Antimicrobial evaluation of a methanol extract of Beauveria bassiana against pathogenic bacteria of nosocomial importance

Objective: The antimicrobial activity of a crude extract of B. bassiana and two fractions thereof against clinically important bacteria was evaluated. Methods: The mycelium of strain B. bassiana was soaked in methanol for a week, then it was evaporated in a rotovap at 45 degrees C applying a vacuum. The methanolic extract was passed through two mobile phases to obtain a fraction A and B. Fractions A, B and crude extract C were evaluated against the strains Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Salmonella tiphy, Pseudomonas aeruginosa and Acinetobacter baumannii with the plate microdilution technique. Results: In fraction A an antimicrobial effect against Salmonella typhi, Pseudomonas aeruginosa and Acinetobacter baumannii was observed, bacterial growth reached 70, 60 and 83% respectively. Fraction B caused an antimicrobial effect in Klebsiella pneumoniae, S. typhi, P. aeruginosa and A. baumannii with a bacterial growth of 62, 58, 41 and 7% respectively. And the crude extract did not cause growth inhibition in A. baumannii, but for the rest of the bacteria there was a growth of 56 to 88%. Conclusions: Beauveria bassiana is an entomopathogenic fungus that produces different metabolites with insecticidal, cytotoxic, antifungal, antibiotic and antiviral activity. This is the first study of the antimicrobial effects of a methanolic extract of the entomopathogenic fungus B. bassiana against bacterial strains of clinical importance.