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.

Clinical and demographic study of microsporidial keratoconjunctivitis in South India: a 3-year study (2013-2015).

AIM: To study the demographic profile, clinical features, treatment outcome and ocular morbidity of smear-positive microsporidial keratoconjunctivitis. METHODS: Retrospective case series of all patients with clinical features of microsporidial keratoconjunctivitis and who were smear positive for the same on Gram stain from January 2013 to December 2015. Demographic data, predisposing factors, microbiological investigations, clinical course and visual outcome were analysed. RESULTS: Of the 10 655 patients with conjunctivitis, 550 (5.2%) patients were positive for microsporidia on Gram stain during this time period. The disease was prevalent throughout the year with an increased incidence from July to December. Bilateral involvement was seen in 27 (4.9%) patients. There was no predisposing risk factor in 428 (77.8%) patients. 384 (69.1%) patients had received prior treatment before presentation to us with the most common drug being antibiotic in 285 (49.4%) patients. All the patients underwent diagnostic corneal debridement and received topical 0.3% fluconazole eye drops four times a day. Of the 296 patients who followed-up, 187 (63.1%) patients had complete resolution without sequelae. 68 (22.9%) had persistent superficial punctate keratopathy, 30 (10.1%) developed subepithelial nummular keratitis. No significant change in visual acuity was seen in 255 (80.7%) eyes, two or more line improvement was seen in 48 (15.2%) eyes, while two or more line worsening was seen in 13 (4.1%) eyes. CONCLUSIONS: Microsporidial keratoconjunctivitis is prevalent in South India throughout the year. The characteristic clinical signs and simple microbiological investigation help us to differentiate it from adenoviral keratoconjunctivitis. The visual prognosis is good.

Microsporidial Stromal Keratitis: Clinical Features, Unique Diagnostic Criteria, and Treatment Outcomes in a Large Case Series.

PURPOSE: To describe the history, clinical features, and outcomes of a large case series of microsporidial stromal keratitis with emphasis on probable predictors of the etiology in this rare and unspecified form of keratitis. METHODS: Retrospective analysis of cases seen between January, 2002, and December, 2013, diagnosed at LV Prasad Eye Institute as having microsporidial stromal keratitis based on clinical, microbiology, and histopathology examination. Outcomes of medical and surgical management with visual recovery were documented. RESULTS: There were 34 cases of microsporidial stromal keratitis with a mean age of 43.3 years (range 2-77 years) and male preponderance. The duration of symptoms was chronic in most cases (mean duration of 288 days). Nearly half of the cases had a history of trauma, in the age group of 20 to 50 years. The most common clinical misdiagnosis was herpes simplex virus keratitis (26.5%) followed by fungal keratitis (17.6%). This could be attributed to the nonspecific clinical picture of diffuse multifocal stromal lesions in 82.4% of cases. The organisms were detected in microbiological evaluation of corneal scrapings in 47% cases, and histopathological detection of the organisms showed a positivity rate of 92.3%. Surgical management was necessary in the majority of the cases (73.5% of patients). CONCLUSIONS: The typical history of trauma with a smoldering, diffuse form of keratitis refractory to conventional medical therapy, responding to surgical removal for recovery is clearly demonstrated as a recurring feature in the majority of the cases. Patients presenting with this characteristic clinical picture should be suspected to harbor this rare pathogen, and early surgical interventions should be considered.

In vitro antimicrosporidial activity of gold nanoparticles against Heterosporis saurida.

BACKGROUND: Worldwide, there is a need to expand the number of drugs available to treat parasitic infections in aquaculture. One of the new materials being tested is metal nanoparticles, which have unique chemical and physical characteristics owing to their extremely small size and high surface area to volume ratio. We examined the effectiveness of gold nanoparticles against the microsporidian parasite Heterosporis saurida, which causes severe economic losses in lizard fish, Saurida undosquamis aquaculture. RESULTS: We synthesized gold nanoparticles by chemical reduction of tetrachloroauric acid as a metal precursor. We assessed the antimicrosporidial efficacy of the nanoparticles against H. saurida using an in vitro screening approach, which we had developed previously using the eel kidney cell line EK-1. The number of H. saurida spores produced in EK-1 cells was reduced in a proportional manner to the dosage of gold nanoparticles administered. A cell metabolic activity test (MTT) indicated that the gold nanoparticles did not appear to be toxic to the host cells. CONCLUSIONS: Gold nanoparticles can act as an effective antimicrosporidial agent and hold promise to reduce disease in lizardfish aquaculture. Metal nanoparticles should be considered as an alternate choice for development of new antimicrosporidial drugs to combat disease problems in aquaculture.

Clinical Features, Risk Factors, and Treatments of Microsporidial Epithelial Keratitis.

OBJECTIVE: To report the clinical manifestations, risk factors, and treatments of microsporidial epithelial keratitis in Thailand. METHODS: Twenty eyes of 19 patients were diagnosed and the clinical presentations, risk factors, and management were analyzed. RESULTS: Of 19 patients, six patients (32%) had no apparent risk factors. Predisposing factors included soil exposure (6/19, 32%), water contamination (6/19, 32%), and eye liner (1/19, 4%). Twelve cases (63%) were detected in the rainy season. All cases presented with disseminated, punctated, elevated, epithelial keratitis. Corneal scrapings with Gram-chromotrope staining were positive in all patients. Moxifloxacin 0.5% eye drops were given and all 16 patients experienced complete resolution. Three recurrent cases were resolved with only topical moxifloxacin without corneal scraping or swabbing. CONCLUSIONS: Predisposing factors were not found in some patients; thus, corneal scraping with staining should be considered in cases having a high index of suspicion. The incidence is increased during the rainy season; therefore, clinicians should have more awareness during these times. Debridement with topical moxifloxacin eye drops, without any systemic medication, may be an effective treatment. Corneal scraping or swabbing may not be required in recurrences.

Microsporidia infection of the cornea--a unique and challenging disease.

Microsporidia are a diverse group of obligate, intracellular, eukaryotic, spore-forming parasites. Traditionally, these were considered as protozoans but recently have been reclassified as fungi. Microsporidia behave as opportunistic pathogens causing systemic infections. In the eye, Microsporidia cause keratoconjunctivitis, corneal stromal keratitis, scleritis, and endophthalmitis. This review shares our experiences with anterior segment infections caused by this pathogen. Keratoconjunctivitis is a common form of ocular infection caused by the parasite. Although early reports described it as occurring only in immunosuppressed individuals, it can also occur in immunocompetent individuals. The disease shows a seasonal pattern with a peak incidence during the rainy season. Although several drugs have been considered, our experience suggests that keratoconjunctivitis is a self-limiting disease. In contrast to keratoconjunctivitis, stromal keratitis is an ill-defined disease. We collected 30 cases and analyzed the various aspects of this disease. Stromal keratitis is characterized by a slowly progressive course. The corneal picture resembles herpes simplex virus stromal keratitis or fungal keratitis cases, and is characterized by deep stromal infiltrates with overlying and surrounding stromal edema and keratic precipitates. The diagnosis of Microsporidia infection is confirmed by a microscopic examination of smears from patients with ulcerative keratitis or by a histopathological examination of corneal tissues. Definitive genus identification requires the examination of specimens by electron microscopy or by molecular methods. In the absence of a definitive medical treatment, nearly all patients require surgical treatment. The confusion regarding Microsporidia is not only limited to their classification but also extends to various aspects of the corneal disease caused by them.

Microsporidiasis.

Microsporidia are obligate intracellular spore-forming organisms. Several species of microsporidia cause human disease, mainly in immunocompromised hosts. The spectrum of disease varies from diarrhea, keratoconjunctivitis to disseminated infection involving multiple organs. CNS disease is a rare manifestation usually seen in compromised hosts as part of a disseminated infection. Only 12 cases of CNS microsporidiosis have been reported in the literature. Clinically, they usually present with signs and symptoms of encephalitis and seizures. Diagnosis often requires brain biopsy, but spores can occasionally be found in other sites. Albendazole and fumagillin have been successfully used in treating microsporidiosis at other sites, but their role in CNS infection is unclear.

Treatment of microsporidial keratoconjunctivitis with repeated corneal swabbing.

PURPOSE: To report the effect of repeated corneal swabbing in patients with microsporidial keratoconjunctivitis. DESIGN: Retrospective noncomparative case series. METHODS: Sixteen eyes of 14 healthy patients with microsporidial keratoconjunctivitis were diagnosed based on the detection of microsporidia in corneal scrapings using Gram stain, the modified Kinyoun acid-fast stain, or both. Polymerase chain reaction plus gene analysis of the microsporidian 16S ribosomal RNA had been performed in 10 patients who sought treatment between 2010 and 2011. Some of the lesions were scraped for procurement of specimens. The remaining lesions were wiped off gently by cotton swabs. Repeated swabbing was performed if infection persisted or new lesions were observed at follow-up. To prevent secondary bacterial infection, 0.3% norfloxacin or 0.25 % chloramphenicol were prescribed. RESULTS: The mean age was 52.2 years. All patients had the characteristic disseminated, punctate, slightly elevated, white epithelial lesions. The denser white lesions could be removed easily after gentle swabbing, and most epithelium remained intact. The 10 cases with positive polymerase chain reaction results were all identified to be Vittaforma corneae. The mean number of corneal swabbing was 3.3, and the mean disease resolution time was 6.6 days. No patients had recurrence or loss of visual acuity at last follow-up. CONCLUSIONS: Repeated swabbing effectively can eradicate corneal epithelial microsporidial lesions in approximately 1 week. It is easy to perform, less painful, and more acceptable for the patients.

Microsporidiosis: not just in AIDS patients.

PURPOSE OF REVIEW: Microsporidia have emerged as causes of opportunistic infections associated with diarrhea and wasting in AIDS patients. This review describes recent reports of microsporidiosis in HIV-infected individuals and the growing awareness of microsporidiosis in non-HIV-infected populations. RECENT FINDINGS: Microsporidia were only rarely recognized as causes of disease in humans until the AIDS pandemic. Implementation of combination antiretroviral therapy (cART) to curtail HIV replication and restore immune status drastically reduced the occurrence of opportunistic infections, including those due to microsporidia, in HIV-infected individuals. In developing countries where cART is not always accessible, microsporidiosis continues to be problematic. Improvement of diagnostic methods over the previous 25 years led to identification of several new species of microsporidia, many of which disseminate from enteric to systemic sites of infection and contribute to some unexpected lesions. Among non-HIV-infected but immune-suppressed individuals, microsporidia have infected organ transplant recipients, children, the elderly, and patients with malignant disease and diabetes. In otherwise healthy immune-competent HIV seronegative populations, self-limiting diarrhea occurred in travelers and as a result of a foodborne outbreak associated with contaminated cucumbers. Keratitis due to microsporidiosis has become problematic and a recent longitudinal evaluation demonstrated that non-HIV-infected individuals seropositive for microsporidia who had no clinical signs continued to intermittently shed organisms in feces and urine. SUMMARY: Greater awareness and implementation of better diagnostic methods are demonstrating that microsporidia contribute to a wide range of clinical syndromes in HIV-infected and non-HIV-infected people. As such, microsporidia should be considered in differential diagnoses if no other cause can be defined.

Microsporidial keratitis: need for increased awareness.

Since the devastation of the European silk worm industry in the 19th century, microsporidia have been recognized as important organisms. An enormous literature is available on their biology, phylogeny, classification, disease profile, diagnosis, and treatment; however, it is only recently that ophthalmologists have begun to take note of these organisms. The last two decades have seen several publications related to ocular microsporidiosis, in particular those forms affecting the cornea. Both immunocompetent and immunocompromised patients are at risk of developing corneal infections that may range from self limiting mild keratoconjunctivitis to severe stromal keratitis recalcitrant to medical treatment. Exposure to soil, muddy water, and minor trauma are possible risk factors. Although reliable prevalence data are lacking, recent studies indicate a high prevalence of microsporidial keratoconjunctivitis in the rainy season, especially in India and other countries with similar climates. For instance, a high prevalence has been documented in Singapore. We bring together the information available on ocular microsporidiosis.

Microsporidiosis: current status.

PURPOSE OF REVIEW: Microsporidiosis is an emerging and opportunistic infection associated with a wide range of clinical syndromes in humans. This review highlights the research on microsporidiosis in humans during the previous 2 years. RECENT FINDINGS: The reduced and compact microsporidian genome has generated much interest for better understanding the evolution of these parasites, and comparative molecular phylogenetic studies continue to support a relationship between the microsporidia and fungi. Through increased awareness and improved diagnostics, microsporidiosis has been identified in a broader range of human populations that, in addition to persons with HIV infection, includes travelers, children, organ transplant recipients, and the elderly. SUMMARY: Effective commercial therapies for Enterocytozoon bieneusi, the most common microsporidian species identified in humans, are still lacking, making the need to develop tissue culture and small animal models increasingly urgent. Environmental transport modeling and disinfection strategies are being addressed for improving water safety. Questions still exist about whether microsporidia infections remain persistent in asymptomatic immune-competent individuals, reactivate during conditions of immune compromise, or may be transmitted to others at risk, such as during pregnancy or through organ donation. Reliable serological diagnostic methods are needed to supplement polymerase chain reaction or histochemistry when spore shedding may be sporadic.

Keratitis caused by Trachipleistophora anthropopthera.

We report a case of intrastromal keratitis in a 42-year-old male with underlying human immunodeficiency virus-1 infection. Numerous microsporidial spores were found from corneal biopsy. Ultrastructural studies of corneal tissues revealed dimorphic sporophorous vesicles containing characteristic spores belonging to Trachipleistophora anthropopthera. Infection could be controlled by penetrating keratoplasty but not by topical fumagillin and systemic albendazole per se. This is the first report of human keratitis caused by this organism.

Chronic microsporidial stromal keratitis in an immunocompetent, non-contact lens wearer.

An 82-year-old healthy man with unilateral chronic stromal keratitis, initially diagnosed to have viral keratitis and refractory to medical therapy, showed numerous oval, microsporidial organisms, measuring 4-5 m in length in the corneal biopsy. Penetrating keratoplasty, followed by treatment with systemic albendazole and topical propamidine isethionate resulted in resolution of the infection. Electron microscopy of the keratoplasty specimen demonstrated sporoblasts with diplokaryotic nuclei and multiple coils of the filament. The light and electron microscopic features were consistent with microsporidial keratitis.

Treating opportunistic infections among HIV-exposed and infected children: recommendations from CDC, the National Institutes of Health, and the Infectious Diseases Society of America.

In 2001, CDC, the National Institutes of Health, and the Infectious Diseases Society of America convened a working group to develop guidelines for therapy of human immunodeficiency virus (HIV)-associated opportunistic infections to serve as a companion to the Guidelines for Prevention of Opportunistic Infections Among HIV-Infected Persons. In recognition of unique considerations related to HIV infection among infants, children, and adolescents, a separate pediatric working group was established. Because HIV-infected women coinfected with opportunistic pathogens might be more likely to transmit these infections to their infants than women without HIV infection, guidelines for treating opportunistic pathogens among children should consider treatment of congentially acquired infections among both HIV-exposed but uninfected children and those with HIV infection. In addition, the natural history of opportunistic infections among HIV-infected children might differ from that among adults. Compared with opportunistic infections among HIV-infected adults, which are often caused by reactivation of pathogens acquired before HIV infection when host immunity was intact, opportunistic infections among children often reflect primary acquisition of the pathogen and, among children with perinatal HIV infection, infection acquired after HIV infection has been established and begun to compromise an already immature immune system. Laboratory diagnosis of opportunistic infections can be more difficult with children. Finally, treatment recommendations should consider differences between adults and children in terms of drug pharmacokinetics, dosing, formulations, administration, and toxicities. This report focuses on treatment of opportunistic infections that are common in HIV-exposed and infected infants, children, and adolescents in the United States.

Evaluation of chronic diarrhea in patients with human immunodeficiency virus infection.

Chronic diarrhea is a common problem for patients with human immunodeficiency virus infection, especially those with advanced disease. The extent of evaluation and whether to do flexible sigmoidoscopy, colonoscopy, and/or upper endoscopy have been areas of significant debate. Based upon the marked improvement in long-term survival since the introduction of highly active antiretroviral therapy, a comprehensive evaluation is currently justified. A stepwise approach to the evaluation of chronic diarrhea appears to be the best approach. The first step is a history, with a focus on any association between the onset of diarrhea and the institution of protease inhibitor therapy, which is associated with significant diarrhea in many patients. If there is no temporal association with antiretroviral therapy, the next step is examination of stool for bacterial and protozoal pathogens. If the stool studies are negative, the next step is to proceed to colonoscopy. Flexible sigmoidoscopy alone has been noted to miss up to 39% of cases of cytomegalovirus colitis. The inclusion of ileoscopy and biopsy of the terminal ileum during colonoscopy has a significant yield for microsporidiosis, which may obviate the need for upper endoscopy. The highest yield can be expected in patients with fever, weight loss, and a CD4 count of under 200 cells/mm3, especially those with a CD4 count less than 50 cells/mm3.

Cryptosporidia and microsporidia--waterborne diseases in the immunocompromised host.

Cryptosporidia and microsporidia are emerging parasitic pathogens in immunocompetent and immunocompromised individuals. Cryptosporidium infects several wild and domestic animals that excrete oocysts into the environment and contaminated water represents the major source of infection for humans. Waterborne transmission of Cryptosporidium is a major risk for humans and appropriate measures have to be taken to protect immunocompetent and immunocompromised individuals to become infected. For microsporidia, the sources and ways of transmission are not well documented. Although several animal hosts have been identified recently, the relevant reservoirs of human microsporidia are still unknown. Also, the routes of spreading are unknown. Is microsporidiosis a zoonotic disease that will be transmitted through close contact with infected animals or is contaminated surface water responsible for transmission and represents a relevant reservoir? This review is designed to give information on these two emerging intestinal parasites in a format that will be useful to clinical microbiologists, physicians interested in infectious diseases, and public health personnel.

Molecular techniques for detection, species differentiation, and phylogenetic analysis of microsporidia.

Microsporidia are obligate intracellular protozoan parasites that infect a broad range of vertebrates and invertebrates. These parasites are now recognized as one of the most common pathogens in human immunodeficiency virus-infected patients. For most patients with infectious diseases, microbiological isolation and identification techniques offer the most rapid and specific determination of the etiologic agent. This is not a suitable procedure for microsporidia, which are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Although the diagnosis of microsporidiosis and identification of microsporidia by light microscopy have greatly improved during the last few years, species differentiation by these techniques is usually impossible and transmission electron microscopy may be necessary. Immunfluorescent-staining techniques have been developed for species differentiation of microsporidia, but the antibodies used in these procedures are available only at research laboratories at present. During the last 10 years, the detection of infectious disease agents has begun to include the use of nucleic acid-based technologies. Diagnosis of infection caused by parasitic organisms is the last field of clinical microbiology to incorporate these techniques and molecular techniques (e.g., PCR and hybridization assays) have recently been developed for the detection, species differentiation, and phylogenetic analysis of microsporidia. In this paper we review human microsporidial infections and describe and discuss these newly developed molecular techniques.

Clinical syndromes associated with microsporidiosis.

Microsporidia are ubiquitous in nature. Several clinical syndromes have been associated with microsporidiosis, especially in HIV-infected individuals, and include enteropathy, keratoconjunctivitis, sinusitis, tracheobronchitis, encephalitis, interstitial nephritis, hepatitis, cholecystitis, osteomyelitis, and myositis. Diarrhea and malabsorption are the most common clinical problems. Enterocytozoon bieneusi is the most common microsporidial cause of intestinal disease. A second species, Encephalitozoon intestinalis (originally named Septata intestinalis) is associated with disseminated as well as intestinal disease. Microsporidiosis has been seen worldwide, and is recognized as a frequent enteric infection in patients with AIDS. The pathogenesis of intestinal disease is related to excess death of enterocytes as a result of cellular infection. Clinically, microsporidiosis most often presents with diarrhea and weight loss as a result of small intestinal injury and malabsorption. However, microsporidia have been detected in virtually all organs, and may provoke symptoms related to their specific localization. The diagnosis of microsporidiosis is made histologically, either from tissue biopsies or secretions. While transmission electron microscopy was required for diagnosis in the past, special stains and light microscopy, as well as immunohistochemical and molecular techniques are capable of providing a firm diagnosis. Therapeutic options are limited. Enc. intestinalis responds well to albendazole, while no antiparasitic therapy has documented efficacy in Ent. bieneusi infections.