The incidence of penicillinase-producing Neisseria gonorrhoeae (PPNG) infections has increased in Canada during the past 2 years. Most of these cases were imported from abroad. The PPNG strains from these cases were characterized with respect to susceptibility to 11 antibiotics, auxotype, and plasmid content. Rosaramicin and cefuroximne proved to be the most potent of the antibiotics tested. The molecular characterization of the isolates indicated that all carried a 2.6-megadalton cryptic plasmid. Most of the PPNG isolates (87%) harbored a 4.5-megadalton penicillinase-producing plasmid, whereas only 13% harbored the 3.2-megadalton penicillinase-producing plasmid. In those cases where contact tracing was possible, the correlation linking strains of Far Eastern etiology with carriage of the 4.5-megadalton plasmid was upheld. The penicillinase-producing strains were typed auxanographically in either the proline-requiring (57%) or prototrophic groups (42%). Substrate hydrolysis profiles and analytical isoelectric focusing of crude ,B-lactamase extracts of several isolates has reconfirmed that these strains elaborate a type TEM-1 enzyme. Several of the penicillinase-producing plasmids were also examined for plasmid stability.

The antibiotic susceptibility of 2609 Salmonella isolates, collected during the period 1975-1976, was tested and the relationships between antibiotic-resistance pattern, source of isolation, and serovar and phagovar were determined. Of 95 serovars examined, 40 were sensitive to all of the antibiotics tested. Salmonella typhimurium was the major contributor to multiple resistance from both human and non-human sources. Multiply resistant strains were not found from animal feed sources and, in addition, S. typhimurium, one of the most predominant serovars, was found in every source but animal feeds. 90% of phagovar 10 was sensitive to all antibiotics tested whereas over 80% of phagovars 3-aerogenic, 92, and 123 were multiply resistant.

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Thiamphenicol was compared with penicillin, tetracycline, and chloramphenicol for its ability to inhibit 530 isolates of Neisseria gonorrhoeae, including 13 penicillinase-producing isolates. Thiamphenicol proved to be as active as chloramphenicol in inhibiting all of the isolates.Thiamphenicol, a chloramphenicol analog in which the nitro group has been substituted with a methylsulfonyl group (2), has been suggested as a viable alternate therapy regimen to penicillin in the treatment of infections with Neisseria gonorrhoeae (2). This antibiotic has been successfully used in treatment of uncomplicated gonococcal infections in both men and women (4, 15), with failure rates as low as 2 to 3%.Because penicillin and tetracycline treatment failures have been correlated with increased resistance to those antibiotics (5, 6), the use of thiamphenicol as an alternate therapy regimen in the treatment of N. gonorrhoeae should be seriously evaluated. In the present study, we have examined the minimal inhibitory concentrations (MICs) of 530 isolates of N. gonorrhoeae, including 13 f)-lactamase-producing isolates, to penicillin, tetracycline, chloramphenicol, and thiamphenicol.The fi-lactamase-producing isolates were obtained from Canadian, Asian, American, and African sources during the period 1976 to 1978. The other 517 nonpenicillinase-producing isolates were collected during a previous study (la) in 1973 to 1974. All strains were maintained at -70°C in heart infusion broth (Difco Laboratories, Detroit, Mich.) plus 20% glycerol. Before determining MICs, all isolates were subcultured on GC medium base (Difco), containing 1% (vol/vol) defined supplement (8), followed by incubation for 18 h at 35°C in an atmosphere containing 5% CO2. Penicillin-resistant isolates were tested for the production of fi-lactamase by using the chromogenic cephalosporin substrate, nitrocefin (13). MICs were determined by an agar dilution technique, and antibiotic-containing plates were inoculated by an adaptation of the method of Maier et al. (10). Antibiotic media consisted of GC medium base with 2% defined supplement to which the following antibiotics Organization isolates III, V, and VII (supplied by A. Reyn, Copenhagen) were used as control strains. The results were read after 18 h of incubation at 35°C in a 5% CO2 atmosphere. The MIC was considered to be that concentration of antibiotic which completely inhibited growth; the presence of one to nine colonies was accepted as being indicative of drug susceptibility. Table 1 shows the susceptibility of 517 non-,B-lactamase-producing isolates to penicillin, tetracycline, thiamphenicol, and chloramphenicol. Penicillin and tetracycline were more active than thiamphenicol and chloramphenicol; over 60% of the isolates was inhibited by concentrations of 0.25 U of penicillin or 0.25 ,ug of tetracycline per ml, as compared to under 30% inhibition by chloramphenicol and thiamphenicol at this concentration level. Over 90% of the isolates was inhibited by 2 jig of thiamphenicol or chloramphenicol per ml.In exa...