Panton-Valentine leucocidin toxin-positive staphylococcus aureus-mediated neonatal mastitis.

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A case of Panton–Valentine leucocidin toxin-positive staphylococcus aureus-mediated neonatal mastitis

Introduction: Neonatal mastitis is an inflammatory condition of the breast frequently associated with Staphylococcus aureus. While Panton–Valentine leucocidin (PVL), a B-pore-forming cytotoxin, is commonly associated with enhanced virulence in community-acquired methicillinresistant S. aureus isolates, this is the first report to our knowledge of neonatal mastitis caused by PVL-positive S. aureus. Case presentation: A 20-day-old full-term female neonate presented with bilateral mastitis, complicated by bilateral abscess formation. PVL toxin-positive S. aureus was cultured from aspirates of both breasts. All family members, none of whom presented with symptoms of infection, and, specifically, maternal vaginal samples proved negative for PVL-positive S. aureus. Successful resolution involved surgical drainage and clindamycin therapy. Conclusion: While PVL toxin-positive S. aureus has previously been implicated in bovine and ovine mastitis, there may now be a need for vigilance with respect to human incidence. Due to PVL-mediated tissue necrosis, breast abscess formation and poor response to conventional antimicrobial therapy should, perhaps, be a cause for suspicion of PVL-bearing S. aureus and expediting of appropriate therapy to avoid potential for long-term consequences such as abnormal breast development

Expression of annexin A2 promotes cancer progression in estrogen receptor negative breast cancers

When breast cancer progresses to a metastatic stage, survival rates decline rapidly and it is considered incurable. Thus, deciphering the critical mechanisms of metastasis is of vital importance to develop new treatment options. We hypothesize that studying the proteins that are newly synthesized during the metastatic processes of migration and invasion will greatly enhance our understanding of breast cancer progression. We conducted a mass spectrometry screen following bioorthogonal noncanonical amino acid tagging to elucidate changes in the nascent proteome that occur during epidermal growth factor stimulation in migrating and invading cells. Annexin A2 was identified in this screen and subsequent examination of breast cancer cell lines revealed that Annexin A2 is specifically upregulated in estrogen receptor negative (ER-) cell lines. Furthermore, siRNA knockdown showed that Annexin A2 expression promotes the proliferation, wound healing and directional migration of breast cancer cells. In patients, Annexin A2 expression is increased in ER- breast cancer subtypes. Additionally, high Annexin A2 expression confers a higher probability of distant metastasis specifically for ER- patients. This work establishes a pivotal role of Annexin A2 in breast cancer progression and identifies Annexin A2 as a potential therapeutic target for the more aggressive and harder to treat ER- subtype