Background In India, knowledge regarding N. gonorrhoeae antimicrobial resistance profiling is limited, and data concerning genetic characteristics of N. gonorrhoeae is also lacking. Herein, we investigated the genetic resistance determinants for various antimicrobials used against N. gonorrhoeae isolated in Delhi, India. Various studies have shown that this resistance towards antimicrobials could be either plasmid or chromosomal mediated involving mutations in various genes.
Methods Molecular basis of plasmid and chromosomal mediated antimicrobial resistance was analysed by amplifying and sequencing the most target genes, pen A and por B, of N. gonorrhoeae. Attempts have been made to in-silico model the structure of mutant PenA to understand how mutations in these genes affect the drug binding. A PCR assay was also carried out to analyse the penicillinase producing N. gonorrhoeae (PPNG).
Results Out of the 40 clinical isolates of N. gonorrhoeae studied which were resistant to various antimicrobials, twenty eight isolates showed high resistance to penicillin (3–32µg/ml). These resistant isolates were PPNG positive (70%; 28/40) and predominantly harboured the African type of PPNG plasmid. Only two isolates carried the Asian type of plasmid. Mutations were also observed in penA and porB genes which correlate their effects on drug resistance. Through in silico modelling studies, we were able to even show that a single point mutation at G452S in penA gene changed the susceptibility of N. gonorrhoeae towards penicillin and tetracycline.
Conclusions This study clearly shows a cumulative effect of increasing mutations with subsequent increase in resistance towards various antimicrobials. Presence of both African and Asian type of penicillinase producing plasmid gives an indication of extensive travel of patients affected with Gonorrhea. Our in silico modelling studies of mutant proteins provide new insights to access increasing antimicrobial resistance among Neisseria gonorrhoeae.
- Antimicrobial Resistance