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Rapid Discrimination of Pseudomonas aeruginosa ST175 Isolates Involved in a Nosocomial Outbreak Using MALDI-TOF Mass
Ana Candela1,2, Manuel J Arroyo3, María Sánchez-Cueto1,2
1Clinical Microbiology and Infectious Diseases Department, Hospital General Universitario Gregorio Marañón, Madrid, Spain.
Abstract:
The goal of this study was to evaluate matrix-assisted laser desorption ionization-iime of flight mass spectrometry (MALDI-TOF MS) and Fourier-transform infrared spectroscopy (FTIR-S) as diagnostic alternatives to DNA-based methods for the detection of Pseudomonas aeruginosa sequence type (ST) 175 isolates involved in a hospital outbreak. For this purpose, 27 P. aeruginosa isolates from an outbreak detected in the Hematology department of our hospital were analyzed by the above-mentioned methodologies. Previously, these isolates had been characterized by pulse-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS). Besides, eight P. aeruginosa isolates were analyzed as unrelated controls. MALDI-TOF MS spectra were acquired by transferring several colonies onto the MALDI target and covering them with 1 µl of formic acid 100% and 1 µl of α-ciano-3,4-hidroxicinamic acid matrix. For the analysis with FTIR-S, colonies were resuspended in 70% ethanol and sterile water according to the manufacturer's instructions. Spectra from both methodologies were analyzed using Clover Biosoft Software, which allowed data modeling using different algorithms and validation of the classifying models. Three outbreak-specific biomarkers were found at 5,169, 6,915, and 7,236 m/z in MALDI-TOF MS spectra. Classification models based on these three biomarkers showed the same discrimination power displayed by PFGE. Besides, K-nearest neighbor algorithm allowed the discrimination of the same clusters provided by WGS and the validation of this model achieved 97.0% correct classification. On the other hand, FTIR-S showed a discrimination power similar to PFGE and reached correct discrimination of the different STs analyzed. In conclusion, the combination of both technologies evaluated, paired with machine learning tools, may represent a powerful tool for real-time monitoring of high-risk clones and isolates involved in nosocomial outbreaks.
Insights
Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and Fourier-transform infrared spectroscopy (FTIR-S) show promise for detecting Pseudomonas aeruginosa outbreaks. These methods, combined with machine learning, offer rapid identification of high-risk bacterial clones.
Area of Science:
- Clinical Microbiology
- Infectious Disease Diagnostics
- Spectroscopic Analysis
Background:
- Nosocomial outbreaks caused by *Pseudomonas aeruginosa* pose significant challenges in healthcare settings.
- Traditional DNA-based methods for bacterial strain typing can be time-consuming and resource-intensive.
- Rapid and accurate detection of outbreak-specific bacterial clones is crucial for effective infection control.
Purpose of the Study:
- To evaluate matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and Fourier-transform infrared spectroscopy (FTIR-S) as rapid diagnostic alternatives.
- To assess the utility of these methods for detecting *Pseudomonas aeruginosa* sequence type (ST) 175 isolates during a hospital outbreak.
- To compare the discriminatory power of MALDI-TOF MS and FTIR-S against established methods like pulse-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS).
Main Methods:
- Analysis of 27 *P. aeruginosa* isolates from a hospital outbreak using MALDI-TOF MS and FTIR-S.
- Spectra acquisition involved specific sample preparation protocols for each technique.
- Data analysis utilized Clover Biosoft Software with machine learning algorithms (e.g., K-nearest neighbor) for classification and validation.
Main Results:
- MALDI-TOF MS identified three outbreak-specific biomarkers (5,169, 6,915, and 7,236 m/z) with discriminatory power comparable to PFGE.
- A classification model based on these biomarkers achieved 97.0% correct classification, discriminating clusters similar to WGS.
- FTIR-S demonstrated discriminatory power similar to PFGE and successfully differentiated the analyzed sequence types (STs).
Conclusions:
- MALDI-TOF MS and FTIR-S, when combined with machine learning tools, are effective alternatives to DNA-based methods for outbreak detection.
- These spectroscopic techniques offer a powerful approach for real-time monitoring of high-risk bacterial clones in healthcare environments.
- The study highlights the potential for rapid, cost-effective identification of pathogens involved in nosocomial infections.
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