Microsporidial stromal keratitis and endophthalmitis in an immunocompetent patient

Case Report: The Use of In Vivo Confocal Microscopy for Diagnosis and Monitoring in a Rare Case of Ancaliia algerae Microsporidial Keratitis in New South Wales, Australia

We describe the successful management of Ancaliia Algerae microsporidial keratitis in an immunosuppressed 54-year-old woman with refractory linear IgA disease. The case highlights the challenges in diagnosis and management of this infection in immunocompromised individuals and emphasizes the usefulness of in vivo confocal microscopy as a novel, noninvasive tool to aid in the diagnosis and monitoring of microsporidial keratitis. We also discuss the possible mode of acquisition of this rare infection.

Microsporidial Stromal Keratitis: Epidemiological Features, Slit-Lamp Biomicroscopic Characteristics, and Therapy

PURPOSE

Microsporidial stromal keratitis is a rare form of infectious keratitis, with only 7 cases reported in the United States to date. This study was performed to evaluate risk factors, clinical features, and response to therapy.

METHODS

A retrospective review of the medical records of all patients diagnosed with microsporidial stromal keratitis seen in the practices of the authors between 1999 and 2020 was performed. Diagnosis was determined by cytology or histopathology in corneal specimens. Risk factors, presence or absence of distinctive clinical features, and response to medical and surgical therapies were recorded.

RESULTS

Nine patients-7M:2F, aged 7 to 99 years-with microsporidial stromal keratitis were identified. Exposures to recreational water and hymenopteran insect bites, both epidemiologically linked risk factors for systemic microsporidial infection, were identified in our patients. Presence of stromal edema with features of disciform keratitis and a distinctive granular keratitis were observed in 6 of 9 and 5 of 9 patients, respectively. Poor response to medical therapy was noted. Penetrating keratoplasty was effective in curing the infection. Final visual acuity was 20/40 or better in 6 of 9 patients.

CONCLUSIONS

In patients with slowly progressive keratitis, history of exposure to recreational water or hymenopteran insects should be sought. In patients with corneal edema consistent with disciform keratitis, with evolution to a granular keratitis, microsporidia should be considered in the differential diagnosis. In cases of established microsporidial stromal keratitis, penetrating keratoplasty should be considered if prompt response to medical therapy is not noted.

Microsporidiosis in Humans

Microsporidia are obligate intracellular pathogens identified ∼150 years ago as the cause of pébrine, an economically important infection in silkworms. There are about 220 genera and 1,700 species of microsporidia, which are classified based on their ultrastructural features, developmental cycle, host-parasite relationship, and molecular analysis. Phylogenetic analysis suggests that microsporidia are related to the fungi, being grouped with the Cryptomycota as a basal branch or sister group to the fungi. Microsporidia can be transmitted by food and water and are likely zoonotic, as they parasitize a wide range of invertebrate and vertebrate hosts. Infection in humans occurs in both immunocompetent and immunodeficient hosts, e.g., in patients with organ transplantation, patients with advanced human immunodeficiency virus (HIV) infection, and patients receiving immune modulatory therapy such as anti-tumor necrosis factor alpha antibody. Clusters of infections due to latent infection in transplanted organs have also been demonstrated. Gastrointestinal infection is the most common manifestation; however, microsporidia can infect virtually any organ system, and infection has resulted in keratitis, myositis, cholecystitis, sinusitis, and encephalitis. Both albendazole and fumagillin have efficacy for the treatment of various species of microsporidia; however, albendazole has limited efficacy for the treatment of Enterocytozoon bieneusi. In addition, immune restoration can lead to resolution of infection. While the prevalence rate of microsporidiosis in patients with AIDS has fallen in the United States, due to the widespread use of combination antiretroviral therapy (cART), infection continues to occur throughout the world and is still seen in the United States in the setting of cART if a low CD4 count persists.

A Narrative Review of Microsporidial Infections of the Cornea

Microsporidia are a rare and commonly misdiagnosed cause of corneal infection, accounting for approximately 0.4% of cases of microbial keratitis in some populations. Ocular microsporidiosis most often presents as either microsporidial keratoconjunctivitis (MKC) or microsporidial stromal keratitis (MSK). Though these two clinical entities exhibit similar symptomology, they are distinguished from one another by the time course for disease progression, findings on slit-lamp examination, and response to medical therapy. This review summarizes the current literature on the etiology and clinical presentation of microsporidial infections of the cornea and highlights ongoing developments in available diagnostic modalities and treatment regimens.

Microbial Keratitis in Taiwan: A 20-Year Update

PURPOSE

To investigate the demographics, risk factors, microbiology, and resistance pattern at a tertiary hospital and to detect the shifting trend over 2 decades.

DESIGN

A retrospective observational case series.

METHODS

We reviewed all records of patients with microbial keratitis (MK) that were hospitalized in National Taiwan University Hospital between 2007 and 2016. Demographics, predisposing factors, pathogens, and clinical courses were compared to our previous study conducted from 1992 to 2001. Antibiotic susceptibility was compared with those conducted from 1994 to 2005.

RESULTS

The percentage of patients 60 years and older in the MK population was increasing (P = 2.1E-21). The proportion of trauma-related MK declined while MK related to chronic ocular or systemic disorders rose. The prevalence of nontuberculous mycobacteria (NTM) showed a decreasing trend (P = .0032), whereas Microsporidia has been increasingly detected. The 2 most common bacterial isolates were Pseudomonas aeruginosa (35.2%) and Staphylococcus species (13.2%). Management of these infection did not differ in common pathogens between the 2 decades. The susceptibility of Staphylococcus species to oxacillin reduced significantly (P = .002) and there was an increase in methicillin-resistant Staphylococcus aureus keratitis.

CONCLUSIONS

Contact lens wear remained the most common predisposing factor, with Pseudomonas species as the major pathogen. However, chronic disorder-related MK was on the rise along with an increasing trend of oxacillin resistance in Staphylococcus species. We found a decreasing trend in NTM keratitis while Microsporidia keratitis was considered as an emerging ocular disease. Though gram-negative isolates remained susceptible to all antibiotics tested, antibiotic resistance was more common in gram-positive isolates.

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.

Practical Guidance for Clinical Microbiology Laboratories: Laboratory Diagnosis of Parasites from the Gastrointestinal Tract

This Practical Guidance for Clinical Microbiology document on the laboratory diagnosis of parasites from the gastrointestinal tract provides practical information for the recovery and identification of relevant human parasites. The document is based on a comprehensive literature review and expert consensus on relevant diagnostic methods. However, it does not include didactic information on human parasite life cycles, organism morphology, clinical disease, pathogenesis, treatment, or epidemiology and prevention. As greater emphasis is placed on neglected tropical diseases, it becomes highly probable that patients with gastrointestinal parasitic infections will become more widely recognized in areas where parasites are endemic and not endemic. Generally, these methods are nonautomated and require extensive bench experience for accurate performance and interpretation.