Abstract
IntroductionIncreasing use of nucleic acid amplification tests (NAATs) as the primary means of diagnosing gonococcal infection has resulted in diminished availability of Neisseria gonorrhoeae antimicrobial susceptibility data. We conducted a prospective diagnostic assessment of a real-time PCR assay (NGSNP) enabling direct detection of gonococcal ciprofloxacin susceptibility from a range of clinical sample types.MethodsNGSNP, designed to discriminate an SNP associated with ciprofloxacin resistance within the N. gonorrhoeae genome, was validated using a characterized panel of geographically diverse isolates (n = 90) and evaluated to predict ciprofloxacin susceptibility directly on N. gonorrhoeae-positive NAAT lysates derived from genital (n = 174) and non-genital (n = 116) samples (n = 290), from 222 culture-confirmed clinical episodes of gonococcal infection.ResultsNGSNP correctly genotyped all phenotypically susceptible (n = 49) and resistant (n = 41) panel isolates. Ciprofloxacin-resistant N. gonorrhoeae was responsible for infection in 29.7% (n = 66) of clinical episodes evaluated. Compared with phenotypic susceptibility testing, NGSNP demonstrated sensitivity and specificity of 95.8% (95% CI 91.5%–98.3%) and 100% (95% CI 94.7%–100%), respectively, for detecting ciprofloxacin-susceptible N. gonorrhoeae, with a positive predictive value of 100% (95% CI 97.7%–100%). Applied to urogenital (n = 164), rectal (n = 40) and pharyngeal samples alone (n = 30), positive predictive values were 100% (95% CI 96.8%–100%), 100% (95% CI 87.2%–100%) and 100% (95% CI 82.4%–100%), respectively.ConclusionsGenotypic prediction of N. gonorrhoeae ciprofloxacin susceptibility directly from clinical samples was highly accurate and, in the absence of culture, will facilitate use of tailored therapy for gonococcal infection, sparing use of current empirical treatment regimens and enhancing acquisition of susceptibility data for surveillance.
Highlights
Increasing use of nucleic acid amplification tests (NAATs) as the primary means of diagnosing gonococcal infection has resulted in diminished availability of Neisseria gonorrhoeae antimicrobial susceptibility data
The aim of this study was to ascertain the diagnostic performance of a real-time PCR assay (NGSNP), enabling genotypic prediction of ciprofloxacin-susceptible or -resistant N. gonorrhoeae directly on clinical samples taken from diverse sites
Results of NGSNP testing directly on residual N. gonorrhoeae-positive NAAT lysates was compared with findings of routine culture-based antimicrobial susceptibility testing (AST)
Summary
Increasing use of nucleic acid amplification tests (NAATs) as the primary means of diagnosing gonococcal infection has resulted in diminished availability of Neisseria gonorrhoeae antimicrobial susceptibility data. Neisseria gonorrhoeae infection is frequently treated empirically at the point of care (PoC), based on clinical presentation alongside findings from microscopy of Gram-stained genital swabs.[1] Efficacy of antimicrobial therapy is threatened by the development of successive antimicrobial resistance (AMR) in response to antibiotic classes used over time,[2] resulting in potentially empirically untreatable gonorrhoea.[3] In addition, nucleic acid amplification tests (NAATs) have largely replaced culture as the primary laboratory method of gonorrhoea diagnosis,[4,5] resulting in a decline in availability of antibiotic susceptibility data to guide prescribing.[6] These challenges have instigated the development of the WHO Global action plan to control the spread and impact of AMR in N. gonorrhoeae,[7] recognizing the need for molecular methods for monitoring and detecting AMR. Fluoroquinolones may represent a favourable group of antimicrobials to which molecular AMR detection may be applied due to the relative genetic simplicity of resistance, mediated predominantly through SNPs within genes coding for the GyrA subunit of DNA gyrase and ParC subunit of topoisomerase IV.[8]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
