Microbial Pathogenesis Lecture 1 PDF

MICR3268 MICROBIAL PATHOGENESIS Lecture 1 – Introduction to pathogenic microorganisms Dr. Kelly Brathwaite 1  General information Office hours: Wednesdays 10 am-12 pm Office location: Biology Extension Telephone: 417-4354 Contact: [email protected]....

MICR3268 MICROBIAL PATHOGENESIS Lecture 1 – Introduction to pathogenic microorganisms Dr. Kelly Brathwaite 1  General information Office hours: Wednesdays 10 am-12 pm Office location: Biology Extension Telephone: 417-4354 Contact: [email protected]  To create a better understanding of: ✓ Mechanisms by which microorganisms infect and cause disease in humans ✓ Modes of transmission of disease ✓ The outcome of microbial COURSE infection OBJECTIVES ✓ Mechanisms by which a human host defends itself against microbial infection To examine the measures used to control infectious diseases To take a closer look at specific infectious diseases 6 of the human body  Prerequisite courses for MICR3268 All students MUST have completed the following: MICR2260 (Essential Microbiology) (or MICR2251 General Microbiology) & BIOL1030 Introduction to Genetics (or BIOL1151 Introductory Genetics)  Assessment Final theory exam (2 hours) 50% Practical report/quizzes 15% In-course tests/assignments 35%  Course outline 18 LECTURES 6 TUTORIALS ASSESSMENTS: 2 x IN-COURSE TESTS, CASE STUDY, PRESENTATION, FINAL EXAM ------------------------------------------------------------ 6 PRACTICALS ASSESSMENTS: LAB REPORT, QUIZZES  At the end of this lecture you Learning should be able to: Objectives ❖ Understand the concept of pathogenicity. of Today’s ❖ Distinguish between infection and disease. Lecture ❖ Illustrate that not all microbes cause disease. ❖ Identify possible outcomes of exposure to microbes. ❖ State Koch’s postulates and explain their limitations. ❖ Show how Molecular Koch’s postulates can be applied to microbial pathogenicity. 12 BUT FIRST… Pathogens are However, the Some pathogens Pathogenic microorganisms majority of cause disease microorganisms that have the microorganisms only under possess potential to are generally certain mechanisms that cause disease harmless (not circumstances allow them to pathogenic) ie opportunistic manipulate the immune system of the host in order to promote disease Introduction Infection  Disease 18  Definitions Infection: Invasion or colonization of the body by a (pathogenic) microorganism Disease : Infection that results in a detrimental change in the health of the host Colonization: Establishment of proliferating microbes on skin or mucous membranes Pathogenesis: Means by which disease develops Possible outcomes of exposure to microorganisms Harvey et al, 2013  Types of infections Subclinical o An infection with no detectable symptoms (patient referred to as an asymptomatic carrier) Famous Example - “Typhoid Mary”  Types of infections Latent o A dormant infection which has the potential to become reactivated with the reoccurrence of symptoms Opportunistic o An infection caused by an organism that generally does not cause disease unless normal host defenses are compromised  Types of infections Primary o An infection that may become latent and later cause other disease manifestations (symptoms) Secondary o 1) A latent infection that has been reactivated or 2) The second stage of an infection Mixed o An infection where two or more bacteria infect the same tissue Agents of infectious disease  Microbes and infectious disease Early work led the way for scientists to understand the role of microorganisms in infectious disease These principles paved the way for modern day microbiological techniques and medical microbiology  Robert Koch (1843-1910) German physician/medical microbiologist Developed an experimental method to determine whether a particular microorganism is the cause of a disease Built on Pasteur’s work and proved that the bacterium Bacillus anthracis was the cause of anthrax Awarded the 1905 Nobel Prize for his work on tuberculosis  Question You successfully isolated a particular microorganism from an area of infected tissue. Can we therefore conclude that this particular organism caused the infection?  ✓ Derived from Robert Koch's early work on Koch’s infectious diseases (anthrax and postulates tuberculosis). ✓ Attempted to establish a standard for identifying the specific cause of an infectious disease. ✓ Developed to convince novice microbiologists to use more rigorous criteria before claiming a causal relationship between a microorganism and a disease. Harvey et al, 2013 Some of the Normal flora criteria cannot be causing Pathogen may met by many disease cause pathogenic Opportunistic Some subclinical microorganisms pathogens pathogens infection in may cause some Cannot be grown in pure culture in the several individuals vs. lab (in vitro) diseases clinical No animal model infection in available others Ethics Limitations to Koch’s postulates  Molecular Koch’s Postulates 1. The phenotype or property under investigation should be significantly linked with pathogenic strains of a species and not with non-pathogenic strains 2. Specific inactivation of the gene/s associated with the suspected virulence trait should lead to a measurable decrease in pathogenicity or virulence (NB. NOT ALL GENES FROM PATHOGENIC MICROORGANISMS PLAY A ROLE IN PATHOGENICITY OR VIRULENCE) 3. Reversion or replacement of the mutated gene with the wild type gene should restore pathogenicity or virulence  Useful Resources CDC – Articles on emerging infectious diseases https://wwwnc.cdc.gov/eid/ CDC – A-Z index on diseases and conditions https://www.cdc.gov/DiseasesConditions/ WHO – Fact sheets on infectious diseases https://www.who.int/topics/infectious_diseases/facts heets/en/ “Contagion” – A Warner Bros movie that depicts what happens during an outbreak of a novel, virulent infectious disease (Compare movie to what occurred during COVID-19 pandemic) Any Questions?