Staph and Strep

Cocci Morphology

Catalase Test

• Enzyme– Catalase– (+) bubbles

• Staphylococcus

– (-) no bubbles• Streptococcus• Enterococcus

• Detoxify hydrogen peroxide

• H2O2 H2O + O2

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 % NaCl, halotolerant– Staphylococci

• Differential– pH indicator: phenol red– Mannitol

• Fermentation – Acid end products

– Yellow

• Non fermentation = red

MSA

DNase

• Differential• Dye

– Methyl green– pH 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 IgG• 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 (CH2O)– Reacts with FeNH3-citrate

• Results– Growth– Black precipitate

CAMP

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

Rapid Strep Test

• Group A Strep• Immunoassay

– Ag ID– Ab on test strip

• Results– Color change

Flow Chart