Characterization of genotoxin-encoding Escherichia coli isolated from specific-pathogen free cats with impaired fertility

Abstract

Escherichia coli strains encoding colibactin (pks), hemolysin-associated cytotoxic necrotizing factor (cnf), and cytolethal distending toxin (cdt) are associated with intestinal inflammation and cancer, urinary tract infection, and septicemia in susceptible hosts. Over a 2-year period, an inbred laboratory colony of specific-pathogen free (SPF) cats (∼25) presented with resorptions, stillbirths, and pyometras in >50 % of pregnancies. Hemolytic E. coli were cultured from vaginal and preputial swabs of clinically normal, intact males, healthy kittens, and placenta and fetal tissues of a dam with reproductive disorders. We hypothesized cats from this colony were colonized with cytotoxin-encoding E. coli. 27 E. coli isolates were cultured from 20 fresh feces representing the majority of cats with and without fertility failures. Two E. coli isolates were also cultured from vaginal swabs from the same cat. 22 isolates (75.9 %) demonstrated hemolysis on blood agar. Twelve isolates (41.4 %) were pks+, 14 (48.3 %) were cnf+, and 10 (34.5 %) were cdt+ by PCR. Serotypes and virulence factor profiles were consistent with the extraintestinal E. coli (ExPEC) pathotype. Antibiotic resistance to cephalothin was exhibited in 13/14 representative isolates. Whole genome sequence analysis of 3 representative isolates confirmed the hemolysin-associated cnf, cdt, and the pks gene island. Representative isolates were cytotoxic to cervical epithelial cells in vitro. This study indicated ExPEC were present in SPF cats with a history of reproductive failure. While causality cannot be established, it is probable ExPEC was associated with impaired reproductive health and breeding success. Since treatment of the colony with cefovecin, reproductive performance has appreciably improved.