Hoffmaster Alex R, Novak Ryan T, Marston Chung K, Gee Jay E, Helsel Leta, Pruckler James M, Wilkins Patricia P
National Center for Zoonotic, Vector-borne, and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, USA.
BMC Microbiol. 2008 Nov 6;8:191. doi: 10.1186/1471-2180-8-191.
Bacillus cereus 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 B. cereus and analysis has suggested a clonal or weakly clonal population structure for B. cereus and its close relatives B. anthracis and B. thuringiensis. In this study we used MLST to determine if B. cereus isolates associated with illnesses of varying severity (e.g., severe, systemic vs. gastrointestinal (GI) illness) were clonal or formed clonal complexes.
A retrospective analysis of 55 clinical B. cereus 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.
STs of clinical B. cereus 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 B. anthracis and emetic B. cereus isolates.
蜡样芽孢杆菌最常与食源性疾病（腹泻型和呕吐型）相关，但也是一种机会致病菌，可引起严重和致命感染。最近已开发出几种多位点序列分型（MLST）方案用于蜡样芽孢杆菌的基因分型，分析表明蜡样芽孢杆菌及其近亲炭疽芽孢杆菌和苏云金芽孢杆菌具有克隆或弱克隆群体结构。在本研究中，我们使用MLST来确定与不同严重程度疾病（例如严重的全身性疾病与胃肠道（GI）疾病）相关的蜡样芽孢杆菌分离株是克隆性的还是形成了克隆复合体。
对1954年至2004年间提交给疾病控制与预防中心的55株临床蜡样芽孢杆菌分离株进行了回顾性分析。选择来自严重感染（n = 27）、胃肠道（GI）疾病（n = 18）的临床分离株以及来自食品的相关分离株（n = 10），使用MLST进行分析。这55株分离株具有多样性，包含两个不同进化枝中的38种序列类型（ST）。在与严重疾病相关的27株分离株中，13株聚集在进化枝1中，而14株在进化枝2中。与GI疾病相关的分离株也在整个进化枝1和2中被发现，而本研究中没有分离株属于进化枝3。本研究中属于进化枝1/蜡样芽孢杆菌III谱系的所有分离株都与严重疾病相关，而属于进化枝1/蜡样芽孢杆菌II的分离株主要包含与严重疾病和呕吐型疾病相关的分离株。对于在流行病学上不同的分离株，仅观察到三种ST出现不止一次。
临床蜡样芽孢杆菌分离株的ST在系统发育上具有多样性，并分布在先前描述的三个进化枝中的两个中。需要分析更多数量的菌株，以确认是否特定谱系或克隆复合体更有可能包含临床分离株或与特定疾病相关，类似于炭疽芽孢杆菌和呕吐型蜡样芽孢杆菌分离株。
