Ali Hayssam M, Salem Mohamed Z M, El-Shikh Mohamed S, Megeed Ahmed Abdel, Alogaibi Yahya A, Talea Ibrahim Ahmed
King Saud University, College of Science, Department of Botany and Microbiology, PO Box 2455, Riyadh 11451, Saudi Arabia.
Alexandria University, Faculty of Agriculture (EL-Shatby), Department of Forestry and Wood Technology, Alexandria, Egypt.
J AOAC Int. 2017 Jan 1;100(1):152-158. doi: 10.5740/jaoacint.16-0139. Epub 2016 Oct 19.
Multidrug-resistant (MDR) Acinetobacter baumannii infections are a great public health concern and demand continuous surveillance and antibiotic stewardship. Virulence traits and the pathogenicity of Acinetobacter are less studied compared with the molecular epidemiological and antibiotic resistance profile of this organism. In our present study, we investigated the primary characteristics contributing to the virulence of MDR A. baumannii isolates and compared them with avirulent isolates. A total of 32 well-characterized MDR A. baumannii clinical isolates and 22 avirulent isolates from a healthy individual were subjected to multilocus sequence typing and polymerase chain reaction (PCR) for a variety of biofilm-associated genes. Additionally, a number of in vitro tests were performed to determine virulence properties. Isolates were found to relate to six sequence types (STs) in which the dominant sequence was ST557 in clinical isolates, followed by ST195 and ST208. However, ST557 and ST222 were absent in avirulent isolates. All STs belonged to clonal complex 2 and clonal lineage 2, which is considered to be a universal clone. PCR analysis showed that most clinical isolates were positive for biofilm-forming genes, such as csu and bap, and also carried pga and ompA genes, which were less common in avirulent isolates. Biofilm formation, phospholipase C production, hemolytic activity, and acinetobactin production occurred significantly more frequently in clinical isolates compared with avirulent isolates. Though A. baumannii clonal lineages showed common virulence traits, they differed in virulent phenotype expression. These findings further support previous studies indicating that A. baumannii is a versatile pathogen with an ability to acquire iron and survive in iron-limiting conditions, highlighting the acinetobactin-mediated iron acquisition mechanisms involved in the pathogenesis of A. baumannii infections.
多重耐药鲍曼不动杆菌感染是一个重大的公共卫生问题，需要持续监测和抗生素管理。与该菌的分子流行病学和抗生素耐药谱相比，不动杆菌的毒力特征和致病性研究较少。在我们目前的研究中，我们调查了导致多重耐药鲍曼不动杆菌分离株毒力的主要特征，并将它们与无毒力分离株进行比较。总共32株特征明确的多重耐药鲍曼不动杆菌临床分离株和22株来自健康个体的无毒力分离株接受了多位点序列分型和针对多种生物膜相关基因的聚合酶链反应（PCR）。此外，还进行了一些体外试验以确定毒力特性。分离株被发现与六种序列类型（STs）相关，其中临床分离株中占主导地位的序列是ST557，其次是ST195和ST208。然而，无毒力分离株中不存在ST557和ST222。所有STs都属于克隆复合体2和克隆谱系2，这被认为是一个通用克隆。PCR分析表明，大多数临床分离株的生物膜形成基因（如csu和bap）呈阳性，并且还携带pga和ompA基因，这些基因在无毒力分离株中不太常见。与无毒力分离株相比，临床分离株中生物膜形成、磷脂酶C产生、溶血活性和铁载体产生的发生频率明显更高。尽管鲍曼不动杆菌克隆谱系表现出共同的毒力特征，但它们在毒力表型表达上存在差异。这些发现进一步支持了先前的研究，表明鲍曼不动杆菌是一种具有在铁限制条件下获取铁并存活能力的多功能病原体，突出了铁载体介导的铁获取机制在鲍曼不动杆菌感染发病机制中的作用。
