Characterization of a novel β-lactamase-producing plasmid in Neisseria gonorrhoeae: sequence analysis and molecular typing of host gonococci.

OBJECTIVES

To determine the complete nucleotide sequence of the novel Johannesburg β-lactamase-encoding gonococcal plasmid (pEM1) and to determine the strain relatedness of Johannesburg plasmid-containing penicillinase-producing Neisseria gonorrhoeae (PPNG) by molecular typing.

METHODS

Eleven PPNG isolates containing the Johannesburg β-lactamase-encoding plasmid were previously identified among gonococci isolated from men with urethral discharge attending a clinic in Alexandra (Johannesburg) using a PCR assay. DNA sequence-based characterization of one such plasmid was performed to determine its relatedness to the prototype Asia plasmid. The 11 PPNG isolates containing the Johannesburg plasmid and 105 other clinical gonococci isolates were typed using N. gonorrhoeae multi-antigen sequence typing (NG-MAST).

RESULTS

Plasmid pEM1 was determined to comprise 4865 bp and to be a deletion derivative of the prototype Asia plasmid with a unique 2560 bp deletion in the non-TnA region. NG-MAST genotyping demonstrated a significant association between sequence type (ST) 502, or other closely related STs, and the Johannesburg plasmid-containing PPNG (P < 0.0001).

CONCLUSIONS

Sequencing of a novel β-lactamase-encoding plasmid (pEM1) found in PPNG isolates in Johannesburg shows it to be a deletion derivative of the prototype Asia plasmid, the deletion most likely arising as a result of DNA rearrangements. The majority of Johannesburg plasmid-containing PPNG isolates were, or were very closely related to, ST502.