量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Pasteurella pneumotropica, a Gram-negative opportunistic pathogen, is frequently isolated from the respiratory organs and digestive tracts of clinically normal conventional mice. Oral or subcutaneous treatment with enrofloxacin, an antibiotic, at a daily dose of 25.5 mg/kg for 2 weeks is effective in eliminating P. pneumotropica. However, the drawbacks of this treatment include substituted microbism and inhibited growth of indigenous fungi in the mouth. We therefore examined whether reducing the enrofloxacin treatment duration and dosage could eliminate P. pneumotropica from mice and eliminate these drawbacks.
Healthy C3H/HeMsNrs (TLR4-competent) and C.B-17/Icr- Prkdcscid/JclNrs mice were intranasally inoculated with 1 X 107 P. pneumotropica. Twenty-two days after inoculation, the mice were subcutaneous injected with enrofloxacin once a day for 3 days at doses ranging from 3 to 300 mg/kg. Day 22 was chosen for treatment initiation because in a preliminary examination P. pneumotropica was detected in nasal samples by PCR assay 21 days after inoculation. Seven days after the completion of treatment, all mice were sacrificed and oral, nasal, and tracheal swabs were collected. Each swab sample was plated directly onto blood agar and incubated. To identify P. pneumotropica among the isolates, PCR assay was used to identify the 16S rRNA gene. The lungs and skin were examined histopathologically. Pasteurella pneumotropica was not detected, even in the minimum-dose group (3 mg/kg), in C3H/HeMsNrs mice. In the 100- and 300-mg/kg dose groups, induration or inflammation was observed in the skin at the injection site. In C.B-17/Icr- Prkdcscid/JclNrs mice, P. pneumotropica was detected at enrofloxacin doses of 3 and 10 mg/kg, and these mice developed pneumonia. Because of skin inflammation, higher doses were not tested.
Subcutaneous administration of enrofloxacin at a dose of 3 mg/kg for 3 days can successfully eradicate latent infection of P. pneumotropica in immunocompetent mice. Further investigation is needed to clarify the lack of efficacy of the same treatment in immunodeficient mice.
2010 AALAS National Meeting
