3 Microbilogylecturelab


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3 Microbilogylecturelab

  1. 1. Microbiology Antonio Rivas PA-C Feb 2008
  2. 2. Microbiology <ul><li>Clinical microbiology encompasses </li></ul><ul><ul><li>Bacteriology </li></ul></ul><ul><ul><li>Parasitology </li></ul></ul><ul><ul><li>Virology </li></ul></ul><ul><ul><li>Mycology </li></ul></ul>
  3. 3. Bacteriology <ul><li>Characteristics of bacteria </li></ul><ul><ul><li>Multiply by fission </li></ul></ul><ul><ul><li>Grow in colonies </li></ul></ul><ul><li>Morphology </li></ul><ul><ul><li>Coccus </li></ul></ul><ul><ul><li>Bacillus </li></ul></ul><ul><ul><li>Spiral </li></ul></ul><ul><ul><li>Growth patterns </li></ul></ul>
  4. 4. Specimen collection <ul><li>Collect before antimicrobials are given </li></ul><ul><li>Specimen collected where the organism is most likely to be found w/o external contamination </li></ul><ul><li>Stage of the disease </li></ul><ul><ul><li>Enteric pathogens are present in higher numbers during the acute or diarrheal phase of the infection </li></ul></ul><ul><li>Sufficient quantity of specimen </li></ul><ul><li>Prompt delivery to the lab </li></ul>
  5. 5. Aseptic Technique
  6. 6. Techniques Culture
  7. 7. Culture Techniques
  8. 8. Bacteriological Growth Media <ul><li>Agar plates contain different components that enhance or inhibit the growth of certain microorganisms </li></ul><ul><li>Examples: </li></ul><ul><ul><li>MAC-selective media - inhibits Gram Positive organism </li></ul></ul><ul><ul><li>HE- selective media- inhibits Gram negative organism </li></ul></ul>
  9. 9. Bacteriological Growth Media
  10. 10. Incubation - Plates are incubated for : 24-48 hrs at different temperature and O2 concentration- - Most human pathogens grow best at 35-37 degree C
  11. 11. Culture Techniques <ul><li>Observing culture after 24 hours </li></ul><ul><ul><li>Colony characteristics </li></ul></ul><ul><ul><li>Presence (or absence) of hemolysis </li></ul></ul>Staphylococcus aureus Beta hemolyticus strept.
  12. 12. Colony Characteristics <ul><li>Colony size, shape, moist or dry, color, smell </li></ul><ul><ul><ul><li>Pseudomonas sp. Smells like grapes </li></ul></ul></ul><ul><ul><ul><li>Neisseria gonorrhea smells like sweaty tennis shoe </li></ul></ul></ul><ul><ul><ul><li>Shigella is mucoid and purple </li></ul></ul></ul><ul><ul><li>Presence of hemolysis in blood agar plate (Strep.pyogenes-throat inf.-beta hemolysis) </li></ul></ul><ul><ul><ul><li>Beta-hemolysis: </li></ul></ul></ul><ul><ul><ul><li>Lysis of the red cell present in the media showing clear area around the bacterial growth </li></ul></ul></ul>
  13. 13. Automated ID
  14. 14. Gram Stain <ul><li>Bacterial species divided into two groups according to how they take Gram Stain </li></ul><ul><ul><li>Gram positive : take up the crystal violet basic stain (stain purple) </li></ul></ul><ul><ul><li>Gram negative : allow the crystal violet to easily washout with acetone and take up the Safranin dye (stain pink) </li></ul></ul><ul><ul><li>Related to the cell membrane composition </li></ul></ul>
  15. 15. Gram Stain <ul><li>Important for </li></ul><ul><ul><li>Bacterial identification </li></ul></ul><ul><ul><li>Antibiotic susceptibility testing </li></ul></ul><ul><ul><li>Preparing a smear </li></ul></ul><ul><ul><ul><li>From a swab </li></ul></ul></ul><ul><ul><ul><li>From a culture </li></ul></ul></ul>
  16. 16. Preparing the Bacterial Smear <ul><li>Heat-fixing the smear </li></ul><ul><ul><li>Smear must be dry </li></ul></ul><ul><ul><li>Affixes bacteria to slide </li></ul></ul><ul><ul><li>Do not use excessive heat </li></ul></ul>
  17. 17. Gram Stain <ul><li>Primary stain </li></ul><ul><li>Gram’s iodine </li></ul><ul><ul><li>Mordant </li></ul></ul><ul><li>Decolorizer </li></ul><ul><li>Counterstain </li></ul>
  18. 18. Observe the Stained Smear <ul><li>Oil immersion </li></ul><ul><li>Gram reactions </li></ul><ul><ul><li>Gram (+) -> purple </li></ul></ul><ul><ul><li>Gram (-) -> pink </li></ul></ul>
  19. 19. Microbiology <ul><li>Bacteremia : transient release of bacteria to the blood stream, indicates the presence of a focus of disease </li></ul><ul><li>Septicemia or Sepsis : a situation in which bacteria and their products are causing harm to the host </li></ul><ul><li>Terms are used interchangeable </li></ul>
  20. 20. <ul><li>Portals of entry for septicemia: </li></ul><ul><ul><li>GU </li></ul></ul><ul><ul><li>Respiratory </li></ul></ul><ul><ul><li>Abscesses </li></ul></ul><ul><ul><li>Surgical wound infections </li></ul></ul><ul><ul><li>Biliary tract </li></ul></ul><ul><ul><li>Other sites </li></ul></ul><ul><li>Organisms most commonly isolated from blood are: </li></ul><ul><ul><li>Gram positive cocci </li></ul></ul><ul><ul><li>Coagulase neg staphylococci </li></ul></ul><ul><ul><li>Staphylococcus aureus </li></ul></ul><ul><ul><li>Enterococcus sp. </li></ul></ul>
  21. 21. <ul><li>Meningitis: infection in the subarachnoid space, between the Pia-mater and the Arachnoid </li></ul><ul><li>Dx by PE, CSF analyisis, and cultures </li></ul><ul><li>Hematogenous spread </li></ul><ul><li>Children <5 years </li></ul><ul><ul><li>Haemophilus influenza </li></ul></ul><ul><li>Neonates </li></ul><ul><ul><li>Group B streptococci </li></ul></ul><ul><ul><li>E.coli </li></ul></ul><ul><ul><li>Listeria sp. </li></ul></ul><ul><li>Most common bacteria causing meningitis in children age 6 years and up </li></ul><ul><ul><li>Haemophilus influenza </li></ul></ul><ul><ul><li>Neisseria meningitidis </li></ul></ul><ul><ul><li>Streptococcus pneumoniae </li></ul></ul>
  22. 22. <ul><li>Meningitis in adults </li></ul><ul><ul><li>Neisseria meningitidis(young adults crowded conditions) </li></ul></ul><ul><ul><li>Pneumococci </li></ul></ul><ul><ul><li>Listeria monocytogenes </li></ul></ul><ul><ul><li>Staphylococcus aureus </li></ul></ul>
  23. 23. Staphylococcus saprophyticus <ul><li>Gram positive cocci </li></ul><ul><li>Second cause of UTI in young females after E.coli </li></ul><ul><li>Symptoms : </li></ul><ul><li>Burning when urinating </li></ul><ul><li>Increased urge to urinate </li></ul><ul><li>Dripping effect </li></ul><ul><li>Razor like pain in the lower abdomen and during intercourse </li></ul><ul><li>Treated with Quinolones in the US </li></ul>
  24. 24. Enterococcus faecalis <ul><li>Gram positive bacilli </li></ul><ul><li>Inhabitant in GI tract humans and animals </li></ul><ul><li>Life threatening nosocomial infections </li></ul><ul><li>High level antibiotic resistance </li></ul><ul><li>Can cause endocarditis, bladder, prostate and epididymal infections </li></ul>
  25. 25. Streptococcus pyogenes <ul><li>Gram positive cocci in chains </li></ul><ul><li>Group A, beta hemolytic </li></ul><ul><li>Strept throat-pharyngitis </li></ul><ul><li>Impetigo </li></ul><ul><li>Cellulitis </li></ul><ul><li>Necrotizing fasciitis </li></ul><ul><li>Toxic shock </li></ul><ul><li>Rheumatic fever </li></ul><ul><li>Glomerulonephritis </li></ul><ul><li>Sensitive to penicillin </li></ul>
  26. 26. Candida albicans <ul><li>Yeast, fungi </li></ul><ul><li>Opportunistic oral and genital infection in immunocompromised patients </li></ul><ul><li>Live in human mouth and GI </li></ul><ul><li>May occur in blood </li></ul><ul><li>Thrush – immunocompromised </li></ul>
  27. 27. Cryptococcus neoformans <ul><li>Encapsulated yeast-like fungus </li></ul><ul><li>Cryptococcal meningitis in immunocompromissed patients </li></ul><ul><li>India ink stain used for Dx in CSF </li></ul>
  28. 28. E.coli <ul><li>Gram negative rod </li></ul><ul><li>Virulent strains can cause gastroenteritis, UTI, neonatal meningitis </li></ul><ul><li>Ascending UTI with fecal contamination </li></ul>