AUTHOR=Liu Fei , Chen Sijie , Zou Yingxin , Jiao Yong , Tang Ying 

TITLE=A simple and efficient fluorescent labeling method in Staphylococcus aureus for real-time tracking of invasive bacteria

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1128638

DOI=10.3389/fmicb.2023.1128638

ISSN=1664-302X

ABSTRACT=<p>Bacterial fluorescent labeling is a powerful tool for the diagnosis and treatment of bacterial infections. Here, we present a simple and efficient labeling strategy for <italic>Staphylococcus aureus</italic>. Intracellular labeling of bacteria was achieved by heat shock using Cyanine 5.5 (Cy5.5) near-infrared-I dyes in <italic>S. aureus</italic> (<italic>Cy5.5@S. aureus</italic>). Several key factors, such as Cy5.5 concentration and labeling time, were systematically evaluated. Further, the cytotoxicity of Cy5.5 and the stability of <italic>Cy5.5@S. aureus</italic> was evaluated by flow cytometry, inverted fluorescence microscopy, and transmission electron microscopy. In addition, <italic>Cy5.5@S. aureus</italic> were used to explore the phagocytic behavior of RAW264.7 macrophages. These results proved that <italic>Cy5.5@S. aureus</italic> had a uniform fluorescence intensity and high luminance; additionally, our method had no significant adverse effects on <italic>S. aureus</italic> compared to unlabeled <italic>S. aureus</italic> infections. Our method provides researchers with a useful option for analyzing the behavior of <italic>S. aureus</italic> as an infectious agent. This technique can be broadly applied to study host cell–bacteria interactions at the molecular level, and to <italic>in vivo</italic> tracing of bacterial infections.</p>