Violacein quantification using a smartphone coupled to an endoscopic camera: Quorum sensing inhibition in Chromobacterium violaceum

Quorum sensing (QS) strongly regulates the biofilm formation mechanism in several microorganisms. The blockade of violacein production in Chromobacterium violaceum has been employed to indicate QS inhibition. Nevertheless, quantifying violacein is challenging due to the reliance on high-cost equipment and supplies. Consequently, this study compared the production and inhibition of violacein using a traditional spectrophotometric method and an alternative approach utilizing a Photometrix UVC Android application integrated with a USB endoscopic camera. The study standardized the growth of C. violaceum in several culture media and incubation times, then evaluated the pigment inhibition against salicylic acid. Results indicated that C. violaceum produced more violacein when cultivated in BHI broth for 24 h. Salicylic acid inhibited violacein production, even at sub-inhibitory concentrations, with a minimum inhibitory pigment concentration (125 µg/mL) and a minimum bactericidal concentration (2000 µg/mL). A comparison between application-based readings and the traditional method showed no significant differences, highlighting the potential of this technology as an essential tool in for QS inhibition and biofilm research. • C. violaceum has a better production of violacein when cultivated in BHI broth for 24 h. • Salicylic acid was able to inhibit violacein production, even when tested at sub-inhibitory concentrations. • Photometrix can be a great ally in research involving QS inhibition and biofilms.