PUBLIC HEALTH IMPACT OF RAPID IDENTIFICATION OF EPIDEMIOLOGICALLY IMPORTANT CHARACTERISTICS OF SALMONELLA SPP. BY MALDI-TOF MS
Introduction: Infections caused by Salmonella are an ongoing worldwide public health problem, often found as a source of nosocomial infections, which cause significant socio-economic burdens. Salmonella is a major food-borne pathogen causing primarily gastrointestinal diseases as well as other localized and systemic infections and extraintestinal complications. MALDI-TOF MS is a new method used by clinical laboratories for rapid, reliable, cost-effective and user-friendly diagnosis of many medical important bacteria of public health interest. The use of this technique improves early identification of genus Salmonella on the species, subspecies and even serovar level, which has a positive impact on public health.
Objectives: The aim of the study was to evaluate the importance of MALDI-TOF mass spectrometry for rapid identification of epidemiologically important Salmonella serovars. Based on the latest knowledge about specific biomarker molecules the possibility to identify Salmonella enterica subsp. enterica serovar Enteritidis was verified, which is one of the most common serovars present in Europe associated with gastrointestinal diseases. For serovar Enteritidis a unique mass peak at m/z 6,036 was used.
Methods: 140 clinical Salmonella isolates were collected from January to October 2017. Serotyping of Salmonella species, subspecies and serovars was performed by slide agglutination technique: 139 isolates were identified as Salmonella enterica subsp. enterica and one isolate as Salmonella enterica subsp. diarizonae (IIIb). From 139 isolates of Salmonella enterica subsp. enterica the following serovars were detected: 108 Enteritidis, 12 Typhimurium, 6 Infantis, 3 Agona, 3 Derby, 7 others. All isolates were identified also by MALDI-TOF MS as Salmonella spp. For all isolates a unique mass peak at m/z 6.036 was used, which is considered to be relevant for serovar Enteritidis according to the most recent known data.
Results: 103 isolates from a total of 108 slide agglutination positive isolates for serovar Enteritidis showed a specific mass signal at m/z 6,036 (+/-). 5 isolates did not contain this specific protein. After repeated analysis from re-culture, the specific protein was found also in the remaining 5 isolates. 32 serovars other than Enteritidis did not contain this specific biomarker molecule.
Conclusion: We can confirm that MALDI-TOF MS is a rapid and reliable method to identify of the most common serovar Salmonella Enteritidis based on the diagnostic marker peak at m/z 6,036 identified by recent studies. This unique mass signal showed 100% specificity and 95% sensitivity for Enteritidis serovar in our study. We can conclude that the determination of this frequently present serovar is significantly accelerated by MALDI-TOF MS. The rapid and reliable diagnosis is important for the early treatment and prevention of the spread of salmonellosis with a positive impact on public health.
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