Duerkop Breck A, Huo Wenwen, Bhardwaj Pooja, Palmer Kelli L, Hooper Lora V
Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA.
mBio. 2016 Aug 30;7(4):e01304-16. doi: 10.1128/mBio.01304-16.
The human intestine harbors diverse communities of bacteria and bacteriophages. Given the specificity of phages for their bacterial hosts, there is growing interest in using phage therapies to combat the rising incidence of multidrug-resistant bacterial infections. A significant barrier to such therapies is the rapid development of phage-resistant bacteria, highlighting the need to understand how bacteria acquire phage resistance in vivo Here we identify novel lytic phages in municipal raw sewage that kill Enterococcus faecalis, a Gram-positive opportunistic pathogen that resides in the human intestine. We show that phage infection of E. faecalis requires a predicted integral membrane protein that we have named PIPEF (for phage infection protein from E. faecalis). We find that PIPEF is conserved in E. faecalis and harbors a 160-amino-acid hypervariable region that determines phage tropism for distinct enterococcal strains. Finally, we use a gnotobiotic mouse model of in vivo phage predation to show that the sewage phages temporarily reduce E. faecalis colonization of the intestine but that E. faecalis acquires phage resistance through mutations in PIPEF Our findings define the molecular basis for an evolutionary arms race between E. faecalis and the lytic phages that prey on them. They also suggest approaches for engineering E. faecalis phages that have altered host specificity and that can subvert phage resistance in the host bacteria.
Bacteriophage therapy has received renewed attention as a potential solution to the rise in antibiotic-resistant bacterial infections. However, bacteria can acquire phage resistance, posing a major barrier to phage therapy. To overcome this problem, it is necessary to understand phage resistance mechanisms in bacteria. We have unraveled one such resistance mechanism in Enterococcus faecalis, a Gram-positive natural resident of the human intestine that has acquired antibiotic resistance and can cause opportunistic infections. We have identified a cell wall protein hypervariable region that specifies phage tropism in E. faecalis Using a gnotobiotic mouse model of in vivo phage predation, we show that E. faecalis acquires phage resistance through mutations in this cell wall protein. Our findings define the molecular basis for lytic phage resistance in E. faecalis They also suggest opportunities for engineering E. faecalis phages that circumvent the problem of bacterial phage resistance.
人类肠道中栖息着各种各样的细菌群落和噬菌体群落。鉴于噬菌体对其细菌宿主具有特异性，人们越来越有兴趣利用噬菌体疗法来应对多重耐药细菌感染发病率的上升。此类疗法的一个重大障碍是噬菌体抗性细菌的迅速出现，这凸显了了解细菌在体内如何获得噬菌体抗性的必要性。在此，我们在城市原污水中鉴定出新型裂解性噬菌体，它们能够杀死粪肠球菌，这是一种存在于人类肠道中的革兰氏阳性机会致病菌。我们发现，粪肠球菌的噬菌体感染需要一种预测的整合膜蛋白，我们将其命名为PIPEF（粪肠球菌噬菌体感染蛋白）。我们发现PIPEF在粪肠球菌中保守存在，并且含有一个160个氨基酸的高变区，该区域决定了噬菌体对不同肠球菌菌株的嗜性。最后，我们利用体内噬菌体捕食的悉生小鼠模型表明，污水噬菌体可暂时减少粪肠球菌在肠道中的定殖，但粪肠球菌会通过PIPEF中的突变获得噬菌体抗性。我们的研究结果确定了粪肠球菌与其捕食性裂解性噬菌体之间进化军备竞赛的分子基础。它们还提出了改造粪肠球菌噬菌体的方法，这些噬菌体具有改变的宿主特异性，能够颠覆宿主细菌中的噬菌体抗性。
噬菌体疗法作为抗生素耐药细菌感染增加的一种潜在解决方案，已重新受到关注。然而，细菌能够获得噬菌体抗性，这对噬菌体疗法构成了重大障碍。为克服这一问题，有必要了解细菌中的噬菌体抗性机制。我们在粪肠球菌中揭示了一种这样的抗性机制，粪肠球菌是人类肠道中的革兰氏阳性常住菌，已获得抗生素抗性并可引起机会性感染。我们鉴定出一个细胞壁蛋白高变区，它决定了粪肠球菌中的噬菌体嗜性。利用体内噬菌体捕食的悉生小鼠模型，我们表明粪肠球菌通过该细胞壁蛋白中的突变获得噬菌体抗性。我们的研究结果确定了粪肠球菌中裂解性噬菌体抗性的分子基础。它们还提出了改造粪肠球菌噬菌体的机会，这些噬菌体可规避细菌噬菌体抗性问题。
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