Lactobacillary replacement of the flora of the adult

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lactobacillary replacement of the flora of the adult colon does not take place so easily, there have been some successes with capsules containing lyophilized bacteria. In some studies, administration of preparations containing a particular strain of Lactobacillus ( L rhamnosus strain GG , LGG) has reduced the duration of rotavirus diarrhea in children and prevented relapses of antibiotic-associated diarrhea caused by C difficile . Infectious Disease Epidemiology Pathogenesis Immunity Clinical Aspects of Infectious Disease Manifestations Diagnosis Treatment Prevention Summary Of the thousands of species of viruses, bacteria, fungi, and parasites, only a tiny portion is involved in disease of any kind. These are called pathogens . There are plant pathogens, animal pathogens, and fish pathogens, as well as the subject of this book, human pathogens. Among pathogens, there are degrees of potency called virulence , which sometimes makes the dividing line between benign and virulent microorganisms difficult to draw. Other pathogens are virtually always associated with disease of varying severity. Yersinia pestis, the cause of plague, causes fulminant disease and death in 50% to 75% of persons who come in contact with it. It is highly virulent. Understanding the basis of these differences in virulence is a fundamental goal of this book. The better that students of medicine understand how a pathogen causes disease, the better they will be prepared to intervene and help their patients. For any pathogen the basic aspects of how it interacts with the host to produce disease can be expressed in terms of its epidemiology, pathogenesis, and immunity. Usually our knowledge of one or more of these topics is incomplete. It is the task of the physician to relate these topics to the clinical aspects of disease and be prepared for new developments which clarify, or in some cases, alter them. We do not know everything, and not all of what we believe we know is correct. Epidemiology Epidemiology is the "who, what, when, and where" of infectious diseases. The power of the science of epidemiology was first demonstrated by Semmelweis, who by careful data analysis alone determined how streptococcal puerperal fever is transmitted. He even devised a means to prevent transmission (ie, handwashing) decades before the organism itself was discovered. Since then, each organism has built its own profile of vital statistics. Some agents are transmitted by air, others by food, and others by insects; some spread by the person-to-person route. Figure 1–5 presents some of the variables in this regard. Some agents occur worldwide, and others only in certain geographic locations or ecologic circumstances. Knowing how an organism gains access to its victim and spreads is crucial to understanding the disease.
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