video: A new diagnostic for antibiotic susceptibility testing uses single-molecule DNA counting to determine if urine samples contain resistant bacteria. Here, the antibiotic-treated sample ('treated,' left) shows fewer DNA molecules compared with the same sample without antibiotic ('control,' right), indicating the pathogen is susceptible to the antibiotic. view more
Credit: Ismagilov Lab/Caltech. Chips provided by SlipChip Corp
Scientists have pioneered a method to detect antibiotic susceptibility for urinary tract infections in less than 30 minutes - potentially enabling patients to be diagnosed and prescribed effective treatments during a single clinical visit. Urinary tract infections account for almost 8 million primary care visits every year (and almost always require antibiotics), yet the emergence of bacterial resistance remains a growing threat to global health, rendering many antibiotics ineffective. Seeking a faster method to evaluate the response of a bacteria to antibiotics, Nathan Schoepp et al. used a highly sensitive single-molecule DNA amplification and quantification technique called dLAMP to directly count bacterial genomes in urine samples (as opposed to isolating and culturing the microbes for testing over several days). To perform the assay, urine samples were diluted and incubated for 15 minutes before dLAMP analysis to calculate ratios of bacterial DNA concentrations between untreated (without antibiotics) and treated (with antibiotics) samples. Ratios below preset thresholds indicated sensitivity to the antibiotics, because treatment reduced bacterial abundance. While other DNA quantification approaches can take hours, Schoepp and colleagues optimized the dLAMP protocol to provide more precise measurements within 6.7 minutes - allowing the entire procedure to be performed in less than half an hour. The researchers validated their platform with 51 clinical samples that had been confirmed as containing bacteria that were either susceptible or resistant to one of two commonly used antibiotics (ciprofloxacin or nitrofurantoin). According to the authors, with further development for additional pathogens, antibiotics, and sample types, the new test could help clinicians make rapid decisions to better manage infectious diseases.
###
Journal
Science Translational Medicine