Rapid Antimicrobial Susceptibility Test of Helicobacter pylori to Metronidazole via Single‐Cell Raman Spectrometry

Background Metronidazole is a first‐line antibiotic to treat Helicobacter pylori infections. However, the Clinical Laboratory Standards Institute guidelines recommend against using antimicrobial susceptibility test (AST) to test metronidazole resistance, due to the unreliable predictive power which can result in treatment failure. Objectives The aim of this study was to establish an 8‐h, metabolic‐phenotype based AST for H . pylori metronidazole susceptibility using D 2 O‐probed Raman microspectroscopy. Methods Minimal inhibitory concentration (MIC) measured by conventional AST (E‐test) were compared with expedited MIC via metabolic activity (eMIC‐MA) for 10 H . pylori isolates. Raman barcodes of cellular‐response to stress (RBCS) incorporating protein and carbohydrate Raman bands, were utilized to identify a biomarker to distinguish metronidazole susceptibility. Results Specifically, eMIC‐MA produces metronidazole susceptibility results showing 100% agreement with E‐test, and determines the bactericidal dosage for both high‐ and low‐level resistant H . pylori strains. In addition, RBCS not just reliably distinguish between metronidazole‐susceptible and ‐resistant strains, but reveal their distinct mechanisms in bacterial responses to metronidazole. Conclusion The speed, accuracy, low cost, and rich information content that reveals the mode‐of‐action of drugs suggest the method's value in guiding metronidazole prescriptions for H . pylori eradication and in rapid screening based on drug‐resistance mechanism.