1- Bacterial cell structure.pdf

What is Microbiology? Dental Microbiology & Immunology...

What is Microbiology? Dental Microbiology & Immunology Learning Resources Microbiology in Dentistry? Recommended Books and Reference The study of organisms of The open environment in the human mouth is suited to MMIC 311 Review of Medical Microbiology and Immunology, latest Edition, Warren E. the growth of characteristic microorganisms found there. Levinson, Lange publication. microscopic size It provides a source of water and nutrients, as well as a Mims' Medical Microbiology, MOSBY Required Textbook Journal of Clinical Microbiology (JCM) publishes, ASM moderate temperature Journal of Medical Microbiology , Lippincott Williams & Wilkins, UK Dental caries and oral infections are caused by Microbes Essentials of Microbiology for.Electronic Materials, Web Sites etc Dental Invasive procedures….risk of infection, transmission, cardiac patients risk….etc. www.asmusa.org ( American Society for Microbiology) dental students. J.Bagg. T. W. www.cdc.gov ( Centers for Disease Control and Prevention) Macfarlane. I. R. Roxton and www.cdc.gov/ncidod/index.htm( CDC National Center for Infectious Improper dental work and microbes… e.g. root canal A. J. Smith Diseases) abscess… www.hpa.org.uk/ (Health protection agency) www.socgenmicrobiol.org.uk ( Society for General Microbiology) Oral microbes can spread to other body parts e.g., brain, www.who.int/home-page/( World Health Organization) heart or bone , causing serious infections and have MMI 2 MMI Other learning material such as computer programs and printouts.3 impact on systemic diseases e.g., diabetes millitus. Prokaryote Eukaryote Types of Microorganisms: Organisms are mainly divided into Examples Bacteria Fungi, plants, animals Prokaryotic Average size Smaller (0.2-2 µm in diameter) Larger (10-100 µm in diameter) Bacteria e.g., staph aureus 1. Prokaryotes “before nucleus” Nuclear membrane Absent (Neucleoid) Present (True Nucleus) - Mycoplasma (bacteria that lack a cell wall). Organisms that do not have a nucleus (DNA is not Chromosomes 1 (circular) >1 (linear) Eukaryotic Fungi (mycology) enclosed in a membrane) e.g. bacteria, … Extrachromosomal plasmid Usually present (additional fragment of DNA) Usually absent Ribosomes Smaller (70S) Larger (80S) Protozoa unicellular organisms e.g., amoeba feed on human intestine and cause diseases 2. Eukaryotes “true nucleus” Membrane-bound absent Present e.g. mitochondria organelles parasites (Worms) Organisms that contain a nucleus surrounded by a Cell wall containing Yes No nuclear membrane e.g. fungi, plants and animals peptidoglycans Viruses Not a Cell ((DNA or RNA & protein coat)) Reproduction Asexual (binary fission) Sexual and asexual (budding (a grey area between living and non-living) or mitosis) e.g., Corona Virus, HIV Respiration Via cytoplasmic membrane Via mitochondria 6 Oral bacterial Flora What are Bacteria ? Medically important Bacteria Bacteria are single celled (unicellular) microbes. Medically important bacteria can grow in the human free-living prokaryotic organisms. body temperature: Some Bacteria are pathogenic and are important (cause of disease) to the human body systems  The genetic information is contained in a single loop of DNA suspended in a jelly- like substance called cytoplasm. Many bacteria live with us as normal flora on the skin, nose, mouth or intestine, and counts more Bacteria Grow independently than human cells. Investigated in the laboratory by culture media which Normal flora is very beneficial in its original body provide nutrients “food” for bacteria, at 37oC site e.g. mechanical barrier against harmful bacteria can be seen under light microscope pathogens and help in digestion…etc. Normal flora may also cause illness if transferred to abnormal site… e.g. oral to blood stream. The human body, which contains about 1013 cells, routinely harbours about 1014 bacteria. NORMALLY, No bacteria in Sterile body sites e.g. blood, heart, bone, CSF..  (Poor hygiene, accumulation of bacteria) What are bacteria? Name (Nomenclature) Shapes and arrangements Bacteria are single celled (unicellular) microbes. 3 basic shapes determined by the rigid bacterial cell wall: All organisms have a name consisting of two parts: the Genus followed by the species The genetic information is contained in a single Staphylococcus aureus loop of DNA suspended in a jelly-like substance called cytoplasm. Some bacteria have an extra circle of genetic Escherichia coli material called: a plasmid→ contains genes that give the bacterium some advantage over other bacteria → e.g. a gene that makes the bacterium Bacterial Size: The diameter of most cocci are about 1.0μm Most rods are about 2-3μm in length and 0.3- 0.5μm (diameter) resistant to a certain antibiotic. Bacteria seen under light microscope Basic Bacterial Structures Cell Wall Is the outer covering layer of the bacterial cell (support the cytoplasmic Structures found in membrane). all bacteria ’ Rigid structure that maintains the bacterial shape ’ Common of all Bacteria (except Mycoplasma) (Invariant structures) It is composed of : basic layer & additional layer Streptococcus Cell wall Basic layer (peptidoglycan ) Cell membrane - Formed of carbohydrate cross-linked by peptide chains(protein) E. coli Ribosomes - It is responsible for rigidity of cell wall. - Good target for antibacterial drugs (antibiotics). why? Nucleoid - Peptidoglycan is unique to bacterial cells (not found in human) e.g. penicillins and cephalosporins, inhibit its synthesis. Borrelia Compositions of the Cell Wall: Compositions of the cell wall: - Basic layer (peptidoglycan ) Invariant structure Bacteria are classified according to thickness of peptidoglycan layer into - Additional layer 2. Cell membrane two main groups: Other names: ’ Bacteria have Thick peptidoglycan, ’ Bacteria have Thin peptidoglycan, forms 80% of Cell wall forms 20% of Cell wall - In Gram +ve bacteria it is formed of teichoic acid. Cytoplasmic membrane, Plasma membrane This composition determines the cell’s reaction to Gram stain: ----------------------------------------------------------------- It is a thin elastic structure 5 – 10 µm thick - Gram –ve bacteria has outer membrane layer formed of: (e.microscope) ’ Thick peptidoglycan ’ Thin peptidoglycan  retain Gram stain  loose the Gram stain (lipopolysaccharide=endotoxin) and protein Composed of a phospholipid bilayer This outer layer protect peptidoglycan & prevents the permeation of many  Gram +ve bacteria  Gram –ve bacteria. antibiotics makes Gram-negative bacteria more resistant to antibiotics than Gram-positive ones Example: Vancomycin antibiotic can NOT cross this outer membrane(lipopolysaccharide) So, Gram-negative bacteria can cause serious diseases in humans. Nosocomial “hospital” infections caused by Gram-negative bacilli (GNB) are the most challenging issue for health care professionals due to resistance to antibiotics  Invariant structure Invariant structures Invariant structures 2. Cell membrane Ribosomes: 4. Nucleoid. function as the site of protein synthesis. Main Functions:. Bacterial Ribosomes exist as 70s with 30s and 50s subunits It is the location where the genetic material is found Selective transport; restricting the kind and Note: ( Human’s are 80s) different from bacterial ribosomes amount of molecules that enter and leave So, Selective site for many antibacterial drugs (Antibiotics) that affect bacterial Composed of a simple single , circular double stranded but not human cell. DNA molecule (Chromosome).unbound to proteins the cell. Examples: Aminoglycosides antibiotics target 30s Macrolides antibiotics target 50s Quinolones (2nd line antibiotics) inhibit bacterial It provides enzymes important for cell e.g. nucleic acid synthesis (disrupting DNA gyrase cell wall synthesis, respiration. enzyme) Plasmids: These are extra-chromosomal DNA molecules They carry small number of genes, notably some associated with antibiotic resistance No nuclear membrane or nucleolus Variant structures Variant structures Variant structures→ 3. Pili (Fimbriae) 1. Capsule 2. Flagella It is a gelatinous layer outside the cell wall of some Some bacteria are motile, others are not. Pili: filamentous structures extending from the species of bacteria. Flagella → the organ of motility in motile bacteria surface of most bacterial pathogens. Function: Important virulence factor → protect bacteria from Shorter and thinner than flagella; NOT INVOLVED phagocytosis IN MOTILITY  help bacteria in adherence Function: Organ of adhesion (attachment of the attachment to human tissues. bacteria to host tissues) Variant structures → 4. Bacterial endospores BACTERIAL PHYSIOLOGY BACTERIAL HABITATE In case of environmental stress → Some bacteria can form & PATHOGENESIS (1) Live on inanimate materials such as surfaces, water, dust air, a highly resistant dormant phase called endospores dead bodies, and decaying organic matter. BACTERIAL PHYSIOLOGY Function: ensure the survival of a bacterium through Habitat (2) live on or in the body of living creature.These are classified into: periods of environmental stress e.g. high temperature, Nutrition & Oxygen requirement a) Commensals (normal flora): They do not cause disease in normal conditions, but can cause disease when the resistance of the body drying, radiation and many damaging chemicals Replication (Immunity) is decreased e.g. AIDS and Leukemia Opportunistic infection OR if transferred to abnormal site e.g. from skin to bloodstream. Endospores can survive for very long periods of time.. Endospores can germinate (turn back into a growing BACTERIAL PATHOGENESIS bacteria) many years after formation when the conditions Products & Virulence factors a) Pathogenic: cause disease in healthy host regardless of the host's resident microbiota or immune system (Not Normal flora) are favorabl e.g...bloodstream wound Clostridium tetani Endospores are difficult to kill.. E.g. Alcohol Antibiotics  Bacterial Nutrition & Growth Gaseous Requirements Bacterial replication Normal According to oxygen requirements bacteria are Bacteria reproduce by binary fission, Flora Medically important bacteria are Heterotrophic bacteria: classified into 4 groups: resulting in two genetically identical daughter cells. require complex preformed organic substances e.g. sugars, protein 1- Obilgatory aerobes: can not grow except in Logarithmic growth presence of oxygen e.g Mycobacterium tuberculosis. Many bacteria secrete enzymes to breakdown extracellular nutrient material into simpler molecules, then transported & utilized by bacteria 2- Obligatory anaerobes: Can grow only in complete absence of oxygen e.g. clostridia Optimum growth occurs at 37C i.e. the normal body temperature. (Clostridium Tetani). 3- Facultative anaerobes : can grow in presence Most pathogenic species of bacteria can grow at a narrow range of and in absence of oxygen e.g. Staphylococci & PH 7.2-7.6 Escherichia coli. Number of BUT few bacteria e.g. lactobacilli, S. mutans (tooth decay) can survive cells 1 2 4 8 16 Exponenti in the acidic environment (PH 4) which is very bad for teeth health 4-Microaerophilic: grow best in presence of minimum amount of oxygen: e.g. Campylobacter al 20 21 22 23 24 jejuni & Corynebacterium acne. BACTERIAL PRODUCTS 3-Bacterial Toxins (1) Bacterial pigments Exotoxin Endotoxin Bacterial Pathogenesis Antimicrobials agents - colored substances produced by some bacteria. Toxicity - Highly toxic - Less toxic Antigenicity - Strong antigenic - Weak antigenic ’ * Factors that Govern Disease Production: - Endopigments: localized to bacteria. Exopigments: excreted outside bacteria - play a role in respiration, some have anti bacterial actions Specificity - Specific in action - Non specific The outcome of infection depends on interactions between: An antimicrobial is an agent that kills microorganisms Nature - Protein - Lipopolysaccharides ’ Microbial factors (pathogenicity and virulence). or stops their growth Effect of heat - Thermolabile (damaged by heat) - Thermostable ’ Host resistance factors (natural and acquired immunity). (2) Bacterial Enzymes Protein catalysts produced by some bacteria to mediate bacterial activities Pathogenicity: Example -Mainly by Gram +ve bacteria - Gram –ve bacteria Functions of bacterial enzymes: is ability of an organism to cause disease -Diphtheria exotoxin. - Salmonella a- Metabolism e.g. lipase enzyme. b- Respiration e.g. cytochrome enzyme. Virulence factors: c- DNA replication. Some bacteria have some virulence factors d- virulence factors: e.g. (Hyaluronidase tissue destruction), (Coagulase protection -structures: e.g. ? from immune cells). (Haemolysin :lysis of RBCs) …etc. -products: certain enzymes or toxins e.g.? Antibiotics Infection Vs. Disease:  Infection: a condition in which pathogenic microbes penetrate host ’ Antibiotics are = antibacterial drugs How to treat bacterial infection defenses, enter tissues & multiply Act only on bacterial infections identified by specimen culture After appropriate specimen collection from patients with then, Antibiotics are prescribed according to sensitivity tests  Disease: damage of a tissue or organ caused by microbes or their suspected bacterial infections: products(enzymes, toxin) ’ Each antibiotic has specific target in the bacterial cell structures So, Human safe (do not attack human cell) Mild cases can wait for culture result, then treated ’ Classified into: accordingly…. Broad-spectrum antibiotics: Outpatients with an urgent severe infection, suspected CNS active against both Gram-positive and Gram-negative bacteria+/- infections or those who need admission… should start anaerobes. E.g. Quinolones antibiotic (s) according to the clinical assessment (either Narrow spectrum antibiotics: Broad spectrum or narrow spectrum antibiotic), which is More specific in their course and act against only certain bacteria then tailored according to the culture results e.g. penicillin  Mode of transmission Airborne (through inhalation) Infectious nuclei remain suspended in air because 5 μm in diameter So, Particles heavy, do not remain suspended in the air Touching wound or burn SOME ORGANISMS MAY BE TRANSMITTED THROUGH MORE Sneezing, coughing, talking → Spray of large droplets travel short distance→ THAN ONE OF THESE ROUTES Droplets rapidly settle out on horizontal surfaces OR deposited on susceptible facing person's conjunctivae, nasal membranes or mouth. Dr Ghada, Faculty of Nursing, Taibah University EXAMPLE: Corona virus Infections Local Vs. Systemic Infection An infection does not always cause acute / apparent illness. (Example of acute infection ) Periods of infectious diseases 1. Incubation period Streptococcus pyogenes infection Subclinical infection Local Infection Time between the start of infection and the appearance of the first No symptoms or Symptoms very mild to be noticed (carrier) signs or symptoms An infection that is limited to a small area of the Acute infection different according to pathogen from days e.g. influenza to months body e.g. dental abcess e.g. HIV The onset of Symptoms and disease appearance Chronic infection 2. Period of illness Some Infections result in long-term or lifelong disease Systemic infection Following incubation, individual experiences signs and symptoms of e.g. HIV, Viral Hepatitis C An infection that is found throughout the body the disease (infection that is in the bloodstream) e.g. HIV Latent infection Causative agent under immunity control→ remains inactive 3. Period of convalescence can be reactivated and symptomatic in immune disease Period of recovery Example: Herpes , Tubercolosis 56 57 58 Neisseria meningitidis Gram stain classify bacteria according to thickness of peptidoglycan layer of cell wall into: (example CNS infection) Classification of Gram positive bacteria Bacteria Which can be cocci OR bacilli according to thickness of peptidoglycan layer of cell wall Gram negative bacteria Also, cocci OR bacilli  After Gram stain, Bacteria are seen under Gram Positive Bacilli Gram Negative Cocci Gram Positive cocci light microscope which magnifies x 1000 Examples (genus): Classified into 2 genus: Examples : Lactobacillus species Staphylococci Neisseria Clostridium e.g. Clostridium difficile e.g. Staphylococcus aureus e.g., Neisseria meningitidis Corynebacterium e.g., Neisseria gonorrhea Streptococci e.g. Streptococcus pyogenes Streptococcus viridians group Gram Negative Bacilli Examples: E. coli salmonella vibrio cholera Pseudomonas aeruginosa