Clinical Features, Antibiotic Susceptibility Profile, and Outcomes of Infectious Keratitis Caused by Stenotrophomonas maltophilia.

PURPOSE: Stenotrophomonas maltophilia, an uncommon cause of infectious keratitis, is difficult to treat because of its resistance to multiple antibiotics. The purpose of this study is to describe the clinical features, antibiotic susceptibility profile, and outcomes of S. maltophilia keratitis. METHODS: A retrospective review of records from 1987 to 2016 identified 26 eyes of 26 patients who were treated at the Bascom Palmer Eye Institute for an S. maltophilia corneal ulcer. Clinical data were analyzed as to predisposing factors, clinical presentation, antibiotic susceptibility, treatment selection, and clinical outcomes. RESULTS: Median age at presentation was 65 years (range, 16-98). Twelve patients were using topical corticosteroids, 8 patients had a history of penetrating keratoplasty, and 9 were contact lens wearers. All patients received topical antibiotics, 2 required therapeutic penetrating keratoplasty, and 1 was enucleated. At presentation, 57.7% (15/26) of the patients had visual acuity of 20/400 or worse. At the final visit, only 30.4% (7/23) of the patients had visual acuity worse than 20/400, whereas 65.2% (15/23) of the patients had 20/100 or better. Almost all isolates (25/26, 96.2%) were susceptible to fluoroquinolones and 77.3% (17/22) of them to polymyxin B/trimethoprim. Only 33.3% (5/15) of the tested isolates were susceptible to aminoglycosides and 58.3% (7/12) to cephalosporins. CONCLUSIONS: Infectious keratitis due to S. maltophilia presents a treatment challenge because of its resistance to aminoglycosides and cephalosporins, which are typically used for empiric broad-spectrum gram-negative coverage as fortified solutions. Fluoroquinolones and polymyxin B/trimethoprim should be considered instead in cases of S. maltophilia infection.

Multiplex Polymerase Chain Reaction Assay for Screening of Mycotoxin Genes From Ocular Isolates of Fusarium species.

PURPOSE: To identify mycotoxin genes among clinical ocular isolates of Fusarium species and to correlate these with clinical outcomes of Fusarium keratitis. METHODS: Fifty-four clinical isolates of Fusarium were retrieved from the Bascom Palmer Eye Institute Ocular Microbiology Laboratory data bank. Multiplex polymerase chain reactions were run to confirm the identification of Fusarium species [internal transcribed spacer sequence, translation elongation factor 1-α (TEF) and ß-tubulin] and to detect the presence of genes encoding production of fumonisin B mycotoxins (FUM1 and FUM8) and trichothecene mycotoxins (deoxynivalenol and nivalenol). The presence or absence of mycotoxins was compared with patient outcomes. RESULTS: Forty-three (79%) of the 54 isolates were confirmed as Fusarium species, by an internal transcribed spacer sequence in 3 (5.6%) and by TEF in 43 (79.6%) of the 54 isolates. Fumonisin biosynthetic gene 1 (FUM1) was detected in 57.4% (n = 31/54) of the Fusarium isolates. No FUM8, deoxynivalenol genes, and nivalenol genes were detected among these in the clinical isolates group. Initial best-corrected visual acuity ranged from 20/25 to 20/80 in the FUM1 gene-negative group and from 20/20 to light perception in the FUM1 gene-positive group. There was no difference in the time to cure between both groups. The presence of FUM1 genes in 5 fungal isolates seemed to be associated with progression to penetrating keratoplasty in the 5 patients from whom the fungi were isolated. Fusarium solani was recovered from all patients requiring penetrating keratoplasty. CONCLUSIONS: Fumonisin B biosynthetic gene 1 may be common among clinical Fusarium isolates and contribute to worse initial visual acuity and high-risk progression to penetrating keratoplasty.

Clinical Features, Antibiotic Susceptibility Profiles, and Outcomes of Infectious Keratitis Caused by Achromobacter xylosoxidans.

PURPOSE: Reports on Achromobacter xylosoxidans ocular infections are increasing, drawing attention to its emerging role in infectious keratitis. The purpose of this study is to report the clinical features, antibiotic sensitivities, and visual outcomes of infectious keratitis secondary to Achromobacter xylosoxidans. METHODS: A microbiology database and clinical chart review was performed in all patients diagnosed with A. xylosoxidans keratitis at the Bascom Palmer Eye Institute between the years 1987 and 2014. Initial presentation, antimicrobial susceptibilities, minimum inhibitory concentrations (MICs), treatment course, and outcomes were recorded. RESULTS: Twenty-eight patients were identified. The main risk factors were corneal graft (n = 8, 28.6%) and contact lens wear (n = 8, 28.6%). On presentation, visual acuity was 20/100 or worse in 20 (71.2%) patients. Hypopyon was present in 7 (25.0%) patients. In most cases, topical fluoroquinolones or tobramycin were the initial treatment, often accompanied by vancomycin. High susceptibility rates were found for piperacillin [100%, minimum inhibitory concentration for 90% of isolates (MIC90) = 8] and ticarcillin (100%, MIC90 = 16). Low susceptibility rates were documented for ciprofloxacin (46.7%, MIC90 = 8), tobramycin (26.7%, MIC90 = 16), and gentamicin (20%, MIC90 = 16). One (3.6%) patient suffered endophthalmitis. Six (21.4%) patients underwent therapeutic penetrating keratoplasty, and 2 (7.1%) patients had conjunctival flap surgery. Visual acuity at final follow-up was 20/100 or worse in 16 (57.1%) patients. CONCLUSIONS: Infectious keratitis caused by A. xylosoxidans is associated with poor visual outcomes. Fluoroquinolones and aminoglycosides are not appropriate treatments for these ocular infections. Further studies are needed to define the clinical application of compound piperacillin and ticarcillin eye drops.

Comparative antifungal susceptibility analysis of Candida albicans versus non-albicans Candida corneal isolates.

PURPOSE: To compare the in vitro activity of topical amphotericin B (AMB), natamycin, voriconazole, and fluconazole against human corneal isolates of Candida sp. for guidance in the treatment of Candida keratitis. METHODS: Sixty-eight Candida isolates (37 albicans and 31 non-albicans isolates) recovered from corneal scrapings submitted to rule out microbial keratitis, during the years 2005 to 2011, at the Bascom Palmer Eye Institute, were examined in this study. Corneal isolates were cultured on fungal agars for 48 hours. Each yeast isolate was dispensed into 4 microtiter wells, each containing 100 mL of commercial (natamycin 5%) or compounded (AMB 0.15%, voriconazole 1%, and fluconazole 0.2%) antifungal medications. A comparison of growth patterns was conducted. RESULTS: One hundred percent of the samples showed growth inhibition after treatment exposure with AMB or natamycin. The isolates treated with voriconazole demonstrated an 85% inhibition rate overall, with the Candida albicans samples showing a 77% inhibition rate and the non-albicans sp. a 93% inhibition rate. In the fluconazole group, there was only a 19.6% inhibition rate noted, with a 7.7% inhibition rate observed in the C. albicans group versus a 30% inhibition rate in the non-albicans group. CONCLUSIONS: AMB 0.2% and natamycin 5% have equal effectiveness and full inhibition against Candida keratitis isolates. Fluconazole 0.2% is not the drug of choice in both C. albicans and non-albicans keratitis. Voriconazole 1% may need a stronger concentration for higher effectiveness, but potentially may be helpful as a second agent in the treatment of Candida keratitis.