Quantitation of H. pylori cytotoxin mRNA by real-time RT-PCR shows a wide expression range that does not correlate with promoter sequences.

Up to 28-fold differences in vacA expression in Helicobacter pylori strains grown in vitro were demonstrated by real time quantitative RT-PCR. These large differences in expression were unrelated to putative -35 and -10 motifs or to other untranslated sequences upstream of the ATG start site. The lack of correlation between promoter sequences and the vacA expression levels suggest the potential existence of a bacterial strain-specific factor, as earlier proposed by others on the basis of reporter gene fusions.