Cassu-Corsi Dandara, Martins Willames Mbs, Nicoletti Adriana G, Almeida Luiz Gp, Vasconcelos Ana Tr, Gales Ana C
Universidade Federal de São Paulo, Escola Paulista de Medicina, Departamento de Medicina Interna, Divisão de Doenças Infecciosas, Laboratório Alerta, São Paulo, SP, Brasil.
Laboratório Nacional de Computação Científica, Petrópolis, RJ, Brasil.
Mem Inst Oswaldo Cruz. 2018 Dec 10;113(12):e180392. doi: 10.1590/0074-02760180392.
OBJECTIVES The emergence of 16S rRNA methyltranferases (16 RMTAses) has jeopardised the clinical use of aminoglycosides. RmtB is one of the most frequently reported in Gram-negatives worldwide. In this study, we aimed to estimate the frequency of 16S RMTAses encoding genes in Enterobacteriaceae isolated in a three-month period from a tertiary Brazilian hospital. METHODS All Gram-negatives classified as resistant to amikacin, gentamicin, and tobramycin by agar screening were selected for analysis. The presence of 16SRMTases encoding genes was verified by polymerase chain reaction (PCR). Antimicrobial susceptible profile was determined by broth microdilution. The genetic relationship among these isolates was accessed by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Selected RmtB-producing isolates were characterised by whole genome sequencing (WGS) analysis. RESULTS Twenty-two of 1,052 (2.1%) Enterobacteriaceae were detected as producers of RmtB-1 [Klebsiella pneumoniae (n = 21) and Proteus mirabilis (n = 1)]. blaKPC-2 was identified among 20 RmtB-1-producing K. pneumoniae isolates that exhibited an identical PFGE and MLST (ST258) patterns. Two K. pneumoniae isolates, the A64216 (not harboring bla KPC-2), A64477 (harboring bla KPC-2) and one P. mirabilis isolate (A64421) were selected for WGS. rmtB-1 and bla KPC-2 genes were carried by distinct plasmids. While a plasmid belonging to the IncFIIk group harbored rmtB-1 in K. pneumoniae, this gene was carried by a non-typable plasmid in P. mirabilis. In the three analysed plasmids, rmtB-1 was inserted on a transposon, downstream a Tn2. CONCLUSION Our findings suggested that the rmtB-1 was harbored by plasmids distinct from those previously reported in Bolivia and China. It suggests that multiple mobilization events might have occurred in South America.
目的 16S rRNA甲基转移酶（16RMTAses）的出现危及了氨基糖苷类药物的临床应用。RmtB是全球革兰氏阴性菌中最常报道的一种。在本研究中，我们旨在估计巴西一家三级医院在三个月内分离出的肠杆菌科细菌中16S RMTAses编码基因的频率。方法 选择所有经琼脂筛选对阿米卡星、庆大霉素和妥布霉素耐药的革兰氏阴性菌进行分析。通过聚合酶链反应（PCR）验证16SRMTases编码基因的存在。通过肉汤微量稀释法测定抗菌药物敏感性谱。通过脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）分析这些分离株之间的遗传关系。对选定的产RmtB分离株进行全基因组测序（WGS）分析。结果 在1052株肠杆菌科细菌中，有22株（2.1%）被检测为RmtB-1的产生菌[肺炎克雷伯菌（n = 21）和奇异变形杆菌（n = 1）]。在20株产RmtB-1的肺炎克雷伯菌分离株中鉴定出blaKPC-2，这些分离株表现出相同的PFGE和MLST（ST258）模式。选择两株肺炎克雷伯菌分离株A64216（不携带bla KPC-2）、A64477（携带bla KPC-2）和一株奇异变形杆菌分离株（A64421）进行WGS。rmtB-1和bla KPC-2基因由不同的质粒携带。在肺炎克雷伯菌中，属于IncFIIk组的质粒携带rmtB-1，而在奇异变形杆菌中，该基因由一个不可分型的质粒携带。在分析的三个质粒中，rmtB-1插入在转座子上，位于Tn2的下游。结论 我们的研究结果表明，rmtB-1由与玻利维亚和中国先前报道的质粒不同的质粒携带。这表明南美洲可能发生了多次转移事件。
