René J. Dubos

Bacterial and mycotic infections of man

Dacterial and mycotic infections of man , Dacterial and mycotic infections of man , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Rapid and submerged growth of mycobacteria in liquid media

Summary Addition to Longs synthetic medium of small amounts of phosphatides and of long chain fatty acids esters of polyhydric alcohols permits submerged and rapid growth of tubercle bacilli; the different groups of mycobacteria appear to exhibit differential optima with reference to these two types of substances.

The indigenous flora of the gastrointestinal tract

ConclusionsThe bacterial species that are most abundant in the gastrointestinal tract under normal conditions are anaerobic and have exacting growth requirements. As they display only a narrow range of biochemical activities, it is probable that the chemical transformation of metabolites in the gastrointestinal tract is less pronounced when these organisms predominate than when others gain the upper hand under pathologic conditions. In other words, the composition of the gastrointestinal flora determines the nature of the bioactive substances that are produced through metabolic transformation of amino acids, bile acids and other metabolites. Such biochemical activities may be as important as the orthodox pathologic lesions caused by pathogens.The microorganisms of the indigenous flora exert morphogenetic effects that are essential for adequate histologic development and for the healthy function of the gastrointestinal tract. The most important species of this flora are not necessarily those which multiply most abundantly within the lumen, but rather those which selectively become associated with the mucous layer in the different parts of the gastrointestinal tract.In brief, the microbial flora affects the histologic structure of the gastrointestinal tract and the kind of substances that are released from it into the general circulation. The different parts of the digestive tract, the various microbial species that they harbor selectively, and the physiologic conditions that govern the interplay between the host and its indigenous flora constitute a highly integrated ecosystem. Interference with any component of this system is likely to disturb its equilibrium and therefore to result in pathologic manifestations.

Bactericidal Effect of an Extract of a Soil Bacillus on Gram Positive Cocci

An unidentified spore-bearing bacillus, capable of causing the lysis of living gram-positive cocci, has been isolated from a soil sample to which suspensions of these cocci had been added over a long period of time. Autolysates of cultures of the soil saphrophyte have yieded a soluble factor which lyses living staphylococci, pneumococci (R and S forms, irrespective of typederivation), hemolytic, green and indifferent streptococci (all types so far tested). The active principle is not volatile, does not dialyze through collodion membranes, and is heat-labile. It is very stable at alkaline reactions, but is rapidly inactivated at reactions more acid than pH 5.5, even at room temperature. When maintained at 0°C, the active principle can be precipitated quantitatively at pH 4.2-4.4, and the precipitate, redissolved in a neutral medium, exhibits the lytic activity of the original solution. Several tests have been used to investigate the effect of this soluble extract upon the living cells of a number of bacterial species. 1. Lytic activity. 1 mg (dry weight) of the bacterial extract, added to 109 pneumococci in a medium at pH 7.5, causes complete lysis of the bacterial cells after 1 hour at 377°C. Staphylococci undergo solution under the same conditions, but somewhat more slowly. Although lysis of streptococci can also be obtained, it is always less complete and requires larger amounts of extract. 2. Bactericidal efect. Pneumococci, streptococci, and staphylococci incubated at 37OC with the extract, are rapidly killed. For instance, 1 mg of extract (dry weight) is enough to kill 1010 pneumococci or streptococci in 2 hours at 37OC. Similar results have been obtained with staphylococci. The cocci, however, do not lose their viability when the mixtures of extract and bacterial cells is maintained at O°C even for several hours.

Action of the Lytic Principle of Pneumococcus on Certain Tissue Polysaccharides

Avery and Cullen 1 obtained from both rough and smooth pneumococci a ferment capable of lysing heat-killed pneumococci. In unpublished experiments (Dubos) it was found that the same ferment preparation renders ineffective in rabbits the capsular type specific antigen of killed cells of virulent pneumococci. A hydrolytic action of the ferment preparation of pneumococcus on two tissue polysaccharides is described here. This action seems to be identical with that of the same ferment on the pneumococci. From bovine vitreous humor and from human umbilical cord two polysaccharides have been obtained in pure form, seemingly identical in composition, rotation, and general physical behavior. 2 They are composed of acetylglucosamine and glucuronic acid, the components having been shown to be present in equimolar ratio by isolation or quantitative analysis. The 2 polysaccharide acids yielded reducing sugar following hydrolysis by the ferment obtained from pneumococcus autolysates. The hydrolysis is optimal between pH 5 and 6, and does not take place above pH 8 nor below pH 4.5. The action of the ferment on killed pneumococci has about the same pH optimum. The action on both the pneumococci and the 2 polysaccharide acids is abolished by heating the ferment or by treating it with iodine. The iodine inactivation is reversed by sulfite and to a lesser degree by arsenite, as measured by the polysaccharide hydrolysis. Further evidence that the same principle is active against the 2 tissue polysaccharides and the pneumococci is found in the following inhibition reaction: 2.0 cc. of a 0.1 percent pneumococcus ferment solution in phosphate buffer at pH 6.0 were incubated for 6 hours with 10 mg. of polysaccharide (vitreous and umbilical cord). When tested against a suspension of heat-killed pneumococci at the end of the incubation period, the ferment was found to have lost at least 90% of its lytic activity. The control ferment solution also incubated at pH 6.0 for the same length of time in the absence of the polysaccharide retained all its activity.

Effect of Penicillin on the Tubercle Bacillus in vitro.

Summary and Conclusions Using appropriate experimental conditions, a virulent human strain of M. tuberculosis has been found to undergo partial lysis in the presence of high concentrations of penicillin. Small inocula of tubercle bacilli are highly susceptible to concentrations of penicillin as low as 1 unit per cc in the Tween-albumin medium. In the oleic acid-albumin medium, penicillin in a concentration of 100 units per cc causes no inhibition of growth, even with the smallest inocula Preliminary experiments indicate that in both the solid and liquid oleic acid-albumin medium, penicillin in concentrations of 50 to 100 units per cc may prove a valuable adjunct in culturing tubercle bacilli from contaminated materials.

THE UNKNOWNS OF STAPHYLOCOCCAL INFECTION

The greatest merit of this monograph is the emphasis that it places on all the uncertainties of our knowledge concerning the bacteriology, the pathogenesis, and the epidemiology of staphylococcal infections. Unfortunately, little positive new information will be found in these pages. The only recourse remaining to the text-book writer will be to heed Chesterton’s advice and . . . never, never doubt What nobody is sure about. For the investigator, on the other hand, these papers will have mapped out many areas in which critical research is greatly needed. Among the many questions that cry out for an answer, I shall mention but a few of those that are implicitly or explicitly raised in this publication.

THE EFFECT OF SPECIFIC AGENTS EXTRACTED FROM SOIL MICROÖRGANISMS UPON EXPERIMENTAL BACTERIAL INFECTIONS

Excerpt Organic matter does not accumulate in nature; it rapidly becomes the prey of countless species of microorganisms which break it down, stepwise, to carbon dioxide, water, ammonia, and minera...

Action of gramicidin on streptococci of bovine mastitis.

Gramicidin—an alcohol-soluble, water-insoluble substance isolated from cultures of a sporulating bacillus—has been shown to exert a marked bactericidal effect against gram-positive microorganisms, both in vitro and in vivo. It has been found for instance that 0.002 mg of this substance injected intraabdominally into white mice, exerts a therapeutic action against experimental peritonitis caused by pneumococci and streptococci; gramicidin, however, has proved almost completely ineffective when administered by the intravenous, intramuscular, or subcutaneous route. 1 2 3 It is known that in the chronic form of bovine mastitis caused by Streptococcus agalactia (Lancefield group B), the infection is confined to the infected quarter of the udder and rarely results in a demonstrable systemic disturbance. It appeared of interest, therefore, to determine whether gramicidin, when injected into the infected quarter, would destroy the streptococci causing the mastitis. A number of cases of chronic mastitis were selected for study and it was established by daily bacteriological examination of the milk that the numbers of streptococci remained high (over 100,000 per cc of milk) during a period of several weeks prior to treatment. The toxic reactions which result from the injection of gramicidin into the bovine udder and a convenient methcd of administration of the substance, were determined on 2 cows suffering from chronic mastitis. These animals received repeated treatments with increasing amounts of gramicidin diluted in Ringers solution, which proved very irritating, and later in distilled water, which was more satisfactory. The following technic was finally adopted for the treatment of each individual quarter. Gramicidin in amounts of 60 to 240 mg was diluted in lo00 cc of double distilled sterile water at 40°C. Following the morning milking, the residual milk in the cistern and in the teat was flushed out with 100 to 200 cc of a dilute solution of gramicidin; 800 to 900 cc of the preparation were then injected under pressure into the quarter and allowed to remain until the next milking.

Hippocrates in Modern Dress

When your Institute and Society were founded fifty years ago, the specialists in infectious disease, nutrition, and metabolism were still the scientific heroes of the medical world. Their disciplines had yielded rich harvests of practical results, and had enlarged mans understanding of his relation to the environment. The intellectual atmosphere in medical schools, however, was even then beginning to change. In 1920, the development ofa practical method for the production ofinsulin made it obvious that medicine had entered a new phase; emphasis had shifted from the external to the internal agents of disease. Today the focus of attention is shifting even further away from the preoccupations of the early 1900s. More and more scientific medicine is identified with the esoteric knowledge of molecular biology or biological electronics, and with the spectacular performances of medical engineering in the lungs, the brain, the heart or the kidneys. The ceremony marking your fiftieth anniversary is a salute to the past, but also a dedication to the future. As a representative ofone of the downgraded scientific disciplines, medical microbiology, I should therefore feel embarrassed at speaking for the future. But instead, I feel gently amused because I am convinced that the glamorous achievements of today will appear old fashioned fifty years hence. In fact, I shall take advantage of your invitation to play the prophet, and tell you of some of the topics likely to occupy a prominent place on your programs when you meet to celebrate your hundredth anniversary. As there is no good prospective without retrospective, I shall first try to review briefly the forces which have been at work during the past 2,500 years to prepare the forthcoming change in direction of medical