The in vitro Antibacterial Activity of Macleaya cordata Extract against Four Common Pathogenic Bacteria in Pig Farms

PurposeThe aim was to study the in vitro antibacterial activity of Macleaya cordata extract (MCE), and to provide experimental basis for its application and addition in animal industry.

MethodStaphylococcus aureus, Salmonella choleraesuis, Escherichia coli and Pseudomonas aeruginosa were selected as the test bacteria. The inhibition efficacy of MCE on 4 kinds of tested bacteria was measured by radial diffusion assay. Minimum inhibitory mass concentration (MIC) and minimum bactericidal mass concentration (MBC) of MCE against 4 different strains were determined by microdilution method. The dynamic bactericidal effects of MCE on S. aureus and E. coli were determined by time-killing curve.

ResultMCE has a certain inhibitory effect on the 4 gram-positive and negative bacteria, and the inhibition ability from strong to weak is S. aureus, E. coli, S. choleraesuis, P. aeruginosa successively. The MIC values of MCE against S. aureus, E. coli, S. choleraesuis and P. aeruginosa were 64, 64, 128 and 512 μg/mL, respectively, and the MBC values were 128, 128, 256 and >1024 μg/mL, respectively. The in vitro bactericidal rate of MCE against S. aureus and E. coli increased with the increase of concentration. Among them, MCE with concentration of 8, 4 and 2×MIC could completely kill the two tested bacteria after 2, 12 and 24 hours respectively, while a small amount of bacteria could still survive after the 24 hours treatment with concentration of 1×MIC MCE.

ConclusionMCE had certain inhibitory effect on the tested bacteria, and its in vitro bactericidal rate against S. aureus and E. coli appeared to be concentration-dependent.