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

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.

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.

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.

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.

Surveillance programmes to monitor levels of antibiotic resistant isolates are essential to ensure therapeutic success.