Bacillus “next generation” diagnostics: moving from detection toward subtyping and risk-related strain profiling

Monika Ehling-Schulz,Ute Messelhäusser

doi:10.3389/fmicb.2013.00032

Monika Ehling-Schulz, Ute Messelhäusser

Open Access

https://doi.org/10.3389/fmicb.2013.00032

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Abstract

The highly heterogeneous genus Bacillus comprises the largest species group of endospore forming bacteria. Because of their ubiquitous nature, Bacillus spores can enter food production at several stages resulting in significant economic losses and posing a potential risk to consumers due the capacity of certain Bacillus strains for toxin production. In the past, food microbiological diagnostics was focused on the determination of species using conventional culture-based methods, which are still widely used. However, due to the extreme intra-species diversity found in the genus Bacillus, DNA-based identification and typing methods are gaining increasing importance in routine diagnostics. Several studies showed that certain characteristics are rather strain-dependent than species-specific. Therefore, the challenge for current and future Bacillus diagnostics is not only the efficient and accurate identification on species level but also the development of rapid methods to identify strains with specific characteristics (such as stress resistance or spoilage potential), trace contamination sources, and last but not least discriminate potential hazardous strains from non-toxic strains.

Highlights

Proper diagnostic tools are of utmost importance, in the field of clinical and in the field of food and veterinary microbiology diagnostics
There are some studies reporting on the detection of B. cereus enterotoxins in non-B. cereus group Bacillus spp. (Rowan et al, 2001; Phelps and McKillip, 2002) and, more recently, a heat stable toxin, structural related to the B. cereus emetic toxin cereulide, has been found in a Paenibacillus tundrae strain (Rasimus et al, 2012)
Recent studies from different continents including isolates from diverse origins indicate the progressive emergence of pathotypes with novel toxin gene profiles (Thorsen et al, 2006; Ehling-Schulz et al, 2011a; Chon et al, 2012), confronting food industry and food microbiology labs with potential novel hazards

Summary

INTRODUCTION

Proper diagnostic tools are of utmost importance, in the field of clinical and in the field of food and veterinary microbiology diagnostics. With the increase of genetic information and the description of more and more so-called “borderline” strains (Klee et al, 2006; Fricker et al, 2008), a refinement of the current nomenclature might become necessary Due to their different risk potentials, ranging from risk group 1 to risk group 3, the members of the B. cereus group are still handled as separate species. Recent studies from different continents including isolates from diverse origins indicate the progressive emergence of pathotypes with novel toxin gene profiles (Thorsen et al, 2006; Ehling-Schulz et al, 2011a; Chon et al, 2012), confronting food industry and food microbiology labs with potential novel hazards. It has been shown that the toxigenic potential among emetic as well as enterotoxic strains can vary substantially (see, e.g., Moravek et al, 2006; Stark et al, 2013)

POPULATION STUDIES AND CONTAMINATION ROUTE ANALYSIS

Economic relevance

Findings

CONCLUSION AND FUTURE PERSPECTIVES