Emergence of ciprofloxacin-resistant B from asymptomatic carriers during an outbreak in Peru, 2017.

Asymptomatic carriers are a likely source of transmission of to close contacts who are placed at a higher risk for invasive meningococcal disease (IMD). Although ciprofloxacin-resistance is rare, there have been an increase in the reports of resistant isolates mainly in patients diagnosed with IMD, and little is known about the ciprofloxacin-resistance in the carrier populations. We performed a pharyngeal carriage study during a 2017 military setting outbreak in Peru, caused by a ciprofloxacin-resistant B. The isolates analysed came from two hospitalized cases and six asymptomatic carriers. Whole-genome sequence-based analysis was performed and showed that strains carrying the ThrIle mutation, in the gene encoding for subunit A of DNA gyrase (A), were responsible for the fluoroquinolone resistance (MICs ≥0.256 µg ml) and were closely related to highly virulent strains from France, Norway and the UK. Phylogenetic analysis of the A gene revealed that likely these Peruvian isolates acquired resistance through horizontal gene transfer from . Our study provides evidence for the emergence and propagation of ciprofloxacin-resistant B from asymptomatic carriers, and recommends the introduction of serogroup B vaccines for high-risk populations.