Horse with colic

Additional Test Results

Results of appropriate studies are obtained and are shown:

Transrectal ultrasound image of mass:

Aspiration of perirectal mass: Thick, white-yellow purulent material is aspirated.

Cytology of perirectal mass fluid: The fluid contains large numbers of degenerate neutrophils and bacteria, indicating a septic inflammatory process consistent with a perirectal abscess. No lymphoid tissue is seen. Based on the cytology, the fluid is also submitted for bacterial culture.

Culture and sensitivity testing: A pure culture of Streptococcus zooepidemicus is obtained. The bacteria is susceptible to ampicillin, cefazolin, ceftiofur, chloramphenicol, erythromycin, penicillin, and rifampin. The bacteria is not susceptible to amikacin or trimethoprim/sulfonamide. There is intermediate susceptibility to gentamicin, enrofloxacin, and tetracycline.