| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1145-1 | ||||
Resumo:Currently there is concern about growing antibiotic resistance of clinical and agriculturally important pathogens. The World Health Organisation (WHO) published a list with critical, high and medium levels for bacterial pathogens that should be prioritised for research and development of new drugs. The Pantanal biome is known as a biodiverse repository of endophytes that, specifically in association with medicinal plants, have antimicrobial potential. Previous studies of Vochysia divergens endophytome (a medicinal tree of the South Mato Grosso Pantanal) performed by the research group of the Laboratory of Bioprospecting and Molecular Genetics of Microorganisms (BioGeMM) revealed a dominance of the Diaporthe genus, known producers of bioactive secondary metabolites. The type strain of the endophytic fungus Diaporthe vochysiae is reported to produce the carboxamides vochysamides A and B, and the latter was described to be active against Klebsiella pneumoniae carbapenemase-producing (KPC). There are in the NAPI CMRP Taxonline collection 55 other D. vochysiae strains of diverse genetics and macromorphology, which could be potential producers of new bioactive secondary metabolites. In this sense, the goal of the present study was to test whether the previously observed diversity within D. vochysiae extends to the bioactivity of strains’ secondary metabolites present in extracts. Extracts were produced in malt extract liquid medium with ten-day fermentation period and XAD-16 resin for secondary metabolite adsorption, washed with methanol. Bioactivity was assessed via minimum inhibitory (MIC) and bactericidal (MBC) concentration assays against gram positive Staphylococcus aureus methicillin resistant (MRSA, WHO’s high priority) and the gram negative KPC and A. baumannii (WHO’s critical priority) as well as mycelial growth inhibition assay against the phytopathogen Colletotrichum abscissum, causal agent of postbloom fruit drop (PFC) in Citrus spp. in Brazil. For MRSA, MIC and MBC values ranged from 3.125 mg/mL to 0.004 mg/mL and from greater than 3.125 mg/mL to 0.116 mg/mL, respectively. Against A. baumannii, only one isolate had an extract MBC of 3.125 mg/mL, and no extracts were lethal to KPC at up to 3.125 mg/mL. One extract inhibited 77.74% of C. abscissum mycelial growth, another five inhibited more than 20% but less than 40%, and, surprisingly, six of the extracts promoted growth of up to 5.96% compared to the negative control. The isolates show diverse levels of extract activity against MRSA whereas most were homogeneously inactive towards the gram-negative bacteria used in this study, showing a specificity against gram positive bacteria which may be desirable in drug discovery settings. The isolates show very diverse levels of extract activity against C. abscissum, with actions ranging from 5.96% growth promotion to 77.74% inhibition. The results show a potential of new compound action discovery which helps to advance the goals set by the WHO's list of priority pathogens. Further investigations will seek to characterise the chemical profile of the extracts and possibly compare the chemical and bioaction profiles to the phylogenetic placement of the isolates, helping to determine whether secondary metabolite production correlates with their genetic diversity. Palavras-chave: Diaporthe, bioprospecting, Colletotrichum abscissum, MRSA, Acinetobacter baumannii Agência de fomento:CAPES | |||||