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The Scientific World Journal
Volume 2012 (2012), Article ID 158237, 7 pages
Research Article

In Vitro Synergistic Effect of Psidium guineense (Swartz) in Combination with Antimicrobial Agents against Methicillin-Resistant Staphylococcus aureus Strains

1Laboratório de Fisiologia e Bioquímica de Microorganismos, Departamento de Antibióticos, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil
2Laboratório de Farmacognosia, Departamento de Farmácia Universidade Federal de Pernambuco, Centro de Ciências da Saúde, 50670-901 Recife, PE, Brazil
3Department of Biochemistry, Kansas State University, 141 Chalmers Hall, Manhattan, KS 66506, USA

Received 31 October 2011; Accepted 26 December 2011

Academic Editors: W. A. Gebreyes and T. Hatano

Copyright © 2012 Tiago Gomes Fernandes et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The aim of this study was to evaluate the antimicrobial activity of aqueous extract of Psidium guineense Swartz (Araçá-do-campo) and five antimicrobials (ampicillin, amoxicillin/clavulanic acid, cefoxitin, ciprofloxacin, and meropenem) against twelve strains of Staphylococcus aureus with a resistant phenotype previously determined by the disk diffusion method. Four S. aureus strains showed resistance to all antimicrobial agents tested and were selected for the study of the interaction between aqueous extract of P. guineense and antimicrobial agents, by the checkerboard method. The criteria used to evaluate the synergistic activity were defined by the fractional inhibitory concentration index (FICI). All S. aureus strains were susceptible to P. guineense as determined by the microdilution method. The combination of the P. guineense extract with the antimicrobial agents resulted in an eight-fold reduction in the MIC of these agents, which showed a FICI ranging from 0.125 to 0.5, suggesting a synergistic interaction against methicillin-resistant Staphylococcus aureus (MRSA) strains. The combination of the aqueous extract of P. guineense with cefoxitin showed the lowest FICI values. This study demonstrated that the aqueous extract of P. guineense combined with beta lactamics antimicrobials, fluoroquinolones, and carbapenems, acts synergistically by inhibiting MRSA strains.