Institut National de la Recherche Agronomique, Biopolymères Interactions Assemblages, Equipe Fonctions et Interactions des Protéines, Nantes Cedex, France.
Benef Microbes. 2011 Mar;2(1):15-27. doi: 10.3920/BM2011.0001.
Five bacterial cocci isolates were selected from a wide pool of 503 isolates collected from traditional Egyptian dairy products on the basis of their inhibitory activities against Lactobacillus brevis F145, Lactobacillus bulgaricus 340, Enterococcus faecium HKLHS, Listeria ivanovii ATCC, Listeria innocua CIP 80.11 and Listeria monocytogenes EGDe 107776. These 5 isolates were identified as E. faecium TX1330 and E. faecium E980 by 16S rDNA amplification and sequencing. The antibacterial activity of the two strains was not affected by treatment of the cell free culture supernatant with catalase but their activities disappeared completely when digested with protease K, α-chymotrypsin and trypsin. The antimicrobial substance was stable over a wide range of pH (2-10) and was active after heating at 100 °C for 10 min. Bacteriocin yield in two strains reached a maximum (1,600 AU/ml) at the end of the exponential phase (6 h) and remained stable until the end of 24 h-incubation period when the medium reached pH 5.5. Maximal production of bacteriocin was obtained when growing the bacterial cells at temperatures ranging between 30 and 37 °C. Bacteriocin production was unaffected when the bacterial cells grew under severe conditions of pH (9.6) and in high salt (6.5% NaCl). Thanks to PCR gene amplification the bacteriocins produced by E. faecium TX1330 could be identified as enterocins A and B structural genes, while the bacteriocins produced by E. faecium E980 could be identified as enterocins P and L50A structural genes, which can be classified into two enterocin subclasses (IIa and IIc), respectively. PCR amplification demonstrated that the two studied strains did not contain virulence factors asal, cyl A and B, ace, efaAfs and espfm. These two strains were sensitive to most of the tested antibiotics but were resistant to tetracycline. E. faecium E980 was also resistant to chloramphenicol.
从传统埃及乳制品中收集的 503 个分离株中，基于其对乳酸短杆菌 F145、保加利亚乳杆菌 340、粪肠球菌 HKLHS、伊氏李斯特菌 ATCC、无害李斯特菌 CIP 80.11 和单核细胞增生李斯特菌 EGDe 107776 的抑制活性，选择了 5 个细菌球菌分离株。通过 16S rDNA 扩增和测序，这 5 个分离株被鉴定为屎肠球菌 TX1330 和屎肠球菌 E980。两株菌的抑菌活性不受无细胞培养上清液中过氧化氢酶处理的影响，但用蛋白酶 K、α-糜蛋白酶和胰蛋白酶消化后完全消失。抗菌物质在很宽的 pH 范围（2-10）下稳定，在 100°C 加热 10 分钟后仍然保持活性。两株菌的细菌素产量在指数期结束时（6 小时）达到最大值（1,600 AU/ml），并在 24 小时培养期结束时保持稳定，此时培养基达到 pH 5.5。当细菌细胞在 30-37°C 温度下生长时，细菌素产量最高。当细菌细胞在 pH（9.6）和高盐（6.5%NaCl）等恶劣条件下生长时，细菌素的产生不受影响。通过 PCR 基因扩增，鉴定屎肠球菌 TX1330 产生的细菌素为肠球菌 A 和 B 结构基因，而屎肠球菌 E980 产生的细菌素为肠球菌 P 和 L50A 结构基因，可分别归入肠球菌两个亚类（IIa 和 IIc）。PCR 扩增表明，这两个研究菌株不含有asal、cyl A 和 B、ace、efaAfs 和 espfm 等毒力因子。这两株菌对大多数测试的抗生素敏感，但对四环素耐药。屎肠球菌 E980 也对氯霉素耐药。
