Departments of Pediatrics, University of California, San Diego, California 92093, USA.
J Biol Chem. 2013 Mar 1;288(9):6417-26. doi: 10.1074/jbc.M112.448738. Epub 2013 Jan 15.
Staphylococcus aureus infections present an enormous global health concern complicated by an alarming increase in antibiotic resistance. S. aureus is among the few bacterial species that express nitric-oxide synthase (bNOS) and thus can catalyze NO production from L-arginine. Here we generate an isogenic bNOS-deficient mutant in the epidemic community-acquired methicillin-resistant S. aureus (MRSA) USA300 clone to study its contribution to virulence and antibiotic susceptibility. Loss of bNOS increased MRSA susceptibility to reactive oxygen species and host cathelicidin antimicrobial peptides, which correlated with increased MRSA killing by human neutrophils and within neutrophil extracellular traps. bNOS also promoted resistance to the pharmaceutical antibiotics that act on the cell envelope such as vancomycin and daptomycin. Surprisingly, bNOS-deficient strains gained resistance to aminoglycosides, suggesting that the role of bNOS in antibiotic susceptibility is more complex than previously observed in Bacillus species. Finally, the MRSA bNOS mutant showed reduced virulence with decreased survival and smaller abscess generation in a mouse subcutaneous infection model. Together, these data indicate that bNOS contributes to MRSA innate immune and antibiotic resistance phenotypes. Future development of specific bNOS inhibitors could be an attractive option to simultaneously reduce MRSA pathology and enhance its susceptibility to commonly used antibiotics.
金黄色葡萄球菌感染是一个巨大的全球健康问题，其复杂性在于抗生素耐药性的惊人增长。金黄色葡萄球菌是少数能够表达一氧化氮合酶（bNOS）并因此能够从 L-精氨酸催化 NO 产生的细菌物种之一。在这里，我们在流行的社区获得性耐甲氧西林金黄色葡萄球菌（MRSA）USA300 克隆中生成了一个同源 bNOS 缺陷突变体，以研究其对毒力和抗生素敏感性的贡献。NOS 的缺失增加了 MRSA 对活性氧和宿主抗菌肽的敏感性，这与人类中性粒细胞和中性粒细胞细胞外陷阱内 MRSA 的杀伤增加有关。NOS 还促进了对抗生素的耐药性，这些抗生素作用于细胞膜，如万古霉素和达托霉素。令人惊讶的是，NOS 缺陷株对氨基糖苷类药物产生了耐药性，这表明 bNOS 在抗生素敏感性中的作用比以前在芽孢杆菌属中观察到的更为复杂。最后，MRSA bNOS 突变体在小鼠皮下感染模型中的生存能力降低，脓肿生成减少，表明其毒力降低。综上所述，这些数据表明 bNOS 有助于 MRSA 的固有免疫和抗生素耐药表型。未来开发特异性 bNOS 抑制剂可能是一种有吸引力的选择，可以同时降低 MRSA 的病理学并增强其对常用抗生素的敏感性。
