ABSTRACT

Global dissemination of the Neisseria gonorrhoeae ceftriaxone-resistant FC428 clone jeopardizes the currently recommended ceftriaxone-based first-line therapies. Ceftriaxone resistance in the FC428 clone has been associated with the presence of its mosaic penA allele 60.001. Here we investigated the contribution penA allele 60.001 to ceftriaxone resistance and its impact on biological fitness. Gonococcal isolates expressing penA allele 60.001 and mosaic penA allele 10.001, which is widespread in the Asia-Pacific region and associated with reduced susceptibility to ceftriaxone and cefixime, were genetic engineered to exchange their penA alleles. Subsequent antimicrobial susceptibility analyses showed that mutants containing penA 60.001 displayed 8- to 16-fold higher ceftriaxone and cefixime minimal inhibitory concentrations (MICs) compared with otherwise isogenic mutants containing penA 10.001. Further analysis of biological fitness showed that in vitro liquid growth of single strains and in the competition was identical between the isogenic penA allele exchange mutants. However, in the presence of high concentrations of palmitic acid or lithocholic acid, the penA 60.001-containing mutants grew better than the isogenic penA 10.001-containing mutants when grown as single strains. In contrast, the penA 10.001 mutants outcompeted the penA 60.001 mutants when grown in competition at slightly lower palmitic acid or lithocholic acid concentrations. Finally, the penA 60.001 mutants were outcompeted by their penA 10.001 counterparts for in vivo colonization and survival in a mouse vaginal tract infection model. In conclusion, penA allele 60.001 is essential for ceftriaxone resistance of the FC428 clone, while its impact on biological fitness is dependent on the specific growth conditions.

摘要

淋病奈瑟菌头孢曲​​松耐药 FC428 克隆的全球传播危及目前推荐的基于头孢曲松的一线疗法。FC428 克隆中的头孢曲松耐药性与其嵌合penA等位基因 60.001的存在有关。在这里，我们研究了penA等位基因 60.001 对头孢曲松耐药性的贡献及其对生物适应性的影响。表达penA等位基因 60.001 和镶嵌penA等位基因 10.001 的淋球菌分离株在亚太地区广泛存在，并与头孢曲松和头孢克肟敏感性降低相关，经过基因工程改造以交换其penA等位基因。随后的抗菌敏感性分析表明，与含有penA 10.001 的其他同基因突变体相比，含有penA 60.001 的突变体表现出的头孢曲松和头孢克肟最低抑菌浓度 (MIC) 高 8 至 16 倍。进一步的生物适应性分析表明，单菌株的体外液体生长和在同基因penA等位基因交换突变体之间的竞争是相同的。然而，在高浓度棕榈酸或石胆酸存在下，当作为单一菌株生长时，含有penA 60.001的突变体比含有同基因penA 10.001的突变体生长得更好。相反，当在略低的棕榈酸或石胆酸浓度下竞争生长时，penA 10.001突变体在竞争中胜过penA 60.001突变体。最后，在小鼠阴道感染模型中，penA 60.001 突变体在体内定植和存活方面被其penA 10.001 对应物击败。总之，penA等位基因60.001对于FC428克隆的头孢曲松抗性至关重要，而其对生物适应性的影响取决于特定的生长条件。