Specific Strains of Escherichia coli Are Pathogenic for the Endometrium of Cattle and Cause Pelvic Inflammatory Disease in Cattle and Mice

Abstract

Background Escherichia coli are widespread in the environment and pathogenic strains cause diseases of mucosal surfaces including the female genital tract. Pelvic inflammatory disease (PID; metritis) or endometritis affects ∼40% of cattle after parturition. We tested the expectation that multiple genetically diverse E. coli from the environment opportunistically contaminate the uterine lumen after parturition to establish PID.Methodology/Principal FindingsDistinct clonal groups of E. coli were identified by Random Amplification of Polymorphic DNA (RAPD) and Multilocus sequence typing (MLST) from animals with uterine disease and these differed from known diarrhoeic or extra-intestinal pathogenic E. coli. The endometrial pathogenic E. coli (EnPEC) were more adherent and invasive for endometrial epithelial and stromal cells, compared with E. coli isolated from the uterus of clinically unaffected animals. The endometrial epithelial and stromal cells produced more prostaglandin E2 and interleukin-8 in response to lipopolysaccharide (LPS) purified from EnPEC compared with non-pathogenic E. coli. The EnPEC or their LPS also caused PID when infused into the uterus of mice with accumulation of neutrophils and macrophages in the endometrium. Infusion of EnPEC was only associated with bacterial invasion of the endometrium and myometrium. Despite their ability to invade cultured cells, elicit host cell responses and establish PID, EnPEC lacked sixteen genes commonly associated with adhesion and invasion by enteric or extraintestinal pathogenic E. coli, though the ferric yersiniabactin uptake gene (fyuA) was present in PID-associated EnPEC. Endometrial epithelial or stromal cells from wild type but not Toll-like receptor 4 (TLR4) null mice secreted prostaglandin E2 and chemokine (C-X-C motif) ligand 1 (CXCL1) in response to LPS from EnPEC, highlighting the key role of LPS in PID.Conclusions/SignificanceThe implication arising from the discovery of EnPEC is that development of treatments or vaccines for PID should focus specifically on EnPEC and not other strains of E. coli.

Innate immunity and inflammation of the bovine female reproductive tract in health and disease

“…The impact of pathogens on the host is enhanced by a multitude of virulence factors including pore-forming toxins, bacterial secretion systems and bacterial proteases (Blander & Sander 2012). In addition, unlike commensal organisms, pathogens not only colonise tissues but also invade the cells of the female reproductive tract, often causing cell death (Donofrio et al 2007, Sheldon et al 2010. Therefore, the scale of the inflammatory response to microbes is dependent on multiple factors including microbial virulence effectors, host tissue factors, and on the regulation of intracellular signalling pathways associated with innate immunity.…”

“…For example, endometrial pathogenic E. coli (EnPEC) adhere to and invade primary endometrial epithelial and stromal cells, cause inflammation, and recreate disease when infused into the uterus of mice (Sheldon et al 2010). In particular, LPS appears to be the major virulence factor of EnPEC, stimulating TLR4-dependent inflammatory responses by endometrial cells (Sheldon et al 2010, Cronin et al 2012. On the other hand, the presence of T. pyogenes is associated with pus in the uterus, the severity of clinical signs and the extent of the subsequent subfertility (Bonnett et al 1991, Westermann et al 2010.…”

“…However, animal models of clinical uterine disease are also important because they are needed for the development of new vaccines or treatments, as well as uncovering the mechanisms of immunity in the female reproductive tract. Animal models of uterine disease have been generated in dairy and beef cattle, sheep and mice (Ayliffe & Noakes 1982, Karsch et al 2002, Sheldon et al 2010, Amos et al 2014. Most of the animal models that replicate uterine disease rely on infusion of E. coli or T. pyogenes into the uterine lumen (Rowson et al 1953, Ayliffe & Noakes 1982, Sheldon et al 2010, Amos et al 2014.…”

“…Animal models of uterine disease have been generated in dairy and beef cattle, sheep and mice (Ayliffe & Noakes 1982, Karsch et al 2002, Sheldon et al 2010, Amos et al 2014. Most of the animal models that replicate uterine disease rely on infusion of E. coli or T. pyogenes into the uterine lumen (Rowson et al 1953, Ayliffe & Noakes 1982, Sheldon et al 2010, Amos et al 2014. A key step in generating models of uterine disease in cattle is mechanical debridement of the epithelium lining the endometrium (Ayliffe & Noakes 1982, Amos et al 2014.…”

Agreement between postmortem endometrial cytology, biopsy and bacteriology in culled dairy cows

“…Whereas from cytology negative horns some recognized pathogens were isolated, such as E. coli and T. pyogenes (Sheldon et al, 2002(Sheldon et al, , 2010Amos et al, 2014) or S. uberis, the major causative agent for bovine mastitis (Schunkken et al, 2013), from cytology positive horns nonspecific or low pathogenic bacteria were found. These findings agree with previous studies showing that large microbial diversity can be identified in the uterus of dairy cows, irrespective of their uterine health status (Santos et al, 2011).…”