Characterization of Host-Pathogen-Device Interactions in Pseudomonas aeruginosa Infection of Breast Implants

Background: Pseudomonas aeruginosa accounts for 7 to 22 percent of breast implant-associated infections, which can result in reconstructive failures and explantation. Investigating host-pathogen-device interactions in mice and patient samples will improve the understanding of colonization mechanisms, for targeted treatments and clinical guidelines. Methods: Mice with and without implants were infected with PAO1 laboratory strain or BIP2 or BIP16 clinical strains and killed at 1 day or 7 days after infection to evaluate for colonization of implants and underlying tissues by means of colony-forming unit enumeration. Immunostaining was performed on mouse implants, human tissue expanders colonized by BIP2, and acellular dermal matrix colonized by BIP16. Results: Colonization of tissues and smooth implants by P. aeruginosa was strain-dependent: at 1 day after infection, all strains acutely infected tissues with and without implants with colonization levels reflecting growth rates of individual strains. At 7 days after infection, PAO1 caused colonization of approximately 10(5) colony-forming units/100 mg of tissue but required implant presence, whereas in mice infected with BIP2/BIP16, colony-forming units were below the limit of detection with or without implants. Immunofluorescence staining of mouse implants, however, demonstrated continued presence of BIP2 and BIP16. Staining showed co-localization of all strains with fibrinogen, collagen I, and collagen III on mouse and human samples. Conclusions: The trajectory of P. aeruginosa in breast implant-associated infections was strain-dependent, and strains could exhibit acute symptomatic or chronic asymptomatic colonization. With strains causing clinical symptoms, the presence of an implant significantly worsened infection. For asymptomatic colonizers, further studies investigating their long-term impacts, especially during periods of immunosuppression in hosts, are needed.