The prevalence of polymyxin-resistant Enterobacteriaceae is increasing worldwide. Their emergence is worrisome and limits therapeutic options for severely ill patients. We aimed to investigate the molecular and epidemiological characteristics of polymyxin-resistant Klebsiella pneumoniae circulating in Brazilian hospitals. Polymyxin-resistant K. pneumoniae isolates from two Brazilian healthcare facilities were characterized phenotypically and subjected to whole genome sequencing (WGS). Using the WGS data we determined their sequence type, resistance gene content (resistome), their composition of virulence genes and plasmids. ST11 was the most common (80 %) sequence type among the isolates followed by ST345, ST15 and ST258. A resistome analysis revealed the common presence of bla_KPC-2 and less frequently bla_SHV-11, bla_TEM-1, bla_CTX-M-15, and bla_OXA-9. Genes conferring resistance to aminoglycosides, fluoroquinolones, phenicols, sulphonamides, tetracyclines, trimethoprim and macrolide-lincosamide-streptogramin were also detected. We observed a clonal spread of polymyxin-resistant K. pneumoniae isolates, with polymyxin-resistance associated with various alterations in the mgrB gene including inactivation by an insertion sequence and nonsense point mutations. We additionally identified a novel 78-bp repeat sequence, encoding a MgrB protein with 26 amino acids duplicated in six isolates. This is the first observation of this type of alteration being associated with polymyxin resistance. Our findings demonstrate that mgrB alterations were the most common source of polymyxin-resistance in Brazilian clinical settings. Interestingly, distinct genetic events were identified among clonally related isolates, including a new amino acid alteration. The clinical implications and investigation of the resistance mechanisms is of great importance to patient safety and control of these infections, particularly in long-term care facilities.

在世界范围内，对多粘菌素耐药的肠杆菌科的患病率正在上升。它们的出现令人担忧，并且限制了重症患者的治疗选择。我们旨在调查在巴西医院中传播的对多粘菌素耐药的肺炎克雷伯菌的分子和流行病学特征。耐多粘菌性肺炎克雷伯菌对来自两个巴西医疗机构的分离株进行表型鉴定，并进行全基因组测序（WGS）。使用WGS数据，我们确定了它们的序列类型，抗性基因含量（抗性基因组），毒力基因和质粒的组成。在分离株中，ST11是最常见的序列类型（80％），其次是ST345，ST15和ST258。电阻组分析显示bla _KPC-2的普遍存在，而bla _SHV-11，bla _TEM-1，bla _CTX-M-15和bla _OXA-9的出现频率较低。还检测到了对氨基糖苷类，氟喹诺酮类，酚类，磺酰胺类，四环素类，甲氧苄啶和大环内酯-林可酰胺-链霉菌素具有抗性的基因。我们观察到多粘菌抗性肺炎克雷伯菌分离株的克隆传播，与多粘菌抗性与mgrB基因的各种变化有关，包括通过插入序列失活和无意义的点突变。我们还确定了一个新颖的78 bp重复序列，该序列编码一个MgrB蛋白，在六个分离物中重复了26个氨基酸。这是这种与多粘菌素抗性相关的改变的首次观察。我们的发现表明，mgrB改变是巴西临床环境中最常见的多粘菌素耐药性来源。有趣的是，在克隆相关的分离物中鉴定出不同的遗传事件，包括新的氨基酸改变。抗药性机制的临床意义和研究对患者安全和这些感染的控制非常重要，尤其是在长期护理机构中。