Purpose: The aim of this study was to determine the influence of LMWC on growth and expression of the Shiga Toxin genes, stx1 and stx2, by Escherichia coli O157:H7.
Methods: STEC O157:H7 strains were grown in tryptic soy broth (TSB) or Luria Bertani broth (LB) containing 0.1% DMSO (control) and 50 µm LMWC at 37°C. Bacterial growth was monitored by measuring optical density (OD600 nm) and viable cell count over 10 h. qPCR was performed on cDNA generated at mid-logarithmic (MLP) (3.5 h), late logarithmic (LLP) (6.5 h) and stationary (SP) (20 h) growth phases to monitor gene expression. Primers were designed for gapA (reference), arcA (housekeeping), stx1, and stx2 genes.
Results: No significant difference in viability was detected when the bacteria were treated with LMWC CCG-203592. In TSB, the expression of stx1 and stx2 in strain c7927 decreased by 51 ± 7.5% (P ≤ 0.007) and 39 ± 9.8% (P ≤ 0.02) at the LLP, respectively. The expression of stx2 by strain 3178-95 decreased by 26 ± 40.6% (P ≤ 0.38) at the MLP, by 30 ± 19.4% (P ≤ 0.11) at the LLP and by 40 ± 18.6% (P ≤ 0.19) at the SP. In LB broth, stx1 and stx2 expression by strain 3178-95 decreased by 34.5 ± 3.5% (P ≤ 0.05) and 85.7 ± 1.4% (P ≤ 0.008) at the LLP, respectively, while stx2 expression decreased by 87.1 ± 1.4% (P ≤ 0.008) at the SP.
Significance: The use of LMWC could be an alternative way to inhibit virulence gene expression in STEC without causing cell death, indicating a promising starting point for development of novel antimicrobial agents against STEC.