Use of chlorazol black E mounts of corneal scrapes for diagnosis of filamentous fungal keratitis.
OBJECTIVE
To determine whether chlorazol black E, a chitin-specific stain, can be used to detect fungal filaments in corneal scrapings and to compare its sensitivity as a diagnostic aid for fungal keratitis with that of gram and lactophenol cotton blue stains.


METHODS
Prospective study, laboratory investigation.


METHODS
Between December 1, 2005 and July 31, 2006, corneal scrapes from 163 patients with ulcerative keratitis were used for culture and to prepare smears that were stained by lactophenol cotton blue, chlorazol black E, or gram stains. A diagnosis of fungal keratitis was established if fungal growth occurred on the inoculated areas of multiple culture plates.


RESULTS
Fungi were isolated from corneal scrapes of 82 patients. Taking fungal culture positivity as the gold standard for diagnosis of fungal keratitis, direct microscopic examination of chlorazol black E mounts had a sensitivity of 82% and specificity of 98%; culture results and chlorazol black E results were identical in 89.6% of patients. Lactophenol cotton blue mounts and gram-stained smears had a sensitivity of 85%, specificity of 90% to 91%, and 88% agreement with culture results.


CONCLUSIONS
Chlorazol black E can be used for detection of fungal filaments in corneal scrapings; however, it is less sensitive than lactophenol cotton blue and gram stains as a diagnostic aid for fungal keratitis.
Thomas
Philip Aloysius
PA
Department of Microbiology, Institute of Ophthalmology, Joseph Eye Hospital, Tiruchirapalli, Tamil nadu, India. philipthomas@satyam.net.in
Kaliamurthy
Jayaraman
J
Jesudasan
Christadoss Arul Nelson
CA
Geraldine
Pitchairaj
P
D001391:Azo Compounds / Q000494:pharmacology*; D004396:Coloring Agents / Q000494:pharmacology*; D003315:Cornea / Q000382:microbiology*; D003320:Corneal Ulcer / Q000175:diagnosis* / Q000382:microbiology; D015821:Eye Infections, Fungal / Q000175:diagnosis* / Q000382:microbiology; D005188:False Negative Reactions; D005658:Fungi / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification; D006801:Humans; D016533:Mycological Typing Techniques; D009181:Mycoses / Q000175:diagnosis* / Q000382:microbiology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling
D001391:Azo Compounds; D004396:Coloring Agents; C015844:direct black 3