Hydroethanolic stem bark extract of Treculia africana Decne (Moraceae) shows antimicrobial resistance modulatory effects

Abstract

Antimicrobial resistance (AMR) poses a serious threat to humans in all countries of the world. This study investigated the antibacterial, anti-biofilm formation, efflux pump inhibition and resistance modulatory effects of hydroethanolic stem bark extract of Treculia africana Decne (Moraceae) so as to assess its usefulness in the fight against drug-resistant pathogens. Preliminary phytochemical screening of Treculia africana stem bark extract (TASBE) revealed the presence of saponins, glycosides, tannins, triterpenoids and coumarins. The TASBE demonstrated moderate antibacterial activity (MIC = 125 – 500 µg/mL) towards Gram-negative bacteria whilst it showed no activity (MIC > 500 µg/mL) against Gram-positive bacterial species at the highest dose used (500 µg/mL). The extract also exhibited effects against two mycobacterial species, M. aurum (MIC = 500 µg/mL) and M. smegmatis (MIC > 500 µg/mL). Furthermore, the extract exerted potent anti-biofilm formation activity in both M. aurum and M. smegmatis with percentage biofilm inhibition of 56.70 70 ± ± 2.31 % and 59.10 10 ± ± 2.89 % respectively. Additionally, substantial efflux pump inhibitory effects were demonstrated in both M. aurum and M. smegmatis. A combination of the extract with ciprofloxacin exhibited synergistic effect against P. aeruginosa and P. mirabilis and additive effect against E. coli whilst their effect on K. pneumoniae was indifferent. Similarly, TASBE with rifampicin exhibited synergistic activity towards M. smegmatis whilst the effect towards M. aurum was indifferent. This study provides data that could be used to support the traditional use of T. africana in treating gastrointestinal and respiratory tract infections and demonstrates the potential of the extract as a source of novel compounds for tackling antimicrobial resistance.