Polymerase chain reaction based detection of fungi in infected corneas

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CLINICAL SCIENCE

Polymerase chain reaction based detection of fungi in infected

corneas

P A Gaudio1,*, U Gopinathan2, V Sangwan2 and T E 1

1 Yale Eye Center, New Haven, CT, USA

2 LV Prasad Eye Institute, Hyderabad, India

http://bjo.bmjjournals.com/cgi/content/abstract/86/7/755

Correspondence to:

E , PhD, Yale Eye Center, 330 Cedar Street, New Haven,

CT 06520, USA;

thomas.hughes@...

Aims: To evaluate a polymerase chain reaction (PCR) based assay to

detect fungi in scrapings from infected corneas.

Methods: A PCR assay was developed to amplify a portion of the

fungal 18S ribosome gene. Corneal scrapings from 30 patients with

presumed infectious keratitis were evaluated using this assay, as

well as by standard microbiological techniques, and the results were

compared. Conjunctival swabs from each patient's healthy, fellow eye

were also evaluated by PCR.

Results: PCR and fungal culture results matched (were both positive

or both negative for fungi) in 22 (74%) of 30 scrapings from

infected corneas. Three (10%) of 30 samples were PCR positive but

fungal culture negative; two of these appeared clinically to

represent fungal infections, and the third was clinically

indeterminate. Four (13%) scrapings were positive by PCR but also by

bacterial and not fungal culture. One specimen (3%) was PCR negative

but fungal culture positive. Of the conjunctival swabs from each

patient's healthy fellow eye, five (17%) of 30 were positive by PCR,

and the opposite, infected eye of all five of these harboured a

fungal infection.

Conclusions: PCR is promising as a means to diagnose fungal

keratitis and offers some advantages over culture methods, including

rapid analysis and the ability to analyse specimens far from where

they are collected.