staph and strep. cocci morphology catalase test enzyme –catalase –(+) bubbles staphylococcus...
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Catalase Test
• Enzyme– Catalase– (+) bubbles
• Staphylococcus
– (-) no bubbles• Streptococcus• Enterococcus
• Detoxify hydrogen peroxide
• H2O2 H2O + O2
MSA
• Selective– 7.5 % NaCl, halotolerant– Staphylococci
• Differential– pH indicator: phenol red– Mannitol
• Fermentation – Acid end products
– Yellow
• Non fermentation = red
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
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
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
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
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