Staphylococcus aureus is the leading cause of wound and hospitalacquired infections worldwide. The emergence of S. aureus strains with resistance to multiple antibiotics requires the identification of bacterial virulence genes and the development of novel therapeutic strategies. Herein, bursa aurealis, a mariner-based transposon, was used for random mutagenesis and for the isolation of 10,325 S. aureus variants with defined insertion sites. By screening for loss-of-function mutants in a Caenorhabditis elegans killing assay, 71 S. aureus virulence genes were identified. Some of these genes are also required for S. aureus abscess formation in a murine infection model. transposon ͉ Caenorhabditis elegans

Bacteria that express contact-dependent growth inhibition (CDI) systems outcompete siblings that lack immunity, suggesting that CDI mediates intercellular competition. To further explore the role of CDI in competition, we determined the target cell range of the CDIEC93 system from Escherichia coli EC93. The CdiAEC93 effector protein recognizes the widely conserved BamA protein as a receptor, yet E. coli EC93 does not inhibit other enterobacterial species. The predicted membrane topology of BamA indicates that three of its extracellular loops vary considerably between species, suggesting that loop heterogeneity may control CDI specificity. Consistent with this hypothesis, other enterobacteria are sensitized to CDIEC93 upon the expression of E. coli bamA and E. coli cells become CDIEC93 resistant when bamA is replaced with alleles from other species. Our data indicate that BamA loops 6 and 7 form the CdiAEC93-binding epitope and their variation between species restricts CDIEC93 target cell selection. Although BamA loops 6 and 7 vary dramatically between species, these regions are identical in hundreds of E. coli strains, suggesting that BamAEcoli and CdiAEC93 play a role in self-nonself discrimination.

Summary CdiB/CdiA proteins mediate inter-bacterial competition in a process termed contact-dependent growth inhibition (CDI). Filamentous CdiA exoproteins extend from CDI+ cells and bind specific receptors to deliver toxins into susceptible target bacteria. CDI has also been implicated in auto-aggregation and biofilm formation in several species, but the contribution of CdiA-receptor interactions to these multi-cellular behaviors has not been examined. Using Escherichia coli isolate EC93 as a model, we show that cdiA and bamA receptor mutants are defective in biofilm formation, suggesting a prominent role for CdiA-BamA mediated cell-cell adhesion. However, CdiA also promotes auto-aggregation in a BamA-independent manner, indicating that the exoprotein possesses an additional adhesin activity. Cells must express CdiA in order to participate in BamA-independent aggregates, suggesting that adhesion could be mediated by homotypic CdiA-CdiA interactions. The BamA-dependent and BamA-independent interaction domains map to distinct regions within the CdiA filament. Thus, CdiA orchestrates a collective behavior that is independent of its growth-inhibition activity. This adhesion should enable “greenbeard” discrimination, in which genetically unrelated individuals cooperate with one another based on a single shared trait. This kind-selective social behavior could provide immediate fitness benefits to bacteria that acquire the systems through horizontal gene transfer.

Background: Complications following vascular procedures involving the groin can lead to significant morbidity. Achieving stable soft tissue coverage over sites of revascularization can help mitigate complications. Prior evidence supports the use of muscle flaps in reoperative groins and in high risk patient populations to reduce postoperative complications. Data regarding the use of prophylactic muscle flap coverage of the groin is lacking. Therefore, the purpose of this study is to evaluate the effect of immediate prophylactic muscle flap coverage of vascular wounds involving the groin. Methods: A retrospective cohort study was performed on all patients undergoing primary open vascular procedures involving the groin for occlusive, aneurysmal, or oncologic disease between 2014 and 2020 at a single institution where plastic surgery was involved in closure. Patient demographics, comorbidities, surgical details, and postoperative complications were compared between patients who had sartorius muscle flap coverage of the vascular repair versus layered closure alone. Results: A total of 133 consecutive groins were included in our analysis. A sartorius flap was used in 115 groins (86.5%) and a layered closure was used in 18 (13.5%). Wound breakdown was similar between groups (25.2% sartorius vs. 38.9% layered closure, P = 0.26). However, the rate of reoperation was significantly higher in the layered closure group (50.0% vs. 12.2%, P < 0.01). Among patients who experienced wound breakdown ( N = 36), a larger proportion of layered closure patients required operative intervention (71.4% vs. 20.7%, P = 0.02). Other rates of complications were not statistically different between groups. Conclusions: In patients undergoing primary open vascular procedures involving the groin, patients who underwent prophylactic sartorius muscle flap closure had lower rates of reoperation. Although incisional breakdown was similar between the groups overall, the presence of a vascularized muscle flap overlying the vascular repair was associated with reduced need for reoperation and allowed more wounds to be managed with local wound care alone. Consideration should be given to this low morbidity local muscle flap in patients undergoing vascular procedures involving the groin.

Background: In nipple-sparing mastectomy, adequate perfusion to the nipple-areolar complex (NAC) during reconstruction is paramount to avoiding unwanted outcomes. Previous studies have suggested that periareolar incisions may result in higher rates of NAC complications. However, studies to date have not specifically investigated this in prepectoral reconstruction. The purpose of this study is to evaluate the impact of incision location on NAC complications in patients undergoing prepectoral breast reconstruction. Methods: We performed a retrospective review of all patients who underwent immediate two-stage prepectoral breast reconstruction following nipple-sparing mastectomy between 2015 and 2018 at a single institution. We identified two types of incisions utilized: superior periareolar or inframammary fold (IMF). Patient demographics, comorbidities, and surgical details were compared between incision types, as were NAC complications. Results: A total of 181 consecutive prepectoral breast reconstructions were included for analysis. A superior periareolar incision was used in 113 reconstructions (62%), and an IMF incision was used in 68 reconstructions (38%). There were 33 (18%) total NAC complications in our series. The periareolar incision group had a higher rate of any NAC complication (25% versus 7.4%; P < 0.01), as well as a higher rate of nipple necrosis requiring debridement (9.7% versus 1.5%; P = 0.03). Conclusions: In patients undergoing immediate two-stage prepectoral breast reconstruction following nipple-sparing mastectomy, periareolar incisions are associated with an increased risk of NAC complications compared with IMF incisions. For patients who are candidates for either an IMF or periareolar incision, a periareolar incision should be avoided.