Surface Hardness Impairment of Quorum Sensing and Swarming for Pseudomonas aeruginosa

The importance of rhamnolipid to swarming of the bacterium Pseudomonas aeruginosa is well established. It is frequently, but not exclusively, observed that P. aeruginosa swarms in tendril patterns—formation of these tendrils requires rhamnolipid. We were interested to explain the impact of surface changes on P. aeruginosa swarm tendril development. Here we report that P. aeruginosa quorum sensing and rhamnolipid production is impaired when growing on harder semi-solid surfaces. P. aeruginosa wild-type swarms showed huge variation in tendril formation with small deviations to the “standard” swarm agar concentration of 0.5%. These macroscopic differences correlated with microscopic investigation of cells close to the advancing swarm edge using fluorescent gene reporters. Tendril swarms showed significant rhlA-gfp reporter expression right up to the advancing edge of swarming cells while swarms without tendrils (grown on harder agar) showed no rhlA-gfp reporter expression near the advancing edge. This difference in rhamnolipid gene expression can be explained by the necessity of quorum sensing for rhamnolipid production. We provide evidence that harder surfaces seem to limit induction of quorum sensing genes near the advancing swarm edge and these localized effects were sufficient to explain the lack of tendril formation on hard agar. We were unable to artificially stimulate rhamnolipid tendril formation with added acyl-homoserine lactone signals or increasing the carbon nutrients. This suggests that quorum sensing on surfaces is controlled in a manner that is not solely population dependent

Compensating control participants when the intervention is of significant value: experience in Guatemala, India, Peru and Rwanda

The Household Air Pollution Intervention Network (HAPIN) trial is a randomised controlled trial in Guatemala, India, Peru and Rwanda to assess the health impact of a clean cooking intervention in households using solid biomass for cooking. The HAPIN intervention—a liquefied petroleum gas (LPG) stove and 18-month supply of LPG—has significant value in these communities, irrespective of potential health benefits. For control households, it was necessary to develop a compensation strategy that would be comparable across four settings and would address concerns about differential loss to follow-up, fairness and potential effects on household economics. Each site developed slightly different, contextually appropriate compensation packages by combining a set of uniform principles with local community input. In Guatemala, control compensation consists of coupons equivalent to the LPG stove’s value that can be redeemed for the participant’s choice of household items, which could include an LPG stove. In Peru, control households receive several small items during the trial, plus the intervention stove and 1 month of fuel at the trial’s conclusion. Rwandan participants are given small items during the trial and a choice of a solar kit, LPG stove and four fuel refills, or cash equivalent at the end. India is the only setting in which control participants receive the intervention (LPG stove and 18 months of fuel) at the trial’s end while also being compensated for their time during the trial, in accordance with local ethics committee requirements. The approaches presented here could inform compensation strategy development in future multi-country trials

Improving nutritional care quality in the orthopedic ward of a Septic Surgery Center by implementing a preventive nutritional policy using the Nutritional Risk Score: a pilot study.

Septic Surgery Center (SSC) patients are at a particularly high risk of protein-energy malnutrition (PEM), with a prevalence of 35-85% found in various studies. Previous collaboration between our hospital's SSC and its Clinical Nutrition Team (CNT) only focussed on patients with severe PEM. This study aimed to determine whether it was possible to improve the quality of nutritional care in septic surgery patients with help of a nutritional policy using the Nutritional Risk Score (NRS). Nutritional practices in the SSC were observed over three separate periods: in the 3 months leading up to the implementation baseline, 6 months after implementation of preventive nutritional practices, and at 3 years. The nutritional care quality indicator was the percentage of patients whose nutritional care, as prescribed by the SSC, was adapted to their specific requirements. We determined the septic surgery team's NRS completion rate and calculated the nutritional policy's impact on SSC length of stay. Data before (T <sub>0</sub> ) and after (T <sub>1</sub> + T <sub>2</sub> ) implementation of the nutritional policy were compared. Ninety-eight patients were included. The nutritional care-quality indicator improved from 26 to 81% between T <sub>0</sub> and T <sub>2</sub> . During the T <sub>1</sub> and T <sub>2</sub> audits, septic surgery nurses calculated NRS for 100% and 97% of patients, respectively. Excluding patients with severe PEM, SSC length of stay was significantly reduced by 23 days (p = 0.005). These findings showed that implementing a nutritional policy in an SSC is possible with the help of an algorithm including an easy-to-use tool like the NRS

Resistin serum levels are increased but not correlated with insulin resistance in chronic hemodialysis patients

Background/Aims: Insulin resistance is a well-known phenomenon in uremia. Resistin, a recently discovered insulin inhibitor secreted by adipocytes, is associated with obesity and insulin resistance in mice. Adiponectin, also secreted by adipocytes, is known to reduce insulin resistance in humans. The aim of the present study was to address the hypothesis that changes in resistin or adiponectin serum levels may relate to body composition and to insulin resistance in patients with end-stage renal disease. Methods: In a cross-sectional study, 33 non-diabetic patients ( 24 males and 9 females, mean age 61.5 +/- 15.8 years) with end-stage renal disease on chronic hemodialysis (treatment duration 41 +/- 31 months) that lacked signs of infection were enrolled. The control group consisted of 33, matched for age, sex and body mass index (BMI), healthy volunteers ( 22 males, 11 females, mean age 62.6 +/- 12.1 years). BMI (kg/m(2)) was calculated from body weight and height. Body fat (%) was measured by means of bioelectrical impedance. Blood samples were taken always in the morning after a 12-hour fasting period before and after the hemodialysis session. Resistin and adiponectin serum concentrations were measured by enzyme immunoassays and insulin by an electrochemiluminescence immunoassay. The posttreatment values were corrected regarding the hemoconcentration. The homeostasis model assessment index (HOMA-R) was calculated as an estimate of insulin resistance from the fasting glucose and insulin serum levels. Results: Pre-treatment resistin serum levels were significantly increased in hemodialysis patients compared to healthy controls (19.2 +/- 6.2 vs. 3.9 +/- 1.8 ng/ml; p < 0.001). Hemodialysis did not alter resistin levels, as pre- and post-treatment levels were not different when corrected for hemoconcentration (19.2 +/- 6.2 vs. 18.7 +/- 5.0 ng/ml; p = 0.54). Adiponectin levels were also increased in hemodialysis patients compared to healthy controls (25.4 +/- 21.5 vs. 10.5 +/- 5.9 mu g/ml; p < 0.001). A significant inverse correlation was observed between the serum adiponectin levels before the hemodialysis session on the one hand and the BMI ( r = - 0.527, p = 0.002), the HOMA-R ( r = - 0.378, p < 0.05) and the fasting insulin levels ( r = - 0.397, p < 0.05) on the other. However, no significant correlation was observed between serum resistin levels on the one hand versus HOMA-R index (3.2 +/- 3.9 mmol center dot mu IU/ml; r = - 0.098, p = 0.59), insulin levels (13.3 +/- 14.4 mU/l; r = - 0.073, p = 0.69), glucose levels ( 89 +/- 13 mg/dl; r = - 0.049, p = 0.78), BMI (25.6 +/- 3.7 kg/m(2); r = - 0.041, p = 0.82) and body fat content (26.4 +/- 8.4%; r = - 0.018, p = 0.94) on the other hand. Conclusion: Resistin serum levels are significantly elevated in non-diabetic patients with end-stage renal disease that are treated by hemodialysis. The hemodialysis procedure does not affect the resistin levels. Along with previous observations in patients with renal insufficiency in the pre-dialysis stage, our findings implicate an important role of the kidney in resistin elimination. However, increased resistin serum levels in hemodialysis patients are not related to reduced insulin sensitivity encountered in uremia. Copyright (C) 2005 S. Karger AG, Basel