Lecture 2_Ch 1.2 Basic Concepts of Infection PDF

Sherris & Ryan's Medical Microbiology Eighth Edition Kenneth J. Ryan 1 Infection—Basic Concepts Copyright © McGraw Hill  Background Kenneth J. Ryan / Sh...

Sherris & Ryan's Medical Microbiology Eighth Edition Kenneth J. Ryan 1 Infection—Basic Concepts Copyright © McGraw Hill  Background Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  Which of the following entities are strict intracellular parasites infecting a wide range of hosts, including bacteria? A. Bacteriophages B. Fungi C. Protozoa D. Algae © McGraw-Hill Education, 2019  INFECTIOUS AGENTS: THE MICROBIAL WORLD The major classes of microorganisms in terms of ascending size and complexity are viruses, bacteria, fungi, and parasites. Viruses are not cells at all. They have a genome and some structural elements, but must take over the machinery of another living cell (eukaryotic or prokaryotic) to replicate. Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  Increasing complexity: viruses → bacteria → fungi → parasites Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology Copyright © McGraw Hill  VIRUSES Strict intracellular parasites of other living cells, not only of mammalian and plant cells but also of simple unicellular organisms, including bacteria (the bacteriophages). Simple forms of replicating, biologically active particles that carry genetic information in either DNA or RNA molecules. Most mature viruses have a protein coat (Capsid) over their nucleic acid and, sometimes, a lipid surface membrane (Envelope) derived from the cell they infect. Viruses lack the protein synthesizing enzymes and structural apparatus necessary for their own replication. Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  Which structure is characteristic of most mature viruses and what is part of the host membrane? A. Capsid; Envelope B. Nucleus; Ribosome C. Spike protein; Capsid D. Golgi Apparatus; Membrane receptor © McGraw-Hill Education, 2019  INFECTIOUS DISEASE Pathogens: Only a small portion of the thousands of species of viruses, bacteria, fungi, and parasites cause disease = pathogens. Types of Pathogens: There are plant pathogens, animal pathogens, fish pathogens, and human pathogens. Virulence: Pathogens have varying degrees of potency = virulence. Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019 © McGraw-Hill Education, 2019 How are we going to study viruses? Virus general properties and characteristics (identification and differential diagnosis) Epidemiology Chain of infection Pathogenesis (Physiopathology) Signs and symptoms Diagnosis Treatment Prevention and public health © McGraw-Hill Education, 2019  Each agent has its own mode of spread Poor socioeconomic conditions foster infection Modern society may facilitate spread Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology Copyright © McGraw Hill  PATHOGENESIS Producing disease is a very complicated process. Pathogenicity is multifactorial. Virulence factors are required to persist, cause disease, and escape to repeat the cycle. Attachment usually involves specialized surface molecules or structures that correspond to receptors on human cells. Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  PATHOGENESIS The inflammatory response they stimulate is enough to disrupt function in some way. (Destruction of host cells is among the more common mechanisms.) Evading the immune response is a major feature of virulence Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  CLINICAL ASPECTS OF INFECTIOUS DISEASE Manifestations: Fever, pain, and swelling are the universal signs of infection → the particular organs involved and the speed of the process dominate the signs and symptoms of disease. Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  CLINICAL ASPECTS OF INFECTIOUS DISEASE Diagnosis: Most microorganisms can be isolated from the patient, grown in artificial culture, and identified. Others can be seen microscopically or detected by measuring the specific immune response to the pathogen. – Empiric diagnosis? Denning, D, et al. 2020 Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  CLINICAL ASPECTS OF INFECTIOUS DISEASE Treatment: – Antibiotics – Antifungal and antiprotozoal – Antivirals (easy or hard to use?) Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019  CLINICAL ASPECTS OF INFECTIOUS DISEASE Public health and immunization are primary preventive measures Kenneth J. Ryan / Sherris & Ryan's Medical Microbiology © McGraw-Hill Education, 2019 Check your understanding Compared to other microbes, structurally, viruses are more or less complex? Do viruses lack the protein synthesizing enzymes and structural apparatus necessary for their own replication? What is the difference between pathogenicity and virulence? How do viruses interact with their hosts cells? How virus genome interact with intracellular organelles? How can we make a diagnosis of a viral infection? What is the difference between infection and disease? © McGraw-Hill Education, 2019