Research ArticleVascular Biology

Methicillin-resistant Staphylococcus aureus causes sustained collecting lymphatic vessel dysfunction

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Science Translational Medicine  17 Jan 2018:
Vol. 10, Issue 424, eaam7964
DOI: 10.1126/scitranslmed.aam7964

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Lymphatics limp along after MRSA

Lymphedema is associated with skin and soft tissue infections, and both can be recurring, causing continual suffering in affected patients. To better understand the relationship between bacterial infections and lymphedema, Jones et al. used intravital imaging to examine the lymphatics of mice infected with MRSA. They observed lymphatic muscle cell death, which led to prolonged dysfunction months after the bacteria had been cleared. In vitro experiments with human cells indicated that bacterial toxins were responsible for damaging the lymphatic muscle cells, suggesting that the toxins could be targeted in patients to interrupt this brutal cycle.

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of morbidity and mortality worldwide and is a frequent cause of skin and soft tissue infections (SSTIs). Lymphedema—fluid accumulation in tissue caused by impaired lymphatic vessel function—is a strong risk factor for SSTIs. SSTIs also frequently recur in patients and sometimes lead to acquired lymphedema. However, the mechanism of how SSTIs can be both the consequence and the cause of lymphatic vessel dysfunction is not known. Intravital imaging in mice revealed an acute reduction in both lymphatic vessel contractility and lymph flow after localized MRSA infection. Moreover, chronic lymphatic impairment is observed long after MRSA is cleared and inflammation is resolved. Associated with decreased collecting lymphatic vessel function was the loss and disorganization of lymphatic muscle cells (LMCs), which are critical for lymphatic contraction. In vitro, incubation with MRSA-conditioned supernatant led to LMC death. Proteomic analysis identified several accessory gene regulator (agr)–controlled MRSA exotoxins that contribute to LMC death. Infection with agr mutant MRSA resulted in sustained lymphatic function compared to animals infected with wild-type MRSA. Our findings suggest that agr is a promising target to preserve lymphatic vessel function and promote immunity during SSTIs.

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