Association between Granulomatous Colitis in French Bulldogs and Invasive Escherichia coli and Response to Fluoroquinolone Antimicrobials

Background French Bulldogs develop a form of granulomatous colitis (GC) with histopathological resemblance to GC of Boxer dogs (GCB). GCB is associated with mucosally invasive Escherichia coli whose eradication correlates with clinical remission. Hypothesis/Objectives To characterize the clinical and histopathological features, presence or absence of invasive colonic bacteria, and response to fluoroquinolones in French Bulldogs with GC. Animals A total of 6 French Bulldogs with a histological diagnosis of GC. Methods Retrospective study of medical records. Bacterial colonization was evaluated using 16S rRNA probes for eubacteria and E.coli. Biopsy specimens from 3 dogs were cultured for bacteria. Clinical response to fluoroquinolone antimicrobials was determined. Results All dogs were =1year of age with hematochezia that was refractory to empirical therapy. Clinicopathologic and fecal analysis did not reveal abnormalities. Abdominal ultrasound revealed patchy thickening of the colon in 4/5 dogs and regional lymphadenopathy in 5/5. Colonoscopic abnormalities included irregularly thickened and ulcerated mucosa, hyperemia, and overt bleeding in 4/6 cases. Multifocal accumulations of PAS-positive macrophages and intramucosal E.coli were present in colonic biopsies of all 6 dogs. Administration of enrofloxacin (5/6) or marbofloxacin (1/6) at 4.410mg/kg (median 10mg/kg) PO q24h for 610weeks was associated with clinical improvement within 514days. All dogs remained in remission over a 330month follow-up period. Conclusions Granulomatous colitis in young French Bulldogs is associated with the presence of invasive E.coli and closely parallels GCB. Treatment with fluoroquinolone antimicrobials can induce lasting clinical remission.