Detection of Pasteurella pneumotropica in C57BL/6-Tg (CAG-flpe)36 mice

Experimental Animal Division of RIKEN BioResource Center (BRC), urgently asks your attention to RBRC01834 C57BL/6-Tg (CAG-flpe)36 mice we shipped. We recently detected Pasteurella pneumotropica in these mice maintained in our barrier facility by the supplemental microbial tests.

P. pneumotropica is a gram-negative coccobacillus and categorized as an opportunistic pathogen (*) with very week pathogenicity in immuno-competent normal mice. However, there have been a few reports that experimental infection of P. pneumotropica to immune-deficient mice caused pathological changes in the lung and even death.

If you would like to continue to use the C57BL/6-Tg (CAG-flpe)36 mice we shipped and the crossbred offspring, please inquire of your facility manager or veterinarian about keeping the strain, and consider the antibiotic administration to eliminate P. pneumotropica (Exp. Anim. 2002, 51(4): 401-405).

When the C57BL/6-Tg (CAG-flpe)36 strain was rederived by embryo transfer of imported mice in 2006, P. pneumotropica was not detected by the test using foster mothers. Since then, P. pneumotropica has not been detected by bimonthly test using sentinel mice. However, recently we conducted P. pneumotropica culture test by using direct swab samples from eyes, oral cavity and genital regions and detected P. pneumotropica only in this strain and the crossbred offspring. We have already eliminated positive mice from the barrier facility. We have started to clean-up the strain again by embryo transfer. If you would like to have the cleaned-up mice, please let us know. We will provide the mice as soon as they become available.

Through this lesson, we have decided to improve the microbial tests by expanding the direct swab test from each live strain as a preventive measure so that P. pneumotropica will never escape from our test again. We appreciate your continued understanding and support for RIKEN BRC.

If you have any question and concern on this matter, please feel free to contact us (

*Opportunistic pathogen: an organism that is capable of causing disease only when the host’s resistance is lowered.

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