Mathis J N, Pilkinton L, McMillin D E
Department of Biology, State University of West Georgia, Carrollton, GA 30118, USA.
Curr Microbiol. 1999 Jun;38(6):324-8. doi: 10.1007/pl00006811.
Genomic DNA from three Clostridium difficile strains was analyzed by PCR for DNA sequences encoding toxin A (tcdA) and toxin B (tcdB). Toxigenic control strain VPI 10463 possessed tcdA, tcdB, and an open reading frame (tcdE) between these two genes, whereas nontoxigenic control strain 85 lacked each of these genetic determinants. However, strain M90, also a nontoxigenic strain, was found to possess tcdA, tcdB, and tcdE. Normally the presence of toxin genes is associated with toxigenicity. Analysis of tcdA and tcdB mRNA revealed toxin gene transcription in strains VPI 10463, 23 (a mildly toxigenic strain), and M90, but not in strain 85. However, for strain M90, tcdA and tcdB mRNA was at the lower limit of detection, whereas mRNAs encoding tcdA and tcdB were easily detected in strains VPI 10463 and 23. Low levels of toxin gene transcription is the probable cause of M90's lack of toxigenicity.
采用聚合酶链反应（PCR）对三株艰难梭菌菌株的基因组DNA进行分析，以检测编码毒素A（tcdA）和毒素B（tcdB）的DNA序列。产毒素对照菌株VPI 10463拥有tcdA、tcdB以及这两个基因之间的一个开放阅读框（tcdE），而无毒对照菌株85则缺乏这些遗传决定因素中的任何一个。然而，同样为无毒菌株的M90菌株却被发现拥有tcdA、tcdB和tcdE。通常情况下，毒素基因的存在与产毒性相关。对tcdA和tcdB mRNA的分析显示，在菌株VPI 10463、23（一种轻度产毒菌株）和M90中存在毒素基因转录，但在菌株85中则没有。然而，对于菌株M90，tcdA和tcdB mRNA处于检测下限，而在菌株VPI 10463和23中则很容易检测到编码tcdA和tcdB的mRNA。毒素基因转录水平低可能是M90缺乏产毒性的原因。
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