Davies Emily V, James Chloe E, Brockhurst Michael A, Winstanley Craig
Institute of Infection and Global Health, University of Liverpool, 8 West Derby Street, Liverpool, L69 7BE, UK.
School of Environment and Life Sciences, University of Salford, Manchester, M5 4WT, UK.
BMC Microbiol. 2017 Jan 5;17(1):3. doi: 10.1186/s12866-016-0916-z.
During chronic lung infections of cystic fibrosis patients Pseudomonas aeruginosa populations undergo extensive evolutionary diversification. However, the selective drivers of this evolutionary process are poorly understood. To test the effects of temperate phages on diversification in P. aeruginosa biofilms we experimentally evolved populations of P. aeruginosa for approximately 240 generations in artificial sputum medium with or without a community of three temperate phages.
Analysis of end-point populations using a suite of phenotypic tests revealed extensive phenotypic diversification within populations, but no significant differences between the populations evolved with or without phages. The most common phenotypic variant observed was loss of all three types of motility (swimming, swarming and twitching) and resistance to all three phages. Despite the absence of selective pressure, some members of the population evolved antibiotic resistance. The frequency of antibiotic resistant isolates varied according to population and the antibiotic tested. However, resistance to ceftazidime and tazobactam-piperacillin was observed more frequently than resistance to other antibiotics, and was associated with higher prevelence of isolates exhibiting a hypermutable phenotype and increased beta-lactamase production.
We observed considerable within-population phenotypic diversity in P. aeruginosa populations evolving in the artificial sputum medium biofilm model. Replicate populations evolved both in the presence and absence of phages converged upon similar sets of phenotypes. The evolved phenotypes, including antimicrobial resistance, were similar to those observed amongst clinical isolates from cystic fibrosis infections.
在囊性纤维化患者的慢性肺部感染期间，铜绿假单胞菌群体经历了广泛的进化多样化。然而，这一进化过程的选择驱动因素却知之甚少。为了测试温和噬菌体对铜绿假单胞菌生物膜多样化的影响，我们在含有或不含有三种温和噬菌体群落的人工痰液培养基中，对铜绿假单胞菌群体进行了约240代的实验进化。
使用一系列表型测试对终点群体进行分析，结果显示群体内部存在广泛的表型多样化，但在有噬菌体或无噬菌体情况下进化的群体之间没有显著差异。观察到的最常见表型变异是三种运动性（游泳、群集和颤动）全部丧失以及对所有三种噬菌体产生抗性。尽管没有选择压力，但群体中的一些成员仍进化出了抗生素抗性。抗生素抗性分离株的频率因群体和所测试的抗生素而异。然而，对头孢他啶和他唑巴坦 - 哌拉西林的抗性比其他抗生素更为常见，并且与表现出超突变表型和β - 内酰胺酶产生增加的分离株的更高流行率相关。
我们在人工痰液培养基生物膜模型中进化的铜绿假单胞菌群体中观察到了相当大的群体内表型多样性。在有噬菌体和无噬菌体情况下进化的重复群体在相似的表型组上趋同。所进化出的表型，包括抗菌抗性，与囊性纤维化感染临床分离株中观察到的表型相似。
