* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 13: Infection and Disease
Gastroenteritis wikipedia , lookup
Oesophagostomum wikipedia , lookup
Hepatitis B wikipedia , lookup
Rocky Mountain spotted fever wikipedia , lookup
Onchocerciasis wikipedia , lookup
Chagas disease wikipedia , lookup
Marburg virus disease wikipedia , lookup
Neonatal infection wikipedia , lookup
Sarcocystis wikipedia , lookup
Leptospirosis wikipedia , lookup
Cross-species transmission wikipedia , lookup
Schistosoma mansoni wikipedia , lookup
Hospital-acquired infection wikipedia , lookup
Eradication of infectious diseases wikipedia , lookup
Coccidioidomycosis wikipedia , lookup
Neglected tropical diseases wikipedia , lookup
Schistosomiasis wikipedia , lookup
Visceral leishmaniasis wikipedia , lookup
Sexually transmitted infection wikipedia , lookup
Chapter 13 Infection and Disease 13.1 The Host–Microbe Relationship • The Human Body Maintains a Symbiosis with Microbes • Infection refers to: • The relationship between the host and microbe • The competition for supremacy between them • If the host loses the competition, disease occurs • Microbiota are microbes that reside in the body without causing disease (in symbiosis) • In mutualism, both host and microbe benefit • In commensalism, the microbe benefits and the host is unaffected • Pathogens Differ in Their Ability to Cause Disease • In parasitism, pathogens cause damage and disease in the host • Pathogenicity refers to a microbe’s ability to enter a host and cause disease • Virulence is the degree of pathogenicity • Pathogenicity islands refers to gene clusters responsible for virulence • Several Events Must Occur for Disease to Develop in the Host • An exogenous infection occurs if a pathogen breaches the host’s external defense and enters sterile tissue • An endogenous infection occurs if normal microbiota enter sterile tissue • Opportunistic infections occur when commensals take advantage of a change in the body’s environment that favors the microbe • Primary infections occur in otherwise healthy bodies • Secondary infections occur in a body weakened by a primary infection • Local diseases are restricted to a single area • Systemic diseases disseminate to organs and systems 13.2 Establishment of Infection and Disease • Diseases Progress through a Series of Stages • Signs, symptoms, and syndromes characterize diseases • The incubation period is the time between entry of the microbe and symptom appearance • The prodromal phase is a time of mild signs or symptoms • The acme period (climax) is when signs and symptoms are most intense • As signs and symptoms subside, a period of decline occurs • The body systems return to normal during the period of convalescence • Acute diseases develop rapidly, cause severe symptoms, and fade quickly • Chronic diseases linger for long periods of time, and are slower to develop and recede • Pathogen Entry into the Host Depends on Cell Adhesion and the Infectious Dose • The portal of entry is the route an exogenous pathogen uses to enter the body • The infectious dose is the number of microbes entering the body • Many pathogens have adhesins that allow them to adhere to specific tissues • Breaching the Host Barriers Can Establish Infection and Disease • Invasiveness is the ability of a pathogen to penetrate tissues and spread • Many pathogens use phagocytosis by body cells to enter cells or pass through defenses • Successful Invasiveness Requires Pathogens to Have Virulence Factors • Pathogens have to adapt to a new environment when they enter a host • Enzymes can help pathogens resist body defenses • Some staphylococci produce coagulase to form a blood clot that protects them from phagocytosis • Others produce streptokinase, which dissolves fibrin clots and allows dissemination of the bacteria • Hyaluronidase enhances pathogen penetration through tissues • Leukocidins disintegrate neutrophils and macrophages • Hemolysins dissolve red blood cells • Virulence can be enhanced in biofilms because immune cells cannot reach bacterial cells • Toxigenicity is the ability of pathogens to produce toxins • Toxemia is the presence of toxins in the blood • Exotoxins are proteins produced during bacterial metabolism • Neurotoxins act on the nervous system • Enterotoxins act on the gastrointestinal tract • Antitoxins are produced by the host body and neutralize toxins • Toxoids are toxins whose toxicity has been destroyed but still elicit an immune response • Endotoxins are released upon disintegration of gram-negative cells • They cause blood coagulation • Endotoxin shock may occur with antibiotic treatment of diseases caused by gram-negative bacilli • Pathogens Must Be Able to Leave the Host to Spread Disease • Pathogens or toxins leave the host through a portal of exit 13.3 Infectious Disease Epidemiology • Epidemiologists Have Several Terms that Apply to the Infectious Disease Process • Communicable diseases are contagious • They are transmittable among hosts in a population • Noncommunicable diseases are not easily transmitted to another host • They are acquired directly from the environment • Infectious Diseases Can Be Transmitted in Several Ways • Direct contact methods involve close or personal contact with an infected person • Indirect contact methods can involve fomites • Epidemiologists Often Have to Identify the Reservoir of an Infectious Disease • Reservoirs are ecological niches where microbes live and reproduce • Carriers have recovered from the disease but continue to shed the disease agents • Diseases Are Also Described by How They Occur Within a Population • An endemic disease is habitually present at a low level in a certain geographic area • • • An epidemic disease occurs in a region in excess of what is normally found in that population • An outbreak is a more contained epidemic • A pandemic is a worldwide epidemic Nosocomial Infections Are Serious Health Threats within the Health Care System • Health care-associated infections (HAIs) occur as a result of receiving treatment for another condition • Nosocomial infections are HAIs associated with hospitals • They occur as a result of chains of transmission Infectious Diseases Continue to Challenge Public Health Organizations • Globalization means that diseases emerging anywhere in the world can be spread globally • Zoonoses are diseases transmitted from other vertebrate animals to humans • Disease emergence and reemergence are related to: • Changes in land use or agriculture practices • Changes in human demographics • Poor population health • Pathogen evolution • Contamination of food sources and water supplies • International travel • Failure of public health systems • International trade • Climate change