Molecular recognition strategy for detection and antimicrobial susceptibility testing of Staphylococcus aureus by utilizing teicoplanin and porcine IgG as indicator molecules

Abstract

Timely and accurate anti-infective therapy significantly benefits treatment of various life-threatening bacterial infectious diseases. Unfortunately, owing to the lack of selectivity for recognizing bacterial species, most of the reported phenotypic antimicrobial susceptibility testing protocols suffer from time-consuming bacterial isolation and identification. In this work, a highly-selective molecular recognition-based sandwich fluorimetric assay was developed to rapidly detect Staphylococcus aureus (S. aureus), and furtherly to assess its susceptibility to antibiotics. Immobilized porcine IgG was utilized to capture S. aureus through the selective interaction between Fc fragment of porcine IgG and protein A in the cell wall of S. aureus. Fluorescein isothiocyanate-labeled teicoplanin was adopted as the signal tracer utilizing the binding behavior between teicoplanin and d-Ala-d-Ala moieties in the peptidoglycans of Gram-positive bacterial cell wall. S. aureus could be detected within a wide linear rang of 1.0 × 103 to 1.0 × 107 CFU mL−1. Subsequently, this protocol utilizing porcine IgG and teicoplanin as the indicator molecules was utilized to assess the antimicrobial susceptibility of S. aureus after the bacteria were treated with antibiotics. The minimum inhibitory concentrations of penicillin, cefoxitin, clindamycin, trimethoprim/sulfamethoxazole and erythromycin were estimated to be >0.25,<4, <0.25, <2/38 and <0.5 μg mL−1, respectively. The whole process for antimicrobial susceptibility testing can be completed within 4 h since it avoided extra time-consuming isolation and identification of bacterial species.