Karah Nabil, Dwibedi Chinmay Kumar, Sjöström Karin, Edquist Petra, Johansson Anders, Wai Sun Nyunt, Uhlin Bernt Eric
Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden, and Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden.
Antimicrob Agents Chemother. 2016 Jan 11;60(3):1801-18. doi: 10.1128/AAC.02143-15.
Acinetobacter baumannii has emerged as an important opportunistic pathogen equipped with a growing number of antibiotic resistance genes. Our study investigated the molecular epidemiology and antibiotic resistance features of 28 consecutive carbapenem-resistant clinical isolates of A. baumannii collected throughout Sweden in 2012 and 2013. The isolates mainly belonged to clonal complexes (CCs) with an extensive international distribution, such as CC2 (n = 16) and CC25 (n = 7). Resistance to carbapenems was related to blaOXA-23 (20 isolates), blaOXA-24/40-like (6 isolates), blaOXA-467 (1 isolate), and ISAba1-blaOXA-69 (1 isolate). Ceftazidime resistance was associated with blaPER-7 in the CC25 isolates. Two classical point mutations were responsible for resistance to quinolones in all the isolates. Isolates with high levels of resistance to aminoglycosides carried the 16S rRNA methylase armA gene. The isolates also carried a variety of genes encoding aminoglycoside-modifying enzymes. Several novel structures involved in aminoglycoside resistance were identified, including Tn6279, ΔTn6279, Ab-ST3-aadB, and different assemblies of Tn6020 and TnaphA6. Importantly, a number of circular forms related to the IS26 or ISAba125 composite transposons were detected. The frequent occurrence of these circular forms in the populations of several isolates indicates a potential role of these circular forms in the dissemination of antibiotic resistance genes.
鲍曼不动杆菌已成为一种重要的机会性病原体，携带越来越多的抗生素耐药基因。我们的研究调查了2012年和2013年在瑞典各地收集的28株连续的耐碳青霉烯类鲍曼不动杆菌临床分离株的分子流行病学和抗生素耐药特征。这些分离株主要属于具有广泛国际分布的克隆复合体（CCs），如CC2（n = 16）和CC25（n = 7）。对碳青霉烯类的耐药性与blaOXA - 23（20株）、blaOXA - 24/40样（6株）、blaOXA - 467（1株）和ISAba1 - blaOXA - 69（1株）有关。CC25分离株中头孢他啶耐药性与blaPER - 7有关。所有分离株中两个经典的点突变导致对喹诺酮类耐药。对氨基糖苷类具有高水平耐药性的分离株携带16S rRNA甲基化酶armA基因。这些分离株还携带多种编码氨基糖苷类修饰酶的基因。鉴定出了几种与氨基糖苷类耐药相关的新结构，包括Tn6279、ΔTn6279、Ab - ST3 - aadB以及Tn6020和TnaphA6的不同组合。重要的是，检测到了一些与IS26或ISAba125复合转座子相关的环状形式。这些环状形式在多个分离株群体中的频繁出现表明这些环状形式在抗生素耐药基因传播中可能发挥作用。
