Acquisition of β-lactamase and TetM-containing Conjugative Plasmids by Phenotypically Different Strains of Neisseria gonorrhoeae

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Abstract
.beta.-lactamase plasmids confer high-level penicillin resistance on strains of Neisseria gonorrhoeae and may be mobilized between strains by conjugative plasmids. The authors examined 32 isolates belonging to 23 auxotype/serovar (A/S) classes to determine the frequency with which they acquired the 4.4-, 3.2-, and 3.05-megadalton (Mdal) .beta.-lactamase plasmids, respectively. The 3.05-Mdal .beta.-lactamase plasmid was not acquired by any isolate. Each of 22 isolates possessing only the 2.6-Mdal plasmid or both the 2.6- and 24.5-Mdal plasmids acquired the 4.4- and 3.2-Mdal plasmids at similar frequencies, and 12 (55%) acquired the 4.4- or 3.2-Mdal plasmids at a frequency of .gtoreq. 10-3 per input recipient; all transconjugants acquired the 24.5-Mdal conjugative plasmid. Among ten isolates that lacked the 2.6-Mdal plasmid (plasmidless), seven isolates that included five PAU/IB-2, -16 isolates acquired neither the 4.4- nor 3.2-Mdal plasmid; three non-Pau isolates acquired both the 4.4- and 3.2-Mdal plasmids (10-2-10-5 per input recipient). All plasmidless isolates acquired the 25.2-Mdal TetM containing plasmid with frequencies ranging from 10-1 to 10-8 per input recipient. These data suggest that gonococcal strains possessing the 2.6-Mdal plasmid readily acquire the 4.4- and 3.2-Mdal .beta.-lactamase plasmids in vitro, whereas acquisition of these plasmids by strains lacking the 2.6-Mdal plasmid is strain dependent.