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.
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