Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation ROBERT W. BAUMAN M ICROBIOLOGY ALTERNATE EDITION WITH DISEASES BY BODY SYSTEM Chapter 14 Infection, Infectious Diseases, and Epidemiology
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Symbiosis means “to live together” Describes the relationship between microorganisms and their host 3 types Mutualism Commenalism Parasitism Symbiotic Relationships
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Table 14.1 The Three Types of Symbiotic Relationships
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Also termed normal flora and indigenous microbiota Refers to the organisms that colonize the body’s surfaces without normally causing disease Two types Resident microbiota Transient microbiota Normal Microbiota
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Are a part of the normal microbiota throughout life Most are commensal Resident Microbiota
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Table Resident Microbiota
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Table Resident Microbiota
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Remain in the body for only hours to months before disappearing Found in the same regions as resident microbiota Cannot persist in the body Competition from other microorganisms Elimination by the body’s defenses cells Chemical or physical changes in the body Transient Microbiota
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Development in the womb is generally free of microorganisms (axenic) Microbiota begins to develop during the birthing process Much of ones resident microbiota established during the first months of life Acquisition of Normal Microbiota
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Normal microbiota that can cause disease under certain circumstances Conditions that provide opportunities for pathogens Immune suppression Changes in the normal microbiota- changes in relative abundance of normal microbiota may allow opportunity for a member to thrive and cause disease Introduction of normal microbiota into unusual site in the body Opportunistic Pathogens
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Contamination- the mere presence of microbes in or on the body Infection- results when the organism has evaded the body’s external defenses, multiplied, and become established in the body Contamination versus Infection
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Sites through which pathogens enter the body 4 major types Skin Mucous membranes Placenta Parenteral route Portals of Entry
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Outer layer of packed, dead, skin cells usually acts as a barrier to pathogens Some pathogens can enter through openings or cuts Others enter by burrowing into or digesting the outer layers of skin Skin
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Line the body cavities that are open to the environment Provides a moist, warm environment that is hospitable to pathogens Respiratory tract is the most commonly used site of entry- entry is through the nose, mouth or eyes Pathogens able to survive the acidic pH of the stomach may use the gastrointestinal tract as a route of entry Mucous Membranes
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Table 14.3 Some Pathogens that Cross the Placenta
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Not a true portal of entry but a means by which they can be circumvented Pathogens deposited directly into tissues beneath the skin or mucous membranes Parenteral Route
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Process by which microorganisms attach themselves to cells Required to successfully establish colonies within the host Uses adhesion factors Specialized structures Attachment proteins Adhesion
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Found on viruses (attachment proteins) and many bacteria (adhesins) Surface lipoproteins or glycoproteins, called ligands, that bind host cell receptors Interaction of ligand with host receptor can determine specificity for host cells Ability to change or block the ligand or its receptor can prevent infection Inability to make attachment proteins or adhesins renders the microorganisms avirulent Attachment Proteins
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Infection is the invasion of the host by a pathogen Disease results only if the invading pathogen alters the normal functions of the body Disease is also referred to as morbidity Infection versus Disease
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Symptoms- subjective characteristics of disease felt only by the patient Signs- objective manifestations of disease that can be observed or measured by others Syndrome- group of symptoms and signs that characterize a disease or abnormal condition Asymptomatic, or subclinical, infections lack symptoms but may still have signs of infection Manifestations of Disease:
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Study of the cause of disease Germ theory of disease- disease caused by infections of pathogenic microorganisms Robert Koch developed a set of postulates one must satisfy to prove a particular pathogen causes a particular disease Etiology
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Using Koch’s postulates is not feasible in all cases Some pathogens can’t be cultured in the laboratory Some diseases are caused by a combination of pathogens and other cofactors Ethical considerations prevent applying Koch’s postulates to pathogens that require a human host Difficulties in satisfying Koch’s postulates Diseases that can be caused by more than one pathogen Pathogens that are ignored as potential causes of disease Exceptions to Koch’s Postulates
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Pathogenicity- ability of a microorganism to cause disease Virulence- degree of pathogenicity Virulence factors contribute to an organisms virulence Adhesion factors Extracellular enzymes Toxins Antiphagocytic factors Virulence Factors of Infectious Disease
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Enzymes secreted by the pathogen Dissolve structural chemicals in the body Help pathogen maintain infection, invade further, and avoid body defenses Extracellular Enzymes
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Chemicals produced by the pathogen Harm tissues or trigger host immune responses that cause damage Toxemia refers to toxins in the bloodstream that are carried beyond the site of infection 2 types Exotoxins Endotoxins Toxins
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings A Comparison of Bacterial Exotoxins and Endotoxins Table 14.7
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Certain factors prevent phagocytosis by the host’s phagocytic cells Bacterial capsule Often composed of chemicals found in the body and not recognized as foreign Can be slippery making it difficult for phagocytes to engulf the bacteria Antiphagocytic chemicals Some prevent fusion of lysosome and phagocytic vesicles Leukocidins directly destroy phagocytic white blood cells Antiphagocytic Factors
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Following infection, sequence of events called the disease process occurs Many infectious diseases have five stages following infection The Stages of Infectious Disease
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.10
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Pathogens leave host through portals of exit Movement of Pathogen Out of Host
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.11
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Most pathogens cannot survive long outside of their host Sites where pathogens are maintained as a source of infection are termed reservoirs of infection 3 types of reservoirs Animal reservoir Human carriers Nonliving reservoir Reservoirs of Infection
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Zoonoses- diseases that are naturally spread from their usual animal host to humans Acquire zoonoses through various routes Direct contact with animal or its waste Eating animals Bloodsucking arthropods Humans are usually dead end host to zoonotic pathogens Animal Reservoirs
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Infected individuals who are asymptomatic but infective to others Some individuals will eventually develop illness while others never get sick Human Carriers
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Soil, water, and food can be reservoirs of infection Presence of microorganisms is often due to contamination by feces or urine Nonliving Reservoirs
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Transmission from either a reservoir or portal of exit 3 groups Contact transmission Vehicle transmission Vector transmission Modes of Infectious Disease Transmission
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Table Modes of Disease Transmission
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Many different methods of classification The body system they affect The taxonomic groups of the causative agent Their longevity and severity How they are spread to their host Classification of Infectious Diseases
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Table Terms Used to Classify Infectious Diseases
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Study of where and when diseases occur and how they are transmitted within populations Track occurrence of diseases using two measures Incidence- number of new cases of a disease in a given area during a given period of time Prevalence- number of total cases of a disease in a given area during a given period of time Occurrence also evaluated in terms of frequency and geographic distribution Epidemiology Play Animation: Epidemiology
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.15
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Descriptive Analytical Experimental Epidemiologists Study Disease Dynamics Using 3 Approaches
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Careful tabulation of data concerning a disease Record information about the location and time of the cases of disease Collect patient information Try to identify the index case (or first case) of the disease Descriptive Epidemiology
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Seeks to determine the probable cause, mode of transmission, and methods of prevention Useful in situations in which Koch’s postulates can’t be applied Often retrospective- investigation occurs after on outbreak has occurred Analytical Epidemiology
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Involves testing a hypothesis concerning the cause of a disease Application of Koch’s postulates is experimental epidemiology Experimental Epidemiology
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Infections acquired while in a health care facility Types of nosocomial infections Exogenous- pathogen acquired from the health care environment Endogenous- pathogen arise from normal microbiota due to factors within the health care setting Iatrogenic- results from modern medical procedures Nosocomial Infections
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.19
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Involves precautions designed to reduce the factors that result in disease Universal Precautions instituted by the CDC to limit exposure to pathogens Hand washing is the most effective way to reduce nosocomial infections Control of Nosocomial Infections
Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Agencies at the local, state, national, and global level share information concerning disease The United States Public Health Service is the national public health agency World Health Organization (WHO) coordinates public health services internationally Public health agencies work to limit disease transmission Monitor water and food safety Public health agencies campaign to educate the public on healthful choices to limit disease Epidemiology and Public Health