Based on the results of this study, we advise laboratories not to trust gradient tests for colistin susceptibility testing and to use broth microdilution methods for this purpose. There are several commercial broth microdilution tests available and in principle they perform well.

The implementation of routine whole-genome sequencing (WGS) promises to transform our ability to monitor the emergence and spread of bacterial pathogens. Here we combined WGS data from 308 invasive Staphylococcus aureus isolates corresponding to a pan-European population snapshot, with epidemiological and resistance data. Geospatial visualization of the data is made possible by a generic software tool designed for public health purposes that is available at the project URL (http://www.microreact.org/project/EkUvg9uY?tt=rc). Our analysis demonstrates that high-risk clones can be identified on the basis of population level properties such as clonal relatedness, abundance, and spatial structuring and by inferring virulence and resistance properties on the basis of gene content. We also show that in silico predictions of antibiotic resistance profiles are at least as reliable as phenotypic testing. We argue that this work provides a comprehensive road map illustrating the three vital components for future molecular epidemiological surveillance: (i) large-scale structured surveys, (ii) WGS, and (iii) community-oriented database infrastructure and analysis tools.

IntroductionThe objective of this study was to provide an update on the resistance of Escherichia coli in women with acute uncomplicated urinary tract infections (UTIs) in France, Germany, Spain, Sweden, and the United Kingdom (UK) to mecillinam [amdinocillin (United States Adopted Name)], amoxicillin–clavulanic acid, cefadroxil, nitrofurantoin, ciprofloxacin, and trimethoprim, and to compare the results with resistance in the ECO.SENS I and II surveys in 2000 and 2008, respectively.MethodsThe susceptibility of E. coli in France (166 isolates), Germany (133 isolates), Spain (169 isolates), Sweden (137 isolates), and the UK (124 isolates) was determined by disc diffusion according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints and methodology. Resistance rates were compared using Fisher’s exact test, 2-tailed, with P < 0.05 indicating statistical significance.ResultsSince 2000, there has been a significant increase in resistance to cefadroxil in Germany (1% to 12%) and Spain (3% to 8%), to ciprofloxacin in Germany (2% to 21%), Spain (15% to 31%), Sweden (0% to 7%), and the UK (1% to 15%), to trimethoprim in Germany (23% to 37%), Spain (25% to 37%), Sweden (9% to 17%), and the UK (13% to 46%), to mecillinam in Spain (1% to 6.5%), and to nitrofurantoin in the UK (0% to 6%); there was also a significant decrease in resistance to nitrofurantoin in Spain (4% to 0%). Since 2008, there has been a significant increase in resistance to ciprofloxacin in Sweden (3% to 15%) and the UK (1% to 15%), and to trimethoprim (13% to 46%) and nitrofurantoin (0% to 6%) in the UK.ConclusionE. coli isolates from women with acute uncomplicated UTIs have increasing antimicrobial resistance, particularly to ciprofloxacin and trimethoprim. However, resistance to mecillinam and nitrofurantoin mostly remains low.FundingLEO Pharma.Electronic supplementary materialThe online version of this article (doi:10.1007/s40121-015-0095-5) contains supplementary material, which is available to authorized users.

c Fluoroquinolones (FQs) are among the drugs of choice for treatment of Salmonella infections. However, fluoroquinolone resistance is increasing in Salmonella due to chromosomal mutations in the quinolone resistance-determining regions (QRDRs) of the topoisomerase genes gyrA, gyrB, parC, and parE and/or plasmid-mediated quinolone resistance (PMQR) mechanisms including qnr variants, aac(6=)-Ib-cr, qepA, and oqxAB. Some of these mutations cause only subtle increases in the MIC, i.e., MICs ranging from 0.12 to 0.25 mg/liter for ciprofloxacin (just above the wild-type MIC of <0.06 mg/liter). These isolates are difficult to detect with standard ciprofloxacin disk diffusion, and plasmid-mediated resistance, such as qnr, is often not detected by the nalidixic acid screen test. We evaluated 16 quinolone/fluoroquinolone disks for their ability to detect low-level-resistant Salmonella enterica isolates that are not serotype Typhi. A total of 153 Salmonella isolates characterized for the presence (n ‫؍‬ 104) or absence (n ‫؍‬ 49) of gyrA and/or parC topoisomerase mutations, qnrA, qnrB, qnrD, qnrS, aac(6=)-Ib-cr, or qepA genes were investigated. All isolates were MIC tested by broth microdilution against ciprofloxacin, levofloxacin, and ofloxacin and by disk diffusion using EUCAST or CLSI methodology. MIC determination correctly categorized all isolates as either wild-type isolates (MIC of <0.06 mg/liter and absence of resistance genes) or non-wild-type isolates (MIC of >0.06 mg/liter and presence of a resistance gene). Disk diffusion using these antibiotics and nalidixic acid failed to detect some low-level-resistant isolates, whereas the 5-g pefloxacin disk correctly identified all resistant isolates. However, pefloxacin will not detect isolates having aac(6=)-Ib-cr as the only resistance determinant. The pefloxacin disk assay was approved and implemented by EUCAST (in 2014) and CLSI (in 2015).

Objectives: Increasing use of improved culture techniques and sensitive nucleic acid amplification assays have resulted in recognition of Kingella kingae as an important cause of invasive infections in young children, especially in septic arthritis, osteomyelitis, bacteraemia, and endocarditis. In 2016, EUCAST established clinical MIC breakpoints for K. kingae (published in EUCAST Clinical Breakpoint Tables v 7.0, 2017). The present study was carried out to produce MIC-zone diameter correlations for K. kingae on an international collection of isolates, with the aim of suggesting zone diameter breakpoints corresponding to the clinical MIC breakpoints. Methods: Antimicrobial susceptibility testing was performed for 18 clinically relevant agents on a collection of 159 clinical isolates of K. kingae. Broth microdilution MIC determination and disk diffusion were performed according to EUCAST recommendations for fastidious organisms. Results: The correlation between MICs and zone diameters was good for all agents with EUCAST breakpoints for K. kingae. b-lactamase was detected in 41 isolates (26%) and these isolates were resistant to aminopenicillins. These isolates were also resistant to trimethoprim-sulfamethoxazole. Resistance to tetracyclines was detected in 8% of all isolates. All resistant isolates were correctly categorized for these agents with the proposed zone diameter breakpoints. One isolate, resistant to erythromycin but susceptible to other macrolides, was categorized as susceptible with erythromycin disk diffusion. No resistance was detected for the cephalosporins, carbapenems, and fluoroquinolones tested. Conclusion: Based on the results in this study, zone diameter breakpoints for K. kingae calibrated to EUCAST clinical MIC breakpoints were proposed and approved by EUCAST.