Sánchez-León Irene, García-Martínez Teresa, Diene Seydina M, Pérez-Nadales Elena, Martínez-Martínez Luis, Rolain Jean-Marc
Maimonides Biomedical Research Institute of Cordoba, 14004 Cordoba, Spain.
Department of Agricultural Chemistry, Edaphology and Microbiology, Agrifood Campus of International Excellence CeiA3, University of Cordoba, 14014 Cordoba, Spain.
Antibiotics (Basel). 2023 Jun 27;12(7):1111. doi: 10.3390/antibiotics12071111.
Heteroresistance to colistin can be defined as the presence of resistant subpopulations in an isolate that is susceptible to this antibiotic. Colistin resistance in Gram-negative bacteria is more frequently related to chromosomal mutations and insertions. This work aimed to study heteroresistance in nine clinical isolates of producing OXA-48 and to describe genomic changes in mutants with acquired resistance in vitro. Antimicrobial susceptibility was determined by broth microdilution (BMD) and heteroresistance by population analysis profiling (PAP). The proteins related to colistin resistance were analyzed for the presence of mutations. Additionally, PCR of the B gene was performed to identify the presence of insertions. In the nine parental isolates, the PAP method showed colistin heteroresistance of colonies growing on plates with concentrations of up to 64 mg/L, corresponding to stable mutant subpopulations. The MICs of some mutants from the PAP plate containing 4×MIC of colistin had absolute values of ≤2 mg/L that were higher than the parental MICs and were defined as persistent variants. PCR of the B gene identified an insertion sequence that inactivated the gene in 21 mutants. Other substitutions in the investigated mutants were found in PhoP, PhoQ, PmrB, PmrC, CrrA and CrrB proteins. Colistin heteroresistance in isolates was attributed mainly to insertions in the B gene and point mutations in colistin resistance proteins. The results of this study will improve understanding regarding the mechanisms of colistin resistance in mutants of producing OXA-48.
对黏菌素的异质性耐药可定义为在对该抗生素敏感的分离株中存在耐药亚群。革兰氏阴性菌中的黏菌素耐药性更常与染色体突变和插入有关。本研究旨在研究9株产OXA-48临床分离株中的异质性耐药，并描述体外获得性耐药突变体的基因组变化。通过肉汤微量稀释法（BMD）测定抗菌药物敏感性，通过群体分析谱（PAP）测定异质性耐药。分析与黏菌素耐药相关的蛋白质是否存在突变。此外，进行B基因的PCR以鉴定插入的存在。在9株亲本分离株中，PAP方法显示在浓度高达64 mg/L的平板上生长的菌落存在黏菌素异质性耐药，对应于稳定的突变亚群。来自含有4倍黏菌素MIC的PAP平板的一些突变体的MIC绝对值≤2 mg/L，高于亲本MIC，被定义为持续性变异株。B基因的PCR鉴定出一个插入序列，该序列在21个突变体中使该基因失活。在所研究的突变体中，还在PhoP、PhoQ、PmrB、PmrC、CrrA和CrrB蛋白中发现了其他替代。分离株中的黏菌素异质性耐药主要归因于B基因的插入和黏菌素耐药蛋白中的点突变。本研究结果将增进对产OXA-48突变体中黏菌素耐药机制的理解。
