Institute of Microbiology and Immunology, Medical Faculty, University of Belgrade, Doktora Subotica starijeg 1, Belgrade, 11000, Serbia.
Faculty of Biology, University of Belgrade, Belgrade, Serbia.
Antimicrob Resist Infect Control. 2020 Jul 6;9(1):101. doi: 10.1186/s13756-020-00769-8.
The worldwide emergence and clonal spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is of great concern. The aim of this nationwide study was to investigate the prevalence of CRAB isolates in Serbia and to characterize underlying resistance mechanisms and their genetic relatedness.
Non-redundant clinical samples obtained from hospitalized patients throughout Serbia were included in the prospective, observational, multicenter study conducted from January to June 2018. Samples were initially screened for the presence of Acinetobacter baumannii-calcoaceticus (Acb) complex using conventional bacteriological techniques. Acb complexes recovered from clinical samples obtained from inpatients with confirmed bacterial infections were further evaluated for the presence of A. baumannii. Identification to the species level was done by the detection of the bla gene and rpoB gene sequence analysis. Susceptibility testing was done by disk diffusion and broth microdilution method. CRAB isolates were tested for the presence of acquired carbapenemases (bla, blabla, bla, bla, bla, bla, bla, bla, bla) by PCR. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).
Acb complex was isolated in 280 out of 2401 clinical samples (11.6%). Overall, A. baumannii was identified in 237 out of 280 Acb complex (84.6%). CRAB prevalence was found to be 93.7% (237/222). The MIC/MIC for imipenem and meropenem were 8/> 32 μg/mL and 16/> 32 μg/mL, respectively. Although susceptibility was high for colistin (95.7%; n = 227) and tigecycline (75.1%; n = 178), ten isolates (4.3%) were classified as pandrug-resistant. The following carbapenemases-encoding genes were found: 98 (44.2%) bla, 76 (34.5%) bla, and 7 (3.2%) bla. PFGE analysis revealed six different clusters. MLST analysis identified three STs: ST2 (n = 13), ST492 (n = 14), and ST636 (n = 10). Obtained results evaluated that circulating CRAB clones in Serbia were as follows: bla/bla/ST2 (32.4%), bla/bla/bla/ST2 (2.7%), bla/bla/ST492 (37.8%), and bla/bla/ST636 (27.1%).
This study revealed extremely high proportions of carbapenem resistance among A. baumannii clinical isolates due to the emergence of bla, bla, and bla genes among CRAB isolates in Serbia and their clonal propagation.
碳青霉烯类耐药鲍曼不动杆菌（CRAB）在全球的出现和克隆传播令人高度关注。本全国性研究的目的是调查塞尔维亚 CRAB 分离株的流行情况，并对潜在的耐药机制及其遗传相关性进行特征分析。
2018 年 1 月至 6 月期间，采用前瞻性、观察性、多中心研究方法，纳入来自塞尔维亚住院患者的非冗余临床样本。采用常规细菌学技术对鲍曼不动杆菌-醋酸钙不动杆菌复合体（Acb）进行初步筛查。从确诊细菌感染住院患者的临床样本中分离出 Acb 复合体，进一步评估鲍曼不动杆菌的存在。通过 bla 基因和 rpoB 基因序列分析鉴定到种水平。通过纸片扩散法和肉汤微量稀释法进行药敏试验。采用 PCR 检测 CRAB 分离株是否存在获得性碳青霉烯酶（bla、bla、bla、bla、bla、bla、bla、bla、bla）。通过脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）评估克隆相关性。
在 2401 份临床样本中分离出 Acb 复合体 280 株（11.6%）。总体而言，280 株 Acb 复合体中有 237 株（84.6%）鉴定为鲍曼不动杆菌。CRAB 的流行率为 93.7%（237/222）。亚胺培南和美罗培南的 MIC/MIC 值分别为 8/>32μg/mL 和 16/>32μg/mL。尽管多粘菌素（95.7%；n=227）和替加环素（75.1%；n=178）的敏感性较高，但有 10 株（4.3%）被归类为泛耐药。发现了以下碳青霉烯酶编码基因：98 株（44.2%）bla、76 株（34.5%）bla 和 7 株（3.2%）bla。PFGE 分析显示 6 个不同的簇。MLST 分析确定了 3 个 ST 型：ST2（n=13）、ST492（n=14）和 ST636（n=10）。研究结果表明，塞尔维亚流行的 CRAB 克隆如下：bla/bla/ST2（32.4%）、bla/bla/bla/ST2（2.7%）、bla/bla/ST492（37.8%）和 bla/bla/ST636（27.1%）。
本研究揭示了塞尔维亚 CRAB 分离株中由于 bla、bla 和 bla 基因的出现及其克隆传播，导致碳青霉烯类耐药的极高比例。
