bacte strep biochemical test

• Catalase Test

  • Reagent: 3% H2O2
  • Positive Result: Effervescence or bubbling formation
  • Positive (+): Staphylococci
  • Negative (-): Streptococci
• Bacitracin Disk Test/Taxo A (0.04 units)

  • Differentiates Beta-hemolytic groups of streptococci
  • Positive Result: susceptible – any zone of inhibition (>10mm)
  • SUSCEPTIBLE (+): Group A (S. pyogenes)
  • RESISTANT (-): Group B (S. agalactiae), Group C & D
• Sulfamethoxazole and Trimethoprim (SXT) Test

  • Presumptive test for the identification of Group A streptococci
  • SUSCEPTIBLE (+): Group C S
  • RESISTANT (-): Group A (S. pyogenes), B (S.agalactiae), & D
• Pyrrolidonyl arylamidase (PYR) Test

  • More specific than bacitracin test in identification of S. pyogenes from other beta-hemolytic groups.
  • Positive: S. pyogenes - ONLY β –hemolytic Strep spp POSITIVE to PYR.
  • Positive Result (+): Cherry Red Color
• CAMP Test (Christie, Atkins, Munch-Peterson) is used to differentiate S. agalactiae from other β-hemolytic streptococci
• CAMP (Christie, Atkins, Munch-Peterson) Test

  • Test for synergistic hemolysis between Group B Streptococcus and β-hemolytic S. aureus (reagent organsm)
  • β-hemolytic S. aureus is streak down the center of BAP while test organism is steak PERPENDICULARLY to the reagent organism
• CAMP (Christie, Atkins, Munch-Peterson) Test

  • Performed in an aerobic environment and the BAP is incubated at 35 – 37°C overnight
• CAMP (Christie, Atkins, Munch-Peterson) Test

  • Positive Result: Arrow-head or bowtie-shaped beta-hemolysis near S. aureus growth.
  • Positive (+): Group B (S. agalactiae)
• Hippurate Hydrolysis Test

  • Differentiate S. agalactiae from other β-hemolytic streptococci.
  • S. agalactiae possesses the enzyme hippuricase or hippurate hydrolase
• Hippurate Hydrolysis Test

  • Reagent: SODIUM HIPPURATE & NINHYDRIN
  • Determines hydrolysis of sodium hippurate to benzoic acid & glycine
  • Glycine can be detected with Ninhydrin reagent.
• Hippurate Hydrolysis Test

  • Positive Result: PURPLE COLOR after adding ninhydrin reagent.
  • Positive (+): Group B (S. agalactiae)
  • Negative Resilt: NO COLOR CHANGE
  • Negative (-): Group A (S. pyogenes)
• Bile Esculin Hydrolysis

  • Determines the capacity of an organism to grow in the presence of increased (40%) bile salts & the ability to hydrolyze esculin to esculetin
  • Differentiates Group D Enterococcus from Non-enterococcus.
• Bile Esculin Hydrolysis

  • Reagent: Esculin and 40% bile salt
  • Positive Result: Esculetin reacts with Ferric chloride to form dark brown to black precipitate
  • Positive (+): Group D Enterococcus & Non-enterococcus
• Salt (6.5% NaCl) Tolerance Test (Nutrient Broth Base)

  • Ability of the organism to grow in high concentration of salts
  • Positive Result: Growth of the organism (TURBIDITY)
  • Positive (+): Enterococci
  • Negatve (-): Non-enterococci & Group D Streptococci
• Optochin (Taxo P) Susceptibility test

  • Aka Ethylhydrocuprein Hydrochloride (5uq)
  • Optochin lyses pneumococci but other alpha hemolytic streptococci are resistant.
  • Medium: BAP
• Optochin (Taxo P) Susceptibility test

  • Positive Result: SUSCEPTIBLE - zone of inhibition greater than 14mm.
  • Positive (+): Streptococcus pneumoniae
  • Negative (-): Viridans streptococci
• Bile Solubility Test

  • Differentiates Streptococcus pneumoniae from alpha-hemolytic streptococci.
  • Determines the presence of autocatalytic enzyme amidase in S. pneumoniae to lyse (autolysis) in the presence of bile salts.
• Bile Solubility Test

  Reagent: 10% sodium deoxycholate (BAP) or 2% sodium deoxycholate (test tube)
• Bile Solubility Test

  • Positive Result (A): Colony lyses or disintegrates; an imprint of the lysed colony may remain in the zone
  • Positive (+): S. pneumoniae - soluble
  • Negative (B): Intact colonies
  • Negative (-): Viridans Streptococci - insoluble
• Leucine Aminopeptidase (LAP) Test

  • Presumptive test for catalase- negative, Gram-positive cocci
  • Substrate: Leucine-beta-naphthylamide
• Leucine Aminopeptidase (LAP) Test

  Reagent: p-dimethylaminocinnamaldehyde (DMACA)
• Leucine Aminopeptidase (LAP) Test

  • Positive (+): RED COLOR – Viridans streptococci, Enterococci, S. pyogenes, S. agalactiae, and S. pneumoniae
  • Negative (-): NO COLOR CHANGE - Aerococcus and Leuconostoc
• Voges-Proskauer (VP) Test

  • Medium: MRVP Broth
  • Reagents: 5% alpha-naphthol & 40% KOH
  • End product: Acetoin
  • Positive Result: Deep pink or red color
  • Positive (+): S. bovis & S. mutans groups