Natamycin is a safe and efficient antimycotics which is widely used in food and medicine industry. The polyene macrolide compound, produced by several bacterial species of the genus Streptomyces, is synthesized by type Ⅰ polyketide synthases using acetyl-CoA, malonyl-CoA, and methylmalonyl-CoA as substrates. In this study, four pathways potentially responsible for the supply of the three precursors were evaluated to identify the effective precursor supply pathway which can support the overproduction of natamycin in Streptomyces gilvosporeus, a natamycin-producing wild-type strain. The results showed that over-expressing acetyl-CoA synthetase and methylmalonyl-CoA mutase increased the yield of natamycin by 44.19% and 20.51%, respectively, compared with the wild type strain under shake flask fermentation. Moreover, the yield of natamycin was increased by 66.29% compared with the wild-type strain by co-overexpression of acetyl-CoA synthetase and methylmalonyl-CoA mutase. The above findings will facilitate natamycin strain improvement as well as development of strains for producing other polyketide compounds.
Natamycin/metabolism* ; Methylmalonyl-CoA Mutase/metabolism* ; Acetyl Coenzyme A/metabolism* ; Streptomyces/genetics* ; Polyketide Synthases/metabolism*

Natamycin is a polyene macrolide antibiotics with strong and broad spectrum antifungal activity. It not only effectively inhibits the growth and reproduction of fungi, but also prevents the formation of some mycotoxins. Consequently, it has been approved for use as an antifungal food preservative in most countries, and is also widely used in agriculture and healthcare. Streptomyces natalensis and Streptomyces chatanoogensis are the main producers of natamycin. This review summarizes the biosynthesis and regulatory mechanism of natamycin, as well as the strategies for improving natamycin production. Moreover, the future perspectives on natamycin research are discussed.
Antifungal Agents/pharmacology* ; Fungi ; Natamycin ; Streptomyces

PURPOSE: To report a case of Paecilomyces lilacinus fungal keratitis after cataract surgery in a patient with chronic systemic and autoimmune disease who was treated with medical therapy and penetrating keratoplasty. CASE SUMMARY: A 72-year-old female was referred for decreased visual acuity and ocular pain in the left eye. She underwent cataract surgery in the left eye 1 month earlier and was treated for 2 weeks for corneal edema and stromal infiltration around the corneal suture. She had a chronic systemic disease with hypertension, hyperlipidemia, hepatitis C and rheumatoid arthritis. Suspecting infectious keratitis, the patient was instructed to stop applying topical and systemic steroids and use topical amphotericin B (0.15%) and moxifloxacin (0.5%). However, without improvement, amphotericin B (0.15%) and moxifloxacin (0.5%) were changed to natamycin (5%) and topical voriconazole (2%) and systemic voriconazole was added. However, her systemic status deteriorated and corneal melting developed, scleral graft implantation and amniotic membrane implantation were performed to prevent corneal perforation 6 weeks after the initial visit. Paecilomyces lilacinus was identified in culture at 7 weeks and penetrating keratoplasty was performed 12 weeks after the initial visit. After penetrating keratoplasty, corneal status was stable for 6 months and no signs of recurrence were observed. CONCLUSIONS: In a patient with Paecilomyces lilacinus fungal keratitis and chronic systemic and autoimmune disease, penetrating keratoplasty showed good prognosis when the disease was refractory to topical and systemic antifungal agents.
Aged ; Amnion ; Amphotericin B ; Antifungal Agents ; Arthritis, Rheumatoid ; Autoimmune Diseases* ; Cataract* ; Corneal Edema ; Corneal Perforation ; Female ; Freezing ; Hepatitis C ; Humans ; Hyperlipidemias ; Hypertension ; Keratitis* ; Keratoplasty, Penetrating ; Natamycin ; Paecilomyces* ; Prognosis ; Recurrence ; Steroids ; Sutures ; Transplants ; Visual Acuity ; Voriconazole

A 71-year-old man presented with pain in the left eye that revealed a 3x3 mm deep corneal stromal infiltrate, with a 2x2 mm epithelial defect. The patient started topical moxifloxacin, voriconazole 2%, and natamycin for 2 weeks. However, the treatment was not effective and the corneal infiltration worsened. Subsequently, the patient underwent therapeutic penetrating keratoplasty. Thick brown/gray mold colonies on Potato Corn Meal Tween 80 agar was isolated from excised corneal tissue and on slide culture many septated, and club-shaped ascospores were revealed. Histological findings also showed numerous hyphae scattered in corneal tissue. A. alternata colonies were confirmed by 18S rRNA sequencing. Intracameral voriconazole was injected every other day for 2 weeks to eliminate remaining fungi on the deep corneal stroma. The remaining corneal infiltration was improved one month after the injection. During 5 months postoperative follow up, the infection did not recurred. In conclusion, deep corneal infection of A. alternata was effectively treated with intracameral voriconazole injection.
Agar ; Aged ; Alternaria* ; Corneal Stroma ; Follow-Up Studies ; Fungi ; Humans ; Hyphae ; Keratitis* ; Keratoplasty, Penetrating ; Meals ; Natamycin ; Polysorbates ; Solanum tuberosum ; Zea mays

The afsRS(cla) global regulatory genes from Streptomyces clavuligerus activate the production of two antibiotics in Streptomyces lividans. In this study, we gained an increase of 38% in the production of natamycin (3.56 g/L) in an industrial strain Streptomyces gilvosporeus TZ1401 through the integration of pHL851 that bears the afsRS(cla) global regulatory genes into its genome. We discovered by quantitive real-time reverse transcription PCR (qRT-PCR) that the expression of 6 genes of the natamycin biosynthetic gene cluster were improved from 1.9 to 2.7 times. This suggests that afsRS(cla) improve the production of natamycin through increased transcription. This study provides a good example for applying afsRS(cla) in high yield breeding of industrial antibiotic producers.
Anti-Bacterial Agents ; biosynthesis ; Genes, Regulator ; Industrial Microbiology ; Multigene Family ; Natamycin ; biosynthesis ; Streptomyces ; genetics

PURPOSE: To report a case of Phoma glomerata keratitis occurring in recurrent herpes simplex keratitis cicatrix. CASE SUMMARY: A 63-year-old male patient was admitted to our hospital with complaints of abrupt visual deterioration and ocular pain in his left eye. He was treated for recurrent herpes simplex keratitis in the same eye 12 years prior. Because central desmatocele was observed as a result of advanced corneal stromal melting, Gram staining, Potassium Hydroxide (KOH) mount, and culture were performed in corneal scrape specimens. On microbiological evaluation, a Phoma species was detected and Phoma glomerata was diagnosed using DNA sequencing method. Two consecutive amniotic membrane transplantations were performed with topical antifungal agents. The lesion was not improved when using topical amphotericin B and natamycin eyedrops, thus fluconazole eyedrops were used additionally. The corneal infection was resolved with central thick opacification. CONCLUSIONS: In the present case, herpetic keratitis was the main underlying causative factor because the patient had no past history of trauma. When diverse appearances of keratitis occur in herpes simplex keratitis patients, clinicians need to consider the concurrence of fungal infection, especially Phoma glomerata, a rare fungal organism.
Amnion ; Amphotericin B ; Antifungal Agents ; Cicatrix* ; Fluconazole ; Freezing ; Herpes Simplex ; Humans ; Keratitis* ; Keratitis, Herpetic* ; Male ; Middle Aged ; Natamycin ; Ophthalmic Solutions ; Potassium ; Sequence Analysis, DNA

PURPOSE: To report a case of Beauveria bassiana keratitis that was confirmed by gene sequencing. CASE SUMMARY: A 70-year-old man presented to our hospital with complaints of ocular pain and deterioration of the visual acuity in his left eye after injury caused by a wood branch one week previously. Visual acuity in the left eye was 20/400 at the time of the first visit. Slit lamp examination showed a central 0.7 x 2.5-mm-sized epithelial defect surrounded by cellular infiltration in the stroma. Scraping of the corneal lesion for microbiological examinations was performed. Initial Gram stain, potassium hydroxide (KOH) mount, and culture were negative. However, fungal hyphae were observed on a KOH mount of the repeated corneal scraping specimen, and a Beauveria species was suspected based on the culture. Beauveria bassiana was confirmed using a MicroSEQ(R) D2 large-subunit ribosomal DNA fungal sequencing kit. Natamycin eye solution was initially instilled bihourly (every two hours), but the persistent epithelial defect and progressive stromal melting finally resulted in a descemetocele. Temporary and permanent amniotic membrane transplantations were performed, and amphotericin B eye solution was administered bihourly (every two hours). The ulcerous lesion gradually improved with no evidence of recurrence. CONCLUSIONS: Recently, cases of fungal keratitis have been increasing. Therefore, molecular diagnosis methods such as gene sequencing can be helpful in diagnosis and in improving the prognosis of fungal keratitis caused by rare fungi, as we found in this case.
Aged ; Amnion ; Amphotericin B ; Beauveria* ; Diagnosis ; DNA, Ribosomal ; Freezing ; Fungi ; Humans ; Hyphae ; Keratitis* ; Natamycin ; Potassium ; Prognosis ; Recurrence ; Ulcer ; Visual Acuity ; Wood

PURPOSE: To report a case of fungal keratitis caused by Drechslera species. CASE SUMMARY: A 77-year-old man visited our clinic complaining of left ocular pain and decrease of visual acuity for 1 week On slit-lamp examination, epithelial defect and stromal infiltration on the corneal center with numerous inflammatory cells in the anterior chamber were found. There was no improvement after routine antibiotic treatment. A corneal biopsy and culture were performed on the corneal lesion. The KOH smear study reported hyphae, thus the patient was treated with 0.25% amphotericin B, 0.2% fluconazole and 5% natamycin eye drops. A clinical improvement was observed on the corneal lesion and Drechslera species was identified by the culture study. CONCLUSIONS: The authors report an experience of fungal keratitis caused by Drechslera species.
Aged ; Amphotericin B ; Anterior Chamber ; Biopsy ; Fluconazole ; Humans ; Hyphae ; Keratitis ; Natamycin ; Ophthalmic Solutions ; Visual Acuity

We isolated a high efficient antifungal strain A02 from forest soil in a suburb of Beijing. The result of polyphasic taxonomy confirmed that strain A02 belongs to Streptomyces lydicus. The fermented broth of the strain presented a stable and strong inhibiting activity against many plant pathogenic fungi. The purpose of this study was to ascertain the substance base of the antifungal activity of strain A02. We extracted the antifungal metabolite of A02 by using column chromatography with X-5 macroporous resin and 100-200 mesh silica gel respectively, and then purified it by LC-9101 recycling preparative HPLC with a SP-120-15 column (JAIGEL-ODS-AP). An active compound with purity over 99.845% was finally obtained. The chemical structure of the active compound was determined with spectroscopy methods, including ultraviolet spectrometry, infrared spectrometry, high resolution mass spectrometry and nuclear magnetic resonance. According to the analysis results, we identified the active compound as a tetraene macrolide antibiotic with the molecular weight of 665, the molecular formula C33H47No3 and the same chemical structure as natamycin. Our research revealed a new biosynthetic function for S. lydicus to produce natamycin, and an expanding application field for natamycin to be used for the control of fungal plant diseases.
Antifungal Agents ; chemistry ; isolation & purification ; Natamycin ; analogs & derivatives ; Soil Microbiology ; Streptomyces ; chemistry ; isolation & purification ; metabolism

BACKGROUNDFungal keratitis is a rare but serious corneal disease that may result in loss of vision. The poor prognosis might be due to limited treatment option. This study aimed to evaluate the clinical efficacy of 0.25% terbinafine eye drops comparing with 5% natamycin suspension on fungal keratitis.

METHODSA retrospective clinical trial was performed on 90 patients presenting with direct smear and/or culture positive fungal keratitis at Beijing Tongren Hospital, Beijing, China from January 2006 to May 2008. Corneal ulcers were categorized as mild or severe. Forty-five patients were treated with topical terbinafine and the next 45 cases received topical natamycin hourly.

RESULTSFilamentous fungi were found in corneal scrapings among all 90 cases. Fungal cultures were positive in 64 patients (71%). Species of Fusarium and Aspergillus were the principal isolates. Forty (89%) patients showed favorable response to terbinafine, while forty-two (93%) patients exhibited favorable response to natamycin (P > 0.05). The mean course of treatment was significantly showed in the terbinafine treatment group than natamycin group ((26.5 +/- 11.2) days versus (19.3 +/- 6.4) days; P < 0.05). In terbinafine group, twenty patients with ulcers smaller than 4 mm had favorable outcome, while 20 of 25 patients with ulcers more than 4 mm in diameter had favorable response (P < 0.05). Twenty-seven patients with depth of infiltration less than half of stroma thickness had favorable response to terbinafine, while 13 of 18 patients with depth of infiltration more than half of stroma responded to terbinafine. This difference was statistically significant (P < 0.05).

CONCLUSIONSOur findings suggest that topical terbinafine is an effective antifungal drug for the management of filamentous mycotic keratitis, particularly in cases with smaller and shallower ulcers. Its mean duration of treatment was longer than natamycin.

Antifungal Agents ; therapeutic use ; Aspergillus ; isolation & purification ; physiology ; Fusarium ; isolation & purification ; physiology ; Humans ; Keratitis ; drug therapy ; microbiology ; Naphthalenes ; therapeutic use ; Natamycin ; therapeutic use ; Retrospective Studies ; Treatment Outcome