Detection and Remediation of Pneumocystis murina Infections by Environmental Health Monitoring
The increased sensitivity of PCR testing for environmental health monitoring compared with soiled bedding sentinel (SBS) serology can identify rodent pathogens thought to be excluded from a research animal facility. Exhaust dust testing for rodent pathogen surveillance revealed the presence of Pneumocystis murina in 3 colonies that was undetected in previous years of SBS serologic testing. This case series describes the process of follow-up testing used to identify and eliminate or isolate animals infected with P. murina. PCR testing of exhaust dust at the rack, row, and cage level on individually ventilated cage (IVC) racks was leveraged to identify all infected cages. Based on our experience, IVCs and standard cage handling practices are sufficient to contain this organism in mice with altered immune systems, which can harbor chronic P. murina infections. Institutions with an active mouse import program are at ongoing risk of accepting P. murina–positive animals from institutions still relying on SBS serology to identify this pathogen. PCR testing of rodent cage–generated dust can be used to pinpoint P. murina–infected mice housed on IVC racks.
Room-level diagrams of racks that tested positive for P. murina during EDT health surveillance testing with PCR relative copy numbers indicated as a color heat map. (A) Case 1 includes 8 single-sided IVC racks (along left and right walls) and 6 double-sided racks (center). Initially, 3 of the double-sided racks tested positive, but rack 5/10 tested negative during repeat testing. (B) Case 2 includes 6 single-sided racks and 2 double-sided racks. Relatively low copy numbers were confirmed by subsequent row- and cage-level testing. (C) Case 3 includes 7 single-sided racks. On initial and follow-up testing, racks 5 to 8 had low copy numbers that were determined to be false-positives and likely due to high environmental DNA burden in the room from infected strains on racks 1 to 3. ATS, animal transfer station.
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