Bacteria PDF: Medical Microbiology Lecture Notes

WE MAKE DOCTORS BACTERIA Arturo Ochoa, M.D.  I. Outline the main II. Identify and characteristics of associate virulence the bacterial factors from involved structure and in disease bacterial physiology as pathogenesis a...

WE MAKE DOCTORS BACTERIA Arturo Ochoa, M.D.  I. Outline the main II. Identify and characteristics of associate virulence the bacterial factors from involved structure and in disease bacterial physiology as pathogenesis and prokaryotes outcome III. Describe and IV. Demonstrate the identify the main mechanisms of morphologic and genetic exchange biochemical testing that confer characteristics taken adaptation to into consideration for bacterial cells the classification of prokaryotic cells (bacteria)  Definition Bacteria constitute a domain of unicellular prokaryotes that don’t have a nucleus. They can be classified as pathogens or commensals. Commensals Commensals are microorganisms living on or within humans. Resident Flora: Skin: Staphylococcus epidermidis Nasal: Staphylococcus epidermidis Oropharyngeal: Viridans group streptococci Dental Plaques: Streptococcus mutans Gut: Escherichia Coli and Bacterioides Vaginal: Lactobacillus acidophilus Lung: Neisseria catarrhalis, alpha-hemolytic streptococci, staphylococci, nonpathogenic corynebacteria, Candida albicans Transient Flora Pathogens Facultative Pathogens: Are capable of survival outside of a host Only cause disease in susceptible hosts Opportunistic pathogens Obligate Pathogens: Can only replicate inside the cells of a host If a sufficient amount of bacteria is ingested, it can also affect immunocompetent patients Bacterial Structure Cell Wall Peptidoglycan, Mycolic acid in acid-fast bacteria Peptide side chains crosslinked by transpeptidase Muramic acid Gram-positive contain lipoteichoic acid Outer Membrane (Gram -) Outer layer: Contains endotoxin (LPS/LOS) Inner layer: Composed of phospholipids Bacterial Structure Cytoplasmic Membrane Bilayer of phospholipids contains proteins and enzymes Bacterial Capsule Organized layer of polysaccharides Highly charged, hydrophilic Rarely contains proteins Glycocalix Loose polysaccharide layer Bacterial Structure Periplasm (Gram -) Space between the outer and cytoplasmic membrane Contains peptidoglycan and beta-lactamase Flagellum Proteins Pilus (fimbria) Glycoproteins Endospores Coating layer of keratin, dipicolinic acid, peptidoglycan, DNA Bacterial Structure Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Bacterial Structure Richard, Goering., Dockrell, Hazel., Zuckerman, Mark., Chiodini, Peter.(2024) Mims' Medical Microbiology and Immunology, Elsevier. 7th Ed. Chapter 2, pages 6-26, Retrieved from ClinicalKey Form Bacilli: rod-shaped bacteria Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Form Cocci: sphere-shaped bacteria Staphylococci Streptococci Diplococci Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Form Coccobacilli: very short rods almost resembling a cocci (2020), Coccobacilus Conundrum, Clinical Microbiology Newsletter, 42 (11) 93-94. Retrieved from ClinicalKey. Figure 2. Form Spirochetes: Spiral-shaped organisms, contain axial fillaments (endoflagella), poorly visible on gram-stain. Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Cell Wall Structure Gram staining is a standard microbiological laboratory method used to differentiate bacteria based on their cell wall structure. Gram-positive bacteria: violet to blue appearance Gram-negative bacteria: pink appearance Atypical bacteria: do not Gram stain Lack of cell wall Atypical cell wall composition Very thin wall Hans Verstraelen MD, MPH, Rita Verhelst PhD, Kristien Roelens MD, Geert Claeys MD, PhD, Steven Weyers MD, Ellen De Backer BSc, Mario Vaneechoutte PhD, Marleen Temmerman MD, MPH, PhD, (2007), Modified classification of Gram-stained vaginal smears to predict spontaneous preterm birth: a prospective cohort study, American Journal of Obstetrics and Gynecology, 196 (6), 528, Retrieved from ClinicalKey) Cell Wall Structure Acid-fasting staining is a method that stains mycolic acid. Ziehl-Neelsen stain produces red staining Auramine-rhodamine stain produces a yellowish-red staining Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Qinglian Hu, Wen Li, Xiurong Hu, Qida Hu, Jie Shen, Xue Jin, Jun Zhou, Guping Tang, and Paul K. Chu, (2012), Synergistic treatment of ovarian cancer by co-delivery of survivin shRNA and paclitaxel via supramolecular micellar assembly, Biomaterials, 33 (27), 6580-6591, Retrieved from ClinicalKey Capsule A polysaccharide structure located outside the cell membranes of certain bacteria. Antiphagocytic by impeding opsonization. Most important encapsulated bacteria: Group B Streptococcus Streptococcus pneumoniae Haemophilus influenzae type b Neisseria meningitidis E. coli Salmonella Klebsiella Pneumoniae Pseudomonas aeruginosa Intracellular bacteria Obligate intracellular bacteria Cannot produce ATP outside of host cell Facultative intracellular bacteria Can produce ATP outside of host cell Oxygen Environment Anaerobic Bacteria Obligate anaerobe: Occur in the gut flora, Susceptible to damage due to lack of enzymes, Often produce foul smell, Difficult to culture Facultative anaerobe: Can use oxygen for ATP generation but may switch to anaerobic metabolism Aerobic Bacteria Require oxygen to produce ATP Grow optimally under atmospheric oxygen levels Hemolysis Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Antibiotic resistance testing Antibiotic sensitivity testing Reports the sensitivity of a pathogen as “susceptible”, “intermediate”, or “resistant”. Can be used to tailor antibiotic therapy Antibiogram Collates the results of antibiotic sensitivity tests in a hospital or region to predict potential local susceptibility of a bacterial pathogen to various antibiotics. Enzymes Catalase An enzyme that visibly breaks down hydrogen peroxide into water and oxygen, preventing its breakdown into microbiocidal substances. Coagulase An enzyme that converts fibrinogen into fibrin Oxidase (cytochrome c oxidase) An enzyme that catalyzes the donation of hydrogen atoms to oxygen, forming water or hydrogen peroxide Enzymes Urease An enzyme that hydrolyzes urea to ammonia and carbon dioxide, which increases pH Penicillin-binding proteins (PBPs) Involved in cell wall synthesis Bacterial DNA structures Plasmids: Bacterial nonchromosomal DNA fragments that replicate independently from chromosomal replication Integrons: These sequences integrate to chromosomal bacterial DNA via integrase Pathogenicity islands: Associated with virulence factors such as adhesins and toxins Genetic variability of bacteria Intracellular mechanisms Exchange of larger gene segments between bacteria that have similar gene sequence via homologus recombination Intercellular mechanisms Bacterial transformation Bacterial conjugation Bacterial transduction Bacterial transposition Genetic variability of bacteria Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Genetic variability of bacteria Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Genetic variability of bacteria Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Genetic variability of bacteria Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Genetic variability of bacteria Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Bacterial Infection and Disease Bacteria use different mechanisms to colonize, invade, and infect the host in order to survive. Colonization Lipoteichoic acid (LTA) cell wall component anchored in cytoplasmic membrane and acts as antigen Bacterial adhesins Biofilm a heterogenous aggregation of bacteria held together by extracellular polymeric substances (EPS) Flagella Perithrichous flagella: Flagella around the bacterium Lophotrichous flagella: Several flagella at one pole Polar flagella: One flagellum a one of the bacterial poles Bacterial Infection and Disease Avoiding the immune system Bacterial capsule IgA protease cleaves mucosal IgA Protein A binds to Fc region mainly of IgG to prevent Ig binding, inhibiting phagocytosis, complement fixation, and antibody dependent killing M protein prevents opsonization by C3b Bacterial Infection and Disease Bacterial Nutrition Secretion of siderophores Antigenic Variation Pili, Capsule and Flagella expression, Antigenic Drift Intracellular survival Inhibition of phagosome-lysosome fusion, Exiting phagosomes before fusion, Invasins. Bacterial Infection and Disease Type III secretion system Injectisome a bacterial appendage that connects bacteria and immune cells and delivers bacterial toxins directly into the cell Inflammatory response Bacteria-specific antibodies Immune complexes Peptidoglycan and teichoic acid Bacterial Toxins Likewise, virulence factors Endotoxins Present in Gram-Negative Bacteria Genetic information is encoded in bacterial chromosome Released by bacterial lysis and exocytosis LPS containing Lipid A (Toxicogenic component) and O antigen (Immunogenic component) Heat stable with low antigenicity Bacterial Toxins Endotoxins Activate macrophages via CD14/TLR4 receptors, releasing TNF-a, Nitric oxide, IL-1, IL-6. Activation of the complement system Activation of the coagulation cascade Commonly causes fever, flu-like symptoms, DIC, Septic Shock Low Toxicity No toxoid formation Bacterial Toxins Exotoxins Both gram +/- organisms Genetic information is encoded in the plasmid or bacteriophage that is taken up by the bacterium It is actively released by living bacteria Polypeptides in the cytoplasm which consist of two components Heat-labile with exceptions and high antigenicity producing antitoxin antibodies Bacterial Toxins Exotoxin Different mechanisms of action for each toxin such as AB toxins Commonly causes tissue and cell necrosis, dehydration, and usually no fever High toxicity Forms toxoid that can be modified into a toxoid vaccine Image: AMBOSS. (2024) General Bacteriology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/In0Yug?q=bacteria Drug Resistance Chromosomal Chromosomal mutations that alter the binding site for the drug or affect the permeability of the drug Non-Chromosomal Resistance plasmid Resistance transfer factor (R factor) Resistance determinant (r) Beta-lactamase Acetyltransferase Oncogenesis Helicobacter pylori (H. pylori) Gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma Salmonella typhi Gallbladder cancer Streptococcus gallolyticus Colorectal cancer Fusobacterium nucleatum Colorectal cancer Chlamydia trachomatis Cervical cancer (synergistic with human papillomavirus HPV) References Amboss. (2024). General Bacteriology. Retrieved November 4, 2024, from https://next.amboss.com/us/article/In0Yug?q=bacteria Richard, Goering., Dockrell, Hazel., Zuckerman, Mark., Chiodini, Peter.(2024) Mims' Medical Microbiology and Immunology, Elsevier. 7th Ed. Chapter 2, pages 6-26.