Fluorescence Reporter in Staphylococcus aureus as a Useful Tool for Studying L-forms and Virulence

Background: Staphylococcus aureus is a prominent pathogen responsible for human pyogenic and nosocomial infections. Although numerous studies on S. aureus L-forms and virulence are available in the literatures, there are still various impediments in the research methods employed. Objectives: This study aimed to perform fluorescence reporter in studying S. aureus L-form and its virulence, and wild strain virulence. Methods: Newman-pCM29 strain which can express green fluorescent protein (GFP) was constructed and used to detect S. aureus L-form formation and virulence in vitro and in vivo. Results: "Fried egg" like L-form colonies of GFP reporter S. aureus and the dense core of the colonies embedded into soft agar can be observed obviously. GFP reporter can contribute to preparing L-form suspension for injection and track the protoplasts and reverted cells in lesions of mice. GFP reporter, also, can help to detect S. aureus wild strain distribution and inflammation scope in lesions, and the fluorescence intensity can be used as an effective surrogate to represent the bacterial quantity in lesions. Fluorescence can improve to distinguish the colonies of varying sizes derived from the injected bacteria or from contaminants. Conclusions: Fluorescence reporter in S. aureus is a powerful tool which can provide new insight into S. aureus L-form formation in vitro and its fate in vivo, and wild strain virulence in vivo in a non-traditional manner.