Ambrosi Cecilia, Scribano Daniela, Aleandri Marta, Zagaglia Carlo, Di Francesco Laura, Putignani Lorenza, Palamara Anna Teresa
Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy.
Dani Di Giò Foundation-Onlus, Rome, Italy.
Front Microbiol. 2017 Oct 12;8:1977. doi: 10.3389/fmicb.2017.01977. eCollection 2017.
Carbapenem-resistant (CRAb) have emerged in recent decades as major causes of nosocomial infections. Resistance is mainly due to overexpression of intrinsic and/or acquired carbapenemases, especially oxacillinases (OXA). In Italy, although the sequence type (ST) 2 and the ST78 are the most frequently detected, we recently reported ST632, a single locus variant of ST2. Therefore, this study was aimed at unraveling common bacterial surface virulence factors involved in pathogenesis and antibiotic resistance in representative CRAb of these ST genotypes. Outer membrane protein (OMP) composition together with motility, biofilm formation, adherence to, invasion of, and survival within pneumocytes were analyzed. Differently from the carbapenem-susceptible reference strain ATCC 17978, either overexpressed OXA-51 or both OXA-23 and OXA-51 co-purified with OMPs in CRAb. This tight association ensures their maximal concentration on the inner surface of the outer membrane to provide the best protection against carbapenems. These findings led us to propose for the first time a common behavior of OXA enzymes in CRAb. Despite the presence of both OmpA and phosphorylcholine-porinD and the ability of all the strains to adhere to cells, invasion, and survival within pneumocytes was shown only by ST2 and ST78 isolates, sharing the highest number of identified OMPs. Conversely, notwithstanding genetic and OMPs similarities with ST2, ST632 was unable to invade and survive within epithelial cells. Overall, our study shows that different STs share a specific OMP composition, also shaped by overexpressed OXA, that is needed for invasiveness and survival of CRAb.
耐碳青霉烯类鲍曼不动杆菌（CRAb）在近几十年已成为医院感染的主要原因。耐药性主要归因于固有和/或获得性碳青霉烯酶的过度表达，尤其是氧青霉烯酶（OXA）。在意大利，虽然序列类型（ST）2和ST78是最常检测到的，但我们最近报告了ST632，它是ST2的单一位点变体。因此，本研究旨在揭示这些ST基因型的代表性CRAb中参与发病机制和抗生素耐药性的常见细菌表面毒力因子。分析了外膜蛋白（OMP）组成以及运动性、生物膜形成、对肺细胞的黏附、侵袭和在肺细胞内的存活情况。与碳青霉烯敏感参考菌株ATCC 17978不同，在CRAb中，要么OXA-51过度表达，要么OXA-23和OXA-51两者都与OMP共纯化。这种紧密关联确保了它们在外膜内表面的最大浓度，以提供对碳青霉烯类药物的最佳保护。这些发现使我们首次提出了CRAb中OXA酶的共同行为。尽管所有菌株都存在OmpA和磷酸胆碱孔蛋白D，并且都有黏附细胞的能力，但只有ST2和ST78分离株表现出对肺细胞的侵袭和在肺细胞内的存活能力，它们具有最多已鉴定的OMP。相反，尽管ST632与ST2在基因和OMP方面有相似性，但它无法在上皮细胞内侵袭和存活。总体而言，我们的研究表明，不同的ST共享一种特定的OMP组成，这种组成也受到过度表达的OXA的影响，这是CRAb侵袭性和存活所必需的。
