Reham Mohamed EL SHABRAWY, Nissreen El Sayed El BADAWY, Ashraf Wasfy HARB

Mısır, Zagazig Üniversitesi Hastaneleri'nde fungal keratit insidansı ve hızlı tanısında direkt mikroskopi ve PCR tekniğinin yeri

Amaç: Fungal keratit (FK) sıklığının, risk faktörlerinin ve korneal örneklerin direkt mikroskopi ile incelenmesi ve PCR tekniğinin tanı değerinin araştırılması.Yöntemler: Mısır'da, Zagazig Üniversitesi Hastaneleri Göz Hastalıkları Departmanı'nda Ocak-Haziran 2012 arasında keratit tanısı alan hastalar çalışmaya alındı. Korneal örnekler %10 KOH preparasyon yöntemi ile direkt mikroskopi ile incelendi, ayrıca örnekler PCR ile fungal DNA varlığı açısından test edildi vekültür plaklarına ekim yapıldı. Korneal smear direkt mikroskopi ve PCR bulguları kültür sonuçları ile testlerin duyarlılığı, güvenirliği, uygunluğu ve tahmin değerleri açısından karşılaştırıldı.Bulgular: Çalışma süresince toplam 350 hasta keratit olarak değerlendirilerek bunlardan 60 tanesi rastgele örnekleme yöntemiyle çalışmaya dâhil edildi. Toplam 60 hastanın 33'ünde (% 55,0) kültürde fungus üremesi ile FK tanısı doğrulandı. Göz travması en sık predispozan faktör olarak değerlendirildi (% 63,6). En sık fungal ajan Penicillium spp. idi (% 24,2) ve bunu Aspergillus fumigatus (% 21,2) takip etti. Direkt mikroskopinin FK tanısında duyarlılığı % 100, özgüllüğü %66,7, pozitif tahmin değeri (PPV) % 78,6 ve negatif tahmin değeri (NPV) % 100 olarak hesaplandı. PCR tekniğinin ise duyarlılığı % 100, özgüllüğü % 88,9, PPV % 91,7 ve NPV % 100 olarak hesaplandı.Sonuçlar: FK tanısında PCR, kültür negatif olgularda önemli oranda fungal etiyolojiyi gösterebilmesine rağmen, pahalı olması sebebiyle FK tanısında rutin tanısal test yöntemi olarak kullanılamayacağını, bunun yerine daha ekonomik, daha hızlı ve duyarlı bir yöntem olan korneal örneklerin direkt mikroskopik incelemesinin daha uygun olduğunu düşünüyoruz.

The incidence of fungal keratitis in Zagazig University Hospitals, Egypt and the value of direct microscopy and PCR technique in rapid diagnosis

Objective: To determine the frequency and risk factors of fungal keratitis (FK) and the value of direct microscopy and PCR techniques of corneal smears as appropriate diagnostic methods.Methods: The keratitis cases in Ophthalmology Department of Zagazig University Hospitals, between January and June 2012 were enrolled. Corneal samples were examined by direct microscopic examination of wet mount preparation with KOH (10%), PCR technique and cultured simultaneously. The corneal smear and PCR findings were compared to the culture results to analyze specificity, sensitivity and predictive values of these techniques.Results: A total of 350 patients diagnosed as keratitis and 60 of them were included in the study by a systemic random sampling method. The FK was proven in 33 (55%) cases with culture results. Ocular trauma (63.6%) was the most prevalent predisposing factor. The cultures revealed that the most frequent fungal pathogen were Penicillium spp. (24.2%) followed by Aspergillus fumigatus (21.2%). Direct microscopic examination had a sensitivity of 100%, specificity of 66.7%, a positive predictive value (PPV) of 78.6% and a negative predictive value (NPV) of 100%. PCR had a sensitivity of 100%, specificity of 88.9%, a PPV of 91.7% and a NPV of 100%.Conclusion: Although, PCR is able to detect fungi in a high proportion of culture negative cases, it is difficult to be used as a routine diagnostic test due to the economic reasons. Therefore, we strongly recommend the use of direct microscopy of corneal smear as a rapid, economic and sensitive method for screening of FK. J Microbiol Infect Dis 2013;3(4)186-191

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1. Tilak R, Singh A, Maurya OP, et al. Mycotic keratitis in India: a five-year retrospective study. J Infect Dev Ctries 2010;4:171- 174.
2. Nath R, Baruah S, Saikia L, et al. Mycotic corneal ulcers in upper Assam. Indian J Ophthalmol 2011;59:367-371.
3. Keay LJ, Gower EW, Iovieno A, et al. Clinical and microbiological characteristics of fungal keratitis in the United States, 2001-2007: a multicenter study. Ophthalmology 2011;118:920-926.
4. Saad-Hussein A, El-Mofty HM, Hassanien MA. Climate change and predicted trend of fungal keratitis in Egypt. East Mediterr Health J 2011;17:468-473.
5. Thomas PA. Fungal infections of the cornea. Eye 2003;17:852- 862.
6. Xie L, Dong X, Shi W. Treatment of fungal keratitis by penetrating keratoplasty. Br J Ophthalmol 2001;85:1070-1074.
7. Ferrer C, Alió JL. Evaluation of molecular diagnosis in fungal keratitis. Ten years of experience. J Ophthal Inflamm Infect 2011;1:15-22.
8. Galarreta D, Tuft S, Ramsay A, and Dart J. Fungal keratitis in London: microbiological and clinical evaluation. Cornea 2007;26:1082-1086.
9. Winn W, Allen S, Janda. Mycology. In: Winn WC, Koneman EW, Janda WM, Koneman EW eds. Koneman's Colored Atlas and Textbook of Diagnostic Microbiology, 6th edn. Philadelphia:Lippincott Williams and Wilkins, 2006:1151- 1243.
10. Sharma S, Kunimoto DY, Gopinathan U, et al. Evaluation of corneal scraping smear examination methods in the diagnosis of bacterial and fungal keratitis: a survey of eight years of laboratory experience. Cornea 2002;21:643-647.
11. Kim E, Chidambaram JD, Srinivasan M, et al. Prospective comparison of microbial culture and polymerase chain reaction in the diagnosis of corneal ulcer. Am J Ophthalmol 2008;146:714-723.
12. Willinger B, Obradovic A, Selitsch B, et al. Detection and identification of fungi from fungus balls of the maxillary sinus by molecular techniques. J Clin Microbiol 2003;41:581-585.
13. Vemuganti GK, Garg P, Gopinathan U, et al. Evaluation of agent and host factors in progression of mycotic keratitis: A histologic and microbiologic study of 167 corneal buttons. Ophthalmology 2002;109:1538-1546.
14. Shukla PK, Kumar M, Keshava GB. Mycotic keratitis: an overview of diagnosis and therapy. Mycoses 2008;51:183- 199.
15. Mahdy RA, Nada WM, Wageh MM. Topical amphotericin B and subconjunctival injection of fluconazole (combination therapy) versus topical amphotericin B (monotherapy) in treatment of keratomycosis. J Ocul Pharmacol Ther 2010;26:281-285.
16. Tuft SJ, Tullo AB. Fungal keratitis in the United Kingdom 2003-2005. Eye (Lond) 2009;23:1308-1313.
17. Bharathi MJ, Ramakrishnan R, Vasu S, et al. Epidemiological characteristics and laboratory diagnosis of fungal keratitis. A three-year study. Indian J Ophthalmol 2003;51:315-321.
18. Alkatan H, Athmanathan, Canites CC. Incidence and microbiological profile of mycotic keratitis in a tertiary care eye hospital: A retrospective analysis. Saudi J of Ophthalmol 2012;26:217-221.
19. Xu LJ, Song XS, Zhao J, et al. Hypopyon in patients with fungal keratitis. Chin Med J (Eng) 2012;125:470-475.
20. Basak SK, Basak S, Mohanta A, Bhowmick A. Epidemiological and microbiological diagnosis of suppurative keratitis in Gangetic West Bengal, eastern India. Indian J Ophthalmology 2005;53:17-22.
21. Shokohi T, Nowroozpoor-Dailami K, Moaddel-Haghighi T. Fungal keratitis in patients with corneal ulcer in Sari, Northern Iran. Arch Iran Med 2006;9:222-227.
22. Sengupta J, Khetan A, Saha S, et al. Candida keratitis: emerging problem in India. Cornea 2012;31:371-375.
23. Bharathi M J, Ramakrishnan R, Meenakshi R, et al. Microbiological diagnosis of infective keratitis: comparative evaluation of direct microscopy and culture results. Br J Ophthalmol 2006;90:1271-1276.
24. Eleinen KG, Mohalhal AA, Elmekawy HE, et al. Polymerase chain reaction-guided diagnosis of infective keratitis - a hospital-based study. Curr Eye Res 2012;37:1005-1011.
25. Tananuvat N, Salakthuantee K, Vanittanakom N, et al. Prospective comparison between conventional microbial workup vs PCR in the diagnosis of fungal keratitis. Eye (Lond) 2012;26:1337-1343.
26. Embong Z, Wan Hitam WH, Yean CY, et al. Specific detection of fungal pathogens by 18S rRNA gene PCR in microbial keratitis. BMC Ophthalmol 2008;8:7.