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M C Roberts

Publications and source records attributed to M C Roberts.

254 records · Page 15Linked to original sources
PubMedDate not supplied

Transfer frequency of various 25.2 Mdal tetracycline resistance plasmids in Neisseria gonorrhoeae.

We examined ten Neisseria gonorrhoeae strains, all of which carried the tetracycline resistant 25.2 Mdal plasmid, for their ability to act as donors in conjugation. All strains transferred the 25.2 Mdal plasmid and tetracycline resistance to the recipient N. gonorrhoeae strain F62 at a frequency that ranged from 10(-2) to 10(-7) per recipient. The four strains carrying the beta-lactamase plasmid and the 25.2 Mdal plasmid transferred the beta-lactamase plasmid at a frequency of 10(-6) to 10(-8) per recipient. The results indicate that most of the N. gonorrhoeae strains carrying the 25.2 Mdal plasmid can act as donors of this plasmid and can also mobilize the transfer of the 3.2 Mdal plasmid and the 4.4 Mdal plasmid to recipient strains.

Conjugation, Genetic↗
PubMedDate not supplied

Acquisition of beta-lactamase and TetM-containing conjugative plasmids by phenotypically different strains of Neisseria gonorrhoeae.

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 greater than or equal to 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.

Conjugation, Genetic↗