Pyogenic Cocci and Intestinal Bacilli

bacillus has already been referred to. Pyogenic cocci are rarely absent from the intestines, where they may be present in such small numbers as to escape detection, but the great frequency with which they may be found in perforative peritonitis is significant. Bacillus proteus, Bacillus pyocyaneus, Bacillus tetani, Diplococcus lanceo- latus, Bacillus aérogenes capsulatus, and others have also been found. Much attention has lately been devoted to the presence in the normal intestine of “acid-staining ” bacilli having tinctorial reactions similar to those of the tubercle bacillus. Under normal conditions the intestinal bacteria are found only a short distance in the common bile-duct ; but any alteration from the normal, such as mechanical impediment to the outflow of bile, change in the composition of the bile, or other perturbation in the physiology of secretion, may be followed by an ascending in- fection of the ducts or gall-bladder. Contrary to the old idea, the bile has not been found to possess any decided bactericidal Property. Genito-urinary Tract.—It has been shown repeatedly that the anterior portion of the healthy male urethra contains bacteria. These are abundant and varied in the fossa navicularis, and diminish rapidly in number and kind toward the posterior part of the urethra. Urethral bacteria are usually present in urine voided after sterilization of the meatus and fossa, even in the urine passed toward the end of micturition. Among the non- pathogenic and pathogenic bacteria found in healthy urethras may be mentioned the smegma bacillus, Bacillus coli communis, and the so-called pseudogonococeus. The latter is of importance in reference to the diagnosis of gonorrhea by microscopic examina- tion. If, however, the morphology, staining reactions, and enclos- ure and arrangement within cells, characterizing the gonococens, be observed, a mistake in diagnosis is possible in only a small number of cases. 24 INFECTION CONSIDERED IN ITS SURGICAL RELATIONS. It cannot be said that the question has definitely been settled as to whether the bacteria of cystitis are usually those normally present in the urethra or those directly introduced from the meatus. The bladder-urine in health is germ-free. The female urethra contains micro-organisms, and the anatomic conditions are much more favorable than in the male for their passage into the bladder. The vagina also contains bacteria in varying number and kind. Pathogenic species are found only occasionally. The so-called “ vaginal saprophytes” are the bac- teria more constantly present, and are evidently harmless. The occasional presence of pathogenic organisms is usually transi- tory; they may, however, persist for a variable time as harm- less parasites. The experiments of Schluter and Witte on the effect of acid on certain bacteria, including pyogenic streptococci and staphylococci, show that the percentages of acid usually present in the vagina may inhibit their growth. Experiments by Kronig and Menge show that bacteria when introduced into the vagina disappear in a relatively short time. Irrigation of the vagina with water or with antiseptics retards the time of their disappearance. The body of the healthy uterus is ordinarily free from micro- organisms. Stroganoff’ found the bacteria of the vagina extending up to the mucous surface of the cervix but not penetrating it, and experimentally proved the mucus an unfavorable medium. Powerful as are the normal defences against bacterial invasion, they may, however, be overthrown under conditions very imper- fectly understood. The more important bacteria found in puerperal infections are the streptococcus and staphylococcus, Bacillus coli communis, and Bacillus aérogenes capsulatus (Plate I.). THE BACTERIAL EXCITANT AND HOST. Among the micro-organisms gaining entrance into the body, there are some which may under suitable conditions induce phe- nomena by which disease is characterized. These are the ones which induce infectious diseases, and which we habitually refer to as being pathogenic bacteria, The term pathogenic is, however, a relative one—a fact w should be held clearly in mind for the following reasons: first, an organism quite harmless to one animal may be capable of inducing disease in another ; secondly, an organism which under ordinary conditions is harmless may under special conditions give rise to special lesions; thirdly, many organisms generally regarded as harmless under special con- prove injurious. lent from what has been said that infectious disease ist without the presence in the body of living miero- cannot ¢: PLATE I. Cover-glass preparation of pericardial exudate showing bacillus pyocyaneus stained Section through wall of abscess showing staphylococcus pyogenes aureus. (Baum- blue, and the tubercle bacillus garten.) stained red. (Ernst.) Streptococcus pyogenes; streptococcus erysipelatos. (Prudden.) Micrococeus gonorrhaees or Micrococcus lanceolatus. aonococeus. (Abbott.) (Abbott.) Some Forms of Bacteria Giving Rise to Surgical Infections. THE BACTERIAL EXCITANT AND HOST. 25 organisms. But, on the other hand, the mere entrance of bacteria into the tissues is not sufficient to constitute infection, for it has been seen that many bacteria are harmless, and that the body pos- sesses important safeguards whereby bacteria are destroyed or their effects neutralized. Whether the micro-organisms possess patho- genic activity or not will depend largely upon the host, and also upen their own variable nature and qualities, This relationship of host and bacterial excitant has been stated so admirably by Prudden that one can do no better than quote the following : “In the study of the infectious diseases it is especially im- portant to bear in mind that the abnormal processes through which the disturbances incited by micro-organisms are manifested are processes of the body-cells, and not processes of the micro-organ- isms. The micro-organisms do indeed incite the train of phenomena by which the disease is manifested, and the nature or ‘species’ of the micro-organism may largely influence the character of the phenomena ; but the stored-up energy which is released in this manifestation is body-cell energy, and hot that of microbic metabo- lism. The microbes are excitants of disease, but the disease is a performance of the body-cells. If these obvious considerations be held in view, it will be convenient in considering certain of the infectious dixeases to use the familiar and much-abused term “specific’ as indicative of those phases of abnormal body-cell per- formance which are apt to occur in characteristic ways in response to special forms of microbic stimulus. Thus the poisonous sub- stances which the tubercle bacillus builds up out of the organic material upon which it feeds are in part such as exert a peculiar influence upon connective-tissue cells, leading to their proliferation and the temporary formation of new tissue—the tubercle. This, together with associated action of the same or other metabolic products of the living bacillus, forms a group of lesions and dis- turbances which is characteristic of the action of the tubercle bacillus in the body. In this sense tuberculosis is a ‘specific’ disease. On the other hand, the poisons eliminated by the tubercle bacillus may incite responses on the part of the body-cells which are practically identical with those which many other toxic sub- stances, both of bacterial and of other origin, induce—fever, degeneration, etc. These manifestations of the action of the tubercle bacillus upon the living body-cells are not specific.’ ” The Bacterial Excitant—The reaction of the body-cells in infection bears a more or less constant relation to the virulence of the infecting micro-organism and to the number of bacteria gaining entrance into the tissues. The virulence varies considerably under different conditions, and according as these variations are small or great, different phenomena will develop within the body. The char- 26 INFECTION CONSIDERED IN ITS SURGICAL RELATIONS. acter of the processes induced will necessarily vary according to the virulence of the infecting bacterium ; and this largely depends upon its environment, which may not only modify the morphologic char- acters of the organism, but also may change its physiologic activ ties. For example, Bacillus coli communis as found normally in the intestines is of very low virulence, and is not capable of in- citing pathologic processes ; but so soon as its physiologic activities are modified by changes in its environment its virulence is apt to be very much increased. This influence of environment is also well shown by the modifications which may occur in the vital activity of an organism when it finds its habitat in new and unnatural hosts. This point is demonstrated especially well with the mammalian tubercle bacillus, which when transmitted for a long time through another animal host, as birds, ultimately loses its virulence for the host from which it originally was derived. Bacteria which enter the body associated with their toxic prod- ucts are much better able to induce infection than when they enter deprived of their products. - These toxic substances, by damaging at the outset cells and fluids which protect the body from infection, enable the invader to gain a foothold which it otherwise might not have obtained. As a rule, bacteria lose their virulence with greater or less when cultivated in artificial media. On the other hand, ssages of a pathogenic orgai through highly susceptible animals exalt its virulence. Thus a streptococcus of attenuated virulence may be exalted a hundredfold or more by successive inoculations into rabbits. Differences in the virulence of bacteria often suffice to explain differences in the clinical and morphologic types of disease. It is well known that under some conditions an organism of low viru- lence will incite rather mild reactions of the body-cells ; whereas under other conditions, when the virulence of the same organism is exalted, the effects are more marked both in severity and extent of the lesions. The number of micro-organisms which gain entrance into the body is also a factor which modifies the character and extent of the cellular reactions. Within certain limitations the healthy body may dispose without apparent injury of a certain number of bac- teria of given virul ; but when the same organism ix introduced in large quantities infection follows. Tn highly susceptible animals probably so small a number as one or two anthrax bacilli may incite disease. Hy, however, much larger numbers are nec- essary for the development of an infection, The question of dosage is largely one of individual and racial susceptibility, on the one hand, and of virulence of the micro-organisms, on the other hand, THE BACTERIAL EXCITANT AND HOST. 27 The kind of infection produced by some bacteria varies with the dose. Thus it often happens that the introduction of a very small number will produce only a local infection, whereas larger numbers may induce septicemia. Further, according to the portal of entry, we find variations in the character of the infectious process. Thus a given dose of bacteria which when injected into the subcutaneous tissues of an animal may prove quite harmless, may induce, when the same dose is introduced intravenously or into the peritoneal cavity, well-marked abnormal cellular reactions. The study of the influences which other associated organisms may bring into play in the development of infection is an exceed- i interesting one. Mixed infections are common in the human being, especially in suppurating wounds, in which it is usual to find more than one bacterial species. Sometimes the association of one species may be without influence upon the properties of another, or it may enhance or lower the virulence of one or the other. Bacteria exert their influences on each other largely through their chemical products, and it is often possible to bring about modifications of character by exposing one species to the action of the chemical products of another. Sometimes concurrent inocula- tion of two different bacterial species inhibits the influence of one or both. Thus simultaneous inoculation of Bacillus pyocyaneus and Bacillus anthracis into a susceptible animal is often without pathogenic effect. More often, however, the concurrent inocu- lation of two species rather increases the danger from one or both, although sometimes a bacterium of attenuated virulence may beeome augmented in virulence by the inoculation of another spe- cies which need not necessarily be pathogenic itself. Thus the pathogenic effects of the tetanus bacillus are much enhanced when, it is associated with pyogenic bacteria. It sometimes happens that infection with one species paves the way for infection with another. The Host.—It is, of course, well known that certain bacteria will induce infections only in certain species of animals, proving absolutely innocuous for other species. Thus while the anthrax bacillus usually induces lesions with the greatest readiness in many animals, others, like the white rat, are ordinarily insusceptible to inoculation with these bacilli unless very large amounts be given or special factors be brought into play. Furthermore, some dis- «sex are especially peculiar to man, such as typhoid fever, syphilis, leprosy, scarlet fever, measles, etc., these diseases never occurring naturally in other animals. “ Racial predi-position may be inherited or acquired, or general or local. — Negroes are gencrally insusceptible to yellow fever, whereas other human beings are quite susceptible to the pathogenic agents of this disease. 28 INFECTION CONSIDERED IN ITS SURGICAL RELATIONS. The influence of age is so well known that investigators com- monly make use of this knowledge in their experimental work. As a predisposing factor to infection this is well illustrated by the curve of frequency of infectious diseases in man, the maximum point occurring in children. Sex is also sometimes a factor pre- disposing to infection. Numerous other conditions affecting the normal physiologic integrity of the body also favor the develop- ment of infectious disease. For example, the influence of fatigue, starvation, cold and heat, and loss of blood, has been studied par- ticularly from an experimental point of view, the results conclu- sively proving that a marked susceptibility to infection is devel- oped when any of these factors is brought into play. Any traumatic injury to the body-tissues also favors the lodge- ment and activity of whatever bacteria may reach the affected area. This is illustrated by the well-known clinical fact that tuberculosis of bones and joints of children often follows different forms of trauma, Other factors have also been investigated, such as the action of chemical substances and unsuitable diet, the latter especially by Hankin, who fed refractory rats on sour milk and bread. Such treatment made the animals extremely susceptible to anthrax infection. The local predisposition may be limited to one or more of the portals of entry, or it may exist at some point within the body, constituting a so-called locus minoris resistentia. The character of the tissue infected, the presence of local anemia or passive hyper- semia, the withdrawal of nerve-impulses from a point, the rapidity of absorption, the presence of foreign bodies, are also modifying factors in the susceptibility to infection. Wounds through poorly vascularized tissue generally offer but slight resistance to bac- terial invasion. The presence of cedema in the tissue likewise favors infection, Contrary to the general belief, suppurating surfaces offer con- siderable resistance to the entrance of bacteria into the body, for pus possesses distinct bactericidal power, partly from the cells and partly from the fluid portion, Thus the danger of bacterial ab- sorption from suppurating surfaces is much less than from fresh wounds. The existence of suppuration, however, lowers the gen- eral resistance of the individual. Among the local conditions favoring the growth, in wounds, of bacteria which might otherwise be disposed of by the tis: animal fluids, may be mentioned strangulation of masses of tis: by ligature, the presence of foreign bodies, interference with the circulation from undue pressure and tension, ete. IMMUNITY. 29 ACTION OF BACTERIA AND THEIR PRODUCTS IN THE BODY. Micro-organisms induce their effects in several ways, but chiefly by their presence in the tissues and by the development of their poisonous products, which either affect the physiologic activity of the cell or kill the cell outright. These poisonous products act in varying degree, generally or locally, according to the nature aud quantity of the product formed. Such toxic substances become diffused through the system, and the clinical manifestation of their effec is shown by the occurrence of fever, disturbances in the functions of the respiratory and nervous systems, etc. In some cases changes are found locally, in the tissues directly involved. The general effect: of Lacterial poisons may be so slight as to be regarded of little importance, as in the case of a local inflamma- tion ; or they may be very intense, as in tetanus and diphtheria. In diseases like tetanus and diphtheria it is usually only in the local lesion that the bacilli are found ; and the profound systemic intoxication is due to absorption of the highly toxic products from the local lesion. Whenever there is a widespread distribution of pathogenic bac- teria in the blood the condition is designated septicemia ; and if associated with multiple foci of pus-formation, the term pyemia is applied. The body which is already the seat of infectious dixease is much more susceptible to invasion by other bacteria; thus mixed or concurrent infections are often present. Individuals the victims of long-standing chronic diseases, such as those of the heart, lungs, kidneys, and liver, often succumb to infectious dis- eases of one kind or another. The term terminal infection has been applied by Osler to these infectious diseases. IMMUNITY. Immunity is characterized by resistance to infection or its effects. The absence or loss of this capacity is known as auaceptibility, Immunity from an infectious disease may be hereditary, or it may be aequired, either by an attack of the disease from which the indi- vidual has recovered—natural immunization—or by the introduc- tion into the body of something which diminishes susceptibility — artificial immunization. Acquired immunity may be transmitted from parent to offspring. Many of the infectious diseases confer greater or lesser immun- ity to subsequent attacks of the same disease, although there are exceptions to this rule. A previous attack of erysipelas renders one more susceptible to subsequent infection with the strepto- coceus. 2) INPRCTION CONSIDERED [¥ (13 $7R:: C4 RELSTIONS. Artitieal immonization is generate aeremrished Ee making the teedy-tiewnes tolerant 6) tne preseore of hueteria or their poiwms. This may be dene by the inoraiecie nf amenuated jms of by the inorelnets a of cueir pine. The vame resnit may be ootained ty inom ehie toe beedeiaids from an already immnne indiviinal” Ic & mc Procite te determine t what extent the ie immnnizatinn esferted is ee Is some case From the stmig of infertioa it & ences are evidentiy at piay in ena” It has clearly been shown that the destrietivg of bucteria may in part be broaght abet ty the neers acd ccker meselernal cells, which when the- enzamd are mudd poarest In the bedy-flnids there are al-y certain al eminecs ingrelients which have well-marked bactertidal po perties. A number of theories bave been advaceed to explain the esen- tial nature of immunity. They may be erected inc two el: the hxmorcl, which attributes imriunity w extrac: the body ; and the erf/Jir, which assumes that