PDF(Pubmed)
Abstract：
The emergence of Neisseria gonorrhoeae strains resistant to extended-spectrum cephalosporins (ESCs) is a worldwide concern because this class of antibiotics represents the last empirical treatment option for gonorrhea. The abusive use of antimicrobials may be an essential factor for the emergence of ESC resistance in N. gonorrhoeae. Cephalosporin resistance mechanisms have not been fully clarified. In this study, we mapped mutations in the genome of N. gonorrhoeae isolates after resistance induction with cefixime and explored related metabolic pathways. Six clinical isolates with different antimicrobial susceptibility profiles and genotypes and two gonococcal reference strains (WHO F and WHO Y) were induced with increasing concentrations of cefixime. Antimicrobial susceptibility testing was performed against six antimicrobial agents before and after induction. Clinical isolates were whole-genome sequenced before and after induction, whereas reference strains were sequenced after induction only. Cefixime resistance induction was completed after 138 subcultures. Several metabolic pathways were affected by resistance induction. Five isolates showed SNPs in PBP2. The isolates M111 and M128 (ST1407 with mosaic penA-34.001) acquired one and four novel missense mutations in PBP2, respectively. These isolates exhibited the highest minimum inhibitory concentration (MIC) for cefixime among all clinical isolates. Mutations in genes contributing to ESC resistance and in other genes were also observed. Interestingly, M107 and M110 (ST338) showed no mutations in key determinants of ESC resistance despite having a 127-fold increase in the MIC of cefixime. These findings point to the existence of different mechanisms of acquisition of ESC resistance induced by cefixime exposure. Furthermore, the results reinforce the importance of the gonococcal antimicrobial resistance surveillance program in Brazil, given the changes in treatment protocols made in 2017 and the nationwide prevalence of sequence types that can develop resistance to ESC.
摘要：
对广谱头孢菌素（ESC）具有抗性的淋病奈瑟菌菌株的出现是全世界关注的问题，因为此类抗生素代表了淋病的最后经验治疗选择。滥用抗菌药物可能是淋病奈瑟菌出现ESC耐药性的重要因素。头孢菌素耐药机制尚未完全阐明。在这项研究中,我们对头孢克肟诱导耐药后的淋病奈瑟菌基因组中的突变进行了定位,并探索了相关的代谢途径.随着头孢克肟浓度的增加，诱导了六个具有不同抗菌药物敏感性和基因型的临床分离株和两个淋球菌参考菌株（WHOF和WHOY）。在诱导前后对六种抗菌剂进行了抗菌药物敏感性测试。临床分离株在诱导前后进行全基因组测序,而参考菌株仅在诱导后进行测序。在138次继代培养后完成头孢克肟抗性诱导。几种代谢途径受到抗性诱导的影响。五个分离株显示PBP2中的SNP。分离株M111和M128（带有镶嵌penA-34.001的ST1407）分别在PBP2中获得了一个和四个新的错义突变。这些分离株在所有临床分离株中对头孢克肟表现出最高的最小抑制浓度(MIC)。还观察到导致ESC抗性的基因和其他基因的突变。有趣的是,尽管头孢克肟的MIC增加127倍,但M107和M110(ST338)在ESC抗性的关键决定因子中没有显示突变。这些发现指出了头孢克肟暴露诱导的ESC抗性获得的不同机制的存在。此外，结果加强了巴西淋球菌抗菌素耐药性监测计划的重要性，考虑到2017年治疗方案的变化以及可能对ESC产生耐药性的序列类型在全国范围内的流行。
