Role of bacterial components in macrophage activation by the LAC and MW2 strains of community-associated, methicillin-resistant Staphylococcus aureus.

We tested the contribution of four staphylococcal components - PSM-α, PSM-ß, δ-toxin, and PVL - in triggering macrophage secretion of tumor necrosis factor (TNF) and interleukins 6 (IL-6) and 12 (IL-12) by two prominent, circulating strains of community-associated, methicillin-resistant Staphylococcus aureus (CA-MRSA): LAC, USA300; MW2, USA400. RAW 264.7 murine macrophages were stimulated with live, antibiotic-exposed bacteria, and cytokine secretion was quantitated in supernatants. Deletion of PSM-α expression in LAC led to >50% reduction in macrophage TNF and IL-6 secretion and a 20% reduction in IL-12 secretion, while PSM-α deletion in MW2 did not significantly reduce macrophage TNF secretion but resulted in a 15-20% reduction in IL-6 and IL-12 secretion. Deletion of δ-toxin in either strain led to more than 50% reduction in macrophage IL-6 secretion and smaller reductions in macrophage TNF and IL-12 secretion (8-25%). Our data implicate both PSM-α and δ-toxin in stimulating macrophage cytokine responses to CA-MRSA bacteria.

A multipronged approach is associated with improved breast milk feeding rates in very low birth weight infants of an inner-city hospital.

Breast milk feeding has advantages over formula feeding in premature infants, but its use in them is low. We initiated measures in our inner-city hospital such as starting a dedicated lactation service, counseling the mothers prenatally and postnatally, educating hospital staff, and advocating with our state's Medicaid insurance to provide free home breast pumps. These measures were associated with improvement in our breast milk feeding rates in very low birth weight infants from 22% to 88% over 5 years. This article describes our multipronged approach and can help encourage and guide other units with similar demographics to improve their breast milk feeding rates.