Colony Morphology Appearances by Organism

Organism	BA	CHOC	CNA	MAC	ANO2	Gram
GRAM POSITIVES
Staphylococcus aureus	Small/med White/gold Beta-heme	Small/med White/gold	Small/med White/gold Beta-heme		Smaller White/gold Beta-heme	GPC clusters
Methicillin Resistant Staphylococcus aureus (MRSA)	May be grayer and non-heme	May be grayer	May be grayer and non-heme		May be grayer and non-heme
Coagulase-negative Staphylococcus (e.g., S. epidermidis)	Small/med White Non-heme	Small/med White	Small/med White Non-heme		Smaller White Non-heme	GPC clusters
Streptococcus pyogenes (GAS)	Small/med Gray Large beta-heme	Small/med Gray	Small/med Gray Large beta-heme		Small/med Gray Large beta-heme	GPC pairs & chains
Streptococcus agalactiae (GBS)	Small/med Gray Small beta-heme	Small/med Gray	Small/med Gray Small beta-heme		Small/med Gray Small beta-heme	GPC pairs & chains
Streptococcus pneumoniae	Small/med Gray Alpha-heme May checkerboard	Small/med Gray	Small/med Gray Alpha-heme May checkerboard		Small/med Gray Alpha-heme May checkerboard	GPDC or GPC pairs & chains (mostly pairs, larger/rounder/lancet-shaped)
Viridans streptococci	Smaller, opaquer than S. pneumoniae Alpha-heme	Smaller, opaquer than S. pneumoniae	Smaller, opaquer than S. pneumoniae Alpha-heme		Smaller, opaquer than S. pneumoniae Alpha-heme	GPC pairs & chains
Enterococcus spp.	Small/med Gray Non-heme	Small/med Gray	Small/med Gray Non-heme		Small/med Gray Non-heme	GPC pairs & chains
Corynebacterium spp.	Small White Non-heme	Small White	Small White Non-heme		Small White Non-heme	Small GPB in v's and palisades (may be club-shaped)
Listeria monocytogenes	Small/med Gray Small beta-heme	Small/med Gray	Small/med Gray Small beta-heme		Small/med Gray Small beta-heme	GPB (slim/short)
YEASTS (GRAM POSITIVE-LIKE)
Candida spp.	Small/med White Non-heme May have "feet"	Small/med White May have "feet"	Small/med White Non-heme May have "feet"		May not grow at 24h	Yeast
GRAM NEGATIVES
Enterobacterales
Escherichia coli	Large Gray Beta-heme	Large Gray		Large LF or NLF	Med/large Gray Beta-heme	GNB
Klebsiella pneumoniae	Large Gray Non-heme Mucoid	Large Gray Mucoid		Large LF Very mucoid	Med/large Gray Non-heme Mucoid	GNB
Pseudomonas aeruginosa	Large, flat Gray Beta-heme Metallic sheen	Large, flat Gray Metallic sheen		Large NLF Metallic sheen or green		GNB
Haemophilus spp.	NG or satellitism with S. aureus	Small White Non-heme				GNCB
Neisseria spp.	Small Gray Non-heme	Small Gray				GNDC
Moraxella spp.	Small White/gray Non-heme Gliding "hockey puck" colonies	Small White/gray Gliding "hockey puck" colonies				GNDC
ANAEROBES
Clostridium					Large, flat Gray Double-zone beta-heme	Large GPB (boxcar, large/thick, may have spores)
Peptostreptococcus spp.					Pinpoint/small Gray Non-heme	GPC pairs & chains
Bacteroides spp.					Small Gray Non-heme	GNB

Reporting CMI

These are the following organisms to report for CMI:

• Haemophilus spp.
• Neisseria/Moraxella spp.
• Listeria monocytogenes
• Corynebacterium spp.
• Bacillus spp. (non anthracis)
• Lactobacillus
• Yeast?

Fastidious gram negatives

Gram positive bacilli

• LBLC