Using agar dilution, we determined MICs of penicillin, cefoxitin, ceftriaxone, cefmetazole, tetracycline, and spectinomycin for 129 strains of Neisseria gonorrhoeae. All strains were susceptible to ceftriaxone (MIC range, .0.008 to 0.06 ,ug/ml) and spectinomycin (16 to 32 ,ug/ml). The MICs for 50, 90, and 100% of strains tested were 1.0, 2.0, and >8.0 ,ug/ml; 0.12, 1.0, and >8.0 ,Ig/ml; 0.5, 1.0, and 2.0 ,ug/ml; and 1.0, 2.0, and >8.0 ,ug/ml for cefmetazole, penicillin, cefoxitin, and tetracycline, respectively. Seven strains were Il-lactamase producers; eight were chromosomally resistant to penicillin. There was a log-linear relation for non-P-lactamase-producing strains between the MICs of cefmetazole, cefoxitin, and tetracycline and the MIC of penicillin (Pearson r = 0.787, 0.544, and 0.358, respectively).The treatment strategy for presumed or microbiologically documented gonorrheal infection has changed in the light of new information regarding the susceptibility of Neisseria gonorrhoeae to penicillin and tetracycline (6). Most laboratories do not test each strain for antimicrobial susceptibilities; thus clinicians rely on epidemiologic data from regional or national authorities to guide therapy. Cephalosporins such as cefoxitin and ceftriaxone have been widely used as primary therapy for gonorrhea. The purpose of our study was to determine the susceptibility patterns of N. gonorrhoeae, collected from men seen at clinics in two urban Philadelphia neighborhoods, to five drugs commonly used in the treatment of gonorrhea: penicillin, tetracycline, spectinomycin, cefoxitin, and ceftriaxone. We also tested the activity of cefmetazole, a novel cephalosporin being used in clinical trials, as chemotherapy for gonorrhea. We determined the incidence of penicillin resistance due to ,-lactamase production, and we examined the relation between susceptibility to penicillin and susceptibility to other antibiotics among non-3-lactamase-producing strains.
MATERIALS AND METHODSBetween March and October 1987, isolates of N. gonorrhoeae were collected from men seen at Episcopal Hospital and women seen at Temple University Hospital, both in north Philadelphia. The isolates were identified in the clinical microbiology laboratories by growth on Thayer-Martin agar, Gram stain appearance, oxidase activity, and coagglutination with monoclonal antibodies (Phadebact Monoclonal GC Omni Test; Pharmacia Diagnostics, Piscataway, N.J.) or by carbohydrate utilization (Fastidious Fermenters Duo Tubes and Trio Tubes; Carr-Scarborough Microbiologicals, Inc., Decatur, Ga.). Isolates were frozen at -70°C in 1-ml samples of Trypticase soy broth (BBL Microbiology Systems, Cockeysville, Md.) with 20% glycerol until they were thawed for batch susceptibility testing. The control strain was a laboratory isolate whose susceptibilities to penicillin and tetracycline were determined by agar dilution in a previous experiment (data not published). ,-Lactamase activity was * Corresponding author. determined by the chromogenic cephalosporin assay (Cefinase; B...