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Transcript
Classification of medically important bacteria Bacteria Unicellular, Microscopic, Prokaryotic Organisms, Multiply By Binary Fission. Comparison Between Bacteria And Fungi And Protozoa Bacteria Type Chromosome One (Number) Nuclear Membrane Prokaryotic Fungi & Protozoa Eukaryotic Multiple Absent Present Comparison Between Bacteria and Fungi and Protozoa (Continued) Bacteria Fungi & Protozoa Mitochondria Absent Present Ribosomes 70s 80s Sterols Absent (Except In Mycoplasma) Usually Present Cell Wall Rigid Layer Of Peptidoglycan (Absent In Mycoplasma) No PeptidoGlycan (In some cases cellulose present) Bacteria can be divided into: 1. Filamentous Bacteria (Actinomycete) Most capable of branching 2. True (Euobacteria): Divide by Binary Fission Cocci Bacilli (rods) Vibrio (coma shape) 3. Spirocheates: Divide by Transverse Binary Fission 4. Mycoplasma Which Lack Rigid Cell Wall 5. Ricketssiae, and Chlamydia Intracellular parasites which are strict Taxonomic Ranks Formal Rank ________________________________________________________________________________________________________________________ Kingdom Division Class Order Family Example Prokaryotae Gracilicutes Scotobacteria Eubacteriales Enterobacteriae Genus Eschirichia, Streptococcus, Staphylococcus, Streptococcus, Klebsiella Species coli Pyogenes aureus pneumoniae pneumonia The Gram stain, t bacteria into two main groups, is the first step in bacterial classfication & identification. Bacteria stained purple are Gram + - their cell walls have thick petidoglycan and teichoic acid. stained pink are Gram – their cell walls have have thin peptidoglycan and lipopolysaccharides with no teichoic acid. Bacteria The Gram stain has four steps: 1. crystal violet, the primary stain: followed by 2.grams iodine, which acts as a mordant by forming a crystal violet-iodine complex, then 3. alcohol, which decolorizes, followed by 4. safranin, the counterstain. Is this gram stain positive or negative? Identify the bacteria. Is this gram stain positive or negative? Identify the bacteria. Gram staining tests the bacterial cell wall's ability to retain crystal violet dye during solvent treatment. Iodine is added as a mordant to form the crystal violet/iodine complex in order to render the dye impossible to remove. Ethyl-alcohol solvent acts as a decolorizer and dissolves the lipid layer from gram-negative cells. This enhances leaching of the primary stain from the cells into the surrounding solvent. Ethyl-alcohol will dehydrate the thicker grampositive cell walls, closing the pores as the cell wall shrinks. For this reason, the diffusion of the crystal violetiodine staining is inhibited, so the bacteria remain stained. Classification based on Shape Gram reaction Oxygen Free living & non free living Simplified Classification of Medically – Important Gram-positive Bacteria Free living Aerobes or facultative Anaerobes Cocci Arranged in clusters Micrococcus Staphylococcus Arranged in chains Streptococcus Anaerobes Peptostreptococcus Simplified Classification of Medically – Important Gram-positive bacteria Sporing Aerobes or facultative anaerobes Nonsporing Bacillus Corynebacterium Listeria Lactobacillus Nocardia Mycobacterium RODS Sporing Clostridium Nonsporing Actinomycosces Anaerobes Simplified Classification Of Medically – Important Gram-negative Bacteria Aerobes Neisseria Anaerobes Veillonella Cocci Important Gram-negative Bacteria Aerobes Pseudomonas Salmonella Shigella enterKlebsiella obac Proteus teriae Escherichia Facultative Anaerobes BACILLI cae Yersinia respir leigonella Bordetella Haemophilus zoonot Brucella Pasteurella francisella yersinia Vibrio(curved) Anaerobes Microaerophilic Bacteroids Fusobacterium Camplylobacter Simplified Classification Of Medically – Important Gram-negative Bacteria Aerobes Leptospira Anaerobes Treponema Borrelia Spirochetes Cell wall deficient bacteria------- Mycoplasma 2.Non- free living intra cellular— Rickettsia &chlamydia Capsule Present in Certain Bacteria. Polysaccharide; occasionally protein e.g. Bacillus anthracis importance a. Inhibit Phagocytosis b. Antigenic Study template for bacteria Diagrams Showing The Structure Of Bacterial Cell Walls Microbiology And The Patient Medical Microbiology – concerned with: (i) Aetiology (cause) (ii) Pathogenesis (Mechanism of production of disease) (iii) Laboratory Diagnosis (iv) Treatment of infection (v) Epidemiology (spread, distribution, prevalence of infection in the community) (vi) Control and prevention in community Laboratory Methods: Collection of specimens (i) Microscopy Stained Specimens Unstained Specimens (ii) (iii) (iv) (v) Culture Identification of the organism Tests for Antimicrobial agents serology Demonstration of Abs 6) Understand the proper use of Clinical Lab. a) b) c) Specimen collection and handling Requesting appropriate tests Interpretation of results of Lab. tests 7) Correct selection, use, monitoring of antimicrobial therapy 8) Understand methods of prevention of infection e.g. Vaccine, chemoprophylaxis, hygiene, isolation etc.