Antimicrobial Susceptibility Testing of Neisseria gonorrhoeae using a Phenotypic-Molecular Assay and Lyophilized Antimicrobials

Abstract Gonorrhea is an urgent global public health threat as Neisseria gonorrhoeae (Ng) has progressively developed resistance to all antibiotics commonly used for treatment. Surveillance of antimicrobial susceptibility trends is critical to monitor the emergence and spread of antimicrobial resistance. The gold standard methods for antimicrobial susceptibility testing (AST) of Ng are laborious and time-consuming. We evaluated a phenotypic molecular approach, involving a short cultivation step and quantitative PCR, with lyophilized antimicrobials to characterize antimicrobial susceptibility in Ng. There was excellent concordance between AST performed with liquid and lyophilized ciprofloxacin, penicillin, and tetracycline using the pheno-molecular assay, following a four-hour incubation step. The categorical agreement between the pheno-molecular assay and the gold standard AST results was 92.4% for characterization of antimicrobial susceptibility. Essential agreement between the two methods was 91.9%. Characterization of ceftriaxone susceptibility in Ng using the pheno-molecular assay required a six-hour incubation step.