Association between the Presence of Intrauterine Escherichia Coli Virulence Genes and Subsequent Reproductive Tract Disease in Postpartum Dairy Cows

Abstract

An association between postpartum intrauterine Escherichia coli and subsequent reproductive tract diseases such as purulent vaginal discharge (PVD) and endometritis (ENDO) has been found inconsistently in previous research. This inconsistency may be due to differences in the pathogenicity and presence of certain virulence factors in the various strains. The objective of this study was to evaluate the association between the presence of intrauterine E. coli virulence factor (VF) genes after parturition and subsequent reproductive tract diseases in postpartum dairy cows. Intrauterine swabs were collected from cows 4 (± 3) DIM. The swabs were plated to identify E. coli, Trueperella pyogenes, Fusobacterium necrophorum , and Prevotella melaninogenica . A subgroup of the E. coli samples was submitted for colony hybridization for identification of 40 VF genes. Purulent vaginal discharge and ENDO were diagnosed at 35 (±7) DIM using the Metricheck device (purulent discharge or worse) and the cytobrush technique adapted for use in cattle (≥ 6% polymorphonuclear leukocytes), respectively. Cows diagnosed with PVD, ENDO, or both conditions were classified as positive for reproductive tract disease. Logistic regression models were built using the reproductive tract disease status as the outcome, and the bacteria and VF gene presence as the exposure. Of the 465 cows enrolled, 52% of the uterine samples were positive for E. coli , 34% were positive for T. pyogenes , 3% were positive for F. necrophorum , and 1% were positive for P. melaninogenica . A total of 152 E. coli samples were examined for VF gene identification. Reproductive tract disease was diagnosed in 237 cows (51%). The presence of intrauterine E. coli and T. pyogenes was associated with greater odds of reproductive tract disease. Cows with E. coli positive for VF genes fepC, maIX, hlyE, sitA, irp1, irp2, fyuA, or iss had greater odds of having subsequent reproductive tract disease compared to cows without E. coli . These VF genes code for iron acquisition, the maltose and glucose PTS system, hemolysin E toxin, and increased serum survival. Three of the siderophore genes (irp1, irp2, and fyuA) are part of the core of a high-pathogenicity islands, previously described in extraintestinal pathogenic E. coli (ExPEC) The results of this study suggest that certain VFs are likely to contribute to the pathogenicity of E. coli strains as they are associated with subsequent reproductive tract disease.