Novel Daptomycin Combinations against Daptomycin-Nonsusceptible Methicillin-Resistant Staphylococcus aureus in an In Vitro Model of Simulated Endocardial Vegetations

Reduced susceptibility to daptomycin has been reported in patients with infections due to methicillin-resistant Staphylococcus aureus (MRSA). Although infections with daptomycin-nonsusceptible (DNS) MRSA are infrequent, optimal therapy of these strains has not been determined. We investigated the killing effects of novel antibiotic combinations with daptomycin (DAP) against two clinical DNS MRSA isolates (SA-684 and R6003) in a 72-h in vitro pharmacokinetic/pharmacodynamic (PK/PD) model with simulated endocardial vegetations (SEV). Simulated regimens included DAP at 6 mg/kg every 24 h (q24h) alone or in combination with trimethoprim-sulfamethoxazole (TMP/SMX) at 160/800 mg q12h, linezolid (LIN) at 600 mg q12h, cefepime (CEF) at 2 g q12h, and nafcillin (NAF) at 4 g q4h. Bactericidal activity was defined as a ≥3-log10 CFU/g kill. Differences in CFU/g were evaluated between 4 and 72 h by analysis of variance with the Bonferroni post hoc test. DAP MICs were 4 and 2 mg/liter for SA-684 and R6003, respectively. In the PK/PD model, DAP alone was slowly bactericidal, achieving a 3-log10 kill at 24 and 50 h for SA-684 and R6003, respectively. Against SA-684, DAP plus TMP/SMX, CEF, LIN, or NAF was bactericidal at 4, 4, 8, and 8 h, respectively, and maintained this activity for the 72-h study duration. DAP plus TMP/SMX or CEF exhibited superior killing than DAP alone against SA-684 between 4 and 72 h, and overall this was significant (P < 0.05). Against R6003, DAP plus TMP/SMX was bactericidal (8 h) and superior to DAP alone between 8 and 72 h (P < 0.001). The unique combination of DAP plus TMP/SMX was the most effective and rapidly bactericidal regimen against the two isolates tested and may provide a clinical option to treat DNS S. aureus infections.This work was not funded by any external support. M.J.R. has received grant support, consulted for, or provided lectures for Astellas, Cubist, Forrest, Ortho-McNeil, and Pfizer

Impact of Dose De-Escalation and Escalation on Daptomycin’s Pharmacodynamics against Clinical Methicillin-Resistant Staphylococcus aureus Isolates in an In Vitro Model

De-escalation and escalation therapeutic strategies are commonly employed by clinicians on the basis of susceptibility results and patient response. Since no in vitro or in vivo data are currently available to support one strategy over the other for daptomycin, we attempted to evaluate the effects of dose escalation and de-escalation on daptomycin activity against methicillin-resistant Staphylococcus aureus (MRSA) isolates using an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model with simulated endocardial vegetations. Three clinical MRSA isolates, including one heterogeneous vancomycin-intermediate S. aureus (hVISA) isolate and one vancomycin-intermediate S. aureus (VISA) isolate, were exposed to daptomycin at 10 or 6 mg/kg of body weight/day for 8 days using a starting inoculum of 109 CFU/g of vegetations, with dose escalation and de-escalation initiated on the fourth day. Daptomycin MIC values ranged from 0.5 to 1 g/ml. In the PK/PD model, high-dose daptomycin (10 mg/kg/day) and de-escalation simulation (10 to 6 mg/kg/day) appeared to be the most efficient regimens against the three tested isolates, exhibiting the fastest bactericidal activity (4 to 8 h) compared to that of the standard regimen of 6 mg/kg/day and the escalation therapy of 6 to 10 mg/kg/day. The differences in the numbers of CFU/g observed between dose escalation and de-escalation were significant for the hVISA strain, with the de-escalation simulation exhibiting a better killing effect than the escalation simulation (P < 0.024). Although our results need to be carefully considered, the use of high-dose daptomycin up front demonstrated the most efficient activity against the tested isolates. Different therapeutic scenarios including isolates with higher MICs and prolonged drug exposures are warranted to better understand the outcomes of escalation and de-escalation strategies.We thank Debbie Goff and Preeti Pancholi from the Ohio State Medical Center for kindly providing isolate B010-01. This study was funded by a research grant from Cubist Pharmaceuticals. M.J.R. has received grant support, has served as a consultant, or has participated as a speaker for Astellas, Cerexa, Cubist, Forest, Johnson & Johnson, Pfizer, Targanta and Theravance. C.V. and M.E.S. have no potential conflicts to declare

Evaluation of Telavancin Activity versus Daptomycin and Vancomycin against Daptomycin-Nonsusceptible Staphylococcus aureus in an In Vitro Pharmacokinetic/Pharmacodynamic Model

Daptomycin-nonsusceptible (DNS) Staphylococcus aureus strains have been reported over the last several years. Telavancin is a lipoglycopeptide with a dual mechanism of action, as it inhibits peptidoglycan polymerization/cross-linking and disrupts the membrane potential. Three clinical DNS S. aureus strains, CB1814, R6212, and SA-684, were evaluated in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model with simulated endocardial vegetations (starting inoculum, 108.5 CFU/g) for 120 h. Simulated regimens included telavancin at 10 mg/kg every 24 h (q24h; peak, 87.5 mg/liter; t1/2, 7.5 h), daptomycin at 6 mg/kg q24h (peak, 95.7 mg/liter; t1/2, 8 h), and vancomycin at 1 g q12h (peak, 30 mg/liter; t1/2, 6 h). Differences in CFU/g between regimens at 24 through 120 h were evaluated by analysis of variance with a Tukey's post hoc test. Bactericidal activity was defined as a ≥3-log10 CFU/g decrease in colony count from the initial inoculum. MIC values were 1, 0.25, and 0.5 mg/liter (telavancin), 4, 2, and 2 mg/liter (daptomycin), and 2, 2, and 2 mg/liter (vancomycin) for CB1814, R6212, and SA-684, respectively. Telavancin displayed bactericidal activities against R6212 (32 to 120 h; −4.31 log10 CFU/g), SA-684 (56 to 120 h; −3.06 log10 CFU/g), and CB1814 (48 to 120 h; −4.9 log10 CFU/g). Daptomycin displayed initial bactericidal activity followed by regrowth with all three strains. Vancomycin did not exhibit sustained bactericidal activity against any strain. At 120 h, telavancin was significantly better at reducing colony counts than vancomycin against all three tested strains and better than daptomycin against CB1814 (P < 0.05). Telavancin displayed bactericidal activity in vitro against DNS S. aureus isolates.This study was funded by a research grant from Astellas, Deerfield, IL. M.J.R. has received grant support, has served as a consultant, or has participated as a speaker for Astellas, Cerexa, Cubist, Forest, Pfizer, and Theravance. C.V. and M.E.S. have no conflicts to declare

Evaluation of Ceftaroline Activity versus Ceftriaxone against Clinical Isolates of Streptococcus pneumoniae with Various Susceptibilities to Cephalosporins in an In Vitro Pharmacokinetic/Pharmacodynamic Model

Drug resistance in Streptococcus pneumoniae, a frequent pathogen in community-acquired pneumonia, is increasing. Ceftaroline (active metabolite of ceftaroline fosamil) is a broad-spectrum intravenous cephalosporin with activity in vitro against drug-resistant Gram-positive organisms. We investigated ceftaroline at 600 mg every 12 h (q12h) (maximum concentration of the free, unbound drug in serum [fCmax] is 15.2 μg/ml, and half-life [T1/2] is 2.5 h) versus ceftriaxone at 1 g q24h (fCmax = 23 μg/ml, T1/2 = 8 h) against six clinical S. pneumoniae isolates in a one-compartment in vitro pharmacokinetic/pharmacodynamic 96-h model (starting inoculum of 107 CFU/ml). Differences in CFU/ml (at 24 to 96 h) were evaluated by analysis of variance with a Tukey's post hoc test. Bactericidal activity was defined as a ≥3 log10 CFU/ml decrease from the initial inoculum. Ceftaroline MICs were 0.06, 0.015, ≤0.008, 0.25, 0.25, and 0.5 μg/ml, and ceftriaxone MICs were 0.5, 0.25, 0.25, 4, 4, and 8 μg/ml for SP 1477, SP 669, SP 132, SP 211, SP 90, and SP 1466, respectively. Against the ceftaroline- and ceftriaxone-susceptible strain SP 1477, ceftaroline displayed sustained bactericidal activity (3 to 96 h, −5.49 log10 CFU/ml) and was significantly (P ≤ 0.012) better than ceftriaxone (72 to 96 h, −2.03 log10 CFU/ml). Against the ceftriaxone-resistant strains, ceftaroline displayed sustained bactericidal activity at 96 h and was significantly better than ceftriaxone (SP211 [−5.91 log10 CFU/ml, P ≤ 0.002], SP 90 [−5.26 log10 CFU/ml, P ≤ 0.008], and SP1466 [−5.14 log10 CFU/ml, P ≤ 0.042]). Ceftaroline was the more effective drug and displayed sustained bactericidal activity. Ceftaroline fosamil may provide a therapeutic option to treat ceftriaxone-resistant S. pneumoniae infections.This study was funded by a research grant from Forest Laboratories. Scientific Therapeutics Information, Inc. (Springfield, NJ), provided editorial assistance on the manuscript. Funding for editorial assistance was provided by Forest Laboratories, Inc. M.J.R. has received research support from or consulted or participated in speaking for Astellas, Cubist, Forest Laboratories, Pfizer, Rib-X, and Novartis. D.B. is an employee of Cerexa, a wholly owned subsidiary of Forest Laboratories, Inc., and holds stock and stock options in Forest Laboratories, Inc. M.E.S., C.V., and P.W. declare no conflicts of interest

Towards a fair and transparent research participant compensation and reimbursement framework in Viet Nam

Background: Providing compensation for participants in clinical research is well established and whilst international guidelines exist, defining a context specific and fair compensation for participants in low resource settings is challenging due to ethical concerns and the lack of practical, national compensation and reimbursement frameworks. Methods: We reviewed OUCRU (Oxford University Clinical Research Unit) internal reimbursement documentation over a ten-year period and conducted a scoping literature review to expand our knowledge of compensation and reimbursement practices including ethical concerns. We developed a preliminary reimbursement framework that was presented to Community Advisory Boards (CAB) and clinical investigators to assess its applicability, fairness, and transparency. Results: The main topics discussed at the workshops centered on fairness and whether the reimbursements could be perceived as financial incentives. Other decisive factors in the decision making process were altruism and the loss of caregivers’ earnings. Investigators raised the issue of additional burdens, whereas the CAB members were focused on non-monetary elements such as the healthcare quality the patients would receive. All elements discussed were reviewed and where possible, incorporated into the final framework. Conclusion: Our new reimbursement framework provides a consistent, fair and transparent decision-making process and will be implemented across all future OUCRU clinical research in Viet Nam

Pharmacokinetic/pharmacodynamic integration and modelling of florfenicol for the pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida

Pharmacokinetic-pharmacodynamic (PK/PD) integration and modelling were used to predict dosage schedules for florfenicol for two pig pneumonia pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida. Pharmacokinetic data were pooled for two bioequivalent products, pioneer and generic formulations, administered intramuscularly to pigs at a dose rate of 15 mg/kg. Antibacterial potency was determined in vitro as minimum inhibitory concentration (MIC) and Mutant Prevention Concentration in broth and pig serum, for six isolates of each organism. For both organisms and for both serum and broth MICs, average concentration:MIC ratios over 48 h were similar and exceeded 2.5:1 and times greater than MIC exceeded 35 h. From in vitro time-kill curves, PK/PD modelling established serum breakpoint values for the index AUC24h/MIC for three levels of inhibition of growth, bacteriostasis and 3 and 4log10 reductions in bacterial count; means were 25.7, 40.2 and 47.0 h, respectively, for P. multocida and 24.6, 43.8 and 58.6 h for A. pleuropneumoniae. Using these PK and PD data, together with literature MIC distributions, doses for each pathogen were predicted for: (1) bacteriostatic and bactericidal levels of kill; (2) for 50 and 90% target attainment rates (TAR); and (3) for single dosing and daily dosing at steady state. Monte Carlo simulations for 90% TAR predicted single doses to achieve bacteriostatic and bactericidal actions over 48 h of 14.4 and 22.2 mg/kg (P. multocida) and 44.7 and 86.6 mg/kg (A. pleuropneumoniae). For daily doses at steady state, and 90% TAR bacteriostatic and bactericidal actions, dosages of 6.2 and 9.6 mg/kg (P. multocida) and 18.2 and 35.2 mg/kg (A. pleuropneumoniae) were required. PK/PD integration and modelling approaches to dose determination indicate the possibility of tailoring dose to a range of end-points

Sex Steroids Induce Membrane Stress Responses and Virulence Properties in Pseudomonas aeruginosa.

Estrogen, a major female sex steroid hormone, has been shown to promote the selection of mucoid Pseudomonas aeruginosa in the airways of patients with chronic respiratory diseases, including cystic fibrosis. This results in long-term persistence, poorer clinical outcomes, and limited therapeutic options. In this study, we demonstrate that at physiological concentrations, sex steroids, including testosterone and estriol, induce membrane stress responses in P. aeruginosa This is characterized by increased virulence and consequent inflammation and release of proinflammatory outer membrane vesicles promoting in vivo persistence of the bacteria. The steroid-induced P. aeruginosa response correlates with the molecular polarity of the hormones and membrane fluidic properties of the bacteria. This novel mechanism of interaction between sex steroids and P. aeruginosa explicates the reported increased disease severity observed in females with cystic fibrosis and provides evidence for the therapeutic potential of the modulation of sex steroids to achieve better clinical outcomes in patients with hormone-responsive strains.IMPORTANCE Molecular mechanisms by which sex steroids interact with P. aeruginosa to modulate its virulence have yet to be reported. Our work provides the first characterization of a steroid-induced membrane stress mechanism promoting P. aeruginosa virulence, which includes the release of proinflammatory outer membrane vesicles, resulting in inflammation, host tissue damage, and reduced bacterial clearance. We further demonstrate that at nanomolar (physiological) concentrations, male and female sex steroids promote virulence in clinical strains of P. aeruginosa based on their dynamic membrane fluidic properties. This work provides, for the first-time, mechanistic insight to better understand and predict the P. aeruginosa related response to sex steroids and explain the interindividual patient variability observed in respiratory diseases such as cystic fibrosis that are complicated by gender differences and chronic P. aeruginosa infection

Increased prevalence of methicillin-resistant Staphylococcus aureus nasal colonization in household contacts of children with community acquired disease

<p>Abstract</p> <p>Background</p> <p>To measure Methicillin-resistant <it>Staphylococcus aureus </it>(MRSA) nasal colonization prevalence in household contacts of children with current community associated (CA)-MRSA infections (study group) in comparison with a group of household contacts of children without suspected <it>Staphylococcus aureus </it>infection (a control group).</p> <p>Methods</p> <p>This is a cross sectional study. Cultures of the anterior nares were taken. Relatedness of isolated strains was tested using pulse field gel electrophoresis (PFGE).</p> <p>Results</p> <p>The prevalence of MRSA colonization in the study group was significantly higher than in the control group (18/77 (23%) vs 3/77 (3.9%); p ≤ 0.001). The prevalence of SA colonization was 28/77 (36%) in the study group and 16/77 (21%) in the control group (p = 0.032). The prevalence of SA nasal colonization among patients was 6/24 (25%); one with methicillin-susceptible <it>S. aureus </it>(MSSA) and 5 with MRSA. In the study (patient) group, 14/24 (58%) families had at least one household member who was colonized with MRSA compared to 2/29 (6.9%) in the control group (p = 0.001). Of 69 total isolates tested by PFGE, 40 (58%) were related to USA300. Panton-Valetine leukocidin (PVL) genes were detected in 30/52 (58%) tested isolates. Among the families with ≥1 contact colonized with MRSA, similar PFGE profiles were found between the index patient and a contact in 10/14 families.</p> <p>Conclusions</p> <p>Prevalence of asymptomatic nasal carriage of MRSA is higher among household contacts of patients with CA-MRSA disease than control group. Decolonizing such carriers may help prevent recurrent CA-MRSA infections.</p