mild to be recorded as colds, survival of the virus in the environment and its subsequent dispersal are considered as possible explanations of this.The distribution of serial intervals between colds suffered by members of the same family indicates that the median interval between the onset of an infection and the first symptom in infection apparently arising from it as cross-infections was between 21½ and 31½ days. This is only slightly longer than the median interval, 2·4 days, observed between nasal installation and the onset of symptoms in experimental infections.There is some epidemiological evidence that susceptibility to the common cold is reduced during the weeks following a cold.We should like to repeat, in this the second paper in this series, our thanks to the Ministry of Pensions and National Insurance and to the Shell Petroleum Company, to those members of their staffs and to the nurses and others who helped us in this investigation.
Sodium fluoracetate and fluoracetamide as ‘direct’ poisons for the control of rats in sewers
Authors: Bentley E. W. , Hammond L. E. , Bathard A. H. , Greaves J. H. 
Published: May 2009

1. Field trials suggest that 3-monthly operations against rats in sewers using either 0·25% sodium fluoracetate or 2% fluoracetamide as a direct poison are more effective than 6-monthly treatments with 2·5% zinc phosphide or 10% arsenious oxide using the pre-baiting method.2. In six paired trials 2% fluoracetamide gave better results (an apparent 100% clearance in five instances) than 0·25% sodium fluoracetate.3. There is no evidence, at present, that direct poisoning treatments with 2% fluoracetamide or 0·25% sodium fluoracetate are improved by the addition of mould inhibiting substances to the bait.The work described above was made possible only by the co-operation of a large number of local authority councils and their staffs, to whom we are therefore much indebted. We wish to thank also, Mr J. D. Riley who gave considerable help during the early stages of the trials.
The effect of temperature on the growth of pox viruses in the chick embryo
Authors: Bedson H. S. , Dumbell K. R. 
Published: May 2009

The ‘ceiling temperature’ of a pox virus has been defined as the maximum temperature (to the nearest 0·5° C.) of incubation at and below which that virus will grow and produce pocks on the chorioallantois of 12-day-old chick embryos, and above which no pocks appear.Ceiling temperatures have been estimated for: alastrim (2 strains), 37·5° C.; variola major (2 strains), 3·8° C.; ectromelia (3 strains) and monkey pox (1 strain), 39°C.; cowpox (2 strains), 40°C. Five strains of vaccinia and two of rabbit pox were all capable of pock formation at 40·5° C. Above this temperature difficulty was encountered because many embryos died. But the ceiling temperature for two strains of vaccinia and one strain of rabbit pox was probably 41° C. The Utrecht strain of rabbit pox produced some lesions at 41·5° C.—the highest temperature used.The ceiling temperatures of the viruses used were not correlated with their thermal stabilities at 55°C.in vitro. Thus vaccinia strain, Lederle-7 N, had a high ceiling temperature and a low thermal stability, while variola major had a low ceiling temperature and a high thermal stability. For this reason ceiling temperatures and thermal stability are regarded as distinct characters.In experiments with twelve of the seventeen viruses of which the ceiling temperatures had been determined, the virulence for the chick embryo was then measured. It was found that, in general, the higher the ceiling temperature of a virus the greater was its virulence for the chick embryo.The presentation of these results is followed by a brief discussion of their significance and potential use.