Optochin discs and resp specimens
"Miller, J. Michael PhD ", Mike
JMM8 at CIDHIP1.EM.CDC.GOV
Mon Jan 9 08:15:03 EST 1995
Recently, a question was asked on the net about using optochin disks on the
initial inoculum of a sputum culture.
Optochin disks are not placed on the initial inoculum of sputum
cultures. In fact, the test requires a pure culture inoculum and careful
measuring of zone size to determine results. After incubation in CO2, a 6-mm
disk must produce a zone of 14-mm or more before calling the strain a
pneumococcus. A zone less than 14-mm is "questionable" for pneumococci and
must be confirmed some other way. If you use a 10-mm disk, the zone size for
a pneumococcus must be at least 16-mm. You can't do this test accurately on
mixed culture streaks from direct specimens.
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