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134 SEcTioN ii Microbiology ` microbiology—cliNical bacteriology Microbiology ` microbiology—cliNical bacteriology

` microbiology—cliNical bacteriology

Gram-positive lab algorithm

Gram (purple/blue)

Branching
Bacilli Cocci
filaments

Aerobic Anaerobic Aerobic Anaerobic

Listeria Clostridium
Bacillus Cutibacterium Nocardia Actinomyces
Corynebacterium (weakly acid fast) (not acid fast)
(formerly
Propionibacterium)
Catalase

(Pairs or Streptococcus (Clusters) Staphylococcus
chains)
Hemolysis Coagulase

α (Partial β (Complete γ (No hemolysis,
hemolysis,
hemolysis,
green) clear) grows in bile) S aureus
Novobiocin
Optochin sensitivity Bacitracin sensitivity Growth in 6.5% NaCl sensitivity
and bile solubility and PYR status and PYR Status

Group B Group A S saprophyticus S epidermidis
S agalactiae S pyogenes

Viridans streptococci
(no capsule) S pneumoniae Nonenterococcus Enterococcus
S mutans (encapsulated) S bovis E faecium
S mitis E faecalis
Important tests are in bold. Important pathogens are in bold italics.
Note: Enterococcus is either α- or γ-hemolytic.

Gram-positive cocci antibiotic tests
Staphylococci Novobiocin—Saprophyticus is Resistant; On the office’s “staph” retreat, there was
Epidermidis is Sensitive no stress
Streptococci Optochin—Viridans is Resistant; Pneumoniae is OVRPS (overpass)
Sensitive
Bacitracin—group B strep are Resistant; group B-BRAS
A strep are Sensitive

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