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Updated: Aug 21, 2025
Identification of Fatty Acids in Bacillus cereus
Published on: December 5, 2016
Diagnostic challenges within the Bacillus cereus-group: finding the beast without teeth
Veronika Muigg1, Aline Cuénod2, Srinithi Purushothaman2
1Clinical Bacteriology and Mycology, University Hospital Basel, Basel, Switzerland.
Abstract:
The Bacillus cereus-group (B. cereus sensu lato) includes common, usually avirulent species, often considered contaminants of patient samples in routine microbiological diagnostics, as well as the highly virulent B. anthracis. Here we describe 16 isolates from 15 patients, identified as B. cereus-group using a MALDI-TOF MS standard database. Whole genome sequencing (WGS) analysis identified five of the isolates as B. anthracis species not carrying the typical virulence plasmids pXO1 and pXO2, four isolates as B. paranthracis, three as B. cereus sensu stricto, two as B. thuringiensis, one as B. mobilis, and one isolate represents a previously undefined species of Bacillus (B. basilensis sp. nov.). More detailed analysis using alternative MALDI-TOF MS databases, biochemical phenotyping, and diagnostic PCRs, gave further conflicting species results. These cases highlight the difficulties in identifying avirulent B. anthracis within the B. cereus-group using standard methods. WGS and alternative MALDI-TOF MS databases offer more accurate species identification, but so far are not routinely applied. We discuss the diagnostic resolution and discrepancies of various identification methods.
Insights
Accurate identification of Bacillus cereus group bacteria is challenging. Whole genome sequencing and advanced databases improve species identification, crucial for distinguishing virulent from avirulent strains.
Area of Science:
- Microbiology
- Genomics
- Bacterial Pathogenesis
Background:
- The Bacillus cereus group encompasses diverse species, ranging from harmless contaminants to the virulent Bacillus anthracis.
- Standard diagnostic methods often struggle to differentiate closely related species within this group.
Purpose of the Study:
- To evaluate the accuracy of various identification methods for Bacillus cereus group isolates.
- To highlight discrepancies between standard and advanced techniques in species delineation.
Main Methods:
- Whole genome sequencing (WGS) for precise genetic analysis.
- Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) with standard and alternative databases.
- Biochemical phenotyping and diagnostic PCR.
Main Results:
- WGS identified Bacillus anthracis strains lacking typical virulence plasmids, alongside other species like B. paranthracis, B. cereus sensu stricto, and B. thuringiensis.
- Conflicting species identification results were observed across different methods, including MALDI-TOF MS, biochemical tests, and PCR.
- One isolate represented a novel species, Bacillus basilensis sp. nov.
Conclusions:
- Standard microbiological diagnostics face significant challenges in accurately identifying Bacillus cereus group species, particularly avirulent Bacillus anthracis.
- WGS and advanced MALDI-TOF MS databases provide superior accuracy but are not yet routine clinical tools.
- Discrepancies underscore the need for improved diagnostic strategies for this complex bacterial group.
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