Foldscope: A smartphone based diagnostic tool for fungal keratitis

Purpose:Smartphone-based microscopy tool like foldscope (FS) may serve the purpose of a low-cost diagnostic alternative to the compound light microscope especially in areas with limited resources. The purpose of this study was to detect fungal pathogens causing keratitis on direct smear by smartphone-mounted FS and to evaluate the efficacy of FS against routine compound light microscope (CLM).Methods:The prospective study was conducted at a tertiary eye care center from September 2019 to March 2020. The study included 60 smear examinations (Gram stain [GM] n = 30, Lactophenol Cotton Blue [LCB] n = 30) to detect fungal pathogens from corneal scraping material of clinically suspected fungal keratitis (FK) cases. The diagnostic utility of FS was compared with CLM for both GM and LCB wet mount. Data collected were used to quantify the agreement using Cohen’s kappa between CLM and FS imaging.Results:Forty-six samples out of 60 were positive for fungi using CLM. GM stain and LCB showed 22/30 (73.33%) and 24/30 (80%) positive results with CLM, respectively. Moderate agreement (0.49) was observed between CLM and FS with the smartphone method. LCB mount showed high specificity of 1.00 over 0.87 of GM stain for FS with the smartphone.Conclusion:Direct smear can be an early and sensitive measure to diagnose FK other than clinical suspicion. The smartphone-mounted FS has limited sensitivity as an alternative to CLM, but excellent specificity in the present study for FK. The FS as a smartphone-based diagnostic tool is simple, portable, and inexpensive in resource-constrained rural or remote clinical and public health settings in the absence of CLM and other higher diagnostic modalities.     

Lomefloxacin is an effective treatment of experimental bacterial keratitis

PURPOSE: Lomefloxacin was evaluated as a potential topical therapy for bacterial keratitis. METHODS: Lomefloxacin was compared with ciprofloxacin in different rabbit keratitis models. A total of 216 corneas were infected with Staphylococcus aureus (ciprofloxacin-susceptible and -resistant), Streptococcus viridans, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens and were treated with lomefloxacin (0.3%), ciprofloxacin (0.3% Ciloxan), and the control phosphate-buffered saline (PBS), respectively. The data were analyzed statistically comparing the decrease in the number of recovered viable bacteria. RESULTS: Compared with PBS-treated control corneas, the colony counts for all bacterial isolates were significantly reduced (p < 0.05) after topical treatment with either lomefloxacin or ciprofloxacin. For gram-positive bacteria, lomefloxacin and ciprofloxacin were equally effective. For gram-negative bacteria, lomefloxacin, while effective, was less so than ciprofloxacin under experimental conditions (p < 0.05). CONCLUSION: Our data, using multiple bacterial keratitis models, suggest that lomefloxacin is promising for therapy of bacterial keratitis. Further clinical studies are needed to expand its use for keratitis therapy.     

Topical pefloxacin in bacterial keratitis

Problem: To evaluate the clinical efficacy and safety of topical pefloxacin 0.3% drops as the sole antibiotic used to treat culture positive bacterial corneal ulcers. Methods: Forty two consecutive Gram's smear-positive cases of bacterial corneal ulcers were enrolled for this prospective open labelled clinical trial. All patients underwent a complete clinical and microbiological work up and were put on topical 0.3% pefloxacin drops with supportive cycloplegic, vitamins and antiglaucoma therapy. Of 42 cases, 4 cases of mycotic keratitis and 6 culture negative cases were excluded from the study. Results: Positive microbiologic cultures were obtained in 84.2% (32 of 38) cases. Staphylococcus aureus (14/32; 43.7%) and coagulase negative Staphylococci (12/32; 37.5%) were the two most common organisms isolated. Resolution of the corneal ulcer was achieved in 31 out of 32 cases (96.9%) with a mean duration of 9.3 ± 5.3 days (range 3–21 days). Best corrected visual acuity of 20/200 or better was achieved in 65.6% of cases at 4 weeks post resolution. Corneal deposits were observed in one case which disappeared 8 days following discontinuation of therapy. Conclusions: Topical pefloxacin is effective as a single antibiotic agent for the treatment of bacterial keratitis.     

Is blood agar an alternative to sabouraud dextrose agar for the isolation of fungi in patients with mycotic keratitis

To compare the blood agar (BA), sabouraud dextrose agar (SDA) and chocolate agar (CA) for the isolation of fungi in patients with mycotic keratitis. Corneal Scrapings of 229 patients with clinically diagnosed microbial keratitis were inoculated on BA, SDA, CA. The culture media were evaluated for the rate and time taken for the fungal growth. Seventy six of 229 patients had fungal keratitis. Fungus grew on BA in 60/76(78.9 %), on SDA in 76/76 (100 %), on CA in 40/76(52.6 %) patients. The fungi which grew on BA (60/76) also grown on SDA at the same time. The colony morphologies of different fungi were better on SDA than BA/CA. Among the different culture media, SDA is essential for the isolation fungi in patients with mycotic keratitis.     

Efficacy of transport media use versus direct inoculation of blood agar plates in the microbiologic evaluation of experimental Streptococcus pneumoniae keratitis

PURPOSE: To compare the microbiologic yield of cultures obtained by direct inoculation of blood agar plates (BAP) from corneal ulcer swabbings versus indirect inoculation via transport media in a rabbit model of Streptococcus pneumoniae bacterial keratitis. METHODS: The corneas of 12 rabbits were inoculated with S. pneumoniae. Keratitis was confirmed 18 hours later. Sampling was performed at four 2.5-hour intervals. At each interval, corneal swabs were directly applied to BAP and placed into transport medium: thioglycollate and Amies medium without charcoal. Swabbings were then subcultured onto BAP at two time points: 2 and 24 hours after collection in transport medium. Plates were evaluated 48 hours later. Organism recovery rates were measured in terms of the number of positive culture plates observed and the bacterial colony counts on each plate. RESULTS: The rate of positive cultures overall was 69%. The recovery rates were similar for direct inoculation, inoculation via Amies held for 2 hours, and inoculation via Amies held for 24 hours. Direct inoculation yielded fewer colonies than indirect inoculation via Amies held for 24 hours (p = 0.008). Direct inoculation yielded a higher rate of positive cultures than did thioglycollate held for 2 hours (p = 0.004) or 24 hours (p < 0.001). The rate of nonpneumococcal contaminants ranged from 6% of BAP subcultured from thioglycollate held for 24 hours to 28% of directly inoculated BAP. CONCLUSIONS: Amies medium without charcoal may be used as a transport medium for up to 24 hours in the recovery of S. pneumoniae from corneal ulcers in this rabbit model. Thioglycollate appears to be less effective as a transport medium. Results of this study may justify studies of other transport media and/or other corneal pathogens. Altogether, such studies may provide justification for human clinical trials.     

Fortified antibiotic ointment in bacterial keratitis

We conducted experiments to determine the effectiveness of fortified antibiotic ointment in the treatment of Pseudomonas keratitis in rabbits. We evaluated gentamicin ointment (3, 10, 20, and 40 mg/g), gentamicin solution (3 and 10 mg/ml), and placebo, each given every 30 minutes. We also examined the effectiveness of fortified ointment given in extended treatment intervals. In short-term trials, commercial-strength gentamicin solution (3 mg/ml) was therapeutically superior (P less than .001) to commercial-strength gentamicin ointment (3 mg/g) in reducing corneal bacterial colony counts. No significant difference in antimicrobial effect was noted between fortified gentamicin ointment and fortified gentamicin solution at 30-minute treatment intervals. Fortified gentamicin ointment reduced colony counts even at extended treatment intervals of up to four hours in a severe keratitis model.     

Herpes simplex virus stromal keratitis is not titer-dependent and does not correlate with neurovirulence

We developed a murine model of ocular herpes simplex virus (HSV) disease which is particularly suited for testing stromal keratitis because most animals show some evidence of infection. Using this model, we characterized the ocular disease patterns caused by ten recent low-passage clinical isolates of HSV-1, as well as those caused by the established laboratory strains HSV-1 KOS and HSV-2 333. Viral strains were evaluated for their ability to cause stromal keratitis, blepharitis, vascularization of the cornea, and mortality. The model was not useful for scoring epithelial keratitis. The ocular disease caused by the recent isolates ranged from very mild disease to severe stromal keratitis. Some of the recent isolates caused disease as severe as the two laboratory strains. A comparison of the virulence characteristics expressed by various HSV strains indicated that the ability to cause stromal disease was correlated with vascularization of the cornea (correlation coefficient = 0.797, P less than 0.001) and was not correlated with the neurovirulence of the strains (correlation coefficient 0.045, P greater than 0.05). The severity of stromal keratitis was not dependent on the amount of inoculum over the range tested and a strain causing severe stromal keratitis caused severe ocular disease even when mixed with a nonstromal strain at ratios of 10:1, 100:1, and 1000:1.     

Improvement in corneal scarring following bacterial keratitis

Aim

Bacterial keratitis results in corneal scarring and subsequent visual impairment. The long-term evolution of corneal scars has not been well described. In this case series, we identified patients who had improvement in corneal scarring and visual acuity from a clinical trial for bacterial keratitis.

Methods

We searched the records of the Steroids for Corneal Ulcers Trial (SCUT) for patients who had improvement in vision between the 3-month and 12-month visits and reviewed their clinical photographs.

Results

Of the 500 patients enrolled in SCUT, five patients with large central corneal scars due to bacterial keratitis are presented. All experienced improvement in rigid contact lens–corrected visual acuity from months 3 to 12. All patients also had marked improvement in corneal opacity during the same time period. None of the patients opted to have penetrating keratoplasty.

Conclusions

Corneal scars may continue to improve even many months after a bacterial corneal ulcer has healed. The corneal remodeling can be accompanied by considerable improvement in visual acuity, such that corneal transplantation may not be necessary.     

Amniotic membrane transplantation in severe bacterial keratitis

PURPOSE: To determine whether a combination of early amniotic membrane transplantation (AMT) and early topical corticosteroid treatment could be a safe adjuvant therapy during antibacterial treatment in severe bacterial keratitis (BK) for relieving pain, avoiding iatrogenic epithelial toxicity, and allowing earlier use of topical steroids. METHODS: In a prospective noncomparative case series, 12 patients with severe microscopically-proven BK were treated with immediate maximal topical antibiotics followed by AMT at 48 hours (single-layer epithelial side-down or multilayer epithelial side-up), plus topical steroid treatment at 72 hours. Pain relief (NRS-11 numeric rating pain scale) and the corneal epithelium healing were measured. RESULTS: The follow-up rate was 7.5 person-months, with AMT performed once in 2 patients and twice in 10 patients with BK caused by Pseudomonas aeruginosa (5), Klebsiella pneumoniae (1), Moraxella cattharalis (1), Staphylococcus aureus (1), Staphylococcus epidermidis (2), or Streptococcus pneumoniae (1). A significant decrease in the pain score was noted from the admission day (median, 8; range, 7-10) to shortly after AMT (at day 3: median, 2; range, 1-3). Epithelial healing was achieved between 8 and 45 days (mean, 25.5 +/- 9.7 days). Neither perforation nor neovascularization was observed. CONCLUSIONS: Early AMT combined with topical corticosteroid in severe BK provides immediate pain relief and allows epithelial healing.     

Secondary bacterial keratitis in herpes zoster ophthalmicus

We report a case of an unusual complication of herpes zoster ophthalmicus, secondary bacterial keratitis. Compared with previously reported cases, ours is unique in its early occurrence in the course of zoster and the lack of predisposing factors such as steroid use, contact lens use, or prior corneal disease or surgery. The opportunistic pathogen Branhamella cattarhalis responded well to medical therapy. We feel that bacterial superinfection must always be a concern in patients with herpes zoster keratitis, even early in their often prolonged chronic disease.     

Secondary bacterial infections in herpes simplex keratitis

In nine patients who had herpetic corneal disease, secondary bacterial infections developed. Five of the patients had the ulcers in their own cornea, whereas four had them in corneal transplants in which the graft had been performed because of herpes. All of the patients with grafts were receiving topical steroids when the ulcer developed. Four of the eyes had active herpetic disease at the time of onset, four had no known active disease, and in one it was unknown. The infections respond well to topical treatment except in eyes that had been grafted because of herpes. Staphylococcus was the most frequent invader in these corneas and Pseudomonas aeruginosa was the second most common.     

Analysis of bacterial cultures in infectious keratitis, 1997 to 2004

PURPOSE: To review bacterial culture results in infectious keratitis at a tertiary referral center. DESIGN: Retrospective case series. METHODS: Analysis of Gram stain, bacterial culture, and targeted antibiotic sensitivities of all cases of presumed infectious keratitis at Duke University Eye Center from 1997 to 2004 (n = 453). RESULTS: Cultures were positive in 307 cases (68%); 21% demonstrated polymicrobial growth. Among 388 isolates, 81% were Gram-positive. Gram stain results were available in 334 cases, demonstrating 18% sensitivity and 94% specificity. Antibiotic sensitivities revealed 24% resistance of tested S. aureus isolates to cefazolin, and <5% resistance of tested gram-negative isolates to various antibiotics, with no statistically significant increase from 1997 to 2004. CONCLUSIONS: In this study, the microbial profile has remained stable from 1997 to 2004. Gram stain studies were of poor sensitivity, while culture yields were significantly higher and demonstrated a relatively high polymicrobial infection rate. Increasing antibiotic resistance was not clearly demonstrated.     

Predictive factors for response to medical therapy in bacterial ulcerative keratitis

Background: Fifty-four consecutive cases of culture-positive bacterial ulcerative keratitis presenting at a major university hospital were reviewed to identify factors predictive of response to medical therapy for bacterial ulcerative keratitis (BUK). Methods: Eleven patients (20%) failed medical therapy (defined as the need for surgical intervention or cyanoacrylate gluing). Using multivariate logistic regression, the following variables were evaluated: (1) predisposing ocular factors (e.g., contact lens wear), (2) pre-existing ocular diseases, (3) ulcer size, and (4) the number of topical ocular medications used at the time of presentation. Results: We noted certain factors to be potentially predictive of medical therapy outcome. The average size of the ulcer at the time of presentation was 4.4±2.4 mm in the failure group but only 2.5±1.9 mm for the success group (P=0.027). In addition, patients in the medical failure group used more topical ocular medications at the time of presentation (P=0.0075). Further analysis of the individual topical ocular medications revealed that the use of corticosteroids was higher in the failure group (56% vs 12%, P=0.0005 by Fisher's exact test). Other factors such as patient age, the type of organism(s), and the time elapsed between the onset of symptoms and the beginning of definitive therapy were not statistically significant. Conclusion: In this population, ulcer size at the onset of antibacterial treatment and the use of certain ocular medications, specifically corticosteroids, were significant predictive factors for failure of medical therapy for BUK.     

Factors influencing predilection and outcome in bacterial keratitis

Complete records from 175 patients with 176 episodes of culture-proven bacterial keratitis treated over a 4-year period at the Massachusetts Eye and Ear Infirmary in Boston were analyzed. Sixty-three percent of the infections involved gram-positive organisms, and 40% involved gram-negative organisms; 15% were polymicrobial. There was a high incidence of infection with Staphylococcus aureus (28%), coagulase-negative staphylococci (14%), diphtheroids (14%), Pseudomonas aeruginosa (14%), and Streptococcus pneumoniae (12%). Gram stain correlation was achieved in 55%. Potential predisposing factors, usually multiple, were identified in 97% of the patients. Fifty percent of the ulcers were associated with such iatrogenic factors as prior topical corticosteroid therapy, penetrating keratoplasty, and contact lens use. Trauma occurred in only 16%. Several statistically significant associations of epidemiologic factors and outcome variables were revealed. Ninety-five percent of the ulcers resolved with therapy, but only 44% of the patients had visual acuity better than the level at admission, and 13% developed major complications.