Antimicrobial agents and gonorrhoea: therapeutic choice, resistance and susceptibility testing.

INTRODUCTION: Neisseria gonorrhoeae, the causative agent of gonorrhoea is a particularly well adapted pathogen that has continued to evolve mechanisms to evade treatment with antimicrobial agents. THERAPEUTIC CHOICE: The choice of antibiotic for use in the first-line treatment of gonorrhoea should be made with knowledge of the susceptibility of the isolates of N gonorrhoeae to be encountered. RESISTANCE: High-level resistance to penicillin and tetracycline in N gonorrhoeae is plasmid-mediated and a major therapeutic problem. Penicillinase-producing N gonorrhoeae, first described in 1976, have now spread worldwide and tetracycline-resistant N gonorrhoeae, described in 1985, are becoming increasingly prevalent. Chromosomal resistance to penicillin is low-level and affects a range of antibiotics. High-level resistance to spectinomycin has been sporadic and has not limited its use whereas the emergence of resistance to ciprofloxacin will have a significant impact on its use for gonorrhoea. SUSCEPTIBILITY TESTING: A variety of methods are available including disc diffusion, breakpoint agar dilution technique, E-test and determination of the minimum inhibitory concentration (MIC). The choice of methodology will depend on the number and type of isolates and the facilities available for testing. DISCUSSION: Surveillance programmes to monitor levels of antibiotic resistant isolates are essential to ensure therapeutic success.