(P74) Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) based stable isotope labelling for rapid drug susceptibility testing in Neisseria gonorrhoeae.
Background- N. gonorrhoeae has developed resistance to various antimicrobials which were used in past to treat the gonococcal infections. There are numerous studies which have developed molecular methods for the determination of drug resistance in N. gonorrhoeae but these methods can’t predict resistance if multiple and unknown mechanisms of drug resistance are involved..The study was planned to develop a MALDI-TOF MS(Matrix-assisted laser desorption ionization-time of flight mass spectrometry) based stable isotope labelling technique for rapid prediction of drug susceptibility in N. gonorrhoeae and also which can detect the drug resistance irrespective of the mechanism underlying drug resistance
Methods:
Twenty five N. gonorrhoeae isolates were used for the present study. N. gonorrhoeae isolates cultured in three different setups were employed with normal lysine, heavy lysine (isotope) and heavy lysine with drug. After incubation spectra was acquired using MALDI-TOF MS and the acquired spectra were screened for media specific spectra to differentiate the drug susceptible and resistant isolates and compared with phenotypic antimicrobial susceptibility testing methods. The results of the same were reconfirmed by PCA dendrogram and virtual gel analysis.
Results:
A total 25 isolates were observed to have different antimicrobial susceptibility profiles. Resistance to all the tested drugs was observed except for the ceftriaxone and spectinomycin. A total of 22 isolates were resistant to ciprofloxacin and 3 were resistant to Azithromycin by phenotypic method. MALDI-TOF MS based SILAC (Stable isotope labeling by amino acids in cell culture) based drug resistance detection could characterize all the isolates to be susceptible and resistant to ciprofloxacin and azithromycin in less than 6 hrs.
Conclusions:
The results of the present method were in concordance with phenotypic method for antimicrobial susceptibility testing. SILAC is a promising approach for rapid detection of resistance in N. gonorrhoeae. Though, evaluation of the same is suggested in large number of isolates
