Background MRSA are high-priority multidrug-resistant pathogens. Although there are still some antibiotics active against MRSA, continuous efforts to discover new antibiotics and treatment strategies are needed because resistance to these new drugs has already been reported. Objectives Here we explore if d-alanylation of teichoic acids (TAs) mediated by the dlt operon gene products might be a druggable target to overcome β-lactam-resistance of MRSA. Methods MICs and bactericidal effects of several β-lactam antibiotics were monitored in a panel of clinical MRSA strains with genetic or chemically induced deficiency in d-alanylation of TAs. Efficiency of the chemical inhibitor to rescue MRSA-infected larvae of Galleria mellonella as well as its ability to prevent or eradicate biofilms of S. aureus were analysed. Results Genetic inactivation of the Dlt system or its chemical inhibition re-sensitizes MRSA to β-lactams. Among the 13 strains, the most pronounced effect was obtained using the inhibitor with imipenem, reducing the median MIC from 16 to 0.25 mg/L. This combination was also bactericidal in some strains and significantly protected G. mellonella larvae from lethal MRSA infections. Finally, inactivation of d-alanylation potentiated the effect of imipenem on inhibition and/or eradication of biofilm. Conclusions Our combined results show that highly efficient inhibitors of d-alanylation of TAs targeting enzymes of the Dlt system should be promising therapeutic adjuvants, especially in combination with carbapenems, for restoring the therapeutic efficacy of this class of antibiotics against MRSA.

中文翻译：

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抑制磷壁酸的d-丙氨酰化克服耐甲氧西林金黄色葡萄球菌的耐药性

背景 MRSA 是高度优先的多重耐药病原体。尽管仍有一些抗生素对 MRSA 有活性，但仍需要不断努力发现新的抗生素和治疗策略，因为已经报道了对这些新药的耐药性。目的 在这里，我们探讨由 dlt 操纵子基因产物介导的磷壁酸 (TAs) 的 d-丙氨酰化是否可能成为克服 MRSA 对 β-内酰胺类耐药的药物靶点。方法 在一组临床 MRSA 菌株中监测几种 β-内酰胺类抗生素的 MIC 和杀菌效果，这些菌株具有遗传或化学诱导的 TAs d-丙氨酰化缺陷。分析了化学抑制剂拯救受 MRSA 感染的大麦氏菌幼虫的效率以及其预防或根除金黄色葡萄球菌生物膜的能力。结果 Dlt 系统的遗传失活或其化学抑制使 MRSA 对 β-内酰胺重新敏感。在 13 株菌株中，使用抑制剂与亚胺培南的效果最为显着，将 MIC 中值从 16 降至 0.25 mg/L。这种组合在某些菌株中也具有杀菌作用，并显着保护 G. mellonella 幼虫免受致命的 MRSA 感染。最后，d-丙氨酰化的失活增强了亚胺培南对抑制和/或消除生物膜的作用。结论 我们的综合结果表明，靶向 Dlt 系统酶的 TAs 的 d-丙氨酰化的高效抑制剂应该是有希望的治疗佐剂，特别是与碳青霉烯类组合，以恢复这类抗生素对 MRSA 的治疗效果。