In vitro interaction of certain antimicrobial agents in combination with plant extracts against some pathogenic bacterial strains

Objective To evaluate the in vitro interaction between methanolic extracts of Terminalia catappa (Combretaceae) (T. catappa) and Carica papaya (caricaceae) (C. papaya) leaves and certain known antimicrobial drugs like penicillin G (P), ampicillin (AMP), amoxyclav (AMC), cephalothin (CEP), polymyxin B (PB), rifampicin (RIF), amikacin (AK), nilidixic acid (NA), gentamicin (GEN), chloramphenicol (C), ofloxacin (OF) against five Gram positive and five Gram negative bacteria. Methods Evaluation of synergy interaction between plant extracts and antimicrobial agents was carried out using disc diffusion method. Results The results of this study showed that there is an increased activity in case of combination of methanolic plant extracts and test antimicrobial agents. The more potent result was that the synergism between methanolic extract of C. papaya and antibiotics showed highest and strong synergistic effect against tested bacterial strains; though methanolic extract of C. papaya alone was not showing any antibacterial activity. Conclusions These results indicate that combination between plant extract and the antibiotics could be useful in fighting emerging drug-resistance microorganisms.