Antimicrobial susceptibility of non-penicillinase and penicillinase-producing Neisseria gonorrhoeae strains isolated in Tripoli, Libya.

Neisseria gonorrhoeae culture gave a positive result in 42 of 64 male adults with purulent urethral discharge. The majority of the infections were acquired outside Libya. Twenty-seven strains (64.3%) were non-penicillinase producing (NPPNG) and 15 (35.7%) were penicillinase producing (PPNG) by starch paper technique. Antimicrobial susceptibility of the strains to 5 antibiotics was carried out by agar-plate dilution technique. Twenty-three NPPNG strains (54.8%) were susceptible to penicillin with a minimum inhibitory concentration (MIC) of less than or equal to 0.5 micrograms/ml. In 4 strains (9.5%), a high resistance to penicillin (MIC greater than or equal to 16 micrograms/ml) appeared to be chromosomally-mediated (CMRNG). All PPNG strains were resistant to penicillin (MIC greater than or equal to 1 microgram/ml). While resistance to erythromycin (MIC greater than or equal to 1 microgram/ml) and tetracycline (MIC greater than or equal to 1 microgram/ml) was observed in 5 strains, resistance to kanamycin (MIC 32 micrograms/ml) and spectinomycin (MIC 64 micrograms/ml) was present in only one strain. Whereas no significant differences were recorded in MICs of erythromycin, tetracycline, kanamycin and spectinomycin between NPPNG and PPNG strains, one PPNG strain was found to be resistant in vitro to all 5 antibiotics.