Peykov Slavil, Stratev Alexander, Kirov Boris, Gergova Raina, Strateva Tanya
1Department of Genetics, Faculty of Biology, Sofia University "St. Kliment Ohridski", Sofia, Bulgaria.
2BioInfoTech Laboratory, Sofia Tech Park, Sofia, Bulgaria.
Acta Microbiol Immunol Hung. 2022 Aug 29;69(3):209-214. doi: 10.1556/030.2022.01833. Print 2022 Sep 16.
Colistin is considered as the last-line antibiotic for the treatment of infections caused by extensively drug-resistant Gram-negative pathogens belonging to the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) group. The present study aimed to explore the colistin resistance mechanisms of a Klebsiella aerogenes (formerly Enterobacter aerogenes) isolate (Kae1177-1bg) obtained from a Bulgarian critically ill patient with septic shock in 2020. Antimicrobial susceptibility testing and whole-genome sequencing using DNA nanoball technology were performed. The resulting read pairs were used for draft genome assembly, MLST analysis and mutation screening in the pmrA/B, phoP/Q, and mgrB genes. Kae1177-1bg demonstrated high-level resistance to colistin, resistance to 3rd generation cephalosporins and susceptibility to all other antibiotics tested. In our strain a CMY-2-type class C cephalosporinase was the only β-lactamase identified. No mobile colistin resistance (mcr) genes were detected. A total of three missense variants in the genes for the two-component PmrA/PmrB system were identified. Two of them were located in the pmrB (pR57K and pN275K) and one in the pmrA gene (pL162M). The pN275K variant emerged as the most likely cause for colistin resistance because it affected a highly conservative position and was the only nonconservative amino acid substitution. In conclusion, to the best of our knowledge, this is the first documented clinical case of a high-level colistin-resistant K. aerogenes in Bulgaria and the first identification of the nonconservative amino acid substitution pN275K worldwide. Colistin-resistant Gram-negative pathogens of ESKAPE group are serious threat to public health and should be subjected to infection control stewardship practices.
黏菌素被认为是治疗由属于ESKAPE（粪肠球菌、金黄色葡萄球菌、肺炎克雷伯菌、鲍曼不动杆菌、铜绿假单胞菌和肠杆菌属）组的广泛耐药革兰氏阴性病原体引起的感染的最后一线抗生素。本研究旨在探索2020年从一名患有感染性休克的保加利亚重症患者中分离出的产气克雷伯菌（原产气肠杆菌）菌株（Kae1177-1bg）的黏菌素耐药机制。进行了抗菌药敏试验和使用DNA纳米球技术的全基因组测序。所得的读段对用于草图基因组组装、多位点序列分型分析以及pmrA/B、phoP/Q和mgrB基因的突变筛查。Kae1177-1bg对黏菌素表现出高水平耐药，对第三代头孢菌素耐药，对所有其他测试抗生素敏感。在我们的菌株中，CMY-2型C类头孢菌素酶是唯一鉴定出的β-内酰胺酶。未检测到可移动黏菌素耐药（mcr）基因。在双组分PmrA/PmrB系统的基因中总共鉴定出三个错义变体。其中两个位于pmrB（pR57K和pN275K），一个位于pmrA基因（pL162M）。pN275K变体成为黏菌素耐药最可能的原因，因为它影响了一个高度保守的位置，并且是唯一的非保守氨基酸替代。总之，据我们所知，这是保加利亚首例有记录的高水平黏菌素耐药产气克雷伯菌临床病例，也是全球首次鉴定出非保守氨基酸替代pN275K。ESKAPE组的耐黏菌素革兰氏阴性病原体对公共卫生构成严重威胁，应实施感染控制管理措施。
