Urinary tract infections attributed to diverse ExPEC strains in food animals: evidence and data gaps.

Randall S Singer

doi:10.3389/fmicb.2015.00028

Abstract

Between 70 and 95% of urinary tract infections (UTI) are caused by strains of Escherichia coli. These strains, often termed Extraintestinal Pathogenic E. coli (ExPEC), possess specific virulence traits allowing them to colonize more inhospitable environments, such as the urogenital tract. Some ExPEC isolates from humans have similar virulence factor profiles to ExPEC isolates from animals, and because of the potential for these strains to cause UTI in people, these infections have been referred to as foodborne UTI, or FUTI. Finding similarities in ExPEC in animals and humans is not necessarily proof of transmission, particularly a unidirectional pathway from animals to humans; similarities in virulence factor profiles should be expected given the specific bacterial requirements for colonizing physiological compartments with similar characteristics in all animals. Many of the most important strains of human ExPEC globally, such as ST131, are highly virulent and clonal implying routes of transmission other than food. Documenting routes of transmission is particularly difficult due to the wide range of potential ExPEC sources, including the human intestinal tract, and non-human reservoirs such as food animals and retail meat products, sewage and other environmental sources, and companion animals. The significant environmental reservoir of ExPEC, including strains such as ST131, could potentially explain much more completely the global dissemination of virulent ExPEC clones and the rapid dissemination of new strains within the community. Taken in its totality, the link between ExPEC in animals and UTI in humans might exist, but studies conducted to date do not enable an estimation of the relative importance of this route of transmission. To reduce the burden of illness associated with ExPEC, the scientific community needs to push forward with ecologically-based, scientifically-sound study designs that can address the plethora of ways in which E. coli can spread.

Highlights

Extraintestinal pathogenic Escherichia coli (ExPEC) is an incredibly diverse E. coli pathotype, and this genetic diversity is reflective of its occurrence in and colonization of diverse and highly specialized ecological niches
ExPEC can colonize the human intestine, and when given the opportunity in individuals who might be vulnerable in some way or the presence of specific risk factors such as increased sexual activity and use of spermicides (Foxman, 2014), the bacterium can be transferred to the urogenital tract where it can cause a urinary tract infection (UTI)
UTIs represent a serious burden of illness globally (Foxman, 2002, 2014), and 70–95% of these infections are caused by strains of E. coli (George and Manges, 2010; Hooton, 2012), often termed uropathogenic E. coli (UPEC), which is a subset of ExPEC

Summary

Introduction

Extraintestinal pathogenic Escherichia coli (ExPEC) is an incredibly diverse E. coli pathotype, and this genetic diversity is reflective of its occurrence in and colonization of diverse and highly specialized ecological niches. A continued reliance on phenotypic traits, such as VF and AR, and the use of study designs inappropriate for documenting frequency and direction of transmission, has resulted in the propagation of the ill-defined inference that animal ExPEC cause a substantial fraction of human ExPEC infections, including UTI.

Results

Conclusion