WGS analysis of a penicillin-resistant Neisseria meningitidis strain containing a chromosomal ROB-1 β-lactamase gene

OBJECTIVES: Neisseria meningitidis is rarely penicillin resistant. We describe WGS analysis of a penicillin-resistant N. meningitidis collected from a case of invasive meningococcal disease. METHODS: Serogrouping, serotyping and serosubtyping were performed with specific antibodies. β-Lactamase was detected by nitrocefin. MICs were determined by Etest and agar dilution. Sequencing of N. meningitidis genomes was done on the Illumina MiSeq platform and genome data were analysed using the Bacterial Isolate Genome Sequence Database (BIGSdb) on the PubMLST Neisseria website (https://pubmlst.org/neisseria/). Transformation was used to confirm the genetic basis of the penicillin resistance. RESULTS: An N. meningitidis blood isolate from a female patient in her mid-50s with a painful and septic left shoulder was found to have penicillin MIC values of 3–12 mg/L. The isolate was typed as Y: 14, 19: P1.– and ST3587, and was weakly β-lactamase positive. WGS analysis identified a full-length copy of the β-lactamase gene bla(ROB-1), which was contained on a 1719 bp insert with a G + C content of 41.7% (versus a G + C content of N. meningitidis of 51.7%), suggesting that the bla(ROB-1) gene came from a different bacterial species. A GenBank analysis of the bla(ROB-1) gene insert found 99.77% identity with a DNA segment found in plasmid pB1000′ from Haemophilus influenzae. Transformation of a penicillin-susceptible strain with the bla(ROB-1) gene conferred β-lactamase activity and penicillin resistance. CONCLUSIONS: N. meningitidis serogroup Y, ST3587 can carry and express the bla(ROB-1) gene, leading to penicillin resistance. It is highly likely that the N. meningitidis isolate acquired the bla(ROB-1) gene from H. influenzae.