Corneal Scrape (Bacteriology)
Keratitis is an inflammation of the cornea which is a serious
condition requiring prompt and meticulous investigation, and may
progress to perforation and blindness if treatment is unsuccessful.
Predisposing factors include prior ocular disease, wearing contact
lenses and use of topical corticosteroids. The condition may be
caused by a wide range of bacteria, fungi and parasites.
Collection container (including preservatives):
Kits are available 24 hours a day from the stock fridge within
Autolab reception MRI; should infection with fungi or Acanthamoeba
be suspected additional kits are available from the Autolab
The scrape kit contains blood blobs, a chocolate plate, a glass
slide within slide carrier and an instruction sheet.
The kit label indicates when the kit expires; kits should not be
used after the expiry date and unused kits should be returned to
Specimen type: Aqueous and vitreous humour,
Collection: Use aseptic technique. For each
scrape of the eye a fresh needle must be used.
1. Preparing the Gram Stain:
Clear/wipe the infected area by removing as much cellular
material as possible using a syringe needle and spread this evenly
over the scribed area of the glass slide.
2. Innoculating the Culture plates and Blood Blobs:
Scrape the infected area using a fresh needle and inoculate the
surface of the agar with a large "C" streak. (Figure 1) (if
the syringe needle is dug deep into the agar this will delay signs
of bacterial growth)
Innoculate each agar blob using a fresh needle each time. Slide
and Choc agar and blobs MUST all be appropriately labelled.
Acanthameoba plates should be labelled on the lid of the plate as
labelling the agar side obstructs the visualisation of the plate
down the microscope.
Specimen transport: Specimens should be
transported and processed as soon as possible.
Minimum volume of sample: Corneal scrapings
should be of sufficient quantity to make a visible deposit on a
microscope slide and to inoculate culture plates.
If insufficient specimen to make an impression smear and
inoculate plates, cultures should be the priority.
Special precautions: Collect specimens before
antimicrobial therapy where possible.
Turnaround time: 24 - 72 hrs for culture. 30 -
60 mins for microscopy if telephoned in advance
Factors known to significantly affect the
results: Where media and smears are inoculated at the
patient's side they must be transported immediately to the
laboratory for processing.