MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group Streptococci
Discrimination of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> group (SMG) species is still challenging but very important due to their different pathogenic potential. In this study, we aimed to develop a matrix-assisted laser desorption/ionization ti...
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MDPI AG
2021-09-01
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| Series: | Microorganisms |
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| author | Ilka D. Nix Evgeny A. Idelevich Andreas Schlattmann Katrin Sparbier Markus Kostrzewa Karsten Becker |
| author_facet | Ilka D. Nix Evgeny A. Idelevich Andreas Schlattmann Katrin Sparbier Markus Kostrzewa Karsten Becker |
| author_sort | Ilka D. Nix |
| collection | DOAJ |
| description | Discrimination of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> group (SMG) species is still challenging but very important due to their different pathogenic potential. In this study, we aimed to develop a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based optochin susceptibility test with an objective read-out. Optimal test performance was established and evaluated by testing consecutively collected respiratory isolates. Optochin in different concentrations as a potential breakpoint concentration was added to a standardized inoculum. Droplets of 6 µL with optochin and, as growth control, without optochin were spotted onto a MALDI target. Targets were incubated in a humidity chamber, followed by medium removal and on-target protein extraction with formic acid before adding matrix with an internal standard. Spectra were acquired, and results were interpreted as <i>S. pneumoniae</i> in the case of optochin susceptibility (no growth), or as non-<i>S. pneumoniae</i> in the case of optochin non-susceptibility (growth). Highest test accuracy was achieved after 20 h incubation time (95.7%). Rapid testing after 12 h incubation time (optochin breakpoint 2 µg/mL; correct classification 100%, validity 62.5%) requires improvement by optimization of assay conditions. The feasibility of the MALDI-TOF MS-based optochin susceptibility test was demonstrated in this proof-of-principle study; however, confirmation and further improvements are warranted. |
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| language | English |
| last_indexed | 2024-03-10T06:21:41Z |
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| series | Microorganisms |
| spelling | doaj.art-0617987e9c60415e9bdbee5dd398b1042023-11-22T19:12:46ZengMDPI AGMicroorganisms2076-26072021-09-01910201010.3390/microorganisms9102010MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group StreptococciIlka D. Nix0Evgeny A. Idelevich1Andreas Schlattmann2Katrin Sparbier3Markus Kostrzewa4Karsten Becker5Institute of Medical Microbiology, University Hospital Münster, 48149 Münster, GermanyInstitute of Medical Microbiology, University Hospital Münster, 48149 Münster, GermanyInstitute of Medical Microbiology, University Hospital Münster, 48149 Münster, GermanyBruker Daltonics GmbH & Co. KG, 28359 Bremen, GermanyBruker Daltonics GmbH & Co. KG, 28359 Bremen, GermanyInstitute of Medical Microbiology, University Hospital Münster, 48149 Münster, GermanyDiscrimination of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> group (SMG) species is still challenging but very important due to their different pathogenic potential. In this study, we aimed to develop a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based optochin susceptibility test with an objective read-out. Optimal test performance was established and evaluated by testing consecutively collected respiratory isolates. Optochin in different concentrations as a potential breakpoint concentration was added to a standardized inoculum. Droplets of 6 µL with optochin and, as growth control, without optochin were spotted onto a MALDI target. Targets were incubated in a humidity chamber, followed by medium removal and on-target protein extraction with formic acid before adding matrix with an internal standard. Spectra were acquired, and results were interpreted as <i>S. pneumoniae</i> in the case of optochin susceptibility (no growth), or as non-<i>S. pneumoniae</i> in the case of optochin non-susceptibility (growth). Highest test accuracy was achieved after 20 h incubation time (95.7%). Rapid testing after 12 h incubation time (optochin breakpoint 2 µg/mL; correct classification 100%, validity 62.5%) requires improvement by optimization of assay conditions. The feasibility of the MALDI-TOF MS-based optochin susceptibility test was demonstrated in this proof-of-principle study; however, confirmation and further improvements are warranted.https://www.mdpi.com/2076-2607/9/10/2010<i>Streptococcus pneumoniae</i>MALDI-TOF mass spectrometryoptochin susceptibility testingrapid testDOT-MGA |
| spellingShingle | Ilka D. Nix Evgeny A. Idelevich Andreas Schlattmann Katrin Sparbier Markus Kostrzewa Karsten Becker MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group Streptococci Microorganisms <i>Streptococcus pneumoniae</i> MALDI-TOF mass spectrometry optochin susceptibility testing rapid test DOT-MGA |
| title | MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group Streptococci |
| title_full | MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group Streptococci |
| title_fullStr | MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group Streptococci |
| title_full_unstemmed | MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group Streptococci |
| title_short | MALDI-TOF Mass Spectrometry-Based Optochin Susceptibility Testing for Differentiation of <i>Streptococcus pneumoniae</i> from other <i>Streptococcus mitis</i> Group Streptococci |
| title_sort | maldi tof mass spectrometry based optochin susceptibility testing for differentiation of i streptococcus pneumoniae i from other i streptococcus mitis i group streptococci |
| topic | <i>Streptococcus pneumoniae</i> MALDI-TOF mass spectrometry optochin susceptibility testing rapid test DOT-MGA |
| url | https://www.mdpi.com/2076-2607/9/10/2010 |
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