A novel method for rapid detection of lactic acid bacteria resistance based on flow cytometry

Due to the misuse of antibiotics, bacterial resistance has become an increasingly serious issue. The greatest drawback of the traditional method for detecting the resistance of lactic acid bacteria (LAB) is that it is time consuming, usually taking 48 h. Here, we would like to apply fluorescent dyes combined with flow cytometry to develop a rapid assay, then we labeled five strains of Bifidobacterium pseudocatenulatum , one strain of Lactobacillus plantarum , and 12 strains of Lactobacillus helveticus with a fluorescent probe and measured the average fluorescence intensity following treatment with 12 different antibiotics (ampicillin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, kanamycin, neomycin, rifampicin, streptomycin, tetracycline, and vancomycin) at different concentrations by flow cytometry. The optimal experimental conditions are also discussed. The minimum inhibitory concentrations (MICs) of six test strains were determined by the broth microdilution (BMD) method and flow cytometry-based drug sensitivity testing (FCST). Under the effects of 12 different antibiotics, the MICs of the two methods were positively correlated ( P < 0.001), with correlation coefficients ranging from R 2 = 0.92 to 0.99, indicating a good linear correlation. The method was further applied to the detection of drug resistance in LAB, and the consistency between the MICs measured by FCST and the BMD method was 95.14%. FCST can rapidly and accurately determine the MICs of antibiotics for LAB, greatly reducing the time required, compared to traditional methods of detecting drug resistance. This method will be useful for rapid detection of microbial drug resistance, providing support for research on the resistance of LAB, and will also facilitate rapid detection of the MICs of drugs for these bacteria. • Establishing a novel method for detecting the minimum inhibitory concentration of lactic acid bacteria through fluorescent labeling and flow cytometry. • Enables hour-scale MIC detection for lactic acid bacteria (LAB), reducing analysis time by >80% vs. traditional 48-h methods. • The flow cytometry-based drug sensitivity test provides support for the study of lactic acid bacteria resistance and has important application value for the rapid monitoring of microbial resistance in the food industry.