Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.
Key Laboratory of Clinical Pharmacology of Antibiotics, Ministry of Health, Shanghai, China.
Front Cell Infect Microbiol. 2023 May 22;13:1186017. doi: 10.3389/fcimb.2023.1186017. eCollection 2023.
is an important pathogen causing upper and lower respiratory tract infections in children and other age groups. Macrolides are the recommended treatments of choice for infections. However, macrolide resistance in is increasing worldwide, which complicates the treatment strategies. The mechanisms of macrolide resistance have been extensively studied focusing on the mutations in and ribosomal proteins. Since the secondary treatment choice for pediatric patients is very limited, we decided to look for potential new treatment strategies in macrolide drugs and investigate possible new mechanisms of resistance. We performed an selection of mutants resistant to five macrolides (erythromycin, roxithromycin, azithromycin, josamycin, and midecamycin) by inducing the parent strain M129 with increasing concentrations of the drugs. The evolving cultures in every passage were tested for their antimicrobial susceptibilities to eight drugs and mutations known to be associated with macrolide resistance by PCR and sequencing. The final selected mutants were also analyzed by whole-genome sequencing. Results showed that roxithromycin is the drug that most easily induces resistance (at 0.25 mg/L, with two passages, 23 days), while with midecamycin it is most difficult (at 5.12 mg/L, with seven passages, 87 days). Point mutations C2617A/T, A2063G, or A2064C in domain V of were detected in mutants resistant to the 14- and 15-membered macrolides, while A2067G/C was selected for the 16-membered macrolides. Single amino acid changes (G72R, G72V) in ribosomal protein L4 emerged during the induction by midecamycin. Genome sequencing identified sequence variations in , , , , and in one of the () genes in the mutants. Mutants induced by the 14- or 15-membered macrolides were resistant to all macrolides, while those induced by the 16-membered macrolides (midecamycin and josamycin) remained susceptible to the 14- and 15-membered macrolides. In summary, these data demonstrated that midecamycin is less potent in inducing resistance than other macrolides, and the induced resistance is restrained to the 16-membered macrolides, suggesting a potential benefit of using midecamycin as a first treatment choice if the strain is susceptible.
是导致儿童和其他年龄段上、下呼吸道感染的重要病原体。大环内酯类药物是治疗 的首选治疗方法。然而， 的大环内酯类药物耐药性在全球范围内不断增加，这使得治疗策略变得复杂。大环内酯类药物耐药性的机制已被广泛研究，主要集中在 和核糖体蛋白的突变上。由于儿科患者的二线治疗选择非常有限，我们决定在大环内酯类药物中寻找潜在的新治疗策略，并研究可能的新耐药机制。我们通过用药物逐渐增加浓度的方法诱导亲本 M129 菌株，对 5 种大环内酯类药物（红霉素、罗红霉素、阿奇霉素、交沙霉素和麦迪霉素）耐药的突变体进行了 选择。在每一轮中，进化培养物都通过 PCR 和测序检测了对 8 种药物的抗菌药敏性和与大环内酯类药物耐药相关的已知突变。最终选择的突变体也通过全基因组测序进行了分析。结果表明，罗红霉素最容易诱导耐药（在 0.25mg/L 时，经过 2 个传代，23 天），而麦迪霉素最难诱导耐药（在 5.12mg/L 时，经过 7 个传代，87 天）。在对 14 元和 15 元大环内酯类药物耐药的突变体中检测到 结构域 V 中的 C2617A/T、A2063G 或 A2064C 点突变，而对 16 元大环内酯类药物耐药的突变体中检测到 A2067G/C 点突变。在麦迪霉素诱导过程中，核糖体蛋白 L4 中出现了单个氨基酸变化（G72R、G72V）。全基因组测序鉴定了突变体中 、 、 、 和一个 （ ）基因的序列变异。由 14 元或 15 元大环内酯类药物诱导的突变体对所有大环内酯类药物均耐药，而由 16 元大环内酯类药物（麦迪霉素和交沙霉素）诱导的突变体对 14 元和 15 元大环内酯类药物仍敏感。总之，这些数据表明，麦迪霉素诱导耐药的能力比其他大环内酯类药物弱，而且诱导的耐药性仅限于 16 元大环内酯类药物，这表明如果菌株敏感，使用麦迪霉素作为一线治疗选择可能具有潜在益处。
