Introduction: Neisseria gonorrhoeae (NG) was originally highly susceptible to antimicrobials. The ongoing selective pressure allied to the bacterium’s ability to develop and retain resistance factors has been indicating the possibility of NG to evolve into untreatable forms. Therefore, constant monitoring of antimicrobial resistance and updates of treatment guidelines are mandatory. The aim of this study was to evaluate the evolution of NG antimicrobial resistance in a historical series of isolates from São Paulo/Brazil.
Methods A total of 173 NG isolates obtained between 2003 and 2016 from the STD/AIDS Reference and Training Centre of São Paulo were analysed. The bacterial species identification was confirmed by MALDI-TOF and the minimum inhibitory concentration (MIC) for penicillin (PEN), tetracycline (TET), ciprofloxacin (CIP), azithromycin (AZT), ceftriaxone (CRO) and cefixime (CFX) was determined by agar dilution.
Results The isolates were divided into two periods, from 2003 to 2010 and 2011 to 2016. The susceptibility profile for PEN did not differ between the two periods, 77.8% of the isolates had intermediate (I) and 19% resistant (R) from 2003 to 2010, while 74.5% I and 25.5% R from 2011 to 2016. The susceptibility profile for TET showed a different behaviour with more intermediates in the second period (59.6% I and 31.9% R) compared to the first period (29.4% I and 60.3% R). For AZT, there was an increase in the number of resistant isolates over the years: 0.8% I and 1.6% R (2003 to 2010), and 10.6% I and 12.8% R (2011 to 2016). CIP was the drug that presented the major difference between the periods with 86.5% of isolates being sensitive, 1.6% I and 11.9% R in the first period and 46.8% R in the second period. The isolates were 100% sensitive to cefixime and ceftriaxone.
Conclusion The study showed an increase in resistance to azithromycin and especially to ciprofloxacin. Ceftriaxone and cefixime isolates, both rarely used in clinic in Brazil, did not present resistance.