Antibacterial activity of taro (Colocasia esculenta L.) leaves extracts against Staphylococcus aureus and Vibrio parahaemolyticus and its effect on microbial population in sardine (Sardinella longiceps Val.)

Abstract

Colocasia esculenta L. which is popularly known in Malaysia as '‘keladi’' has extensive traditional uses for certain of the plant part such as the leaves, corm and stem. An earlier study has reported on the analysis of its pharmacological properties such as anti-inflammatory and antibacterial activity. This study aimed to determine the antibacterial activity of C. esculenta L. leaves extracts against Staphylococcus aureus ATCC 29737 and Vibrio parahaemolyticus ATCC 17802 and its effect on the microbial population of sardine. The extract was tested for antibacterial activity against S. aureus and V. parahaemolyticus in term of disc diffusion assay (DDA), minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and killing time curve by using Clinical and Laboratory Standard Institute (CLSI) methods. DDA assay of the extract resulted in 8.40±0.10 mm and 8.20±0.16 mm of inhibition zone of the extract on S. aureus and V. parahaemolyticus, respectively. The extract can inhibit the growth of S. aureus and V. parahaemolyticus with MICs values of 1.25±0.00 and 0.31±0.00 mg/mL and can kill the bacteria with MBCs values of 2.50±0.00 and 0.63±0.00 mg/mL, respectively. The killing time analyses showed that the S. aureus and V. parahaemolyticus can be killed completely for 4 hrs at 2 × MIC (25.0 mg/mL) and 2 × MIC (6.25 mg/mL), respectively. Application of the extract on sardine samples shows significant reduction in total plate count (TPC), S. aureus and V. parahaemolyticus count after treated with 5.00% of the extract and stored at 4°C for 30 mins. Based on the findings, it indicates that C. esculenta L. can be listed as one of the alternatives natural sanitiser or preservative agent to reduce the bacterial loading of raw sardine prior to cooking.