Chapter 14 Lecture Microbiology PDF

Chapter 14 Principles of Disease and Epidemiology Lectures prepared by Christine L. Case...

Chapter 14 Principles of Disease and Epidemiology Lectures prepared by Christine L. Case Edited by Erica Foote © 2013 Pearson Education, Inc. Copyright © 2013 Pearson Education, Inc. Lectures prepared by Christine L. Case  Normal Microbiota © 2013 Pearson Education, Inc. 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 Bacteria (orange Bacteria (brown) Bacteria (orange) spheres) on the on the lining of in the small surface of the stomach intestine the nasal epithelium © 2013 Pearson Education, Inc. Symbiosis  In commensalism, one organism benefits, and the other is unaffected  In mutualism, both organisms benefit  In parasitism, one organism benefits at the expense of the other  Some normal microbiota are opportunistic pathogens © 2013 Pearson Education, Inc. 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: live microbes applied to or ingested into the body, intended to exert a beneficial effect perhaps by competition? © 2013 Pearson Education, Inc.  Patterns of Disease © 2013 Pearson Education, Inc. 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- biggest one?  Chemotherapy © 2013 Pearson Education, Inc. Figure 14.5 The stages of a disease. Prodromal period (mild signs or symptoms) Incubation period (no signs or symptoms) Period of Period of illness decline Period of convalescence Number of microbes Most severe signs Signs and and symptoms symptoms Time © 2013 Pearson Education, Inc. Check Your Understanding  The incubation period for a cold is 3 days, and the period of disease is usually 5 days. If the person next to you has a cold, when will you know whether you contracted it?  What happens if you don’t convalesce? © 2013 Pearson Education, Inc.  Classifying Infectious Diseases © 2013 Pearson Education, Inc. Pathology, Infection, and Disease  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 © 2013 Pearson Education, Inc. 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  Communicable disease: a disease that is spread from one host to another  Contagious disease: a disease that is easily spread from one host to another  Noncommunicable disease: a disease that is not transmitted from one host to another © 2013 Pearson Education, Inc. Occurrence of a Disease  Incidence: fraction of a population that contracts a disease during a specific time (new infections)  Prevalence: fraction of a population having a specific disease at a given time (all infections)  Sporadic disease: disease that occurs occasionally in a population  Epidemic disease: disease acquired by many hosts in a given area in a short time  Pandemic disease: worldwide epidemic  Endemic disease: disease constantly present in a population  When reading graphs, always look for other factors that can effect the data. Correlation (things are related) is not the same as causation (something causes an effect). © 2013 Pearson Education, Inc. Figure 14.4 Reported AIDS cases in the United States. Second Third Fourth 120,000 First 250,000 cases 250,000 250,000 250,000 cases cases Cases 100,000 Number of cases Expansion of surveillance 80,000 case definition 60,000 40,000 20,000 0 1979 1983 1987 1991 1995 1999 2003 2007 Year © 2013 Pearson Education, Inc.  Epidemiology © 2013 Pearson Education, Inc. Epidemiology- the study of where and when diseases occur. John Snow 1848–1849 Mapped the occurrence of cholera in London Ignaz Semmelweis 1846–1848 Showed that handwashing decreased the incidence of puerperal fever Florence 1858 Showed that improved Nightingale sanitation decreased the incidence of epidemic typhus © 2013 Pearson Education, Inc. Map of London: Used WITHOUT permission: http://sphweb.bumc.bu.edu/otlt/M PH-Modules/EP/EP713_Descripti veEpi/EP713_DescriptiveEpi_pri nt.html Boston University School of Public Health © 2013 Pearson Education, Inc. Epidemiology  Descriptive: collection and analysis of data  Retrospective  Prospective  Snow – London, cholera, water pump  Analytical: comparison of a diseased group and a healthy group  Case control method  Cohort method  Nightingale – soldiers, civil war, typhus  Experimental: controlled experiments  Semmelweis- hand washing between dissection and birth © 2013 Pearson Education, Inc. Epidemiology  Case reporting: health care workers report specified disease to local, state, and national offices  Nationally notifiable diseases: physicians are required to report occurrence to CDC which tracks:  Morbidity: incidence of a specific notifiable disease  Mortality: deaths from notifiable diseases  Morbidity rate: number of people affected in relation to the total population in a given time period  Mortality rate: number of deaths from a disease in relation to the population in a given time © 2013 Pearson Education, Inc.  The Spread of Infection- Important Considerations in Epidemiology © 2013 Pearson Education, Inc. Reservoirs of Infection  Sometimes unidentified... Ebola?  Continual sources of infection  Human: AIDS, gonorrhea  Carriers may have unapparent infections or latent diseases (SIV in monkeys- not ill)  Animal: rabies, Lyme disease (bacteria in mammal blood, transmitted by tick)  Some zoonoses (animal diseases) may be transmitted to humans  Nonliving: botulism, tetanus  Soil © 2013 Pearson Education, Inc. Transmission of Disease  Contact  Direct: requires close association between infected and susceptible host  Indirect: spread by fomites- objects that carry disease  Droplet: transmission via airborne droplets (considered airborne if moves more than 3 feet) © 2013 Pearson Education, Inc. Figure 14.7 Vehicle transmission. Water Food Air Transmission by an inanimate reservoir (food, water, air) © 2013 Pearson Education, Inc. Vector transmission  Arthropods, especially fleas, ticks, and mosquitoes  Transmit disease by two general methods:  Mechanical transmission: arthropod carries pathogen on feet  Biological transmission: pathogen reproduces in vector © 2013 Pearson Education, Inc. Check Your Understanding  Why are carriers important reservoirs of infection?  How are zoonoses transmitted to humans?  Give an example of direct transmission, indirect transmission, and vector transmission. © 2013 Pearson Education, Inc.  Nosocomial Infections © 2013 Pearson Education, Inc.  Figure 14.9 Nosocomial infections. Microorganisms Compromised in hospital host environment Nosocomial infection Are acquired as a result of a hospital stay Affect 5– Chain of transmission 15% of all hospital patients © 2013 Pearson Education, Inc. Common Causes of Nosocomial Infections Percentage Percentage of Resistant to Total Infections Antibiotics Coagulase-negative 15% 89% staphylococci S. aureus 15% 80% Enterococcus 10% 4–71% Gram-negative rods 15–25% 3–32% C. difficile 13% Not reported © 2013 Pearson Education, Inc. MRSA  USA100: 92% of health care strains  USA300: 89% of community-acquired strains  Basilea Pharma. Ceftobiprole is approved in Canada, Switzerland, Russia, Azerbaijan, Ukraine and Hong Kong. The FDA denied approval in 2009. © 2013 Pearson Education, Inc. Check Your Understanding  What interacting factors result in nosocomial infections?  How are nosocomial infections primarily transmitted, and how can they be prevented? © 2013 Pearson Education, Inc.  Emerging Infectious Diseases © 2013 Pearson Education, Inc. Emerging Infectious Diseases: - Diseases that are new, increasing in incidence, or showing a potential to increase in the near future Contributing factors  Genetic recombination  E. coli O157, avian influenza (H5N1)  Evolution of new strains  V. cholerae O139  Inappropriate use of antibiotics and pesticides  Antibiotic-resistant strains  Changes in weather patterns*** article about bed bugs and Chagas disease  Hantavirus © 2013 Pearson Education, Inc. Clinical Focus 13.1 Influenza: Crossing the Species Barrier Avian gene pool 1918 H1N1 Human H3N2 North American swine Triple reassortment H1N2 Eurasian swine H1N1 2009 H1N1 pandemic © 2013 Pearson Education, Inc. Emerging Infectious Diseases  Modern transportation  West Nile virus, Zika  Ecological disaster, war, and expanding human settlement  Coccidioidomycosis, plague, Zika  Animal control measures  Lyme disease  Public health failure  Diphtheria © 2013 Pearson Education, Inc. Figure 14.10 a & b Epidemiological graphs. 40,000 35,000 Number of reported cases 30,000 25,000 20,000 15,000 10,000 5,000 0 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 (a) Lyme disease cases, 1999–2010 600 500 400 Reported cases per 100,000 people 300 200 100 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month (b) Lyme disease by month, 2009 © 2013 Pearson Education, Inc. Figure 14.10c Epidemiological graphs. 120 100 Reported cases per 100,000 people 80 60 40 20 0 1948 1958 1968 1978 1988 1998 2008 Year Reported tuberculosis cases, 1948–2010 © 2013 Pearson Education, Inc.  Decline began before TB identified… what is causing the decline? Used WITHOUT permission: http://sphweb.bumc.bu.edu/otlt/MPH-Modules/EP/EP713_DescriptiveEpi/EP713_DescriptiveEpi_print.html Boston University School of Public Health © 2013 Pearson Education, Inc.