Plasmid-Mediated OqxAB Is an Important Mechanism for Nitrofurantoin Resistance in Escherichia coli

Increasing consumption of nitrofurantoin (NIT) for treatment of acute uncomplicated urinary tract infections (UTI) highlights the need to monitor emerging NIT resistance mechanisms. This study investigated the molecular epidemiology of the multidrug-resistant efflux gene oqxAB and its contribution to nitrofurantoin resistance by using Escherichia coli isolates originating from patients with UTI (n = 205; collected in 2004 to 2013) and food-producing animals (n = 136; collected in 2012 to 2013) in Hong Kong. The oqxAB gene was highly prevalent among NIT-intermediate (11.5% to 45.5%) and -resistant (39.2% to 65.5%) isolates but rare (0% to 1.7%) among NIT-susceptible (NIT-S) isolates. In our isolates, the oqxAB gene was associated with IS26 and was carried by plasmids of diverse replicon types. Multilocus sequence typing revealed that the clones of oqxAB-positive E. coli were diverse. The combination of oqxAB and nfsA mutations was found to be sufficient for high-level NIT resistance. Curing of oqxAB-carrying plasmids from 20 NIT-intermediate/resistant UTI isolates markedly reduced the geometric mean MIC of NIT from 168.9 μg/ml to 34.3 μg/ml. In the plasmid-cured variants, 20% (1/5) of isolates with nfsA mutations were NIT-S, while 80% (12/15) of isolates without nfsA mutations were NIT-S (P = 0.015). The presence of plasmid-based oqxAB increased the mutation prevention concentration of NIT from 128 μg/ml to 256 μg/ml and facilitated the development of clinically important levels of nitrofurantoin resistance. In conclusion, plasmid-mediated oqxAB is an important nitrofurantoin resistance mechanism. There is a great need to monitor the dissemination of this transferable multidrug-resistant efflux pump.     

Multi-level corpectomies and reconstruction via a single posterolateral approach

The surgical treatment of ventral spinal canal compression has traditionally required either an anterior or combined anterior–posterior decompression and stabilization. These types of approaches carry a significant morbidity and may not be appropriate for all patients. We report our experience with multi-level corpectomies and reconstruction performed via a single, posterolateral approach. A retrospective review was performed of six consecutive patients at a single institution who were treated for ventral multi-level spinal cord compression via a single posterolateral approach. All six patients underwent reconstruction and stabilization with an expandable cage and posterior fixation. Five patients had metastatic cancer with spinal cord compression and one patient had osteomyelitis with a ventral epidural abscess and vertebral body collapse. All patients underwent 2-level corpectomies. Pre-operative and post-operative neurologic function and stabilization construct integrity were analyzed. All patients had successful decompression and stabilization and there were no hardware complications. Three peri-operative complications were encountered: post-operative pleural effusion needing thoracostomy drainage, transient leg paresis that resolved at 2 months and a post-operative wound infection needing operative debridement. At last follow-up all patients had improvement or stabilization of their neurological function. Long-term follow-up was limited by the progression of metastatic disease and death in all the patients with cancer. This study demonstrates that symptomatic improvement can be achieved in select patients requiring multi-level corpectomies when using a single posterolateral approach with expandable cage reconstruction and posterior stabilization.     

Implantable Cardioverter‐Defibrillator Shock: Appropriate or Inappropriate?

A 76‐year‐old female with a single chamber implantable cardioverter‐defibrillator implanted for secondary prevention was referred due to multiple discharges. The device was programmed for ventricular tachycardia (VT) detection at 400 ms, fast VT detection at 280 ms, and ventricular fibrillation detection at 320 ms. Antitachycardia pacing (ATP) during charge was enabled. Interrogation revealed a VT episode with a mean cycle length of 270 ms, which was successfully terminated with ATP during charge. Seconds later, the device delivered a shock. This case illustrates the importance of understanding programming algorithms as part of troubleshooting when facing a scenario of device discharge. Ann Noninvasive Electrocardiol 2010;15(2):181–183     

Dialysis Practices That Distinguish Facilities with Below- versus Above-Expected Mortality

Background and objectives: Mortality rates vary widely among dialysis facilities even after adjustment with standardized mortality ratios (SMRs). This variation may occur because top-performing facilities use practices not shared by others, because the SMR fails to capture key patient characteristics, or both. Practices were identified that distinguish top- from bottom-performing facilities by SMR.Design, setting, participants, & measurements: A cross-sectional survey was performed of staff across three organizations. Staff members rated the perceived quality of their units'' patient-, provider-, and facility-level practices using a six-point Likert scale. Facilities were divided into those with above- versus below-expected mortality on the basis of SMRs from U.S. Renal Data Service facility reports. Mean Likert scores were computed for each practice using t tests. Practices that were statistically significant (P ≤ 0.05) and achieved at least a medium effect size of ≥0.4 were reported. Significant predictors were entered into a linear regression model.Results: Dialysis facilities with below-expected mortality reported that patients in their unit were more activated and engaged, physician communication and interpersonal relationships were stronger, dieticians were more resourceful and knowledgeable, and overall coordination and staff management were superior versus facilities with above-expected mortality. Staff ratings of these practices explained 31% of the variance in SMRs.Conclusions: Patient-, provider-, and facility-level practices partly explain SMR variation among facilities. Improving SMRs may require processes that reflect a coordinated, multidisciplinary environment (i.e., no one group, practice, or characteristic will drive facility-level SMRs). Understanding and improving SMRs will require a holistic view of the facility.Since 1995, the U.S. Renal Data System (USRDS) has calculated standardized mortality ratios (SMRs) to estimate patient survival in dialysis facilities. Because unadjusted mortality rates cannot capture the inevitable case-mix variations among facilities, the SMR is adjusted for a range of variables including age, sex, race, disease duration, comorbidities, nursing home status, and body mass index (1,2). SMR further adjusts for underlying mortality rates by scaling observed mortality by expected mortality on the basis of national data. Individual facilities are classified as having lower (SMR < 1.0), higher (SMR > 1.0), or as-expected (SMR = 1.0) mortality compared with the national average (1,2). This information is publicly available (3) and allows payers and consumers to monitor quality within individual facilities and to compare quality among facilities.Despite attempts to adjust for case-mix variations, patient survival varies among dialysis facilities even after adjustment. McClellan and colleagues evaluated mortality rates in a cohort of dialysis units and showed that facility-specific mortality ranged between 2.0 and 10.5 deaths per 10,000 patient days; variations remained after extensive adjustment (4). Goodkin and colleagues found that intra- and international mortality variations also remained after adjusting for a range of demographic characteristics and comorbidities (5). In short, mortality varies from center to center, and this variation is not explained by case-mix adjustment alone.If case-mix adjustment is inadequate to fully explain mortality variations, then what else might explain the differences? One possibility is that there may be important differences in facility-level factors that affect SMRs. These factors may include procedural (e.g., implementation patterns of policies in a facility), attitudinal (e.g., staff morale), interpersonal (e.g., staff communication), or structural (e.g., layout of facilities) practices associated with reduced SMRs (6). There may also be additional patient-level characteristics that are unaccounted for with standard case-mix adjustment. These factors may be incremental to standard demographics and comorbidities or may even supersede those factors. For example, it is possible that top-performing units have more compliant, more motivated, or more disciplined patients compared with bottom-performing units—all characteristics that elude standardized adjustments.To test the hypothesis that there are patient-, provider-, and facility-level factors that are associated with SMRs, and to further elucidate predictors of SMRs, we conducted the Identifying Best Practices in Dialysis (IBPiD) study; this study aims to catalogue best practices associated with improved patient outcomes in dialysis, including SMRs (6). In this study, we identify predictors of mortality that are not traditionally included in case-mix adjustments.