Recombinant Bacteriophage Cell-Binding Domain Proteins for Broad-Spectrum Recognition of Methicillin-Resistant...

Methicillin-resistant Staphylococcus aureus (MRSA) has been well-recognized as one of the most common multiresistant bacteria threatening human health. Broad-spectrum recognition of multiple MRSA strains can meet the urgent demands for efficient diagnosis and subsequent decision of relevant treatment of MRSA-induced infections. Here, recombinant cell-binding domain (CBD) and green fluorescent protein-fused CBD of MRSA bacteriophage were expressed in soluble form. Distinct from the strain-specific MRSA bacteriophage, both recombinant CBD proteins displayed broad-spectrum recognition capability toward all five staphylococcal cassette chromosome mec types of MRSA. Furthermore, they did not display any lytic activity toward the host bacteria, which facilitated the capture of whole MRSA cells with ideal flexibility for downstream manipulation and tracing. For demonstration of their application potential, a flow cytometry method employing the recombinant CBD proteins as the recognition agents was established to detect MRSA within a dynamic range of 1.5 × 10² to 1.5 × 10⁶ cfu mL^-1. The method can exclude potential interference from methicillin-sensitive Staphylococcus aureus strains and other bacterial species. The recombinant CBD proteins were also successfully employed in antibiotic susceptibility testing of MRSA with a microplate-based method. The obtained results were consistent with those by the standard broth microdilution method. The satisfying results demonstrated their great application potential in clinical diagnosis and treatment of MRSA-induced infections.