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TORTORA FUNKE CASE ninth edition MICROBIOLOGY an introduction 14 Principles of Disease and Epidemiology PowerPoint® Lecture Slide Presentation prepared by Christine L. Case Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Principles of Disease and Epidemiology Pathology: The study of disease Etiology: The study of the cause of a disease Pathogenesis: The development of disease Infection: Colonization of the body by pathogens Disease: An abnormal state in which the body is not functioning normally Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Normal Microbiota and the Host Transient microbiota may be present for days, weeks, or months. Normal microbiota permanently colonize the host. Symbiosis is the relationship between normal microbiota and the host. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.1c Normal Microbiota and the Host Locations of normal microbiota on and in the human body. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.1c Normal Microbiota and the Host Microbial antagonism is a competition between microbes. Normal microbiota protect the host by: Occupying niches that pathogens might occupy Producing acids Producing bacteriocins Probiotics are live microbes applied to or ingested into the body, intended to exert a beneficial effect. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Symbiosis Commensalism Mutualism Parasitism Some normal microbiota are opportunistic pathogens. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Koch’s Postulates Koch's postulates are used to prove the cause of an infectious disease. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.3 (1 of 2) Koch’s Postulates Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.3 (2 of 2) Classifying Infectious Diseases Symptom: A change in body function that is felt by a patient as a result of disease. Sign: A change in a body that can be measured or observed as a result of disease. Syndrome: A specific group of signs and symptoms that accompany a disease. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classifying Infectious Diseases Communicable disease Contagious disease Noncommunicable disease Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Occurrence of Disease Incidence: Fraction of a population that contracts a disease during a specific time. Prevalence: Fraction of a population having a specific disease at a given time. Endemic disease: Disease constantly present in a population. Epidemic disease: Disease acquired by many hosts in a given area in a short time. Pandemic disease: Worldwide epidemic. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Reported AIDS cases in the United States Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.4 Obesity Epidemic Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Severity or Duration of a Disease Acute disease: Symptoms develop rapidly. Chronic disease: Disease develops slowly. Latent disease: Disease with a period of no symptoms when the patient is inactive. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Extent of Host Involvement Local infection: Pathogens are limited to a small area of the body. Systemic infection: An infection throughout the body. Septicemia: Growth of bacteria in the blood. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Predisposing Factors Make the body more susceptible to disease Short urethra in females Inherited traits such as the sickle-cell gene Climate and weather Fatigue Age Lifestyle Chemotherapy Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Stages of a Disease Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.5 Reservoirs of Infection Reservoirs of infection are continual sources of infection. Human — AIDS, gonorrhea Carriers may have inapparent infections or latent diseases. Other Animals — Rabies, Lyme disease Some zoonoses may be transmitted to humans. Nonliving — Botulism, tetanus Soil and Water Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Viral and Bacterial Zoonoses Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.2 (1 of 3) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.2 (2 of 3) Transmission of Disease Contact Direct Indirect: Spread by fomites. Droplet Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Disease Vehicle: Transmission by an inanimate reservoir (food, water). Vectors: Arthropods, especially fleas, ticks, and mosquitoes. Mechanical Biological Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Disease Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figures 14.7b, 14.8 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.3 Nosocomial (Hospital-Acquired) Infections Are acquired as a result of a hospital stay. 5-15% of all hospital patients acquire nosocomial infections. ~20,000 die as a result per year Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figures 14.6b, 14.9 Relative Frequency of Nosocomial Infections Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.5 Common Causes of Nosocomial Infections Percentage of Nosocomial Infections Percentage Resistant to Antibiotics Gram + cocci 51% 29-89% Gram – rods 30% 3-32% Clostridium difficile 13% Fungi 6% Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Emerging Infectious Diseases (EIDs) Diseases that are new, increasing in incidence, or showing a potential to increase in the near future. Contributing factors Genetic recombination E. coli 0157, Avian influenza (H5N1) Evolution of new strains V. cholerae 0139 Inappropriate use of antibiotics and pesticides Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Emerging Infectious Diseases Changes in weather patterns Malaria Modern Transportation West Nile virus Animal control measures Lyme disease Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epidemiology The study of where and when diseases occur Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.10 Epidemiology John Snow 1848-1849 Mapped the occurrence of cholera in London Ignaz Semmelweis 1846-1848 Showed that hand washing decreased the incidence of puerperal fever Florence Nightingale 1858 PLAY Animation: Epidemiology Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Showed that improved sanitation decreased the incidence of epidemic typhus Centers for Disease Control and Prevention (CDC) Morbidity: Incidence of a specific notifiable disease. Mortality: Deaths from notifiable diseases. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Centers for Disease Control and Prevention (CDC) Collects and analyzes epidemiological information in the United States. Publishes Morbidity and Mortality Weekly Report (MMWR) www.cdc.gov Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings “AIDS” to “Gonorrhea”; “Pertussis” to “Streptococcal Toxic Shock Syndrome” Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.7 (1 of 2) “Haemophilus influenzae” to “Mumps”; “Streptococcus pneumonaie” to “Yellow Fever” Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.7 (2 of 2)