Staphylococcus lecture bls 209

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Staphylococcus lecture bls 209

  1. 1. <ul><li>Pathogenic Gram-Positive Cocci (Staphylococci) </li></ul><ul><li>VMP 231 </li></ul><ul><li>Hoza, A.S </li></ul>
  2. 2. <ul><li>Stain purple when gram-stained </li></ul><ul><li>Can be categorized into 2 major groups </li></ul><ul><ul><li>Genera of cocci-shaped organisms- Staphylococcus , Streptococcus , and Enterococcus </li></ul></ul><ul><ul><li>Genera of bacilli-shaped organisms- Bacillus , Clostridium , Listeria, Corynebacterium , Mycobacterium , Nocardia , and Actinomyces </li></ul></ul>Gram-Positive Pathogens
  3. 4. <ul><li>Normal members of every human’s and animal microbiota </li></ul><ul><li>Can be opportunistic pathogens </li></ul>Staphylococcus
  4. 5. <ul><li>Gram-positive cocci, nonmotile, facultative anaerobes </li></ul><ul><li>Cells occur in grapelike clusters because cells division occurs along different planes and the daughter cells remain attached to one another </li></ul><ul><li>Salt-tolerant: allows them to tolerate the salt present on human skin </li></ul><ul><li>Tolerant of desiccation: allows survival on environmental surfaces (fomites) </li></ul>Structure and Physiology
  5. 8. <ul><li>Two species are commonly associated with staphylococcal diseases in humans/ANIMALS </li></ul><ul><ul><li>Staphylococcus aureus -The more virulent strain that can produce a variety of conditions depending on the site of infection </li></ul></ul><ul><ul><li>Staphylococcus epidermidis -Normal microbiota of human skin that can cause opportunistic infections in immunocompromised patients or when introduced into the body </li></ul></ul>Structure and Physiology
  6. 9. <ul><li>“ Staph’ infections result when staphylococci breach the body’s physical barriers </li></ul><ul><li>Entry of only a few hundred bacteria can result in disease </li></ul><ul><li>Pathogenicity results from 3 features </li></ul><ul><ul><li>Structures that enable it to evade phagocytosis </li></ul></ul><ul><ul><li>Production of enzymes </li></ul></ul><ul><ul><li>Production of toxins </li></ul></ul>Pathogenicity
  7. 10. <ul><li>Protein A coats the cell surface </li></ul><ul><ul><li>Interferes with humoral immune responses by binding to class G antibodies </li></ul></ul><ul><ul><li>Inhibits the complement cascade </li></ul></ul><ul><li>Clumping Factor (Bound coagulase) </li></ul><ul><ul><li>Converts the soluble blood protein fibrinogen in insoluble fibrin molecules that form blood clots </li></ul></ul><ul><ul><li>Fibrin clots hide the bacteria from phagocytic cells </li></ul></ul>Structural Defenses Against Phagocytosis
  8. 11. <ul><li>3 . Synthesize loosely organized polysaccharide slime layers (often called capsules) </li></ul><ul><ul><li>Inhibit chemotaxis of and phagocytosis by leukocytes </li></ul></ul><ul><ul><li>Facilitates attachment of Staphylococcus to artificial surfaces </li></ul></ul>Structural Defenses Against Phagocytosis
  9. 12. <ul><li>Coagulase </li></ul><ul><ul><li>Triggers blood clotting </li></ul></ul><ul><li>Hyaluronidase </li></ul><ul><ul><li>Breaks down hyaluronic acid, enabling the bacteria to spread between cells </li></ul></ul><ul><li>Staphylokinase </li></ul><ul><ul><li>Dissolves fibrin threads in blood clots, allowing Staphylococcus aureus to free itself from clots </li></ul></ul>Enzymes
  10. 13. <ul><li>4. Lipases </li></ul><ul><ul><li>Digest lipids, allowing staphylococcus to grow on the skin’s surface and in cutaneous oil glands </li></ul></ul><ul><li>5.  -lactamase </li></ul><ul><ul><li>Breaks down penicillin </li></ul></ul><ul><ul><li>Allows the bacteria to survive treatment with  -lactam antimicrobial drugs </li></ul></ul>Enzymes (cont.)
  11. 14. <ul><li>Staphylococcus aureus produces toxins more frequently than S.epidermidis </li></ul><ul><li>1. Cytolytic toxins </li></ul><ul><ul><li>Disrupts the cytoplasmic membrane of a variety of cells </li></ul></ul><ul><ul><li>Leukocidin can lyse leukocytes specifically </li></ul></ul><ul><li>2. Exfoliative toxins </li></ul><ul><ul><ul><li>Causes the patient’s skin cells to separate from each other and slough off the body </li></ul></ul></ul>Toxins
  12. 15. <ul><li>3. Toxic-shock-syndrome toxin </li></ul><ul><ul><li>Causes toxic shock syndrome </li></ul></ul><ul><li>4. Enterotoxins </li></ul><ul><ul><li>Stimulate the intestinal muscle contractions, nausea, and intense vomiting associated with staphylococcal food poisoning </li></ul></ul>Toxins (cont.)
  13. 16.                                                                                                                 III.    Virulence factors of Staphylococcus aureus
  14. 17. <ul><li>3 categories </li></ul><ul><ul><li>Noninvasive Disease </li></ul></ul><ul><ul><ul><li>Food poisoning from the ingestion of enterotoxin-contaminated food </li></ul></ul></ul><ul><ul><li>Cutaneous Disease </li></ul></ul><ul><ul><ul><li>Various skin conditions including scalded skin syndrome, impetigo, folliculitis, and furuncles </li></ul></ul></ul>Staphylococcal Diseases
  15. 18. <ul><ul><li>Systemic Disease </li></ul></ul><ul><ul><ul><li>Toxic shock syndrome-TSS toxin is absorbed into the blood and causes shock </li></ul></ul></ul><ul><ul><ul><li>Bacteremia-presence of bacteria in the blood </li></ul></ul></ul><ul><ul><ul><li>Endocarditis-occurs when bacteria attack the lining of the heart </li></ul></ul></ul><ul><ul><ul><li>Pneumonia-inflammation of the lungs in which the alveoli and bronchioles become filled with fluid </li></ul></ul></ul><ul><ul><ul><li>Osteomyelitis-inflammation of the bone marrow and the surrounding bone </li></ul></ul></ul>Staphylococcal Diseases
  16. 19. <ul><li>Diagnosis </li></ul><ul><ul><li>Detection of Gram-positive bacteria in grapelike arrangements isolated from pus, blood, or other fluids </li></ul></ul><ul><li>Treatment </li></ul><ul><ul><li>Methicillin is the drug of choice to treat staphylococcal infections </li></ul></ul><ul><ul><ul><li>Is a semisynthetic form of penicillin and is not inactivated by  -lactamase </li></ul></ul></ul>Diagnosis, Treatment, and Prevention
  17. 20. Diagnosis <ul><li>Specimen </li></ul><ul><li>Smear </li></ul><ul><li>Culture </li></ul><ul><li>Film </li></ul><ul><li>Biochemical Reactions </li></ul><ul><li>Antibiogram </li></ul><ul><li>Typing </li></ul>
  18. 21. <ul><li>Prevention </li></ul><ul><ul><li>Hand antisepsis is the most important measure in preventing nosocomial infections </li></ul></ul><ul><ul><li>Also important is the proper cleansing of wounds and surgical openings, aseptic use of catheters or indwelling needles, an appropriate use of antiseptics </li></ul></ul>Diagnosis, Treatment, and Prevention (cont.)
  19. 22. Antibiotic sensitivity pattern <ul><li>Very variable and not predictable </li></ul><ul><li>Very imp. In Pt. Management </li></ul><ul><li>Mechanisms </li></ul><ul><ul><li>1.B lactamase production - plasmid mediated </li></ul></ul><ul><ul><ul><li>Has made S. aureus resistant to penicillin group of antibiotics - 90% of S. aureus (Gp A) </li></ul></ul></ul><ul><ul><ul><li>β lactamase stable penicillins (cloxacillin, oxacillin, methicillin) used </li></ul></ul></ul>
  20. 23. <ul><ul><li>2. Alteration of penicillin binding proteins </li></ul></ul><ul><ul><ul><li>(Chromosomal mediated) </li></ul></ul></ul><ul><ul><ul><li>Has made S. aureus resistant to β lactamase stable penicillins </li></ul></ul></ul><ul><ul><ul><li>10-20% S. aureus Gp (B ) GH Colombo/THP resistant to all Penicillins and Cephalasporins) </li></ul></ul></ul><ul><ul><ul><li>Vancomycin is the drug of choice </li></ul></ul></ul>Antibiotic sensitivity pattern
  21. 24. <ul><li>Tested in lab using methicillin </li></ul><ul><li>Referred to as methicillin resistant S. aureus (MRSA) </li></ul><ul><li>Emerging problem in the world </li></ul><ul><li>Drug of choice - vancomycin </li></ul><ul><li>No effective antibiotics discovered -We might have to discover </li></ul>Antibiotic sensitivity pattern

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