Searches for substances with antimicrobial activity are frequent, and medicinal plants have been considered interesting by some researchers since they are frequently used in popular medicine as remedies for many infectious diseases. The aim of this study was to verify the synergism between 13 antimicrobial drugs and 8 plant extracts -"guaco" (Mikania glomerata), guava (Psidium guajava), clove (Syzygium aromaticum), garlic (Allium sativum), lemongrass (Cymbopogon citratus), ginger (Zingiber officinale), "carqueja" (Baccharis trimera), and mint (Mentha piperita) -against Staphylococcus aureus strains, and for this purpose, the disk method was the antimicrobial susceptibility test performed. Petri dishes were prepared with or without dilution of plant extracts at sub-inhibitory concentrations in Mueller-Hinton Agar (MHA) In a constant attempt to improve their quality of life, men have used plants as source of food, shelter, clothing, medicine, cosmetics, and for seeking relief from hardship of life. Some plants are known as medicinal because they contain active substances that cause certain reactions, from relenting to the cure of diseases, on the human organism (Silva Junior et al. 1994). Knowledge on medicinal plants sometimes means the only therapeutic resource of some communities and ethnic groups (Di Stasi 1996); and their use, especially in South America, contributes significantly to primary health care (Holetz et al. 2002). Infectious diseases still represent an important cause of morbidity and mortality among humans, especially in developing countries. Even though pharmaceutical industries have produced a number of new antimicrobial drugs in the last years, resistance to these drugs by microorganisms has increased. In general, bacteria have the genetic ability to transmit and acquire resistance to drugs used as therapeutic agents (Nascimento et al. 2000).In vitro studies on plants used in traditional medicine have been carried out in the field of microbiology, especially on pathogenic bacterial growth; and some of these studies were about the antimicrobial activity of Mikania glomerata Spreng ("guaco") (Boyayan 2002, Holetz et al. 2002, Psidium guajava L (guava) (Gnan & Demello 1999, Jaiarj et al. 1999, Nascimento et al. 2000, Ahmad & Beg 2001, Abdelrahim et al. 2002, Holetz et al. 2002, Voravuthikunchai et al. 2004, Qadan et al. 2005, Syzygium
MATERIALS AND METHODSPlant samples -M. glomerata, P. guajava, B. trimera, M. piperita, and C. citratus samples were collected in 2004 from an experimental field of the School of Agronomical Sciences, Unesp, Botucatu, São Paulo, Brazil, and the voucher specimens were deposited at the Herbarium of the Department of Botany, Institute of Biosciences, Unesp. Their leaves were dried at 40 o C and triturated in a mechanical mill. A. sativum, S. aromaticum, and Z. officinale samples were obtained from the local commerce in the same year and were used in natura for the extracts preparation.
Preparation of plant extracts -Plant material, dried (M. glomerata, P. guajava, B. ...
