bioRxiv preprint doi: https://doi.org/10.1101/2021.05.16.444350; this version posted May 17, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 1 OmpF Downregulation Mediated by Sigma E or OmpR Activation Confers 2 Cefalexin Resistance in Escherichia coli in the Absence of Acquired β- 3 Lactamases. 4 5 Maryam ALZAYN1,2, Punyawee DULYAYANGKUL1, Naphat SATAPOOMIN1, 6 Kate J. HEESOM3, Matthew B. AVISON1* 7 8 1School of Cellular & Molecular Medicine, University of Bristol, Bristol, UK 9 2Biology Department, Faculty of Science, Princess Nourah Bint Abdulrahman 10 University, Riyadh, Saudi Arabia 11 3University of Bristol Proteomics Facility, Bristol, UK 12 13 * Correspondence to: School of Cellular & Molecular Medicine, University of 14 Bristol, Bristol, United Kingdom.
[email protected] 15 16 17 Running Title: OmpR and Sigma E mediated Cefalexin Resistance in E. coli 18 1 bioRxiv preprint doi: https://doi.org/10.1101/2021.05.16.444350; this version posted May 17, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 19 Abstract 20 Cefalexin is a widely used 1st generation cephalosporin, and resistance in 21 Escherichia coli is caused by Extended-Spectrum (e.g. CTX-M) and AmpC β- 22 lactamase production and therefore frequently coincides with 3rd generation 23 cephalosporin resistance.