A Requirement of TolC and MDR Efflux Pumps for Acid Adaptation and GadAB Induction in Escherichia coli

BACKGROUND: The TolC outer membrane channel is a key component of several multidrug resistance (MDR) efflux pumps driven by H(+) transport in Escherichia coli. While tolC expression is under the regulation of the EvgA-Gad acid resistance regulon, the role of TolC in growth at low pH and extreme-acid survival is unknown. METHODS AND PRINCIPAL FINDINGS: TolC was required for extreme-acid survival (pH 2) of strain W3110 grown aerobically to stationary phase. A tolC deletion decreased extreme-acid survival (acid resistance) of aerated pH 7.0-grown cells by 10(5)-fold and of pH 5.5-grown cells by 10-fold. The requirement was specific for acid resistance since a tolC defect had no effect on aerobic survival in extreme base (pH 10). TolC was required for expression of glutamate decarboxylase (GadA, GadB), a key component of glutamate-dependent acid resistance (Gad). TolC was also required for maximal exponential growth of E. coli K-12 W3110, in LBK medium buffered at pH 4.5-6.0, but not at pH 6.5-8.5. The TolC growth requirement in moderate acid was independent of Gad. TolC-associated pump components EmrB and MdtB contributed to survival in extreme acid (pH 2), but were not required for growth at pH 5. A mutant lacking the known TolC-associated efflux pumps (acrB, acrD, emrB, emrY, macB, mdtC, mdtF, acrEF) showed no growth defect at acidic pH and a relatively small decrease in extreme-acid survival when pre-grown at pH 5.5. CONCLUSIONS: TolC and proton-driven MDR efflux pump components EmrB and MdtB contribute to E. coli survival in extreme acid and TolC is required for maximal growth rates below pH 6.5. The TolC enhancement of extreme-acid survival includes Gad induction, but TolC-dependent growth rates below pH 6.5 do not involve Gad. That MDR resistance can enhance growth and survival in acid is an important consideration for enteric organisms passing through the acidic stomach

Altering Knee Abduction Angular Impulse Using Wedged Insoles for Treatment of Patellofemoral Pain in Runners: A Six-Week Randomized Controlled Trial

<div><p>Objective</p><p>Determine if a change in internal knee abduction angular impulse (KAAI) is related to pain reduction for runners with patellofemoral pain (PFP) by comparing lateral and medial wedge insole interventions, and increased KAAI and decreased KAAI groups.</p><p>Design</p><p>Randomized controlled clinical trial (<a href="http://ClinicalTrials.gov" target="_blank">ClinicalTrials.gov</a> ID# NCT01332110).</p><p>Setting</p><p>Biomechanics laboratory and community.</p><p>Patients</p><p>Thirty-six runners with physician-diagnosed PFP enrolled in the trial, and 27 were analyzed.</p><p>Interventions</p><p>Runners with PFP were randomly assigned to either an experimental 3 mm lateral wedge or control 6 mm medial wedge group. Participants completed a biomechanical gait analysis to quantify KAAIs with their assigned insole, and then used their assigned insole for six-weeks during their regular runs. Usual pain during running was measured at baseline and at six-week follow-up using a visual analog scale. Statistical tests were performed to identify differences between wedge types, differences between biomechanical response types (i.e. increase or decrease KAAI), as well as predictors of pain reduction.</p><p>Main Outcome Measures</p><p>Percent change in KAAI relative to neutral, and % change in pain over six weeks.</p><p>Results</p><p>Clinically meaningful reductions in pain (>33%) were measured for both footwear groups; however, no significant differences between footwear groups were found (<i>p</i> = 0.697). When participants were regrouped based on KAAI change (i.e., increase or decrease), again, no significant differences in pain reduction were noted (<i>p</i> = 0.146). Interestingly, when evaluating absolute change in KAAI, a significant relationship between absolute % change in KAAI and % pain reduction was observed (<i>R</i>² = 0.21; <i>p</i> = 0.030), after adjusting for baseline pain levels.</p><p>Conclusion</p><p>The greater the absolute % change in KAAI during running, the greater the % reduction in pain over six weeks, regardless of wedge type, and whether KAAIs increased or decreased. Lateral and medial wedge insoles were similar in effectiveness for treatment of PFP.</p><p>Clinical Relevance</p><p>Altering KAAI should be a focus of future PFP research. Lateral wedges should be studied further as an alternative therapy to medial wedges for management of PFP.</p><p>Trial Registration</p><p>ClinicalTrials.gov <a href="https://clinicaltrials.gov/ct2/show/NCT01332110?term=NCT01332110" target="_blank">NCT01332110</a></p></div

Main results of this study are displayed for each footwear group, and the regroupings^* after the six-week intervention.

<p>* subjects were regrouped based on whether they experienced increased or decreased KAAIs with their assigned footwear, regardless of wedge type</p><p>† significant at α = 0.05</p><p>Mean differences between groups are shown with 95% confidence intervals. Negative % change values indicate that there was a decrease from baseline.</p

The wedged insole conditions tested in this study.

<p>On right, the 6mm medial wedge is shown. On left, the 3mm lateral wedge is shown.</p

Scatter plot showing relationship between absolute change in knee abduction angular impulse (KAAI) with wedged intervention and pain reduction over 6 weeks.

<p>The regression analysis in this article also adjusted for baseline pain; however a 2-dimensional graph is shown here for clarity.</p

Baseline characteristics.

<p>* subjects were regrouped based on whether they experienced increased or decreased KAAIs with their assigned footwear, regardless of wedge type</p><p>Baseline characteristics are shown for each footwear group, and the regroupings^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134461#t002fn001" target="_blank">*</a>}. Baseline measures were compared using paired-samples two-tailed t-tests (α = 0.05).</p

Photograph of an experimental trial occurring.

<p>The motion capture cameras, force platform, timing system, and retroreflective markers can be seen.</p