Bacteriological Landscape

BACTERIOLOGICAL LANDSCAPE (or landscape), a method for studying the activity of microbes in natural conditions—in non-sterilized soil, "living," in the apt expression of S.N. Winogradsky, who first applied it—in soil where the life of each microbe is directly dependent on the flora surrounding it and on the physical and chemical properties of the soil itself. Thus, the researcher does not isolate a given microbe from its usual environment and place it in artificial conditions, as happens when studying pure cultures of microbes, but has before him the entire so-called B. p. (or landscape). It is self-evident that only studies of this kind can give a correct understanding of the processes occurring in a given environment depending on the existing bacterial flora. This method of studying the "activity" of microbes, named by S.N. Winogradsky "direct" (méthode directe), was first applied by him for soil research in 1923. Such a rational method could not fail to find application in medical microbiology for identifying the functions of the bacterial flora in its complete composition, where we are not dealing with pure cultures but with the cohabitation of many species of microorganisms, which in turn depend on changing conditions of the external environment. This primarily applies to intestinal flora, which is extremely rich not only in the number of microbes but also in the diversity of their species. It includes facultative and obligate anaerobes, coccal, bacillary forms, and vibrios, both non-staining and Gram-staining, with very different functions. Thus, some microbes develop mainly fermentative activity, breaking down carbohydrates with the formation of acid and gases, while another part of the microbes exerts mainly proteolytic action on proteins, developing mainly putrefactive processes. The predominance of certain forms of microbes determines the character of biochemical processes in the intestine. The composition of the intestinal flora is directly dependent, first of all, on the composition of the medium on which it grows (the predominance of carbohydrates or proteins in it), so it is understandable that from the "direct" study of the bacterial flora, one can conclude about the state of the function of the digestive tract and its deviations from normal in one direction or another. From this, therapeutic measures can also follow, directed to a large extent at changing the dietary regimen. This method made it possible to rationalize Mechnikov's doctrine of the arbitrary change of intestinal flora by introducing into the intestine microbes that change the character of processes in the direction of acid formation. Due to the acidic reaction of the medium, putrefactive bacteria disappear, and at the same time the amount of toxic products formed in the intestine and entering the general bloodstream also decreases. Thus, it was proved that the Bulgarian bacillus, recommended by Mechnikov, does not take root in the intestine, whereas the equivalent Bacterium acidophilus does. American and Japanese researchers firmly took the path indicated by S.N. Winogradsky and gave new methods based on the ideas underlying the direct microbial study of soil. Such are the studies of H. Tsuchiga, who distinguishes the following types of intestinal flora: 1) fermentative flora, when there is a predominant amount of Bacterium acidophilus; such flora is very favorable, as fermentation does not cause excessive gas formation; 2) semi-fermentative flora consists of a large amount of Bacterium acidophilus, but also of ordinary intestinal bacilli and sometimes streptococci; 3) mixed consists of all intestinal microbes, with Bacterium acidophilus and Bacterium Welchii often present in a small percentage; 4) semi-putrefactive, with the predominance of putrefactive microbes, sometimes Bacterium acidophilus may also be present; 5) putrefactive, with a large predominance of ordinary intestinal bacillus and spore-forming anaerobic bacilli; Bacterium acidophilus may be completely absent. With this last flora, proteolytic processes predominate sharply in the intestine with abundant gas development, which is why it is least favorable. The listed types of intestinal flora can be characterized by the percentage of Gram-positive forms of microbes they contain, namely they contain: fermentative flora—75-100% Gram-positive microbes, semi-fermentative—55-70%, mixed—35-50%, semi-putrefactive—10-30% and putrefactive—5-30%. There is no doubt that the method of S.N. Winogradsky should yield fruitful results in studying complex and still obscure questions of epidemiology, such as, for example, the question of the causes of development and spontaneous extinction of epidemics.