Optimal medical management in patients undergoing peripheral vascular interventions for chronic limb-threatening ischemia is associated with improved outcomes.

OBJECTIVE: Optimizing medical management and risk factor modification are underused strategies in patients with chronic limb-threatening ischemia (CLTI), despite evidence of improved outcomes. The Vascular Quality Initiative (VQI) registry is a tool to improve quality of vascular care. In this study, we used the VQI to evaluate trends in medical management in patients with CLTI undergoing peripheral vascular interventions (PVI), and the impact of changes in management on overall survival (OS), amputation-free survival (AFS), and limb salvage (LS). METHODS: Patients undergoing index PVI for CLTI between 2012 and 2016, with ≥24 months of follow-up were identified from the national VQI registry. Patient details including smoking status and medication use, OS, LS, and AFS were analyzed with linear-by-linear association, t test, and logistic regression. RESULTS: There were 12,370 PVI completed in 11,466 patients. There was a significant increase in infrapopliteal interventions (from 29.8% to 39.0%; P < .001) and PVI performed for tissue loss (from 59.1% to 66.5%; P < .001). The percentage of current smokers at time of PVI decreased (from 36.2% to 30.7%; P = .036). At discharge, statins were initiated in 25%, aspirin in 45%, and P2Y12 therapy in 58% of patients not receiving these medications before PVI. Over the course of follow-up, dual antiplatelet therapy (DAPT) (from 41.1% to 48.0%; P < .001), angiotensin-converting enzyme (ACE) inhibitor (from 46.2% to 51.3%; P < .001), and statin (from 70.4% to 77.5%; P < .001) use increased. Combined DAPT, ACE inhibitor and statin use increased from 33.6% to 39.6% (P ≤ .001). Significant improvement in 24-month OS and AFS was noted (OS, from 90.9% to 93.7% [P = .002]: AFS, from 81.2% to 83.1% [P = .046]), but not LS (from 89.6% to 89.0%; P = .83). Combined therapy with P2Y12 inhibitors, statins and ACE inhibitors was an independent predictor of improved OS (hazard ratio, 0.61; 95% confidence interval, 0.39-0.96; P = .034). DAPT was independent predictor of improved LS (hazard ratio, 0.83; 95% confidence interval, 0.79-0.87; P < .007). CONCLUSIONS: Antiplatelet, ACE inhibitor, and statin use increased over the study period and was associated with improved OS and AFS. LS trends did not change significantly over time, possibly owing to the inclusion of patients with a greater disease burden or inadequate medical management. Medical management, although improved, remained far from optimal and represents an area for continued development.

Structure and Dynamics of FosA-Mediated Fosfomycin Resistance in Klebsiella pneumoniae and Escherichia coli.

Fosfomycin exhibits broad-spectrum antibacterial activity and is being reevaluated for the treatment of extensively drug-resistant pathogens. Its activity in Gram-negative organisms, however, can be compromised by expression of FosA, a metal-dependent transferase that catalyzes the conjugation of glutathione to fosfomycin, rendering the antibiotic inactive. In this study, we solved the crystal structures of two of the most clinically relevant FosA enzymes: plasmid-encoded FosA3 from Escherichia coli and chromosomally encoded FosA from Klebsiella pneumoniae (FosAKP). The structure, molecular dynamics, catalytic activity, and fosfomycin resistance of FosA3 and FosAKP were also compared to those of FosA from Pseudomonas aeruginosa (FosAPA), for which prior crystal structures exist. E. coli TOP10 transformants expressing FosA3 and FosAKP conferred significantly greater fosfomycin resistance (MIC, >1,024 µg/ml) than those expressing FosAPA (MIC, 16 µg/ml), which could be explained in part by the higher catalytic efficiencies of the FosA3 and FosAKP enzymes. Interestingly, these differences in enzyme activity could not be attributed to structural differences at their active sites. Instead, molecular dynamics simulations and hydrogen-deuterium exchange experiments with FosAKP revealed dynamic interconnectivity between its active sites and a loop structure that extends from the active site of each monomer and traverses the dimer interface. This dimer interface loop is longer and more extended in FosAKP and FosA3 than in FosAPA, and kinetic analyses of FosAKP and FosAPA loop-swapped chimeric enzymes highlighted its importance in FosA activity. Collectively, these data yield novel insights into fosfomycin resistance that could be leveraged to develop new strategies to inhibit FosA and potentiate fosfomycin activity.