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Volume 31, Number 10—October 2025

Research Letter

Neonatal Gonococcal Conjunctivitis Caused by Fluoroquinolone-Resistant Neisseria gonorrhoeae

Hiroto Mizushima, Miwa Komori, Carolina Andrea Yoshida, and Isao MiyairiComments to Author 
Author affiliation: Hamamatsu University School of Medicine, Shizuoka, Japan

Main Article

Table

MICs of antimicrobial drugs for Neisseria gonorrhoeae isolate B196-JP22 from a case of neonatal gonococcal conjunctivitis caused by fluoroquinolone-resistant N. gonorrhoeae, Japan

Antimicrobial drug MIC, mg/L Interpretation* Antimicrobial resistance genes (mutation details)
Penicillin G
1
Reduced susceptibility
mtrR (mtrR_A39T),† mtrR (mtrR_promoter_a-57del),‡ ponA (ponA_L421P),† penA gene§
Piperacillin/tazobactam
<0.01
Susceptible

Ceftriaxone
0.05
Susceptible

Meropenem
0.01
Susceptible

Levofloxacin
12
Resistant
gyrA (gyrA_S91F/D95N),† parC (parC_S87I)†
Azithromycin 0.75 Elevated MIC¶ mtrA, macA, macB, farA#

*Antimicrobial MIC tested by using Etest (bioMérieux, https://www.biomerieux.com). Interpretation according to Clinical and Laboratory Standards Institute (CLSI) standards (4). CLSI cutoff for susceptible is MIC <0.06 μg/mL, for intermediate is MIC 0.12–1 μg/mL, for resistant is MIC >2 μg/mL. A MIC of 1 was described as reduced susceptibility. †Missense mutation. ‡Promoter deletion. §The penA gene that encodes the PBP2 shared 99.77% identity with the penA encoded by the World Health Organization Alfa strain. However, it could not be classified by using the NG-STAR platform (https://ngstar.canada.ca) because of 2 gaps in the sequence, and the closest NG STAR type was the nonmosaic allele 18.001. ¶MIC 0.75 μg/mL was within susceptible range, although elevated compared with local reference strains. CLSI MIC cutoff for N. gonorrhoeae azithromycin susceptibility is MIC <1 μg/mL. However, CLSI has set a susceptible only interpretive breakpoint at this value, with the recommendation that this applies when azithromycin (1 g single dose) is used in combination with another antimicrobial, such as ceftriaxone. #Efflux pumps encoded in this strain include mtrA, macA, macB, and farA.

Main Article

Page created: September 08, 2025
Page updated: September 25, 2025
Page reviewed: September 25, 2025
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