Prevention and treatment of cilia-associated respiratory bacillus in mice by use of antibiotics.

The effects of continuous oral administration of antibiotics in mice were investigated. Sulfamerazine, ampicillin, and chlortetracycline were tested at a rate of 500 mg/L of drinking water. Mice were infected by intranasal inoculation with 10(6) bacilli of the SMR strain of cilia-associated respiratory (CAR) bacillus. The mice were treated with the antibiotics starting 1 week before, 1 week after, or 4 weeks after the inoculation, for 5, 3, or 4 weeks respectively, then were examined. The infected mice lost body weight, and this loss was prevented or regained by all of the antibiotic treatments. Serologically no antibodies were detectable in the mice administered sulfamerazine starting 1 week before the inoculation. Mice administered sulfamerazine starting 1 week after the inoculation and ampicillin or chlortetracycline starting 1 week before or after the inoculation yielded a low titer of antibodies compared with nontreated infected mice. Mice administered antibiotics starting 4 weeks after the inoculation yielded the same titer of antibodies as nontreated infected mice. No pathologic respiratory tract lesions were observed in mice administered sulfamerazine starting 1 week before the inoculation. Mice administered sulfamerazine starting 1 week after the inoculation or ampicillin starting 1 week before or after the inoculation had slight peribronchitis without CAR bacillus colonization. Mice administered chlortetracycline, starting either 1 week before or after inoculation, developed peribronchitis, with colonization of the bacillus on the airway mucosa. In mice medicated starting 4 weeks after the inoculation, respiratory tract lesions developed, but their severity was reduced. The airway mucosa in mice treated with chlortetracycline was associated with the CAR bacillus but not in mice treated with sulfamerazine and ampicillin. These findings suggest that prevention and eradication of CAR bacillus infection is possible by treatment with sulfamerazine.