Montealegre Maria Camila, Singh Kavindra V, Somarajan Sudha R, Yadav Puja, Chang Chungyu, Spencer Robert, Sillanpää Jouko, Ton-That Hung, Murray Barbara E
Department of Internal Medicine, Division of Infectious Diseases, The University of Texas Health Science Center at Houston, Houston, Texas, USA.
Center for the Study of Emerging and Re-emerging Pathogens, The University of Texas Health Science Center at Houston, Houston, Texas, USA.
Infect Immun. 2016 Apr 22;84(5):1491-1500. doi: 10.1128/IAI.01396-15. Print 2016 May.
Enterococcus faecium is an important cause of hospital-associated infections, including urinary tract infections (UTIs), bacteremia, and infective endocarditis. Pili have been shown to play a role in the pathogenesis of Gram-positive bacteria, including E. faecium We previously demonstrated that a nonpiliated ΔempABC::cat derivative of E. faecium TX82 was attenuated in biofilm formation and in a UTI model. Here, we studied the contributions of the individual pilus subunits EmpA, EmpB, and EmpC to pilus architecture, biofilm formation, adherence to extracellular matrix (ECM) proteins, and infection. We identified EmpA as the tip of the pili and found that deletion of empA reduced biofilm formation to the same level as deletion of the empABC operon, a phenotype that was restored by reconstituting in situ the empA gene. Deletion of empB also caused a reduction in biofilm, while EmpC was found to be dispensable. Significant reductions in adherence to fibrinogen and collagen type I were observed with deletion of empA and empB, while deletion of empC had no adherence defect. Furthermore, we showed that each deletion mutant was significantly attenuated in comparison to the isogenic parental strain, TX82, in a mixed-inoculum UTI model (P < 0.001 to 0.048), that reconstitution of empA restored virulence in the UTI model, and that deletion of empA also resulted in attenuation in an infective endocarditis model (P = 0.0088). Our results indicate that EmpA and EmpB, but not EmpC, contribute to biofilm and adherence to ECM proteins; however, all the Emp pilins are important for E. faecium to cause infection in the urinary tract.
屎肠球菌是医院获得性感染的重要病因，包括尿路感染（UTIs）、菌血症和感染性心内膜炎。菌毛已被证明在革兰氏阳性菌（包括屎肠球菌）的发病机制中起作用。我们之前证明，屎肠球菌TX82的非菌毛ΔempABC::cat衍生物在生物膜形成和UTI模型中减弱。在这里，我们研究了单个菌毛亚基EmpA、EmpB和EmpC对菌毛结构、生物膜形成、对细胞外基质（ECM）蛋白的粘附以及感染的贡献。我们确定EmpA是菌毛的尖端，发现empA的缺失将生物膜形成减少到与empABC操纵子缺失相同的水平，通过原位重建empA基因可恢复该表型。empB的缺失也导致生物膜减少，而发现EmpC是可有可无的。empA和empB缺失时，观察到对纤维蛋白原和I型胶原的粘附显著减少，而empC缺失则没有粘附缺陷。此外，我们表明，在混合接种UTI模型中，与同基因亲本菌株TX82相比，每个缺失突变体均显著减弱（P < 0.001至0.048），empA的重建恢复了UTI模型中的毒力，并且empA的缺失在感染性心内膜炎模型中也导致减弱（P = 0.0088）。我们的结果表明，EmpA和EmpB而非EmpC有助于生物膜形成和对ECM蛋白的粘附；然而，所有的Emp菌毛蛋白对于屎肠球菌在泌尿道引起感染都很重要。
