Department of Infection, University of Leicester, Leicester LE1 9HN, United Kingdom.
Infect Immun. 2010 Apr;78(4):1437-46. doi: 10.1128/IAI.00621-09. Epub 2010 Feb 1.
Pseudomonas aeruginosa is a leading cause of hospital-acquired pneumonia and severe chronic lung infections in cystic fibrosis patients. The reference strains PA14 and PAO1 have been studied extensively, revealing that PA14 is more virulent than PAO1 in diverse infection models. Among other factors, this may be due to two pathogenicity islands, PAPI-1 and PAPI-2, both present in PA14 but not in PAO1. We compared the global contributions to virulence of PAPI-1 and PAPI-2, rather than that of individual island-borne genes, using murine models of acute pneumonia and bacteremia. Three isogenic island-minus mutants (PAPI-1-minus, PAPI-2-minus, and PAPI-1-minus, PAPI-2-minus mutants) were compared with the wild-type parent strain PA14 and with PAO1. Our results showed that both islands contributed significantly to the virulence of PA14 in acute pneumonia and bacteremia models. However, in contrast to the results for the bacteremia model, where each island was found to contribute individually, loss of the 108-kb PAPI-1 island alone was insufficient to measurably attenuate the mutant in the acute pneumonia model. Nevertheless, the double mutant was substantially more attenuated, and exhibited a lesser degree of virulence, than even PAO1 in the acute pneumonia model. In particular, its ability to disseminate from the lungs to the bloodstream was markedly inhibited. We conclude that both PAPI-1 and PAPI-2 contribute directly and synergistically in a major way to the virulence of PA14, and we suggest that analysis of island-minus strains may be a more appropriate way than individual gene knockouts to assess the contributions to virulence of large, horizontally acquired segments of DNA.
铜绿假单胞菌是医院获得性肺炎和囊性纤维化患者严重慢性肺部感染的主要病原体。参考菌株 PA14 和 PAO1 已经被广泛研究，研究表明，在各种感染模型中，PA14 比 PAO1 具有更强的毒力。除其他因素外，这可能是由于两个毒力岛 PAPI-1 和 PAPI-2 所致，这两个毒力岛都存在于 PA14 中，但不存在于 PAO1 中。我们使用急性肺炎和菌血症的小鼠模型比较了 PAPI-1 和 PAPI-2 对毒力的整体贡献，而不是单个岛携带基因的贡献。我们将三个同基因岛缺失突变体（PAPI-1 缺失突变体、PAPI-2 缺失突变体和 PAPI-1 缺失突变体、PAPI-2 缺失突变体）与野生型亲本菌株 PA14 和 PAO1 进行了比较。我们的结果表明，两个岛都显著促进了 PA14 在急性肺炎和菌血症模型中的毒力。然而，与菌血症模型的结果相反，在该模型中，每个岛都被发现各自独立地发挥作用，单独缺失 108kb 的 PAPI-1 岛不足以使突变体在急性肺炎模型中明显减毒。尽管如此，双突变体在急性肺炎模型中的减毒程度明显高于 PAO1，其毒力也明显降低。特别是，它从肺部传播到血液的能力受到明显抑制。我们得出结论，PAPI-1 和 PAPI-2 都直接且协同地对 PA14 的毒力产生重大影响，我们建议分析岛缺失菌株可能是一种比单个基因敲除更合适的方法，用于评估水平获得的大型 DNA 片段对毒力的贡献。
