Medical management of Beauveria bassiana keratitis

Isolation of the entomopathogenic fungus Beauveria bassiana from a skin lesion in a wild Nikolsky's viper (Vipera berus nikolskii)

Mycotic lesions of the skin of snakes are often associated with the fungus Ophidiomyces ophiodiicola, but other pathogens can cause similar signs. A skin sample from a wild Nikolsky's viper (Vipera berus nikolskii) with dermal lesions was collected in eastern Ukraine. A pure fungal culture was obtained and identified using nucleotide sequence analysis as the entomopathogenic species Beauveria bassiana sensu lato. Although Beauveria spp are considered to be non-pathogenic in vertebrates, sporadic infections have been reported. This report highlights the need to explore various pathogens when diagnosing the cause of snake integumentary lesions.

Beauveria bassiana Keratitis: A Case Series and Review of Literature

BACKGROUND

Beauveria bassiana is a filamentous fungus commonly used as an insecticide that rarely causes keratitis.

METHODS

Patients affected by Beauveria bassiana keratitis were retrospectively recruited at San Raffaele Hospital (Milan, Italy) between 2020 and 2022. All subjects underwent comprehensive ophthalmic evaluation, including in vivo confocal microscopy (IVCM) and microbiologic examination of corneal scrapings. Beauveria bassiana was identified using 18S rDNA targeted PCR.

RESULTS

Four eyes of four patients (51 ± 8.8 years old) were evaluated. The main risk factors were soft contact lens wear (75%) and trauma with vegetative matter (50%). A superficial infiltrate was displayed in the majority of patients. Three cases (75%) showed hyphae on IVCM. All patients showed clinical improvement after topical antifungal therapy, although mostly through a combination of two antifungals (75%). One patient with a deeper infection required a systemic antifungal agent after one month of topical therapy. All cases required debridement to reduce the microbial load and enhance drug penetration. All patients experienced keratitis resolution following medical treatment (average: 3.3 months).

CONCLUSIONS

The identification of risk factors and the early diagnosis of Beauveria bassiana keratitis are fundamental in order to avoid its penetration in the deeper corneal stromal layers. Topical antifungal drugs, possibly accompanied by ulcer debridement, may be a successful treatment if instilled from the early phases of the disease.

General Limitations to Endophytic Entomopathogenic Fungi Use as Plant Growth Promoters, Pests and Pathogens Biocontrol Agents

The multiple roles of fungal entomopathogens in host plants' growth promotion, pest and pathogen management have drawn huge attention for investigation. Endophytic species are known to influence various activities of their associated host plants, and the endophyte-colonized plants have been demonstrated to gain huge benefits from these symbiotic associations. The potential application of fungal endophytes as alternative to inorganic fertilizers for crop improvement has often been proposed. Similarly, various strains of insect pathogenic fungi have been formulated for use as mycopesticides and have been suggested as long-term replacement for the synthetic pesticides that are commonly in use. The numerous concerns about the negative effects of synthetic chemical pesticides have also driven attention towards developing eco-friendly pest management techniques. However, several factors have been underlined to be militating the successful adoption of entomopathogenic fungi and fungal endophytes as plant promoting, pests and diseases control bio-agents. The difficulties in isolation and characterization of novel strains, negative effects of geographical location, vegetation type and human disturbance on fungal entomopathogens, are among the numerous setbacks that have been documented. Although, the latest advances in biotechnology and microbial studies have provided means of overcoming many of these problems. For instance, studies have suggested measures for mitigating the negative effects of biotic and abiotic stressors on entomopathogenic fungi in inundative application on the field, or when applied in the form of fungal endophytes. In spite of these efforts, more studies are needed to be done to achieve the goal of improving the overall effectiveness and increase in the level of acceptance of entomopathogenic fungi and their products as an integral part of the integrated pest management programs, as well as potential adoption as an alternative to inorganic fertilizers and pesticides.

Fungal keratitis caused by Beauveria bassiana: drug and temperature sensitivity profiles: a case report

BACKGROUND

Beauveria bassiana is an entomopathogenic fungus and is a rare cause of keratitis. We present a case of fungal keratitis caused by B. bassiana that was diagnosed by in vivo confocal microscopy and in vitro corneal cultures. In addition, we determined the temperature- and drug-sensitivities of the isolated strain of B. bassiana.

CASE PRESENTATION

A 59-year-old Japanese man with a 2-month history of keratitis was examined by slit-lamp biomicroscopy, in vivo confocal microscopy, and histology and cultures of corneal scrapings. The corneal scrapings were used to determine the minimal inhibitory concentrations of different antifungal drugs and also to determine the temperature-sensitivity. In vivo confocal microscopy and histological examinations showed filamentous fungal keratitis. The characteristics of the fungal growth indicated that the keratitis was caused by B. bassiana. The keratitis responded poorly to systemic and topical voriconazole and to natamycin ointment. However, it was resolved after changing the natamycin to micafungin combined with surgical debridement. The isolated strain was sensitive to itraconazole, miconazole, micafungin, voriconazole, and resistant to flucytosine and fluconazole. It was moderately sensitive to amphotericin B, and natamycin. After 7 days in culture, the isolate grew small white colonies at 25 °C, very small colonies at 35 °C and 37 °C.

CONCLUSION

The drug-sensitivity and temperature-sensitivity profiles of B. bassiana should be helpful in the treatment of B. bassiana keratitis. Therapeutic surgery may be helpful for mycotic keratitis poorly responsive to medical therapy alone.

A case of Beauveria bassiana keratitis confirmed by internal transcribed spacer and LSU rDNA D1-D2 sequencing

We describe a case of fungal keratitis due to Beauveria bassiana in a farmer with Fuchs' dystrophy, treated with amphotericin B. Surgery with penetrating keratoplasty was necessary to resolve the lesions. Susceptibility testing and molecular sequencing permitted the identification and treatment of this rare aetiological agent of invasive fungal disease.

Diversity of microbial species implicated in keratitis: a review

Background:

Microbial keratitis is an infectious disease of the cornea characterised by inflammation and is considered an ophthalmic emergency requiring immediate attention. While a variety of pathogenic microbes associated with microbial keratitis have been identified, a comprehensive review identifying the diversity of species has not been completed.

Methods:

A search of peer-reviewed publications including case reports and research articles reporting microorganims implicated in keratitis was conducted. Search engines including PubMed, Scopus and Web of Science with years ranging from 1950-2012 were used.

Results:

232 different species from 142 genera, representing 80 families were found to be implicated in microbial keratitis. Fungi exhibited the largest diversity with 144 species from 92 genera. In comparison, 77 species of bacteria from 42 genera, 12 species of protozoa from 4 genera and 4 types of virus were identified as the infectious agents. A comparison of their aetiologies shows reports of similarities between genera.

Conclusions:

The diversity of microbial species implicated in keratitis has not previously been reported and is considerably greater than suggested by incidence studies. Effective treatment is heavily reliant upon correct identification of the responsible microorganisms. Species identification, the risk factors associated with, and pathogenesis of microbial keratitis will allow the development of improved therapies. This review provides a resource for clinicians and researchers to assist in identification and readily source treatment information.

The characteristics of keratomycosis by Beauveria bassiana and its successful treatment with antimycotic agents

Clinical findings and treatment of keratomycosis caused by Beauveria bassiana, an entomopathogenic filamentous fungus, are described for an 80-year-old woman, who was referred to the hospital for ocular pain and redness on the 9th day after an ocular injury caused by the frame of her glasses. She had a long history of recurrent diabetic iritis and continuously used topical antibiotics and corticosteroids. At her first visit, a slit-lamp examination indicated a corneal ulcer confined within the superficial stromal layer, along with a slight infiltration and edema. Only a very few inflammatory cells were seen in the anterior chamber. Direct microscopic examination of corneal scrapings revealed septate fungal hyphae with zig-zag rachis and budding that was subsequently identified as B. bassiana by slide culture. Topical voriconazole with miconazole, pimaricin and oral itraconazole were effective and the lesion disappeared leaving only a mild scar at 2 months. The sensitivity of B. bassiana to various antimycotic agents was confirmed by broth microdilution, agar dilution with the Clinical Laboratory Standard Institute standard, and a disk method using topically applied concentrations. B. bassiana, which exhibits a characteristic appearance in smears and causes superficial keratomycosis, is sensitive to voriconazole with miconazole, pimaricin, and itraconazole.

Treatment Failure after Lamellar Keratoplasty for Fungal Keratitis

PURPOSE

To evaluate treatment failure after lamellar keratoplasty (LK) for fungal keratitis.

DESIGN

Retrospective, interventional case series.

PARTICIPANTS

Two hundred eighteen patients (218 eyes) with fungal keratitis who failed to respond to medical therapy and underwent LK at the Shandong Eye Institute between January 1998 and July 2005.

METHODS

Detailed medical history was obtained from each patient. Antifungal drugs were administered for at least 7 days before LK was performed. A trephine that was 0.5 mm larger in diameter than the fungal infection was used to create a lamellar incision to excise the ulcer. After treatment failure was observed after surgery, penetrating keratoplasty (PK) was performed. The distribution of risk factors for treatment failure was analyzed.

MAIN OUTCOME MEASURES

Clinical features and risk factors for treatment failure.

RESULTS

Seventeen patients (7.8%) experienced treatment failure within 2 weeks after LK, including 15 patients within 1 week. All cases of treatment failure displayed increasing local irritation and hyphal infiltration in the recipient LK bed and subsequently were cured by PK. A higher rate of inadequate treatment with LK was found in the cases with Aspergillus species, in those to whom glucocorticoids or immunosuppressants were administered, and in those with hypopyon or endothelial plaque before LK.

CONCLUSIONS

Treatment failure after LK for fungal keratitis can be reduced significantly with adept intraoperative skills. Aspergillus species, use of glucocorticoids or immunosuppressants, and presence of hypopyon or endothelial plaque before LK should be noted as major risk factors. Prompt recognition and management of failed LK with PK can achieve successful outcomes.

Recalcitrant Beauveria bassiana Keratitis

PURPOSE

To report the clinical, confocal microscopic, and histologic appearance of a case of Beauveria bassiana keratitis and response to medical therapy.

METHODS

A 58-year-old woman with a 1-month history of a recalcitrant contact lens-related corneal ulcer was evaluated by confocal microscopy and corneal scraping for histology and culture.

RESULTS

Confocal microscopy and histology revealed a filamentous fungal keratitis confirmed by culture as B. bassiana resistant to amphotericin B. The keratitis was unresponsive to multiple topical and systemic antifungals but resolved after the addition of oral posaconazole.

CONCLUSIONS

B. bassiana is a rare cause of keratitis that may show significant resistance to topical and systemic antifungals but was treated successfully with the addition of oral posaconazole to topical voriconazole. Confocal microscopy and corneal smears may be of benefit in identifying and directing therapy for this slow-growing fungus.

First case report of empyema caused by Beauveria bassiana

Infections with Beauveria bassiana are extremely rare in humans. A 51-year-old man was admitted to hospital with the diagnosis of lung adenocarcinoma. Thoracic wall resection with lobectomy was applied and empyema has developed after prolonged air leakage. B. bassiana was isolated in pleural fluid. The patient improved without antifungal therapy after thoracotomy with securing of air leakage.

Antifungal therapy for keratomycoses

Keratomycoses have recently emerged as an important cause of ocular morbidity, especially in third-world countries. Available antifungal agents are limited in their efficacy, due to limited penetration into the cornea, the fungistatic nature and the development of drug resistance. Effective usage of the available drugs is hampered by the inefficiency of currently available antibiotic sensitivity tests for fungal organisms. There is also limited knowledge regarding the ideal combination(s) of antifungal agents, including issues of synergism and antagonism. Despite these problems, recent publications indicate encouraging outcomes in the treatment of a large series of fungal keratitis. Advances include better drug formulations, new agents and novel methods of drug delivery into the eye. As our ability to deal with advanced fungal keratitis remains limited, the importance of early diagnosis has been stressed and molecular biological techniques may play an important role in the future. This article summarises the important new advances in these areas in the past 2 years and provides guidelines for the management of these serious corneal infections.

Disseminated Beauveria bassiana infection in a patient with acute lymphoblastic leukemia

We describe a case of disseminated Beauveria bassiana infection in a patient with acute lymphoblastic leukemia. Her infection was successfully treated with amphotericin B and itraconazole. B. bassiana is rarely reported as a human pathogen. It is commonly found in soil and because of its pathogenicity to many insect species is incorporated into several pesticides.

Allergens of the entomopathogenic fungus Beauveria bassiana

Background

Beauveria bassiana is an important entomopathogenic fungus currently under development as a bio-control agent for a variety of insect pests. Although reported to be non-toxic to vertebrates, the potential allergenicity of Beauveria species has not been widely studied.

Methods

IgE-reactivity studies were performed using sera from patients displaying mould hypersensitivity by immunoblot and immunoblot inhibition. Skin reactivity to B. bassiana extracts was measured using intradermal skin testing.

Results

Immunoblots of fungal extracts with pooled as well as individual sera showed a distribution of IgE reactive proteins present in B. bassiana crude extracts. Proteinase K digestion of extracts resulted in loss of IgE reactive epitopes, whereas EndoH and PNGaseF (glycosidase) treatments resulted in minor changes in IgE reactive banding patterns as determined by Western blots. Immunoblot inhibitions experiments showed complete loss of IgE-binding using self protein, and partial inhibition using extracts from common allergenic fungi including; Alternaria alternata, Aspergillus fumigatus, Cladosporium herbarum, Candida albicans, Epicoccum purpurascens, and Penicillium notatum. Several proteins including a strongly reactive band with an approximate molecular mass of 35 kDa was uninhibited by any of the tested extracts, and may represent B. bassiana specific allergens. Intradermal skin testing confirmed the in vitro results, demonstrating allergenic reactions in a number of individuals, including those who have had occupational exposure to B. bassiana.

Conclusions

Beauveria bassiana possesses numerous IgE reactive proteins, some of which are cross-reactive among allergens from other fungi. A strongly reactive potential B. bassiana specific allergen (35 kDa) was identified. Intradermal skin testing confirmed the allergenic potential of B. bassiana.

Current perspectives on ophthalmic mycoses

Fungi may infect the cornea, orbit and other ocular structures. Species of Fusarium, Aspergillus, Candida, dematiaceous fungi, and Scedosporium predominate. Diagnosis is aided by recognition of typical clinical features and by direct microscopic detection of fungi in scrapes, biopsy specimens, and other samples. Culture confirms the diagnosis. Histopathological, immunohistochemical, or DNA-based tests may also be needed. Pathogenesis involves agent (invasiveness, toxigenicity) and host factors. Specific antifungal therapy is instituted as soon as the diagnosis is made. Amphotericin B by various routes is the mainstay of treatment for life-threatening and severe ophthalmic mycoses. Topical natamycin is usually the first choice for filamentous fungal keratitis, and topical amphotericin B is the first choice for yeast keratitis. Increasingly, the triazoles itraconazole and fluconazole are being evaluated as therapeutic options in ophthalmic mycoses. Medical therapy alone does not usually suffice for invasive fungal orbital infections, scleritis, and keratitis due to Fusarium spp., Lasiodiplodia theobromae, and Pythium insidiosum. Surgical debridement is essential in orbital infections, while various surgical procedures may be required for other infections not responding to medical therapy. Corticosteroids are contraindicated in most ophthalmic mycoses; therefore, other methods are being sought to control inflammatory tissue damage. Fungal infections following ophthalmic surgical procedures, in patients with AIDS, and due to use of various ocular biomaterials are unique subsets of ophthalmic mycoses. Future research needs to focus on the development of rapid, species-specific diagnostic aids, broad-spectrum fungicidal compounds that are active by various routes, and therapeutic modalities which curtail the harmful effects of fungus- and host tissue-derived factors.

Lamellar keratoplasty for the treatment of fungal keratitis

PURPOSE

To determine the therapeutic value of lamellar keratoplasty (LKP) in the treatment of fungal keratitis not curable by antifungal chemotherapy.

METHODS

Fifty-five patients, in whom a diagnosis of fungal keratitis was confirmed by microscopic analysis of corneal scrapings or confocal microscopy, and who were not cured by topical and oral antifungal medication, were given LKP. After LKP, topical antifungal treatment was continued for 2 weeks with gradual tapering of the drugs. The excised recipient lamella was used for microbial culture and histopathologic examination.

RESULTS

Therapeutically beneficial results were achieved in 51 cases (92.7%) of the 55 LKPs that were performed. In these 51 cases, there was no recurrence of infection, and the resulting visual acuity ranged from 20/63 to 20/20. Patient follow-up ranged from 6 to 18 months. In four cases (7.3%), there was a recurrence of the fungal infection within 2 weeks of LKP. In these four patients, the infection was cured by performing a penetrating keratoplasty (PKP). Forty-six of the recipient lamellae were culture positive for fungi. Thirty-three of these cultures were identified as Fusarium, six as Aspergillus, three as Candida, one as Penicillium species, and in the other three cases, unidentified septate hyphae were noted. In the four cases of recurrent infection, microbiologic culture revealed three cases with Fusarium species and one case with Aspergillus species. Histopathologic analysis of periodic acid-Schiff (PAS)-stained tissue sections of donor lamellae revealed fungal filaments in all samples. Immune reactions to the lamellar grafts were not observed and the donor lamellae remained clear for the duration of follow-up.

CONCLUSION

Lamellar keratoplasty can be effective for treating fungal keratitis that is not cured by antifungal therapeutics. In addition, LKP can provide useful vision with few complications. Furthermore, corneal tissue used in LKP may be obtained more easily than healthy tissue used in PKP.

Treatment of fungal keratitis by penetrating keratoplasty

AIM

To study the use of penetrating keratoplasty (PKP) for the treatment of severe fungal keratitis that could not be cured by antifungal medication.

METHODS

A retrospective analysis of 108 cases of severe fungal keratitis in which PKP was performed served as the basis for this study. Fungal keratitis was diagnosed by KOH staining of corneal scrapings or by confocal microscopic imaging of the cornea. All patients received a combination of topical and oral antifungal medicines without steroids as the first course of therapy. Patients whose corneal infection was not cured or in whom the infection progressed during antifungal treatment were given a PKP. After surgery, the patients continued to receive antifungal therapy with gradual tapering of the dose over a 1-2 month period. Cyclosporine was used to prevent graft rejection beginning 2 weeks after PKP. Topical steroid only was administered to the patient whose donor graft was over 8.5 mm and with a heavy iris inflammation 2 weeks after PKP. The surgical specimens were used for microbiological evaluation and examined histopathologically. The patients were followed for 6-24 months after PKP. Graft rejection, clarity of the graft, visual acuity, and surgical complications were recorded.

RESULTS

Corneal grafts in 86 eyes (79.6%) remained clear during follow up. There was no recurrence of fungal infection and the visual acuity ranged from 40/200 to 20/20. Complications in some patients included recurrent fungal infection in eight eyes (7.4%), corneal graft rejection in 32 eyes (29.6%), secondary glaucoma in two eyes (1.9%), and five eyes (4.6%) developed cataracts. 98 of 108 of the recipient corneas had PAS positive fungal hyphae in tissue sections; 97 of 108 were culture positive for various fungi, including Fusarium (63), Aspergillus (14), Candida (9), Penicillium (4), and seven cases in which septate hyphae were seen but identification of the organism was not conclusive.

CONCLUSIONS

PKP is an effective treatment for fungal keratitis that does not respond to antifungal medication. Early surgical intervention before the disease becomes advanced is recommended. It is critical that the surgical procedure remove the infected tissue in its entirety in order to effect a cure.