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Genomic and phenotypic characterization of Escherichia coli isolates recovered from the uterus of puerperal dairy cows

E. Silva^*, S. Leitão^*, T. Tenreiro, C. Pomba^*, T. Nunes^*, L. Lopes da Costa^* and L. Mateus^*,1

^* Interdisciplinary Centre of Research in Animal Health, Faculty of Veterinary Medicine, TULisbon, Av. da Universidade Técnica, Alto da Ajuda, Polo Universitário, 1300-477 Lisbon, Portugal
Faculty of Sciences, University of Lisbon, Edifício ICAT, Campus da FCUL, Campo Grande 1749-016, Portugal

¹ Corresponding author: lmateus{at}fmv.utl.pt

The role of Escherichia coli in the pathogenesis of the puerperal uterine infection of the cow is largely unknown. It is proposed that E. coli favors the persistence of Arcanobacterium pyogenes and gram-negative bacteria that are pivotal to the establishment of the infection. Here, we report the genomic and phenotypic characteristics of 72 E. coli isolates recovered from the uterus of dairy cows with normal puerperium (n = 12; 35 isolates) or clinical metritis (n = 18; 37 isolates), in an attempt to identify characteristics that are related to the establishment of uterine infection. We evaluated DNA fingerprints generated by repetitive element sequence-based PCR, phylogenetic grouping, the presence of 15 virulence factor genes, in vitro biofilm formation and its relationship to curli fimbriae expression, and cellulose production. We found a wide genetic diversity (40 clonal types), including types common to normal puerperium and clinical metritis cows (n = 6), as well as types specific to normal puerperium (n = 14) or clinical metritis (n = 20) cows. Isolates were assigned to phylogenetic groups B1 (58%), A (31%), and D (11%). Only 4 virulence factor genes were detected (hlyE, hlyA, iuc, and eaeA). In vitro biofilm formation was significantly affected by culture medium and incubation temperature. Curli fimbriae expression and cellulose production, although related to biofilm formation, were not required for it. None of the evaluated E. coli characteristics were significantly related to the establishment of the uterine infection. In conclusion, data presented in this paper indicate that E. coli isolates recovered from the uterus of puerperal cows present a wide genetic diversity, do not belong to a known pathogenic group, and have a low potential of virulence and persistence. This corroborates the putative role of the bacterium in the pathogenesis of the puerperal uterine infection of the cow.

Key Words: Escherichia coli • virulence factor gene • biofilm • puerperal cow