16
Table 1: Common Microbiota of the Respiratory Tract and Skin
ORGANISM
GRAM-STAINED
CELL MORPHOLOGY
COLONY
MORPHOLOGY, ETC.
Alpha-hemolytic
Streptococcus
Gram-positive cocci
in pairs and chains.
Small, dome-shaped, translucent
colonies surrounded by an area
of greenish discoloration, alpha
hemolysis. Not susceptible to
Taxo P disks.
Streptococcus
pneumoniae
Gram-positive, lancet-shaped
diplococci, in pairs and
hemolytic colonies.
Translucent, mucoid, small
glistening, medium, alpha chains.
Susceptible to Taxo P disks.
Beta-hemolytic
Streptococcus
Gram-positive cocci,
in pairs and long chains,
especially in broth.
Small, raised, translucent
colonies, surrounded by an area
of clear hemolysis, with a sharp
border.
Gamma-hemolytic
Streptococcus
Gram-positive cocci,
in pairs and chains.
Small, translucent, nonhemolytic colonies.
Staphylococcus
aureus
Gram-positive cocci,
in grape-like clusters.
Large, round, creamy-golden
tan colony, often with a zone
of clear hemolysis. Coagulase
positive.
Staphylococcus
epidermidis
Gram-positive cocci,
in grape-like clusters.
Large, round, white, opaque,
discrete colonies; usually not
hemolytic. Coagulase negative.
Neisseria spp.
(pharyngeal)
Gram-negative cocci,
in flattened pairs.
Small, white to yellowish,
smooth or dry, wrinkled colonies.
Oxidase positive.
Corynebacterium spp. Gram-positive., pleomorphic
(diphtheroids)
rods, some club-shaped; bipolar
or barred stain; groups form
"palisades."
Varies with species. Usually
smooth, convex, whitish, opaque,
non-hemolytic. Some wrinkled.
17
TABLE 1: Common Microbiota of the Respiratory Tract and Skin (cont.)
ORGANISM
GRAM-STAINED
CELL MORPHOLOGY
COLONY
MORPHOLOGY, ETC.
Haemophilus
influenzae
Very small gram-negative
coccobacilli with capsules
in young cultures. Older
cultures show longer rods and
pleomorphic forms, and lose
the capsule. Non-motile.
Small, round, convex, translucent,
oxidase-negative colonies appear
only on Chocolate agar (prefer
10% CO2) OR as satellite
colonies on blood agar, around
hemolytic S. aureus colonies.
Requires "X" & "V" factors
(hemin and NAD or NADP).
Haemophilus spp.
Small gram-negative
rods, short or long chains,
often pleomorphic
Small, smooth, opaque colonies.
Most require X and/or V factors
from blood-based enriched medium.
Gram-negative
enteric rods
e.g. Klebsiella
Gram-negative rods,
usually larger than
above spp.
Usually large, gray, glistening
colonies. Will grow on
MacConkey's (Pink if Lac positive).
Gram-negative rods, Gram-negative bacilli
non-fermentative
or coccobacilli.
e.g. Alcaligenes,
Acinetobacter.
Small, gray, glistening colonies.
No reaction in TSI butt.
Micrococcus luteus
Lemon-colored colony. Common
flora of skin.
Gram-positive cocci,
usually in tetrads.