Jawetz Melnick & Adelbergs Medical Microbiology 28 E
As all the prior editions of this textbook before, the twenty-eighth edition of Jawetz, Melnick, & Adelberg’s Medical Microbiology remains true to the goals of the first edition published in 1954, which is to “to provide a brief, accurate and up-to-date presentation of those aspects of medical microbiology that are of particular significance to the fields of clinical infections and chemotherapy.”
For the twenty-seventh edition, under the authorship of Dr. Karen Carroll, all chapters had been extensively revised, reflecting the tremendous expansion of medical knowledge afforded by molecular mechanisms and diagnostics, advances in our understanding of microbial pathogenesis, and the discovery of novel pathogens. While Dr. Carroll decided to step down as an author and contributor for this new edition, the remaining authors would like to express their gratitude for her leadership and contributions to the previous, greatly expanded edition. For the 28th edition, Chapter 47, “Principles of Diagnostic Medical Microbiology,” and Chapter 48, “Cases and Clinical Correlations,” were again updated to reflect the continued expansion in laboratory diagnostics as well as new antimicrobial therapies in the treatment of infectious diseases.
Chapter 48 was specifically updated to reflect clinically important and currently emerging infectious disease cases.
New to this edition are Peter Hotez, MD, PhD, Rojelio Mejia, MD, and Stefan Riedel, MD, PhD, D(ABMM). Dr. Hotez is the Dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston, TX, and is a Professor of Pediatrics, Molecular Virology and Microbiology; he brings extensive expertise in parasitology. Dr. Mejia is an Assistant Professor in the Department of Pediatrics, Section of Tropical Medicine, at the National School of Tropical Medicine, Baylor College of Medicine in Houston, TX. Dr. Riedel is the Associate Medical Director of the Clinical Microbiology Laboratories at Beth Israel Deaconess Medical Center in Boston, MA, and holds the academic rank of Associate Professor of Pathology at Harvard Medical School. Following Dr. Carroll’s departure as an author and contributor to this textbook, Dr. Riedel assumed the role as Editor-in-Chief for this revised, 28th edition of the textbook.
The authors hope that the changes to this current edition will continue to be helpful to the student of microbiology and infectious diseases.
Microbiology is the study of microorganisms, a large and diverse group of microscopic organisms that exist as single cells or cell clusters; it also includes viruses, which are microscopic but not cellular. Microorganisms have a tremendous impact on all life and the physical and chemical makeup of our planet. They are responsible for cycling the chemical elements essential for life, including carbon, nitrogen, sulfur, hydrogen, and oxygen; more photosynthesis is carried out by microorganisms than by green plants. Furthermore, there are 100 million times as many bacteria in the oceans (13 × 1028) as there are stars in the known universe. The rate of viral infections in the oceans is about 1 × 1023 infections per second, and these infections remove 20–40% of all bacterial cells each day. It has been estimated that 5 × 1030 microbial cells exist on earth; excluding cellulose, these cells constitute about 90% of the biomass of the entire biosphere. Humans also have an intimate relationship with microorganisms; 50–60% of the cells in our bodies are microbes (see Chapter 10). The bacteria present in the average human gut weigh about 1 kg, and a human adult will excrete his or her own weight in fecal bacteria each year. The number of genes contained within this gut flora outnumber that contained within our genome by 150-fold; even in our own genome, 8% of the DNA is derived from remnants of viral genomes.
BIOLOGIC PRINCIPLES ILLUSTRATED BY MICROBIOLOGY
Nowhere is biologic diversity demonstrated more dramatically than by microorganisms, cells, or viruses that are not directly visible to the unaided eye. In form and function, be t biochemical property or genetic mechanism, analysis of microorganisms takes us to the limits of biologic understanding. Thus, the need for originality—one test of the merit of a scientific hypothesis—can be fully met in microbiology. A useful hypothesis should provide a basis for generalization, and microbial diversity provides an arena in which this challenge is ever present.
Prediction, the practical outgrowth of science, is a product created by a blend of technique and theory. Biochemistry, molecular biology, and genetics provide the tools required for analysis of microorganisms. Microbiology, in turn, extends the horizons of these scientific disciplines. A biologist might describe such an exchange as mutualism, that is, one that benefits all contributing parties. Lichens are an example of microbial mutualism. Lichens consist of a fungus and phototropic partner, either an alga (a eukaryote) or a cyanobacterium (a prokaryote) (Figure 1-1). The phototro-pic component is the primary producer, and the fungus provides the phototroph with an anchor and protection from the elements. In biology, mutualism is called symbiosis, a continuing association of different organisms. If the exchange operates primarily to the benefit of one party, the association is described as parasitism, a relationship in which a host provides the primary benefit to the parasite. Isolation and char-acterization of a parasite—such as a pathogenic bacterium or virus—often require effective mimicry in the laboratory of the growth environment provided by host cells. This demand sometimes represents a major challenge to investigators.
The terms mutualism, symbiosis, and parasitism relate to the science of ecology, and the principles of environmental biology are implicit in microbiology. Microorganisms are the products of evolution, the biologic consequence of natural selection operating on a vast array of genetically diverse organisms. It is useful to keep the complexity of natural history in mind before generalizing about microorganisms, the most heterogeneous subset of all living creatures.
A major biologic division separates the eukaryotes, organisms containing a membrane-bound nucleus from pro-karyotes, organisms in which DNA is not physically separated from the cytoplasm. As described in this chapter and in Chapter 2, further major distinctions can be made between eukaryotes and prokaryotes. Eukaryotes, for example, are distinguished by their relatively large size and by the presence of specialized membrane-bound organelles such as mitochondria.
As described more fully later in this chapter, eukary-otic microorganisms—or, phylogenetically speaking, the Eukarya—are unified by their distinct cell structure and phylogenetic history. Among the groups of eukaryotic microorganisms are the algae, the protozoa, the fungi, and the slime molds. A class of microorganisms that share characteristics common to both prokaryotes and eukaryotes are the archae-bacteria and are described in Chapter 3.
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