Posaconazole in the treatment of refractory Purpureocillium lilacinum (former Paecilomyces lilacinus) keratitis: the salvation when nothing works

Abstract

We report a case of a 41-year-old woman, wearer of contact lenses who was presented to the emergency room with a 2-month history of pain and red eye. She presented with a severe keratitis refractory to quinolones, fortified antibiotics and clotrimazole. Due to the risk of perforation, a tectonic penetrating keratoplasty (PK) was performed. Clinical signs of keratitis recurrence were observed and cultures were positive for Purpureocillium lilacinum (former Paecilomyces lilacinus). The patient did not improve on topical amphotericin B and intracameral voriconazole. Worsening of clinical condition required a new PK. Oral posaconazole was initiated postoperatively and suspended at the fourth postoperative month. The cornea remains clear until the last follow-up visit, 12 months after the second graft. To our knowledge, this is the second case report that documents the effectiveness of oral posaconazole in a refractory P. lilacinus keratitis, resistant to other second-generation triazoles and conventional antifungals.

Background

Paecilomyces lilacinus is a rare cause of fungal keratitis. Due to molecular studies, this fungus was recently reclassified and is currently denominated Purpureocillium lilacinum. ¹ It is a saprophytic fungus mainly found in soil, air, wood and decomposing plants.² However, it can also be found as a contaminant of antiseptic skin lotions and solutions used as sterilisers for artificial lenses.^{3 4} According to previous studies, one of the most frequent manifestations of P. lilacinum is keratitis.⁵ The ocular infection occurs mainly in patients with predisposing factors, namely chronic keratopathy, previous ocular surgery, corneal trauma or contact lens wear.^5–7

Keratitis may present several clinical and histologic characteristics suggestive of fungal infection. Fungus identification is crucial for the establishment of therapy but can only be obtained using microbiology techniques. The success of the microbiological procedures is dependent on correct practices for sample collection and on laboratory methodologies.⁸

Corneal isolates of P. lilacinus are usually resistant to amphotericin B or natamycin. As a result of its poor response to conventional antifungal therapies, Paecilomyces keratitis is often devastating and frequently requires penetrating keratoplasty (PK).⁹

Triazole antifungals, such as voriconazole, demonstrated to be much more effective than conventional antifungals in the treatment of P. lilacinus keratitis.^{10 11} Posaconazole, a triazole antifungal, has shown to be effective in the treatment of P. lilacinus infection, in a murine model.¹² In addition, it has recently been used in a case of relapsing keratitis due to P. lilacinus with good response.¹³

We report a case of severe fungal keratitis by P. lilacinus in a contact lens wearer, non-responsive to the commonly used antifungals and voriconazole, which was successfully treated with sequential PK and oral posaconazole.

Case presentation

A 41-year-old woman presented with a 2-month history of pain and red eye in the left eye. She was under topical treatment with ofloxacin 3 mg/mL (six times a day) and clotrimazole 10 mg/mL (four times a day) for the previous 3 weeks without performing corneal cultures. She had worn soft contact lenses for 11 years, with poor hygiene care. No prior history of ocular infections was reported. At presentation in our department, her best-corrected visual acuity (BCVA) was hand motion in the left eye and 20/20 in the right eye. Slit-lamp examination demonstrated a 5×3 mm central corneal epithelial defect, a surrounding infiltrate, stromal oedema, hypopyon and marked ciliary and conjunctival injection. Anterior segment optical coherence tomography (AS-OCT) revealed a deep corneal infiltrate and stromal thinning in the affected area (figure 1A and B). Posterior segment involvement was excluded by ultrasound sonography. Microbial specimens were collected from the corneal infiltrate by scraping the lesion with a surgical blade under local anaesthesia. According to our laboratory protocol, three samples were collected and cultured using blood agar, chocolate agar and Sabouraud/Chloramphenicol Agar Plates that were incubated at 37°C. Blood and chocolate agar plates were used to exclude the presence of bacteria and Sabouraud/Chloramphenicol Agar Plate was used to obtain the fungus culture. Fungus smears were performed, stained with lactophenol blue and analysed under optical microscope at different times.

Figure 1.

Horizontal (A) and vertical (B) cross-sections of the corneal infiltrate in anterior segment optical coherence tomography. Involvement of the entire corneal thickness, with epithelial defect and stromal thinning.

Treatment

After obtaining corneal cultures, fortified ceftazidime 50 mg/mL and tobramycin 1.64% (hourly) and intravenous ciprofloxacin 400 mg were started. No fungus was detected in the Sabouraud/Chloramphenicol Agar. The infiltrate turned more circumscribed and the hypopyon resolved.

Despite the apparent initial response to treatment, 1 week later she presented with a worsened infiltrate and hypopyon. Forty days after presentation, topical ceftazidime 50 mg/mL, tobramycin 1.64% (every hour), clotrimazole 10 mg/mL (four times a day), oxytetracycline 5 mg/g (three times a day) and intravenous ciprofloxacin 400 mg were initiated. A systemic evaluation for infectious and immunological markers was performed, including complete blood cell count, erythrocyte sedimentation rate, C reactive protein, rheumatoid factor, hepatitis B surface antigen, hepatitis B core antibody, hepatitis C virus antibody, HIV antigen and antibody and syphilis screening, which were all unremarkable. Protein chain reaction for Acanthamoeba, herpes simplex virus 1 and 2, varicella zoster virus and cytomegalovirus DNA was also negative.

The patient remained with this treatment for 1 week, with subsequent reduction of dosage to topical ceftazidime 50 mg/mL, tobramycin 1.64% (eight times a day), clotrimazole 10 mg/mL (four times a day), oxytetracycline 5 mg/g (three times a day) and oral ciprofloxacin 750 mg during 1 week. Since then, she was under topical ceftazidime 50 mg/mL and tobramycin 1.64% five times a day, clotrimazole 10 mg/mL four times a day and oxytetracyline two times a day.

Her clinical condition remained stable, with no signs of perforation, until the third month after presentation, when she presented with worsening of the stromal infiltrate, hypopyon and a central descemetocele. Due to the clinical worsening and to the risk of perforation, a tectonic PK was performed.

The immediate postoperative period was uneventful and the patient was treated with topical clotrimazole 10 mg/mL (four times a day), ofloxacin 3 mg/mL (six times a day), timolol 0.5% (two times a day), dexamethasone 1 mg/mL (six times a day) and oral cyclosporine 50 mg (two times a day). One week after the PK, her BCVA improved to 20/63 and at slit-lamp examination the graft was clear, there were posterior synechiae and a posterior subcapsular cataract. The treatment remained unchanged until 3 weeks after the PK, when ofloxacin 3 mg/mL and dexamethasone 1 mg/mL were reduced to four times a day. Two weeks later (6 weeks after the PK), she developed an endothelial infiltrate in the corneal graft associated with hypopyon, which was aspirated and analysed. According to our laboratory protocol, three samples were collected and cultured, using blood agar, chocolate agar and Sabouraud/Chloramphenicol Agar plates that were incubated at 37°C. Intracameral voriconazole was administrated. Postoperatively, she started topical cyclosporine 2%, voriconazole 1% and amphotericin B, all six times daily.

The colonies had a moderately/rapid growing and presented at first as white coloured and then became lilac, (figure 2A and B). Lactophenol smears were prepared and analysed under optical microscope at different times. The smears showed that conidiophores organised in verticillate branches with two to four phialides. The conidia originated from the phialides were round to fusiform, and presented a smooth to slightly roughened wall (figure 2C–E). Altogether, the macroscopic and microscopic characteristics allowed the identification as fungi from the genus Purpureocillium. In order to perform a more accurate identification of the species, it was performed the molecular analysis. Briefly, DNA from fungi culture was isolated, a segment of the internal transcribed spacer (ITS) and D1/D2 rDNA regions was amplified, the amplified products were sequenced by DNA Sanger sequencing, sequences were aligned to generate the consensus sequence that was then compared against sequences from the NCBI database. The combination of highest identity, total score and query values, identified the species as a P. lilacinum.

Figure 2.

(A, B) Sabouraud/Chloramphenicol Agar Plate, incubated at 37°C showing the colonies of P. lilacinus with 6 days (A) and 14 days (B) of culture. Colonies presented a white to lilac colour and a floccose aerial mycelium. (C–E) Conidiophores were organised in verticillate branches with two to four phialides. The conidia originated from the phialides were round to fusiform, and presented a smooth to slightly roughened wall. Magnification: 400x and 1000x.

Weekly intracameral voriconazole and intravenous voriconazole were added to the treatment. Despite this therapy, the clinical condition worsened, developing melting of the graft and an anterior chamber white mass (figure 3). Yet, the posterior segment remained without signs of involvement.

Figure 3.

Large corneal infiltrate, melting of the graft and hypopion.

Due to the lack of improvement, the patient underwent a second PK, 3 months after the first one. During the surgery, it was possible to observe iris infiltration by a whitish material. An anterior chamber washout with voriconazole was performed.

At the first postoperative day, oral posaconazole 400 mg two times daily was started. After 1 week of oral posaconazole, she reported symptomatic improvement, with increase of uncorrected visual acuity from hand motion at 2 feet to 20/200. Topical amphotericin was stopped, topical voriconazole (six times a day) and ofloxacin 3 mg/mL (five times a day) were continued for 6 months and 1 month, respectively.

Outcome and follow-up

Two months after starting posaconazole, there was no evidence of inflammation or fungal recurrence, the cornea remained clear and a dense posterior subcapsular cataract was observed (figure 4). The patient achieved a BCVA of 20/100. At this time, posaconazole was tapered off to 300 mg/day.

Figure 4.

Slit lamp image demonstrating clear corneal graft without signs of infection 2 months after starting oral posaconazole.

In order to diagnose potential adverse effects, she performed liver function monitoring two times a month, with no alterations registered.

Four months after initiating oral posaconazole, the treatment was stopped due to the increase of serum creatinine levels (1.40 mg/dL) and hypokalaemia (3.1 mmol/L). Currently, the patient remains without signs of recurrent infection (8 months after posaconazol cessation) and serum creatinine and potassium returned to normal levels.

Discussion

The visual outcome of P. lilacinus keratitis is usually poor, commonly culminating in endophthalmitis, perforation and enucleation.⁵ It usually occurs after environmental trauma.⁷ Keratitis induced by soft contact lens accounts for 24% of all Paecilomyces keratitis.¹⁴

The definitive diagnosis of Paecilomyces keratitis and the establishment of therapy is dependent of the fungus identification using microbiological techniques, and is often difficult and delayed. The success of the identification is dependent on the quality of the sample and on the microbiological procedures. It is crucial to collect the sample before the beginning the treatment.

One of the main reasons for the devastating course of the Paecilomyces keratitis is the antifungal resistance. In fact, P. lilacinus is resistant to amphotericin B. Nevertheless, previous studies showed that P. lilacinus is sensitive to the azoles namely to voriconazole and posaconazole. The azoles have lanosterol 14α-demethylase (CYP51) as primary target and block ergosterol synthesis. Ergosterol depletion coupled to the accumulation of methylated sterol precursors results in inhibition of fungal cell growth, fungal cell death or both.¹⁵

However, this patient was refractory to voriconazole and presented with recurrent fungal keratitis even after therapeutic corneal transplantation. Posaconazole differs from voriconazole in its extended side chain. The extended side chains of posaconazole provides additional points of contact with the azole target, CYP51.¹⁶ The addition of posaconazole marked the outset of an infection-free period, with no recurrence observed until today. To the best of our knowledge, there is only one report on the use of oral posaconazole for P. lilacinus keratitis. Although in that report the patient was submitted to a keratoprosthesis implantation 2 months after stopping oral posaconazole due to graft rejection, he remained with no evidence of infection after 3,5 years.¹³

Another triazole with in vitro activity is ravuconazole which could be a future option in the management of refractory cases.¹⁷

The most described adverse effects of posaconazole in the literature are gastrointestinal complaints, abnormal liver function tests and pleural effusion.^{13 18} Our patient manifested an increase of serum creatinine levels and hypokalaemia, which resolved after withdrawal of posaconazole. Despite the long period of treatment, she did not develop any irreversible complication. Concerning the use of oral posaconazole in a Paecilomyces keratitis, this is the first report describing adverse effects and the one in which the corneal graft remained longer without infection.

Learning points.

• Purpureocillium lilacinum (former Paecilomyces lilacinus) keratitis, although rare, often follows a relentless course, requiring aggressive medical therapy and surgical management.

• Experience in the treatment of keratitis due to P. lilacinus species is limited and the optimal antifungal treatment remains unknown.

• Although P. lilacinus keratitis is resistant to many antifungal agents, voriconazole has been found to be effective.

• Our patient revealed to be refractory to voriconazole, leading to the adoption of an alternative treatment with oral posaconazole, which proved to be effective and safe under close monitoring.

• To our best knowledge, this is the second case report that documents the effectiveness of oral posaconazole in a refractory P. lilacinus keratitis, resistant to other second-generation triazoles and conventional antifungals.