A.- INTRODUCTION. BACT-FUNGI-VIRUS. PHYSICAL AND CHEMICAL FACTORS.pdf

PAHOLOGY PRODUCED BY MICROORGANIMS Importance of infectious diseases in Public Health  According to World Health Organization (WHO) the infectious diseases produce almost the forth part of the deaths in the world.  90 % of the deceases due to: VIH/AIDS, tuberculosis, diarrhea, malaria, measl...

PAHOLOGY PRODUCED BY MICROORGANIMS Importance of infectious diseases in Public Health  According to World Health Organization (WHO) the infectious diseases produce almost the forth part of the deaths in the world.  90 % of the deceases due to: VIH/AIDS, tuberculosis, diarrhea, malaria, measles and pneumonia.  Importance of emerging and re-emerging infectious diseases. Or resistant to antibiotics: SARS, Creuzfeldt-Jakob, dengue, Ébola, cholerae, Chicungunya fever Influential factors: environmental and human activities richness and poorness, globalization (movement of persons and goods) basic sanitation and human congestion social exclusion, etc… Discovery: Relation between microorganisms and infeccious diseases: Koch (1876) y Pasteur (1877). Discovery of Bacillus anthracis, Mycobacterium tuberculosis, Vibrio cholerae, Corynebacterium diphtheriadae,.... Koch's Postulates Established “scientific rules” to show a cause and effect relationship between a microbe and a disease:  Koch's Postulates Four criteria that were established by Robert Koch to identify the causative agent of a particular disease, these include: 1. The microorganism or other pathogen must be present in all cases of the disease 2. The pathogen can be isolated from the diseased host and grown in pure culture 3. The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal 4. The pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen Eukaryotes, DNA is organized into chromosomes and into the nucleus. They have membrabous irganelles such a mithocondria or Golgi. Prokaryotic cells lack a nucleus and membranous organelles and DNA is a single loop. Virus: no cells. Morphology and structure of the main microorganisms. Bacteriae, Virus, Fungi. Bacterial morphology and structure EXTERNAL STRUCTURES FIMBRAE OR PILI Made of protein Function: Enable cell to adhere to surfaces (cells) or cell receptors. Pili sexual function: to join bacterial cells for partial DNA transfer called conjugation FLAGELLA Structure: Flagelar filament Hook Basal body Function: motility Location: Monotrichous – polar, one flagellum Lophotrichous – tufts of flagella at one or both ends Amphitricous – one flagellum at each end Peritrichous – (peri=around) flagella evenly spread on surface  GLUCOCALIX Slime layer - loosely organized and attached Capsule - highly organized, tightly attached (dense) Functions: Escapes from phagocytosis, contributing to pathogenicity. Adhesion: formation of biofilms CELL WALL Composition: Peptidoglycan. Structure: Gram positive Thick Layer of peptidoglycan + techoic acid. Gram negative: Thin layer of peptidoglycan PLASMATIC MEMBRANE  CYTOPLASM RIBOSOMES 70S 30S + 1RNAr 50S + 2RNAr. INCLUSIONS AND GRANULES.- Intracellular storage bodies (glycogen, poly b- hydroxybutyrate, gas vesicles, sulfur and phosphate granules, particles of iron oxide). NUCLEIC ACID MATERIAL “one chromosome” plasmid ENDOSPORES Resistence forms produced by some Gram positive  BACTERIA WITH ENDOSPORES CAUSING DISEASES Bacillus anthracis (Anthrax), Clostridium tetanii (Tetanus), Clostridium perfringens (Gas gangrene), Clostridium botulinum (Botulisme).  Size Bacterial morphologies  Spherical: Cocci Bacilli  Corkscrew form:  “vibrio”  Helical  Filamentous  Spirochetes  Types of bacterial diseases a.- Intoxication b.-Infections c. Intoxication and infection Pathogenic mechanisms Stickiness.- Adherence factors. Invasiviness.- mocrobian products causing fever, inflammation, … Toxigenicity.- Toxigenic factors: – citocins, – neurotoxins, – enterotoxins. FUNGI Differences respect to the other eukaryotic cells Wall cell cellulose chitin (polymer of acetilglucosamine) combination Plasma membrane ergosterol  Types - Yeast or unicellular fungi Some species grow as unicellular yeasts that reproduce by budding or gemmation - Filamentous fungi: Filamentous cells: Hyphae Set or hyphal group: Mycelium. * Moulds. * Rest of fungi. Reproduction 1.- Asexual Budding or gemmation (1) Conjugation (2) Asexual spores by mitosis (3) 2.- Sexual Sexual spores by meiosis 1.- Filamentous fungi - Imperfect fungi or Deuteromycota(Moulds) - Ascomycota. Ascocarpo (ascospores) - Basidiomycota. Basidiocarpo (basidiospores) 2.- Yeast 3.- Dimorphic fungi Yeast phase and miceliar phase  Types of fungal diseases a.- Intoxication (micotoxicosis y micetismes). b.-Infections (mycosis). c. Hipersensibility (allergies). a.- Intoxications Muscarine (hallucinogenic). Faloidine and amanitine (very dangerous:). Ergotamine (in rye, very toxic) Aflatoxin (contaminate grains, very toxic) b.- Mycosis and the way of transmission - Superficial and cutaneous.- Involving the outter layer of the statum corneum of the skin (epidermis and dermis, nails and hair). By direct contact. - Subcutaneous.- Affecting subcutaneous tissues, muscles, and lymphatic tissue. By injuriesor wounds. - Systemic.- Disseminated infection from the respiratory tract to the rest of the body (brain, heart, liver, spleen, kidneys…). By inhalation. - Opportunistic.- Require a compromised host, causing deep mycosis invading via the respiratory tract, alimentary tract or intravascular devices By autoinfection and fómites. Viral Morphology and Structure  DEFINITION  Submicroscopic entity consisting of a single nucleic acid surrounded by a protein coat (capsid) and capable of replication only within the living cells of bacteria, animals or plants.  Obligate intracellular parasite: Not made of cells Can not reproduce on their own Do not grow or undergo division Do not transform energy Lack machinery for protein synthesis SHAPES STRUCTURE Nucleic Acid Capsid Other Elements  Nucleic acid Types (one or several in one virus): DNA single-stranded DNA double-stranded RNA single-stranded RNA double-stranded Both circular or linear…. The RNA can be: - Positive sense RNA works as mRNA - Negative sense RNA must be converted to positive-sense RNA by an RNA-dependent polymerase, before translation.  Capsid It is formed from identical protein subunitscalled capsomeres. Helical Polyhedral Spherical Bacteriophage  Envelope: Acquired from host cell during viral replication or release; envelope is a portion of membrane system of host.  Effects Citocide. Latent virus. Persistent virus. Transforming virus.  Types of infections - Lytic viral infections Cell died. - Persistent viral infections The cells are still alive. - Latent infection There is a period between the infection and the symptoms. - Oncogenic viruses Transformation into the chromosome cell - Benign, - Malignancy (cancer).  Strategies for virus survival Finding and getting into a host cell. As viruses are obligate parasites they must find the right type of cell for their replication, they must invade that cell and get their genome to the site of replication. Making virus protein. All viruses are parasites of translation. The virus must make mRNA (unless it has a + sense RNA genome already). Strategies must exist to synthesize mRNA. Making viral genomes. Many viral genomes are copied by the cell’s synthetic machinery in cooperation with viral proteins. Forming progeny virions. The virus genome, capsid (and envelope) proteins must be transported through the cell to the assembly site, and the correct information for assembly must be pre-programmed. Spread within and between hosts. To ensure survival the virus must propagate itself in new cells. Overcoming host defences. The host defends itself against “nonself” Viruses have evolved ways to fight back.  PRIONS - A prion is an infectious agents, specifically a protein in a misfolded form (losted the terciary structure). - Prions are not considered living organisms. - High power of association to hydrophilic proteins In plasmatic membranes. - The brain like a sponge due to the accumulation of prion proteins in neurons, where amyloid plaques are formed, which are caused by the accumulation of amyloid peptide, an essential protein for cellular functioning in the body, and that in the brain generates toxicity for nerve cells.  Types of prion diseases in humans Sporadic: Occurring spontaneously, without any known reason (most common) -Creutzfeldt-Jakob disease (progressive deterioration of mental function, leading to dementia, involuntary jerking of muscles (myoclonus), and staggering when walking -Fatal insomnia (interferes with sleep and leads to deterioration of mental function and loss of coordination) Familial: Genetic component -Familial Creutzfeldt-Jakob disease -Fatal familial insomnia -Gerstmann-Sträussler-Scheinker disease (loss of coordination followed by slow deterioration of mental function) -Diarrhea and autonomic neuropathy (affects nerves outside the brain, causing diarrhea and loss of feeling in the feet) Acquired: Acquired from contaminated material (uncommon) - Kuru (canibalism) PHYSICAL AND CHEMICAL FACTORS AFFECTING HOSPITAL ENVIRONMENT  CHEMICAL FACTORS: NUTRIENTS Nutrients.- Compounds from the environment used by microorganisms for the synthesis of new molecules to build new cells. INDISPENSABLE NUTRITIONAL FACTORS a) Carbon Souce b) Nitrogen source c) Mineral salts d) Oligoelementsand growth factors a) Carbon Source Monosaccharides Polysaccharides Carbon dioxide b) Nitrogen Source Peptones and/or organic nitrogen. Inorganic nitrogen (nitrates, N2…) c) Mineral salts: Ions and buffer solutions d) Oligoelements Phosphorus Sulphur Copper Iron e) Other: Growth factors (GF). Vitamins, amino acids, blood, etc. PHYSICAL FACTORS: Environmental Requirements Oxygen Temperature Psychrophiles - optimum less than 5°C Mesophiles- optimum 37°C Thermophiles- optimum more 80°C pH Low pH = Acid (fungi) High pH = Basic or Alkaline (bacteria) Osmotic Pressure – Halophiles- require high concentrations of of NaCl  Microbial growth It is the increase of number of cells of a population or the increase of the mass of cells. Bacteria.- Binary fission. Fungi - Yeast.- Mitosis - Filamentous fungi.- Mitosis and meiosis Virus.- Intracellular replication in the host  Bacterial Growth Curve 1.During lag phase, bacteria adapt themselves to growth conditions 2.The log phase (sometimes called the logarithmic phase or the exponential phase) is a period characterized by cell doubling. The number of new bacteria appearing per unit time is proportional to the present population 3.The stationary phase is often due to a growth-limiting factor such as the depletion of an essential nutrient, and/or the formation of an inhibitory product such as an organic acid. 4.At death phase (decline phase), bacteria die. This could be caused by lack of nutrients, environmental temperature above or below the tolerance band for the species, or other injurious conditions.