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Abstract：
Among the Acinetobacter genus, Acinetobacter pittii stands out as an important opportunistic infection causative agent commonly found in hospital settings, which poses a serious threat to human health. Recently, the high prevalence of carbapenem-resistant A. pittii isolates has created significant therapeutic challenges for clinicians. Bacteriophages and their derived enzymes are promising therapeutic alternatives or adjuncts to antibiotics effective against multidrug-resistant bacterial infections. However, studies investigating the depolymerases specific to A. pittii strains are scarce. In this study, we identified and characterized a capsule depolymerase, Dpo27, encoded by the bacteriophage IME-Ap7, which targets A. pittii. A total of 23 clinical isolates of Acinetobacter spp. were identified as A. pittii (21.91%, 23/105), and seven A. pittii strains with various K locus (KL) types (KL14, KL32, KL38, KL111, KL163, KL207, and KL220) were used as host bacteria for phage screening. The lytic phage IME-Ap7 was isolated using A. pittii 7 (KL220) as an indicator bacterium and was observed for depolymerase activity. A putative tail fiber gene encoding a polysaccharide-degrading enzyme (Dpo27) was identified and expressed. The results of the modified single-spot assay showed that both A. pittii 7 and 1492 were sensitive to Dpo27, which was assigned the KL220 type. After incubation with Dpo27, A. pittii strain was susceptible to killing by human serum; moreover, the protein displayed no hemolytic activity against erythrocytes. Furthermore, the protein exhibited sustained activity across a wide pH range (5.0-10.0) and at temperatures between 20 and 50°C. In summary, the identified capsule depolymerase Dpo27 holds promise as an alternative treatment for combating KL220-type A. pittii infections.
摘要：
在不动杆菌属中，皮氏不动杆菌是医院环境中常见的重要机会性感染病原体，这对人类健康构成了严重威胁。最近,耐碳青霉烯A.pittii分离株的高流行率给临床医生带来了巨大的治疗挑战.噬菌体及其衍生的酶是有效对抗多药耐药细菌感染的抗生素的有前途的治疗替代品或辅助手段。然而,研究特定于A.pittii菌株的解聚酶的研究很少。在这项研究中,我们鉴定并表征了一种胶囊解聚酶，Dpo27，由噬菌体IME-Ap7编码，靶向Pittii。共23株临床分离的不动杆菌。被鉴定为A.pittii(21.91%，23/105),和7个具有各种K基因座（KL）类型（KL14，KL32，KL38，KL111，KL163，KL207和KL220）的pittii菌株用作宿主细菌进行噬菌体筛选。使用A.pittii7（KL220）作为指示细菌分离裂解噬菌体IME-Ap7，并观察其解聚酶活性。鉴定并表达了编码多糖降解酶（Dpo27）的推定尾纤维基因。改进的单点测定的结果表明，A.pittii7和1492对Dpo27敏感，Dpo27被指定为KL220类型。与Dpo27孵育后，A.pittii菌株容易被人血清杀死；此外，该蛋白对红细胞没有溶血活性。此外，蛋白质在宽pH范围（5.0-10.0）和20至50°C的温度下表现出持续的活性。总之,确定的胶囊解聚酶Dpo27有望作为对抗KL220型A.pittii感染的替代治疗方法。
