Interaction between terpenes and penicillin on bacterial strains resistant to beta-lactam antibiotics

INTRODUCTION A variety of medicinal plants possess the capacity to synthesize aromatic compounds called essential oils, which are obtained either by hydrodistillation or by expression. These oils are complex mixtures of organic compounds, including monoterpenes and sesquiterpenes. Beneficial properties for human and animal health have been attributed to these compounds such as: antitumoral activity, antioxidant efficiency and antimicrobial activity (Zygadlo and Juliani, 2001). The antimicrobial activity of some essential oils from some native species of Argentina was tested. Good antimicrobial activity was observed in Gram positive bacteria while reduced inhibitory activity was observed in Gram-negative bacteria, particularly on Pseudomona aeruginosa. The indiscriminate use of antibiotics gave rise to the appearance of multiresistant strains, e.g., methicillin resistant Staphylococcus aureus (MRSA), which at the present time is one of the main causal agents of intrahospitalarial infections in the world. There are also strains naturally resistant to these substances, such as Gramnegative bacteria. In this work we want to study the influence of a terpenic compound on the mode of action of an antibiotic of conventional use, e.g., penicillin, which is ineffective against MRSA, and is not specific for Gram-negative strains, such as Escherichia coli. The combination of terpenes and antibiotics could result in a sinergistic effect in order to eliminate this microorganism and/or other natural resistant ones, such as Gram-negative bacteria, in particular P. aeruginosa.