Antimicrobial susceptibility of Fusarium, Aspergillus, and other filamentous fungi isolated from keratitis

Clinical utility of voriconazole eye drops in ophthalmic fungal keratitis

Fungal keratitis is one of the major causes of ophthalmic mycosis and is difficult to treat. The range of common antifungal agents available for fungal keratitis remains inadequate and is generally associated with poor clinical outcomes. Voriconazole is a new generation triazole antifungal agent. Only marketed in systemic formulation and, with broad-spectrum activity and high intraocular penetration, voriconazole has demonstrated effectiveness against fungal keratitis. Systemic voriconazole, however, is not without side effects and is costly. Voriconazole eye drops have been prepared extemporaneously and used for the treatment of ophthalmic fungal keratitis. The current article sought to review the literature for evidence related to the effectiveness and safety of topical voriconazole and its corneal penetration into the aqueous humor of the eye. The voriconazole eye drops used are typically of 1% concentration, well tolerated by the eye, and are stable. Despite existing evidence to suggest that the eye drops are effective in the treatment of fungal keratitis, more studies are needed, especially in relation to using the eye drops as first-line and stand-alone treatment, preparation of higher concentrations, and optimal dosing frequency.

Practice patterns in the management of fungal corneal ulcers

PURPOSE

The purpose of this study was to determine the practice patterns of ophthalmologists in the management of fungal corneal ulcers.

METHODS

In December 2007, a survey of 13 questions addressing the actual and preferred treatment of fungal ulcers was sent to the kera-net e-mail listserv facilitated by the Cornea Society.

RESULTS

Ninety-two respondents from North America, South America, Asia, Europe, and Australia participated by completing the electronic questionnaire. Natamycin was the most commonly used topical treatment for ulcers caused by filamentous fungi (96%) followed by amphotericin (75%) and voriconazole (63%). However, voriconazole was most often listed as the preferred topical treatment in an ideal world (79%) compared with 55% for natamycin. Approximately half of the respondents use combination topical therapy (56%) and the remainder monotherapy. The majority of respondents rescrape the epithelium at some time during the course of treatment, but the frequency of rescraping varied among the different topical treatments. The most common reasons cited for not using their preferred treatment were cost and a desire for further evidence to support preferred treatment.

CONCLUSION

There appears to be significant variation in the management of fungal corneal ulcers. Although natamycin was the most commonly used treatment for ulcers caused by filamentous fungi, voriconazole was the most preferred as the ideal treatment. These results highlight the need for more evidence regarding the efficacy of the newer topical antifungals.

In vitro activity of thimerosal against ocular pathogenic fungi

The in vitro activity of thimerosal versus those of amphotericin B and natamycin was assessed against 244 ocular fungal isolates. The activity of thimerosal against Fusarium spp., Aspergillus spp., and Alternaria alternata was 256 times, 512 times, and 128 times, respectively, greater than that of natamycin and 64 times, 32 times, and 32 times, respectively, greater than that of amphotericin B. Thimerosal's antifungal activity was significantly superior to those of amphotericin B and natamycin against ocular pathogenic fungi in vitro.

In vitro evaluation of combination antifungal activity against Fusarium species isolated from ocular tissues of keratomycosis patients

PURPOSE

To determine the minimum inhibitory concentrations (MICs) of five antifungal agents against Fusarium species isolated from ocular tissues and to evaluate anti-Fusarium species activities of eight combination treatments in vitro.

DESIGN

Experimental research.

METHODS

Thirty-eight isolates of Fusarium species were collected from patients' ocular tissues and were cultured in vitro. The MICs of natamycin, terbinafine, itraconazole fluconazole, and amphotericin B, either used alone or combined with other compounds, were evaluated by checkerboard microdilution technique based on the Clinical Laboratory Standards Institute proposed standard. The interactions were assessed using the Fractional Inhibitory Concentration Index model.

RESULTS

In the MIC study, the MIC(90) of each drug used alone were: natamycin, 16 microg/ml; terbinafine, 8 microg/ml; itraconazole, >16 microg/ml; fluconazole, >64 microg/ml; and amphotericin B, 4 microg/ml. Synergism was obtained in the amphotericin B plus terbinafine (81.6%) group and in the amphotericin B plus itraconazole (84.2%) group, with an obviously decreased MIC value of amphotericin B. Antagonism was shown in the natamycin plus azoles and in the natamycin plus terbinafine groups in 52.6% to 60.5% of Fusarium species strains.

CONCLUSIONS

Amphotericin B plus terbinafine or itraconazole demonstrated more effective anti-Fusarium species activity than single-use in vitro treatment, which implies that these combinations may be helpful in treating fungal keratitis. The combinations of natamycin plus azoles or natamycin plus terbinafine were not satisfactory and can be avoided. Further in vivo studies are needed to elucidate the potential usefulness of these combination therapies.

Activity of antibiotics against Fusarium and Aspergillus

BACKGROUND/AIMS

To study the susceptibility of Fusarium and Aspergillus isolated from keratitis to amoxicillin, cefazolin, chloramphenicol, moxifloxacin, tobramycin and benzalkonium chloride (BAK).

METHODS

10 isolates of Fusarium and 10 isolates of Aspergillus from cases of fungal keratitis at Aravind Eye Hospital in South India were tested using microbroth dilution for susceptibility to amoxicillin, cefazolin, chloramphenicol, moxifloxacin, tobramycin and BAK. The minimum inhibitory concentration (MIC) median and 90th percentile were determined.

RESULTS

BAK had the lowest MIC for both Fusarium and Aspergillus. Chloramphenicol had activity against both Fusarium and Aspergillus, while moxifloxacin and tobramycin had activity against Fusarium but not Aspergillus.

CONCLUSIONS

The susceptibility of Fusarium to tobramycin, moxifloxacin, chloramphenicol and BAK and of Aspergillus to chloramphenicol and BAK may explain anecdotal reports of fungal ulcers that improved with antibiotic treatment alone. While some of the MICs of antibiotics and BAK are lower than the typically prescribed concentrations, they are not in the range of antifungal agents such as voriconazole, natamycin and amphotericin B. Antibiotics may, however, have a modest effect on Fusarium and Aspergillus when used as initial treatment prior to identification of the pathological organism.

Voriconazole for the treatment of refractory Aspergillus fumigatus keratitis

We report a case of Aspergillus fumigatus keratitis in a 53-year-old, well-controlled diabetic female who did not respond to standard antifungal treatment. She was started on topical natamycin eye drops, but the infiltrate continued to progress. Topical amphotericin B and systemic ketoconazole was added, however, there was no response and the infiltrate increased further. She was then switched to topical and systemic voriconazole. Steady resolution of the infiltrate was noted within 2 weeks of therapy.

Determination of in vitro susceptibility of ocular Fusarium spp. isolates from keratitis cases and comparison of Clinical and Laboratory Standards Institute M38-A2 and E test methods

We evaluated the susceptibility of 85 Fusarium spp. isolates from cases of fungal keratitis with 8 antifungal drugs using the standard Clinical and Laboratory Standards Institute broth microdilution and E test methods. Members of the Fusarium solani species complex showed consistently higher MICs to the triazole drugs itraconazole, voriconazole, and posaconazole than did members of other species complexes (Fusarium oxysporum and other minor species). High MICs to amphotericin B, natamycin, and echinocandins were consistently obtained with no discrimination based on species or method. Further work is required to determine any potential correlation between MIC and clinical outcome in keratitis.

In vitro natamycin susceptibility of ocular isolates of Fusarium and Aspergillus species: comparison of commercially formulated natamycin eye drops to pharmaceutical-grade powder

The Clinical and Laboratory Standards Institute susceptibility method prohibits the use of pharmacy preparations, but obtaining pure powders is difficult. The activity of natamycin against isolates of Aspergillus and Fusarium species isolated from keratitis was assessed by using both powder and pharmacy eye drop preparations. Eye drop preparations may be a viable option for testing natamycin activity.

Antifungal susceptibility for common pathogens of fungal keratitis in Shandong Province, China

PURPOSE

To analyze common pathogens of fungal keratitis and results of antifungal drug sensitivity test in Shandong Province, China and provide guidance for appropriate choice of antifungal drugs in clinic.

DESIGN

Retrospective, noncomparative study.

METHODS

The pathogens isolated from 674 fungal keratitis patients between January 1, 2001 and December 31, 2006 were cultured and identified in Shandong Eye Institute, of which some common strains were tested for sensitivity to antifungal drugs.

RESULTS

Fungi were positively cultured in 549 (81.5%) patients, in which the dominating pathogen was genus Fusarium (77.6%), with F. solani (37.3%), F. moniliforme (30.0%), and F. oxysporum (27.9%) being common species; Fusarium was mostly sensitive to natamycin, next to amphotericin B, and then to terbinafin. The second common pathogen was genus Aspergillus (10.8%), in which the main species were A. flavus (49.2%) and A. fumigatus (35.6%); Aspergillus was mostly sensitive to natamycin, next to terbinafin, and then to amphotericin B. Relatively, both Fusarium and Aspergillus were insensitive to ketoconazole, miconazole, itraconazole, fluconazole, and fluorocytosine.

CONCLUSIONS

Fusarium is the most common pathogen of fungal keratitis, followed by Aspergillus, in Shandong Province, China. Natamycin is still the first choice in the treatment of hyphomycetic keratitis. Fusarium and Aspergillus are also sensitive to amphotericin B and terbinafin. Early diagnosis and treatments are vital to good prognosis in the treatment of fungal keratitis.

[Purulent corneal melting secondary to multidrug-resistant Fusarium oxysporum aggravated by topical corticosteroid therapy]

Keratomycosis is a rare sight-threatening infection of the cornea. Predisposing factors in its pathogenesis are corneal trauma, mostly of plant origin, contact lenses, and overuse of topical corticosteroids. We report a case of a 44-year-old woman, with no ophthalmologic history, who developed severe keratitis 7 days after beginning topical therapy with a corticosteroid and antibiotic. Microbiological analysis revealed Fusarium oxysporum keratitis. Despite aggressive antifungal therapy with Voriconazole and Amphotericin B, she required a penetrating keratoplasty for impending corneal perforation. A second keratoplasty was performed because of corneal-transplant rejection after 6 months. There was no recurrence of Fusarium infection.

Exogenous fungal endophthalmitis: microbiology and clinical outcomes

OBJECTIVE

To report the fungal isolates, treatment strategies, and clinical outcomes for a large series of patients with exogenous fungal endophthalmitis.

DESIGN

Retrospective, single institution, consecutive case series.

PARTICIPANTS

All patients treated at Bascom Palmer Eye Institute between January 1, 1990, and June 30, 2006, for culture-proven exogenous fungal endophthalmitis.

METHODS

Microbiologic and medical records were reviewed for all patients with intraocular cultures positive for fungal organisms and clinically diagnosed exogenous endophthalmitis.

MAIN OUTCOME MEASURES

Fungal isolates, treatment strategies, visual acuity, and rate of enucleation.

RESULTS

Culture-positive exogenous fungal endophthalmitis occurred in 41 eyes, including 18 cases (44%) associated with fungal keratitis, 10 cases (24%) occurring after penetrating ocular trauma, and 13 cases (32%) after intraocular surgery. Filamentous fungi (molds) accounted for 35 cases (85%), and Candida species (yeasts) accounted for 6 cases (15%). Although most keratitis cases were caused by Fusarium (13 of 18; 72%), Aspergillus was the most common isolate in postoperative cases (5 of 13; 38%). Open-globe cases were caused by a broader spectrum of fungi. As initial treatment, 30 (73%) patients received intraocular amphotericin B, but at least 3 antifungal agents were used in 24 (59%) cases. At least 1 pars plana vitrectomy was performed in 25 (61%) eyes, and 29 (71%) eyes underwent 3 or more procedures, including surgeries and intraocular injections. Although a final vision of 20/400 or better was achieved in 22 (54%) eyes, all but 1 of these were either in the keratitis (11 of 18) or the postoperative (10 of 13) groups. Conversely, although 10 (24%) of 41 eyes were enucleated, 7 of these were among the open-globe patients.

CONCLUSIONS

This report highlights the differences between the clinical categories of exogenous fungal endophthalmitis. Although 85% of all cases were caused by molds, most commonly Fusarium and Aspergillus, the most common fungal genera varied by clinical category. Amphotericin B was the most commonly used antifungal agent, but most cases were treated with at least 3 different antifungal agents. Final visual outcomes were variable, with the open-globe-associated patients having the poorest outcomes. Overall, 44% of patients achieved a final visual acuity of 20/80 or better.