Risk Factors and Causative Organisms in Microbial Keratitis

Characterization of infectious bacterial keratitis in Östergötland County, Sweden: a 10-year retrospective study

BACKGROUND

The aim of this study was to characterize bacterial species, aetiology and antibiotic susceptibility connected to bacterial keratitis infections in Östergötland, Sweden.

METHODS

Retrospective cross-sectional study based on electronic health records for the period 2010-2019. Records of patients diagnosed with infectious keratitis were screened for microbiology confirmed infectious bacterial keratitis. Bacterial species and their susceptibility to antibiotics were determined from microbiology test results.

RESULTS

One-hundred and ninety patients with lab culture-confirmed infectious bacterial keratitis were included in the analysis. The most frequently found bacterial species were coagulase-negative staphylococci (39%), Staphylococcus aureus (17%) and Cutibacterium acnes (10%). Pseudomonas spp. was the most frequently found Gram-negative bacterial species (7%). Contact lens wear and severely ill/blind eye were the top two aetiologies associated with bacterial keratitis, 22% of the patients with bacterial keratitis were also diagnosed with glaucoma. Most isolates, 157 out of 173, were susceptible to fluoroquinolones, and 145 out of 155 isolates were susceptible to chloramphenicol.

CONCLUSION

Our results revealed a positive rate of bacterial keratitis of 59% for the samples sent to the laboratory. There was a high susceptibility of the bacterial species to the recommended antibiotics. Our results indicate that it is likely that patients are receiving the correct treatment. Future studies are necessary to monitor changes in antibiotic susceptibility.

Trends and Clinical Outcomes of Fungal Keratitis in Canada: A 20-year Retrospective Multicentre Study

PURPOSE

An increase in fungal and particularly filamentous keratitis has been observed in many geographic areas, mostly in contact lens wearers. This study seeks to characterize long-term trends in fungal keratitis in a continental climate area to provide guidance for diagnosis and treatment.

DESIGN

Retrospective multicentric case series.

METHODS

Cases of microbiology-confirmed fungal keratitis from 2003 to 2022 presenting to tertiary care centers across Canada were included. Charts were reviewed for patient demographics, risk factors, visual acuity, and treatments undertaken.

RESULTS

A total of 138 patients were identified: 75 had yeast keratitis while 63 had filamentous keratitis. Patients with yeast keratitis had more ocular surface disease (79% vs 28%) while patients with filamentous keratitis wore more refractive contact lenses (78% vs 19%). Candida species accounted for 96% of all yeast identified, while Aspergillus (32%) and Fusarium (26%) were the most common filamentous fungi species. The mean duration of treatment was 81 ± 96 days. Patients with yeast keratitis did not have significantly improved visual acuity with medical treatment (1.8 ± 1 LogMAR to 1.9 ± 1.5 LogMAR, P = .9980), in contrast to patients with filamentous keratitis (1.4 ± 1.2 LogMAR to 1.1 ± 1.3 LogMAR, P = .0093).

CONCLUSIONS

Fungal keratitis is increasing in incidence, with contact lenses emerging as one of the leading risk factors. Significant differences in the risk factors and visual outcomes exist between yeast keratitis and filamentous keratitis which may guide diagnosis and treatment.

Comparison of susceptibility of Pseudomonas aeruginosa isolated from keratitis to antibiotics and multipurpose disinfecting solutions

PURPOSE

This study aimed to assess the susceptibility of ocular isolates of Pseudomonas aeruginosa to two multi-purpose disinfectant solutions (MPDS) and to determine if there was a relationship with resistance to antibiotics.

METHODS

Twenty-three strains of P. aeruginosa isolated from microbial keratitis cases in Australia were utilized in this study. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of two commercially available MPDSs, Biotrue and cleadew MPS were determined. Additionally, the MIC of the strains to five antibiotics, ciprofloxacin, levofloxacin, gentamicin, ceftazidime, and imipenem, were analyzed.

RESULTS

All strains were susceptible to 100 % of each of the MPDS. However, when MPDSs were diluted, cleadew MPS had significantly lower median MIC (median = 12.5 vs 25; p = 0.00008) and MBC (median = 25 vs 50; p = 0.0027) compared to Biotrue. All tested strains were susceptible to levofloxacin and gentamicin. Susceptibility rates to ciprofloxacin, imipenem, and ceftazidime were 52.2 %, 30.4 %, and 91.3 %, respectively. There were no significant relations between MIC or MBC to either MPDS and resistance to the antibiotics (p≧0.23).

CONCLUSION

Both MPDSs were active against P. aeruginosa isolated from microbial keratitis in Australia. However, after dilution, cleadew MPS remained active against P. aeruginosa at lower concentrations. Certain strains of P. aeruginosa were resistant to imipenem, ceftazidime or ciprofloxacin. The lack of association of susceptibility to MPDS and antibiotics suggest that resistance to one did not predispose to resistance to the other.

Demographic and Microbiological Profile of Corneal Ulcers in Eastern India

PURPOSE

To evaluate the microbiological profile of corneal ulcers presenting at a tertiary care eye hospital in eastern Uttar Pradesh (UP), India.

METHODS

This retrospective, observational study included patients with corneal ulcers who underwent corneal scraping and microbiological examination of the sample from May 2014 to October 2023. The demographic details, predisposing factors, and clinical examination data of the patients were noted. Microbiology report of staining and culture (blood agar and Sabaraud's dextrose agar) of corneal scraping sample was analyzed in percentage. Reports of antimicrobial susceptibility testing were also noted and analyzed.

RESULTS

A total of 695 corneal scraping samples were examined during the study period. The mean age of the patients was 45.95 years. Among the patients, 412 (59.28%) were males and 283 (40.72%) were females. Among the patients, 402 (57.84%) belonged to an agricultural background. Trauma was the most common predisposing factor associated with 350 (50.36%) cases. The corneal scraping samples were stain-positive in 455 (65.47%) cases, of which, 130 (28.57%) were gram-positive and 325 (71.43%) were positive on potassium hydroxide (KOH) mount. Culture was positive in 306 (44.03%) cases, of which, bacterial isolates were found in 78 (25.49%), and fungal isolates were found in 228 (74.51%). Fusarium was the most common fungal isolate in 72 (31.58%) cases followed by Aspergillus in 60 (26.32%) cases. Among the bacterial isolates, Staphylococcus aureus was the most common in 20 (25.64%) cases followed by Pseudomonas and Streptococcus. The antimicrobial susceptibility testing showed that 47 (60.26%) of the bacterial isolates were sensitive to fluoroquinolones while the rest 31 (39.74%) were resistant. All the Staphylococcus aureus strains (including four cases of methicillin-resistant Staphylococcus aureus) were susceptible to vancomycin and linezolid, while 7 (35%) were resistant to moxifloxacin. None of the Pseudomonas strains were multidrug resistant. Among the fungal isolates, 220 (96.49%) were susceptible to voriconazole and 189 (82.89%) were sensitive to amphotericin B.

CONCLUSION

Fungal corneal ulcers are more common compared to bacterial ulcers in eastern India, particularly eastern UP and Bihar. This article highlights the importance of microbial testing and provides insight into the prevalent organisms and their antimicrobial susceptibility pattern in this geographic location, the knowledge of which will help clinicians in the appropriate management of these cases.

Photoactivated Chromophore for Keratitis-Corneal Cross-linking (PACK-CXL)-A Scoping Review Based on Preclinical Studies

Purpose

Photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) stabilizes the corneal stroma and eliminates microorganisms. Numerous PACK-CXL protocols, using different energy sources and chromophores, have been applied in preclinical studies, including live animal studies, with various experimental designs and endpoints. So far, a systematic mapping of the applied protocols and consistency across studies seems lacking but is essential to guide future research.

Methods

The scoping review protocol was in line with the JBI Manual for Evidence Synthesis. Electronic databases were searched (Embase, MEDLINE, Scopus, Web of Science) to identify eligible records, followed by a two-step selection process (title and abstract screening, full text screening) for record inclusion. We extracted information on (1) different PACK-CXL protocol characteristics; (2) infectious pathogens tested; (3) study designs and experimental settings; and (4) endpoints used to determine antimicrobial and tissue stabilizing effects. The information was charted in frequency maps.

Results

The searches yielded 3654 unique records, 233 of which met the inclusion criteria. With 103 heterogeneous endpoints, the researchers investigated a wide range of PACK-CXL protocols. The tested microorganisms reflected pathogens commonly associated with infectious keratitis. Bacterial solutions and infectious keratitis rabbit models were the most widely used models to study the antimicrobial effects of PACK-CXL.

Conclusions

If preclinical PACK-CXL studies are to guide future translational research, further cross-disciplinary efforts are needed to establish, promote, and facilitate acceptance of common endpoints relevant to PACK-CXL.

Translational Relevance

Systematic mapping of PACK-CXL protocols in preclinical studies guides future translational research.

Infectious keratitis associated with contact lens wear: REGINFECOR multicenter study

This 32-centre multicentre study addresses the lack of knowledge about the prevalence and significance of microbial keratitis (MK) associated with contact lens (CL) wear in Spain. A total of 304 cases recruited from 32 hospitals were studied and showed that infectious keratitis associated with contact lens wear mainly affects young women during the summer months. In this study, soft lenses with monthly replacement and single solution cleaning were most commonly used, purchased and fitted in opticians' shops. Common risk factors were identified among users, such as topping off solutions, prolonging the life of lenses, and frequently sleeping, swimming and showering with lenses. Overnight lens wear was significantly associated with a higher incidence of corneal opacities, and the presence of Pseudomonas aeruginosa in bacterial cultures was associated with more severe sequelae and a greater need for corneal transplantation. Although most cases were benign, the time taken to heal was long, which poses a problem for working patients. This study provides valuable epidemiological, microbiological and risk factor information and estimates the incidence of CL related MK in Spain to be approximately 1 case per 30,000 inhabitants per year.

Epidemiology of Microbial Keratitis at a Tertiary Care Hospital in Southern Thailand

Purpose

This study aimed to ascertain the microbial profiles and predisposing risk factors for microbial keratitis and to analyze the trend of mixed microbial infection cases over 8 years.

Patients and Methods

In this retrospective analysis, we reviewed the electronic medical records of inpatients diagnosed with microbial keratitis between January 2012 and December 2019. Data on demographics, risk factors, and causative pathogens were analyzed. Multivariate logistic regression models were utilized to identify risk factors associated with pathogens.

Results

This study included 640 eyes of 638 patients. Trauma was the most common predisposing risk factor (57.2%), followed by a combination of factors (14.4%). Among diagnostic test results, bacteria, fungi, and mixed pathogens were identified in 46.72%, 46.56%, and 21.41% of cases, respectively. Positive culture results were obtained in 324 eyes (53.6%), with Pseudomonas aeruginosa (25.1%) and Fusarium spp. (17.4%) being the most prevalent pathogens. In the multivariate logistic regression model, contact lens use, presence of diabetes mellitus, and HIV infection were statistically significant risk factors for Pseudomonas aeruginosa infection (p = 0.001, p = 0.046, and p = 0.04, respectively). Trauma was associated with Fusarium spp. infection (p = 0.001). An increase in the percentage of mixed microbial infection cases was observed when comparing the periods of 2016-2019 with 2012-2015 (p = 0.023).

Conclusion

Bacteria and fungi are equally common causes of microbial keratitis, with Pseudomonas aeruginosa and Fusarium spp. being the predominant pathogens causing bacterial and fungal infections. Trauma is the primary predisposing risk factor for microbial keratitis. There was a notable increase in mixed infection cases over the study period.

Multienzyme-Like Nanozyme Encapsulated Ocular Microneedles for Keratitis Treatment

Keratitis, an inflammation of the cornea caused by bacterial or fungal infections, is one of the leading causes of severe visual disability and blindness. Keratitis treatment requires both the prevention of infection and the reduction of inflammation. However, owing to their limited therapeutic functions, in addition to the ocular barrier, existing conventional medications are characterized by poor efficacy and low bioavailability, requiring high dosages or frequent topical treatment, which represents a burden on patients and increases the risk of side effects. In this study, manganese oxide nanocluster-decorated graphdiyne nanosheets (MnOx/GDY) are developed as multienzyme-like nanozymes for the treatment of infectious keratitis and loaded into hyaluronic acid and polymethyl methacrylate-based ocular microneedles (MGMN). MGMN not only exhibits antimicrobial and anti-inflammatory effects owing to its multienzyme-like activities, including oxidase, peroxidase, catalase, and superoxide dismutase mimics but also crosses the ocular barrier and shows increased bioavailability via the microneedle system. Moreover, MGMN is demonstrated to eliminate pathogens, prevent biofilm formation, reduce inflammation, alleviate ocular hypoxia, and promote the repair of corneal epithelial damage in in vitro, ex vivo, and in vivo experiments, thus providing a better therapeutic effect than commercial ophthalmic voriconazole, with no obvious microbial resistance or cytotoxicity.

The effect of climatic and seasonal factors on the microbial keratitis profile

PURPOSE

To compare retrospective data on microbial keratitis (MK) from two different climatic regions in Turkey over 11 years.

STUDY DESIGN

Retrospective cohort.

METHODS

This retrospective cohort study included patients diagnosed with presumed MK at two referral centers. Center A was located in the subtropical region of Turkey, whereas Center B was located in a continental temperate climate zone. Clinical and laboratory data were also recorded. The results were evaluated for seasonal variations.

RESULTS

This study included data from 665 patients with presumed MK (351 and 314 patients from centers A and B, respectively). The most common predisposing factors were ocular trauma in Center A, prior ocular surgery, and systemic disease in Center B. Severe keratitis was related to prior ocular surgery, presence of systemic disease, and fungal infection at presentation. The culture positivity rate was higher in spring and lower in summer at both centers. Gram-positive bacteria were the most commonly isolated bacteria in both centers in all seasons. The fungal and mixed keratitis ratios were higher in Center A than in Center B. In Center A, filamentous fungi were common pathogens that were found year-round, and peaks were observed in July and October.

CONCLUSION

The results of this study show that climatic and seasonal factors may affect the microbial profile of keratitis. Fungal keratitis appears to be a climatic disease. Understanding the regional profile of MK can aid clinicians in their disease management.

The role of corneal biopsy in the management of microbial keratitis

PURPOSE

Corneal biopsy helps in diagnosing deep-seated or recalcitrant lesions of microbial keratitis (MK). We aim to analyze its role in managing these challenging cases.

METHODS

This is a retrospective review of 22 cases of corneal biopsy at our institute from January 2010 to December 2021. Data were retrospectively collected using the electronic medical record (EMR) system. Those cases of indolent, progressive MK or deep-seated lesions where cornea scraping was not possible were considered for corneal biopsy to establish the microbiological diagnosis. The primary aims of our study were to analyze the indications, success rates, and outcomes for biopsy patients in our series. Additional outcomes that were analyzed included the average time from presentation to biopsy, the type of causative organism isolated from the biopsy by either histopathological or microbiological method, and the frequency and outcome of surgical interventions performed. Descriptive statistics using mean (±standard deviation) and median (±range) were used to interpret the demographic data.

RESULTS

Overall, 15 of 22 patients (68%) had a positive corneal biopsy after microbiological or histopathological examinations. The most identified organism was microsporidia (n = 4,30.7%), followed by mycobacteria (n = 2,15.4%), gram-negative bacilli (n = 2,15.4%), acid-fast bacilli (n = 1,7.6%), fungus (n = 2,15.4%), gram-positive cocci (n = 1,7.6%), and mixed bacterial infection (n = 1,7.6%).

CONCLUSION

Corneal biopsy should be considered a diagnostic modality for patients with deep-seated or unresponsive MK. It can improve the treatment for MK, ensuring targeted therapy.

Antimicrobial resistance in ocular infection: A review

Antimicrobial resistance (AMR) is a global public health threat with significant impact on treatment outcomes. The World Health Organization's Global Action Plan on AMR recommended strengthening the evidence base through surveillance programs and research. Comprehensive, timely data on AMR for organisms isolated from ocular infections are needed to guide treatment decisions and inform researchers and microbiologists of emerging trends. This article aims to provide an update on the development of AMR in ocular organisms, AMR in bacterial ocular infections and on AMR stewardship programs globally. The most common ocular pathogens are Pseudomonas aeruginosa, Staphylococcus spp., Streptococcus pneumoniae, and Haemophilus influenzae in ocular infections. A variety of studies and a few surveillance programs worldwide have reported on AMR in these infections over time. Fluoroquinolone resistance has increased particularly in Asia and North America. For conjunctivitis, the ARMOR cumulative study in the USA reported a slight decrease in resistance to ciprofloxacin. For keratitis, resistance to methicillin has remained stable for S. aureus and CoNS, while resistance to ciprofloxacin has decreased for MRSA globally. Methicillin-resistance and multidrug resistance are also emerging, requiring ongoing monitoring. Antimicrobial stewardship (AMS) programmes have a critical role in reducing the threat of AMR and improving treatment outcomes. To be successful AMS must be informed by up-to-date AMR surveillance data. As a profession it is timely for ophthalmology to act to prevent AMR leading to greater visual loss through supporting surveillance programmes and establishing AMS.

Corneal Specialists' Confidence in Identifying Causal Organisms of Microbial Keratitis

PURPOSE

Microbial keratitis (MK) is a potentially blinding corneal disease caused by an array of microbial etiologies. However, the lack of early organism identification is a barrier to optimal care. We investigated clinician confidence in their diagnosis of organism type on initial presentation and the relationship between confidence and presenting features.

METHODS

This research presents secondary data analysis of 72 patients from the Automated Quantitative Ulcer Analysis (AQUA) study. Cornea specialists reported their confidence in organism identification. Presenting sample characteristics were recorded including patient demographics, health history, infection morphology, symptoms, and circumstances of infection. The association between confidence and presenting characteristics was investigated with 2-sample t-tests, Wilcoxon tests, and Chi-square or Fisher's exact tests.

RESULTS

Clinicians reported being "confident or very confident" in their diagnosis of the causal organism in MK infections for 39 patients (54%) and "not confident" for 33 patients (46%). Confidence was not significantly associated with patient demographics, morphologic features, or symptoms related to MK. MK cases where clinicians reported they were confident, versus not confident in their diagnosis, showed significantly smaller percentages of previous corneal disease (0% versus 15%, p = 0.017), were not seen by an outside provider first (69% versus 94%, p = 0.015), or had no prior labs drawn (8% versus 33%, p = 0.046), and a significantly larger percentage of cases wore contact lenses (54% versus 28%, p = 0.029).

CONCLUSION

In almost half of MK cases, cornea specialists reported lack of confidence in identifying the infection type. Confidence was related to ocular history and circumstances of infection but not by observable signs and symptoms or patient demographics. Tools are needed to assist clinicians with early diagnosis of MK infection type to expedite care and healing.

Biocidal Efficacies of Contact Lens Disinfecting Solutions Against International Organization for Standardization (ISO) Compendial Organisms

Purpose

This study was conducted to evaluate and compare the in vitro disinfection efficacies of six commercial lens cleaning and disinfecting products for planned replacement soft contact lenses.

Methods

Disinfection efficacies of five multi-purpose solutions (MPSs) and one hydrogen peroxide solution (HPS) as control were evaluated in the presence of organic soil according to the International Organization for Standardization (ISO, Geneva, Switzerland) ISO 14729 stand-alone test protocol. The five specified compendial organisms, three bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, and Serratia marcescens) and two fungi (Candida albicans and Fusarium solani) were incubated with each solution under standard conditions, after which microbes were recovered and quantified.

Results

Each of the solutions evaluated met or exceeded the standard's primary criteria (3-log reduction of bacteria and 1-log reduction of fungi) after incubation for the manufacturer-recommended soaking time, except for COMPLETE MPS, which achieved only 0.4 ± 0.1 average log reduction for C. albicans. However, differences in efficacy between the solutions were noted. Average log reduction across all microbes for Biotrue Hydration Plus (4.6 ± 0.1) was comparable to that for CLEAR CARE PLUS HPS (4.3 ± 0.1) and greater than those for OPTI-FREE puremoist (3.6 ± 0.1), OPTI-FREE Replenish (4.0 ± 0.2), ACUVUE RevitaLens (3.9 ± 0.03), and COMPLETE MPS (3.6 ± 0.1). Biotrue Hydration Plus was especially effective at reducing the population of C. albicans (4.2 ± 0.7-log reduction).

Conclusion

Products marketed for planned replacement soft CL disinfection generally meet the ISO 14729 standard's primary criteria for reducing populations of compendial organisms, with larger differences between solutions noted with C. albicans.

Hydroquinine Enhances the Efficacy of Contact Lens Solutions for Inhibiting Pseudomonas aeruginosa Adhesion and Biofilm Formation

P. aeruginosa is one of the most common bacteria causing contact lens-related microbial keratitis (CLMK). Previous studies report that disinfecting solutions were ineffective in preventing biofilm formation. Solutions containing novel natural agents may be an excellent alternative for reducing the risk of CLMK. Here, we investigate the disinfecting properties of hydroquinine in combination with multipurpose solutions (MPSs) to prevent P. aeruginosa adhesion and biofilm formation. We examined the antibacterial, anti-adhesion, and anti-biofilm properties of hydroquinine-formulated MPSs compared to MPSs alone. Using RT-qPCR, hydroquinine directly affected the expression levels of adhesion-related genes, namely, cgrC, cheY, cheZ, fimU, and pilV, resulting in reduced adhesion and anti-biofilm formation. Using ISO 14729 stand-alone testing, hydroquinine met the criteria (>99.9% killing at disinfection time) against both P. aeruginosa reference and clinical strains. Using the crystal violet retention assay and FE-SEM, MPSs combined with hydroquinine were effective in inhibiting P. aeruginosa adhesion and destroying preexisting biofilms. This report is the first to highlight the potential utility of hydroquinine-containing formulations as a disinfecting solution for contact lenses, specifically for inhibiting adhesion and destroying biofilm. These findings may aid in the development of novel disinfectants aimed at combating P. aeruginosa, thereby potentially reducing the incidence of CLMK.

Debulking corneal biopsy with tectonic amniotic membrane transplantation in refractory clinically presumed fungal keratitis

The treatment of fungal keratitis (FK) is challenging due to the subacute indolent course, and initial misdiagnosis. In this retrospective case series, we highlight both the diagnostic and therapeutic roles of corneal biopsy together with amniotic membrane transplantation (AMT) in patients with refractory clinically presumed FK. Debulking biopsy and tectonic AMT were performed during the initial presentation. Biopsy specimens were sent for KOH smears and cultures. After KOH smears confirmed the presence of fungal elements, topical voriconazole 1% was prescribed for the first 72 h then tailored according to the clinical response and the culture results. The outcome measures were complete resolution of infection and restoration of corneal integrity. Cases associated with culture proven bacterial keratitis were excluded. Twelve cases were included in the study. KOH smears confirmed the presence of fungal growth in all specimens. Cultures grew Aspergillus in 6/12 cases, sensitive to voriconazole (5/6) and amphotericin (3/6); Fusarium (4/12), sensitive to both voriconazole and amphotericin; and no growth in 2/12 cases. Amphotericin 0.15% eye drops were added to the 7 cases with proven sensitivity and to the remaining 2 culture negative cases. Gradual resolution of infection was seen in all cases after 35.6 ± 7.8 days. In FK, a debulking biopsy simultaneously with AMT help decrease the microbial load, suppress the inflammatory process, support the corneal integrity, confirm the presence of fungal pathogen.

Infectious and Noninfectious Corneal Ulcers in Ocular Graft-Versus-Host Disease: Epidemiology, Clinical Characteristics, and Outcomes

PURPOSE

To evaluate the incidence, clinical characteristics, microbiological profile, and therapeutic outcomes of corneal ulcers in individuals with chronic ocular graft-vs-host disease (coGVHD).

DESIGN

Retrospective clinical cohort study.

METHODS

Review of individuals diagnosed with coGVHD following hematopoietic stem cell transplantation (HSCT) who were seen at the Bascom Palmer Eye Institute between May 2010 and November 2021. Baseline demographics, clinical characteristics, microbiological profile, risk factors for corneal ulceration, and treatment outcomes were collected. Etiology was deemed infectious in individuals with a positive culture or appropriate clinical scenario (presence of stromal infiltrate or hypopyon); otherwise, ulcers were presumed to be noninfectious. Treatment success was defined as reepithelialization with infiltrate resolution, and treatment failure as progression to corneal perforation or keratoplasty. Kaplan-Meier survival analysis estimated the incidence of ulceration. Cox regression analyses examined demographic and risk factors. Infectious and noninfectious ulcer groups were compared using 2-way independent t tests, 1-way analysis of variances, and χ2 tests, as appropriate.

RESULTS

173 individuals were included (53.7±14.4 years old; 59.0% male). Thirty-three individuals developed an ulcer 74.5±54.3 months after HSCT, with estimated 5- and 10-year incidences of 14% and 30%, respectively. Twenty-two (66.6%) ulcers were deemed infectious (15 microbiologically confirmed, 7 clinically) and 11 (33.3%) were deemed noninfectious. Risk factors for corneal ulceration included Black race (hazards ratio [HR] 2.89, 95% CI 1.30-6.42, P < .01), previous ocular surgery (HR 9.16, 95% CI 3.86-21.72, P < .01), eyelid margin abnormalities (HR 3.44, 95% CI 1.69-6.99, P < .01), and topical steroid use (HR 2.74, 95% CI 1.33-5.62, P < .01). Conversely, contact lens use reduced the risk of corneal ulceration (HR 0.29, 95% CI 0.13-0.66, P < .01). Infectious ulcers had a significantly higher frequency of treatment failure than noninfectious ulcers (57.1% vs 20.0%, P = .04).

CONCLUSION

Corneal ulceration is a potential complication of coGVHD, with several clinical features identified as risk factors. Infectious ulcers had worse outcomes than noninfectious ulcers.

A Comparison of Culture Results and Visual Acuity in Contact Lens Related Microbial Keratitis

PURPOSE

Evaluate the effect of corneal and contact lens-related (CLR) culture results on visual acuity (VA) in patients with microbial keratitis (MK).

METHODS

MK patients with corneal and CLR cultures were identified in the University of Michigan electronic health record from August 2012 to April 2022. Test results were classified as laboratory-positive or laboratory-negative. Linear regression was used to examine trends of VA and associations between changes in VA (differences of VA at 90-day and baseline VA) and corneal and CLR culture results, after adjustment for baseline VA. One-sample t-tests were used to test if the slope estimates were different from zero.

RESULTS

MK patients (n = 50) were on average 49 years old (standard deviation = 20.9), 56% female, and 90% White. Positive corneal and CLR cultures were reported in 60% and 64% of patients, respectively, and 38% reported both. The agreement rate between corneal and CLR culture results was 30% (n = 15/50). LogMAR VA improved over time in patients with positive corneal and CLR cultures (Estimate=-0.19 per 10-day increase, p = 0.002), and in those with negative corneal and positive CLR cultures (Estimate= -0.17 per 10-day increase, p = 0.004). Compared to patients with negative corneal and CLR cultures, there was a trend toward improvement in VA for patients with positive corneal and CLR cultures (Estimate=-0.68, p = 0.068), and those with negative corneal and positive CLR cultures (Estimate= -0.74, p = 0.059), after adjusting for baseline VA.

CONCLUSIONS

Positive CLR cultures are associated with significant improvement in VA over time. These additional cultures can provide guidance on appropriate antimicrobial selection, especially when corneal cultures are negative.

Staphylococcus aureus-derived virulent phenol-soluble modulin α triggers alarmin release to drive IL-36-dependent corneal inflammation

Methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients with keratitis produces substantial amounts of phenol-soluble modulin α (PSMα). However, the role of PSMα in S. aureus keratitis remains unclear. We observed that PSMα-producing and PSMα-deficient strains could infect the cornea in our experimental mouse keratitis model; however, only the PSMα-producing strain delayed epithelial wound healing and induced stromal inflammation. PSMα induced damage to the epithelium, the release of alarmins IL-1α and IL-36α, and the expression of inflammatory chemokines by resident corneal cells in the mouse corneal organ culture. The IL-36 (but not IL-1) receptor antagonist attenuated mouse keratitis induced by PSMα-containing bacterial culture supernatants, as well as by infection with PSMα-producing S. aureus, suggesting that the corneal inflammations were dependent on IL-36. Recombinant PSMα elicited IL-36-dependent corneal inflammation in mice. Thus, PSMα and the subsequently released IL-36 are critical factors triggering inflammation during S. aureus keratitis.

Microbial Keratitis Isolates at a Midwestern Tertiary Eye Care Center

PURPOSE

The aim of the study was to describe the pathogen, antimicrobial susceptibility, and trends over time of microbial keratitis (MK) at a Midwestern tertiary eye center.

METHODS

Patients with MK were identified in the electronic health record from August 2012 to December 2021. Diagnostic laboratory tests with an MK diagnosis were identified and classified as laboratory positive or laboratory negative. Laboratory-positive infections were categorized as bacterial (gram-positive, gram-negative, or acid-fast bacilli), fungal, viral, Acanthamoeba , or polymicrobial. Antimicrobial susceptibilities were obtained. Trends over time were assessed using linear regression.

RESULTS

Of 3288 patients with MK identified, 1012 (30.8%) had laboratory tests performed. Laboratory-positive infections (n = 499, 49.3%) were bacterial in 73.5% (n = 367) of cases, fungal in 7.8% (n = 39), viral in 1.6% (n = 8), Acanthamoeba in 1.4% (n = 7), and polymicrobial in 15.6% (n = 78). Of bacterial infections, 70% (n = 257) were gram-positive, with coagulase-negative Staphylococcus (CoNS; 31%) and Staphylococcus aureus ( S. aureus ; 23%) as the most common pathogens. Bacteria were acid-fast bacilli in 1.9% (n = 7) of cases and gram-negative in 28.1% (n = 103), with Pseudomonas aeruginosa as the predominant pathogen (47.7%). S. aureus showed antibiotic resistance from 0% (vancomycin and gentamicin) to 50% (erythromycin); CoNS from 0% (vancomycin, gentamicin, and moxifloxacin) to 64% (erythromycin). The rate of laboratory-negative MK significantly increased over time (slope estimate = 2.1% per year, P = 0.034). Rates of bacterial, fungal, viral, Acanthamoeba , and polymicrobial infections were stable over time (all slope P > 0.05).

CONCLUSIONS

Bacterial keratitis accounted for most MK cases. Gram-positive bacteria were the most common isolates. CoNS and S. aureus were universally susceptible to vancomycin. Rates of MK infection types were stable over time.

Multifunctional Polymer Vesicles for Synergistic Antibiotic-Antioxidant Treatment of Bacterial Keratitis

As an acute ophthalmic infection, bacterial keratitis (BK) can lead to severe visual morbidity, such as corneal perforation, intraocular infection, and permanent corneal opacity, if rapid and effective treatments are not available. In addition to eradicating pathogenic bacteria, protecting corneal tissue from oxidative damage and promoting wound healing by relieving inflammation are equally critical for the efficient treatment of BK. Besides, it is very necessary to improve the bioavailability of drugs by enhancing the ocular surface adhesion and corneal permeability. In this investigation, therefore, a synergistic antibiotic-antioxidant treatment of BK was achieved based on multifunctional block copolymer vesicles, within which ciprofloxacin (CIP) was simultaneously encapsulated during the self-assembly. Due to the phenylboronic acid residues in the corona layer, these vesicles exhibited enhanced muco-adhesion, deep corneal epithelial penetration, and bacteria-targeting, which facilitated the drug delivery to corneal bacterial infection sites. Additionally, the abundant thioether moieties in the hydrophobic membrane enabled the vesicles to both have ROS-scavenging capacity and accelerated CIP release at the inflammatory corneal tissue. In vivo experiments on a mice model demonstrated that the multifunctional polymer vesicles achieved efficient treatment of BK, owing to the enhanced corneal adhesion and penetration, bacteria targeting, ROS-triggered CIP release, and the combined antioxidant-antibiotic therapy. This synergistic strategy holds great potential in the treatment of BK and other diseases associated with bacterial infections.

PM10 and Pseudomonas aeruginosa: effects on corneal epithelium

Purpose

In vivo data indicate that mouse corneas exposed to PM10 showed early perforation and thinning after infection with Pseudomonas aeruginosa. To understand the mechanisms underlying this finding, we tested the effects of PM10 and the mitochondria targeted anti-oxidant SKQ1 in immortalized human corneal epithelial cells (HCET) that were challenged with Pseudomonas aeruginosa strain 19660.

Methods

Mouse corneas were infected with strain 19660 after a 2 week whole-body exposure to PM10 or control air and assessed by clinical scores, slit lamp photography and western blot. HCET were exposed to 100μg/ml PM10 for 24h before challenge with strain 19660 (MOI 20). A subset of cells were pre-treated with 50nM SKQ1 for 1h before PM10 exposure. Phase contrast microscopy was used to study cell morphology, cell viability was measured by an MTT assay, and ROS by DCFH-DA. Levels of pro-inflammatory markers and anti-oxidant enzymes were evaluated by RT-PCR, western blot and ELISA. Reduced glutathione (GSH) and malondialdehyde (MDA) levels were evaluated by assay kits.

Results

In vivo, whole body exposure to PM10 vs. control air exposed mouse corneas showed early perforation and/or corneal thinning at 3 days post infection, accompanied by increased TNF-α and decreased SOD2 protein levels. In vitro, PM10 induced a dose dependent reduction in cell viability of HCET and significantly increased mRNA levels of pro-inflammatory molecules compared to control. Exposure to PM10 before bacterial challenge further amplified the reduction in cell viability and GSH levels. Furthermore, PM10 exposure also exacerbated the increase in MDA and ROS levels and phase contrast microscopy revealed more rounded cells after strain 19660 challenge. PM10 exposure also further increased the mRNA and protein levels of pro-inflammatory molecules, while anti-inflammatory IL-10 was decreased. SKQ1 reversed the rounded cell morphology observed by phase contrast microscopy, increased levels of MDA, ROS and pro-inflammatory molecules, and restored IL-10.

Conclusions

PM10 induces decreased cell viability, oxidative stress and inflammation in HCET and has an additive effect upon bacterial challenge. SKQ1 protects against oxidative stress and inflammation induced by PM10 after bacterial challenge by reversing these effects. The findings provide insight into mechanisms underlying early perforation and thinning observed in infected corneas of PM10 exposed mice.

Clinical comparative analysis of bacterial keratitis according to contact lens use: a retrospective study in a tertiary referral center of South Korea

PURPOSE

To compare the clinical aspects and treatment outcomes of contact lens-related bacterial keratitis (CLBK) and non-CLBK patients.

METHODS

Altogether 217 patients of bacterial keratitis (CLBK; 62, non-CLBK; 155) hospitalized between January 2012 and December 2020 were retrospectively analyzed for epidemiology, microbiological profiles, predisposing factors, clinical characteristics, and treatment outcomes. Poor treatment outcomes (PTO) were defined as a final BCVA < 0.3 (Snellen), a decreased visual acuity after treatment, complications, or surgical intervention. Relative importance of the initial clinical features leading to PTO was assessed using the random forest model and two-proportion Z-test.

RESULTS

The most common predisposing factors were sleeping with wearing CL (51.6%) in the CLBK group and trauma (55.5%) in the non-CLBK group. There were significant differences between the two groups in mean age (35.1:55.1 years, p < 0.001), female sex (56.5:34.8%, p = 0.003), symptom duration (6.2:6.9 days, p = 0.019), gram-negative organisms (83.3:48.3%, p = 0.008), epithelial healing time (8.5:14.1 days, p = 0.004), final BCVA (0.15:0.46 logMAR, p = 0.015), and PTO (9.7:21.9%, p = 0.035). For the entire group, the initial BCVA < 0.1 (27.9%), symptom duration ≥ 5 days (19.4%), age ≥ 60 years (16.4%), and hypopyon (14.0%) were important initial clinical features leading to PTO in the random forest model. In CLBK group, the type of CL or CL-related history was not significantly related to PTO.

CONCLUSION

CLBK patients had a higher proportion of females, younger age, gram-negative bacteria, and better treatment outcomes than those of non-CLBK patients. There were no significant risk factors leading to PTO in either the type of CL or CL-related history.

Successful treatment of multidrug-resistant Pseudomonas aeruginosa keratitis with meropenem eye drops - a case report

BACKGROUND

This case report describes the course and therapeutic management of a fast-spreading bacterial keratitis caused by multidrug-resistant (MDR) Pseudomonas aeruginosa (P. aeruginosa).

CASE PRESENTATION

A 27-year-old male contact lens wearer presented with a multi-resistant, fast spreading P. aeruginosa keratitis. After initial resistance to various antibiotic therapies, testing revealed a MDR P. aeruginosa. The keratitis was treated successfully with specially prepared 50 mg/ml off-label meropenem eye drops for 18 days as well as systemic meropenem for seven days with rapid improvement of the corneal infiltrate.

CONCLUSION

This case report demonstrates the combination of topical and systemic meropenem as a useful treatment option for corneal ulcers caused by MDR P. aeruginosa.

Challenges and insights in the exploration of the low abundance human ocular surface microbiome

Purpose

The low microbial abundance on the ocular surface results in challenges in the characterization of its microbiome. The purpose of this study was to reveal factors introducing bias in the pipeline from sample collection to data analysis of low-abundant microbiomes.

Methods

Lower conjunctiva and lower lid swabs were collected from six participants using either standard cotton or flocked nylon swabs. Microbial DNA was isolated with two different kits (with or without prior host DNA depletion and mechanical lysis), followed by whole-metagenome shotgun sequencing with a high sequencing depth set at 60 million reads per sample. The relative microbial compositions were generated using the two different tools MetaPhlan3 and Kraken2.

Results

The total amount of extracted DNA was increased by using nylon flocked swabs on the lower conjunctiva. In total, 269 microbial species were detected. The most abundant bacterial phyla were Actinobacteria, Firmicutes and Proteobacteria. Depending on the DNA extraction kit and tool used for profiling, the microbial composition and the relative abundance of viruses varied.

Conclusion

The microbial composition on the ocular surface is not dependent on the swab type, but on the DNA extraction method and profiling tool. These factors have to be considered in further studies about the ocular surface microbiome and other sparsely colonized microbiomes in order to improve data reproducibility. Understanding challenges and biases in the characterization of the ocular surface microbiome may set the basis for microbiome-altering interventions for treatment of ocular surface associated diseases.

Staphylococcus aureus and Pseudomonas aeruginosa infectious keratitis: key bacterial mechanisms that mediate pathogenesis and emerging therapeutics

Bacterial keratitis (bacterial infection of the cornea) is a major cause of vision loss worldwide. Given the rapid and aggressive nature of the disease, immediate broad-spectrum antibiotics are essential to adequately treat this disease. However, rising antibiotic resistance continues to accelerate, rendering many commonly used therapeutics increasingly ineffective. As such, there is a significant effort to understand the basic pathogenesis of common causative organisms implicated in keratitis in part, to fuel the development of novel therapies to treat this blinding disease. This review explores two common causes of bacterial keratitis, Staphylococcus aureus and Pseudomonas aeruginosa, with regards to the bacterial mediators of virulence as well as novel therapies on the horizon.

Managing Corneal Infections: Out with the old, in with the new?

There have been multiple reports of eye infections caused by antibiotic-resistant bacteria, with increasing evidence of ineffective treatment outcomes from existing therapies. With respect to corneal infections, the most commonly used antibiotics (fluoroquinolones, aminoglycosides, and cephalosporines) are demonstrating reduced efficacy against bacterial keratitis isolates. While traditional methods are losing efficacy, several novel technologies are under investigation, including light-based anti-infective technology with or without chemical substrates, phage therapy, and probiotics. Many of these methods show non-selective antimicrobial activity with potential development as broad-spectrum antimicrobial agents. Multiple preclinical studies and a limited number of clinical case studies have confirmed the efficacy of some of these novel methods. However, given the rapid evolution of corneal infections, their treatment requires rapid institution to limit the impact on vision and prevent complications such as scarring and corneal perforation. Given their rapid effects on microbial viability, light-based technologies seem particularly promising in this regard.

A Case Series of Infectious Keratitis After Corneal Cross-linking

PURPOSE

To present the 7-year experience of a tertiary eye hospital while exploring possible risk factors and incidence of infectious keratitis in patients undergoing standard corneal cross-linking (CXL).

METHODS

This retrospective cohort study included patients with progressive keratoconus undergoing standard CXL in the Farabi Eye Hospital and all other patients who had undergone CXL in other facilities and were diagnosed as having infectious keratitis in the 7-year period of the study.

RESULTS

Among the total of 4,863 eyes that underwent CXL, 6 eyes developed infectious keratitis, yielding an incidence rate of 0.12%. Additionally, 13 eyes from 10 patients with a CXL history in other facilities who developed infectious keratitis were included. The mean age was 23.75 years, and 75% of patients were men and 25% were women. Gram-positive bacteria and Staphylococcus aureus were the most prevalent pathogens. Meibomian gland dysfunction, dry eye disease, or blepharitis were present in 12 patients. Medical treatment did not arrest the disease progress in 5 patients, which eventually required cases to undergo keratoplasty.

CONCLUSIONS

This study supports the need for proper patient selection by using a comprehensive medical history. It also highlights the imperative role of rigorous patient education and follow-up, particularly in the first postoperative week. Finally, the study emphasizes aggressive early therapy for patients with suspicious findings. [J Refract Surg. 2023;39(8):564-572.].

Impact of Exposomes on Ocular Surface Diseases

Ocular surface diseases (OSDs) are significant causes of ocular morbidity, and are often associated with chronic inflammation, redness, irritation, discomfort, and pain. In severe OSDs, loss of vision can result from ocular surface failure, characterised by limbal stem cell deficiencies, corneal vascularisation, corneal opacification, and surface keratinisation. External and internal exposomes are measures of environmental factors that individuals are exposed to, and have been increasingly studied for their impact on ocular surface diseases. External exposomes consist of external environmental factors such as dust, pollution, and stress; internal exposomes consist of the surface microbiome, gut microflora, and oxidative stress. Concerning internal exposomes, alterations in the commensal ocular surface microbiome of patients with OSDs are increasingly reported due to advancements in metagenomics using next-generation sequencing. Changes in the microbiome may be a consequence of the underlying disease processes or may have a role in the pathogenesis of OSDs. Understanding the changes in the ocular surface microbiome and the impact of various other exposomes may also help to establish the causative factors underlying ocular surface inflammation and scarring, the hallmarks of OSDs. This review provides a summary of the current evidence on exposomes in various OSDs.

Corneal Culture and Antibiotic Susceptibility Results for Microbial Keratitis in the Mid-Atlantic Region of the United States, 2016 to 2020

OBJECTIVE

To examine the microbial distribution and antimicrobial susceptibility of culture-positive microbial keratitis at a large tertiary referral center in the mid-Atlantic region of the United States.

METHODS

Retrospective review of culture-positive microbial keratitis cases at the Wilmer Eye Institute from 2016 through 2020.

RESULTS

Of the 474 culture-positive microbial keratitis cases, most were bacterial (N=450, 94.9%), followed by fungal (N=48, 10.1%) and Acanthamoeba keratitis (N=15, 3.1%). Of the 450 bacterial isolates, 284 (69.5%) were gram-positive organisms, whereas 157 (28.4%) were gram-negative organisms. The most common bacterial species isolated was coagulase-negative Staphylococcus spp (N=154, 24.8%), and the most common gram-negative isolate was Pseudomonas aeruginosa (N=76, 12.3%). Among fungi, the most common isolates were Candida (N=25, 45.4%), whereas Fusarium (N=6, 10.9%) and Aspergillus (N=3, 5.5%) were less common. Of the 217 bacterial isolates tested for erythromycin susceptibility, 121 (55.7%; ∼60% of coagulase-negative staphylococci and corynebacteria tested) showed resistance to erythromycin.

CONCLUSIONS

Microbial keratitis in the Baltimore Mid-Atlantic region of the United States is most commonly caused by bacteria, with fungi and acanthamoeba being less common. Gram-positive bacterial infections predominate. Among fungal keratitis cases, Candida species are more commonly encountered than are filamentous species. Use of erythromycin as infection prophylaxis should be reexamined. Findings from our study may guide empiric treatment in this geographic region.

Eye disease and international travel: a critical literature review and practical recommendations

RATIONALE FOR REVIEW

Eye diseases pose a significant public health and economic burden, particularly for travellers exposed to ocular hazards who may lack access to specialist eye care. This article offers an evidence-based review for travel-health practitioners, with a particular emphasis on ocular infections and trauma that are more prevalent among travellers. Providing an overview of these issues will allow travel health practitioners to comprehensively address ophthalmic considerations of travel.

METHODS

A systematic literature search was conducted on PubMed and Embase electronic databases, using keywords related to travel medicine and ophthalmology. Inclusion was based on the relevant contribution to epidemiology, aetiology, diagnostics, management and long-term consequences of travel-related eye conditions. The data were analysed using narrative synthesis.

KEY FINDINGS

This literature review highlighted that various travel-related eye conditions may occur. Travellers should be aware of the risk of travel-related ocular complications, which can arise from ocular infections, high-risk activities, high altitude and space travel. The economic and logistical challenges associated with medical tourism for ophthalmic procedures are discussed. For travellers with pre-existing eye conditions or visual impairment, careful planning may be needed to promote eye health and ensure safety of travel.

CONCLUSIONS

Travel medicine practitioners should have a comprehensive understanding of the major ocular risks associated with overseas travel, including eye infections, eye injuries and solar eye damage. Further research in this area can enhance overall wellness and alleviate the burden of ocular diseases on travellers. Evidence-based guidelines based on research can also improve the quality of care and prevent long-term vision problems.

Novel Peptides with Dual Properties for Treating Pseudomonas aeruginosa Keratitis: Antibacterial and Corneal Wound Healing

The corneal epithelium is a layer in the anterior part of eye that contributes to light refraction onto the retina and to the ocular immune defense. Although an intact corneal epithelium is an excellent barrier against microbial pathogens and injuries, corneal abrasions can lead to devastating eye infections. Among them, Pseudomonas aeruginosa-associated keratitis often results in severe deterioration of the corneal tissue and even blindness. Hence, the discovery of new drugs able not only to eradicate ocular infections, which are often resistant to antibiotics, but also to elicit corneal wound repair is highly demanded. Recently, we demonstrated the potent antipseudomonal activity of two peptides, Esc(1-21) and its diastereomer Esc(1-21)-1c. In this study, by means of a mouse model of P. aeruginosa keratitis and an in vivo corneal debridement wound, we discovered the efficacy of these peptides, particularly Esc(1-21)-1c, to cure keratitis and to promote corneal wound healing. This latter property was also supported by in vitro cell scratch and ELISA assays. Overall, the current study highlights Esc peptides as novel ophthalmic agents for treating corneal infection and injury, being able to display a dual function, antimicrobial and wound healing, rarely identified in a single peptide at the same micromolar concentration range.

An X-ray inactivated vaccine against Pseudomonas aeruginosa Keratitis in mice

Pseudomonas aeruginosa (P. aeruginosa) is one of the most prevalent pathogens of bacterial keratitis. Bacterial keratitis is a major cause of blindness worldwide. The rising incidence of multidrug resistance of P. aeruginosa precludes treatment with conventional antibiotics. Herein, we evaluated the protective efficiency and explored the possible underlying mechanism of an X-ray inactivated vaccine (XPa) using a murine P. aeruginosa keratitis model. Mice immunized with XPa exhibit reduced corneal bacterial loads and pathology scores. XPa vaccination induced corneal macrophage polarization toward M2, averting an excessive inflammatory reaction. Furthermore, histological observations indicated that XPa vaccination suppressed corneal fibroblast activation and prevented irreversible visual impairment. The potency of XPa against keratitis highlights its potential utility as an effective and promising vaccine candidate for P. aeruginosa.

Bacterial Keratitis: Clinical Features, Causative Organisms, and Outcome During a 13-year Study Period

PURPOSE

This study aimed to review clinical features, causative organisms, complications, and outcome of bacterial keratitis cases at a tertiary eye hospital.

METHODS

A retrospective study was conducted on clinically diagnosed bacterial keratitis cases from 2007 to 2019. Poor outcome was flagged if any of the following was identified: final visual acuity (VA) worse than 20/200, decrease in VA (1 line or worse compared with presenting VA), corneal perforation, endophthalmitis, failed graft, or cases requiring enucleation or evisceration.

RESULTS

The study included 263 cases of bacterial keratitis with 169 cases (64.3%) of culture-positive bacterial keratitis. Gram-positive bacteria were found to be the causative organism in 106 cases (62.8%). The most common types were coagulase-negative staphylococci (23.1%) and Pseudomonas (23.1%). Culture-positive bacterial keratitis was associated with the development of anterior chamber reaction (≥1+) on multivariate analysis [adjusted odds ratio (OR): 3.03, confidence interval (CI): 1.23-7.45, P = 0.016]. The complications that occurred in the current cohort included visually significant scar (64.7%), perforation (10.8%), cataract (8.8%), nonhealing epithelial defects (8.0%), corneal neovascularization (4.9%), endophthalmitis (4.6%), and hypotony (1.5%). On multivariate analysis, diabetes mellitus (adjusted OR: 3.51, CI: 1.59-7.76, P = 0.002), poor presenting best-corrected VA (adjusted OR: 3.95, CI 1.96-7.96, P < 0.001), and positive cultures (adjusted OR: 2.36, CI: 1.11-5.00, P = 0.025) were associated with poor outcome.

CONCLUSIONS

Culture-negative keratitis had less severe infection and better outcomes when compared to culture-positive bacterial keratitis. Factors associated with poor outcome included diabetes, poor presenting VA, and positive cultures.

Pseudomonas aeruginosa-Derived Extracellular Vesicles Modulate Corneal Inflammation: Role in Microbial Keratitis?

Pseudomonas aeruginosa keratitis occurs following trauma, in immunocompromised patients, and in otherwise healthy contact lens wearers. Characterized by a light-blocking infiltrate, P. aeruginosa keratitis is the most serious complication associated with contact lens wear and, in severe cases, can lead to vision loss. Bacterial extracellular vesicles (B EVs) are membrane-enclosed nanometer-scale particles secreted from bacteria and are packed with bioactive molecules. B EVs have been shown to mediate biological functions that regulate host pathogenic responses. In the present study, we isolated P. aeruginosa-derived EVs using size exclusion chromatography and compared the proteomic compositions and functional activities of P. aeruginosa-derived EVs and P. aeruginosa-derived free protein (FP) on corneal epithelial cells and neutrophils. Importantly, P. aeruginosa-derived EVs and FP exhibited unique protein profiles, with EVs being enriched in P. aeruginosa virulence proteins. P. aeruginosa-derived EVs promoted corneal epithelial cell secretion of interleukin-6 (IL-6) and IL-8, whereas these cytokines were not upregulated following treatment with FP. In contrast, FP had a negative effect on the host inflammatory response and impaired neutrophil killing. Both P. aeruginosa-derived EVs and FP promoted intracellular bacterial survival in corneal epithelial cells. Collectively, these data suggest that P. aeruginosa-derived EVs and FP may play a critical role in the pathogenesis of corneal infection by interfering with host innate immune defense mechanisms.

Predatory bacteria can reduce Pseudomonas aeruginosa induced corneal perforation and proliferation in a rabbit keratitis model

PURPOSE

Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included.

METHODS

Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic ΔlasR mutant and co-injected with PBS or B. bacteriovorus. After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines.

RESULTS

We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n = 24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n = 25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The ΔlasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus.

CONCLUSION

These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

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

Bacterial corneal infections, or bacterial keratitis (BK), are ophthalmic emergencies that frequently lead to irreversible visual impairment. Though increasingly recognized as a major cause of global blindness, modern paradigms of evidence-based care in BK have remained at a diagnostic and therapeutic impasse for over half a century. Current standards of management - based on the collection of corneal cultures and the application of broad-spectrum topical antibiotics - are beset by important yet widely underrecognized limitations, including approximately 30% of all patients who will develop moderate to severe vision loss in the affected eye. Though recent advances have involved a more clearly defined role for adjunctive topical corticosteroids, and novel therapies such as corneal crosslinking, overall progress to improve patient and population-based outcomes remains incommensurate to the chronic morbidity caused by this disease. Recognizing that the care of BK is guided by the clinical axiom, "time equals vision", this chapter offers an evidence-based synthesis for the clinical management of these infections, underscoring critical unmet needs in disease prevention, diagnosis, and treatment.

Predatory Bacteria can Reduce Pseudomonas aeruginosa Induced Corneal Perforation and Proliferation in a Rabbit Keratitis Model

Purpose

Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included.

Methods

Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic Δ lasR mutant and co-injected with PBS or B. bacteriovorus . After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines.

Results

We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n=24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n=25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The Δ lasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus .

Conclusion

These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Automatic Diagnosis of Infectious Keratitis Based on Slit Lamp Images Analysis

Infectious keratitis (IK) is a common ophthalmic emergency that requires prompt and accurate treatment. This study aimed to propose a deep learning (DL) system based on slit lamp images to automatically screen and diagnose infectious keratitis. This study established a dataset of 2757 slit lamp images from 744 patients, including normal cornea, viral keratitis (VK), fungal keratitis (FK), and bacterial keratitis (BK). Six different DL algorithms were developed and evaluated for the classification of infectious keratitis. Among all the models, the EffecientNetV2-M showed the best classification ability, with an accuracy of 0.735, a recall of 0.680, and a specificity of 0.904, which was also superior to two ophthalmologists. The area under the receiver operating characteristics curve (AUC) of the EffecientNetV2-M was 0.85; correspondingly, 1.00 for normal cornea, 0.87 for VK, 0.87 for FK, and 0.64 for BK. The findings suggested that the proposed DL system could perform well in the classification of normal corneas and different types of infectious keratitis, based on slit lamp images. This study proves the potential of the DL model to help ophthalmologists to identify infectious keratitis and improve the accuracy and efficiency of diagnosis.

The NLRP3 Inflammasome Is Required for Protection Against Pseudomonas Keratitis

Purpose

The current study was designed to examine the role of the NLRP3 inflammasome pathway in the clearance of Pseudomonas aeruginosa (PA) infection in mouse corneas.

Methods

Corneas of wild type and NLRP3-/- mice were infected with PA. The severity of bacterial keratitis was graded on days 1 and 3 post-infection by slit lamp, and then corneas were harvested for: (i) bacterial enumeration, (ii) immune cell analysis by flow cytometry, (iii) immunoblotting analysis of cleaved caspase-1 and IL-1β, and (iv) IL-1β quantification by ELISA. In parallel experiments, severity of keratitis was examined in the wild-type mice receiving a subconjunctival injection of a highly selective NLRP3 inhibitor immediately prior to infection.

Results

Compared to wild type mice, NLRP3-/- mice exhibited more severe infection, as indicated by an increase in opacity score and an increase in bacterial load. The hallmark of inflammasome assembly is the activation of proinflammatory caspase-1 and IL-1β by cleavage of their precursors, pro-caspase-1 and pro-IL-1β, respectively. Accordingly, increased severity of infection in the NLRP3-/- mice was associated with reduced levels of cleaved forms of caspase-1 and IL-1β and reduced IL-1β+ neutrophil infiltration in infected corneas. Likewise, corneas of mice receiving subconjunctival injections of NLRP3 inhibitor exhibited increased bacterial load, and reduced IL-1β expression.

Conclusions

Activation of NLRP3 pathway is required for the clearance of PA infection in mouse corneas.

Ciprofloxacin resistance and tolerance of Pseudomonas aeruginosa ocular isolates

PURPOSE

Tolerance to antibiotics may occur due to changes in bacterial growth patterns and can be a precursor to development of resistance. However, there is a lack of information on the ability of ocular bacteria isolates to develop tolerance. This paper explores the tolerance to 8 different antibiotics of 61 microbial keratitis isolates of Pseudomonas aeruginosa from Australia and India using the MBC/MIC ratio, with tolerance defined by a ratio ≥ 32, and tolerance to ciprofloxacin by an agar diffusion assay.

METHODS

Antibiotics used were ciprofloxacin, levofloxacin, gentamicin, tobramycin, piperacillin, imipenem, ceftazidime and polymyxin B. Isolates were sourced from microbial keratitis infections in Australia and India. Minimum bactericidal and minimum inhibitory concentration (MBC and MIC) were obtained using broth microdilution and compared to breakpoints from the Clinical Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) to determine bacterial susceptibility. Tolerance was assessed as MBC/MIC ≥ 32. An alternative method for tolerance detection (TD) was assessed with 13P. aeruginosa sensitive isolates by agar disk diffusion assay of ciprofloxacin followed by application of glucose to the agar and observation of re-growth of colonies.

RESULTS

Thirty-three isolates were resistant to imipenem, 20 to ciprofloxacin, 14 to tobramycin and piperacillin, 12 to levofloxacin and ceftazidime, 8 to gentamicin, and 5 to polymyxin B. The percentage of strains resistant to levofloxacin (7 vs 30 %; p = 0.023), gentamicin (0 vs 24 %; p = 0.005) and tobramycin (4 vs 33 %; p = 0.004) was significantly greater in isolates from India.On average, strains from India exhibited notably greater MIC and MBC values compared to strains obtained from Australia. Out of 61 isolates, none displayed an MBC/MIC ratio ≥ 32. However, three sensitive isolates had low tolerance, nine had medium tolerance and one had high tolerance to ciprofloxacin with the TDtest.

CONCLUSIONS

This study used two methods to determine whether P. aeruginosa strains could show tolerance to antibiotics. Using the MBC/MIC criteria no strain was considered tolerant to any of the eight antibiotics used. When 13 strains were tested for tolerance against ciprofloxacin, the most commonly used monotherapy for keratitis, one had high tolerance and nine had medium tolerance. This demonstrates the capacity of P. aeruginosa to develop tolerance which may result in therapeutic failures if inappropriate dosing regimens are used to treat keratitis.

Pseudomonas aeruginosa: Infections, Animal Modeling, and Therapeutics

Pseudomonas aeruginosa is an important Gram-negative opportunistic pathogen which causes many severe acute and chronic infections with high morbidity, and mortality rates as high as 40%. What makes P. aeruginosa a particularly challenging pathogen is its high intrinsic and acquired resistance to many of the available antibiotics. In this review, we review the important acute and chronic infections caused by this pathogen. We next discuss various animal models which have been developed to evaluate P. aeruginosa pathogenesis and assess therapeutics against this pathogen. Next, we review current treatments (antibiotics and vaccines) and provide an overview of their efficacies and their limitations. Finally, we highlight exciting literature on novel antibiotic-free strategies to control P. aeruginosa infections.

Presumed Microbial Keratitis Cases Resulting in Evisceration and Enucleation in Sydney, Australia

PURPOSE

Describe presumed microbial keratitis cases resulting in evisceration/enucleation from 2012 to 2016 in Sydney, Australia.

METHODS

A retrospective case review included 33 patients. Cases were identified from pathology and hospital coding data. Sociodemographic and clinical details were collated.

RESULTS

Mean age was 79 years (range: 38-100 years), and 64% female. There were 30 eviscerations and 3 enucleations, at a median time of 8 days (range: 1-270 days) due to endophthalmitis (n = 15, 45%). Major ocular associated factors included topical corticosteroid use in 12 patients (36%), exposure keratopathy in 4 (12%), ectropion in 3 (9%), degenerative corneal disease in 3 (9%), and corneal graft in 2 (6%). Pseudomonas aeruginosa was the most common isolate with no reports of antimicrobial resistance.

CONCLUSIONS

Educating elderly patients with a history of topical corticosteroid use, corneal or ocular surface disease about prompt hospital presentation and treatment of microbial keratitis may decrease the probability of losing the eye.

Compliance of Soft Contact Lens Care and Bacterial Contamination Among University Students in Palestine

PURPOSE

This study investigated the contact lens care compliance, noncompliance reasons, bacterial contamination rate, and the behaviors associated with contamination among university students in Palestine.

PATIENTS AND METHODS

133 Habitual soft contact lens wearers were recruited in this study and interviewed using a face-to-face questionnaire, to obtain data on demographics, contact lenses, modifiable lens care behaviors and the reasons for non-compliance. High, moderate, and low lens care behaviors were identified. Additionally, a sample of the participant's storage cases was collected for bacterial contamination testing.

RESULTS

The participants' mean age was 22.4±4.4, with female predominance (62.4%). The average compliance rate was 76.8%. Total CL care compliance (100%) was found in filling the case with adequate solution, not sharing the lenses or storage case with others, while the poorest compliance (>40%) was found in attending after-care visits, checking the solution's expiry, and re-disinfecting the lenses with a fresh solution before insertion after prolonged storage. Poor understanding of the instructions contributed significantly to a low level of compliance (P≤0.05). Gram-positive and gram-negative bacteria were detected in 19.55% of the participants' cases. Poor hand and case hygiene, no replacement of lens cases (monthly), and water exposure were linked to bacterial contamination of storage cases.

CONCLUSION

This study indicated moderate to high compliance in CL care, averaging 76.8%. Poor compliance was found in attending after-care visits, checking the solution's expiry, and re-disinfecting the lenses with a fresh solution after an extended storage interval. 19.55% of the cases had bacterial contamination, with Staphylococcus Aureus being the most common. Poor hand and lens case hygiene and water exposure are found to be associated with lens case contamination. These findings emphasize the importance of patient education on safer lens wear modalities, proper wearing schedules, and hygiene regimens to reduce the risks of developing contact lens complications.

Microbial Adherence to Contact Lenses and Pseudomonas aeruginosa as a Model Organism for Microbial Keratitis

Microbial keratitis (MK), the infection of the cornea, is a devastating disease and the fifth leading cause of blindness and visual impairment around the world. The overwhelming majority of MK cases are linked to contact lens wear combined with factors which promote infection such as corneal abrasion, an immunocompromised state, improper contact lens use, or failing to routinely disinfect lenses after wear. Contact lens-related MK involves the adherence of microorganisms to the contact lens. Therefore, this review discusses the information currently available regarding the disease pathophysiology, the common types of microorganisms causing MK, physical and organic mechanisms of adhesion, material properties which are involved in adhesion, and current antimicrobial strategies. This review also concludes that Pseudomonas aeruginosa is a model organism for the investigation of contact lens microbial adherence due to its prevalence in MK cases, its extremely robust adhesion, antimicrobial-resistant properties, and the severity of the disease it causes.

Glycyrrhizin Interacts with TLR4 and TLR9 to Resolve P. aeruginosa Keratitis

This study tests the mechanism(s) of glycyrrhizin (GLY) protection against P. aeruginosa keratitis. Female C57BL/6 (B6), TLR4 knockout (TLR4KO), myeloid specific TLR4KO (mTLR4KO), their wildtype (WT) littermates, and TLR9 knockout (TLR9KO) mice were infected with P. aeruginosa KEI 1025 and treated with GLY or PBS onto the cornea after infection. Clinical scores, photography with a slit lamp, RT-PCR and ELISA were used. GLY effects on macrophages (Mϕ) and polymorphonuclear neutrophils (PMN) isolated from WT and mTLR4KO and challenged with KEI 1025 were also tested. Comparing B6 and TLR4KO, GLY treatment reduced clinical scores and improved disease outcome after infection and decreased mRNA expression levels in cornea for TLR4, HMGB1, and RAGE in B6 mice. TLR9 mRNA expression was significantly reduced by GLY in both mouse strains after infection. GLY also significantly reduced HMGB1 (B6 only) and TLR9 protein (both B6 and TLR4KO). In TLR9KO mice, GLY did not significantly reduce clinical scores and only slightly improved disease outcome after infection. In these mice, GLY significantly reduced TLR4, but not HMGB1 or RAGE mRNA expression levels after infection. In contrast, in the mTLR4KO and their WT littermates, GLY significantly reduced corneal disease, TLR4, TLR9, HMGB1, and RAGE corneal mRNA expression after infection. GLY also significantly reduced TLR9 and HMGB1 corneal protein levels in both WT and mTLR4KO mice. In vitro, GLY significantly lowered mRNA expression levels for TLR9 in both Mϕ and PMN isolated from mTLR4KO or WT mice after incubation with KEI 1025. In conclusion, we provide evidence to show that GLY mediates its effects by blocking TLR4 and TLR9 signaling pathways and both are required to protect against disease.

Ophthalmic Hydrogel Contact Lens Material Containing Magnesium Oxide Nanoparticles and 3-(Trifluoromethyl)styrene for Biomedical Application

This research was conducted for the synthesis and application of ophthalmic lens materials with improved oxygen permeability and durability. Polyvinylpyrrolidone (PVP), N-vinyl-2-pyrrolidone (NVP), 3-(trifluoromethyl)styrene (3-TFMSt), and magnesium oxide nanoparticles were used as additives for the basic combination of 2-hydroxyethyl methacrylate (HEMA). Additionally, the materials were copolymerized with ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent and azobisisobutyronitrile (AIBN) as the initiator. The addition of magnesium oxide nanoparticles was found to increase the tensile strength from 0.0631 to 0.0842 kgf/mm². Copolymerization with a small amount of 3-TFMSt of about 1% increased the tensile strength to 0.1506 kgf/mm² and the oxygen permeability from 6.00 to 9.64 (cm²/s)∙(mLO₂/mL·mmHg)∙10^-11. The contact lens material produced using N-vinyl-2-pyrrolidone and magnesium oxide nanoparticles as additives satisfied the basic physical properties required for hydrogel contact lenses and is expected to be used usefully as a material for fabricating high-performance hydrogel lenses.

Microbial Contamination of Soft Contact Lenses Among Medical School Students in Southern Iraq

Background

Contamination of CLs and accessories risks potentially devastating microbial keratitis. We aimed to explore the rate of microbial contamination and predisposing factors among a group of asymptomatic young medical students.

Methodology

The study included 115 healthy female medical students with a mean age of 21.64 ± 2.02 years between January and November 2021. Information about CL use, wear and care was gathered. Each participant’s CL and case were swabbed for microbiological identification. Univariable and multivariable analyses were conducted to look for associations with a range of factors.

Results

Overall, 91 participants (79.13%) had at least one contaminated sample (lens and/or case). The rates of contamination of CL and their cases were 66% and 76.5%, respectively. Higher contamination rates were caused by gram-negative bacteria (60% of the contaminated samples) with P. aeruginosa being the most common contaminant both for CL and cases, whereas S. epidermidis and S. aureus were the most common contaminants for the CL and cases, respectively, regarding gram-positive contamination. Multivariable analysis showed younger age as a significant predictor of pseudomonas contamination of the lenses and cases (OR: 12.302, 6.555 for CL & cases, respectively; P = 0.001 for both). Older age was a significant predictor of K. pneumoniae contamination (OR: 4.154, P = 0.007). Pseudomonas contamination of both lenses and cases was predicted by the type of solution used (OR: 10.8 and 13.5, P = 0.001 and 0.003 for bottled and distilled water vs commercially available solutions for CL; OR: 4.5 and 5.8, P = 0.045 and 0.004, respectively, for cases). Pseudomonas case contamination was associated with low frequency of solution change.

Conclusion

Microbial contamination rate of soft CL and their cases is high among young medical students in comparison to previously reported rates and was predisposed by several poor hygienic practices and wearing regimens.

Trends in Infectious Keratitis in Taiwan: An Update on Predisposing Factors, Microbiological and Antibiotic Susceptibility Patterns

Infectious keratitis (IK) represents a major cause of corneal blindness. This study aims to investigate the demographics, risk factors, microbiological characteristics and antibiotic susceptibility patterns of IK in Taiwan over the past 15 years. A retrospective population-based study was conducted using the Chang Gung Research Database. Patients with IK were identified by diagnostic codes for corneal ulcer from 2004 to 2019. Of 7807 included subjects, 45.2% of patients had positive corneal cultures. The proportion of contact lens-related IK declined, while that of IK related to systemic diseases grew. The percentage of isolated gram-positive bacteria surpassed that of gram-negative bacteria in the 15-year period. The prevalence of Pseudomonas aeruginosa showed a decreasing trend (p = 0.004), whereas coagulase-negative Staphylococcus (CNS) and Propionibacterium species were increasingly detected (p < 0.001). Overall, the trend of antibiotic susceptibility of both gram-positive and gram-negative bacteria did not change throughout the study period. The susceptibility to the test antibiotics maintained over 90% in gram-negative isolates over 15 years. Vancomycin preserved 100% susceptibility to all gram-positive isolates. Since most tested antibiotics exhibited stable susceptibility over decades, this study reinforced that fluoroquinolones and fortified vancomycin continue to be good empiric therapies for treating bacterial keratitis in Taiwan.

Impact of the COVID-19 Pandemic on the Incidence and Characteristics of Culture-Positive Microbial Keratitis at a Tertiary Eye Hospital in the UK

Purpose

The COVID-19 pandemic has led to drastic changes to the daily lives of those living in the United Kingdom. We hypothesized that the effect of the imposed lockdown on both behaviour and social interaction has the potential to influence the characteristics of microbial keratitis presenting locally to Manchester Royal Eye Hospital — a major tertiary eye centre in the UK.

Methods

We conducted a retrospective case-note review of all positive corneal scrape cultures identified by our local microbiology laboratory during the year since the announcement of lockdown measures in the UK (23 March 2020 to 23 March 2021). Culture results were compared with previously collated, published “baseline” data from prior to the onset of the COVID-19 pandemic (2004–2019). Statistical analysis was undertaken, predominantly looking at the incidence of microbial keratitis and the variety of cultured pathogens.

Results

A total of 6243 corneal scrape results were reviewed. Comparison of data between the COVID-19 pandemic and subsequent lockdown did not show a significant change in the incidence of culture-positive microbial keratitis: mean annual positive samples during 2004–2019 were 128 (35%) vs 91 (29%) during lockdown (P=0.096). No statistically significant shifts in the incidence of organism subtypes — fungi, acanthamoeba, Gram-positive bacteria, or Gram negative bacteria — were identified (P=0.196, 1, 0.366, and 0.087, respectively).

Conclusion

Contrary to our hypothesis, our results suggest that the COVID-19 pandemic did not alter the incidence or characteristics of microbial keratitis presenting to Manchester Royal Eye Hospital in the year following the implementation of lockdown measures in the UK.