STREP IDENTIFICATION CHART
Bacterial growth on Strep Culture Systems Media Hemolysis on Blood PYR Test Bacitracin Optochin Catalase Pathogenicity
Group A Strep ( Streptococcus pyogenes ) Beta
(clear zone)
Positive Zone of inhibition Zone
<14 mm
Negative Respiratory Pathogen
Group B, C, F, and G Strep (various Streptococcus spp.) Beta
(clear zone)
Negative Occasional zone of inhibition Zone
<14 mm
Negative Normally not a respiratory pathogen
Pneumococci ( Streptococcus pneumoniae ) Alpha
(green zone)
Negative Occasional zone of inhibition Zone
≥14 mm
Negative Respiratory pathogen
Viridans Strep ( Streptococcus viridans and others) Alpha
(green zone) or gamma (no zone)
Negative No zone Zone
<14 mm
Negative Normal respiratory flora
Enterococci ( Enterococcus spp., and Group D Strep) Alpha
(green zone) or gamma (no zone)
Positive No zone Zone
<14 mm
Negative (occasionally a weak positive) Normal respiratory flora

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