Culture Media: Blood Agar

-Culture on the standard media is the gold standard for the diagnosis of microbial keratitis
-The culture media used to culture the organisms should be stored in a
dedicated refrigerator and should be re-stocked frequently to avoid any contamination
-In order to enhance the recovery of the organisms, the media should be warmed to the room temperature to prevent lethal cold shock to the organism

METHOD OF INOCULATION:
-The corneal scrapings are routinely inoculated onto blood agar plate
-The selective media agar plates are inoculated by streaking the platinum spatula lightly over the surface to produce a row of separate inoculation marks in a C shaped configuration
-Fresh material should be obtained for each row of C streaks
-C streak method of inoculation differentiates valid growth from contamination as growth on the C streak is considered significant whereas outside this is a possible contamination


-Enriched media such as blood and chocolate agar help to isolate the fastidious organisms
-Blood agar is the standard medium for the isolation of aerobic bacteria at 35oC and helps to support the growth of most saprophytic fungi at room temperature
-The agar is derived from seaweed and produces optimal surface moisture, and addition of 5-10% red blood cells provides nutrients and an index of hemolysis
-Rabbit and horse serum are preferred for supporting the growth of Haemophilus
-The second slide shows the specific organisms that can be grown on blood agar


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Image from Rajan Eye Care Hospital

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