Some factors that increase emergence or reemergence of infectious pathogens include: ++ Human and animal demographics and population movement with intrusion into new habitats (particularly tropical forests) Irrigation, especially primitive irrigation systems, which fail to control arthropods and enteric organisms Uncontrolled urbanization, with vector populations breeding in stagnant water Increased international commerce and travel with contact or transport of vectors and pathogens (globalization) Breakdown in public health measures, including sanitation, vector control, immunization programs related to social unrest, civil wars, and major natural disasters Ecological changes, including global climate change and deforestation, with farmers and their animals exposed to new arthropods, floods, and drought Microbial evolution whether related to indiscriminate use of anti-infective ...

EMERGING INFECTIOUS DISEASES ++ An emerging disease is an infectious disease whose incidence has increased in the past two decades and/or that threatens to increase soon. Emerging infectious diseases reflect the arrival of a new pathogen (newly emerging) or an old pathogen that is increasing in incidence, clinical or laboratory characteristics, or geographic range (re-emerging or resurging). An unusual third group is “deliberately emerging” infections, such as anthrax bioterrorism. The appearance of novel coronaviruses (eg, the severe acute respiratory syndrome [SARS] coronavirus and now SARS-CoV-2 [the cause of COVID-19]) are examples of new pathogens, multidrug-resistant Mycobacterium tuberculosis represents an old pathogen with new characteristics, and cholera and Zika in the Americas are examples of old pathogens with a new geographic range (Asia to South America). New methods of detection (eg, molecular) and surveillance (eg, global) have greatly improved our ability to detect and characterize emerging and reemerging infectious diseases. The fundamental methodologies of molecular epidemiology are described in Chapter 4, and their specific applications are discussed in many other chapters throughout this book. ++ Some factors that increase emergence or reemergence of infectious pathogens include: ++ Human and animal demographics and population movement with intrusion into new habitats (particularly tropical forests) Irrigation, especially primitive irrigation systems, which fail to control arthropods and enteric organisms Uncontrolled urbanization, with vector populations breeding in stagnant water Increased international commerce and travel with contact or transport of vectors and pathogens (globalization) Breakdown in public health measures, including sanitation, vector control, immunization programs related to social unrest, civil wars, and major natural disasters Ecological changes, including global climate change and deforestation, with farmers and their animals exposed to new arthropods, floods, and drought Microbial evolution whether related to indiscriminate use of anti-infective ...

Clinical diagnosis guides approach to etiologic diagnosis ++ Behind every clinical specimen submitted to the diagnostic laboratory should be a question. Does my patient have, can I exclude, does the result confirm the disease? Answers to such questions depend on understanding, whether articulated specifically or not, the characteristics of the tests ordered and performed. These characteristics are sensitivity (the test’s ability to rule out [snout] a disease because there are few false-negative results and thus fewer cases missed) and specificity (the test’s ability to rule in [spin] or confirm an etiology because there are few false-positive results). Ideally, a test would have both excellent sensitivity and specificity, but traditional methods often involved a trade-off between the two, which only emphasizes the need to know the clinical question or reason for ordering a test. Molecular methods, however, tend to have improved sensitivity as well as specificity, which is dramatically so for viral etiologic diagnoses.

Sections Download Chapter PDF Share Email Twitter Facebook Linkedin Reddit Get Citation .logoBrand img { width: 280px; } Citation Disclaimer: These citations have been automatically generated based on the information we have and it may not be 100% accurate. Please consult the latest official manual style if you have any questions regarding the format accuracy. AMA Citation Principles of Laboratory Diagnosis of Infectious Diseases. In: Ryan KJ. Ryan K.J.(Ed.),Ed. Kenneth J. Ryan.eds. Sherris & Ryan's Medical Microbiology, 8e. McGraw Hill; 2022. Accessed September 30, 2023. https://accessmedicine.mhmedical.com/content.aspx?bookid=3107&sectionid=260922674APA Citation Principles of laboratory diagnosis of infectious diseases. Ryan KJ. Ryan K.J.(Ed.),Ed. Kenneth J. Ryan. (2022). Sherris & Ryan's Medical Microbiology, 8e. McGraw Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=3107&sectionid=260922674MLA Citation "Principles of Laboratory Diagnosis of Infectious Diseases." Sherris & Ryan's Medical Microbiology, 8e Ryan KJ. Ryan K.J.(Ed.),Ed. Kenneth J. Ryan. McGraw Hill, 2022, https://accessmedicine.mhmedical.com/content.aspx?bookid=3107&sectionid=260922674. Download citation file: RIS (Zotero) EndNote BibTex Medlars ProCite RefWorks Reference Manager Mendeley © Copyright Tools Search Book Annotate Clip Autosuggest Results Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ INTRODUCTION ++ The diagnosis of a microbial infection begins with an assessment of the clinical and epidemiologic features and formulation of a diagnostic hypothesis. Anatomic localization of the infection depends on physical and radiologic findings (eg, right lower lobe pneumonia, subphrenic abscess). This clinical diagnosis suggests a number of possible etiologic agents based on knowledge of infectious syndromes and their courses. The specific cause or etiologic diagnosis is then established by the application of methods described in this chapter. A combination of science and art on the part of both the clinician and laboratory worker is required: The clinician must select the appropriate tests and specimens to be processed and, where appropriate, suggest the suspected etiologic agents to the laboratory. The laboratory scientist must use the methods that will demonstrate the probable agents and be prepared to explore other possibilities suggested by the clinical situation or by the findings of the laboratory examinations. The best results are obtained when communication between the clinician and laboratory is optimal.

❋ Pasteurization uses heat to kill vegetative forms of bacteria ++ Disinfection is a less precise term. It implies the destruction of pathogenic microorganisms by processes that fail to meet the criteria for sterilization. Pasteurization is a form of disinfection, but the term is most commonly applied to the use of liquid chemical agents known as disinfectants, which usually have some degree of selectivity. Bacterial spores, organisms with waxy coats (eg, mycobacteria), and some viruses may show considerable resistance to the common disinfectants. Antiseptics are disinfecting agents that can be used on body surfaces, such as the skin or vaginal tract, to reduce the numbers of pathogenic agents in the local microbiota. They have lower toxicity than disinfectants used environmentally, but are usually less active in killing vegetative organisms. ...

bsence of growth does not necessarily indicate sterility ++ Sterilization is an absolute term. It means complete killing, or removal, of all living organisms from a particular location or material. It can be accomplished by incineration, nondestructive heat treatment, certain gases, exposure to ionizing radiation, some liquid chemicals, and filtration.

Death/killing as it relates to microbial organisms is defined in terms of how we detect them in culture. Operationally, it is a loss of ability to multiply under any known conditions. This is complicated by the fact that organisms that appear to be irreversibly inactivated may, sometimes, recover when appropriately treated. For example, ultraviolet (UV) irradiation of bacteria can result in the formation of thymine dimers in the DNA with loss of ability to replicate.

Chapter 3: Sterilization, Disinfection, and Infection Control Sections Download Chapter PDF Share Email Twitter Facebook Linkedin Reddit Get Citation .logoBrand img { width: 280px; } Citation Disclaimer: These citations have been automatically generated based on the information we have and it may not be 100% accurate. Please consult the latest official manual style if you have any questions regarding the format accuracy. AMA Citation Sterilization, Disinfection, and Infection Control. In: Ryan KJ. Ryan K.J.(Ed.),Ed. Kenneth J. Ryan.eds. Sherris & Ryan's Medical Microbiology, 8e. McGraw Hill; 2022. Accessed September 30, 2023. https://accessmedicine.mhmedical.com/content.aspx?bookid=3107&sectionid=260922529APA Citation Sterilization, disinfection, and infection control. Ryan KJ. Ryan K.J.(Ed.),Ed. Kenneth J. Ryan. (2022). Sherris & Ryan's Medical Microbiology, 8e. McGraw Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=3107&sectionid=260922529MLA Citation "Sterilization, Disinfection, and Infection Control." Sherris & Ryan's Medical Microbiology, 8e Ryan KJ. Ryan K.J.(Ed.),Ed. Kenneth J. Ryan. McGraw Hill, 2022, https://accessmedicine.mhmedical.com/content.aspx?bookid=3107&sectionid=260922529. Download citation file: RIS (Zotero) EndNote BibTex Medlars ProCite RefWorks Reference Manager Mendeley © Copyright Tools Search Book Annotate Clip Autosuggest Results Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ INTRODUCTION ++ From the time of debates about the germ theory of disease, killing microbes before they reach patients has been a major strategy for preventing infection. In fact, Ignaz Semmelweis successfully applied disinfection principles decades before bacteria were first isolated. This chapter discusses the most important methods used for this purpose in modern medical practice. Understanding how these methods work has become of increasing importance in an environment that includes immunocompromised patients, transplantation, indwelling devices, and Covid-19.

Human blood cells. Stem cells in the bone marrow divide to form two blood cell lineages: (1) the lymphoid stem cell gives rise to B cells that become antibody-secreting plasma cells, T cells that become activated T cells, and natural killer cells. (2) The common myeloid progenitor cell gives rise to granulocytes and monocytes that give rise to macrophages and dendritic cells. (Reproduced with permission from Willey JM: Prescott, Harley, & Klein’s Microbiology, 7th ed. New York, NY: McGraw Hill; 2008.)

he immune response to infection is presented as two major components—innate immunity and adaptive immunity. The primary effectors of both are cells that are members of the white blood cell series derived from hematopoietic stem cells in the bone marrow (Figure 2–1). Innate immunity includes the role of physical, cellular, and chemical systems that are in place and that respond to all aspects of “foreignness.” These include mucosal barriers, phagocytic cells, and the action of circulating glycoproteins such as complement. The adaptive side is sometimes called specific immunity because it has the ability to develop new responses that are highly specific to molecular components of infectious agents, called antigens. These encounters trigger the development of new cellular responses and production of circulating antibodies, which have a component of memory if the invader returns. Artificially creating this memory is, of course, the goal of vaccines.

NTRODUCTION + Humanity has but three great enemies: fever, famine, and war; of these by far the greatest, by far the most terrible, is fever. —Sir William Osler, 1896* ++ When Sir William Osler, the great physician/humanist, wrote these words, fever (infection) was indeed the scourge of the world. Tuberculosis and other forms of pulmonary infection were the leading causes of premature death among the well-to-do and the less fortunate. The terror was due to the fact that, although some of the causes of infection were being discovered, little could be done to prevent or alter the course of disease. In the 20th century, advances in public sanitation and the development of vaccines and antimicrobial agents changed this (Figure 1–1), but only for the nations that can afford these interventions. As we move through the second decade of the 21st century, the world is divided into countries in which heart attacks, cancer, and stroke have surpassed infection as causes of premature death and those in which

REQUIREMENTS FOR GROWTH ++ Most of the dry weight of microorganisms is organic matter containing the elements carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. In addition, inorganic ions such as potassium, sodium, iron, magnesium, calcium, and chloride are required to facilitate enzymatic catalysis and to maintain chemical gradients across the cell membrane.

Bacteria divide by binary fission, asexual reproduction where a single cell divides giving rise to two cells. Those two cells give rise to a total of four cells and so on. This process of replication requires the acquisition of elements that make up their chemical composition. Nutrients from the environment provide these elements in metabolically accessible forms. In addition, organisms require metabolic energy to synthesize macromolecules and maintain essential chemical gradients across their membranes. Factors that must be controlled during growth include the nutrients, pH, temperature, aeration, salt concentration, and ionic strength of the medium.

Chapter 5: Cultivation of Microorganisms Sections Download Chapter PDF Share Email Twitter Facebook Linkedin Reddit Get Citation .logoBrand img { width: 280px; } Citation Disclaimer: These citations have been automatically generated based on the information we have and it may not be 100% accurate. Please consult the latest official manual style if you have any questions regarding the format accuracy. AMA Citation Cultivation of Microorganisms. In: Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. Riedel S, & Hobden J.A., & Miller S, & Morse S.A., & Mietzner T.A., & Detrick B, & Mitchell T.G., & Sakanari J.A., & Hotez P, & Mejia R(Eds.),Eds. Stefan Riedel, et al.eds. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e. McGraw Hill; 2019. Accessed September 30, 2023. https://accessmedicine.mhmedical.com/content.aspx?bookid=2629&sectionid=217769608APA Citation Cultivation of microorganisms. Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. Riedel S, & Hobden J.A., & Miller S, & Morse S.A., & Mietzner T.A., & Detrick B, & Mitchell T.G., & Sakanari J.A., & Hotez P, & Mejia R(Eds.),Eds. Stefan Riedel, et al. (2019). Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e. McGraw Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=2629&sectionid=217769608MLA Citation "Cultivation of Microorganisms." Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. Riedel S, & Hobden J.A., & Miller S, & Morse S.A., & Mietzner T.A., & Detrick B, & Mitchell T.G., & Sakanari J.A., & Hotez P, & Mejia R(Eds.),Eds. Stefan Riedel, et al. McGraw Hill, 2019, https://accessmedicine.mhmedical.com/content.aspx?bookid=2629&sectionid=217769608. Download citation file: RIS (Zotero) EndNote BibTex Medlars ProCite RefWorks Reference Manager Mendeley © Copyright Tools Search Book Annotate Clip Autosuggest Results Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ INTRODUCTION ++ Cultivation is the process of propagating organisms by providing the proper environmental conditions. Parasites, bacteria, and viruses all generally require cultivation for detailed study. The field of microbiology has the greatest experience in the cultivation of bacteria and as such, this is the focus of this chapter.

A. Viable Cell Count ++ The viable cell count (Table 4-1) is typically considered the measure of cell concentration. For this, a 1-mL volume is removed from a bacterial suspension and serially diluted 10-fold followed by plating 0.1-mL aliquots on a suitable agar medium. Each single invisible bacterium (or clump of bacteria) will grow into a visible colony that can be counted

The Measurement of Microbial Concentrations ++ Microbial concentrations can be measured in terms of cell concentration (the number of viable cells per unit volume of culture) or of biomass concentration (dry weight of cells per unit volume of culture

THE MEANING OF GROWTH ++ Growth is the orderly increase in the sum of all the components of an organism. The increase in size that results when a cell takes up water or deposits lipid or polysaccharide is not true growth. Cell multiplication is a consequence of binary fission that leads to an increase in the number of single bacteria making up a population, referred to as a culture.

+++ SURVIVAL OF MICROORGANISMS IN THE NATURAL ENVIRONMENT ++ The population of microorganisms in the biosphere remains roughly constant because the growth of microorganisms is balanced by the death of these organisms. The survival of any microbial group within an environmental niche is ultimately influenced by successful competition for nutrients and by maintenance of a pool of all living cells, often composed of human cells and a consortium of different microorganisms (referred to as the microbiome or microbiota). Understanding competition for nutritional resources within a given microenvironment is essential to understanding the growth, survival, and death of bacterial species (also known as physiology). ++ Much of our understanding of microbial physiology has come from the study of isolated cultures grown under optimal conditions in laboratories (nutrient excess). However, most microorganisms compete in the natural environment under nutritional stress

Identification, classification, and nomenclature are three separate but interrelated areas of bacterial taxonomy. Each area is critical to the ultimate goal of accurately studying the infectious diseases and precisely communicating these to others in the field. ++ Identification is the practical use of a classification scheme (1) to isolate and distinguish specific organisms among the mix of complex microbial flora, (2) to verify the authenticity or special properties of a culture in a clinical setting, and (3) to isolate the causative agent of a disease. The latter may lead to the selection of specific pharmacologic treatments directed toward their eradication, a vaccine mitigating their pathology, or a public health measure (eg, handwashing) that prevents further transmission. ++ Identification schemes are not classification schemes, although there may be some superficial similarity. For example, the popular literature has reported Escherichia coli as the causative agent of hemolytic uremic syndrome (HUS) in infants. There are hundreds of different strains that are classified as E. coli but only a few that are associated with HUS. These strains can be “identified” from the many other E. coli strains by antibody reactivity with their O-, H-, and K-antigens, as described in Chapter 2 (eg, E. coli O157:H7). However, they are more broadly classified as a member of the family Enterobacteriaceae. ++ In a microbiologic context, classification is the categorization of organisms into taxonomic groups. Experimental and observational techniques are required for taxonomic classification. This is because biochemical, physiologic, genetic, and morphologic properties are historically necessary for establishing a taxonomic rank. This area of microbiology is necessarily dynamic as the tools continue to evolve (eg, new methods of microscopy, biochemical analysis, and computational nucleic acid biology). ++ Nomenclature refers to the naming of an organism by an established group

TAXONOMY—THE VOCABULARY OF MEDICAL MICROBIOLOGY ++ One has only to peruse the table of contents of this book to appreciate the diversity of medical pathogens that are associated with infectious diseases. It has been estimated that we currently have the capacity to identify a surprisingly small number of the pathogens responsible for causing human disease. In part this is due to our inability to culture or target these organisms using molecular probes. The diversity of even these identifiable pathogens alone is so great that it is important to appreciate the subtleties associated with each infectious agent. The reason for understanding these differences is significant because each infectious agent has specifically adapted to a particular mode(s) of transmission, the capacity to grow in a human host (colonization), and a mechanism(s) to cause disease (pathology

The bright-field microscope is the most commonly used in microbiology courses and consists of two series of lenses (objective and ocular lens), which function together to resolve the image. These microscopes generally employ a 100-power objective lens with a 10-power ocular lens, thus magnifying the specimen 1000 times. Particles 0.2 µm in diameter are therefore magnified to about 0.2 mm and so become clearly visible. Further magnification would give no greater resolution of detail and would reduce the visible area (field). ++ With this microscope, specimens are rendered visible because of the differences in contrast between them and the surrounding medium. Many bacteria are difficult to see well because of their lack of contrast with the surrounding medium. Dyes (stains) can be used to stain cells or their organelles and increase their contrast so that they can be more easily seen in the bright-field microscope. +++ B. Phase-Contrast Microscope ++ The phase-contrast microscope was developed to improve contrast differences between cells and the surrounding medium, making it possible to see living cells without staining them; with bright-field microscopes, killed and stained preparations must be used

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 phototropic 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 ...

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.