Investigation on interactive antibacterial activity of Millettia aboensis and Gongronema latifolium leaf extracts against Escherichia coli and Salmonella kintambo typed cultures

Due to bacterial resistance to synthetic antibiotics and associated problems, treatment of bacterial infections with single antibacterial agent is becoming a challenge. There are growing needs to search for combined agents from plant source that can be effective in the treatment of bacterial infections, hence, overcoming the problem of bacterial resistance. Millettia aboensis extract (MAE) and Gongronema latifolium extract (GLE) are widely combined concoctions by tradomedicine practitioners for treatment of gram-negative bacterial infections in South Eastern Nigeria. The aim of this study was to investigate on interactive antibacterial activity of Millettia aboensis and Gongronema latifolium leaf extracts against Escherichia coli and Salmonella kintambo typed cultures. This was done by extraction, determination of individual MICs of MAE and GLE using microdilution technique in a 96-well microtitre plate, subsequent determination of combined MICs using Checkerboard technique and determination of fractional inhibitory concentration index (FICI) value required for interpretation of type of interaction. From the results, individual MICs of MAE and GLE on Escherichia coli are 64mg/ml and 16mg/ml, while combination MICs is 32mg/ml and 16mg/ml respectively. On Salmonella kintambo, individual MICs of MAE and GLE are 32mg/ml and 16mg/ml, while combination MICs is 16mg/ml and 8mg/ml respectively. The FICI values on Escherichia coli and Salmonella kintambo are 1.5 and 1.0 respectively. Therefore the interactions between MAE and GLE on Escherichia coli and Salmonella kintambo are indifference and additive respectively.