Enrofloxacin, a fluoroquinolone bactericidal antibiotic, was administered in an attempt to eradicate Pasteurella pneumotropica (P. pneumotropica) from a contaminated mouse colony. Contaminated mice, maintained within 4 animal rooms, were administered Enrofloxacin in drinking water at a daily dosage of 25.5 mg/kg for 2 weeks. Following one week of Enrofloxacin treatment, mice were selected randomly from each room and examined for P. pneumotropica. This procedure was repeated two or three times until all mice examined tested negative for the Pasteurella strain. With the exception of one room, treated mice consistently tested negative for P. pneumotropica for up to 45 weeks following completion of Enrofloxacin treatment. Thus, oral administration of Enrofloxacin significantly eliminated P. pneumotropica from a contaminated mouse colony.