Microbiology ppt sonja ray


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Presentation for nursing students on basic principles of microbiology

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Microbiology ppt sonja ray

  1. 1. + Microbiology Sonja Ray, RN PHN
  2. 2. + Objectives 1.  Discuss basic characteristics of bacteria, including structures that lead to pathogenicity, drug susceptibility, and accurate identification 2.  Discuss basic characteristics of fungi, helminths, and viruses 3.  Describe three main modes of disease transmission 4.  Describe how bacteria penetrate host defenses and cause damage
  3. 3. + Objectives 6.  Describe how bacterial infections are diagnosed and treated 7.  Describe how viruses enter the host can cause illness, and how do we diagnose and treat viral infections 8.  Describe how fungi invade and damage host cells, and how fungal infections are diagnosed and treated 9.  Discuss methods of microbial control
  4. 4. + Overview of basic principles A quick reference
  5. 5. + The Basics:   Cell Theory: All living things are composed of cells (circa 1665)   Biogenesis: All living cells can arise only from preexisting cells   Formed basis of aseptic techniques: techniques that prevent contamination by microorganisms, because we know that microorganisms can only come from living microorganisms.   Heritable material (DNA) is passed from parent to offspring and dictates specific traits expressed in the offspring.   Germ Theory: Germs can cause disease
  6. 6. + Perspective
  7. 7. + Important Terms:   Normal microbiota – microorganisms present inside a healthy human body that do not cause harm and in some cases benefit the host.   Infection – the ability of an organism to invade and establish residency in a host   Note: Infection ≠ Disease!   Pathogen – organisms found in the environment that are capable of replication either independently or with the host AND are capable of provoking an adverse response in the host (aka disease)   Examples include bacteria, viruses, fungi, parasites, and prions   Range from 20 nm (polio virus) to 10 m (tapeworms)
  8. 8. + Koch’s Postulates   The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organism.   The microorganism must be isolated from a diseased organism and grown in pure culture.   The cultured microorganism should cause disease when introduced into a healthy organism   The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
  9. 9. + Koch’s Postulates
  10. 10. + Tools in Microbiology: Microscopy   Most initial observations of microorganisms are made with stained preparations under the microscope   Stains:   Stains are used to color the microorganisms in a way that emphasizes what you want to look at.   Microscopy can aid in classification of microorganism   Determine overall cell shape, size, and capsule   Using microscopy, you can tell if the microorganism is unicellular (like a bacteria) or multicellular (like a parasite)   Based on the organisms response to dyes, you can also note characteristics of the organisms cell wall (see gram stain and acid fast stain)
  11. 11. + Bacteria
  12. 12. + Anatomy of a Bacterial Cell   Bacteria are Prokaryotic, Unicellular Organisms   No nucleus – Their DNA is usually a singular circularly arranged chromosome   Their DNA is not associated with histones   They lack membrane-enclosed organelles (i.e. mitochondria)   Their cell walls almost always contain the complex polysaccharide peptidoglycan   They usually divide by binary fission. During this process, the DNA is copied and the cell splits into two cells.
  13. 13. + Shape: Cocci, Bacilli, Spiral
  14. 14. + Why shape matters: Classification!
  15. 15. + Structures External to the Cell Wall   Glycocalyx   A viscous, gelatinous polymer that is composed of polysaccharides, polypeptides, or both   If it is organized and firmly attached to the cell wall, it is called a capsule   If it is unorganized and loosely attached, it is described as a slime layer   Contributes to virulence:   Protects pathogenic bacteria from phagocytosis (i.e. Bacillus anthracis and Streptococcus pneumoniae)   Enables bacterium to survive by attaching to various surfaces (Streptococcus mutans)   Protects bacterium against dehydration and can inhibit movement of nutrients out of the cell
  16. 16. + Visualizing Bacteria: Capsule Stains   Showing that a microorganism has a capsule can help identify that microorganim and tell you something about its pathogenicity   Capsules to do not accept most biological dyes, so they appear as halos surrounding each stained cell
  17. 17. + Structures External to the Cell Wall   Flagella   Long filamentous appendages made of protein that propel bacteria   The flagellar protein called H antigen is useful for distinguishing among serovars (variations within a species)   Example: Serovars identified as E. coli O157:H7 are associated with foodborn epidemics
  18. 18. + Structures external to the cell wall   Axial Filaments   Found on spirochetes   Allow motility through corkscrew movement   Example: Treponema pallidum (Syphalis) and Borrelia burgdorferi (Lyme disease)
  19. 19. + Structures external to the cell wall   Fimbriae and Pili   Hairlike appendages, that are shorter, straighter, and thinner than flagella and used for attachment and transfer of DNA rather than motility   Fimbriae   Can enable a cell to adhere to surfaces (i.e. Neisseria gonorrhoeae)   Pili   Usually longer than fimbriae and only one or two pili per cell   Join bacterial cells in preparation for the transfer of DNA from one cell to another in a process called conjugation
  20. 20. + The Bacterial Cell Wall   Composed of a peptidoglycan network   Repeating disaccharide attached by polypeptides to form a lattice that surrounds and protects the cell   Disacharide portion is made up of monosaccharides called N- acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)   Alternating NAM and NAG molecules are linked in rows of 10-65 sugars to form a carbohydrate backbone   Adjacent rows are linked by polypeptides   The structure of the polypeptide link varies by species, but it always includes a tetrapeptide side chain attached to NAMs.   Many antibiotics work by targeting the cell wall (i.e. penicillin interferes with final linking of pepdidoglycan rows by peptide cross-bridges
  21. 21. + Bacterial Cell Wall: Images
  22. 22. + Gram Stain
  23. 23. + Gram Positive vs. Gram Negative
  24. 24. + Usefulness of Gram Stain
  25. 25. + Acid Fast Stain
  26. 26. + Bacterial Metabolism: Generating Energy Energy Growth End Product ATP molecules Process Conditions produced Aerobic Aerobic Water 38/glucose Respiration Anaerobic Anaerobic Us. an inorganic Between 2 and 38 Respiration substance (i.e. methane, hydrogen sulfide) Fermentation Aerobic or An organic molecule 2 anaerobic (i.e. lactic acid)
  27. 27. + Objective 1   Discuss basic characteristics of bacteria, including structures that lead to pathogenicity, drug susceptibility, and accurate identification   Glycocalyx - Protects pathogenic bacteria from phagocytosis, Enables bacterium to survive by attaching to various surfaces (Streptococcus mutans), Protects bacterium against dehydration and can inhibit movement of nutrients out of the cell   Flagella – H-antigen is useful for distinguishing among serovars   Axial filaments – allows motility so bacterium can travel to site of infection   Fimbriae – allows bacterium to adhere to surfaces   Components of the cell wall allow bacteria to be identified through the gram stain and acid fast stain
  28. 28. + Fungi
  29. 29. + Fungi: the basics  Easily visible by Light Microscopy (1-200 u)  Plant-like organisms which grow by continuous extension and branching (hyphae)  Growth   Some grow only as yeasts (ie. Candida Albicans, Cryptococcus )   Some grow only as molds (ie. Aspergillus)
  30. 30. + Growth of Fungi
  31. 31. + Fungi: The basics (continued)   All fungi require some organic compounds for energy (not phototrophs)   Most fungi are aerobic   Fungi can reproduce via a few routes:   Asexually by fragmentatino of their hyphae   Suxually or asexually by formation of spores   Fungi usually grow better in an environment with a pH of about 5   Fungi can also grow on substances with very low moisture content and are relatively resistant to osmotic pressure
  32. 32. + Helminths worms
  33. 33. + Helminths: the basics   Multicellular   Eukaryotic   Most possess digestive, circulatory, nervous, excretory, and reproductive systems   Most Helmonths that cause disease are parasitic, there are some distinguishing features of parasitic helminths:   They may lack a digestive system   Their nervous system is reduced   Their means of locomotion is occasionaly reduced or completely lacking   Their reproductive system is often complex. An individual produces a large number of eggs, by which a host is infected
  34. 34. + Life Cycle: Tapeworm
  35. 35. + Viruses
  36. 36. + Size of Viruses
  37. 37. + Viruses: The basics   Viruses are considered to be obligatory intracellular parasites   They require living host cells in order to multiply   They use host machinery to synthesize their own proteins and replicate their own DNA   Viruses have few or no enzymes of their own for metabolism   They lack enzymes for ATP generation and protein synthesis   This makes it difficult when designing antivirals, because most antimicrobial drug targets are enzymes unique the to pathogen, when an organism has no unique enzymes, you have no potential drug target
  38. 38. + Viral Anatomy   Nucleic Acid   DNA or RNA (But never both)   ssDNA   ds DNA   ss RNA   ds RNA   Capsid (Coat Protein)   protects viral genome from host endonucleases   capsomeres   Binding Sites   Envelope (not present on all viruses)   Derived from the host cell   Made up of lipids, proteins and carobhydrates   Binding Sites
  39. 39. + Shape of Viruses Helical Polyhedral
  40. 40. + Shape of Viruses Enveloped (can be Complex helical or polyhedral)
  41. 41. + Life Cycle of A virus: Papovavirus
  42. 42. + Differences in biosynthesis among viruses
  43. 43. + Objective 2   Discuss basic characteristics of fungi, helminths, and viruses   Fungi   multicellular or unicellular (yeasts)   Prefer acidic (pH ~5) environments   Can thrive in dry environments and are relatively resistant to osmotic pressure   Helminths   Multicellular   Most that cause disease are parasitic and have the following features:   They may lack a digestive system   Their nervous system is reduced   Their means of locomotion is occasionally reduces or completely lacking   Their reproductive system is often complex
  44. 44. + Objective 2 (cont)   Viruses   Require a host to multiply   Use hosts machinery to multiply   Made up to 2-3 main components:   Nucleic Acid (DNA or RNA)   Capsid   Envelope (mot present on all viruses)
  45. 45. + Disease transmission
  46. 46. + Stages of Infection
  47. 47. + Spread of infection throughout population
  48. 48. + Contact Transmission   Spread of agent of disease by direct contact, indirect contact, or droplet transmission   Direct contact (aka person to person) occurs when agent is transferred by physical contact between its source and a susceptible host, no intermediate object is involved   Indirect contact occurs when pathogen is transmitted from its reservoir to susceptible host by means of a nonliving object (fomite).   Droplet transmission occurs when microbes are spread in droplet nuclei that travel short distances
  49. 49. + Vehicle Transmission   Transmission of disease agents by a medium, such as water, food, or air   Note: The difference between airborne and droplet transmission   Airborne transmission refers to the spread of agents of infection by droplet nuclei in dust that travel more than 1 meter from the reservoir to the host (in droplet transmission the droplet travels less than 1 meter from the reservoir).   Example: Measles, Tuberculosis can also be spread by airborne transmission, even though it is also considered to be spread by droplet transmission
  50. 50. + Vector-based Transmission   Vectors – animals that carry pathogens from one host to another   Arthropods are an important group of vectors. They transmit disease by 2 general methods:   Mechanical transmission:   Passive transport of pathogens on the insect’s feet or other body parts   Example: houseflies can transfer pathogens of typhoid fever and bacillary dysentery   Biological transmission   Arthropod bites an infected person or animal and ingests some of the infected blood   Pathogen then reproduce in the vector   Pathogen either migrates to salivary gland of vector or gut   Vector spreads pathogen to susceptible host by defecating, vomiting, or biting the host   Example: malaria
  51. 51. + Objective 3   Describe three modes of disease transmission   Contact transmission: Spread of agent of disease by direct contact, indirect contact, or droplet transmission   Vehicle based transmission: Transmission of disease agents by a medium, such as water, food, or air   Vector based transmission: transmission of disease through an animal vector (i.e. arthropod)
  52. 52. + Nosocomial (hospital acquired) infections   In the US, the CDC estimates that 5 to 15% of all hospital patients acquire some type of nosocomial infection   The rate of nosocomial infections has increased 36% during the last 20 years.   2 million people per year contract nosocomial infections, and nearly 20,000 die as a result.   This means, nosocomial infections are the 8th leading cause of death in the US.
  53. 53. + Transmission based precautions
  54. 54. + Transmission based precautions
  55. 55. + Transmission based precautions
  56. 56. + How do pathogens cause injury? What do we do about it? (dx and tx)
  57. 57. + Progression of infection
  58. 58. + Step 1: Entry into human host A pathogen must overcome the host’s barriers to infection in order to cause disease
  59. 59. + Portal of Entry: Mucous Membranes   Lining of respiratory tract, GI tract, GU tract, and conjunctiva (lining of the eye)   Respiratory tract – easiest and most frequently traveled.   Examples: cold, flu, tuberculosis, pertussis, measles, strep throat, diptheria, pneumonia   GI – via contaminated food, water, and fingers   Examples: Hepatitis A, shigellosis, cholera   GU – some microbes can penetrate and unbroken mucous membrane, others require a cut or abrasion   Example: chlamydia, syphilis, herpes, gonorrhea
  60. 60. + Other portals of entry   Skin   Parenteral   Skin is the largest organ of   Microorganisms are the body. When unbroken is deposited into the tissues an effective barrier for most below the skin or mucus microorganisms. membranes   Some microbes can gain   Punctures, injections, bites, entrance thru openings in scratches, surgery, splitting the skin: hair follicles and of skin due to swelling or sweat glands dryness   Example: Nectoriasis   Caused by hookworm   Example: Athletes Foot   Caused by Fungi: Tinea pedis
  61. 61. + Step 2: Travel to site of infection   The blood stream, lymphatic system, and interstitial fluids provide mediums for pathogens to travel throughout the body, once inside
  62. 62. + Step 3: Cause damage   Pathogens can cause damage via three main pathways:   Direct damage   Release of Exotoxins, Endotoxins and/or irritant enzymes/ proteins   Induction of host immune response
  63. 63. + How Bacterial Pathogens Penetrate Host Defenses   Capsules   Capsule resists host’s defenses by impairing phagocytosis   Human response: produce antibodies against the capsule   Cell wall components   Enzymes (produced by some bacteria)   Coagulases: coagulates (clot) the fibrinogen in blood   Hyaluronidase: hydrolyzes hyaluronic acid, a type of polysaccharide that holds together certain cells of the body   Collagenase: breaks down the protein collagen, facilitating spread of infection through connective tissue   IgA proteases: destroys hosts IgA antibodies found on mucosal surfaces
  64. 64. + How Bacterial Pathogens Penetrate Host Defenses (cont)   Antigenic variation   Adaptive (acquired) immunity is a specific defensive response of the body to an infection that relies on remembering antigens associated with specific pathogens.   Some pathogens can alter their surface antigens, so by the time the body develops an immune response specific to those antigens, the pathogen has changed and is unaffected by the body’s immune response   Penetration into the host cytoskeleton   Adhesins: molecules on the surface of bacteria that are used to attach to host cells   Actin: the major component of the cytoskeleton of host cells. Used by some microbes to penetrate host and to move through the host cell
  65. 65. + How Bacterial Pathogens Cause Damage   Using host’s nutrients: Siderophores   Direct Damage   Production of Toxins   Exotoxins   Endotoxins   Inducing a hypersensitivity reaction
  66. 66. + Siderophores   Proteins secreted by some pathogens that allow the pathogen to obtain free iron from the host   Iron is required for the growth of most pathogenic bacteria, but the concentration of free iron is low because most iron is tightly bound to proteins   When iron is needed by a pathogen, siderophores are released into the medium where they take the iron away from iron transport proteins by binding the iron more tightly.   Once the iron-siderophore complex is formed, it binds to the bacterial surface and is used by the bacteria
  67. 67. + Direct damage   Bacteria can cause direct damage as they use the host cells for nutrients and produce waste products   As bacteria metabolize and multiply in cells, the cells usually rupture
  68. 68. + Toxins   Exotoxins:   produced inside some bacteria as a part of their growth and metabolism and secreted by the bacterium into the surrounding medium or released following lysis   Many exotoxins are encoded by genes on the bacterial plasmid   They destroy particular parts of the host cell or inhibit certain metabolic functions   The body produces antitoxins, which are antibodies that provide immunity to exotoxins
  69. 69. + Toxins (Cont)   Endotoxins   Are part of the outer portion of the cell wall of gram-negative bacteria   Are lipopolysaccharides   Are released when gram negative bacteria die and their cell walls undergo lysis   Antibiotics used to treat diseases caused by gram-negative bacteria can lead to release of endotoxin and thus may lead to immediate worsening of the symptoms, but the condition usually improves as the endotoxin breaks down   Stimulates macrophages to release cytokines in very high (toxic) concentrations. Symptoms include: chills, fever, weakness, generalized aches. Can lead to miscarriage, shock, and death
  70. 70. + Objective 4   Describe how bacteria penetrate host defenses and cause damage   Penetrate host defenses:   Capsules   Cell wall components   Enzymes   Antigenic variation   Penetration into cytoskelton   Cause damage   Using host’s nutrients   Direct damage   Toxins   Hypersensitivity reaction
  71. 71. + Diagnosing and treating a bacterial infection   Culture   Gram stain   Set up culture with best specimen for symptoms   Identification based on biochemical reactions   Sensitivities to determine best antibiotic therapy   All usually completed in 24-72 hours   Special consideration for Mycobacteria   distinctive waxy cell coat requiring Acid Fast Stains   virulence is related to cell wall “cord factor” which inhibits phagosome-lysosome fusion   Special culture methods used; may take up to 6 weeks   TX: antibiotics
  72. 72. + Objective 5   Describe how bacterial infections are diagnosed and treated   Diagnosis   Culture   Drug sensitivity tests  Gram stain/ acid fast stain   Treatment   antibiotics
  73. 73. + Example of Bacterial Infection: C. diff   Clostridium difficile is a bacteria that can cause symptoms ranging from acute diarrhea to life-threatening inflammation of the colon   Gram-positive, spore-forming bacillus   Part of normal flora in 1 to 3% of humans   Tx. with broad-spectrum antibiotics predisposes person to colonization by C. diff
  74. 74. + C. diff infection (cont)   C. diff releases toxins that cause mucosal damage and inflammation   Pseudomembranous colitis occurs when an adherent inflammatory membrane covers areas of mucosal injury   Life threatening   Prompt therapy is needed to prevent perforation of bowel   C. diff is transmitted via fecal- oral route
  75. 75. +
  76. 76. + C. diff infection (cont)   Symptoms:   Diarrhea (mild to moderate)   Lower abdominal cramping   If due to antibiotics, they typically begin within 1 to 2 weeks after antibiotic tx started, but this varies from 1 day to 6 weeks   Symptoms tend to subsitde after antibiotic has been d/c’d   Diagnosis:   History (look for antibiotic use)   Lab tests to confirm C. diff in stool by culture and measuring presence of C. diff toxin   Rapid dx can be done with flexible sigmoidoscopy or abdominal CT
  77. 77. + C. Diff (cont)   Treatment   Immediate d/c of antibiotics   Specific tx aimed at eradicate C. diff if symptoms are severe or persistent   Metronidazole (PO) is first choice, but vancomycin (PO) is used in people who can’t tolerate metronidazole or don’t respond   Nursing concerns   Maintaining and monitoring hydration   Maintaining and monitoring skin integrity   Monitoring stool output and response to tx   Contact precautions to prevent spread
  78. 78. + Viral Mechanisms for Invading Host   Viruses need a host for replication   Viruses gain access to cells because they have attachment sites for receptors on their target cells.   When an attachment site is brought together with an appropriate receptor, the virus can bind to and penetrate those cells
  79. 79. + Common terms in viral infection   Active Infection: After recent entry, the virus replicates with the production of antigens. Antibodies and/or a cell mediated response is usually absent in early acute infection.   Past Infection: The virus entered long ago, an immune response occurred and the virus has been cleared. This is characterized by the absence of antigen and the presence of antibodies and/or a cell-mediated response.   Latent Infection: The virus entered in the past and remains there, BUT is inactive. Antigens are absent, but antibodies and/or a cell mediated response is present. The virus can reactivate.   Recurrent Infection: The latent virus has become active. Antigen and antibodies are present.
  80. 80. + Viral induced injury   Infection of a host cell by a virus usually leads to the death of the host cell. This can occur one of a few ways:   Accumulation of large numbers of multiplying viruses   Effects of viral proteins on the permeability of the host cell’s plasma membrane   Inhibition of host DNA, RNA, or protein synthesis   Some viruses cause lysosomes to release their enzymes   Some viruses cause adjacent infected cells to fuse to form a vary large multinucleate call called a syncytium   Some viruses cause antigenic changes on the surfface of infected cells. This elicits a host antibody response against the infected cell, and thus targets the cell for destruction by the host’s immune system   Some viruses cause chromosomal damage to the host cell
  81. 81. + Diagnosis: methods of identifying a virus   Detection of virus by Culture   Detection of Antigens-- ELISA   Detection of specific Antibodies
  82. 82. + Prevention and treatment of viral diseases   Let them run their course and treat symptoms   Antivirals (there are not as many antiviral medications available)   Vaccines
  83. 83. + Objective 6   How do viruses enter the host can cause illness, and how do we diagnose and treat viral infections?   Viruses gain access to cells because they have attachment sites for receptors on their target cells.   Viruses can cause damage in the following ways:   Accumulation of large numbers of multiplying viruses   Viral proteins effect the permeability of the host cell’s plasma membrane   Inhibition of host DNA, RNA, or protein synthesis   Cause lysosomes to release their enzymes   Cause adjacent infected cells to fuse to form a vary large multinucleate call   Cause antigenic changes on the surface of infected cells, targeting them for destruction by the host’s immune system   Cause chromosomal damage to the host cell   Diagnosis through culture and nucleic acid matching, ELISA, Western Blot   Treatment: treat symptoms, give antivirals (rare), prevent spread with vaccines
  84. 84. + Example of a viral infection: Influenza (flu)   Influenza is caused by RNA viruses in the family Orthomyxoviridae   Can affect birds and mammals (which can serve as reservoirs)   There are 3 types that cause epidemics in humans: A, B, and C   Airborne transmission and direct contact transmission   Coughs and sneezes (air)   Contact with bird droppings or nasal secretions (direct-contact)   A person is contagious beginning about the day before symptoms appear to 5 to 7 days later
  85. 85. + Influenza (Cont)   Influenza binds to epithelial cells in nose, throat and lungs (See diagram)   Viral proteins can degrade host cell mRNA, inhibit translation of host cell mRNA   New viruses buds off from the host cell to spread infection and the host cell dies   Influenza evades immune response through antigenic variation
  86. 86. + Influenza   Most Common Symptoms:   Chills   Fever   Sore throat   Muscle pains   Severe headache   Coughing   Weakness/fatigue   General discomfort   Nausea and vomiting (esp children)
  87. 87. + Influenza diagnosis   Symptom assessment   Tests (rare)   Rapid flu test   Done in a doctor’s office   Direct fluorescent antibody stain (DFA)   Done in a lab   Viral culture   Done in a lab Takes 3-10 days     Nucleic acid amplification   Influenza A or B antibody tests
  88. 88. + Influenza treatment   Treatment:   Fluids, rest   Treat symptoms (acetaminophen for fever, etc)   Neuraminidase inhibitors (antiviral)   Prevent the release of new infectious viruses and halt viral replication   M2 inhibitors (antiviral)   Prevent uncoating of virus once in cell, thus preventing replication   Preventing spread:   Handwashing   Seasonal Vaccines (esp. health care workers, over 50, etc)
  89. 89. + Influenza: Nursing concerns   Encourage rest   Encourage fluids   Monitor lung sounds   Provide supportive therapy as indicated (antipyretics, or antitussives)
  90. 90. + Fungal Infection   Infection is called mycoses or mycotic infection.   Fungal infections tent to be chronic because fungi grow slowly   Do not have well defined set of virulence factors   Classified into one of five groups according to extent of tissue involvement and mode of entry into the host   Systemic   Subcutaneous   Cutaneous   Superficial   Opportunistic
  91. 91. + Systemic Mycoses   Fungal infections deep within the body   Not restricted to any particular region of the body, but can affect a number of tissues and organs   Usually caused by fungi that live in the soil   Inhalation of spores is the route of transmission; infection typically begins in the lungs and then spreads to other tissues.   Do not tend to be contagious from animal to human or from human to human   Example: Histoplasmosis and coccidioidomycosis
  92. 92. + Subcutaneous mycoses   Fungal infections beneath the skin   Caused by fungi that live in soil and on vegetation   Infection often begins by direct implantation of spores or mycelial fragments into a puncture wound on the skin   Example: Sporotrichosis (acquired by gardeners and farmers)
  93. 93. + Cutaneous mycoses   Dermatophytes: fungi that infect only the epidermis, hair, and nails   Cutaneous mycoses (aka dermatomycoses) are infections caused by dermatophytes.   Dermatophytes secrete karatinase, an enzyme that degrades karatin, a protein in hair, skin, and nails   Infection is transmitted from human to human or animal to human by direct contact or by contact with infected hairs and epidermal cells   Example: Epidermophyton floccosum
  94. 94. + Superficial Mycoses   Caused by fugni localized along hair shafts and in superficial (surface) epidermal cells   Prevalent in tropical climates   Example: Pitvriases versicolor (shown on the right, above), Tinea Capitus (shown on right, below)
  95. 95. + Opportunistic Mycoses   Opportunistic pathogen:   Example: Pneumocystis and generally harmless in normal Candidiasis (shown below) habitat, but can become pathogenic in a host who is:   seriously debilitated or traumatized   under treatment with broad- spectrum antibiotics   Immunocompromised due to drugs or an immune disorder   diagnosed with a lung disease
  96. 96. + How do fungi invade host cells?   Candida albicans and Trichophyton secrete proteases that modify host cell membranes to allow attachment of the fungi   Cryptococcus neoformans produces a capsule that helps it resist phagocytosis
  97. 97. + How do Fungi cause damage?   Some produce metabolic products that are toxic to humans   i.e. Trichothecenes: fungal toxins that inhibit protein synthesis in host cells   i.e. Alfatoxin is produced by a mold that can be found in peanut butter. Excessive amounts of this toxin is known to have carcinogenic properties.   Some provoke allergic reactions
  98. 98. + Diagnosis and Treatment of Fungal Infection   Cultures may be done.   Many fungi can be identified by light microscopy.   Specimens and biopsies: Special stains   Medications are available for treatment.   Topicals: end in –azole   Systemic: ketoconazole, amphotericin B, Nystatin   Note: Some fungi have developed resistance to antifungals
  99. 99. + Objective 7   Describe how fungi invade and damage host cells, and how fungal infections are diagnosed and treated   Invade host:   Secrete proteases that allow attachment   Produce a capsule that resists phagocytosis   Cause damage:   Producing toxins   Elicit allergic response   Diagnosis: culture and light microscopy, gross assessment   Treatment: antifungals
  100. 100. + Helminth induced injury   Use host tissues for their own growth or produce large parasitic masses; the resulting cellular damage evokes symptoms   Waste products of these parasites can also contribute to disease
  101. 101. + Protozoa induced injury   Reproduce within host cell, causing it to rupture   Example: Plasmodium   Prevent normal cell function   Example: Toxoplasma   Digest cells and tissue fluids   Example: Giardia lamblia   Note: some protozoa can avoid host defenses by varying their antigens like viruses. For example Trypanosoma (causes sleeping sickness) can produce up to 1000 different antigens
  102. 102. + Control of Microbial Growth
  103. 103. + Requirements for Growth Temperature   Every bacterium has an ideal temperature range and temperatures outside that range prohibit growth and life   Psychrophiles (cold-loving)   Mesophiles (moderate temp- loving)   Thermophiles (heat loving)
  104. 104. + Requirements for Growth   pH   Trace Elements (i.e. zinc, iron,   Most bacteria prefer a pH copper, molybdenum) between 6.5 and 7.5   Oxygen (in some bacteria)   Human immune response often uses pH to destroy   Organic Growth Factors bacteria   Organic compounds that an   Osmotic Pressure organism is unable to synthesize and must be   Carbon directly obtained from the environment (i.e. vitamins,   Nitrogen, Sulfur and amino acids, purines, Phosphorus pyrimidines)
  105. 105. + Terms used in microbial control   Sterilization: destroying all forms of life   Disinfection: destroying pathogens or unwanted organisms   Disinfectant: antimicrobial agent used on inanimate objects   Antiseptic: antimicrobial agent used on living tissue   -cidal: kills (i.e. bactericidal = kills bacteria)   Static: inhibits growth (i.e. bacteristatic = inhibits growth of bacteria)
  106. 106. + Actions of microbial control agents   Alteration of membrane   Damage to proteins and permeability nucleic acids   Plasma membrane is located   Many bacterial proteins are just inside the cell wall enzymes that are vital to all cellular activities   Membrane actively   Destroying the shape of regulates passage of proteins destroys the nutrients into the cell and function of proteins the elimination of wastes   H-bonds and disulfide from the cell bridges are critical to   Damage to the membrane protein structure but can causes cellular contents to be broken by heat and leak into the surrounding chemicals medium and interferes with   Heat, radiation, or chemicals growth can destroy bacterial DNA and RNA
  107. 107. + Microbial Control Physical Methods Chemical Agents   Heat   Phenols   Moist heat   Phenolics   Dry heat   Bisphenols   Filtration   Biguanides   Cold   Halogens   High Pressure   Alcohols   Dessication   Heavy metals   Osmotic Pressure   Surface-Active Agents   Radiation   Chemical Food preservatives   Aldehydes   Gaseous Chemosterilizers   Peroxygens
  108. 108. + Objective 9   Discuss methods of microbial control   Physical: Heat, Filtration, Cold, High Pressure, Dessication, Osmotic Pressure, Radiation   Chemical: Phenols, Phenolics, Bisphenols, Biguanides, Halogens, Alcohols, Heavy metals, Surface-Active Agents, Chemical Food preservatives, Aldehydes, Gaseous Chemosterilizers, Peroxygens   The above act either by altering the membrane permeability of the microorganism or damaging proteins and nucleic acids of the microorganism