RESUMO
Aim: To evaluate antimicrobial activity of extracellular metabolites (EMs) of endophytic fungal isolates (EFIs) from Azadirachta indica. Materials & methods: EFIs were identified by internal transcribed spacer (ITS) sequencing. Antimicrobial activity, and minimum inhibitor concentration (MIC) and minimum bactericidal concentration (MBC) were determined using agar diffusion and microdilution method, respectively. Results: Seventeen EFIs were isolated from different organs of A. indica. Eight of them were identified based on ITS sequencing. The EMs of EFIs inhibited the growth of six multidrug-resistant (MDR) bacterial superbugs and three phytopathogenic fungi. The MDR bacterial superbugs are resistant to six commercial antibiotics of different generations but susceptible to EMs of EFIs. The MIC (0.125-1.0 µg/µl), MBC (0.5-4.0 µg/µl) and minimum fungicidal concentration (1.0-4.0 µg/µl) of the EMs from EFIs are lower enough. Conclusion: The EMs of the EFIs have promising antimicrobial activity against MDR bacteria and phytopathogenic fungi.
Assuntos
Anti-Infecciosos/metabolismo , Azadirachta/microbiologia , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Endófitos/metabolismo , Fungos/metabolismo , Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , DNA Fúngico/genética , DNA Espaçador Ribossômico/genética , Endófitos/classificação , Endófitos/genética , Endófitos/isolamento & purificação , Fungos/classificação , Fungos/genética , Fungos/isolamento & purificação , Fusarium/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Oomicetos/efeitos dos fármacos , FilogeniaRESUMO
Antimicrobial resistance poses a threat in the treatment of infectious diseases in Bangladesh as well as in the world. Multidrug-resistant (MDR) Enterobacteriaceae, the most common cause of one such infectious disease, urinary tract infection (UTI), has contributed to the escalating problem of selecting empiric antibiotics against UTIs. The aim of this study was to investigate the presence of the efflux pump in MDR Escherichia coli isolates from UTI in the North-East region of Bangladesh, to isolate and characterize the AcrAB-TolC efflux pump genes of these locally isolated strains and to do mutation analysis of the efflux pump repressor AcrR gene to understand the AcrAB-TolC efflux pump mechanism. In the presence of omeprazole, an efflux pump inhibitor, every MDR E. coli isolate showed increased susceptibility to at least 1 of the 7 antibiotics investigated, indicating that efflux pump might be involved in their antibiotic resistance. Omeprazole decreased the minimum inhibitory concentration of every antibiotics being investigated by 2- to 8-fold. DNA and the deduced amino acid sequences of the polymerase chain reaction (PCR) products analyzed by bioinformatics tools revealed that the chromosomal AcrAB-TolC and AcrR genes were present in all MDR and antibiotic-susceptible E. coli isolates. However, the deduced amino acid sequences of the amplification refractory mutation system (ARMS) PCR product of the AcrR gene revealed that the substitution of arginine to cysteine at position 45 of AcrR was observed only in the MDR E. coli whose antibiotic susceptibility increased in the presence of omeprazole. Data reported herein support the notion that the increased antibiotic susceptibility of the MDR E. coli isolates in the presence of omeprazole might be due to efflux pump(s) inhibition and the AcrAB-TolC efflux pump might be a contributor to antibiotic resistance when the mutation of arginine to cysteine occurs at position 45 of AcrR.
