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

Fusarium spp. in Human Disease: Exploring the Boundaries between Commensalism and Pathogenesis

Fusarium is a large fungal genus that is widely distributed in the environment, mostly known for its plant pathogenicity. Rarely, it is involved in human pathology, where the type of infection caused is highly dependent upon the portal of entry and the immune status of the host. The study at hand aims to summarize routine methods used in diagnosing such infections as well as more advanced molecular diagnostic methods, techniques that can play a huge role in differentiating between colonization and infection when trying to decide the therapeutic outcome. Consequently, to further support our findings, two different strains (one isolated from corneal scrapings and one isolated from purulent discharge) were analyzed in a clinical context and thoroughly tested using classical and modern diagnostic methods: identification by macroscopical and microscopical examinations of the culture and mass spectrometry, completed by molecular methods such as PCR for trichothecene and ERIC-PCR for genetic fingerprinting. Isolation of a clinically relevant Fusarium spp. from a sample still remains a diagnostic challenge for both the clinician and the microbiologist, because differentiating between colonization and infection is very strenuous, but can make a difference in the treatment that is administered to the patient.

Fungal keratitis: Mechanisms of infection and management strategies

Fungal corneal ulcers are an uncommon, yet challenging, cause of vision loss. In the United States, geographic location appears to dictate not only the incidence of fungal ulcers, but also the fungal genera most encountered. These patterns of infection can be linked to environmental factors and individual characteristics of fungal organisms. Successful management of fungal ulcers is dependent on an early diagnosis. New diagnostic modalities like confocal microscopy and polymerase chain reaction are being increasingly used to detect and identify infectious organisms. Several novel therapies, including crosslinking and light therapy, are currently being tested as alternatives to conventional antifungal medications. We explore the biology of Candida, Fusarium, and Aspergillus, the three most common genera of fungi causing corneal ulcers in the United States and discuss current treatment regimens for the management of fungal keratitis.

American Academy of Optometry Microbial Keratitis Think Tank

SIGNIFICANCE

Think Tank 2019 affirmed that the rate of infection associated with contact lenses has not changed in several decades. Also, there is a trend toward more serious infections associated with Acanthamoeba and fungi. The growing use of contact lenses in children demands our attention with surveillance and case-control studies.

PURPOSE

The American Academy of Optometry (AAO) gathered researchers and key opinion leaders from around the world to discuss contact lens-associated microbial keratitis at the 2019 AAO Annual Meeting.

METHODS

Experts presented within four sessions. Session 1 covered the epidemiology of microbial keratitis, pathogenesis of Pseudomonas aeruginosa, and the role of lens care systems and storage cases in corneal disease. Session 2 covered nonbacterial forms of keratitis in contact lens wearers. Session 3 covered future needs, challenges, and research questions in relation to microbial keratitis in youth and myopia control, microbiome, antimicrobial surfaces, and genetic susceptibility. Session 4 covered compliance and communication imperatives.

RESULTS

The absolute rate of microbial keratitis has remained very consistent for three decades despite new technologies, and extended wear significantly increases the risk. Improved oxygen delivery afforded by silicone hydrogel lenses has not impacted the rates, and although the introduction of daily disposable lenses has minimized the risk of severe disease, there is no consistent evidence that they have altered the overall rate of microbial keratitis. Overnight orthokeratology lenses may increase the risk of microbial keratitis, especially secondary to Acanthamoeba, in children. Compliance remains a concern and a significant risk factor for disease. New insights into host microbiome and genetic susceptibility may uncover new theories. More studies such as case-control designs suited for rare diseases and registries are needed.

CONCLUSIONS

The first annual AAO Think Tank acknowledged that the risk of microbial keratitis has not decreased over decades, despite innovation. Important questions and research directions remain.

Dual effect of blue light on Fusariumsolani clinical corneal isolates in vitro

The purpose was to investigate the effect of daylight-intensity blue light on F. solani isolated from the cornea of patients with fungal keratitis. Spore suspensions of 5 F. solani strains (one standard strain and 4 clinical corneal isolates) were prepared in 6-well plates. Blue light groups were irradiated by a light-emitting diode (LED) device with a peak wavelength of 454 nm at 0.5 mW/cm² for 0 to 48 h, while the controls were maintained in darkness. Hyphal morphology in the 6-well plates was recorded at 0, 12, 24, 36, 48 h. One hundred microliters of spore suspensions of each strain at these five time points was transferred to SGA plates and cultured for 36 h at 29 °C; the number of colonies formed was counted as a measure of conidia quality and viability. Blue light has dual effects on F. solani. The hyphal length of F. solani exposed to blue light was significantly shorter than that of the control (P < 0.01), indicating that fungal growth was inhibited. Meanwhile, instead of reducing the viability of spores, blue light significantly enhanced the conidia quality and viability after at least 24 h irradiation. Daylight-intensity blue light exposure will inhibit the hyphal growth of F. solani but promote conidiation, which would be more harmful to fungal keratitis. Eliminating the influence of blue light for these patients should be taken into account.