抗生素耐药鲍曼不动杆菌的传播对世界范围内的公众健康构成重大威胁。这种医院细菌病原体可能与危及生命的感染有关,特别是在重症监护病房。鲍曼不动杆菌主要被描述为细胞内存活受限的细胞外病原体。这项研究表明,鲍曼不动杆菌临床分离株的一部分在非吞噬永生化和原代细胞中广泛繁殖,而不会诱导细胞凋亡,并且在感染后48小时内可见细菌簇。在医院爆发时与高死亡率相关的鲍曼不动杆菌C4菌株和鲍曼不动杆菌ABC141菌株中观察到了这种表型,从皮肤中分离出来,但被发现是高侵袭性的。这些鲍曼不动杆菌菌株的细胞内繁殖发生在宽敞的单膜结合液泡内,用溶酶体缔合膜蛋白(LAMP1)标记。然而,这些隔间不包括裂解器,酸性pH的指示剂,这表明鲍曼不动杆菌可以将其运输从溶酶体降解途径转移。这些区室也缺乏自噬特征。对43个额外的鲍曼不动杆菌临床分离株的高含量显微镜筛查突出了各种表型,并且(i)大多数分离株仍保留在细胞外,(Ii)很大一部分能够入侵和有限的持久性,和(iii)三个分离株在LAMP1阳性液泡内有效繁殖,其中之一也是高侵入性的。这些数据确定了特定鲍曼不动杆菌临床分离株的细胞内生态位,其能够在受保护免受宿主免疫应答和许多抗生素无法触及的环境中广泛繁殖。重要性多重耐药鲍曼不动杆菌分离株在全世界的医院中与显著的发病率和死亡率相关。了解其致病性对于改善治疗管理至关重要。尽管鲍曼不动杆菌可以稳定地粘附在表面和宿主细胞上,大多数细菌都保留在细胞外。最近的研究表明,一小部分细菌可以侵入细胞,但存活有限。我们已经发现,一些鲍曼不动杆菌临床分离株可以建立专门的细胞内生态位,其长时间维持广泛的细胞内增殖而不诱导细胞死亡。我们认为细胞内区室允许鲍曼不动杆菌逃脱细胞的正常降解途径,保护细菌免受宿主免疫反应,并可能阻碍抗生素的使用。这可能有助于鲍曼不动杆菌的持久性,复发性感染,和增加易感患者的死亡率。基于高含量显微镜的筛选证实该致病性性状存在于其他临床鲍曼不动杆菌分离株中。迫切需要新的抗生素或替代的抗菌方法,特别是对抗耐碳青霉烯的鲍曼不动杆菌。这种病原体的细胞内生态位的发现,以及高侵袭性分离株,可能有助于指导未来抗菌治疗和诊断的发展。
The spread of antibiotic-resistant Acinetobacter baumannii poses a significant threat to public health worldwide. This nosocomial bacterial pathogen can be associated with life-threatening infections, particularly in intensive care units. A. baumannii is mainly described as an extracellular pathogen with restricted survival within cells. This study shows that a subset of A. baumannii clinical isolates extensively multiply within nonphagocytic immortalized and primary cells without the induction of apoptosis and with bacterial clusters visible up to 48 h after infection. This phenotype was observed for the A. baumannii C4 strain associated with high mortality in a hospital outbreak and the A. baumannii ABC141 strain, which was isolated from the skin but was found to be hyperinvasive. Intracellular multiplication of these A. baumannii strains occurred within spacious single membrane-bound vacuoles, labeled with the lysosomal associate membrane protein (LAMP1). However, these compartments excluded lysotracker, an indicator of acidic pH, suggesting that A. baumannii can divert its trafficking away from the lysosomal degradative pathway. These compartments were also devoid of autophagy features. A high-content microscopy screen of 43 additional A. baumannii clinical isolates highlighted various phenotypes, and (i) the majority of isolates remained extracellular, (ii) a significant proportion was capable of invasion and limited persistence, and (iii) three more isolates efficiently multiplied within LAMP1-positive vacuoles, one of which was also hyperinvasive. These data identify an intracellular niche for specific A. baumannii clinical isolates that enables extensive multiplication in an environment protected from host immune responses and out of reach of many antibiotics. IMPORTANCE Multidrug-resistant Acinetobacter baumannii isolates are associated with significant morbidity and mortality in hospitals worldwide. Understanding their pathogenicity is critical for improving therapeutic management. Although A. baumannii can steadily adhere to surfaces and host cells, most bacteria remain extracellular. Recent studies have shown that a small proportion of bacteria can invade cells but present limited survival. We have found that some A. baumannii clinical isolates can establish a specialized intracellular niche that sustains extensive intracellular multiplication for a prolonged time without induction of cell death. We propose that this intracellular compartment allows A. baumannii to escape the cell\'s normal degradative pathway, protecting bacteria from host immune responses and potentially hindering antibiotic accessibility. This may contribute to A. baumannii persistence, relapsing infections, and enhanced mortality in susceptible patients. A high-content microscopy-based screen confirmed that this pathogenicity trait is present in other clinical A. baumannii isolates. There is an urgent need for new antibiotics or alternative antimicrobial approaches, particularly to combat carbapenem-resistant A. baumannii. The discovery of an intracellular niche for this pathogen, as well as hyperinvasive isolates, may help guide the development of antimicrobial therapies and diagnostics in the future.