Antimicrobial and antibiofilm potential of Morus macroura against Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae is a respiratory pathogen that causes infectious disease such pneumonia, Otitis media, meningitis. Despite the availability of pneumococcal conjugated vaccine, the prevalence and infection of bacteria is high due the serotypes not covered in vaccine, antibiotic-resistant strains, and biofilm mode of growth. Therefore, it is essential to continue research for novel antibiofilm agents. Here, we investigated the antimicrobial and antibiofilm potential of Morus macroura extracts against S. pneumoniae. The biofilm biomass was detected by microplate-static model, the viable bacteria were detected by cfu counts, the morphology of biofilm were analyzed using live/dead staining and confocal microscopy, and the bioactive compounds were detected by Gas Chromatography-Mass Spectrometry (GC-MS). The Minimum Inhibitory Concentration of methanolic extract against S. pneumoniae was 256 μg/mL. At this concentration, the extract inhibited biofilm formation and eradicated 76% of pre-established biofilms. Time-kill experiments and confocal microscopy revealed bactericidal activity and disruption of bacterial cell membranes. The GC-MS analysis identified 25 bioactive compounds in the methanolic extract, with the maximum peak area for Neophytadiene, Linolenic acid methyl ester and phytol. The extract was not cytotoxic towards human nasal epithelial cells. These findings suggest that S. pneumoniae extract contain bioactive compounds that possess antibiofilm/antimicrobial potential, and can be explored to develop new antimicrobial agents.