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3 Microbilogylecturelab

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