Introduction The emergence of multidrug resistance in N. gonorrhoeae highlights the need to consider alternatives for future therapeutic use. Nowadays, the aminoglycoside gentamicin is considered a possible treatment option for gonorrhoea, particularly in dual therapy. Gentamicin has been used successfully for several years in the treatment of gonococcal urethritis in Malawi. However, treatment failures have been reported. In Argentina, N. gonorrhoeae isolates with multiple resistance profiles to different antimicrobials, including cefixime and ceftriaxone, have been detected. Therefore, the knowledge of the susceptibility to new antimicrobial options for gonorrhoea treatment is required. The aim of this study was to determine the susceptibility to gentamicin of N. gonorrhoeae isolates with different resistance profiles in 2013 and 2015.
Methods We studied 237 N. gonorrhoeae isolates obtained in 2013 and 2015 from the GASSP-AR. The MICs to penicillin, tetracycline, ciprofloxacin, cefixime, ceftriaxone, azithromycin and gentamicin were determined by the agar dilution test according to CLSI guidelines.
Results Gentamicin MICs ranged from 2 to 16 µg/ml. The MIC50 and MIC90 were 8 µg/ml. The rate of isolates with MIC 8 µg/ml was 67.1%, while 30.4% showed a MIC of 4 µg/ml. A 75.5% of the isolates included in this study showed resistance to one or more of the following antibiotics: penicillin (40.5%), tetracycline (30.4%), ciprofloxacin (59.9%), and 5.5% of the isolates showed decreased susceptibility to cefixime and ceftriaxone. A total of 15 resistance phenotypes were found, with phenotypes QRNG and PPNG being more frequent.
Conclusion Although N. gonorrhoeae isolates with resistance to gentamicin were not observed, a high percentage of strains were resistant to other antimicrobial agents, particularly ciprofloxacin. This study suggests that gentamicin may be considered a future treatment option for gonorrhoea in Argentina. However, the high prevalence of isolates with MIC 8 µg/ml (intermediate susceptibility) suggests a continuous surveillance of gentamicin in our country.