Aspergillus fumigatus corneal abscess following ocular trauma: a case report

¹Laboratory of Microbiology, Mohammed VI University Hospital Center, Oujda, Morocco, ²Microbiology Unit, Faculty of Medicine and Pharmacy, Oujda, Morocco, ³Department of Ophthalmology, Mohammed VI University Hospital Center, Oujda, Morocco, ⁴Department of Bacteriology, Mohammed V Military Hospital, Rabat, Morocco

^&Corresponding author
Kaoutar Jamal, Laboratory of Microbiology, Mohammed VI University Hospital, Oujda, Morocco

Introduction    

Aspergillus fumigatus corneal abscess is a grave fungal infection of the cornea, with the potential to cause blindness and pose a significant treatment challenge. Rapid and specialized intervention is imperative for effective management. Globally, fungal keratitis due to filamentous fungi predominates in tropical, hot, and humid climates, while yeast infections are more common in temperate regions [1]. Trauma with a foreign body, particularly those of plant origin, constitutes the main risk factor for fungal abscess on a healthy cornea [2]. We report here a case of a corneal abscess caused by A. fumigatus, which was diagnosed two weeks after ocular trauma resulting from contact with a tree branch.

Patient and observation     

Patient information: we report a case study of a 55-year-old female patient residing in a rural area, without any particular pathological history. She was admitted to the emergency room on the first day, reporting a 15-day history for decreased visual acuity in her left eye, along with severe pain and the sudden onset of eye redness.

Clinical finding: the ophthalmological examination of the left eye (day 1) showed finger movement as the only visual acuity, along with conjunctival hyperemia, ectropion, and a corneal abscess measuring 6 mm which was highlighted by fluorescein and accompanied by hypopyon in the anterior chamber (Figure 1). The rest of the examination showed normal findings.

Timeline of the current episode: before the appearance of these clinical symptoms, the patient had suffered minor trauma to her left eye caused by contact with a tree branch. Two days after exposure to the event, the patient presented tearing and mild ocular itching in the affected eye. Two days after the incident, the patient presented tearing and mild ocular itching in the affected eye.

Diagnostic assessment: the patient underwent a corneal scraping of the left eye. A sample from the scraping was placed on a dry swab and sent to the microbiology laboratory for analysis. Direct examination did not initially reveal any microorganisms. Subsequently, a culture of the sample on chocolate agar medium was carried out. After 24 hours of incubation at 37°C, the culture revealed the growth of white, powdery colonies on the Petri dishes, with a change to bluish green, then turning dark green. A subculture of the colonies was then performed onto Sabouraud chloramphenicol medium, with and without actidione. After 24 hours of incubation at 27°C, similar colony growth was observed. Microscopic examination of the colonies showed a typical appearance of Aspergillus fumigatus after staining with lactophenol blue (round spores originating from phialides surrounding the club-shaped vesicle extending the conidiospores) (Figure 2).

Therapeutic intervention: while awaiting laboratory results, the patient was prescribed fortified eye drops containing hexamidine diisethionate, to be administered as one drop 8 times a day. Additionally, injectable imipenem was prescribed at a dosage of 500 mg 3 times a day, along with oral valaciclovir at a dosage of 1000 mg 3 times a day. Following the diagnosis of Aspergillus fumigatus, the patient was started on fortified fluconazole eye drops at a rate of one drop 4 times a day, mannitol 10% infusion at a rate of 500 ml per day, and oral acetazolamide at a dosage of 250 mg 3 times a day.

Follow-up and outcome of interventions: after 10 days of treatment, the evolution was unfavorable marked by the establishment of a total corneal abscess, peripheral stromal necrosis, with descemetocele. On day 17, the patient underwent conjunctival coverage of the cornea. Subsequently, a post-operative local treatment was started based on ciprofloxacin ointment applied 2 times per day, dexamethasone ointment applied 1 time per day, along with autologous serum and eye wash 4 times per day. While there was a reduction in pain and ocular redness, unfortunately, there was no perceptible improvement in visual acuity.

Patient perspective: at first, I was optimistic after starting treatment to preserve the vision in my left eye. However, I was informed that the prognosis was unfavorable in my case, as I arrived late for the consultation. Afterwards, I understood the situation, and I'm trying to adapt, especially as I still have another functional eye.

Informed consent: informed consent was obtained from the patient.

Discussion     

Aspergillus fumigatus is a hyaline, septate, haploid filamentous fungus. It is part of the phylogenetic group Ascomycetes, within the order Eurotiales and the family Trichocomaceae or Aspergilaceae. A. fumigatus is widely distributed throughout the world, with prevalence notably observed in late summer, autumn and winter periods, and is an environmental saprophyte [3]. A. fumigatus possesses several pathogenicity factors, including its small spore size, thermo-tolerance and possession of virulence factors [3].

A. fumigatus keratitis on a healthy cornea most often develops following corneal trauma involving a plant or soil-related foreign body. This occurrence elucidates the high frequency of fungal keratitis in people working in ground-related activities, such as agriculture and construction, while Candida species are frequently associated with ocular surface diseases such as sicca, and topical steroid use [1,2]. Corneal refractive surgeries, such as laser in situ keratomileusis (LASIK), can also, albeit rarely, lead to A. fumigatus keratitis [1]. Fungal attack on the cornea typically begins with the formation of a mycelial filament. Initially, the corneal lesion is characterized by epithelial damage, progressing into a corneal abscess reaching the stroma [1]. These mycelial filaments cross the corneal stroma, proliferate and cross Descemet's membrane, eventually colonizing the anterior chamber, leading to the formation of a hypopyon. Ulceration and stromal necrosis are mainly complicated by descemetocele, endophthalmitis, or even corneal perforation [1].

Clinical manifestations of keratomycosis may appear within a few days or be delayed by a few weeks [1]. Compared to bacterial keratitis, the symptoms of fungal keratitis are often less [4]. This may explain why patients arriving late at clinics, often presenting with an advanced fungal corneal ulcer, as in our case. The poor prognostic factors identified are a larger infiltrate, a substantial epithelial defect, the presence of hypopyon and positive smear even after prior antifungal treatment [1]. Distinguishing fungal keratitis from bacterial keratitis based solely on clinical presentation is often insufficient [4]. Corneal scraping is the reference sample [1]. Therapeutic decisions for initiation of antifungal therapy can be reliably based on direct microscopic examination of corneal scrapings [1].

Various antifungals have been evaluated in the treatment of fungal keratitis. Among them, topical natamycin remains the treatment of choice for filamentous fungal keratitis. Previous studies have reported that the majority of Aspergillus spp. isolated from cases of keratitis were sensitive to natamycin [5]. Several studies have investigated the comparison between alternative treatment strategies and the standard treatments, but none have yet proven superiority. Additional topical antifungals used in the treatment of fungal keratitis include amphotericin B 0.15-0.3%, voriconazole 1%, econazole 1%, itraconazole 1%, and miconazole 1%. They have been used as supplements or alternatives to natamycin. They can be administered by different routes [2]. Voriconazole has been reported as an effective triazole antifungal against fluconazole-resistant strains in fungal keratitis. It is well tolerated and exhibit good intraocular diffusion [6]. It can be used in the form of 1% eye drops prepared in hospital pharmacies or orally. Marangon et al. [7] report increased susceptibility of Aspergillus, Fusarium, and Candida to voriconazole.

In case of treatment failure or resistance, the combination of general antifungal treatment has shown its effectiveness. Our patient did not benefit from treatment with natamycin, which is unavailable in Morocco, but she received fluconazole prepared by the hospital pharmacy. There is no international consensus regarding the specific molecule or combination of molecules to use [1]. Bourcier et al. [8] recommend treating early-stage superficial fungal keratitis with a local antifungal; either amphotericin B or voriconazole. For deeper stromal damage, a combination of local and general antifungal agents is suggested, with voriconazole serving as the primary systemic antifungal. New drug delivery systems and devices have been investigated for better corneal penetration and release, such as vesicular systems based on liposomes or niosomes, contact lenses, and drug-loaded microneedle eye patches. In addition, new promoting therapeutic agents and methods have been applied, such as antimicrobial peptides, n-butyl cyanoarcylate, umbilical cord mesenchymal stem cells, terbinafine, eugenol, dimethyl itaconate, inhibitors matrix metalloproteinases, inotrophoresis, and photodynamic antimicrobial chemotherapy [9].

In cases of medical treatment failure, surgical interventions such as conjunctival coverage or lamellar/transfixing keratoplasty may be considered. Our patient underwent conjunctival coverage due to the lack of response to medical treatment. The prognosis of fungal keratitis will depend on how early the diagnosis is made and how quickly an effective antifungal agent is started. The prognosis of fungal keratitis depends on the timeliness of diagnosis and the rapid implementation of effective antifungal treatment. The visual prognosis for our patient was devastating, due to the delayed diagnosis. The patient had previously received antibiotic treatment, often ineffective when combined with corticosteroid therapy, especially considering the limited therapeutic resources available.

Conclusion     

Fungal keratitis remains among the most difficult forms of infectious keratitis to manage. Upon suspicion of diagnosis, a corneal scraping for microbiological examination is desirable before starting antifungal medical treatment as quickly as possible. The prognosis for fungal keratitis continues to be unfavorable. This is due to both the high virulence of the involved fungus, and the limited intracorneal diffusion of conventional antifungal drugs.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Patient management: Rachid Sekhesoukh, Adil Maleb and Kaoutar Jamal. Data collection: Kaoutar Jamal and Said Ezrari. Manuscript drafting: Kaoutar Jamal and Said Ezrari. Manuscript revision: Abderrazak Saddari, Rachid Sekhesoukh, Elmostafa Benaissa, Yassine Ben Lahlou, Mostafa Elouennass and Adil Maleb. All authors approved the final version of the manuscript.

Acknowledgement     

We thank the nurses and doctors who were part of the managing team of this patient.

Figures     

Figure 1: corneal abscess of the left eye

Figure 2: appearance of Aspergillus fumigatus after staining with lactophenol blue

References