Abstract
Bacillus cereus plays an often unrecognized role in food borne diseases. Food poisoning caused by this pathogen is manifested by either diarrhea or emesis. Due to the relatively high prevalence of emetic toxin cereulide associated food poisoning, methods for simple and reliable detection of cereulide producing strains are of utmost importance. Recently, two different studies reported on the application of MALDI-ToF MS for either the differentiation of emetic and non-emetic strains of B. cereus or for direct detection of cereulide from bacterial colony smears. However, for implementation of cereulide detection using MALDI-ToF MS in routine microbiological diagnostics additional investigations on the sensitivity and specificity as well as on the fitting into common workflows for bacterial identification are needed. These aspects prompted us to investigate open issues and to test sample preparation methods, commonly used for microbial identification for their suitability to detect the emetic toxin from bacteria. Based on our experimental findings we propose a workflow that allows identification of B. cereus and sensitive detection of cereulide in parallel, using linear-mode MALDI-ToF MS equipment. The protocol was validated in a blinded study and is based on the well-established ethanol/formic acid extraction method. Cereulide is detected in the ethanol wash solution of samples identified as B. cereus as peaks at m/z 1175 and 1191. Peak position difference of 16 Th (Thomson) indicates detection of the sodium and potassium adducts of cereulide. This sample treatment offers possibilities for further characterization by more sophisticated LC-MS-based methods. In summary, the ease of use and the achieved level of analytical sensitivity as well as the wide-spread availability of MALDI-ToF MS equipment in clinical microbiological laboratories provides a promising tool to improve and to facilitate routine diagnostics of B. cereus associated food intoxications.
Highlights
Bacillus cereus is ubiquitously distributed in nature and commonly isolated from soil and food
Our study demonstrates that a routine sample preparation method for mL was analyzed by performing 5 (MALDI)-ToF mass spectrometry (MS) biotyping allows both, identification of B. cereus and parallel detection of cereulide with sufficiently high analytical sensitivity
The suitability of different MALDI-ToF MS biotyping workflows, such as direct transfer, ethanol/formic acid (FA) and trifluoroacetic acid (TFA) extraction, for detection of the emetic toxin was investigated in B. cereus F4810/72 grown on different solid agars, blood, LB and Caso
Summary
Bacillus cereus is ubiquitously distributed in nature and commonly isolated from soil and food. It is a well-recognized causative agent of two different types of gastrointestinal diseases mediated by toxins but is increasingly reported to be linked to non-gastrointestinal diseases, such as nosocomial or eye infections. The diarrheal form of food borne diseases is presumably caused by enterotoxin production of B. cereus in the intestine while the emetic syndrome is caused by the depsipeptide toxin cereulide, preformed in foods contaminated with emetic strains of B. cereus (Ehling-Schulz et al, 2019). Intoxication caused by cereulide leads to nausea and vomiting after 0.5–6 h incubation and lasts up to 24 h (EhlingSchulz et al, 2004). The emetic symptoms are usually self-limiting, severe cases, such as liver failure and acute encephalopathy, have been reported (RouzeauSzynalski et al, 2020). It was shown recently that cereulide is taken up by the body, efficiently translocated and accumulate in certain host organs and tissues (Bauer et al, 2018)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
