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J Antimicrob Chemother. 2016 Apr;71(4):897-902. doi: 10.1093/jac/dkv432. Epub 2016 Jan 26.

Accurate detection of Neisseria gonorrhoeae ciprofloxacin susceptibility directly from genital and extragenital clinical samples: towards genotype-guided antimicrobial therapy.

Author information

1
Institute for Infection and Immunity, St George's, University of London, London, UK.
2
Sexually Transmitted Bacteria Reference Unit, Public Health England, Colindale, London, UK.
3
Institute for Infection and Immunity, St George's, University of London, London, UK Department of STI/HIV, Public Health England, Colindale, London, UK.
4
Institute for Infection and Immunity, St George's, University of London, London, UK Medical Microbiology, South West London Pathology, St George's University Hospitals NHS Foundation Trust, London, UK.
5
Institute for Infection and Immunity, St George's, University of London, London, UK Department of Genitourinary & HIV Medicine, St George's University Hospitals NHS Foundation Trust, London, UK Department of STI/HIV, Public Health England, Colindale, London, UK ssadiq@sgul.ac.uk.

Abstract

INTRODUCTION:

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. 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.

METHODS:

NGSNP, 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.

RESULTS:

NGSNP 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.

CONCLUSIONS:

Genotypic 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.

PMID:
26817487
PMCID:
PMC4790619
DOI:
10.1093/jac/dkv432
[Indexed for MEDLINE]
Free PMC Article

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