Chlorhexidine Monotherapy with Adjunctive Topical Corticosteroids for Acanthamoeba Keratitis

Comparing cytotoxicity and efficacy of miltefosine and standard antimicrobial agents against Acanthamoeba trophozoites and cyst forms: An in vitro study

Acanthamoeba keratitis (AK) is an eye disease often occurring in contact lens wearers. AK treatment is prolonged and requires multiple drugs, which can lead to adverse effects. Our study aimed to compare the in vitro activities and safety of Miltefosine with that of conventional antimicrobial agents used to treat AK. Acanthamoeba castellanii genotype T4 was obtained from a patient with keratitis and subjected to in vitro susceptibility testing with various antimicrobial agents, including Chlorhexidine (CHX), Pentamidine isethionate (PI)Polyhexamethylene biguanide (PHMB), and Miltefosine to assess their efficacy against Acanthamoeba trophozoites and cyst. The cytotoxicity of the agents was evaluated in Vero cells, and their selectivity indexes (SI) were calculated. Chlorhexidine exhibited the highest amoebicidal activity with the highest selectivity index against the trophozoite and cyst, ranging from 1.17 to 8.35. The selectivity index of PHMB is slightly comparable to Chlorhexidine, exhibiting significant anti-Acanthamoeba activity. On the other hand, Pentamidine isethionate and Miltefosine displayed low SI among the compounds. Pentamidine isethionate was effective at high concentrations, which was toxic. Miltefosine exhibited the lowest cytotoxicity; nevertheless, due to the lowest anti-Acanthamoeba activity presented a low selectivity against the parasite. Further studies on more clinical samples and prolonged incubation time should be done to investigate the effectiveness and toxicity of drugs in both in vitro and in vivo conditions.

Use of Amniotic Membrane Transplant and Deep Anterior Keratoplasty in a Patient with Bilateral Acanthamoeba Infectious Keratitis: A Case Report

The aim of this study was to report a case with the use of amniotic membrane transplant and deep anterior keratoplasty in a patient with bilateral Acanthamoeba infectious keratitis as a treatment. A 20-year-old male presented with bilateral Acanthamoeba keratitis (AK) who was initially diagnosed with herpetic keratitis receiving full antiviral and corticosteroid topical treatment without any improvement. Corneal biopsy was performed to confirm the suspected diagnosis, and Acanthamoeba stromal cysts were identified in the sample. Treatment was initiated with 0.02% chlorhexidine, 0.1% propamidine isethionate, neomycin, and tropicamide/phenylephrine. Symptoms and clinical improvement were achieved between the 8th and 10th weeks, so corticosteroids were initiated. Treatment was continued until we observed a poor response in the left eye; therefore, an epithelial scraping and amniotic membrane placement were performed. Lately, the right eye underwent a deep anterior lamellar keratoplasty. A challenging case of bilateral AK managed with topical medications, amniotic membrane, and corneal keratoplasty. The earlier the disease is diagnosed, the better the outcome. If the diagnosis is delayed, the amoebas have penetrated deep into the corneal stroma, and successful therapy becomes difficult. A surgical option can be an early solution with a good prognosis for these cases.

Topical Chlorhexidine 0.2% versus Topical Natamycin 5% for the Treatment of Fungal Keratitis in Nepal: A Randomized Controlled Noninferiority Trial

PURPOSE

To investigate if topical chlorhexidine 0.2%, which is low cost and easy to formulate, is noninferior to topical natamycin 5% for the treatment of filamentous fungal keratitis.

DESIGN

Randomized controlled, single-masked, noninferiority clinical trial.

PARTICIPANTS

Adults attending a tertiary-level ophthalmic hospital in Nepal with filamentous fungal infection confirmed on smear or confocal microscopy.

METHODS

Participants were randomly allocated to receive topical chlorhexidine 0.2% or topical natamycin 5%. Primary analysis (intention-to-treat) was by linear regression, using baseline logarithm of the minimum angle of resolution (logMAR) best spectacle-corrected visual acuity (BSCVA) and treatment arm as prespecified covariates. Mixed fungal-bacterial infections were excluded from the primary analysis but included in secondary analyses and secondary safety-related outcomes. The noninferiority margin was 0.15 logMAR. This trial was registered with ISRCTN, number ISRCTN14332621.

MAIN OUTCOME MEASURES

The primary outcome measure was BSCVA at 3 months. Secondary outcome measures included perforation or therapeutic penetrating keratoplasty by 90 days.

RESULTS

Between June 3, 2019, and November 9, 2020, 354 eligible participants were enrolled and randomly assigned: 178 to chlorhexidine and 176 to natamycin. Primary outcome data were available for 153 and 151 of the chlorhexidine and natamycin groups, respectively. Of these, mixed bacterial-fungal infections were found in 20 cases (12/153 chlorhexidine, 8/151 natamycin) and excluded from the primary analysis. Therefore, 284 patients were assessed for the primary outcome (141 chlorhexidine, 143 natamycin). We did not find evidence to suggest chlorhexidine was noninferior to natamycin and in fact found strong evidence to suggest that natamycin-treated participants had significantly better 3-month BSCVA than chlorhexidine-treated participants, after adjusting for baseline BSCVA (regression coefficient, -0.30; 95% confidence interval [CI], -0.42 to -0.18; P < 0.001). There were more perforations and emergency corneal grafts in the chlorhexidine arm (24/175, 13.7%) than in the natamycin arm (10/173, 5.8%; P = 0.018, mixed infections included), whereas natamycin-treated cases were less likely to perforate or require an emergency corneal graft, after adjusting for baseline ulcer depth (odds ratio, 0.34; 95% CI, 0.15-0.79; P = 0.013).

CONCLUSIONS

Treatment with natamycin is associated with significantly better visual acuity, with fewer adverse events, compared with treatment with chlorhexidine. Natamycin remains the preferred first-line monotherapy treatment for filamentous fungal keratitis.

Evaluating the in vitro efficacy of gatifloxacin, levofloxacin and gentamicin against Acanthamoeba cysts

PURPOSE

To evaluate the in vitro efficacy of three commercial ophthalmic solutions (gatifloxacin, levofloxacin and gentamicin) against cysts of Acanthamoeba species.

DESIGN

Experimental study METHODS: Acanthamoeba cysts belonging to genotypes T3, T4 and T5 were incubated with three ophthalmic solutions for different periods of time; 1, 24, 48 and 72 h at 37 °C. After incubation, treated cysts were stained with trypan blue and counted to express the percent of growth inhibition. Additionally, the viability of treated cysts was assessed by culturing them in PYG medium at 30 °C for 72 h as well as on non-nutrient agar plates at 30 °C for 1 month.

RESULTS

Acanthamoeba cysts of all genotypes were susceptible to gentamicin and gatifloxacin after exposure for 1 h and 24 h, respectively, and for levofloxacin, cysts of all genotypes were resistant to levofloxacin even after 72 h of incubation. Gentamicin and gatifloxacin showed statistically highly significant difference (P < 0.001), and levofloxacin showed statistically significant difference (P < 0.05) in comparison to non-treated control.

CONCLUSIONS

Gentamicin and gatifloxacin were highly effective against Acanthamoeba cysts. Although our results should be confirmed in animal models, this result will guide the choice of the appropriate ophthalmic drugs for early treatment of eye infection caused by Acanthamoeba spp.

<em>Acanthamoeba</em> keratitis: a challenge in diagnosis and the role of amniotic membrane transplant as an alternative therapy

Acanthamoeba keratitis (AK) is a very rare, sight-threatening corneal disease caused by the infection of a free-living amoeba. The aim of this report was to demonstrate the challenges in the diagnosis of AK with an atypical presentation. Amniotic membrane transplantation (AMT) was done in this case to accelerate wound healing. A woman who frequently used contact lens came with redness and a whitish spot in her left eye 2 weeks before admission. There was a history of rinsing contact lens in tap water. The patient had already been on a topical steroid for 2 weeks. Visual acuity of the left eye was light perception with wrong projection. Examination of the left cornea showed a semi-circular central ulcer with a 5.8-mm area and 1/3 stromal depth. It is surrounded by a feathery-edge infiltrate with positive satellite lesions but without hypopyon. It was diagnosed as corneal ulcers due to mixed infection (bacteria and fungi). After 2 weeks of bacterial and fungal therapy, the size of the ulcer decreased, but the corneal infiltrate remained; therefore, an Acanthamoeba culture was done to determine the possibility of Acanthamoeba infection. Two weeks after the Acanthamoeba topical therapy, the visual acuity improved. AMT was performed to accelerate wound healing. Two months post-AMT, visual acuity improved to 1/60 with no conjunctival or ciliary vasodilation, and the ulcer was resolved. The patient was planned to undergo keratoplasty. The diagnosis of AK with an atypical presentation is challenging. AMT can be used as an alternative therapy to accelerate wound healing.

Combating Acanthamoeba spp. cysts: what are the options?

Acanthamoeba spp. are protist pathogens and causative agents of serious infections including keratitis and granulomatous amoebic encephalitis. Its ability to convert into dormant and highly resistant cysts form limits effectiveness of available therapeutic agents and presents a pivotal challenge for drug development. During the cyst stage, Acanthamoeba is protected by the presence of hardy cyst walls, comprised primarily of carbohydrates and cyst-specific proteins, hence synthesis inhibition and/or degradation of cyst walls is of major interest. This review focuses on targeting of Acanthamoeba cysts by identifying viable therapeutic targets.

Non-contact lens related Acanthamoeba keratitis

The purpose of the study is to describe epidemiology, clinical features, diagnosis, and treatment of Acanthamoeba keratitis (AK) with special focus on the disease in nonusers of contact lenses (CLs). This study was a perspective based on authors' experience and review of published literature. AK accounts for 2% of microbiology-proven cases of keratitis. Trauma and exposure to contaminated water are the main predisposing factors for the disease. Association with CLs is seen only in small fraction of cases. Contrary to classical description experience in India suggests that out of proportion pain, ring infiltrate, and radial keratoneuritis are seen in less than a third of cases. Majority of cases present with diffuse infiltrate, mimicking herpes simplex or fungal keratitis. The diagnosis can be confirmed by microscopic examination of corneal scraping material and culture on nonnutrient agar with an overlay of Escherichia coli. Confocal microscopy can help diagnosis in patients with deep infiltrate; however, experience with technique and interpretation of images influences its true value. Primary treatment of the infection is biguanides with or without diamidines. Most patients respond to medical treatment. Corticosteroids play an important role in the management and can be used when indicated after due consideration to established protocols. Surgery is rarely needed in patients where definitive management is initiated within 3 weeks of onset of symptoms. Lamellar keratoplasty has been shown to have good outcome in cases needing surgery. Since the clinical features of AK in nonusers of CL are different, it will be important for ophthalmologists to be aware of the scenario wherein to suspect this infection. Medical treatment is successful if the disease is diagnosed early and management is initiated soon.