CEM-101 Activity against Gram-Positive Organisms▿

The in vitro activity of CEM-101, a new fluoroketolide, was determined against Gram-positive organisms with various macrolide susceptibility profiles. Experiments for determination of the MICs and minimum bactericidal concentrations (MBCs), timed killing, single-step and multistep mutation rates, the erythromycin induction of resistance, postantibiotic effect (PAE), and drug interactions were performed for CEM-101; and the results were compared to those obtained with telithromycin, macrolides, and lincosamides. The MBCs of CEM-101 remained lower overall than those of telithromycin, and CEM-101 displayed a 2-fold greater potency than the ketolide. Timed-killing curve testing showed that CEM-101 had greater bactericidal activity than telithromycin (a ≥3-log10-CFU/ml decrease in the initial inoculum at 24 h) against the staphylococcal isolates tested. The propensity of CEM-101 to cause resistance was low, as determined from the rates of resistance determined in single-step mutational studies (<10−8 or 10−9). In multipassaging studies, mutants of two strains (both of which were USA300 isolates) resistant to CEM-101 emerged. That number was comparable to the number resistant to clindamycin but less than the number resistant to telithromycin. Erythromycin induced CEM-101 resistance in Staphylococcus aureus and Streptococcus pneumoniae, similar to telithromycin; however, in seven of eight beta-hemolytic streptococci, CEM-101 resistance induction was not observed. CEM-101 showed a significant concentration- and exposure-dependent PAE against the strains tested, with the values ranging from 2.3 to 6.1 h for Gram-positive organisms (these times were longer than those for telithromycin). No antagonism was found in synergy analyses, with enhanced inhibition being most noted for combinations with CEM-101 and ceftriaxone, gentamicin, and trimethoprim-sulfamethoxazole. Overall, this new antimicrobial agent (CEM-101) showed good antimicrobial characteristics compared with those of the agents in its class and exhibited measured parameter values similar or superior to those of utilized comparators, indicating that CEM-101 warrants further clinical evaluation

Application of Next-Generation Sequencing for Characterization of Surveillance and Clinical Trial Isolates Analysis of the Distribution of β-lactamase Resistance Genes and Lineage Background in the United States

International audienceBackground - Sequencing technologies and techniques have seen remarkable transformation and innovation that have significantly affected sequencing capability. Data analyses have replaced sequencing as the main challenge. This paper provides an overview on applying next-generation sequencing (NGS) and analysis and discusses the benefits and challenges. In addition, this document shows results from using NGS and bioinformatics tools to screen for β-lactamase genes and assess the epidemiological structure of and -causing bloodstream (BSIs) and urinary tract (UTIs) infections in patients hospitalized in the United States during the SENTRY Antimicrobial Surveillance Program for 2016.Methods - A total of 3525 isolates (2751 and 774 ) causing BSIs (n = 892) and UTIs (n = 2633) in hospitalized patients in the United States were included. Isolates were tested for susceptibility by broth microdilution, and those that met a minimum inhibitory concentration (MIC)-based screening criteria had their genomes sequenced and analyzed. Results - A total of 11.6% and 16.1% of causing UTIs and BSIs, respectively, met the MIC-based criteria, whereas 11.0% and 13.7% of isolates causing UTIs and BSIs, respectively, met the criteria. Among , variants (87.6% overall) prevailed (60.5% of CTX-M group 1 and 26.9% of group 9). A total of 60.3% of isolates carried variants (52.7% and 7.6% of groups 1 and 9, respectively). Two (0.6%) and 13 (12.9%) isolates harbored . Among KPC-producing (2 from BSIs and 11 from UTIs), 84.6% (11/13) were ST258 (CC258). Seventeen and 38 unique clonal complexes (CCs) were noted in that caused BSIs and UTIs, respectively, and CC131 (or ST131) was the most common CC among BSI (53.6%) and UTI (58.2%) isolates. Twenty-three and 26 CCs were noted among -causing BSIs and UTIs, respectively. CC258 (28.3%) prevailed in UTI pathogens, whereas CC307 (15.0%) was the most common CC among BSI isolates. Conclusions - This study provides a benchmark for the distribution of β-lactamase genes and the population structure information for the most common species responsible for BSIs and UTIs in US medical centers during the 2016 SENTRY Program

Performance of Fusidic Acid (CEM-102) Susceptibility Testing Reagents: Broth Microdilution, Disk Diffusion, and Etest Methods as Applied to Staphylococcus aureus▿

Fusidic acid (CEM-102) is an established antistaphylococcal agent that has been used in clinical practice for more than 4 decades. The activity of fusidic acid against 778 isolates of Staphylococcus aureus collected from U.S. (53.8% were methicillin-resistant S. aureus [MRSA]) and Canadian (46.5% were MRSA) medical centers was assessed to determine the intermethod accuracy of the Clinical and Laboratory Standards Institute (CLSI) and Etest methods. Broth microdilution MIC results were compared by scattergram analysis to zone diameters around commercially available 5- and 10-μg disks. Acceptable correlation (r = 0.74 to 0.76) was observed for the two disk concentrations, and applying breakpoints of ≤1 μg/ml (≥22 mm) for susceptibility (S) and ≥4 μg/ml (≤19 mm) for resistance (R) provided 99.9% absolute intermethod categorical agreement. Reference CLSI MIC versus Etest MIC results (r = 0.77; 728 strains) showed 55.4% identical results and agreement of 99.7% ± one log2 dilution. The diagnostic susceptibility testing reagents (including Etest) for fusidic acid (CEM-102) performed at an excellent level of intermethod agreement for the proposed breakpoint criteria

Low Prevalence of fks1 Hot Spot 1 Mutations in a Worldwide Collection of Candida Strains▿

We evaluated the prevalence of fks1 hot spot (HS) 1 mutations among 133 Candida strains from six species displaying various caspofungin MIC values (from ≤0.008 to >8 μg/ml). Only 4 (2.9%) strains displayed FKS1 HS1 amino acid substitutions: 1 C. albicans (F641Y) among 32 isolates tested (3.1%), 1 C. glabrata (S645P) among 34 isolates tested (2.9%), and 2 C. tropicalis (F641S) among 12 isolates tested (16.7%). The 4 isolates displaying FKS1 HS1 alterations showed elevated caspofungin MIC results (1 to >8 μg/ml) but lower anidulafungin and micafungin MIC values (0.12 to 4 μg/ml and 0.25 to 4 μg/ml, respectively) in some instances within the wild-type MIC population, as determined using the epidemiologic cutoff values (ECV). Candida krusei, C. parapsilosis, and C. guilliermondii isolates tested showed no FKS1 HS1 alterations regardless of echinocandin MIC result. We additionally analyzed 8 C. albicans and 7 C. glabrata strains for mutations on other HS regions of fks1 and fks2. Three C. glabrata strains showed alterations on FKS2 HS1 (two S645P and one L644W). In general, strains displaying S645P alteration showed higher echinocandin MIC values than strains harboring other mutations. Overall, Candida spp. strains showing caspofungin MIC values within the ECV did not display fks HS mutations. In contrast, strains showing alterations in this region displayed anidulafungin and/or micafungin MIC values within the wild-type population, suggesting that caspofungin could be the most sensitive agent for detection of these resistance mutations. Furthermore, results from this large, geographically diverse Candida spp. collection demonstrated that fks1 HS1 mutations remain uncommon among isolates with various echinocandin MIC levels

Dilution Factor of Quantitative Bacterial Cultures Obtained by Bronchoalveolar Lavage in Patients with Ventilator-Associated Bacterial Pneumonia

Ventilator-associated bacterial pneumonia (VABP) is a difficult therapeutic problem. Considerable controversy exists regarding the optimal chemotherapy for this entity. The recent guidelines of the Infectious Diseases Society of America and the American Thoracic Society recommend a 7-day therapeutic course for VABP based on the balance of no negative impact on all-cause mortality, less resistance emergence, and fewer antibiotic treatment days, counterbalanced with a higher relapse rate for patients whose pathogen is a nonfermenter. The bacterial burden causing an infection has a substantial impact on treatment outcome and resistance selection. We describe the baseline bronchoalveolar lavage (BAL) fluid burden of organisms in suspected VABP patients screened for inclusion in a clinical trial. We measured the urea concentrations in plasma and BAL fluid to provide an index of the dilution of the bacterial and drug concentrations in the lung epithelial lining fluid introduced by the BAL procedure. We were then able to calculate the true bacterial burden as the diluted colony count times the dilution factor. The median dilution factor was 28.7, with the interquartile range (IQR) being 11.9 to 53.2. Median dilution factor-corrected colony counts were 6.18 log10(CFU/ml) [IQR, 5.43 to 6.46 log10(CFU/ml)]. In a subset of patients, repeat BAL on day 5 showed a good stability of the dilution factor. We previously showed that large bacterial burdens reduce or stop bacterial killing by granulocytes. (This study has been registered at ClinicalTrials.gov under registration no. NCT01570192.