Pythium keratitis in South India: Incidence, clinical profile, management, and treatment recommendation

Abstract

Purpose: To study the demographic profile, clinical features, treatment outcome, and ocular morbidity of microbiologically proven Pythium keratitis in South India.

Methods: A retrospective analysis of clinical records of microbiologically proven Pythium keratitis at a tertiary eye care referral center in South India from January 2016 to November 2017 was performed. Demographic details, predisposing risk factors, microbiological investigations, clinical course, and visual outcome were analyzed.

Results: Seventy-one patients with microbiologically proven Pythium keratitis were identified. The mean age was 44(±18.2) years with an increase in male preponderance and 50% were farmers. Duration of delay at time of presentation to the hospital was a mean of 14(±7.2) days. The visual acuity at baseline ranged from 6/6 to no light perception (median 2.1 logMAR). A combination of 5% natamycin and 1% voriconazole was given to 42% patients, and natamycin alone was given to 39.4% patients. 1% itraconazole eye drops alone was initiated in 7 (10%) patients and 3 among this group responded. Therapeutic keratoplasty (TPK) was performed in 48 (67.6%) patients. None of the primary grafts remained clear after a period of 1 month. Twenty-six eyes (54.2%) had graft reinfection and all these eyes either developed anterior staphyloma (4) or were eviscerated (3) and 13 eyes became phthisical. The remaining 22 patients who had TPK resulted in failed graft. Among these, re-grafts were performed in 6 patients, of which 5 were doing well at the last follow-up.

Conclusion: We report a large series of patients with Pythium keratitis. Promoting early and differential diagnosis, awareness of clinicians and specific treatment options are needed for this devastating corneal disease.

Keywords: DNA sequencing; ITS; Pythium insidiosum; keratitis; therapeutic penetrating keratoplasty.

Figure 1

Bar diagram represents the seasonal observation of 71 culture positive Pythium keratitis cases seen at tertiary eye care center in South India from January 2016 to November 2017

Figure 2

Clinical findings of patients with Pythium keratitis. Slit-lamp picture of the cornea showing (a) central, dense, grayish-white infiltrate with tentacle-like lesions. (b) Diffuse dot-like infiltrates emanating from the main infiltrate extending to the peripheral cornea. In addition peripheral furrowing is seen in this picture inferiorly from 4^o clock to 7^o clock hour. (c) Large dense infiltrate with dot like multiple infiltrates with peripheral furrowing from 2^o clock to 4^o clock hours with 1 mm hypopyon. (d) Dense grayish white infiltrate with peripheral furrowing seen from 7^o clock to 9^o clock hours. Tentacle like extensions and subepithelial dot like infiltrates seen extending from the main infiltrate

Figure 3

(a) 10% KOH wet mount preparation of corneal scraping showed long sparsely septate hyaline hyphae of Pythium insidiosum. The presence of numerous vesicles within the hyphae is usually observed. (b) Gram stain image showed the thick cell wall, a few septate, and mass of vesicles inside. (c) A 3 day old culture of P. insidiosum at 37°C grown on 5% sheep blood agar. (d) A vesicles with zoospores that developed after 3 h incubation before zoospore release (×10)

Fig. 4

Amplification of a 495 bp specific DNA fragment of the ITS1 and ITS4 region of Pythium fungal DNA. MW: Molecular weight marker (100 bp); NC: Negative control; Lane S1-S5: Amplified Pythium fungus DNA (495bp); PC: Positive control