Background Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) is a highly discriminatory technique for assessing the genetic diversity of N. gonorrhoeae and has also been put forward as a tool for predicting specific antimicrobial resistance (AMR) phenotypes. Therefore, the present study was undertaken to investigate the molecular epidemiology of N. gonorrhoeae isolates using NG-MAST in Delhi and to examine if it can be used as a means for predicting AMR. This is the first such research performed in this country.
Methods 100 consecutive gonococcal isolates between April 2010 to October 2013 were investigated. Antimicrobial susceptibility testing was done using disc diffusion method and E test and the results interpreted using the breakpoint criteria of CDS technique. NG-MAST was performed as described previously. WHO N. gonorrhoeae reference strains F, G, K-P were used as controls. Association between NG-MAST sequence type (ST) and antimicrobial susceptibility was probed using chi-square and fisher’s exact tests.
Results Rates of resistance to classical antibiotics were high. Decreased susceptibility to ceftriaxone (MIC 0.032–0.25 µg/ml) was demonstrated in 5% while azithromycin resistance (MIC ≥1 µg/ml) was seen in 4% isolates. N. gonorrhoeae isolates were assigned into 60 different STs and 43 (71.6%) have not been reported previously to the international database. The most common ST was 6058 (21%), followed by ST 9774 (4%), ST9875 (4%), ST9783 (4%) and ST2990 (3%). The majority of the STs (76.6%) were represented by a single isolate. There was significant association between ST6058 and resistance to penicillin (p = 0.00) and tetracycline (p = 0.002). In all the other antibiotics, no association was found.
Conclusion Our work reflects a highly diversified gonococcal population in Delhi. Further, NG-MAST has a limited applicability as a tool for predicting AMR in our region. A detailed investigation on a large number of representative isolates may provide insight into sexual networks in the city.
Disclosure of interest statement None.
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