Host-Microbe InteractionsPowerPoint PresentationSlide 3Slide 4Anatomical Barriers as EcosystemsSlide 6Slide 7Slide 8Slide 9Slide 10Slide 11PathogenicitySlide 13Slide 14Slide 15Slide 16Etiology of Infectious DiseasesSlide 18Slide 19Slide 20Stages of an Infectious DiseaseSlide 22Slide 23Host-Microbe InteractionsChapter 14•Disease•Etiology•Pathogen–Primary vs. opportunistic •Virulence•Contamination•Infection vs. Infestation •Pathogenesis•Pathology•Symptoms •Signs •Syndrome •SequelaeAnatomical Barriers as Ecosystems•Skin and mucous membranes are physical barriers to infection–May supply foundation for microbial ecosystem•Humans are usually sterile in utero •Exposed to microbes during and immediately after birth –microbial populations begin to establish •Normal flora –Resident flora –Transient flora •Probiotics• Isolated colonies in specific body regions•Dominant type of organism may change with age and situation•Factors that influence distribution of Flora:–Nutrient availability, salinity, oxygen availability, host defenses and mechanical factors–Normal flora may offer protection from disease-causing organisms–microbial antagonism–Competitive exclusion–Bacteriocins•Symbiotic relationships form between microorganism and host–Relationships may change depending on state of host and attributes of microbes–Mutualism (++)•both partners benefit–Intestinal bacteria–Probiotics –Commensalisms (+ neutral) •one partner benefits and other is unharmed–Flora on skin and conjunctiva –Parasitism (+-) •microbe benefits at expense of host–Pathogens–State of host resistance usually determines extent of infection•primary infection •secondary infection•Sub-clinical or in-apparent infectionPathogenicity•Many people are carriers of pathogens–Viruses; Neisseria; Salmonella; Streptococcus•Why are they not affected?•Predisposing factors:–gender–genetic background–climate and weather–inadequate nutrition–age–habits and lifestyle–chemotherapy–emotional disturbances•Characteristics of infectious disease:–communicable•contagious •Often reflects ID50–non-communicable diseaseEtiology of Infectious Diseases •Robert Koch demonstrated that specific microbes caused specific diseases–experimented with grazing animals infected with anthrax –Later work with TB got more interest•Koch developed a series of steps (Koch’s postulates): –Same pathogen must be present in each case of disease–Pathogen is isolated from diseased host and grown in pure culture–Pure culture must cause disease when inoculated into healthy animal–Pathogen must be re-isolated from inoculated animal•Exceptions to Koch’s postulates–some bacteria have unique culture requirements –some diseases are caused by multiple pathogens•Polymicrobial diseases (mixed infections) –Ethical considerationsStages of an Infectious DiseaseDuration of a Disease–acute diseases–chronic diseases–latent diseaseDistribution of pathogens–Local infections –Systemic