Spontaneous preputial gland adenitis in Staphylococcus aureus-colonized male C57Bl/6 mice triggers a Th17-driven immune response

Individuals colonized with the pathobiont Staphylococcus aureus can develop endogenous S. aureus infections if the delicate balance between host and microbe is disturbed. We have recently developed a model of persistent S. aureus colonization using the mouse-adapted S. aureus strain JSNZ. This strain is efficiently transferred from the parents to the offspring, leading to lifelong and usually asymptomatic colonization. Here we report that adult male mice frequently develop spontaneous infections of their preputial glands (preputial gland adenitis, PGA), which are characterized by significant pus production and gland enlargement. This study aimed to characterize PGA in terms of phenotype, causative agents, and the pathogen-specific antibody and T cell responses. To this end, we compared naive mice, S. aureus-colonized PGA-negative mice with S. aureus-colonized, PGA-positive mice. PGA occurred in 8/12 (67%) of the male breeding animals and in 17/25 (68%) of the adult male offspring. The infection was not self-resolving, but persisted for several months. Genotyping revealed that the colonizing S. aureus strain JSNZ was the causative agent of PGA. The infection caused a purulent inflammation, characterized by massive bacterial aggregates and neutrophil infiltrates in the gland lumen leading to complete disruption of the glandular architecture. PGA induced a strong, but localized release of IL-1, IL-1{beta}, IL-17, MIP-1 and KC in the infected gland. T cells from PGA-draining lymph nodes as well as splenocytes reacted to in vitro re-stimulation with a S. aureus antigen cocktail with the proliferation of Th17 cells, and the release of IL-17 and IFN-{gamma}, corresponding to a type 1/3-immune response. To conclude, the pathology of this spontaneous and chronic S. aureus infection is driven by a strong type 3-biased immune response that is unable to clear the infection. This endogenous PGA model will be a valuable tool for studying host-pathogen interactions in natural S. aureus infections. Author SummaryAround one in five people naturally carry Staphylococcus aureus bacteria in their noses, usually without any problems. But if something upsets the balance--like a cut on the skin or a weakened immune system--these bacteria can cause a range of infections such as boils and abscesses, wound infections, and sepsis. To better understand how this happens, we developed a special mouse model where the mice are colonized with S. aureus in their noses, just like people are. Interestingly, over half of the male mice developed abscesses caused by their colonizing S. aureus strain. Even though the immune system reacted with strong local inflammation, a Th17-driven T cell response and antibody production, the bacteria were not cleared. This well reflects the human situation, where S. aureus infections are often persistent. This new mouse model helps us study exactly what causes the balance to tip, turning harmless bacteria into harmful invaders. By learning more about these triggers, we hope to find better ways to prevent and treat infections caused by S. aureus.