Introduction to Microbiology PDF

V.Gopalakrishnan UniKL RCMP Outline Role of Microbes in humans Pathogenicity and Routes of infection Mechanisms of Bacterial Virulence Bacterial morphology Gram staining properties Virulence factors Viruses as disease causing agents Fungi as disease causing agents Role of M...

V.Gopalakrishnan UniKL RCMP Outline Role of Microbes in humans Pathogenicity and Routes of infection Mechanisms of Bacterial Virulence Bacterial morphology Gram staining properties Virulence factors Viruses as disease causing agents Fungi as disease causing agents Role of Microbes in Humans  Beneficial  Nutritional  Normal flora (especially bacteria)  Vaccine development  Gene therapy  Investigative tool  As disease causing agents Pathogenicity  Attributes of pathogenicity  Transmissible  Infectivity  Virulence  Exogenous & endogenous infection Sites and routes of microbial infection Pathogen  Pathogen is a microorganism that is able to cause disease  Pathogens are of two types : 1. True pathogen 2. Opportunistic pathogen Role of Bacteria in disease  The Cell Envelope Gram Positive Gram Negative Bacterial Membrane Structures Structure Chemical Constituents Plasma membrane Phospolipid, protein, enzymes, etc., Cell Wall Gram-positive bacteria Peptidoglycan Glycan chain of GlcNAc & MurNAc crosslinked by peptide bridge Teichoic acid Polyribitol phosphate/glycerol phosphate cross-linked to pglycan Lipoteichoic acid Lipid-linked teichoic acid Cell Wall Gram-negative bacteria Peptidoglycan Thinner version of that found in gram-positive bacteria Periplasmic space Enzymes involved in transport, degradation, and synthesis Outer memb. Phospholipids with saturated fatty acids Proteins Porins, lipoprotein, transport proteins LPS Lipid A, core polysaccharide, O antigen Other structures Capsule Polysaccharides and polypeptides Pili Pilin, adhesins Flagellum Motor proteins, flagellin Proteins M protein of streptococci (as an example) Classification of Gram stainable pathogens Molecular postulates  VIRULENCE FACTORS can be identified  Virulence factor - only in pathogenic strains  Mutation - organism becomes less virulent  Transfer to a non- pathogenic organism - it becomes pathogenic  Immune response to pathogenic factor – should be protective Mechanisms of Bacterial Virulence  Adherence  Invasion  By-products of growth (gas, acid)  Toxins  Degradative enzymes  Cytotoxic proteins  Endotoxin  Superantigen  Induction of excess inflammation  Evasion of phagocytic and immune clearance  Capsule  Resistance to antibiotics  Intracellular growth Tissue Injury Toxins Exotoxins Endotoxins and non-specific immunity specific immunity - antigen What Are Viruses?  Nucleic acid genome -DNA or RNA  Protein coat - protection, entry  Lipid envelope in some viruses  Small - (20-400nm)  Obligate intracellular parasites Virus particle = virion White, DO and Fenner, FJ. Medical Virology, 4th Ed. 1994 17 Host Range  May be insect/animal, insect/plant  Do not cross Eukaryote / prokaryote boundary  Cell surface receptor  Ability to get out of cell and spread  Host anti-viral response  5 Basic Types Of Viral Symmetry icosahedral nucleocapsid nucleocapsid lipid bilayer ICOSAHEDRAL ENVELOPED ICOSAHEDRAL helical nucleocapsid COMPLEX nucleocapsid lipid bilayer glycoprotein spikes = peplomers HELICAL ENVELOPED HELICAL 20 Adapted from Schaechter et al., Mechanisms of Microbial Disease  DNA VIRUSES DOUBLE STRANDED SINGLE STRANDED COMPLEX NON-ENVELOPED ENVELOPED ENVELOPED NON-ENVELOPED PARVOVIRIDAE POXVIRIDAE HERPESVIRIDAE HEPADNAVIRIDAE CIRCULAR LINEAR PAPILLOMAVIRIDAE ADENOVIRIDAE All families shown are POLYOMAVIRIDAE icosahedral except for (formerly grouped together poxviruses as the PAPOVAVIRIDAE) 21 Modified from Volk et al., Essentials of Medical Microbiology, 4th Ed. 1991  RNA VIRUSES SINGLE STRANDED SINGLE STRANDED DOUBLE positive sense negative sense STRANDED ENVELOPED NONENVELOPED ENVELOPED NONENVELOPED ICOSAHEDRAL HELICAL ICOSAHE DRAL HELICAL ICOSAHEDRAL FLAVIVIRIDAE CORONAVIRIDAE PICORNAVIRIDAE ORTHOMYXOVIRIDAE REOVIRIDAE TOGAVIRIDAE CALICIVIRIDAE PARAMYXOVIRIDAE RETROVIRIDAE RHABDOVIRIDAE FILOVIRIDAE BUNYAVIRIDAE ARENAVIRIDAE 22 Adeno virus Hepatitis B Virus Papilloma virus Herpes virus Molluscum Contagiosum Rotavirus Paramyxo virus Influenza virus Enterovirus Rift valley fever virus 23 What are fungi  Fungi are non-photosynthetic protists  Grow as a single celled yeasts or  mass of branching, interlacing filaments (hyphae) – mycelium  Hyphae have - Perforated cross-walls – (septate) - No cross walls - a multinucleated – coenocyte (non septate)  The wall of the tubes made up of chitin - are equivalent to cell wall bacteria  Septate hyphae Coenocytic hyphae  Mycotic Diseases 1. Hypersensitivity - Allergy 2. Mycotoxicosis - Production of toxin 3. Mycetismus (mushroom poisoning) - Pre-formed toxin 4. Infection Laboratory methods in fungal identification 1. Wet Mount - Lactophenol cotton blue, KOH 2. Staining – Giemsa, mucicarmine, Calcoflour white stain, Gram, PAS 3. Fluorescent monoclonal antibody 4. Skin test 5. Biopsy & histopathology- GMS, H&E 6. Serology 7. Culture 8. DNA probes Human mycotic infections may be grouped into 1. Superficial mycoses 2. Cutaneous mycoses 3. Subcutaneous mycoses 4. Deep or systemic mycoses  Microsporum canis M. canis thick walled macroconidia  Macroconidia of M.gypseum Macroconidia of Epidermophyton floccosum Micro & Macro conidia of T. mentagrophytes Micro & Macro conidia of T. rubrum Molds: Penicillium species Candida