Generation and Characterization of Stable Small Colony Variants of USA300 <i>Staphylococcus aureus</i> in RAW 264.7 Murine Macrophages

• Main Authors: Dalida Bivona (Author), Carmelo Bonomo (Author), Lorenzo Colombini (Author), Paolo G. Bonacci (Author), Grete F. Privitera (Author), Giuseppe Caruso (Author), Filippo Caraci (Author), Francesco Santoro (Author), Nicolò Musso (Author), Dafne Bongiorno (Author), Francesco Iannelli (Author), Stefania Stefani (Author)
• Format: Book
• Published: MDPI AG, 2024-03-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

Intracellular survival and immune evasion are typical features of staphylococcal infections. USA300 is a major clone of methicillin-resistant <i>S. aureus</i> (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 <i>S. aureus</i> 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 <i>aroK</i>. Gene expression analysis showed a significant up-regulation of the <i>uhpt</i> and <i>sdrE</i> genes in the stable SCVs compared with the wild-type, likely involved in adaptation to the intracellular <i>milieu</i>.

Item Description

10.3390/antibiotics13030264
2079-6382