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Detection of Aspergillus keratitis in ocular infections by culture and molecular method
Parisa Badiee1, Abdolvahab Alborzi, Mahmood Nejabat
1Prof. Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Zand Ave, Nemazi Hospital, 7193711351, Shiraz, Iran. Badieep@yahoo.com
Abstract:
The incidence of fungal keratitis has increased in recent years. Since accurate and rapid diagnosis is important for the proper management of this infection, we evaluated the use of nested PCR to detect Aspergillus-specific DNA in corneal scrapings for the diagnosis of Aspergillus keratitis. From April 2005 to September 2008, patients with eye findings suspicious for fungal keratitis were enrolled for corneal sampling. After ocular examination, we carried out laboratory testing including direct microscopy and culture examination of corneal scrapings, nested PCR and histopathological examination of the corneal tissues obtained at surgery. Of the 57 infected eyes suspicious for fungal keratitis, 32 (56.14%) were reported as Aspergillus keratitis by PCR assay, from which 12 (37.5%) were positive in culture and direct smear for Aspergillus keratitis, and 20 (62.5%) had clinical signs of fungal keratitis (probable). All PCR-positive cases were judged to have fungal infections, based on their responses to the antifungal treatment. The use of molecular methods in high-risk patients can be helpful in diagnosis of fungal infections and can have important public health implications for both the treatment and prevention of suppurative corneal ulcerations. The significance of this study lies in the analysis of the proven cases in terms of both laboratory findings and responses to the treatment.
Insights
Nested PCR accurately detects Aspergillus keratitis in corneal scrapings, improving diagnosis for fungal eye infections. This molecular method aids in timely treatment and prevention of serious corneal ulcers.
Area of Science:
- Ophthalmology
- Medical Mycology
- Molecular Diagnostics
Background:
- Fungal keratitis incidence is rising, necessitating rapid and accurate diagnostic methods.
- Early diagnosis of fungal keratitis is crucial for effective patient management and preventing vision loss.
- Aspergillus species are a common cause of fungal keratitis, particularly in certain geographical regions.
Purpose of the Study:
- To evaluate the diagnostic utility of nested PCR for detecting Aspergillus-specific DNA in corneal scrapings.
- To compare nested PCR results with conventional diagnostic methods like microscopy and culture.
- To assess the clinical significance of nested PCR in diagnosing Aspergillus keratitis.
Main Methods:
- Corneal scrapings and tissue samples were collected from patients with suspected fungal keratitis.
- Nested PCR was employed to detect Aspergillus-specific DNA.
- Conventional methods including direct microscopy, culture, and histopathology were performed for comparison.
- Clinical data and treatment responses were analyzed for all cases.
Main Results:
- Nested PCR identified Aspergillus keratitis in 56.14% (32/57) of suspected cases.
- Of PCR-positive cases, only 37.5% (12/32) were positive by culture or direct smear, highlighting PCR's sensitivity.
- All PCR-positive cases responded to antifungal treatment, confirming the diagnosis.
- Nested PCR demonstrated higher sensitivity compared to conventional methods for Aspergillus keratitis detection.
Conclusions:
- Nested PCR is a sensitive and valuable tool for the rapid diagnosis of Aspergillus keratitis.
- Molecular methods like nested PCR can significantly improve the diagnosis of fungal eye infections, especially in culture-negative cases.
- Accurate diagnosis through nested PCR has public health implications for managing and preventing suppurative corneal ulcerations.
