Introduction to Medical Microbiology (PM704) PDF

Introduction to Medical Microbiology (PM704) Dr: Omneya Helmy Course Coordinator Microbiology: The study of microscopic organisms, either unicellular or multicellular.  Medical Microbiology Infectious diseases that are of great actual or potential importance to...

Introduction to Medical Microbiology (PM704) Dr: Omneya Helmy Course Coordinator Microbiology: The study of microscopic organisms, either unicellular or multicellular.  Medical Microbiology Infectious diseases that are of great actual or potential importance to humans. The impact of these diseases upon health in Egypt and the world.  Why study Medical Microbiology??? It’s about time! It’s about time to learn about all types of major infectious diseases (bacterial, viral or fungal). It’s about time to know and understand how laboratory diagnosis of infectious diseases is carried out. It’s about time to know the different treatment strategies of infectious diseases (Antibiotics for bacteria, antivirals or antifungals). The choice of prescribing or not prescribing? In a community pharmacy or hospital pharmacy or any pharmaceutical field, you need to know the basics of infection control, antibiotic/ non-antibiotic intervention methods as well as patient advice. Medical Microbiology: Learn the basic concepts regarding medically important microorganisms: - Microscopy/ Shape - Culture characters - Biochemical activities - Antigenic characters - Pathogenesis and Virulence - Diagnosis - Treatment - Prevention Medical Microbiology: Learn the basic concepts regarding medically important microorganisms: - Microscopy/ Shape - Culture characters - How to - Biochemical activities “identify” - Antigenic characters - Pathogenesis and Virulence - Diagnosis - How to - Treatment “deal with” - Prevention Medical Microbiology (Bad organisms?) Bacteria, Viruses, Fungi and Protozoa Bacteria Virus Microbiology Protozoa Fungi (Parasites) Bacteria, Viruses, Fungi and Protozoa Bacteria Virus Tuberculosis Corona Typhoid fever Influenza Cholera Common Cold Diphtheria Microbiology HIV/AIDS Fungi Protozoa Tenia (ring worm) Malaria Candidiasis Amoeba Trypanosoma Toxoplasma  Course Outline Bacteriology Gram Positive Bacteria Gram Negative Bacteria - Cocci: Staphylococcus, Streptococcus - Cocci: Neisseria gonorrhoeae, Neisseria - Rods: Corynebacterium diphtheria, meningitides Listeria monocytogenes - Acinetobacter, Moraxella - Bacillus anthracis, Bacillus cereus - Rods: Enterobacteriaceae: Escherichia, - Clostridium tetani, Clostridium Klebsiella, Edwardsiella, Citrobacter, perfringens, Clostridium botulinum, Enterobacter, Yersinia Clostridium difficile - Salmonella, Shigella, Serratia, Proteus, Morganella, Providencia Acid Fact Bacteria - Pseudomonas - Mycobacterium tuberculosis, - Bordetella, Brucella, Francisella Mycobacterium leprae - Legionella, Pasteurella, Haemophilus - Vibrio spp., Campylobacter spp., Spirochetes Helicobacter spp., Bacteroids - Treponema, Borrelia, Leptospira Rickettsia, Chlamydiae, Mycoplasma Mycology (Fungi)  Virology - Introduction to Virology (Structure, replication, methods of viral culture) - DNA viruses (Herpes, Varicella Zoster, Epstein Barr, Cytomegalo, Molluscum Contagiosum, Smallpox, Papilloma viruses, Adenovirus). - RNA viruses (Polio, Rhino, Influenza, Parainfluenza, Respiratory Syncytial, Mumps, Measles, German Measles, Arboviruses, Corona, Rota, Rabies, HIV). - Hepatitis (A, B, C, D, E) Practical Medical Microbiology: - Microscopy/ Shape - Culture characters - How to identify - Biochemical activities - Antigenic characters - Pathogenies and Virulence - Diagnosis - Treatment - Prevention Practical Medical Microbiology: Spots - Microscopy/ Shape - Culture characters - Biochemical activities - Antigenic characters O-Ag H-Ag AH-Ag BH-Ag  Infection, Immunity, Pathogenesis/ Pathogenicity and virulence Infection: The invasion of the body by a disease-causing agent. Immunity: The reaction “resistance” of the host tissue to the infectious agents and its products (toxins). Pathogenicity: The ability of the microorganism to cause a disease. Pathogenesis: The process by which a disease is brought about (how a disease is developed). Virulence: is a pathogen or microbe's ability to infect or damage a host. It is a measure for the degree of pathogenicity. The determinants that confer on the bacterium the potential to cause harm are termed virulence factors. Virulence can be measured in terms of the number of microorganism or micrograms of toxin necessary to kill given animal hosts (LD50 = lethal dose 50 or dose the kills 50% of animals).  The relationships between bacteria and the host Commensalism The host does not benefit from the relationship but is unharmed. Symbiotic The host gains benefits from the microbe beside being unharmed (bacteria produce nutrients and vitamins for the host and break down harmful chemicals). The harmless bacteria that naturally colonize areas prevent access by pathogens, a feature often referred to as colonization resistance.  The relationships between bacteria and the host Parasitism The host is harmed by the relationship but the parasite gains. Opportunistic infections A bacterium which normally lives harmlessly with the host and is non- pathogenic because of a host's normally functioning immune system, may become pathogenic if the immune system is compromised in some way. Such organisms are termed opportunistic pathogens. A bacterial pathogen is simply a bacterium that causes harm to a host. The resident microflora (microbiota) The body is naturally colonized by a vast and complex microflora or microbiota, which consists mainly of bacteria. These bacteria are generally considered harmless and are found over the whole outer surface of the body and in much of the gastrointestinal tract, the urogenital tract, and the oropharynx.  Stages of Bacterial Pathogenesis 1- Transmission 2- Entry 3- Attachment 4- Evasion of host defenses 5- Multiplication/ Colonization 6- Cause of damage 7- Release and spread  1- Transmission of bacteria Bacteria may be transmitted to a new host in two different ways: A. Direct spread to the host from the microbial source, for example: 1- Direct contact (STDs). 2- Droplet infection. 3- Contact with soil or dirt. 4- Transplacental. B. Indirect spread when a secondary inanimate microbial source is involved in the transmission of microbes to a new host. 1- Air-borne. 2- Fomite-borne. 3- Vehicle-borne. 4- Vector-borne (Biological or mechanical).  2- Entry The portals of entry for pathogens are: A. Mucous membranes (Respiratory, GIT (pH?), Genitourinary, Conjunctiva). B. Skin (Openings in the hair follicles or sweat gland ducts). C. Parenteral route (Punctures, injections, bites, cuts, wounds, surgery, and splitting of the skin or mucous membrane due to swelling or drying).  The Preferred Portal of Entry Microbes need to enter from the right portal; entering the body does not necessarily cause disease. Salmonella typhi: swallowed= typhoid, skin = no disease Streptococci: inhaled = pneumonia, swallowed= no disease Bacillus anthracis: can initiate disease from more than one portal of entry  3- Attachment and 4- Evasion of host defenses Surface-associated virulence factors A. Fimbriae , Pili (Adhesion, antiphagocytic) B. Flagella/ Axial filaments (Chemotaxis, penetration) C. Capsule/ Slime layer (Adhesion/ Protection against phagocytosis) D. Lipopolysaccharides (induction of inflammatory mediators). E. Outer membrane proteins (Adhesions, proteins sequestering iron) F. “Spores” 5- Multiplication/ Colonization The ability of the organism to adhere to body surfaces, establish itself, and start multiplying to form colonies. Colonization protects microbes from the effect of body secretions or the intestinal peristaltic movement.  6- Damage to the host A- Direct Damage Microbes can cause direct damage as the pathogens use the host cell for nutrients and produce waste products. B- Using the Host's Nutrients: Siderophores Iron is required for the growth of most pathogenic bacteria. Most of the host iron is tightly bound to iron-transport proteins. To obtain free iron, some pathogens secrete proteins called siderophores which bind iron more tightly away from iron-transport proteins.  6- Damage to the host C- Invasion Tissue invasion: - directly through the tissue (tissue invasive) - via lymphatic channels to the blood stream, and then to other organs (e.g., brain or bones) Intracellular invasion: - inside phagocytic immune cells - inside epithelial cells  6- Damage to the host D- Other virulence factors: Toxins (Exotoxins and Endotoxins) Endotoxins Exotoxins Nature Lipopolysaccharide Protein Location Part of the cell wall Extracellular Production Gram -ve Gram –ve and Gram +ve Enzyme action No Yes Toxicity Less More  6- Damage to the host E- Other virulence factors: Enzymes The virulence of some bacteria is thought to be aided by the production of extracellular enzymes (exoenzymes) and related substances. Coagulases are bacterial enzymes that coagulate (clot) the fibrinogen into fibrin to protect the bacterium from phagocytosis and isolate it from other defenses of the host. Kinases break down fibrin digest clots and allow bacteria to move furthermore.(ex: Staphylokinase, Streptokinase), similarly: collagenases and keratinases. 43  7- Release and Spread A successful pathogen will be released from the host and enters another host.  Manifestations of disease Symptoms: subjective manifestations of a disease that are apparent only to the patient; pain, headache, dizziness, and fatigue. Signs: objective “evidence” of disease that can be observed or “measured” by others; swelling, rash, redness, and fever. Syndrome: a collection of symptoms and signs that collectively characterizes a particular disease or abnormal condition. Medical Microbiology