Hamed Samira M, Abdel-Daim Amira, Tadros Samer A, Zafer Mai M
Department of Microbiology and Immunology, Faculty of Pharmacy, October University for Modern Sciences and Arts (MSA), Giza, Egypt.
Department of Biochemistry, Faculty of Pharmacy, October University for Modern Sciences and Arts (MSA), Giza, Egypt.
BMC Microbiol. 2025 Jul 23;25(1):449. doi: 10.1186/s12866-025-04177-z.
Filamentous phages (FPs) have been recently isolated from Acinetobacter baumannii. While FPs are known to modulate the virulence of some Gram-negative pathogens, their role in A. baumannii has not been fully explored. This study analyzed 18 clinical isolates of A. baumannii from global clones (GC), with draft genomes generated by Illumina sequencing. All isolates were screened for filamentous prophage (FPP) genomes using the Zonula occludens toxin (Zot)-coding gene as a marker. Nine out of the 18 isolates were found to carry zot genes. The complete sequences of four FPPs were predicted. FPPs were exclusively found within GC1, GC7, and GC9 strains. Among the A. baumannii genomes deposited in the NCBI genomic database, FPPs were found to be disseminated in 42 Pasteur STs spanning at least six GCs, most commonly GC1. The impact of FPs on biofilm formation in A. baumannii was investigated using crystal violet assay. None of the zot-negative isolates formed strong biofilms, while six (66.6%) zot-positive isolates did. The biofilm indices of zot-positive isolates were significantly higher compared to zot-negative isolates. The potential enterotoxicity of the zot-positive strains was also assessed using in silico and experimental methods. The cytotoxic effect of cell-free supernatants (CFSs) on Caco-2 cells was measured by the MTT assay. Cells treated with CFSs from zot-positive strains exhibited significantly higher cytotoxicity than those treated with CFSs from zot-negative strains. Upon injecting the CFS of a zot-positive strain intraperitoneally into BALB/c mice, severe diarrhea was observed within 6 h. Histological examination of the intestinal tissue 24 h post-injection revealed significant changes. In conclusion, this study suggests that FPPs are widely disseminated in A. baumannii GCs and may enhance biofilm formation and enterotoxicity, potentially contributing to the pathogen's virulence.
丝状噬菌体（FPs）最近已从鲍曼不动杆菌中分离出来。虽然已知丝状噬菌体可调节一些革兰氏阴性病原体的毒力，但其在鲍曼不动杆菌中的作用尚未得到充分研究。本研究分析了来自全球克隆（GC）的18株鲍曼不动杆菌临床分离株，通过Illumina测序生成了草图基因组。使用编码小带闭合蛋白毒素（Zot）的基因作为标记，对所有分离株进行丝状前噬菌体（FPP）基因组筛选。在18株分离株中，有9株被发现携带zot基因。预测了4个FPP的完整序列。FPP仅在GC1、GC7和GC9菌株中发现。在NCBI基因组数据库中保存的鲍曼不动杆菌基因组中，发现FPP分布于至少六个GC的42个巴斯德序列类型（Pasteur STs）中，最常见的是GC1。使用结晶紫测定法研究了丝状噬菌体对鲍曼不动杆菌生物膜形成的影响。所有zot阴性分离株均未形成强生物膜，而6株（66.6%）zot阳性分离株形成了强生物膜。与zot阴性分离株相比，zot阳性分离株的生物膜指数显著更高。还使用计算机模拟和实验方法评估了zot阳性菌株的潜在肠毒性。通过MTT测定法测量无细胞上清液（CFSs）对Caco-2细胞的细胞毒性作用。用zot阳性菌株的CFS处理的细胞比用zot阴性菌株的CFS处理的细胞表现出显著更高的细胞毒性。将zot阳性菌株的CFS腹腔注射到BALB/c小鼠体内后，6小时内观察到严重腹泻。注射后24小时对肠道组织进行组织学检查发现有显著变化。总之，本研究表明FPP在鲍曼不动杆菌GC中广泛传播，可能增强生物膜形成和肠毒性， potentially contributing to the pathogen's virulence.（原文此处表述有误，正确的应该是“可能有助于病原体的毒力”），可能有助于病原体的毒力。
