Neisseria gonorrhoeae strains isolated in Hong Kong: in vitro susceptibility to 13 antibiotics

Abstract

Fifty-five Neisseria gonorrhoeae strains isolated in Hong Kong over a period of 6 months were tested for their in vitro susceptibility to 13 antimicrobial agents by the agar dilution method. Six strains were beta-lactamase producing. In addition, five beta-lactamase strains from Singapore were tested. Among the non-beta-lactamase-producing strains, 34 (62%) had intermediate resistance to penicillin, with minimal inhibitory concentrations (MICs) ranging from 0.125 to 0.5 microgram/ml, and 15 strains were fully susceptible to penicillin (MICs, 0.015 to 0.06 microgram/ml). The MICs of penicillin for all beta-lactamase-producing strains were 2 microgram/ml, and the strains were resistant to ampicillin. Although a direct correlation between the MICs for resistance to penicillin and the other antibiotics tested was not observed, the gonococci isolated in Hong Kong were notably more resistant to tetracycline and streptomycin than has been reported elsewhere, with 78% of strains requiring for inhibition an MIC of tetracycline of greater than 2 microgram/ml and 51% of the isolates requiring an MIC of streptomycin of greater than 128 microgram/ml. All strains were susceptible to spectinomycin and kanamycin as well as to sulfamethoxazole-trimethoprim (ratio, 19:1). Among the cephalosporins, the order of effectiveness was cefuroxime, cefamandole, and cefoxitin. The older generation of cephalosporins, cephradine and cephalexin, was the least effective: 45 and 37% of the strains, respectively, required for inhibition MICs of greater than or equal to 8 microgram/ml. Cefotaxime, a new parenteral cephalosporin, was the most active; the median MIC was at least 10-fold lower than that of cefuroxime.