Review articleUnderstanding clinical and immunological features associated with Pseudomonas and Staphylococcus keratitis
Section snippets
Background
Contact lens wear (CLW) is a significant risk factor associated with bacterial keratitis, which accounts for 22–65 % of cases of bacterial keratitis in hospital or casualty-based studies [[1], [2], [3], [4], [5], [6], [7], [8]]. Bacteria is present in 69–95 % of the culture-positive cases of contact lens-related microbial keratitis [3,[9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]]. Pseudomonas aeruginosa [3,9,10,13,[19], [20], [21], [22]] and Staphylococcus aureus [2,[9], [10]
Clinical features of Pseudomonas aeruginosa and Staphylococcus aureus keratitis
The diagnosis of bacterial keratitis in patients is based on presenting symptoms, history, presenting risk factors, clinical examination and the smear and culture of the corneal scrape.
Pathology of contact lens-related bacterial keratitis in animal models
Animal models have provided invaluable insight into the host-response in contact lens-related bacterial keratitis [25,27,72]. Chiefly, two variants of mice (C57BL/6 and BALB/c) have commonly been compared with wild-type mice in both scratch and non-scratch models of both contact lens-related and non-contact lens-related bacterial keratitis. C57BL/6 (or B6) mice are common inbred strains of laboratory mice and are susceptible Th1 responders while BALB/c mice are immunodeficient laboratory-bred
Neutrophils are primary immune mediators in early bacterial keratitis in mice models
Corneal infiltrates in bacterial keratitis are aggregations of neutrophils which accumulate to clear invading pathogens and their antigens. Principally, intercellular communication between infiltrating leukocytes, corneal tissues, and the limbal vascular endothelium determines neutrophil recruitment [74]. In animal studies, rapid neutrophil recruitment drives the host's innate immune response by activating Th1 cells at the site of infection [74,[99], [100], [101]]. Prolonged neutrophil
Summary and future directions
Contact lens-related bacterial keratitis is rapidly progressing acute clinical condition, which requires urgent diagnosis and treatment. In the early stage, contact lens-related bacterial keratitis can be challenging to differentiate from symptomatic sterile infiltrates like CLPU. Certain features may be more suggestive of a specific causative agent. However, confirmed diagnosis of a causative organism requires culture or molecular techniques from corneal scrapes or corneal biopsy.
P. aeruginosa
Acknowledgement
The Scientia PhD Scholarship, UNSW Sydney. We are thankful to Mr Suresh Sharma and Mr Hira Nath Dahal, BP Koirala Lions Centre for Ophthalmic Studies, Institute of Medicine, Kathmandu for providing a clinical photo.
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2022, Progress in Retinal and Eye ResearchCitation Excerpt :Although, the role of corneal endothelium has not been studied extensively in bacterial keratitis, it has been observed that injury to Descemet's membrane causes release of mediators by corneal endothelium which promotes the differentiation of keratocytes to fibroblasts and myofibroblasts causing scar formation and irreversible opacity of posterior stroma (Marino et al., 2017; Medeiros et al., 2019). Patients with infectious keratitis typically present with adnexal and conjunctival edema, reduced vision, excessive ocular pain, conjunctival hyperemia, photophobia and discharge (Eguchi, 2019; Shrestha et al., 2021; R.B. Singh et al., 2021). The clinical signs and symptoms vary from case to case depending upon the virulence of infecting organisms, and the patient's immune response and ocular surface health (Mascarenhas et al., 2014; Ruiz Caro et al., 2017).
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2021, BiomaterialsCitation Excerpt :Approximately 90% of infectious keratitis pertain to bacterial keratitis (BK) [1–3]. In recent years, the number of BK case rises rapidly due to the widely use of extended-wear contact lenses [4,5]. If the BK is not appropriately treated, it will lead to rapid destruction of corneal tissue and inordinate complications with sight-threatening, such as corneal leukoma, endophthalmitis, corneal perforation, and lose of eye ultimately [6,7].