Trachipleistophora hominis: molecular characterization of a rare pathogen causing microsporidial stromal keratitis.

The authors report the clinical and microbiological findings of a unique case of stromal keratitis caused by a rare microsporidium, Trachipleistophora hominis. This case of stromal keratitis was in a 49-year-old male with a history of COVID-19 infection and diabetes mellitus. Corneal scraping specimens revealed numerous microsporidia spores upon microscopic examination. PCR of the corneal button revealed the presence of T. hominis infection, which could be controlled by penetrating keratoplasty surgery. The graft was clear with no recurrence of infection until the last follow-up 6 weeks postsurgery. This is the first case of human stromal keratitis caused by this organism in a post-COVID infection, confirmed by molecular diagnosis.

Chlorhexidine in the treatment of microsporidial stromal keratitis and the effect of host immunity: A case series and literature review.

Microsporidial stromal keratitis is an increasingly well-known vision-threatening disease. A large proportion of cases are initially misdiagnosed as herpes simplex keratitis and treated with topical steroids. In most of such cases, medical treatment failed, and corneal transplantation was required. This study reported the results of 0.02% topical chlorhexidine used to treat three cases of microsporidial stromal keratitis and reviewed the literature on the outcomes of microsporidial stromal keratitis treatment. In the first case, histopathology of a specimen from penetrating keratoplasty (PK) revealed severe chronic inflammation involving the entire stromal layer but no microorganism activity after the application of topical chlorhexidine for 10 months. The second case exhibited complete resolution of keratitis after topical chlorhexidine. The patient in the third case did not respond to medical treatment, and therapeutic PK was performed. Histopathological examination revealed numerous microsporidial spores that had colonized in the mid and deep stroma, where few inflammatory cells were observed. These findings explain the variable microsporidial susceptibility to chlorhexidine, suggesting the crucial role of host immunity. In cases of host immunity, topical chlorhexidine may represent a promising option for the treatment of microsporidial stromal keratitis.

Microsporidial stromal keratitis: characterisation of clinical features, ultrastructural study by electron microscopy and efficacy of different surgical modalities.

AIMS: To report the clinical manifestations, ultrastructure and evaluate the efficacy of therapeutic lamellar keratectomy (TLK) and penetrating keratoplasty (PK) for microsporidial stromal keratitis (MSK). METHODS: Fourteen MSK cases between 2009 and 2018 were recruited. Each patient's clinical presentation, light microscopy, histopathology, PCR and electron microscopy (EM) of corneal samples were reviewed. RESULTS: The patients were 70.0±4.7 years old (average follow-up, 4.5 years). Time from symptoms to presentation was 10.6±13.0 weeks. The corneal manifestations were highly variable. Corneal scrapings revealed Gram stain positivity in 12 cases (85.7%) and modified Ziehl-Neelsen stain positivity in 9 (64.3%). Histopathology revealed spores in all specimens, while sequencing of small subunit rRNA-based PCR products identified Vittaforma corneae in 82% of patients. EM demonstrated various forms of microsporidial sporoplasm in corneal keratocytes. All patients were treated with topical antimicrobial agents or combined with oral antiparasitic medications for >3 weeks. As all patients were refractory to medical therapy, they ultimately underwent surgical intervention (TLK in 7, PK in 6 and 1 received TLK first, followed by PK). Postoperatively, the infection was resolved in 78.6% of the patients. Nevertheless, a high recurrence rate (21.4%) was noted during 3-year follow-up, with only two patients retained a final visual acuity ≥20/100. CONCLUSION: MSK usually presents with a non-specific corneal infiltration refractory to antimicrobial therapy. The diagnosis relies on light microscopic examinations on corneal scrapings and histopathological analyses. Surgical intervention is warranted by limiting the infection; however, it was associated with an overall poor outcome.

Case Report: Ocular Microsporidiosis: Case in a Patient Returning from India and Review of the Literature.

Microsporidia are protists close to the kingdom of fungi that may cause eye infections. Most cases are reported in Asia and affect both immunocompromised and immunocompetent patients. Here, we report a rare case of microsporidial keratoconjunctivitis in an immunocompetent French patient 3 weeks after returning from India. In our patient, Weber trichrome staining of conjunctival scrapings revealed rounded elements approximately 1-3 µm in size. Conventional polymerase chain reaction analysis by ribosomal RNA subunit sequencing showed 100% identity with Vittaforma corneae. Treatment by corneal debridement combined with fluoroquinolone eye drops allowed complete resolution of the lesions. Although rare, ocular microsporidiosis should be investigated in a patient who is native to Asia or has returned from an endemic area and presents with keratoconjunctivitis of undetermined etiology.

Femtosecond laser-assisted anterior lamellar keratoplasty in stromal keratitis caused by an Endoreticulatus-like microsporidia.

PURPOSE: To describe a case of stromal keratitis caused by an Endoreticulatus-like microsporidia satisfactorily treated with femtosecond-assisted anterior lamellar keratoplasty (femto-ALK). METHODS: Case report. RESULTS: A 65-year-old healthy woman had a 10-month history of foreign body sensation and blurred vision after a flying insect struck her right eye. The patient presented with focal central to paracentral anterior stromal infiltration and edema with keratic precipitates of the right cornea. Confocal microscopy showed enhanced keratocytes with intracellular hyperreflective round and ovoid bodies confined to the anterior two thirds of corneal stroma. Femto-ALK was performed for excisional biopsy and replacement with anterior stromal donor cornea. A modified trichrome stain of corneal tissue showed numerous microsporidial spores whose small subunit rRNA sequence belonged to that of an Endoreticulatus-like microsporidia. CONCLUSIONS: Besides systemic infection, Endoreticulatus-like microsporidia can cause stromal keratitis. With careful patient selection, femto-ALK may be considered a new surgical alternative with satisfactory treatment outcomes.

The efficacy of corneal debridement in the treatment of microsporidial keratoconjunctivitis: a prospective randomized clinical trial.

PURPOSE: To evaluate the efficacy of corneal debridement in the treatment of clinically diagnosed cases of microsporidial keratoconjunctivitis. DESIGN: Prospective, double-masked randomized clinical trial. METHODS: Patients with clinical features such as multifocal, coarse, raised, punctate, round to oval epithelial lesions in the cornea in slit-lamp examination with mild to moderate conjunctival congestion, suggestive of microsporidial superficial keratoconjunctivitis, were included in the prospective study. All patients were randomized into 2 groups. Group 1 patients underwent debridement with the help of a sterile #15 blade on a Bard-Parker handle, whereas only conjunctival swabs were taken from Group 2 patients. All patients were treated with ocular lubricants. RESULTS: One hundred and twenty patients with clinical features suggestive of microsporidial superficial keratoconjunctivitis were included in the study. The mean age was 34.3 ± 13.6 years (Group 1) and 35.8 ± 16.2 years (Group 2) (P = .59). The mean duration of symptoms was 6.8 ± 3.9 days (Group 1) and 7.2 ± 4.6 days (Group 2) (P = .61). Baseline characteristics showed no difference between the 2 groups. The primary outcome was the time from the presentation to complete resolution (ie, absence of corneal lesions) of the clinical signs and symptoms. The secondary outcomes were final visual acuity and residual corneal side effects and/or scarring, if any. The mean resolution time of the corneal lesions was 5.7 ± 4.0 days (Group 1) and 5.9 ± 3.9 days (Group 2) (P = .83). There was no significant difference in final visual outcome in the 2 groups. No serious side effects were observed. CONCLUSION: Debridement does not have any significant advantage in terms of resolution of the corneal lesions and final visual outcome in cases of microsporidial keratoconjunctivitis.

Microsporidial spores can cross the intact Descemet membrane in deep stromal infection.

We report a rare case of a deep stromal keratitis with a chronic indolent course, diagnosed as microsporidial keratitis from corneal scrapings. The patient's condition worsened despite medical therapy and penetrating keratoplasty was performed. The histopathology of the corneal tissue revealed multiple microsporidial spores in the posterior stroma and the endothelial exudates, whereas there was no clinical or histopathological breach in Descemet's membrane. This is the second report in the literature to report that micropsoridial spores can cross the intact Descemet's membrane.

Deep anterior lamellar keratoplasty to treat microsporidial stromal keratitis.

PURPOSE: To describe deep anterior lamellar keratoplasty (DALK) as a surgical option to treat a case of severe microsporidial stromal keratitis in an immunocompetent patient. MATERIALS AND METHODS: This study is a descriptive case report. A 42 year-old Pakistani woman had an 8-year history of symptoms in the left eye. She had been previously provisionally diagnosed as suspected herpes simplex keratitis or Thygeson keratitis. At presentation, her best-corrected visual acuity was 20/20 OD and 20/200 OS. Examination of the left cornea revealed irregular, central, deep stromal opacification with keratitic precipitates and occasional cells in the anterior chamber. Investigations for mycobacteria, syphilis, and a tetraplex test were normal; all other hematological/biochemistry/virology investigations were normal-she was not found to be immunocompromised. RESULTS: A corneal biopsy confirmed microsporidial infiltration of the stroma. After intensive medical treatment with topical fumagillin and oral albendazole without resolution, DALK was performed with total stromal replacement using the big-bubble technique. One year postoperatively, the graft remained clear with no evidence of recurrence and best-corrected visual acuity was 20/40 OS. CONCLUSIONS: Microsporidial stromal keratitis is rare. Conventional surgical treatment for such a condition has been penetrating keratoplasty. DALK may be considered an option for visual rehabilitation in these cases.