Amphotericin A

The antifungal agent amphotericin B (AmB) is a polyketide produced by Streptomyces nodosus. The synthetic precursors of the amphotericin macrolactone skeleton are acetyl-CoA, malonyl-CoA and methylmalonyl-CoA. The genome sequence of the wild type S. nodosus ATCC14899 revealed a type II polyketide synthase (PKS) competing for malonyl-CoA. The same competitive branch was sequenced and verified in a mutant named S. nodosus ZJB2016050 (S. nodosus N3) screened in our lab. The transcriptome of the secondary metabolic synthetic gene cluster comparisons suggested that type II PKS (PKS5) competition is a factor in low production. The deletion of the PKS5 gene led to the titer of AmB improved from 5.01 g/L to 6.32 g/L while the by-product amphotericin A (AmA) reduced from 0.51 g/L to 0.12 g/L. A sequence of genes including PKS amphA, acc1, mme and mcm were overexpressed in a ΔPKS5 mutant, resulting in improved production AmB from 5.01 g/L to 7.06 g/L in shake flasks at 96 h. The yield of AmB and AmA in a 5 L bioreactor at 144 h was 15.6 g/L and 0.36 g/L, respectively. The intracellular reducibility of the wild type, mutagenesis type and genetically engineered type were detected, which was first found to be related to the by-product AmA. The increment of skeleton biosynthesis may consume more NADPH and reduces AmphC ER5 domain reduction. This study can be implemented for other polyketides in industrial production.

Purpose: Second wave of COVID-19 pandemic was associated with an unprecedented rise in cases of mucormycosis, treatment of which has been challenging owing to the availability and side effects associated with amphotericin. Methods: All patients presenting with rhino-orbital cerebral mucormycosis (ROCM) following COVID-19 infection between April 2021 to June 2021 were included in this retrospective interventional study. Primary objective was to assess the clinical response with combination of intravenous liposomal amphotericin B (4-5 mg/kg/day) and saturated solution of potassium iodide (SSKI) given orally along with surgical debridement. Results: Twenty-five patients of ROCM were treated with the regimen. Mean age and fasting blood sugar levels were 53.48 years and 239.64 mg/dL respectively. All patients had history of intake of steroids with a mean daily dose of 86.39 mg of prednisolone equivalent. 88% of patients had a "proven" diagnosis of mucormycosis. Cultures were positive in 52% of patients with Rhizopus arrhizus as the predominant species. The mean daily dose of amphotericin received was 268 mg/day with a mean duration of 9.52 days. Mean daily dose of SSKI was 2.57 g. 21 patients (84%) had stabilization of disease at week 8 and achieved cure at the end of treatment whereas the mortality rate was 16%. Factors that significantly affected outcome were eye and central nervous system (CNS) involvement on presentation. Conclusion: SSKI, with its remarkably low cost and safety profile, makes it a potential adjuvant drug that may help achieve the twin benefits of shortened duration and dose of LAMB.

Amphotericin, as an important macrolide antibiotic, is synthesized by Streptomyces nodosus. A high-yield S. nodosus ZJB2016050 was obtained by mutagenesis in our lab with the advantages of high yield, short fermentation cycle and few by-products, which was more suitable for industrial production. The fermentation differences in 50-tons bioreactor between S. nodosus ATCC14899 and S. nodosus ZJB2016050 were compared. The amphotericin B (AmB) yield of S. nodosus ZJB2016050 was 9.73 mg/g at 96 h, which was 30% higher than that of S. nodosus ATCC14899. The by-product amphotericin A (AmA) production of S. nodosus ZJB2016050 was 78% lower than that of S. nodosus ATCC14899. By performing whole-genome sequencing of S. nodosus ZJB2016050 and comparative genome analysis with the wild-type S. nodosus ATCC14899, it was found that the two strains have high synteny, but each has a special gene fragment. The genes functions of fragment were identified in the amino acid transport and metabolism, carbohydrate metabolism and lipid transport and metabolism. The gene functions of SNP (single nucleotide polymorphism) genes were identified in amino acid transport and metabolism, carbohydrate metabolism, coenzyme metabolism and secondary metabolites biosynthesis. The difference in signal-regulation and transcription may be the main reason for the differences between these two strains. Three GntR family egulatory factors of S. nodosus ATCC14899 may reduce the synthesis of amphotericin. Based on the analysis of comparative genomes, the effects of corn oil in S. nodosus ATCC14899 and S. nodosus ZJB2016050 were also compared. The results showed that corn oil can promote the fermentation of S. nodosus ZJB2016050. The S. nodosus ZJB2016050 may degrade fatty acids faster, and the degraded acyl-coenzyme can be used to synthesize amphotericin. Supplementary information: The online version contains supplementary material available at 10.1007/s13205-021-02844-2.