Sulfamethoxazole – Trimethoprim Represses csgD but Maintains Virulence Genes at 30°C in a Clinical Escherichia coli O157:H7 Isolate

Abstract

We thank Ly-Huong Nguyen for assistance with DNA Sanger sequencing and Dr. Chin-Yi Chen for helpful consultations. USDA is an equal opportunity provider and employer. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.

Pch Genes Control Biofilm and Cell Adhesion in a Clinical Serotype O157:H7 Isolate

“…In order to compare pchE expression in PA20 grown on agar surfaces at 30°C and 37°C, with and without exposure to 27× SMX-TM, total RNA was isolated and cDNA was made as previously reported [29]. Samples were tested in triplicate.…”

“…For biofilms, the mean optical density values of eluted CV at 590 nm (OD590) for each sample were analyzed as follows. For large screening assays testing the effects of multiple HTR regulators, samples were analyzed in R [37] as previously described [29]. Strain variance was assessed with the Bartlett's test and OD value differences were determined using the nonparametric Kruskal-Wallis test.…”

“…SMX-TM can also induce prophage excision from mlrA, making restoration of CsgD function a possible additional consequence of antibiotic treatment in the host [20,30]. However, in an RNA-seq study testing SMX-TM effects on a clinical O157:H7 transcriptome, SMX-TM had a slight repressive, rather than enhancing, effect on csgD functions in spite of strong induction of prophage and prophage-like genes [29]. The mechanism controlling the unexpected repressive csgD effects following SMX-TM exposure were not apparent but we reasoned that transcription factors differentially expressed during SMX-TM exposure might antagonize csgD.…”

“…Exposure of clinical O157:H7 strains to DNA-damaging antibiotics, such as sulfamethoxazole-trimethoprim (SMX-TM), can potentiate HUS by increasing the expression of virulence genes encoded in prophage and prophage-like elements (e. g. stx 2 www.videleaf.com and LEE) [27][28][29]. SMX-TM can also induce prophage excision from mlrA, making restoration of CsgD function a possible additional consequence of antibiotic treatment in the host [20,30].…”

“…In this study we tested several transcription factors encoded in HTR that were induced during SMX-TM treatment of O157:H7 clinical isolate PA20 [29] for an effect on csgD, csgD-dependent cell adhesion, and biofilm properties.…”