Virulence potential of a multidrug-resistant Escherichia coli strain belonging to the emerging clonal group ST101-B1 isolated from bloodstream infection

Abstract

28Escherichia coli EC121 is a multidrug-resistant (MDR) strain isolated from bloodstream 29 infection of an inpatient with persistent gastroenteritis and Zone T lymphoma that died 30 due to septic shock. Despite causing an extraintestinal infection, strain EC121 harbors 31 very few known virulence factors associated with extraintestinal pathogenic E. coli 32 (ExPEC). Furthermore, this strain was assigned to phylogenetic group B1, which is 33 usually related to commensals or diarrheagenic E. coli (DEC) strains, being rarely linked 34 to extraintestinal infections. The question rises if E. coli EC121 is opportunistic or does 35 have a true virulence potential. To address this question the genome of strain EC121 was 36 sequenced, and an in vitro characterization of some pathogenic-associated properties was 37 performed. The data retrieved from genome analyses showed that E. coli strain EC121 38 belongs to the O154:H25 serotype, and to the sequence type 101-B1 (ST101-B1), which 39 has been epidemiologically linked to extraintestinal infections and antimicrobial 40 resistance spread as well. Moreover, it is shown to be closely related to Shiga-toxin 41 producing E. coli (STEC). Besides, strain EC121 is an MDR strain harboring 14 42 antimicrobial resistance genes, including bla CTX-M-2 , and more than 50 complete virulence 43 genetic clusters, which are reported to be associated either with DEC or ExPEC, or both. 44Strain EC121 also displays the capacity to adhere to and invade HeLa cells, intestinal 45 Caco-2 cells and bladder T24 cells, as well as the ability to form biofilms on abiotic 46 surfaces, and survive the bactericidal serum complement activity. Altogether, the genetic 47 and phenotypic traits presented by E. coli EC121 may be unveiling a pathogen powered 48 by its multi-drug resistance characteristic. The recognition of such MDR pathogens 49 makes it essential to carry out studies providing accurate information about their virulence 50 potential. Such studies will help in the development of alternative therapies of infection 51 management and spread control of MDR strains. [Research article] [Santos el al., 2019] 3 52 53 Author summary 57 Extraintestinal pathogenic Escherichia coli are mostly associated with phylogenetic 58 group B2 and the majority of the studies regarding extraintestinal infection focus on the 59 most virulent strains, which might also possess multidrug-resistant phenotype, like the 60 ST131 strains. On the other hand, strains that belong to phylogroup B1 and are isolated 61 from extraintestinal infections are almost neglected, being considered as merely 62opportunist pathogens, and the majority of studies reporting strains from this phylogroup 63 focus on antimicrobial resistance. We concentrated our research on one multidrug-64 resistant strain isolated from bloodstream infection that belongs to phylogenetic group B1 65 to enlarge the knowledge about the virulence of this kind of strain. We demonstrated that 66 strain EC121 has full potential to be considered a pathogenic strain, bec...