Analysis of Neisseria gonorrhoeae susceptibility trends (MIC creep) from North India: A 15-years' experience!

Abstract

Background Neisseria gonorrhoeae (NG) is a highly transformable strict human pathogen with the potential to evolve into a 'superbug' Resource-limited settings like ours rely on the syndromic diagnostic approach recommended by the WHO and adopted by the National AIDS Control Organisation (NACO) for the management of sexually transmitted infections (STIs). The 'Grey kit" comprising of cefixime 400 mg and azithromycin 1 gm is recommended for genitourinary discharge in India. Aim The objective of this study was to examine putative changes in minimum inhibitory concentration (MICs) of ceftriaxone/cefixime and azithromycin during a ∼15-year period to assess the need for dosage adjustment. Methods All clinical isolates of NG obtained from patients attending the STI clinic of our hospital were included in the study. The MIC for penicillin, tetracycline, ciprofloxacin, ceftriaxone, cefixime, azithromycin, and spectinomycin was determined using the E-test method. The results were interpreted according to the Calibrated Dichotomous Sensitivity (CDS) criteria except for azithromycin (up to 2011) and cefixime, where Clinical & Laboratory Standards Institute (CLSI) guidelines were used. We analysed our data by years (2008-2012 vs. 2013-2017) and examined the limited data available thereafter until June 2023 (in light of COVID). MIC50 and MIC90 (MIC values that stop the growth of 50% and 90% of bacterial isolates respectively) data were analysed for determination of MIC creep. Results A total of 183 NG isolates were collected during the study period (151 during 2008-2017 and 32, 2018 onwards). All isolates were from male patients presenting with urethritis. High resistance levels were observed for penicillin, tetracycline, and ciprofloxacin, but decreased susceptibility to ceftriaxone or cefixime remained (<10%), as did resistance to azithromycin (<5%). Notably, no ceftriaxone resistance was detected over the ∼15-year period, and no significant increase in MIC (MIC creep) was observed for ceftriaxone and azithromycin. Only two isolates showed concurrent resistance to azithromycin and decreased susceptibility to ceftriaxone. All isolates were susceptible to spectinomycin. Limitations The clinical isolates were obtained from a single site, and the numbers were limited. There is a paucity of data during the COVID-19 pandemic due to limited clinical services being offered. Conclusion There appears to be no immediate threat to the therapies currently being used in syndromic management for genitourinary discharge. However, MIC-based monitoring of crucial antimicrobials is imperative.