Diagnostic medical microbiology is concerned with the etiologic diagnosis of infection. Laboratory procedures used in the diagnosis of infectious disease in humans include the following: ++ Morphologic identification of the agent in stains of specimens or sections of tissues (light and electron microscopy). Detection of the agent in patient specimens by antigen testing (latex agglutination, enzyme immunoassay, etc) or nucleic acid testing (nucleic acid hybridization, polymerase chain reaction [PCR], sequencing, etc). Culture isolation and identification of the agent. Susceptibility testing of the agent by culture or nucleic acid methods, where appropriate.

ungi are eukaryotes with a higher level of biologic complexity than bacteria. Fungi may be unicellular or may differentiate and become multicellular by the development of long, branching filaments. They lack the chlorophyll of plants and therefore need to acquire nutrients from the external environment. The diseases caused by fungi are called mycoses. These infections vary greatly in their manifestations but tend to present with subacute or chronic features, often relapsing over time. Acute disease, such as that produced by many viruses and bacteria, is less common with fungal infections. ++ ❋ Fungal cell organization is eukaryotic +++ STRUCTURE ++ The fungal cell has many typical eukaryotic features, including a nucleus with a nucleolus, nuclear membrane, and linear

ECHANISMS OF ACTION OF ANTIMICROBIAL DRUGS ++ Antimicrobial drugs act in one of several ways: by selective toxicity, by inhibition of cell membrane synthesis and function, by inhibition of protein synthesis, or by inhibition of nucleic acid synthesis. +++ SELECTIVE TOXICITY ++ An ideal antimicrobial agent exhibits selective toxicity, which means that the drug is harmful to a pathogen without being harmful to the host. Often, selective toxicity is relative rather than absolute; this implies that a drug in a concentration tolerated by the host may damage an infecting microorganism.

The non–spore-forming Gram-positive bacilli are a diverse group of aerobic and anaerobic bacteria. This chapter focuses on the aerobic members of this group. The anaerobic, non–spore-forming Gram-positive bacilli such as Propionibacterium species and Actinomyces species are discussed in Chapter 21 on anaerobic infections. Specific genera of both groups, namely, Corynebacterium species and Propionibacterium species, are members of the normal microbiota of skin and mucous membranes of humans and, as such, are frequently contaminants of clinical specimens submitted for diagnostic evaluation. However, among the aerobic Gram-positive bacilli are significant pathogens such as Corynebacterium diphtheriae, an organism that produces a powerful exotoxin that causes diphtheria in humans, and Mycobacterium tuberculosis (see Chapter 23), the causative agent of tuberculosis. Listeria monocytogenes and Erysipelothrix rhusiopathiae are primarily found in animals and occasionally cause severe disease in humans. Nocardia and Rhodococcus species are found in the soil and are significant pathogens among immunocompromised patients.

The Gram-positive spore-forming bacilli are the Bacillus and Clostridium species. These bacilli are ubiquitous, and because they form spores, they can survive in the environment for many years. Bacillus species are aerobes, and the Clostridium species are anaerobes (see also Chapter 21). ++ Of the many species of Bacillus and related genera, most do not cause disease and are not well characterized in medical microbiology. There are a few species, however, that cause important diseases in humans. Anthrax, a classical disease in the history of microbiology, is caused by Bacillus anthracis. Anthrax remains an important disease of animals and occasionally of humans. Because of its potent toxins, B. anthracis is a major potential agent of bioterrorism and biologic warfare. B. cereus causes food poisoning and occasionally eye or other localized infections. ++ The genus Clostridium is extremely heterogeneous, and more than 200 species have been described. The list of pathogenic organisms, as well as novel species isolated from human feces whose pathogenic potential remains undetermined, continues to grow. Clostridia cause several important toxin-mediated diseases, including tetanus (Clostridium tetani), botulism (C. botulinum), gas gangrene (C. perfringens), and antibiotic-associated diarrhea and pseudomembranous colitis (C. difficile). Other clostridia are also found in mixed anaerobic infections in humans (se

The human body harbors a variety of microorganisms that can be arranged into two groups: (1) the resident microbiota consists of relatively fixed types of microorganisms regularly found in a given area at a given age; if disturbed, it promptly reestablishes itself; and (2) the transient microbiota consists of nonpathogenic or potentially pathogenic microorganisms that inhabit body sites for hours, days, or weeks. The transient microbiota is derived from the environment, does not produce disease, ...

pathogenesis of bacterial infection includes initiation of the infectious process and the mechanisms that lead to the development of signs and symptoms of disease. The biochemical, structural, and genetic factors that play important roles in bacterial pathogenesis are introduced in this chapter and may be revisited in the organism-specific sections. Characteristics of bacteria that are pathogens include transmissibility, adherence to host cells, persistence, invasion of host cells and tissues, toxigenicity, and the ability to evade or survive the host’s immune system. Resistance to antimicrobials and disinfectants can also contribute to virulence, or an organism’s capacity to cause disease. Many infections caused by bacteria that are commonly considered to be pathogens are inapparent or asymptomatic. Disease occurs if the bacteria or immunologic reactions to their presence cause sufficient harm to the person.

esponse generated against a potential pathogen is called an immune response. The first line of defense, which is nonspecific to the invading pathogen, is rapidly mobilized at the initial site of infection but lacks immunologic memory and is called innate immunity. The second defense system is called adaptive immunity. It is specific for the pathogen and confers protective immunity to reinfection with that pathogen. Adaptive immunity can specifically recognize and destroy the pathogen because lymphocytes carry specialized cellular receptors and produce specific antibodies. A protein that is produced in response to a particular pathogen is called the antibody, and the substance that induces the production of antibodies is called the antigen. In summary, the innate immune response is effective and critical in eliminating most pathogens. However, if this initial mechanism fails, the adaptive immune response is induced that specifically confronts the pathogen and establishes immunity to that invading pathogen. Hence, both systems interact and collaborate to achieve the final goal of destroying the pathogen. +++ INNATE IMMUNITY ++ Innate immunity is an immediate response to a pathogen that does not confer long-lasting protective immunity. It is a nonspecific defense system and includes barriers to infectious agents, such as the skin (epithelium) and mucous membranes. It also includes many immune components important in the adaptive immune response, including phagocytic cells, natural killer (NK) cells, toll-like receptors (TLRs), cytokines, and complement. +++ Barrier Functions of Innate Immunity ++ Few microorganisms can penetrate body surfaces. These surfaces have an epithelial cell layer as their barrier, which is present in the skin, airways, gastrointestinal (GI) tract, ... Your Access profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth Pop-up div Successfully Displayed This div only appears when the trigger link is hovered over. Otherwise it is hidden from view. Please Wait AccessMedicine Books Library Updates Quick Reference Quick Medical Diagnosis & Treatment 2 Minute Medicine® DDx Diagnostic Tests Goodman & Gilman’s : FDA Approvals Huppert's Notes Guidelines — Primary Care Infographics Drugs Multimedia Auscultation Classroom Big Picture Physiology Videos Diagnostic and Imaging Studies Harrison's Pathophysiology Animations Human Anatomy Modules Lectures Patient Interview Patient Safety Modules Pharmacology Physical Exam POCUS Pearls Podcasts Procedural Videos Cases Case Files® - Preview Clinical Neuroanatomy Cases Critical Concept Mastery Series Family Medicine Board Review Fluid/Electrolyte and Acid-Base Cases G&G Pharm Cases Harrison’s Visual Case Challenge Internal Medicine Cases Medical Microbiology Cases Pathophysiology Cases Principles of Rehabilitation Medicine Case-Based Board Review Vanderbilt IM/Peds Curriculum Study Tools Review Questions Clerkship Topics Flashcards Patient Ed About AccessMedicine Advisory Board Hospital Corner For Instructors McGraw Hill Medical Sites AccessAnesthesiology AccessAPN Accessartmed AccessBiomedical Science AccessCardiology AccessDermatologyDxRx AccessEmergency Medicine AccessHemOnc AccessMedicina AccessMedicine AccessNeurology AccessObGyn AccessPediatrics AccessPharmacy AccessPhysiotherapy AccessSurgery Case Files Collection Clinical Sports Medicine Collection F.A. Davis AT Collection F.A. Davis PT Collection JAMAevidence Murtagh Collection OMMBID Pharmacotherapy Principles & Practice Support Training & Support Contact Us Submit Feedback Subscribe Institutional Subscriptions Individual Subscriptions McGraw Hill Apple store Google Play See Terms Copyright © McGraw HillAll rights reserved.Your IP address is 102.68.76.231 Terms of Use   •  Privacy Policy   •  Notice   •  Accessibility   •  Browser Support Silverchair Back To Top .index .dynamic-widget-module.flex-container .text-wrap { padding: 0; } .index .dynamic-widget-module.flex-container > .dynamic-widget-inner-wrap { padding: 1rem; } .index .dynamic-widget-module.flex-container>.dynamic-widget-inner-wrap h2 { position: relative; top: 0; } .index .dynamic-widget-module.flex-container>.dynamic-widget-inner-wrap .item { padding: 0; } .index .dynamic-widget-module.flex-container>.dynamic-widget-inner-wrap [class*='ssHomeWatch'] h2 { position: absolute; top: -2rem; } .index .dynamic-widget-module.flex-container>.dynamic-widget-inner-wrap [class*='ssHomeLearn'] h2 { position: absolute; top: -2rem; } .index .dynamic-widget-module.flex-container>.dynamic-widget-inner-wrap [class*='ssExtrabox'] h2 { position: absolute; top: -2rem; } /*MHGEN-8550*/ .cmpl_iframe_div.cadmore-player-wrap { padding-top: 130%; } .pg_umbrella-main .carousel-item { width: auto; } .pg_umbrella-main .carousel-item img { max-height: 350px; } .pg_umbrella-main .widget-instance-ssUmbrellaAccessCards img { max-height: 300px; } .widget-SitesDropdown .site-name { margin-top: .5rem !important; } .widget-SitesDropdown .site-name a, .user-services a { color: #333 !important; font-weight: bold; text-transform: uppercase; } #micrositeHeader_liAccessMedicina a { line-height: 52px; } //Track Audio Only for JE $('.dropdown.audio a').click(function (e) { //DO Tracking DoClientTrackingForMGH($(this), 'https://books.mcgraw-hill.com/podcast/jamaevidence/'); }); $(function () { $("#microsite-footer li.users-guides-to-the-medical-literature a").each(function () { var getContent = $(this).text(); var newString = getContent.replace('to the Medical Literature', '<br />to the Medical Literature'); $(this).html(newString); }); $('.for-librarians').find('a').removeClass().attr('target', '_blank'); }); //<![CDATA[ var Page_Validators = new Array(document.getElementById("micrositeHeader_RequiredFieldValidator1")); //]]> //<![CDATA[ var micrositeHeader_RequiredFieldValidator1 = document.all ? document.all["micrositeHeader_RequiredFieldValidator1"] : document.getElementById("micrositeHeader_RequiredFieldValidator1"); micrositeHeader_RequiredFieldValidator1.controltovalidate = "txtSearchTerm"; micrositeHeader_RequiredFieldValidator1.errormessage = "Please Enter a Search Term"; micrositeHeader_RequiredFieldValidator1.validationGroup = "headersearch"; micrositeHeader_RequiredFieldValidator1.evaluationfunction = "RequiredFieldValidatorEvaluateIsValid"; micrositeHeader_RequiredFieldValidator1.initialvalue = ""; //]]> //<![CDATA[ var Page_ValidationActive = false; if (typeof(ValidatorOnLoad) == "function") { ValidatorOnLoad(); } function ValidatorOnSubmit() { if (Page_ValidationActive) { return ValidatorCommonOnSubmit(); } else { return true; } } document.getElementById('micrositeHeader_RequiredFieldValidator1').dispose = function() { Array.remove(Page_Validators, document.getElementById('micrositeHeader_RequiredFieldValidator1')); } //]]> (function(){function b(){!1===c&&(c=!0,Munchkin.init("303-FKF-702"))}var c=!1,a=document.createElement("script");a.type="text/javascript";a.async=!0;a.src="//munchkin.marketo.net/munchkin.js";a.onreadystatechange=function(){"complete"!=this.readyState&&"loaded"!=this.readyState||b()};a.onload=b;document.getElementsByTagName("head")[0].appendChild(a)})(); !function(b,e,f,g,a,c,d){b.fbq||(a=b.fbq=function(){a.callMethod?a.callMethod.apply(a,arguments):a.queue.push(arguments)},b._fbq||(b._fbq=a),a.push=a,a.loaded=!0,a.version="2.0",a.queue=[],c=e.createElement(f),c.async=!0,c.src=g,d=e.getElementsByTagName(f)[0],d.parentNode.insertBefore(c,d))}(window,document,"script","https://connect.facebook.net/en_US/fbevents.js");fbq("init","472393460782729");fbq("track","PageView"); <img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=472393460782729&amp;ev=PageView&amp;noscript=1"> !function(b,e,f,g,a,c,d){b.fbq||(a=b.fbq=function(){a.callMethod?a.callMethod.apply(a,arguments):a.queue.push(arguments)},b._fbq||(b._fbq=a),a.push=a,a.loaded=!0,a.version="2.0",a.queue=[],c=e.createElement(f),c.async=!0,c.src=g,d=e.getElementsByTagName(f)[0],d.parentNode.insertBefore(c,d))}(window,document,"script","https://connect.facebook.net/en_US/fbevents.js");fbq("init","491404515608644");fbq("track","PageView"); <img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=491404515608644&amp;ev=PageView&amp;noscript=1"> !function(b,e,f,g,a,c,d){b.saq||(a=b.saq=function(){a.callMethod?a.callMethod.apply(a,arguments):a.queue.push(arguments)},b._saq||(b._saq=a),a.push=a,a.loaded=!0,a.version="1.0",a.queue=[],c=e.createElement(f),c.async=!0,c.src=g,d=e.getElementsByTagName(f)[0],d.parentNode.insertBefore(c,d))}(window,document,"script","https://tags.srv.stackadapt.com/events.js");saq("ts","gzdqW7I-rc7jNTBJ8xilNw"); Display.Common.DefaultUpdateTarget("ucDefaultUpdateTarget", asdfasdf) $(function () { // hide right widget column for front matter if (0 == 1) { $('#toolbox-widgets').hide(); } if ($('.emptyBookmarked').length) { $('.view-favorites').css('display', 'none'); $('.no-filtered-favorites').css('display', 'inline'); } else { $('.view-favorites').css('display', 'inline'); $('.no-filtered-favorites').css('display', 'none'); } // expand main content column for guideline book if (0 == 1) { if (String("RiedMed28").valueOf() == "guid") { $('.row').addClass("row-fluid").removeClass("row"); $('article').removeClass("span6").addClass("span12").show(); $('#content-navbar').removeClass("span6").addClass("span12").show(); } else { // others, just expand to the right column but leave the section nav to the left $('article').removeClass("span6").addClass("span9").show(); $('#content-navbar').removeClass("span6").addClass("span9").show(); } } if ("False" == "True") { $('.searchTextBook').hide(); } $('article').show(); $('#content-navbar').show(); scrollToHash(); getFavoriteStar(); window.addEventListener("SCM.AddFavorites.Complete", function (e) { $('.widget-AddFavorites').each(function () { $(this).addClass('rs_skip_always'); $(this).addClass('rs_preserve') }); }); $(document).ajaxComplete(function () { var cmeClinicalQuestionElement = $('.widget-CmeClinicalQuestions'); if (cmeClinicalQuestionElement.length) { AssigningToCliniclaQUeries(); } }); }); var sectionID = utility.getUrlParams('sectionid'); addRecentlyViewed(sectionID, "section", false); <div class="loader"> <img src="Images/spinnerLarge.gif" /> </div> {{if d.glossaryTerm }} <div class="glossaryTerm">{{html d.glossaryTerm}}</div> <div class="glossaryDefinition">{{html d.glossaryDefinition}}</div> <div class="bordered-bottom"> <a href="/SearchResults.aspx?q={{html d.glossarySearchTerm}}">Run a search on this term</a> </div> <div>{{html d.glossarySource}}</div> {{else}} <div class="msg_error">No glossary found!</div> {{/if}} { "showHighlights": false } This site uses cookies to provide, maintain and improve your experience. MH Privacy Center Close

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.