Deletion of the meningococcal fetA gene used for antigen sequence typing of invasive and commensal isolates from Germany: frequencies and mechanisms

Antigen sequence typing (ST) of FetA is part of the molecular typing scheme of Neisseria meningitidis. Among invasive meningococcal isolates from 2,201 patients in Germany, we identified 11 strains lacking the fetA gene because of deletions mediated by repeat arrays flanking the gene, i.e., Correia elements, repeat sequence 13 (RS13), and duplicated RS3. Geographic mapping and multilocus ST of invasive isolates revealed that fetA deletion was a sporadic event without genetic fixation. Among 821 carrier strains, 12 strains lacked fetA, suggesting that fetA is maintained during asymptomatic carriage. Interestingly, most of these isolates belonged to the multilocus ST-35 clonal complex (cc). ST-35 cc strains and the recently published ST-192 strains from Burkina Faso may benefit from loss of fetA, but their infrequent occurrence among invasive isolates currently does not affect fetA antigen ST.