Antibacterial Activity of Lactic Acid Producing Leuconostoc mesenteroides QZ1178 Against Pathogenic Gallibacterium anatis

Abstract

Lactic acid bacteria (LAB) convert carbohydrates into organic acids [mainly lactic acid (LA)], which reportedly have bactericidal activities. <i>Gallibacterium anatis</i> is a Gram-negative bacteria which infects birds, and causes significant economic losses. In this study, we investigated the antibacterial activity of the LA producing, <i>Leuconostoc mesenteroides</i> QZ1178 from Qula (fermented food), against <i>G. anatis</i>, using the Oxford cup method. Our data showed that <i>L. mesenteroides</i> QZ1178 inhibited <i>G. anatis</i> isolates from different origins; however, <i>L. mesenteroides</i> QZ1178 antibacterial activity dropped dramatically at pH 5.5-pH 6. The LA concentration and pH of the liquid broth containing <i>L. mesenteroides</i> QZ1178 after 24 h culture was 29 mg/mL and 3.6, respectively. This concentration (29 mg/mL at pH 3.6) and the antibiotic, cefotaxime (minimum inhibitory concentration (MIC) 2.5 μg/mL) effectively inhibited <i>G. anatis</i> (GAC026) growth as observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). <i>Gallibacterium anatis</i> treated with LA exhibited extensive cell surface collapse, increased cell damage, cell membrane disruption, and cytoplasmic leakage, indicative of cell lysis. We suggest <i>L. mesenteroides</i> QZ1178 exerts potential antibacterial effects against the poultry pathogen, <i>G. anatis</i> via LA.