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In Neisseria gonorrhoeae, all penicillinase-specifying plasmids isolated so far share homology with each other and carry a 60% deleted sequence of TnA. Plasmid pHD131, an element isolated from Haemophilus ducreyi and carrying an intact copy of the ampicillin resistance transposable element, was introduced from Escherichia coli into N. gonorrhoeae by both transformation and conjugative mobilization. Plasmids were recovered with no detectable deletion. After their transfer back into E. coli, transposition assays onto phage-lambda DNA demonstrated that the TnA elements were still functional. Plasmid pHD131 could be stably maintained in N. gonorrhoeae with or without the presence of penicillin. These results support the hypothesis that the absence in N. gonorrhoeae of plasmids carrying entire and functional TnA transposons cannot be ascribed to incompatibility between the genetic element and the host, but rather to a barrier to introduction of foreign DNA into gonococcus.

Norfloxacin, an analogue of nalidixic acid, is a novel antibacterial compound active against both gram-negative and gram-positive pathogens. 142 Neisseria gonorrhoeae isolates proved to be remarkably sensitive to it; the MIC50 and MIC90 values for norfloxacin were 0.03 microgram/ml and 0.06 microgram/ml, respectively, for the strains resistant to the penicillins; for the strains susceptible to the penicillins, the same value of 0.03 microgram/ml was found both for the MIC50 and MIC90. 100% of the strains were inhibited by 0.125 microgram/ml of the drug: this concentration is far below the serum levels (1.5 micrograms/ml) achievable following normal dosage. Clinical trials should be performed to establish whether the activity in vivo corresponds to that found in vitro.

The plasmid pUB307, a derivative of RP1, is a conjugative, broad-host-range plasmid. We have shown that this element mobilizes gonococcal resistance plasmids from Escherichia coli to Neisseria gonorrhoeae, thus providing evidence that extrachromosomal elements can efficiently enter gonococci by conjugation. Furthermore, pUB307 can also be used as a helper element to mobilize the cloning vector pLES2 into N. gonorrhoeae. This finding significantly increases the usefulness of pLES2 as a shuttle vector between E. coli and gonococcus.

Of 1031 consecutive isolates of Neisseria gonorrhoeae examined before 31 July 1982, 30 strains showed beta-lactamase activity. All the penicillinase producing N gonorrhoeae (PPNG) strains were imported, 23 of them from South East Asia. One PPNG strain was identified as coming from Antigua and one from Chile, the first PPNG strains to be reported from these two countries. In 28 strains, the minimum inhibitory concentration (MIC) of penicillin was greater than or equal to 4.0 mg/l, and 15 strains were insensitive to tetracycline (MIC greater than or equal to 2.0 mg/l). Four strains were less sensitive to spectinomycin (MIC = 30 mg/l), while the remaining 26 were highly sensitive to this antibiotic. The African plasmid was found in only one strain (that originating from Antigua), and all other PPNG strains contained the Asian plasmid. Twenty PPNG strains contained the resistance plasmid together with the transfer plasmid. Auxotype determination showed that 18 PPNG strains were prototrophic whereas 11 were proline requiring.

In a study to determine the epidemiological situation of N. gonorrhoeae (NG) in Switzerland, 149 strains isolated from different regions over the period September 1981 to February 1982 were analyzed for sensitivity to various antibiotics (minimum inhibitory concentration [MIC] for penicillin G, ampicillin, cefuroxime, tetracycline, thiamphenicol, and spectinomycin) and for their auxotype. From the results obtained it can be concluded that (1) the PPNG (penicillinase producing NG) strains are not a problem at present in Switzerland; (2) 15% of the non-penicillinase producing NG strains are "less sensitive" to penicillin G (MIC equal to or greater than 0.5 micrograms/ml); (3) sensitivity level of the NG strains to the various antibiotics assayed and the auxotypes do not show any significant peculiarity when compared to the data reported in other countries; (4) penicillin G should still be used as the first choice antibiotic at present in Switzerland, with spectinomycin, thiamphenicol and cefuroxime as second choice antibiotics; (5) when compared according to the geographical origin of their isolation, the NG strains show specific peculiarities, a fact which could lead to an antibiotic therapy policy more suited to specific regions.

In three beta-lactamase-producing strains of Neisseria gonorrhoeae, ampicillin resistance is due to the presence of a 7.4-kilobase plasmid. Heteroduplex analysis has shown that the R plasmid contains a 1.6-kilobase segment homologous to the right part (the region coding for the beta-lactamase) of the Tn3-like transposon Tn2301 the 1.6-kilobase DNA segment is not transposable, but it can give rise to a functional transposon, when linked to the left part of TN2301. This provides strong evidence that the R plasmids of N. gonorrhoeae are deletion derivatives of a plasmid that contained an entire TN3-like transposon.