Rapid detection of antibiotic sensitivity of Staphylococcus aureus by Raman tweezers

Methicillin-resistant Staphylococcus aureus is a bacterium pathogenic to humans and a leading cause of the hospital-acquired infections, causing significant increase in morbidity and mortality. Conventional antibiotic sensitivity testing requires culturing of the isolated pathogen in the presence of antibiotics, and it takes at least 48 hours. Comparatively faster determination of bacterial sensitivity to antibiotics can be achieved with Raman tweezers—an analytical method based on Raman spectroscopy and optical trapping. This article demonstrates the effectiveness of this approach for the discrimination between a methicillin-resistant and a methicillin-sensitive strain of Staphylococcus aureus in about 4 hours from a microliter volume of the bacterial sample. We found that the antibiotic-induced changes in the bacterial cells influenced the ratio of the Raman signals of nucleic acids to phenylalanine. This points to the antibiotic causing cell lysis and the associated loss of nucleic acids from the cytoplasm.