Differential antimicrobial extract activity of Graviola (Annona muricata) on gram positive and gram- negative antibiotic-resistant bacteria

New agents are needed with the increasing prevalence of multidrug-resistant (MDR) bacteria. Identification of plants with activity against MDR bacteria is of increasing importance. The antimicrobial activity of commercially available Graviola preparations against 38 clinical and laboratory isolates, representing MDR and drug-sensitive Gram positive and Gram negative bacteria, was measured by broth microdilution. Commercially Graviola fruit, as well as leaves/stems preparations, exhibited both inhibitory and cidal activity. However, the fruit preparation showed significantly less activity than the leaves/stems preparation. The Graviola leaves/stems preparation activity titer ranged from 1:4 to 1:16 against MDR Gram positive and Gram negative bacteria; including methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase (ESBL) Escherichia coli, Acinetobacter baumannii, and Klebsiella pneumoniae carbapenemase (KPC). However, the preparation had no effect on Lactobacillus. In addition, further extractions of the leaves/stems were tested against MRSA and MSSA in an in-vitro biofilm wound infection model. The polar extracts of the stems/leaves exhibited the highest bactericidal activity in preventing and inhibiting biofilm formation. Thus, Graviola leaves/stems extracts showed differential activity for phytochemical utility against multidrug-resistant bacteria.