Comparison between Rapid ID 32 Strep System, Matrix Assisted Laser Desorption Ionisation–Time of Flight Mass Spectrometry and 16S rRNA gene sequence analysis for the species identification of Enterococcus spp. isolated from water

“Matrix-Assisted Laser Desorption Ionisation–Time of Flight Mass Spectrometry (MALDI–TOF MS) has
increasingly been used for rapid and reliable identification of clinically relevant micro-organisms. To
establish the applicability of this technique in (drinking) water quality analysis, the MALDI–TOF MS
identification results for Enterococcus spp. isolated from various water environments were
compared with those obtained using the commercial Rapid 32 ID Strep system. One hundred and one
bacterial isolates were isolated from various types of water and determined as enterococci on the
basis of their growth on Slanetz-Bartley agar in typical colonies. The isolates were identified by
MALDI–TOF MS and the commercial biochemical test Rapid 32 ID Strep. Isolates yielding in discrepant
identifications were genotyped using 16S rRNA gene sequence analysis. For 86 isolates (85%), the
results of Rapid ID 32 Strep were identical to those obtained with MALDI–TOF MS. Six isolates were
impossible to be classified by means of the Rapid 32 ID Strep test. And for eight out of a total of nine
discrepant results (89%), the 16S analyses confirmed the MALDI–TOF MS identification. MALDI–TOF
MS produced highly reproducible results. These results indicated that the use of two different culture
media had no effect on the identification. In addition, no significant differences (p ¼ 0.32; n ¼ 20)
were evident between the scores obtained from a 20-fold measurement of the same isolate. The
results of this study showed that MALDI–TOF MS identification (Bruker) is a reliable method for
identifying E. faecium, E. faecalis, E. durans, E. hirae and E. casseliflavus isolated from water
samples. E. mundtii and E. moraviensis were not included in the Rapid 32 ID Strep database and
could therefore not be identified using that test set. However, MALDI–TOF MS and 16S identified all
six isolates as members of these species.”
(Citaat: Taucer-Kapteijn, M., Medema, G.J., Hoogenboezem, W. Comparison between Rapid I 32 Strep System, Matrix Assisted Laser Desorption Ionisation-Time of Flight Mass Spectrometry and 16S rRNA gene sequence analysis for the species identification of Enterococcus spp. isolated from water – Water Science &Technology: Water Supply 13(2013)5, p.1383-1389)