Dept. of Nutrition and Food Technology, Al-Balqa Applied Univ., Salt, Jordan, 19117.
J Food Sci. 2013 Sep;78(9):M1416-20. doi: 10.1111/1750-3841.12209. Epub 2013 Aug 7.
Cronobacter sakazakii is an opportunistic pathogen that can cause bacteremia, meningitis, and necrotizing enterocolitis, most often in neonates with case-fatality rates that may reach 80%. The antimicrobial activity of lactic acid bacteria against a wide range of foodborne pathogens is well-established in different types of food products. The objective of the current study was to investigate the antibacterial activity of Lactobacillus acidophilus and L. casei isolated from feces of healthy infants against different strains of C. sakazakii in agar and a rehydrated infant milk formula (RIMF) model. The inhibition zones of C. sakazakii around L. acidophilus or L. casei ranged from 22 to 32 mm on eMan Rogosa Sharpe (MRS) agar under aerobic conditions, while a slight reduction in antibacterial activity was noted on modified MRS (0.2% glucose) under anaerobic conditions. It was observed that pH-neutralized cell-free supernatant (CFS) of L. acidophilus or L. casei was inhibitory against tested C. sakazakii strains. The inhibition zones of neutralized CFS were lower than the antibacterial activities of live cultures. The antibacterial activity of CFS was abolished when CFS from L. acidophilus or L. casei was heated at 60 or 80 °C for either 10 min or 2 h, or treated with trypsin or pepsin. This was considered strong evidence that the inhibition was due to the production of bacteriocins by L. casei and L. acidophilus. Both the CFS and active growing cells of L. casei and L. acidophilus were able to reduce the viability of C. sakazakii in the RIMF model. The results may extend the use of natural antimicrobials instead of conventional preservation methods to improve the safety of RIMF.
阪崎克罗诺杆菌是一种机会致病菌，可导致败血症、脑膜炎和坏死性小肠结肠炎，最常发生于新生儿，病死率可能高达 80%。在不同类型的食品中，已证实乳酸菌对多种食源性致病菌具有抗菌活性。本研究旨在研究从健康婴儿粪便中分离出的嗜酸乳杆菌和干酪乳杆菌对不同阪崎克罗诺杆菌菌株的抗菌活性，采用琼脂和再水化婴儿配方奶粉（RIMF）模型进行研究。在需氧条件下，嗜酸乳杆菌或干酪乳杆菌周围的阪崎克罗诺杆菌的抑菌圈直径在 eMan Rogosa Sharpe（MRS）琼脂上为 22-32mm，而在厌氧条件下改良 MRS（0.2%葡萄糖）中观察到抗菌活性略有降低。研究发现，嗜酸乳杆菌或干酪乳杆菌的 pH 中和无细胞上清液（CFS）对测试的阪崎克罗诺杆菌菌株具有抑制作用。中性化 CFS 的抑菌圈小于活菌培养物的抗菌活性。嗜酸乳杆菌或干酪乳杆菌的 CFS 在 60 或 80°C 加热 10 分钟或 2 小时，或用胰蛋白酶或胃蛋白酶处理时，其抗菌活性被消除。这有力地证明了抑制作用是由于干酪乳杆菌和嗜酸乳杆菌产生细菌素所致。CFS 和干酪乳杆菌及嗜酸乳杆菌的活性生长细胞均能降低 RIMF 模型中阪崎克罗诺杆菌的活力。研究结果可能会扩大天然抗菌剂的使用范围，以替代传统的保存方法，从而提高 RIMF 的安全性。
