A pharmaceutical composition for the treatment of multi-drug resistant infections includes an antimicrobial agent in combination the benzopyrano[3,4-b][1]benzopyran-12(6H)-one class of compound boeravinone B of Formula 1: The bio-efficacy of anti-infective drugs can be potentiated, when used in combination with boeravinone B. Boeravinone B can overcome the resistance or multi-drug resistance developed by bacteria against quinolone, mupirocin and macrolide class of anti-bacterial agents via inhibition of bacterial efflux pumps. Thus, the compositions can be used to treat or prevent drug-resistant bacterial diseases.