Supplementary Material for: Evidence of Interruption of the comM Gene in a Large Series of Clinical Isolates of Multidrug-Resistant Acinetobacter baumannii

Recent studies have recognized the ATPase-encoding comM gene as a hot spot for the integration of Acinetobacter baumannii resistance islands (RIs). Despite the circulation of high numbers of multidrug-resistant A. baumannii (MDR-AB) isolates in Middle East countries, no information is available about the interruption of comM and subsequent transposition into comM in isolates belonging to the global clones (GC) GC1, GC2, or GC3. In this study 401 A. baumannii isolates from hospitals in Tehran, Iran, were included. The resistance profile was determined by disc diffusion against 22 antibiotics. PCR was used to assess the GC type, presence of the comM gene, and the boundary junctions (J1 and J2) of RIs. Most of the MDR-AB isolates (384 of 388; 98%) and more than half of the susceptible A. baumannii isolates (9 of 13; 69%) had interrupted comM gene-carrying integrative elements. Among the isolates tested, 57 belonged to GC1, 86 to GC2, and 8 to GC3. A set of 250 isolates showed distinct patterns of allele-specific PCR for ompA, csuE, and blaOXA-51-like genes. All but 2 of the GC1 isolates and 2 of the GC2 isolates contained interrupted comM genes. Four A. baumannii isolates harbored intact comM, but were multiply resistant to antibiotics. This study demonstrated that the comM gene is targeted by transposons in Iranian MDR-AB isolates belonging to different GCs. The data also showed that the carriage of interrupted comM is not exclusive to MDR isolates of A. baumannii.近期研究已证实，编码ATP酶的comM基因（ATPase-encoding comM gene）是鲍曼不动杆菌（Acinetobacter baumannii）耐药岛（resistance islands, RIs）整合的热点区域。尽管中东国家广泛流行大量多重耐药鲍曼不动杆菌（multidrug-resistant A. baumannii, MDR-AB）分离株，但目前尚无针对隶属于全球克隆（global clones, GC）GC1、GC2或GC3的分离株中comM基因被打断并随后发生转座插入comM位点的相关研究报道。本研究纳入了来自伊朗德黑兰多家医院的401株鲍曼不动杆菌分离株。采用纸片扩散法对22种抗生素进行药敏试验以确定其耐药谱型；通过聚合酶链式反应（polymerase chain reaction, PCR）鉴定分离株的全球克隆型、comM基因的存在情况以及耐药岛的边界连接区（J1和J2）。受试分离株中，388株多重耐药鲍曼不动杆菌分离株里的384株（占比98%），以及13株药敏敏感鲍曼不动杆菌分离株中的9株（占比69%），均携带带有被打断的comM基因的整合元件。受试分离株中，57株隶属于GC1，86株隶属于GC2，8株隶属于GC3；另有250株分离株的ompA、csuE以及blaOXA-51样基因的等位基因特异性PCR（allele-specific PCR）图谱存在差异。所有GC1型分离株（仅2株除外）以及2株GC2型分离株均携带被打断的comM基因。另有4株鲍曼不动杆菌分离株携带完整的comM基因，但仍表现出多重耐药表型。本研究证实，隶属于不同全球克隆型的伊朗多重耐药鲍曼不动杆菌分离株中，comM基因均为转座子的靶向整合位点；同时研究数据表明，携带被打断的comM基因并非多重耐药鲍曼不动杆菌所特有。