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Although antimicrobial resistance has been uncommon among Neisseria meningitidis isolates, novel strains resistant to ciprofloxacin and penicillin have recently been identified (NEJM JW Infect Dis Sep 2020 and MMWR Recomm Rep 2020 Jun 19). In N. meningitidis, penicillin resistance is associated with the β-lactamase gene blaROB-1 whereas ciprofloxacin resistance is associated with a mutation at amino acid 91 (T91) in the quinolone resistance–determining region of the DNA gyrase gene, gyrA. To characterize the evolution of such resistance, CDC researchers identified N. meningitidis isolates from 2097 cases of invasive meningococcal disease (IMD) in the U.S. between January 2011 and February 2020.
Whole-genome analysis identified 45 isolates with penicillin and/or ciprofloxacin resistance. Eleven were dually resistant, having both the blaROB-1 gene and the gyrA T91 mutation. Phenotypic testing confirmed that these 11 isolates were resistant to penicillin and ampicillin as well as ciprofloxacin. All 11 dually resistant isolates were part of a single clone (CC23) and belonged to serogroup Y, although they were identified in multiple states without apparent epidemiologic linkage. Strains with dual resistance arose beginning in 2019, originating from a β-lactamase positive clade that acquired ciprofloxacin resistance from another Neisseria species.
Potts CC et al. Acquisition of ciprofloxacin resistance among an expanding clade of β-lactamase positive, serogroup Y Neisseria meningitidis in the United States. Clin Infect Dis 2021 Apr 26; [e-pub]. (https://doi.org/10.1093/cid/ciab358)
Comment
This study highlights the importance of genomic surveillance to detect trends in antibiotic resistance. While the incidence of these dually resistant strains is currently infrequent, the results point to a recent emergence that could escalate, thereby possibly precluding the use of penicillin for treatment of (and ciprofloxacin for prophylaxis of) meningococcal disease in the future.