Department of Microbiology, School of Medicine, International Campus, Iran University of Medical Sciences, Tehran, Iran.
Department of Microbiology, School of Medicine, International Campus, Iran University of Medical Sciences, Tehran, Iran.
Microb Pathog. 2018 May;118:242-246. doi: 10.1016/j.micpath.2018.03.020. Epub 2018 Mar 15.
The purpose of the present study was to isolate Lactobacillus bacteria from mother's milk and to assess their probiotic potential. Sixty breast milk samples were collected from the volunteered mothers aged from 19 to 35 and from rural areas of Lorestan and Markazi Provinces, Iran. At first, 970 bacill-shaped bacterial colonies were isolated from these samples and stored in proper condition. Two hundred isolates were randomly selected and investigated for their ability to tolerate acidic condition and to tolerate bile salt as well. Only 33 isolates could withstand the exposure to low pH and bile salt. The isolates were identified using PCR primer specific to Lactobacillus and it was demonstrated that eighteen of thirty-three isolates were belonged to the Lactobacillus. Among the isolates, 16 and 2 of them were Lactobacillus reuteri and L. gasseri, respectively. In addition, the antibiotic resistance of the isolates was determined using disc diffusion method and all of the isolates were shown to be sensitive to eight out of the twelve investigated antibiotics. Moreover, the antagonistic effect of the isolates was inspected on ten indicator pathogens. Interestingly, all of the pathogenic bacteria were inhibited by Lactobacillus isolates. In addition, to partially understand the nature of inhibition mechanism, well diffusion deployed for two randomly-selected indicator bacteria and the resulting halos of three isolates were statistically significant compared to other lactobacillus (p < 0.05). Subsequently, bacteriocin genes (plnS, Laf, gasA) were identified by PCR among the isolates. The results showed that only 2 isolates possessed the gasA gene which were in accordance with well diffusion test. Consequently, eighteen Lactobacillus isolated from breast milk samples which all of them were able to tolerate low pH and bile salt. Similarly, all of the Lactobacillus isolates were proved to inhibit the growth of pathogen strains and two of them possess a bacteriocin-related gene.
本研究的目的是从母乳中分离出乳酸菌，并评估其益生菌潜力。从伊朗洛雷斯坦省和马赞德兰省农村地区的 19 至 35 岁的志愿者母亲中收集了 60 份母乳样本。首先，从这些样本中分离出 970 个杆菌状细菌菌落，并在适当的条件下储存。随机选择 200 个分离株，研究其耐受酸性条件和耐受胆盐的能力。只有 33 个分离株能够耐受低 pH 值和胆盐的暴露。使用针对乳酸菌的 PCR 引物鉴定分离株，结果表明 33 个分离株中有 18 个属于乳酸菌。在这些分离株中，16 个和 2 个分别为乳杆菌和罗伊氏乳杆菌。此外，使用圆盘扩散法测定了分离株的抗生素耐药性，所有分离株对 12 种抗生素中的 8 种均表现出敏感性。此外，还检测了分离株对 10 种指示病原体的拮抗作用。有趣的是，所有致病菌均被乳酸菌分离株抑制。此外，为了部分了解抑制机制的性质，对两种随机选择的指示菌进行了良好的扩散，并对 3 个分离株的晕圈与其他乳酸菌进行了统计分析，结果表明，与其他乳酸菌相比，差异具有统计学意义（p < 0.05）。随后，通过 PCR 在分离株中鉴定了细菌素基因（plnS、Laf、gasA）。结果表明，只有 2 个分离株携带 gasA 基因，与良好扩散试验一致。因此，从母乳样本中分离出的 18 个乳酸菌都能够耐受低 pH 值和胆盐。同样，所有的乳酸菌分离株都被证明能够抑制病原菌的生长，其中 2 个分离株具有细菌素相关基因。
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