Bivona Dalida, Bonomo Carmelo, Colombini Lorenzo, Bonacci Paolo G, Privitera Grete F, Caruso Giuseppe, Caraci Filippo, Santoro Francesco, Musso Nicolò, Bongiorno Dafne, Iannelli Francesco, Stefani Stefania
Medical Molecular Microbiology and Antibiotic Resistance Laboratory (MMARLab), Department of Biomedical and Biotechnological Sciences (BIOMETEC), University of Catania, 95123 Catania, Italy.
Laboratory of Molecular Microbiology and Biotechnology, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy.
Antibiotics (Basel). 2024 Mar 16;13(3):264. doi: 10.3390/antibiotics13030264.
Intracellular survival and immune evasion are typical features of staphylococcal infections. USA300 is a major clone of methicillin-resistant (MRSA), a community- and hospital-acquired pathogen capable of disseminating throughout the body and evading the immune system. Carnosine is an endogenous dipeptide characterized by antioxidant and anti-inflammatory properties acting on the peripheral (macrophages) and tissue-resident (microglia) immune system. In this work, RAW 264.7 murine macrophages were infected with the USA300 ATCC BAA-1556 strain and treated with 20 mM carnosine and/or 32 mg/L erythromycin. Stable small colony variant (SCV) formation on blood agar medium was obtained after 48 h of combined treatment. Whole genome sequencing of the BAA-1556 strain and its stable derivative SCVs when combining Illumina and nanopore technologies revealed three single nucleotide differences, including a nonsense mutation in the shikimate kinase gene . Gene expression analysis showed a significant up-regulation of the and genes in the stable SCVs compared with the wild-type, likely involved in adaptation to the intracellular .
细胞内存活和免疫逃逸是葡萄球菌感染的典型特征。USA300是耐甲氧西林金黄色葡萄球菌（MRSA）的一个主要克隆株，这是一种可在社区和医院获得的病原体，能够在全身扩散并逃避免疫系统。肌肽是一种内源性二肽，具有抗氧化和抗炎特性，作用于外周（巨噬细胞）和组织驻留（小胶质细胞）免疫系统。在这项研究中，用USA300 ATCC BAA - 1556菌株感染RAW 264.7小鼠巨噬细胞，并用20 mM肌肽和/或32 mg/L红霉素进行处理。联合处理48小时后，在血琼脂培养基上获得了稳定的小菌落变体（SCV）形成。结合Illumina和纳米孔技术对BAA - 1556菌株及其稳定衍生物SCV进行全基因组测序，发现了三个单核苷酸差异，包括莽草酸激酶基因中的一个无义突变。基因表达分析表明，与野生型相比，稳定SCV中的某些基因显著上调，可能参与了对细胞内环境的适应。
