Codon 91 Gyrase A Testing Is Necessary and Sufficient to Predict Ciprofloxacin Susceptibility in Neisseria gonorrhoeae

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Abstract
To the Editor—We read with great interest the article by Grad et al [ 1]. We agree with their conclusion that gyrase A (gyrA) genotype testing of Neisseria gonorrhoeae is a valuable means of resistance testing; however, we believe that gyrA testing, specifically of codon 91, is both necessary and sufficient for predicting susceptibility to ciprofloxacin. There have been 11 studies (N=4777 specimens) comparing real-time polymerase chain reaction (RT-PCR) genotype results with conventional antimicrobial susceptibility testing methods, all of which have demonstrated high sensitivity and specificity (93.8%–100% and 93.2%–100%, respectively). Positive and negative predictive values were similarly impressive (94.4%–100% and 87.5%–100%, respectively). Furthermore, 4 studies found that mutation at codon 91 of the gyrA gene as determined by RT-PCR was 100% specific for N. gonorrhoeae compared with other Neisseria species [ 2–5].
Funding Information
  • National Institutes of Health (R21AI117256, R21AI109005)

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