Staph and Strep Cocci Morphology Catalase Test Enzyme

Staph and Strep

Cocci Morphology

Catalase Test • Enzyme – Catalase – (+) bubbles • Staphylococcus – (-) no bubbles • Streptococcus • Enterococcus • Detoxify hydrogen peroxide • H 2 O 2 H 2 O + O 2

Columbia - CNA • Selective for GP – Colistin – Nalidixic Acid • Differential – Blood hemolysis

BAP: Hemolysis Alpha Gamma

BAP Hemolysis: Beta

Gram Stain: Staph

MSA • Selective – 7. 5 % Na. Cl, halotolerant – Staphylococci • Differential – p. H indicator: phenol red – Mannitol • Fermentation – Acid end products – Yellow • Non fermentation = red

MSA

DNase • Differential • Dye – Methyl green – p. H 7. 5 • Enzyme – hydrolytic – DNase • Results – Clear zone = (+)

Mueller-Hinton Agar (MH) • AB sensitivity • Novobiocin Disc – Sensitive > 18 mm – Resistant < 18 mm • Staph chart for ID

Staph Tri-plates • Mannitol – Growth – NF • DNAse (+) • Novobiocin (S)

Staph Tri-Plates • Mannitol – Growth – Fermentation • DNAse (+) • Novobiocin (S)

Staph Tri-plate • Mannitol – Growth – NF • DNAse (-) • Novobiocin (R)

Staph Tri-plate • Mannitol – Growth – Fermentation • DNAse (-) • Novobiocin (R)

Coagulase Test • Staph aureus • Converts fibrinogen to fibrin • Immune defense – Protection from phagocytosis

Rapid Staph Test • Staph aureus • Virulence Factors – Coagulase (+) • Fibrinogen Fibrin • Clots – Protein A • Fc regions of Ig. G • Inhibits Ab • Results – Color Change – Clumping

Anaerobic Systems • Facultative Anaerobes – Staph • Capnophiles – Strep

Streptococcus • • • GP cocci Chains Catalase (-) Capnophiles Groups – Lancefield Groups – Surface Antigens

Lancefield Strep Classifications • Group A – S. pyogenes • Group B – S agalactia • Group C – S. equi • Group D – Enterococcus faecalis – S. bovis • Group K – S. salivarius • Viridans – S. mutans – S. mitis • Pneumoocci – S. pneumoniae

Catalase and MSA • Catalase (-) • MSA – No growth • Not halotolerant – Except • Enterococcus (-)

Hemolysis Types

Bacitracin and SXT Sensitivities

Zone of Inhibition

Ab Sensitivities • Bacitracin – Any zone = Sensitive – No clearing = Resistant • SXT – Zone > 20 mm = S – Zone < 20 mm = R

Bile Esculin • Selective – Bile salts – Enteric organism growth • Differential – Hydrolyze esculin (CH 2 O) – Reacts with Fe. NH 3 -citrate • Results – Growth – Black precipitate

CAMP Identify Group B Strep (GBS) CAMP factor enhances hemolysis Arrow Head produced for GBS

Rapid Strep Test • Group A Strep • Immunoassay – Ag ID – Ab on test strip • Results – Color change

Flow Chart