PATH 3100 Introduction to Medical Microbiology - PDF

PATH 3100. Introduction to Medical Microbiology Characteristics of Bacteria Dr. Enioutina, M.D., Ph.D. https://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Prokaryote _cell.svg/914px-Prokaryote_cell.svg.png, accessed 7/20...

PATH 3100. Introduction to Medical Microbiology Characteristics of Bacteria Dr. Enioutina, M.D., Ph.D. https://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Prokaryote _cell.svg/914px-Prokaryote_cell.svg.png, accessed 7/20/20  Objectives 1. Compare the overall cell structure of prokaryotes and eukaryotes. 2. Describe taxonomic classification and use scientific nomenclature to accurately record the names of microorganisms. 3. Describe the Gram stain procedure and what is happening with the bacteria at each step. 4. Outline the factors affecting microbial growth and growth patterns. 5. Define the terms cocci, bacilli, pleomorphic, spirochete, flagella, pili, endospores, and capsules, microbiome, and biofilm. record the names of microorganisms accurately  3 Domain Classification Scheme Anderson, D. et al. Nestor’s Microbiology: A Human Perspective. 8th ed. 2016. p 239., accessed 6/13/17  Micro world Viruses are the smallest infectious agents/particles – Viruses are true parasites, requiring host cells for replication. – The genome of viruses consists of either DNA or RNA. incapsulated in a protein shell with or without a lipid membrane envelope Bacteria are prokaryotic unicellular organisms – no nuclear membrane, mitochondria, Golgi bodies, and endoplasmic reticulum – reproduce by asexual division  Micro world Fungi are eukaryotic organisms – have a well-defined nucleus, mitochondria, Golgi bodies, and endoplasmic reticulum. – can exist either in a unicellular form (yeast) or in a filamentous form (mold) Parasites are complex microorganisms – classified as eukaryotic, some are unicellular, and others are multicellular Bacteria Bacteria are prokaryotic unicellular organisms no nuclear membrane, mitochondria, Golgi bodies, and endoplasmic reticulum reproduce by asexual division  Major Characteristics of Eukaryotes and Prokaryotes Characteristic Eukaryote Prokaryote Major groups Algae, fungi, protozoa, Bacteria plants, animals Size (approximate) >5 μm 0.5-3.0 μm Nuclear Structures Nucleus Classic membrane No nuclear membrane Chromosomes Strands of DNA diploid Single, circular DNA haploid genome genome Cytoplasmic Structures Mitochondria Present Absent Golgi bodies Present Absent Endoplasmic reticulum Present Absent Ribosomes (sedimentation 80S (60S + 40S) 70S (50S + 30S) coefficient) Cytoplasmic membrane Contains sterols Does not contain sterols (except mycoplasma) Cell wall Present for fungi; otherwise Complex structure containing protein and absent peptidoglycan. May contain polysaccharides, teichoic acid, lipopolysaccharide Reproduction Sexual and asexual Asexual (binary fission) Movement Complex flagellum, if present Simple flagellum, if present Electron transport (ATP Mitochondria Cytoplasmic membrane production) Domain: highest level, distinguished by molecular analysis Phylum: group of similar classes Class: group of similar orders Order: group of similar families Family: made up of related genera Genus: consists of species that differ from each other in certain ways but are related Species: a population of cells with similar characteristics (biochemically the same, shape, gram stain, oxygen requirements, etc.)  Scientific Nomenclature Organisms are named according to scientific nomenclature - each organism has 2 names - genus is the first name and is always capitalized - species is the second name and is never capitalized - genus and species are in italics OR underlined, not both Example: Staphylococcus aureus OR Staphylococcus aureus Scientific Nomenclature slide is important to remember for your Microbiology Diary assignment.  What is a strain? A strain is a genetic variant or subtype of a microorganism A particular strain of bacteria can be distinguished using antibodies to detect characteristic antigens on the bacteria (serotyping). – S. aureus strain UU856 is resistant to methicillin – E. coli serotype O157:H7 is responsible for hemorrhagic colitis  What is an isolate? Colonies of bacteria are growing on plated media They come from a specific specimen sent to the lab. An "isolate" is a pure culture The isolate of S. aureus from the patient of bacteria, usually obtained by wound culture has a gold or yellow color. sub-culturing a single colony grown from a speciment Dijkshoorn et al., 2000; Tenover et al., 1995 Macroscopic and Microscopic Distinction of Bacteria Form of bacterial colony (e.g., color, Marcoscopic size, shape, and smell) appearance Ability to resist certain antibiotics Ferment specific sugars Microscopic Shape (cocci, rods, appearance curved, or spiral) Gram stain Ferment-specific  Bacterial Morphology Cocci or spherical - diplococci - streptococci (chains) - staphylococci (groups) Bacilli or rods - regular - branching - palisading - pleomorphic (many shapes) Spirochetes or helical Figure 1-05 Diagram of the microscopic shapes and arrangements of bacteria. Mahon: Textbook of Diagnostic Microbiology, 5th ed. Accessed 6/14/17  Bacterial cell wall Murray, et al. Medical Microbiology, 9th ed. Accessed 6/20/20  Bacterial cell wall Murray, et al. Medical Microbiology, 9th ed. Accessed 6/20/20  Gram Negative Gram Positive FIGURE 12-2 Comparison of Gram-positive and Gram-negative bacterial cell walls. Murray, et al. Medical Microbiology, 9th ed. Accessed 7/20/20  Cell Walls of Bacteria Gram Positive bacteria Gram Negative Bacteria Thick peptidoglycan Thin peptidoglycan No lipopolysaccharide layer Outer lipopolysaccharide layer Teichoic acid present No teichoic acid Example: Staphylococcus Example: Pseudomonas Take to Exam!  Cell Walls of Bacteria Acid Fast No Cell Wall In addition to Example: Mycoplasma peptidoglycan, the outer membrane of the acid- fast cell wall contains glycolipids (mycolic acids)  Waxy layer over gram positive structure Example: Mycobacterium  Bacteria growth https://phoenixlab.com/did-you-know-urine-culture-se http://www.bacteriainphotos.com/Streptococcus%20pyogenes.htmln sitivity/  The Gram Stain Gram stain is a rapid test that allows to distinguish between the two major classes of bacteria Gram positive: Purple Gram negative: Red/pink Reagents: 1. crystal violet 2. iodine 3. alcohol or acetone alcohol 4. safranin  Gram Stain Procedure Created with BioRender.com  Think P Purple POSITIVE https://upload.wikimedia.org/wikipedia/com mons/8/8f/Gram_stain_01.jpg, https://upload.wikimedia.org/wikipedia/commons/2/2e/Gonococcal_ urethritis_PHIL_4085_lores.jpg, https://labtestsonline.org/tests/gram-stain  Other Bacterial Structures Flagella – exterior protein filaments for movement Take to Exam! https://image.slidesharecdn.com/microbiologyintorduction-111211031828-phpapp02/95/introduction-to-medical-microbiology-38- 728.jpg?cb=1323574389, accessed 6/14/17  Other Bacterial Structures Pili or Fimbriae – protein fibers for attachment Not for locomotion! Take to Exam! FIGURE 3.41 Pili on an E. coli cell. Anderson, et al. Nester’s Microbiology: A Human Perspective, 8th ed. Accessed 6/14/17  Other Bacterial Structures Endospores - highly durable; resistant to heat, drying and chemicals - forms from vegetative cell when environment is hostile - returns to vegetative state (growing) when conditions favorable - remains dormant for a long time - SEEN IN ONLY SOME GRAM POSITIVE BACTERIA Murray, et al. Medical Microbiology, 9th ed. Accessed 6/20/20  Other Bacterial Structures Capsules - Usually made of polysaccharides - Prevent phagocytosis (a virulence factor) Take to Exam! https://pixnio.com/free-images/science/microscopy-images/anthrax-bacillus- anthracis/indian-ink-capsule-stain-is-useful-for-improving-visualization-of- encapsulated-bacillus-anthracis-in-clinica.jpg, accessed 7/20/20 https://upload.wikimedia.org/wikipedia/commons/6/6f/Cryptococcus_neoformans_using_a_light_India_ink_staining_preparation_ PHIL_3771_lores.jpg, accessed 7/20/20  Biofilm: an assemblage of microbial cells that adhering to a surface and enclosed in a matrix of primarily polysaccharide material. – Biofilms help make bacteria resistant to antimicrobial agents (e.g., antibiotics, disinfectants) and physical disruption Factors Affecting Microbial Growth Temperature - psychrophiles live optimally at 15ºC, but can grow at 0ºC - mesophiles live optimally at 30-35ºC - thermophiles survive in > 50-60ºC Take to Exam! Temperature Growth Profiles Figure 4.1 Typical growth rates of different types of microorganisms in response to temperature. Tortora. Microbiology, 12th ed. http://web2.mendelu.cz/af_291_projekty2/vseo/files/191/13606.jpg Factors Affecting Microbial Growth Hydrogen Ion Concentration – how acidic or basic is the media?  Osmotic pressure Osmotic pressure – the pressure created by water moving across a membrane due to osmosis Fluid passes from environment of lower solute concentrate to one of higher solute concentrate Figure 4.18 The principle of osmosis. Tortora. Microbiology, 12th ed.  Chemicals required for bacteria growth Chemical Requirements - carbon, water, nitrogen, sulfur, phosphorus, trace elements (iron, potassium, etc.) Atmosphere Does it require oxygen or does oxygen kill the organism? Bacterial Growth Bacteria multiply by binary fission. Generation time: Time required for a cell to divide into two cells. Time in Hrs # of Cells 0 1 0.5 2 1 4 1.5 8 2 16 2.5 32 3 64 3.5 128 4 256 4.5 512 5 1024 5.5 2048 6 4096 10 1,048,576  Pattern of Microbial Growth # of viable c bacteria (log) b d a Time a. Lag phase: growth undetected b. Log or exponential phase: maximal growth c. Stationary phase: number of cells dying = number dividing d. Death phase: most cells are dying  Microbiome Microbiome: A community of microorganisms living in a particular environment The human microbiome is composed of bacteria, archaea, viruses and eukaryotic microbes that reside in and on our bodies. Microbes impact our physiology: – metabolic functions, – protect against pathogens, – educate the immune system  Thank you! If you have any questions, please email me