Antimicrobial susceptibilities of strains of Neisseria gonorrhoeae in Bangkok, Thailand: 1994-1995

Abstract

Background and objectives: Failure of uncomplicated gonococcal infections acquired in the Far East to respond to doses of ciprofloxacin and ofloxacin recommended by the Centers for Disease Control and Prevention have been identified in Australia, the United Kingdom, and the United States. In the Republic of the Philippines, 54.3% of strains exhibited decreased susceptibility to fluoroquinolones; 12% of strains were resistant to ciprofloxacin. This study was undertaken to compare the antimicrobial susceptibilities of gonococcal isolates in Bangkok, Thailand, with those in the Republic of the Philippines.

Goal: To determine the frequency and diversity of antimicrobial resistance, particularly to fluoroquinolones, in gonococcal strains in Bangkok, Thailand.

Study design: Strains of Neisseria gonorrhoeae isolated from 101 patients with uncomplicated gonorrhea in Bangkok, Thailand, in July, 1994 (46 strains) and November, 1994 to July, 1995 (55 strains), were characterized by auxotype/serovar class, antimicrobial susceptibilities, and plasmid profile. Susceptibilities were determined to penicillin G, tetracycline, ceftriaxone, cefixime, cefoxitin, ciprofloxacin, ofloxacin, norfloxacin, erythromycin, kanamycin, and thiamphenicol.

Results: Of 101 strains, 89.1% (90/101) were resistant to penicillin or tetracycline. Plasmid-mediated resistance to penicillin or tetracycline was identified in 33.7% (34/101) of the isolates: penicillinase-producing Neisseria gonorrhoeae (17.8%; 18/101), tetracycline-resistant Neisseria gonorrhoeae (7.9%; 8/101), and penicillinase-producing/tetracycline-resistant Neisseria gonorrhoeae (7.9%; 8/101). Most penicillinase-producing strains (96.2%; 25/26) possessed the 4.4-megadalton (Md) beta-lactamase plasmid; one strain possessed the 3.2-Md beta-lactamase plasmid. Chromosomally mediated resistance to penicillin and tetracycline was exhibited by 51.5% (52/101) of strains, and 4.0% (4/101) were tetracycline resistant. All strains were susceptible to spectinomycin. Of 21.8% (22/101) strains exhibiting decreased susceptibility to ciprofloxacin (minimal inhibitory concentration [MIC] > or = 0.125 microgram/ml), one strain (ciprofloxacin MIC, 0.5 microgram/ml; ciprofloxacin inhibition zone diameter of 23 mm) had MICs of 2.0 and 8.0 micrograms/ml for ofloxacin and norfloxacin, respectively, indicating resistance to these agents. Decreased susceptibility to ciprofloxacin was identified in strains with chromosomally mediated resistance to penicillin or tetracycline and in penicillinase-producing strains.

Conclusions: In Bangkok, Thailand, gonococcal isolates exhibit resistance to penicillin, tetracycline, kanamycin, and thiamphenicol. Decreased susceptibility to fluoroquinolones is emerging in a variety of strains of N. gonorrhoeae. Thus, all gonococcal infections should be treated with antimicrobial therapies known to be active against all gonococcal strains to reduce the spread of strains exhibiting decreased susceptibilities to fluoroquinolones.

PIP: To assess the frequency and diversity of antimicrobial resistant strains of Neisseria gonorrhoeae in Thailand, endocervical or urethral strains were isolated from 101 patients at a Bangkok sexually transmitted disease clinic. Of the 101 strains, 90 (89.1%) were resistant to penicillin or tetracycline. Plasmid-mediated resistance to penicillin or tetracycline was found in 33.7% of isolates; this included penicillinase-producing N gonorrhoeae (17.8%), tetracycline-resistant N gonorrhoeae (7.9%), and penicillinase-producing/tetracycline-resistant N gonorrhoeae (7.9%). Moreover, 51.5% of all strains exhibited chromosomally mediated resistance to penicillin and tetracycline. All strains were susceptible to spectinomycin. 22 strains (21.8%) showed decreased susceptibility to ciprofloxacin, while another fifth demonstrated resistance to both fluoroquinolones and norfloxacin. Finally, more than 75% of strains exhibited decreased susceptibility to kanamycin and thiamphenicol. The penicillin/tetracycline resistance phenotypes identified in Bangkok were more similar to those of isolates in the US than in the Philippines, where decreased susceptibility to fluoroquinolones predominates. Given evidence of antimicrobial resistance to penicillin, tetracycline, kanamycin, thiamphenicol, and fluoroquinolones in Thailand, the choice of agents for the treatment of uncomplicated gonococcal infection should be considered carefully and periodic surveillance of antimicrobial resistance is recommended to permit timely revision of treatment protocols.