Cryptic silver resistance is prevalent and readily activated in certain Gram-negative pathogens

Objectives: To assess the prevalence of cryptic silver (Ag+) resistance amongst clinical isolates of Gram-negative bacteria, and to examine how overt Ag+ resistance becomes activated in such strains. Methods: Established methods were used to determine the susceptibility of 444 recent clinical isolates to Ag+, and to evaluate the potential for overt Ag+ resistance to emerge from these isolates by spontaneous mutation. The genetic basis for Ag+ resistance was investigated using PCR amplification and DNA sequencing. Results: None of the isolates tested displayed overt Ag+ resistance. However, upon silver challenge, high-level Ag+ resistance (silver nitrate MIC >128 mg/L) was selected at high frequency (10¯⁷ to 10¯⁸) in ˜76% isolates of Enterobacter spp., ˜58% isolates of Klebsiella spp., and ˜0.7% isolates of E. coli. All strains in which Ag+ resistance could be selected harboured the sil operon, with resistance in each case apparently resulting from activation of this system as a consequence of a single missense mutation in silS. By contrast, Ag+ resistance could not be selected in isolates lacking sil, which included all tested representatives of Acinetobacter baumannii, Pseudomonas aeruginosa, Proteus spp and Citrobacter spp. Conclusions: Whilst overt Ag+ resistance in Gram-negative pathogens is uncommon, cryptic Ag+ resistance pertaining to the sil operon is prevalent and readily activated in particular genera (Enterobacter and Klebsiella)

Environmentally friendly analysis of emerging contaminants by pressurized hot water extraction-stir bar sorptive extraction-derivatization and gas chromatography-mass spectrometry

This work describes the development, optimiza- tion, and validation of a new method for the simultaneous determination of a wide range of pharmaceuticals (beta- blockers, lipid regulators ... ) and personal care products (fragrances, UV filters, phthalates ... ) in both aqueous and solid environmental matrices. Target compounds were extracted from sediments using pressurized hot water ex- traction followed by stir bar sorptive extraction. The first stage was performed at 1,500 psi during three static extrac- tion cycles of 5 min each after optimizing the extraction temperature (50 – 150 °C) and addition of organic modifiers (% methanol) to water, the extraction solvent. Next, aqueous extracts and water samples were processed using polydime- thylsiloxane bars. Several parameters were optimized for this technique, including extraction and desorption time, ionic strength, presence of organic modifiers, and pH. Fi- nally, analytes were extracted from the bars by ultrasonic irradiation using a reduced amount of solvent (0.2 mL) prior to derivatization and gas chromatography – mass spectrome- try analysis. The optimized protocol uses minimal amounts of organic solvents (<10 mL/sample) and time ( ≈ 8 h/sam- ple) compared to previous ex isting methodologies. Low standard deviation (usually below 10 %) and limits of de- tection (sub-ppb) vouch for the applicability of the method- ology for the analysis of target compounds at trace levels. Once developed, the method was applied to determin

Live to cheat another day: bacterial dormancy facilitates the social exploitation of beta-lactamases

The breakdown of antibiotics by β-lactamases may be cooperative, since resistant cells can detoxify their environment and facilitate the growth of susceptible neighbours. However, previous studies of this phenomenon have used artificial bacterial vectors or engineered bacteria to increase the secretion of β-lactamases from cells. Here, we investigated whether a broad-spectrum β-lactamase gene carried by a naturally occurring plasmid (pCT) is cooperative under a range of conditions. In ordinary batch culture on solid media, there was little or no evidence that resistant bacteria could protect susceptible cells from ampicillin, although resistant colonies could locally detoxify this growth medium. However, when susceptible cells were inoculated at high densities, late-appearing phenotypically susceptible bacteria grew in the vicinity of resistant colonies. We infer that persisters, cells that have survived antibiotics by undergoing a period of dormancy, founded these satellite colonies. The number of persister colonies was positively correlated with the density of resistant colonies and increased as antibiotic concentrations decreased. We argue that detoxification can be cooperative under a limited range of conditions: if the toxins are bacteriostatic rather than bacteridical; or if susceptible cells invade communities after resistant bacteria; or if dormancy allows susceptible cells to avoid bactericides. Resistance and tolerance were previously thought to be independent solutions for surviving antibiotics. Here, we show that these are interacting strategies: the presence of bacteria adopting one solution can have substantial effects on the fitness of their neighbours

The Binding of Triclosan to SmeT, the Repressor of the Multidrug Efflux Pump SmeDEF, Induces Antibiotic Resistance in Stenotrophomonas maltophilia

The wide utilization of biocides poses a concern on the impact of these compounds on natural bacterial populations. Furthermore, it has been demonstrated that biocides can select, at least in laboratory experiments, antibiotic resistant bacteria. This situation has raised concerns, not just on scientists and clinicians, but also on regulatory agencies, which are demanding studies on the impact that the utilization of biocides may have on the development on resistance and consequently on the treatment of infectious diseases and on human health. In the present article, we explored the possibility that the widely used biocide triclosan might induce antibiotic resistance using as a model the opportunistic pathogen Stenotrophomonas maltophilia. Biochemical, functional and structural studies were performed, focusing on SmeDEF, the most relevant antibiotic- and triclosan-removing multidrug efflux pump of S. maltophilia. Expression of smeDEF is regulated by the repressor SmeT. Triclosan released SmeT from its operator and induces the expression of smeDEF, thus reducing the susceptibility of S. maltophilia to antibiotics in the presence of the biocide. The structure of SmeT bound to triclosan is described. Two molecules of triclosan were found to bind to one subunit of the SmeT homodimer. The binding of the biocide stabilizes the N terminal domain of both subunits in a conformation unable to bind DNA. To our knowledge this is the first crystal structure obtained for a transcriptional regulator bound to triclosan. This work provides the molecular basis for understanding the mechanisms allowing the induction of phenotypic resistance to antibiotics by triclosan

The effects of diet education plus light resistance training on coronary heart disease risk factors in community-dwelling older adults

Objectives: To examine the effects of diet education (DE) plus light resistance training (RT) on coronary heart disease risk (CHD) factors, specifically dietary quality, blood lipid and C-Reactive protein (CRP) concentrations in overweight and obese older adults in a community setting. Design: Community outreach intervention with a quasi-experimental design. Participants and Setting: A total of 96 subjects, 16 males and 80 females, aged 69.2 ± 6.2 years, community-dwelling, and from one of four senior centers in Rhode Island. Intervention: Subjects participated in 30 minutes of DE (once per week) and 80 minutes of RT (two separate sessions per week) for eight weeks. The DE sessions were led by a registered dietitian. Measurements: Anthropometrics (height, weight, waist circumference, hip circumference, and body composition), clinical (blood pressure), biochemical (lipid profile, glucose, and CRP concentrations), and diet quality measured by the Dietary Screening Tool (DST). Results: A significant change was seen in DST risk categories from baseline to postintervention, χ2 (2)=20.43, p \u3c 0.01. Significant differences were seen in triacylglycerol (p=0.028) as well as in systolic and diastolic blood pressures, weight, waist circumference, hip circumference, percent body fat, fat mass, and body mass index (all p\u3c0.05). Conclusion: This intervention effectively decreased CHD risk in overweight and obese older adults. Future research is needed to examine the effects of longer DE plus RT interventions with greater weight loss on the lipid profile and CRP concentrations in overweight and obese older adults at risk for CHD. © 2011 Serdi and Springer Verlag France

P-598 Dose accuracy of the follitropin-alfa, follitropin-alfa/lutropin-alfa and choriogonadotropin-alfa pen injectors used for fertility treatment

Study question Do the Merck family of fertility pen injectors (follitropin-alfa, follitropin-alfa/lutropin-alfa, choriogonadotropin-alfa) meet the International Organization for Standardization (ISO 11608-1:2000/2012/2014) product-validation requirements

Effects of resistance training and dietary changes on physical function and body composition in overweight and obese older adults

Background: Community-based interventions that incorporate resistance training (RT) and dietary changes have not been extensively studied in overweight and obese older adults. The purpose of this investigation was to determine the effects of a community-based RT and dietary intervention on physical function and body composition in overweight and obese older adults. Methods: Ninety-five overweight and obese (BMI = 33.4 ± 4.0 kg/m 2) older adults aged 55-80 years completed an 8-week RT and dietary intervention at 4 Rhode Island senior centers. Participants performed RT twice-weekly using resistance tubing, dumbbells, and ankle weights. Participants also attended 1 weekly dietary counseling session on a modified Dietary Approaches to Stop Hypertension diet. Outcome measurements included anthropometrics, body composition, and physical function. Results: There were small changes in body mass (-1.0 ± 1.8 kg, P \u3c .001), waist circumference (-5.2 ± 3.8 cm, P \u3c .001), and percent body fat (-0.5 ± 1.4%, P \u3c .001). In addition, significant improvements were observed in knee extensor torque (+7.9 ± 19.1 N-m, P \u3c .001), handgrip strength (+1.2 ± 2.5 kg, P \u3c .001), and 8-foot up-and-go test time (-0.56 ± 0.89 s, P \u3c .001). Conclusion: Community-based RT and dietary modifications can improve body composition, muscle strength, and physical function in overweight and obese older adults. Future investigations should determine if this intervention is effective for long-term changes. © 2012 Human Kinetics, Inc