Bacte Lab Mid

• Streptococcus classification


  Based on the antigen that can be found in the cell wall
• S. pyogenes


  • Can cause Rheumatic Heart Disease
  • M protein is the same antigen that can be found in the cardiac muscle; antiphagocytic
  • Self antigen has the same characteristics with the M protein
  • Antibodies will attack the self antigen thinking it is a M protein
• Infections


  • Neisseria meningitidis
  • S. agalactiae (found in the birth canal, can be passed on to the baby)
  • S. pneumoniae (causes Pneumonia, lobar pneumonia has rust red sputum)
  • Staphylococcus (causes Urinary Tract Infection)
• Staphylococcus


  • Most virulent species of staphylococci encountered
  • Virulence - degree of pathogenicity
  • Proteins and Enzymes that protect the bacteria: Coagulase, Catalase, Staphylokinase
• Staphylococcus Infections


  • Toxic shock syndrome
  • Food poisoning
  • Blood Brain Barrier - CNS/Central Nervous System
• Tests used in the Identification of Clinically Significant Gram Positive Cocci

  1. Catalase Test

  2. Coagulase Test

  3. Novobiocin Test

  4. Optochin Test

  5. Bile Salts

  6. Bacitracin Test

  7. Salt Tolerance Test

  8. Bile Esculin Hydrolysis Test

  9. Camp Test
• Catalase Test


  Distinguish the Staphylococci to Streptococci<|>Presence of bubbles (effervescence) indicates Staphylococcus<|>RBC contains catalase (to avoid false positive do not pick up BLOOD AGAR)<|>Platinum loop do not yield false-positive results<|>Older cultures may result to false-negative
• Coagulase Test


  Staphylokinase - dissolves the clot<|>Incubation - 1-4 hrs, if no clot incubate again for 20 hours<|>Positive control - clot formation; Staphylococcus aureus<|>Negative control - liquid; Staphylococcus epidermidis<|>0.1% EDTA Rabbit Plasma instead of citrated plasma<|>S. aureus produces 2 forms of coagulase: SLIDE TEST and TUBE TEST
• Novobiocin Test


  Antibiotic, cell wall inhibitors, protein inhibitors<|>S. aureus - obligate aerobe/facultative aerobes<|>Clearing on zone of inhibition - sensitive, Negative - equal or less than 16mm, Positive - greater than 16mm
• Optochin Test


  Performed in Blood Agar Plate<|>Zone of inhibition: Positive/Sensitive - greater than or equal to 14mm, Negative/Resistant - no zone diameter around the disk
• Bacitracin Test - Taxo A

  Differentiates GAS from GBS<|>Inhibits the synthesis of bacterial cell walls<|>Zone of inhibition: Positive/Susceptible - any zone diameter of >10mm, Negative/Resistant - no zone of inhibition
• Salt Tolerance Test


  Examine the turbidity/growth in 6.5% NaCl<|>Sugar fermented - acid produced, Bromocresol purple to change from purple to yellow<|>Enterococcus > there is growth, S. bovis > no growth at all
• Bile Esculin Hydrolysis Test

  Bacteria able to grow in bile salts (inhibit other bacteria to grow)<|>Esculin hydrolysis results in esculetin and glucose, forming a black color<|>Positive - E. faecalis, Negative - S. pyogenes
• Camp Test


  Diffusible protein, heat stable hemolytic protein produced by S. agalactiae<|>Arrowhead formation<|>Strep - beta hemolysin (completely hemolysis BAP)<|>Beta hemolysin and CAMP act in combination or synergistically
• Most Neisseria spp can ferment sugar
• Weak bubbling - if blood agar medium is accidentally included in the Catalase test
• Do not use mediums inoculated for more than 24 hours
• Neisseria is not limited to gonorrhea and they can spread hematogenously
• Sodium Polyanethol Sulfonate (SPS) - anticoag found in the blood; 0.02% is the only acceptable concentration to not inhibit the growth/cultivation of bacteria
• N. gonorrhoeae - urethral swab, vaginal secretions
• Almost ALL Cocci are Oxidase (-)
• If your patient is male and you find gram (-) cocci it is already presumptive/definitive that it is positive in N. gonorrhoeae. If female it is not definitive, since women have commensal organisms in their vagina which have the same morphology as N. gonorrhoeae (needs more culture)
• Cytochrome Oxidase Test


  An enzyme involved in electron transport, acts with the substrate (Cytochrome) it will oxidize, giving us a characteristic color<|>DO NOT USE IRON LOOP, it will cause a false positive reaction<|>Oxidase (+) - Purple; 5 - 10 secs; N. gonorrhoeae, Moraxella catarrhalis<|>Oxidase (-) - No color produced; E. coli
• Superoxol Test


  Bubbles in an "explosive" way, uses 30% Hydrogen peroxide instead of 3%<|>Reagent A - Sulfanilic Acid, Reagent B - Alpha naphthylamine<|>Formation of red color after adding Rgt A and Rgt B = POSITIVE<|>If the test is colorless/negative add zinc powder, still colorless - nitrate is further reduced in ammonia or nitrogenous gasses, red color formation - TRUE negative
• Serogrouping - MeninGitidis