Therapy

There is staggering evidence to support the role of infectious agents in the pathogenesis of HUC in dogs. No immunosuppressive therapy should be instituted if this condition is suspected and efforts should be made to confirm AIEC, either with special stains or FISH techniques, which is considered the most sensitive of tests.

Empirical treatment with antimicrobials and immunosuppressive therapy has resulted in poor outcomes on dogs with GC (Hostutler etal. 2004). In contrast, dogs have a reported dramatic improvement of the colonic histo­logic pattern and a significant weight gain after treatment with enrofloxacin (Hostutler et al. 2004; Davies et al. 2004; Mansfield et al. 2009). Enrofloxacin, is currently the recom­mended treatment in dogs with GC at a dose of 5-10mg∕kg, orally, daily for 6-10 weeks. Enrofloxacin is a bactericidal antibiotic with a highly effective broad gram-negative spec­trum, it is also specific effect against Mycobacterium, Mycoplasma, Chlamydia, and rickettsia, but another important char­acteristic that plays a role in its success of treating HUC is its ability to penetrate macrophages. Chloramphenicol has also been described as an effective antimicrobial agent in dogs with GC (Van Kruiningen et al. 1965).

Antimicrobial resistance is described as a fairly common occurrence in dogs treated for GC (Craven et al. 2010). Persistent intra-mucosal E. coli can be demonstrated in mucosa using FISH technique in dogs that become antimicrobial unresponsive (Mansfield et al. 2009). Various E. coli strains were isolated and cultured from dogs with GC (n = 14), which translates to approximately two to three strains per dog, which were incidentally similar to the E. coli strains found in healthy dogs (n = 17). It appears that the antimicrobial-resistant individuals are the same dogs carrying antimicrobial-resistant strains. However, almost half of the E. coli strains from dogs with GC were resistant to not only enro- floxacin (6/14) but also chloramphenicol, trimethroprim sulfas, and rifampicin (4/14), and these dogs had a poor outcome (Craven et al. 2010). It remains to be seen if perhaps multidrug combinations that include tetracyclines, trimethropim, and ciprofloxacin may have a synergistic effect in overcoming resistance of E. coli strains as is seen in the case of Crohn's disease (Craven et al. 2010).