MICROB 2300 1nd Edition Lecture 1 Outline of Current Lecture I. What is microbiology?II. Why important?III. What information is important for you?IV. THINK LIKE A PHYSICIAN AND ASK 7 BASIC QUESTIONS MICROBIAL PATHOGENESIS I I. SYMBIOTIC RELATIONSHIPS BETWEEN MICROBES AND THEIR HOSTSII. Normal MicrobiotaIII. PathogenicityIV. MEDIAN INFECTIOUS DOSE (ID50)V. INFECTIOUS DOSE OF VARIOUS FOODBORNE BACTERIAL PATHOGENSVI. Opportunistic PathogensVII. Primary PathogensCurrent LectureI. What is microbiology?a. "The study of micro organisms (including bacteria, viruses, fungi, & parasites) which are of medical importance"b. Bacteria is highly adaptive.II. Why important?a. Morbidity & Mortality i. 2nd leading cause of death worldwide (~23%)b. Healthcare Associated Infections (HAIs) i. Rapidly increasing cause of death in healthcare settingii. Approximately 30% of hospital patients are on antibiotics at any one timec. Antibiotic resistancei. They've evolved mechanisms to resist antibiotics, making this more of a problemii. Diseases we've controlled may get to a point where we can'tIII. What information is important for you?a. Clinical setting:i. Information that you can use to diagnose and manage a patient with infectious diseaseb. Research setting:i. Information that you can use to develop new therapies against infectious diseaseIV. THINK LIKE A PHYSICIAN AND ASK 7 BASIC QUESTIONSa. WHO is at risk?b. WHAT tests should be performed?c. WHERE is the organism prevalent (body site and geographic area)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.d. WHEN is the isolation of the organism important?e. WHY is this organism able to cause disease?f. WHICH species are medically important?g. HOW is the disease managed and prevented? Many pathogens aren't trying to cause disease. A lot of issues are actually caused by our immune system trying to control it. MICROBIAL PATHOGENESIS I I. SYMBIOTIC RELATIONSHIPS BETWEEN MICROBES AND THEIR HOSTSa. We host ~100 million microorganismsb. Mutualismi. Both species benefit from the associationii. EX: Escherichia coli in human intestinal tractc. Commensalismi. One species benefits without harming the otherii. EX: Staphylococcus epidermidis on human skind. Parasitismi. One species derives benefit while damaging its hostii. EX: Mycobacterium tuberculosis → human specific pathogenII. Normal Microbiotai. Body is colonized by numerous mutualistic and commensal symbiontsii. Microbes that colonize the body's surfaces without normally causing disease constitute the body's normal microbiota (flora, older term)iii. Many organisms are beneficial → intestinal E. coli strains produce Vitamin Ki. Resident microbiotai. Remain a part of the normal microbiota throughout our livesii. Many of these organisms protect us against infection & pathogensii. Transient microbiotai. Remain in the body for only a few hours, days, or weeksIII. Pathogenicitya. Pathogenicity: the ability of a organism to cause disease within a hosti. Pathogenicity is the product of an organism’s VIRULENCE FACTORSb. Virulence: the relative ability of an organism to cause disease within the same hosti. The virulence of strains within a species can varyii. Quantitative measure: Median infectious dose (ID50)IV. MEDIAN INFECTIOUS DOSE (ID50)a. Median infectious dose (ID50)i. the number of microorganisms required to cause an infection in half the members of atested population b. High virulence  few microorganisms sufficient to initiate disease (\ low ID50 ≡ highly contagious organism)c. Low/ moderate virulence  many microorganisms required to initiate disease (\ high ID50 ≡ moderately contagious organism)d. Summary:  Number of organisms   likelihood of diseaseV. INFECTIOUS DOSE OF VARIOUS FOODBORNE BACTERIAL PATHOGENSa. Escherichia coli : very large (106 - 108 of organisms)b. V. cholerae : quite large ( 104 - 105 of organisms)c. Campylobacter jejuni : low (500 organisms)d. Shigella : very low (~10 organisms) i. i.e. Shigella is highly virulent with a Low ID50VI. Opportunistic Pathogensa. A usually harmless microbe that becomes pathogenic under favorable conditions; Often a member of the normal microbial florab. Conditions that provide opportunities for pathogensi. Immune suppression 1. various causesii. Changes in relative abundance of normal microbiota 1. antibiotic treatmentsiii. Introduction of normal microbiota into unusual site in the body 1. medical devicesc. Pseudomonas aeruginosai. Pseudomonas aeruginosa is a prototypic example of an opportunistic pathogen of humansii. While healthy individuals are rarely infected with P.a., those with compromised immune systems (diabetics, cancer patients, burn victims) are highly susceptibleiii. Diabetic Ulcer1. Tissue infected with P.a.2. Due to poor circulation/ intrinsic antibiotic resistance of P.a., prognosis is poord. Summaryi. Low probability of causing disease in normal healthy hostii. Increased probability of causing disease in immunocompromised hostiii. Responsible for high morbidity and mortality in the developed worldVII. Primary Pathogensa. Obligate pathogens: Organisms which must cause disease to both SURVIVE and be TRANSMITTEDi. Often host restricted, e.g. human specific pathogen Neisseria gonorrhoeaeb. Strict pathogens: Organisms which typically cause disease in one or more hosts. Can survive in the environment, e.g. Bacillus anthracis c. “Accidental pathogens”: Commensal organisms which occasionally cause disease  negative effect on both the host and the pathogen, e.g. Neisseria meningitidisd. Summaryi. High potential for causing diseaseii. Can be prevented by immunizationiii. Responsible for significant morbidity and mortality in the developing