Coinfection with Acanthamoeba and Pseudomonas in Contact Lens–Associated Keratitis

Irrigation in Endodontics: Polyhexanide Is a Promising Antibacterial Polymer in Root Canal Treatment

Background:chronic apical periodontitis is a common pathology in dentistry, especially in endodontics. It is necessary to systematize data concerning commonly used irrigation solutions. The development of new protocols for endodontic treatment is a very promising direction. The use of a polyhexanide-based antiseptic can positively affect the results of endodontic treatment. Methods: the review was carried out involving the search for English language research and meta-analyses in the Google Scholar and PubMed databases. Results: the number of literary sources that were identified during the literature review is 180. After excluding publications that did not match the search criteria, the total number of articles included in the systematic review was determined to be 68. Conclusions: polyhexanide is a promising solution for infected root canal irrigation. The antibacterial activity of this substance is suitable for the elimination of pathogens responsible for the appearance of apical periodontitis.

Case Series: Unusual Presentation of Acanthamoeba Coinfection in the Cornea

SIGNIFICANCE

The cases illustrate Acanthamoeba coinfection with Pseudomonas aeruginosa or microsporidia in the cornea.

PURPOSE

This case series aimed to alert clinicians toward considering Acanthamoeba coinfection in the cornea when unusual presentation such as perineuritis or epitheliitis was observed in clinical images. Increased suspicion of Acanthamoeba coinfection may facilitate early diagnosis and prompt management, eventually leading to good vision outcomes.

CASE SERIES

An 11-year-old boy wearing orthokeratology lens for myopia control complained of pain in the right eye for 1 week. A paracentral corneal ulcer with perineuritis was observed. Culture from corneal tissue revealed P. aeruginosa , and an in vivo confocal microscopic examination showed highly reflective and oval-shaped structures indicating Acanthamoeba coinfection. Corneal lesions gradually improved under 0.02% polyhexamethylene biguanidine, 0.1% propamidine isethionate, and 0.3% ciprofloxacin. At 1 year, the final best-corrected visual acuity was 20/25 with residual paracentral corneal opacity. Another 20-year-old man complained of pain in the right eye for 2 weeks. Multiple raised corneal lesions associated with epitheliitis were found. Moreover, 1% acid-fast staining showed oval-shaped spores, and microsporidia infection was inferred. In addition, polymerase chain reaction results obtained after subjecting the patient to corneal debridement revealed positivity for Acanthamoeba . Polyhexamethylene biguanidine (0.02%) and 0.5% moxifloxacin were prescribed, and the lesions subsided. At a 2-year follow-up, the final best-corrected visual acuity was 20/25.

CONCLUSIONS

Perineuritis in orthokeratology lens wearers and epitheliitis without any predisposing factor are unusual presentations of Acanthamoeba coinfection in the cornea. These corneal findings should arouse the suspicion of coinfection and enable the clinicians to conduct the appropriate workup and initiate adequate treatment. This case series demonstrated that early diagnosis and prompt treatment can improve visual prognosis.

Atypical presentation of acanthamoeba keratitis resembling central toxic keratopathy

PURPOSE

To describe an atypical case of acanthamoeba keratitis with positive in vivo confocal microscopy in a non-contact lens user who presented with signs and symptoms suggestive of central toxic keratopathy.

OBSERVATIONS

The patient presented with bilateral, though sequential, decreased visual acuity with mild pain. Examination showed stromal haze with corneal flattening and thinning without epithelial defects. Optical coherence tonometry of the right eye revealed an inverse dome-shaped appearance of the opacity and in-vivo confocal imaging showed double-walled cysts consistent with acanthamoeba. Corneal haze, stromal loss, resolved and visual acuity improved over time.

CONCLUSION AND IMPORTANCE

Acanthamoeba is a rare cause of infectious keratitis that is most often associated with contact lens wear in developed countries. Typically, it presents with a unilateral decrease in visual acuity, photophobia, watering, and pain that is out of proportion to slit lamp examination findings. However, many atypical presentations have been reported in the literature. Consequently, it may be misdiagnosed, especially early in the course of the disease. This delay in diagnosis can lead to progressive ulceration and visual impairment. In addition, cyst formation can make eradication with anti-amoebic treatment especially difficult.Central toxic keratopathy is a non-inflammatory clinical syndrome of unknown etiology that is most often associated with excimer laser ablation, though other associated causes have been reported. It is characterized by a central or paracentral opacity with corneal stromal loss and resultant hyperopic shift. The opacification and stromal loss mostly resolve over the course of months with an improvement in visual acuity. This report may help physicians broaden their differential and correctly diagnose atypical presentations of amoebic infection.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

Acanthamoeba Keratitis: an update on amebicidal and cysticidal drug screening methodologies and potential treatment with azole drugs

Introduction: Acanthamoeba encompasses several species of free-living ameba encountered commonly throughout the environment. Unfortunately, these species of ameba can cause opportunistic infections that result in Acanthamoeba keratitis, granulomatous amebic encephalitis, and occasionally systemic infection.Areas covered: This review discusses relevant literature found through PubMed and Google scholar published as of January 2021. The review summarizes current common Acanthamoeba keratitis treatments, drug discovery methodologies available for screening potential anti-Acanthamoeba compounds, and the anti-Acanthamoeba activity of various azole antifungal agents.Expert opinion: While several biguanide and diamidine antimicrobial agents are available to clinicians to effectively treat Acanthamoeba keratitis, no singular treatment can effectively treat every Acanthamoeba keratitis case.Efforts to identify new anti-Acanthamoeba agents include trophozoite cell viability assays, which are amenable to high-throughput screening. Cysticidal assays remain largely manual and would benefit from further automation development. Additionally, the existing literature on the effectiveness of various azole antifungal agents for treating Acanthamoeba keratitis is incomplete or contradictory, suggesting the need for a systematic review of all azoles against different pathogenic Acanthamoeba strains.

Genotype distribution of Acanthamoeba in keratitis: a systematic review

Acanthamoeba spp. are among the most worldwide prevalent protozoa. It is the causative agent of a disease known as Acanthamoeba keratitis, a painful and severe sight-threatening corneal infection that can lead to blindness. In recent years, the prevalence of Acanthamoeba keratitis has rapidly increased, growing its importance to human health. This systematic review aims to assess the distribution of Acanthamoeba sp. genotypes causing keratitis around the world, considering the sample collected type and the used identification method. Most of the cases were found in Asia and Europe. Not surprisingly, the T4 genotype was the most prevalent worldwide, followed by T3, T15, T11, and T5. Furthermore, the T4 genotype contains a higher number of species. Given the differences in pathology, susceptibility to treatment, and clinical outcome between distinct genotypes, it is essential to genotype isolates from Acanthamoeba keratitis cases to help to establish a better correlation between in vitro and in vivo activities, resulting in better drug therapies and successful treatment in cases of this important ocular infection.

Acanthamoeba Keratitis Versus Mixed Acanthamoeba and Bacterial Keratitis: Comparison of Clinical and Microbiological Profiles

PURPOSE

To compare the clinical profiles and outcomes of patients with Acanthamoeba keratitis with or without mixed bacterial infection.

METHODS

A retrospective analysis of microbiologically confirmed AK cases presenting to a tertiary care center over a 9-year period was conducted. Fourteen eyes in the coinfected group (group 1) and 24 eyes in the AK group (group 2) were analyzed to study the differences in these 2 groups of patients. The cases were diagnosed using a conventional microscopic analysis with staining techniques confirmed by cultural methods and were treated, which tailored to the microbiology report.

RESULTS

There was no difference in the demographic profile and presenting features in the 2 groups. Duration of symptoms and history of ocular trauma, contact lens wear, and previous steroid usage were also similar for both the groups. Dense central corneal infiltrate was the common presentation for both groups (7/14 vs. 16/24 in group 1 vs. group 2). Epithelial defect without dense stromal infiltrate was significantly more common in group 1 (42.9% vs. 4.2%, P = 0.003) as a presenting clinical feature. Hypopyon was present in 8/14 of group 1 versus 9/24 of group 2 eyes (P = 0.25). No significant difference was found in the final visual acuity in pure and mixed AK cases, and the need for surgical intervention was comparable. The most common bacterial pathogen isolated in the mixed group was the Staphylococcus species.

CONCLUSIONS

Bacterial coinfection is common in patients with Acanthamoeba keratitis. Coinfection did not point toward a worse clinical disease at presentation or outcome.

Effect of Hygiene Procedures on Lens Case Contamination with Povidone-Iodine or Multipurpose Disinfecting Solutions

SIGNIFICANCE

A multipurpose disinfecting solution (MPDS), which contains povidone-iodine (PI) as a disinfectant, has high disinfecting efficacy not only on planktonic bacterium but also on the case biofilms. The addition of case hygiene practice removed more bacteria from cases than MPDS alone.

PURPOSE

This study compared the ability of two MPDSs, one containing PI and another containing polyaminopropyl biguanide and polyquaternium, to reduce bacterial numbers in solution or adhered to the cases following case hygiene procedures.

METHODS

Bacterial strains (Delftia acidovorans, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis) were exposed to the MPDSs for the recommended disinfection times, and the viable number evaluated according to ISO 14729. Cases were inoculated with bacterial strains and incubated for 24 hours to allow for biofilm formation. Cases were disinfected with both disinfecting solutions for 4 hours and rinsed, followed by recapping or air-drying, or tissue-wiping and air-drying for 18 hours. The number of survivors was counted using standard culture techniques.

RESULTS

Both products exceeded the recommended 3-log reduction against planktonic bacteria. Regarding biofilm, after rinsing and recapping wet, the numbers of D. acidovorans (mean difference [95% confidence interval] log10 colony-forming units per case, -2.9 [0.8 to -4.6], P < .01), P. aeruginosa (-2.0 [0.5 to -3.1], P < .01), S. marcescens (-1.7 [0.8 to -3.5], P < .05), and S. epidermidis (-2.1 [0.6 to -3.5], P < .05) in PI cases were significantly lower than in the dual-disinfectant MPDS storage cases. After air-drying, the PI storage cases had significantly lower numbers of S. maltophilia (-2.6 [0.6 to -4.0], P < .01), D. acidovorans (-1.6 [0.7 to -3.3], P < .05), and S. aureus (-1.6 [0.7 to -3.1], P < .05). The addition of tissue-wiping reduced the bacterial numbers in the MPDS storage cases to levels in the PI storage cases.

CONCLUSIONS

Contact lens users should be recommended to tissue-wipe and air-dry their lens storage cases after disinfection with regular MPDS.

Successful Control of a Co-Infection Caused by Candida albicans and Pseudomonas aeruginosa in Keratitis

Nowadays, the co-infection of different classes of pathogens is a major concern. The objective of this study was to develop a successful therapy for keratitis caused by the co-infection of Candida sp. with Pseudomonas sp, which is difficult to cure. The study is based on a 47 years old male farmer showing redness and watering in the right eye for 15-days. ; Methods: The microbiological examination was performed to isolate the causative organisms, i.e. Pseudomonas aeruginosa and Candida albicans. They were cultured separately along with their co-culture and treated with ciprofloxacin and amphotericin B during the growing stage to predict a definite cure. ; Results: Scanning electron microscope (SEM) results confirmed the inter-specific interaction between the two different types of microorganisms. Amphotericin-B and Ciprofloxacin showed the least MIC value for both organisms in co-culture. ; Conclusion: Treatment with Amphotericin-B and 5% ciprofloxacin effectively hindered the growth of Pseudomonas aeruginosa and Candida albicans, the co-infection of which caused keratitis. This therapy may be successfully implied for such cases of co-infection in the future.

Evaluation of in-situ gel-forming eye drop containing bacteriophage against Pseudomonas aeruginosa keratoconjunctivitis in vivo

Introduction: Eradication of Pseudomonas aeruginosa has become increasingly difficult due to its remarkable capacity to resist antibiotics. Bacteriophages have been suggested as an alternative treatment for bacterial infections. Methods: In-situ gel-forming eye drop containing phage against P. aeruginosa keratoconjunctivitis was prepared. The Cystoviridae phage was formulated as in-situ gel-forming formulation which is a solution formulation but turns into gel when it contacts the eye. Therapeutic effectiveness of the in-situ gel forming formulation was evaluated by histological examination on day 12 post-infection. Results: The viscosity of selected formulation increased when it was instilled into the eye. The histological results showed edema, abscesses, and destruction of the stromal structure of cornea in groups where no in-situ gel-forming formulation was used. In the group where in-situ gel forming formulation was used, re-epithelialization and normal corneal structure were observed. Conclusion: In-situ gel-forming ophthalmic formulation containing phage can be effective in the treatment of P. aeruginosa keratoconjunctivitis.

Identification of free-living amoebas and amoeba-resistant bacteria accumulated in Dreissena polymorpha

To identify the free-living amoeba (FLA) and amoeba-resistant bacteria (ARB) accumulated in zebra mussels and in the water in which they are found, mussels were collected at two locations in the Ebro river basin (North East Spain). FLAs and bacteria were isolated from mussel extracts and from natural water. PCR techniques were used to identify the FLAs and endosymbiont bacteria (Legionella, Mycobacterium, Pseudomonas and cyanobacteria), and to detect Giardia and Cryptosporidium. The most frequently found FLAs were Naegleria spp. The presence of Legionella, Mycobacterium and Pseudomonas inside the FLA was demonstrated, and in some cases both Legionella and Pseudomonas were found together. Differences between FLAs and ARB identified inside the mussels and in the water were detected. In addition, Escherichia coli, Clostridium perfringens, Salmonella spp. and Enterococcus spp. were accumulated in mussels in concentrations unconnected with those found in water. The results show the ability of the zebra mussel to act as a reservoir of potentially pathogenic FLAs, which are associated with potentially pathogenic ARB, although the lack of association between microorganisms inside the mussels and in the water suggests that they are not useful for monitoring microbiological contamination at a specific time.

Antiamoebic activity of synthetic tetrazoles against Acanthamoeba castellanii belonging to T4 genotype and effects of conjugation with silver nanoparticles

Acanthamoeba causes diseases such as Acanthamoeba keratitis (AK) which leads to permanent blindness and granulomatous Acanthamoeba encephalitis (GAE) where there is formation of granulomas in the brain. Current treatments such as chlorhexidine, diamidines, and azoles either exhibit undesirable side effects or require immediate and prolonged treatment for the drug to be effective or prevent relapse. Previously, antifungal drugs amphotericin B, nystatin, and fluconazole-conjugated silver with nanoparticles have shown significantly increased activity against Acanthamoeba castellanii. In this study, two functionally diverse tetrazoles were synthesized, namely 5-(3-4-dimethoxyphenyl)-1H-tetrazole and 1-(3-methoxyphenyl)-5-phenoxy-1H-tetrazole, denoted by T1 and T2 respectively. These compounds were evaluated for anti-Acanthamoeba effects at different concentrations ranging from 5 to 50 μM. Furthermore, these compounds were conjugated with silver nanoparticles (AgNPs) to enhance their efficacy. Particle size analysis showed that T1-AgNPs and T2-AgNPs had an average size of 52 and 70 nm respectively. After the successful synthesis and characterization of tetrazoles and tetrazole-conjugated AgNPs, they were subjected to anti-Acanthamoeba studies. Amoebicidal assay showed that at concentration 10 μM and above, T2 showed promising antiamoebic activities between the two compounds while encystation and excystation assays reveal that both T1 and T2 have inhibited differentiation activity against Acanthamoeba castellanii. Conjugation of T1 and T2 to AgNP also increased efficacy of tetrazoles as anti-Acanthamoeba agents. This may be due to the increased bioavailability as AgNP allows better delivery of treatment compounds to A. castellanii. Human cell cytotoxicity assay revealed that tetrazoles and AgNPs are significantly less toxic towards human cells compared with chlorhexidine which is known to cause undesirable side effects. Cytopathogenicity assay also revealed that T2 conjugated with AgNPs significantly reduced cytopathogenicity of A. castellanii compared with T2 alone, suggesting that T2-conjugated AgNP is an effective and safe anti-Acanthamoeba agent. The use of a synthetic azole compound conjugated with AgNPs can be an alternative strategy for drug development against A. castellanii. However, mechanistic and in vivo studies are needed to explore further translational values.

Dendrite-like anterior stromal keratitis coinfected with Acanthamoeba and Pseudomonas in an orthokeratology contact lens wearer

Acanthamoeba species can cause a keratitis misdiagnosed as herpes keratitis or fungal keratitis. We report an unusual dendrite-like anterior stromal keratitis coinfected with Acanthamoeba and Pseudomonas aeruginosa in an orthokeratology contact lens wearer in Taiwan. Topical 1% voriconazole and 0.5% levofloxacin were prescribed because besides Acanthamoeba keratitis, fungal keratitis was also highly suspected initially. Topical 0.02% chlorhexidine was added after the culture of the scraped cornea showed positive results of Acanthamoeba and P. aeruginosa. The lesion subsided using this triple combination therapy for 1 week. Both Acanthamoeba and P. aeruginosa are potentially devastating causes of infectious keratitis. Our case highlights the importance of considering the possibility of a concurrent infection and atypical presentation in cases with contact lens-related keratitis. The use of topical levofloxacin combined with voriconazole should be considered as the first-line treatment in such patients.

Biofilm testing of microbiota: An essential step during corneal scrap examination in Egyptian acanthamoebic keratitis cases

PURPOSE

To detect co-infections in the culture-proven acanthamoebic keratitis (AK) cases, and to test the capability of biofilm formation in the isolated microbiota. The clinical findings, habit of wearing contact lens and in-vitro antibiotic resistance were analyzed further according to the biofilm formation capability.

METHODS

After clinical examination, corneal scraps and swabs were taken from 240 clinically suspected AK cases, for Acanthamoeba and microbiological cultures. In cases of keratoplasty, trimmed corneal tissue was collected and sent for histopathological examination. Scanning electron microscopy was done for some samples. Biofilm formation capability was investigated using a tissue culture plate method. Antibiotic resistance pattern was determined using a modified-Kirby-Bauer disc diffusion method.

RESULTS

In 102 AK culture proven cases, 11 had no co-infection, 74 had a single co-infection and 17 had double co-infections. Enterobactericae and Aspergillus were the commonest bacterial and fungal isolates, respectively. Regarding the biofilm formation, 64.7% of Enterobactericae, 50% of Pseudomonas aeuroginosa, 43.75% of Staph aureus, 76.92% of Streptococcus pneumoniae, 28.57% of Corynebacterium, 60% of α-haemolytic streptococci, 40% of Acinetobacter, 100% of Candida and 77.8% Aspergillus isolates were biofilm producers. Severe manifestations were more frequently reported in cases co-infected with biofilm producers than with non-biofilm producers. Generally, high percentages of the biofilm forming bacterial isolates were sensitive to antibiotics in-vitro.

CONCLUSIONS

Routine investigations for co-infection and biofilm formation in addition to Acanthamoeba culture are strongly recommended in suspected AK cases. Co-infection with biofilm producers may precipitate extrinsic in-vivo drug resistance despite of the in-vitro sensitivity. Designing a biofilm-dissolving topical drug is highly recommended to enhance the response to the standard therapeutic regimen especially in the resistant AK cases.

Diagnostic Evaluation of Co-Occurrence of Acanthamoeba and Fungi in Keratitis: A Preliminary Report

PURPOSE

To test the hypothesis that the coexistence of Acanthamoeba with other forms of microbial keratitis, especially fungal keratitis (FK), is more prevalent than suspected.

METHODS

A prospective diagnostic study whereby patients presenting with stromal keratitis were additionally tested for Acanthamoeba, irrespective of the initial diagnosis. In addition to the routine workup with Gram stain, KOH mount, and cultures on blood agar and potato dextrose agar, nonnutrient agar was included. Confocal microscopy was performed where feasible. Samples for polymerase chain reaction studies were also obtained. We present the preliminary report of the first 100 culture-positive cases. The primary outcome measured was the number of coexistent Acanthamoeba and FK. The secondary outcomes were the total number of Acanthamoeba cases detected and the correlation between clinical diagnosis and microbiological observations.

RESULTS

Of the first 100 cases, 22 were culture positive for Acanthamoeba, of which 9 were associated with concurrent FK, 5 with bacterial keratitis, and 8 in isolation. However, only 2 cases were diagnosed clinically as Acanthamoeba, whereas 5 were Acanthamoeba suspects. An additional 4 cases of fungal/Acanthamoeba coexistence in keratitis were revealed purely by confocal microscopy.

CONCLUSIONS

Acanthamoeba can coexist with other forms of microbial keratitis. The frequency of infection coexistent or otherwise is higher than reported, and the possibility of coinfection must be considered especially in unresponsive cases. Including nonnutrient agar and confocal microscopy in all cases of keratitis would perhaps translate into better treatment strategies and outcomes.

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.

Associated factors, diagnosis and management of Acanthamoeba keratitis in a referral Center in Southern China

BACKGROUND

To analyse the associated factors, diagnosis, clinical manifestations and therapeutic effects of Acanthamoeba keratitis at a tertiary ophthalmic centre in Southern China.

METHODS

A retrospective clinical study was performed in fifteen patients who were admitted to Zhongshan Ophthalmic Centre (ZOC) from January 2004 to December 2014. The patients' pathogenesis-associated factors were analysed, and preoperative diagnoses were determined using corneal scraping cultures and/or confocal microscopy followed. All diagnoses were confirmed by postoperative pathological examinations. At follow-up, best-corrected visual acuity (BCVA), the recurrence rate and graft transparency were evaluated to assess therapeutic effects.

RESULTS

The main pathogenic factors observed in the fifteen patients were a history of injury or a foreign body entering the eyes (12 cases). In all, Acanthamoeba keratitis was preoperatively diagnosed in 5 cases using corneal scraping cultures or confocal microscopy. Ocular symptoms included redness, photophobia, tearing, and blurred vision. Penetrating keratoplasty was performed in thirteen patients, and postoperative pathological examinations were performed to confirm these diagnoses. The logarithm of the minimum angle of resolution (logMAR) of visual acuity was significantly improved after keratoplasty (p < 0.01). No recurrence was observed, and approximately 90% of the corneal grafts were found to be transparent during the follow-up period.

CONCLUSIONS

Corneal trauma may be the main pathogenic factor that causes Acanthamoeba keratitis in southern China. Corneal scraping combined with confocal microscopy was helpful for achieving a correct diagnosis. Early keratoplasty combined with amoebicidal therapy is an effective treatment strategy in Acanthamoeba keratitis.

Polymicrobial Infection of the Cornea Due to Contact Lens Wear

A 38-year-old male presented with pain and redness in his left eye. He had a history of wearing contact lenses. His ophthalmic examination revealed a large corneal ulcer with surrounding infiltrate. Cultures were isolated from the contact lenses, lens solutions, storage cases, and conjunctivae of both eyes and also corneal scrapings of the left eye. Fortified vancomycin and amikacin drops were started hourly. Culture results of conjunctivae of each eye and left cornea were positive for Pseudomonas aeruginosa; cultures from the contact lenses, lens solution and storage case of both eyes revealed Pseudomonas aeruginosa and Alcaligenes xylosoxidans. Polymerase chain reaction of the corneal scraping was positive for Acanthameoba. The topical antibiotics were changed with ones that both bacteria were sensitive to and anti-amoebic therapy was added. The patient had two recurrences following initial presentation despite intensive therapy. Keratitis occurred due to multiple pathogens; the relapsing course despite adequate therapy is potentially associated with this polymicrobial etiology.

The Development of Drugs against Acanthamoeba Infections

For the past several decades, there has been little improvement in the morbidity and mortality associated with Acanthamoeba keratitis and Acanthamoeba encephalitis, respectively. The discovery of a plethora of antiacanthamoebic compounds has not yielded effective marketed chemotherapeutics. The rate of development of novel antiacanthamoebic chemotherapies of translational value and the lack of interest of the pharmaceutical industry in developing such chemotherapies have been disappointing. On the other hand, the market for contact lenses/contact lens disinfectants is a multi-billion-dollar industry and has been successful and profitable. A better understanding of drugs, their targets, and mechanisms of action will facilitate the development of more-effective chemotherapies. Here, we review the progress toward phenotypic drug discovery, emphasizing the shortcomings of useable therapies.

Isolation and Genotyping of Acanthamoeba spp. as Neglected Parasites in North of Iran

Acanthamoeba, a free-living amoeba, is widely distributed in the environment, water sources, soil, dust, and air. It can cause keratitis in contact lens wearers with poor hygiene and also fatal granulomatous amebic encephalitis (GAE) in immunocompromised hosts. The aim of this study was to gain some insights into the distribution and genotypes of the potentially pathogenic species of Acanthamoeba present in water sources in north of Iran. Total 43 Acanthamoeba species were isolated from 77 water samples taken from different water sources within the Mazandaran province in Northern Iran (Sari city and suburbs). Isolates were identified based on cyst and trophozoite morphological characteristics as well genetics. PCR fragments corresponding to the small-subunit 18S rRNA gene were sequenced for 20 of 43 positive isolates. The results revealed that 83.3% of sequenced isolates belonged to the T4 genotype and the rest belonged to the T2 genotype. Our results indicated that Acanthamoeba is widely distributed in Sari city. As the incidence in Iran of amoebic keratitis has increased in recent years, the exact estimation of the prevalence of this amoeba and its predominant genotype may play a crucial role in prevention of the disease. Sari city has several rivers, seashores, and natural recreational amenities, which attract visitors during the year. This is the first report of Acanthamoeba genotypes from water sources in Sari city, Mazandaran province of Iran, and the results suggest that more attention is needed to protect the visiting population and immunocompromised individuals.

Genotyping of Acanthamoeba spp. and characterization of the prevalent T4 type along with T10 and unassigned genotypes from amoebic keratitis patients in India

Free-living amoebae of the genus Acanthamoeba are the causative agents of severe sight-threatening infection of the cornea. This study was designed to characterize the genotype of 20 Acanthamoeba spp. isolates obtained from corneal scrapings of 183 suspected Acanthamoeba keratitis patients reporting to the Outpatient Department/Casualty Services of Dr R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India during the period 2011-2015. Corneal scrapings were inoculated onto 2 % non-nutrient agar plates overlaid with Escherichia coli and incubated at 30 °C for 15 days. Amongst 183 suspected Acanthamoeba keratitis patients, 29 were found culture-positive for Acanthamoeba spp. out of which 20 samples were established in axenic culture for molecular analysis. DNA was isolated and PCR assay was performed for the amplification of the diagnostic fragment 3 (DF3) (∼280 bp) region of the 18S rRNA gene from axenic culture of 20 Acanthamoeba spp. isolates. Rns genotyping was performed on the basis of variation in nucleotide sequences of the DF3 region of the 18S rRNA gene. In the phylogenetic analysis, 16 of the 20 isolates were found to be of prevalent genotype T4, two were of genotype T10 and the remaining two isolates were of unassigned genotypes. Hence, it was concluded that genotype T4 was found as the most predominant genotype involved in Acanthamoeba keratitis infections. Genotype T10, which had not been reported from India, was detected for the first time in two patients. Two isolates were found to be unique, which shared < 95 % homology with all the known genotypes (T1-T20) of Acanthamoeba spp.

Gold Nanoparticle Conjugation Enhances the Antiacanthamoebic Effects of Chlorhexidine

Acanthamoeba keratitis is a serious infection with blinding consequences and often associated with contact lens wear. Early diagnosis, followed by aggressive topical application of drugs, is a prerequisite in successful treatment, but even then prognosis remains poor. Several drugs have shown promise, including chlorhexidine gluconate; however, host cell toxicity at physiologically relevant concentrations remains a challenge. Nanoparticles, subcolloidal structures ranging in size from 10 to 100 nm, are effective drug carriers for enhancing drug potency. The overall aim of the present study was to determine whether conjugation with gold nanoparticles enhances the antiacanthamoebic potential of chlorhexidine. Gold-conjugated chlorhexidine nanoparticles were synthesized. Briefly, gold solution was mixed with chlorhexidine and reduced by adding sodium borohydride, resulting in an intense deep red color, indicative of colloidal gold-conjugated chlorhexidine nanoparticles. The synthesis was confirmed using UV-visible spectrophotometry that shows a plasmon resonance peak of 500 to 550 nm, indicative of gold nanoparticles. Further characterization using matrix-assisted laser desorption ionization-mass spectrometry showed a gold-conjugated chlorhexidine complex at m/z 699 ranging in size from 20 to 100 nm, as determined using atomic force microscopy. To determine the amoebicidal and amoebistatic effects, amoebae were incubated with gold-conjugated chlorhexidine nanoparticles. For controls, amoebae also were incubated with gold and silver nanoparticles alone, chlorhexidine alone, neomycin-conjugated nanoparticles, and neomycin alone. The findings showed that gold-conjugated chlorhexidine nanoparticles exhibited significant amoebicidal and amoebistatic effects at 5 μM. Amoebicidal effects were observed by parasite viability testing using a Trypan blue exclusion assay and flow-cytometric analysis using propidium iodide, while amoebistatic effects were observed using growth assays. In contrast, chlorhexidine alone, at a similar concentration, showed limited effects. Notably, neomycin alone or conjugated with nanoparticles did not show amoebicidal or amoebistatic effects. Pretreatment of A. castellanii with gold-conjugated chlorhexidine nanoparticles reduced amoeba-mediated host cell cytotoxicity from 90% to 40% at 5 μM. In contrast, chlorhexidine alone, at similar concentrations, had no protective effects for the host cells. Similarly, amoebae treated with neomycin alone or neomycin-conjugated nanoparticles showed no protective effects. Overall, these findings suggest that gold-conjugated chlorhexidine nanoparticles hold promise in the improved treatment of A. castellanii keratitis.

An unusual case of Acanthamoeba Polyphaga and Pseudomonas Aeruginosa keratitis

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5168343391150859

A 56-year-old woman with a history of disposable soft contact lens wear was referred to our university eye center for a corneal ulcer. Based on the microbial culture, the initial diagnosis was bacterial keratitis, which was unresponsive to topical fortified antibiotics. The patient was then examined using in vivo confocal microscopy, which revealed Acanthamoeba infection. This case emphasizes the need to suspect Acanthamoeba infection in soft contact lens wearers who present with progressive ulcerative keratitis or progressively worsening corneal ulcers that are not responsive to the usual antimicrobial therapy. It is also important to consider the possibility of a coinfection with bacterial and Acanthamoeba species.