#15 NSG mouse strain, health monitoring and microbiological findings
AbstractThe NSG strain is one of the most immunodeficient mice available, and provides an effective model for studies where the engraftment of human cells is required.However because of their severe adaptive and innate immune deficiency, these mice must be kept under high environmental control standards.
Routine health monitoring, according to FELASA guidelines, included antigen testing in NSG animals and antibody testing in sentinel animals (negative results, not shown).
We found saprophytic flora, by use of classic microbiology techniques, in a variety of tissues and organs. Many of the sampled animals were found to have bacteria growing in the spinal cord, tarsal joint, heart, spleen, liver, kidney or blood. In order to rule out possible tissue contamination, we sent samples to three different external laboratories. All the samples submitted came back with the same results.
We postulate that the widespread presence of these saprophytic bacteria may be due to a lack of IgA secretion at the mucosal epithelium, and the bacterial growth in these tissues and organs to the immunodeficiency including impaired macrophage activity. The potential clinical significance of these bacteria in NSG mice, if any, is not known. To explore the possible connection between the bacterial infection and animals with signs of slight limb paresthesia (numbness) and paralysis, and arthritis, seen in 0.5-1% of animals, further studies are needed.