Genetic diversity of clinical isolates of <it>Bacillus cereus </it>using multilocus sequence typing

• Main Authors: Pruckler James M, Helsel Leta, Gee Jay E, Marston Chung K, Novak Ryan T, Hoffmaster Alex R, Wilkins Patricia P
• Format: Article
• Language: English
• Published: BMC 2008-11-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/8/191

<p>Abstract</p> <p>Background</p> <p><it>Bacillus cereus </it>is most commonly associated with foodborne illness (diarrheal and emetic) but is also an opportunistic pathogen that can cause severe and fatal infections. Several multilocus sequence typing (MLST) schemes have recently been developed to genotype <it>B. cereus </it>and analysis has suggested a clonal or weakly clonal population structure for <it>B. cereus </it>and its close relatives <it>B. anthracis </it>and <it>B. thuringiensis</it>. In this study we used MLST to determine if <it>B. cereus </it>isolates associated with illnesses of varying severity (e.g., severe, systemic vs. gastrointestinal (GI) illness) were clonal or formed clonal complexes.</p> <p>Results</p> <p>A retrospective analysis of 55 clinical <it>B. cereus </it>isolates submitted to the Centers for Disease Control and Prevention between 1954 and 2004 was conducted. Clinical isolates from severe infections (n = 27), gastrointestinal (GI) illness (n = 18), and associated isolates from food (n = 10) were selected for analysis using MLST. The 55 isolates were diverse and comprised 38 sequence types (ST) in two distinct clades. Of the 27 isolates associated with serious illness, 13 clustered in clade 1 while 14 were in clade 2. Isolates associated with GI illness were also found throughout clades 1 and 2, while no isolates in this study belonged to clade 3. All the isolates from this study belonging to the clade 1/cereus III lineage were associated with severe disease while isolates belonging to clade1/cereus II contained isolates primarily associated with severe disease and emetic illness. Only three STs were observed more than once for epidemiologically distinct isolates.</p> <p>Conclusion</p> <p>STs of clinical <it>B. cereus </it>isolates were phylogenetically diverse and distributed among two of three previously described clades. Greater numbers of strains will need to be analyzed to confirm if specific lineages or clonal complexes are more likely to contain clinical isolates or be associated with specific illness, similar to <it>B. anthracis </it>and emetic <it>B. cereus </it>isolates.</p>