Principles of Disease and Epidemiology(Chapter 14)Lecture MaterialsforAmy Warenda Czura, Ph.D.Suffolk County Community CollegeEastern CampusPrimary Source for figures and content:Tortora, G.J. Microbiology An Introduction 8th, 9th, 10th ed. San Francisco: PearsonBenjamin Cummings, 2004, 2007, 2010.Amy Warenda Czura, Ph.D.1SCCC BIO244 Chapter 14 Lecture SlidesPathology = study of disease:cause, development, & effects on hostEtiology = study of the cause of a diseasePathogenesis = manner in which a diseasedevelopsEpidemiology = study of when and wherediseases occur and how they are transmittedInfection = invasion or colonization by pathogenic microbesDisease = change from a state of healthNormal Microbiota (Normal Flora)-in utero: sterile-once born microbes colonizeHuman body = ~1 x 1013 cellshas 1 x 1014 microbes in or on itNormal microbiota = permanent residents that do not usually cause diseasee.g. Staphylococcus on epidermis and mucusmembranes; Escherichia in colonAmy Warenda Czura, Ph.D.2SCCC BIO244 Chapter 14 Lecture SlidesType and location depends on:-availability of nutrients-physical & chemical factors-defenses of host-mechanical factorsSome carry out microbial antagonism = normal microbiota prevent over growth of harmful microorganisms (pathogens)e.g. vaginal microbiota (Lactobacillus) create pH 4 which inhibits C. albicans:disruption of flora (e.g. antibiotics) or pHcan lead to yeast infectionE. coli in intestines produce bacteriocinsthat inhibit other similar bacteria likeSalmonella (typhoid) & Shigella(dysentery)Amy Warenda Czura, Ph.D.3SCCC BIO244 Chapter 14 Lecture SlidesNormal microbiota may inhibit potential pathogens by:1. Competing for nutrients2. Producing toxins (bacteriocins)3. Altering pH4. Affecting O2 availability5. Occupying spaceRelationship between host and normal microbiota is a symbiosis (“living together”):-most microbiota are commensals(commensalism): microbe benefits, humanis unaffected-some are mutualistic (mutualism): bothhuman and microbe benefite.g. E. coli synthesize vitamin KProbiotics: typically lactic acid producingbacteria ingested to aid digestion and protect intestine from pathogensPrebiotics: chemicals that promote growthof beneficial bacteriaAmy Warenda Czura, Ph.D.4SCCC BIO244 Chapter 14 Lecture Slides-most pathogens tend to be parasites:microbe benefits, human is injuredPathogen = disease causing microbe, not typically part of normal microbiotaOpportunistic Pathogens:-ordinarily do not cause disease in theirnormal habitat (commensal or mutualist normal microbiota)-in new habitat or immune compromised host,can cause diseasee.g. Candida albicans:-80% of population has it in the gut ascommensal-in vagina: can cause vaginitis (new habitat)-can kill AIDS patients: systemic infection(immunocompromised host)Amy Warenda Czura, Ph.D.5SCCC BIO244 Chapter 14 Lecture SlidesEtiology of Infectious DiseaseKoch 1877:-first to link a particular microbe with a particular disease (etiology)-studying Anthrax, proved Bacillus anthracisto be causative agent-later showed tuberculosis to be due toMycobacterium tuberculosisKoch’s Postulates (used to study etiology)1. The same pathogen must be present inevery case of the disease2. The pathogen must be isolated from thediseased host and grown in pure culture3. The pathogen from the pure culture mustcause the same disease when it is inoculatedinto a new healthy animal host4. The pathogen must be isolated from theinoculated sick animal and must be shownto be the same original pathogenAmy Warenda Czura, Ph.D.6SCCC BIO244 Chapter 14 Lecture SlidesExceptions to Koch’s Postulates:1. Some microbes cannot be cultured onartificial mediae.g. Mycobacterium leprae – leprosy Treponema pallidum – syphilisIntracellular parasites-must use other methods such as growth inanimals or eggs or direct testing of patientsto prove all have the same pathogen2. One infectious disease can have multiplecauses/pathogense.g. pneumonia, meningitis, nephritis3. One pathogen can cause several diseaseconditionse.g. Streptococcus pyogenes = sore throat,scarlet fever, skin infections, osteomyelitis4. Ethical considerations-some human diseases have no animal host-can not infect humans on purpose toprove the agent causes diseasee.g. HIV (AIDS), Papillomavirus (cancer)Amy Warenda Czura, Ph.D.7SCCC BIO244 Chapter 14 Lecture SlidesClassifying Infectious Disease1. Patient AppearanceA. Symptoms = subjective changes in bodyfunction (e.g. pain) B. Signs = objective changes in bodyfunction that can be measured(e.g. fever)C. Syndrome = specific group of symptoms& signs that may accompany a particulardisease2. SpreadabilityA. Communicable disease = spreads fromone host to another (e.g. herpes)B. Contagious disease = spreads easily fromone person to another (e.g. chicken pox)C. Non-communicable disease = not spreadfrom one host to another:-either resident flora that becomes anopportunistic pathogen (e.g. UTI)-or accidental inoculation from environment (e.g. tetanus)Amy Warenda Czura, Ph.D.8SCCC BIO244 Chapter 14 Lecture Slides-rate of spread of contagious/communicabledisease is determined by susceptibility of population-immunization/vaccination: attempt to preventspreadHerd immunity = enough immune peoplein the population to prevent the spreadof disease3. OccurrenceIncidence = number of people who developthe disease in a particular time frame(indicates rate of spread)Prevalence = number of people who have the disease at one specified time (indicateshow seriously and how long the disease affects the population)A. Sporadic disease =occurs onlyoccasionally in population (e.g. typhoid)B. Endemic disease = constantly present ina population (e.g. hepatitis)Amy Warenda Czura, Ph.D.9SCCC BIO244 Chapter 14 Lecture SlidesC. Epidemic disease = many people in agiven area acquire the disease in a short amount of time (e.g. influenza)D. Pandemic disease = worldwide epidemic(e.g. AIDS)4. Severity and DurationA. Acute disease = develops rapidly, butlasts only a short time (e.g. common cold)B. Chronic disease = develops slowly, mayhave mild symptoms or signs, but is continual or recurrent for a long time(e.g. tuberculosis)C. Subacute disease = intermediatebetween acute and chronic(e.g. endocarditis)D. Latent disease = agent remains inactivefor a period of time, but then activates to cause disease (e.g. shingles)Amy Warenda Czura, Ph.D.10SCCC BIO244 Chapter 14 Lecture Slides5. Extent of Host InvolvementA. Local infection = microbe restricted to aparticular