Urgent unmet needs in the care of bacterial keratitis: An evidence-based synthesis

[Bacterial keratitis: Retrospective and prospective 2024]

Bacterial keratitis (BK) is an infection of the cornea caused by one or more bacteria. Contact lens wear is the main risk factor. Staphylococcus and Pseudomonas are the most frequently isolated pathogens in developed countries. BK requires a standardized work-up to avoid diagnostic and therapeutic delays that may negatively affect visual prognosis. Corneal signs, the speed at which lesions progress and the presence of risk factors allow the clinician to presume an empirical microbiological diagnosis, but corneal scraping, which allows the isolation and identification of the bacteria involved in the infection, is the only way to confirm the diagnosis. The type of antibiotic treatment depends on the severity of the lesions, the risk factors involved, and the bacteria identified. Corticosteroids have been shown to be effective as adjuvant therapy and may be used under certain well-defined circumstances. Surgical treatment is sometimes necessary.

Novel ophthalmic hyaluronic acid-hydrogel with curcumin nanoparticles for enhanced healing of ulcerative keratitis in rabbit model

Corneal ulcers, whether melting or indolent, are common in humans and companion animals. Treatment involves local administration of antibiotic eye drops and corneal healing drugs. Compared to traditional treatments for ulcerative keratitis, herbal medicines offer unique advantages, such as potent anti-inflammatory effects and inhibition of proinflammatory cytokines. Curcumin, extracted from the Curcuma Longa plant, possesses extensive pharmacological properties, such as anti-inflammatory, anti-cancer, and antioxidant properties, and is used in various medicines. In this study, we developed a novel ophthalmic drop hydrogel using a formulation of Curcumin NPs encapsulated with β-cyclodextrin and hyaluronic acid, to accelerate corneal healing and improve the quality of healed structures. The formation of Curcumin NPs into Hyaluronic acid-based hydrogels was characterized by zeta, FTIR, and scanning electron microscope (SEM) analyses. A total of 25 healthy male New Zealand Albino rabbits were experimentally induced with ulcerative keratitis and treated individually with topical medication. Rabbits were divided into five groups. Fluorescein dye staining, corneal clarity score, Schirmer tear test, proinflammatory cytokine measurement, and pathologic factors assessments were used to evaluate the optimised Curcumin NPs with β-cyclodextrin in Hyaluronic acid hydrogel. Our results demonstrated that the optimized Curcumin NPs with β-cyclodextrin in hyaluronic acid hydrogel significantly reduced the frequency of medication administration compared to conventional therapies, enhancing the quality of healed structures and effectively treating ulcerative keratitis. All findings in this study provide new insight into designing and fabricating novel ophthalmic medicine for ulcerative keratitis for topical usage.

An injectable hydrogel based on sodium alginate and gelatin treats bacterial keratitis through multimodal antibacterial strategy

Bacterial keratitis is among the most prevalent causes of blindness. Currently, the abuse of antibiotics in clinical settings not only lacks bactericidal effects but also readily induces bacterial resistance, making the clinical treatment of bacterial keratitis a significant challenge. In this study, we present an injectable hydrogel (GS-PNH-FF@CuS/MnS) containing self-assembled diphenylalanine dipeptide (FF) and CuS/MnS nanocomposites (CuS/MnS NCs) that destroy bacterial cell walls through a synergistic combination of mild photothermal therapy (PTT), chemodynamic therapy (CDT), ion release chemotherapy, and self-assembled dipeptide contact, thereby eliminating Pseudomonas aeruginosa. Under 808 nm laser irradiation, the bactericidal efficiency of GS-PNH-FF@CuS/MnS hydrogel against P. aeruginosa in vitro reach up to 96.97 %. Furthermore, GS-PNH-FF@CuS/MnS hydrogel is applied topically to kill bacteria, reduce inflammation, and promote wound healing. Hematoxylin-eosin (H&E) staining, Masson staining, immunohistochemistry and immunofluorescence staining are used to evaluate the therapeutic effect on infected rabbit cornea models in vivo. The GS-PNH-FF@CuS/MnS demonstrate good biocompatibility with human corneal epithelial cells and exhibit no obvious eyes side effects. In conclusion, the GS-PNH-FF@CuS/MnS hydrogel in this study provides an effective and safe treatment strategy for bacterial keratitis through a multimodal approach.

Bacterial and Fungal Keratitis in a Tertiary Care Hospital from Romania

Infectious keratitis is a significant global problem that can lead to corneal blindness and visual impairments. This study aimed to investigate the etiology of infectious bacterial and fungal keratitis, identify the causative pathogens and their antimicrobial resistance patterns, and analyze the risk factors associated with the development of infectious keratitis. The study was observational and retrospective, involving 226 eyes from 223 patients presented at the Ophthalmology Clinic of the County Clinical Emergency Hospital of Craiova, Romania. The inclusion criteria included corneal ulceration/abscess/infiltrate present on slit-lamp examination and positive microbiological sampling for bacteria or fungi. The study found that the most common causes of infectious keratitis were coagulase-negative staphylococci (35.40%), Staphylococcus aureus (11.06%), and Pseudomonas aeruginosa (14.16%). The Gram-positive bacteria showed high resistance rates to penicillin, moderate rates to gentamycin and clindamycin, and low resistance to chinolones. The Gram-negative bacteria were highly resistant to ampicillin and amoxicillin-clavulanic acid, while third-generation cephalosporins, quinolones, and carbapenems were effective. Systemic antibiotics, such as vancomycine, piperacillin-tazobactam, amikacin, and ceftazidime, show promise against keratitis with low resistance rates, whereas carbapenems and topical aminoglycosides had higher resistance, leaving moxifloxacin as a potential topical option for Gram-positive bacteria and Pseudomonas aeruginosa, albeit with resistance concerns for Klebsiella spp. Although fungal keratitis was rare, Fusarium spp. and Candida albicans were the leading fungal pathogens, with incidences of 2.65% and 2.21%, respectively. Candida albicans was broadly susceptible to most antifungals, while Fusarium solani, Curvularia lunata, and Alternaria alternata exhibited resistance to many antifungals. Amphotericin B and caspofungin can be used as systemic antifungals in fungal keratitis. The study also identified risk factors for keratitis such as ocular trauma (65.92%, OR: 2.5), contact lens wear (11.94%, OR: 1.8), and corneal scarring/leukoma (10.17%, OR: 1.6). Keratitis was more frequent in individuals over 60 years old. The findings of this study have implications for the development of effective diagnostic, therapeutic, and preventive strategies for infectious keratitis.

Shotgun metagenomic sequencing in culture negative microbial keratitis

PURPOSE

To evaluate the microbiota of culture negative Corneal Impression Membrane (CIM) microbial keratitis samples with the use of shotgun metagenomics analysis.

METHODS

DNA of microbial keratitis samples were collected with CIM and extracted using the MasterPure™ Complete DNA and RNA Purification Kit (Epicentre). DNA was fragmented by sonication into fragments of 300 to 400 base pairs (bp) using Bioruptor® (Diagenode, Belgium) and then used as a template for library preparation. DNA libraries were sequenced on Illumina® HiSeq2500. The resulting reads were quality controlled, trimmed and mapped against the human reference genome. The unmapped reads were taxonomically classified using the Kraken software.

RESULTS

18 microbial keratitis samples were included in the study. Brevundimonas diminuta was found in 5 samples while 6 samples showed the presence of viral infections. Cutibacterium acnes, Staphylococcus aureus, Moraxella lacunata and Pseudomonas alcaligenes were also identified as the presumed putative cause of the infection in 7 samples.

CONCLUSIONS

Shotgun sequencing can be used as a diagnostic tool in microbial keratitis samples. This diagnostic method expands the available tests to diagnose eye infections and could be clinically significant in culture negative samples.

Solulan C24- and Bile Salts-Modified Niosomes for New Ciprofloxacin Mannich Base for Combatting Pseudomonas-Infected Corneal Ulcer in Rabbits

Keratitis is a global health issue that claims the eye sight of millions of people every year. Dry eye, contact lens wearing and refractive surgeries are among the most common causes. The resistance rate among fluoroquinolone antibiotics is >30%. This study aims at formulating a newly synthesized ciprofloxacin derivative (2b) niosomes and Solulan C24-, sodium cholate- and deoxycholate-modified niosomes. The prepared niosomal dispersions were characterized macroscopically and microscopically (SEM) and by percentage entrapment efficiency, in vitro release and drug release kinetics. While the inclusion of Solulan C24 produced something discoidal-shaped with a larger diameter, both cholate and deoxycholate were unsuccessful in forming niosomes dispersions. Conventional niosomes and discomes (Solulan C24-modified niosomes) were selected for further investigation. A corneal ulcer model inoculated with colonies of Pseudomonas aeruginosa in rabbits was developed to evaluate the effectiveness of keratitis treatment of the 2b-loaded niosomes and 2b-loaded discomes compared with Ciprocin^® (ciprofloxacin) eye drops and control 2b suspension. The histological documentation and assessment of gene expression of the inflammatory markers (IL-6, IL1B, TNFα and NF-κB) indicated that both 2b niosomes and discomes were superior treatments and can be formulated at physiological pH 7.4 compatible with the ocular surface, compared to both 2b suspension and Ciprocin^® eye drops.

Bacterial keratitis: identifying the areas of clinical uncertainty

Bacterial keratitis is a common corneal infection that is treated with topical antimicrobials. By the time of presentation there may already be severe visual loss from corneal ulceration and opacity, which may persist despite treatment. There are significant differences in the associated risk factors and the bacterial isolates between high income and low- or middle-income countries, so that general management guidelines may not be appropriate. Although the diagnosis of bacterial keratitis may seem intuitive there are multiple uncertainties about the criteria that are used, which impacts the interpretation of investigations and recruitment to clinical studies. Importantly, the concept that bacterial keratitis can only be confirmed by culture ignores the approximately 50% of cases clinically consistent with bacterial keratitis in which investigations are negative. The aetiology of these culture-negative cases is unknown. Currently, the estimation of bacterial susceptibility to antimicrobials is based on data from systemic administration and achievable serum or tissue concentrations, rather than relevant corneal concentrations and biological activity in the cornea. The provision to the clinician of minimum inhibitory concentrations of the antimicrobials for the isolated bacteria would be an important step forward. An increase in the prevalence of antimicrobial resistance is a concern, but the effect this has on disease outcomes is yet unclear. Virulence factors are not routinely assessed although they may affect the pathogenicity of bacteria within species and affect outcomes. New technologies have been developed to detect and kill bacteria, and their application to bacterial keratitis is discussed. In this review we present the multiple areas of clinical uncertainty that hamper research and the clinical management of bacterial keratitis, and we address some of the assumptions and dogma that have become established in the literature.