Satellite Phenomenon
by Roseann Camp, MT(ASCP),
and Rosemarie Camp
Recall:
Microbiology
The photograph (Fig. 1) is of a
sheep blood agar plate on which
are growing colonies from a 48hour culture of material taken
from an infected eye of an infant.
Questions
1. Based on their colonial morphology,
what is the presumptive identification of the
larger colonies?
Fig. 7. Specimen
of an
infected
eye on sheep
blood agar.
2. To which bacterial genus do
the smaller colonies
most
likely belong?
3. Explain the phenomenon
satellitism.
of
Answer
The larger, w h i t e , c o n v e x ,
opaque colonies morphologically
are suggestive of staphylococci.
The satellite phenomenon occurs
when one bacterial species produces growth factors required by
a second species when these
Roseann Camp, MT(ASCP), is working in a
private pediatric laboratory in Richardson,
Texas.
nutrients are not available in the
culture media itself. In the case
cited, colonies satelliting around
staphylococci on a sheep blood
agar plate most commonly point
to one of the species of Haemophilus that require NAD (Factor
V) for g r o w t h . Factor V is deficient in sheep blood agar due
to the release of NAD'ases from
the sheep erythrocytes during
storage. Many strains of staphylococci synthesize Factor V thereby
supporting the satellite growth of
NAD-dependent strains of Haemophilus adjacent to the staphylococcus colonies.
This satellite phenomenon is
helpful in the primary recovery
of Haemophilus
sp. from specimens where media rich in Factor
V had not been used.
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0007-5027/79/0100/051 $00.55 © American Society of Clinical Pathologists
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