In Vitro Evaluation of Biofilm Dispersal as a Therapeutic Strategy To Restore Antimicrobial Efficacy.

As a proof-of-concept study, the direct impact of biofilm dispersal on the in vitro efficacy of imipenem and tobramycin was evaluated against 3-day-old biofilms of Pseudomonas aeruginosa Arabinose induction of biofilm dispersal via activation of the phosphodiesterase YhjH in the P. aeruginosa engineered strain PAO1/p BAD -yhjH resulted in increased antimicrobial efficacy and synergy of the imipenem-tobramycin combination. These results support the use of biofilm dispersal to enhance antimicrobial efficacy in the treatment of biofilm-associated infections, representing a promising therapeutic strategy.

In Vitro and In Vivo Efficacy of an LpxC Inhibitor, CHIR-090, Alone or Combined with Colistin against Pseudomonas aeruginosa Biofilm.

With the rapid spread of antimicrobial resistance in Gram-negative pathogens, biofilm-associated infections are increasingly harder to treat and combination therapy with colistin has become one of the most efficient therapeutic strategies. Our study aimed to evaluate the potential for the synergy of colistin combined with CHIR-090, a potent LpxC inhibitor, against in vitro and in vivoPseudomonas aeruginosa biofilms. Four P. aeruginosa isolates with various colistin susceptibilities were chosen for evaluation. The tested isolates of P. aeruginosa exhibited MIC values ranging from 1 to 64 and 0.0625 to 0.5 µg/ml for colistin and CHIR-090, respectively. Against 24-h static biofilms, minimum biofilm eradication concentration values ranged from 256 to 512 and 8 to >128 µg/ml for colistin and CHIR-090, respectively. Interestingly, subinhibitory concentrations of CHIR-090 contributed to the eradication of subpopulations of P. aeruginosa with the highest colistin MIC values. The combination of colistin and CHIR-090 at subinhibitory concentrations demonstrated synergistic activity both in vivo and in vitro and prevented the formation of colistin-tolerant subpopulations in in vitro biofilms. In summary, our study highlights the in vivo and in vitro synergistic activity of the colistin and CHIR-090 combination against both colistin-susceptible and -nonsusceptible P. aeruginosa biofilms. Further studies are warranted to investigate the clinical relevance of the combination of these two antimicrobials and outline the underlying mechanism for their synergistic action.

Alternative mutational pathways to intermediate resistance to vancomycin in methicillin-resistant Staphylococcus aureus.

BACKGROUND: We used 2 in vitro experimental systems to compare phenotypic and genotypic changes that accompany selection of mutants of methicillin-resistant Staphylococcus aureus (MRSA) strain JH1 with low-level vancomycin resistance similar to the type found in vancomycin-intermediate S. aureus (VISA). METHODS: The previously described MRSA strain JH1 and its vancomycin-intermediate mutant derivative JH2, both of which were recovered from a patient undergoing vancomycin chemotherapy, were used in this study. Mutants of JH1 were selected in vitro by means of a pharmacokinetic/pharmacodynamic (PK/PD) model of simulated endocardial vegetations (SEVs) and by exposure to vancomycin in laboratory growth medium. Phenotypic abnormalities of JH1 mutants generated by each in vitro experimental system were compared to those of JH2, and whole genomes of 2 in vitro JH1 mutants were sequenced to identify mutations that may be associated with an increased vancomycin minimum inhibitory concentration. RESULTS: JH1R1 was selected from the PK/PD model, and JH1R2 was selected in laboratory growth medium. Both mutants displayed reduced vancomycin and daptomycin susceptibility and phenotypic alterations (eg, thicker cell walls and abnormal autolysis) that are typical of in vivo VISA mutants. Genome sequencing of JH1R1 identified point mutations in 4 genes, all of which were different from the mutations described in JH2, including 1 mutation in yycG, a component of the WalKR sensory regulatory system. Sequencing of the JH1R2 genome identified mutations in 7 genes, including 2 in rpoB. CONCLUSION: Our findings indicate that JH1 is able to develop VISA-type resistance through several alternative genetic pathways.

Evaluation of vancomycin susceptibility testing for methicillin-resistant Staphylococcus aureus: comparison of Etest and three automated testing methods.

We evaluated the ability of four commercial MIC testing systems (MicroScan, Vitek 2, Phoenix, and Etest) to detect vancomycin MIC values of ≤1 to ≥2 in 200 methicillin-resistant Staphylococcus aureus (MRSA) strains compared to the Clinical and Laboratory Standards Institute broth microdilution (BMD) reference methods. Compared to the BMD method, absolute agreement (0 ± dilution) was highest for the Phoenix system (66.2%) and the MicroScan turbidity method (61.8%), followed by the Vitek 2 system (54.3%). The Etest produced MIC values 1 to 2 dilutions higher than those produced by the BMD method (36.7% agreement). Of interest, the MicroScan system (prompt method) was more likely to overcall an MIC value of 1 mg/liter (74.1%), whereas the Phoenix (76%) and Vitek 2 (20%) systems had a tendency to undercall an MIC of 2 mg/liter. The ability to correctly identify vancomycin MIC values of 1 and 2 has clinical implications and requires further evaluation.

In vitro synergy of colistin combinations against colistin-resistant Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae isolates.

Colistin resistance, although uncommon, is increasingly being reported among Gram-negative clinical pathogens, and an understanding of its impact on the activity of antimicrobials is now evolving. We evaluated the potential for synergy of colistin plus trimethoprim, trimethoprim-sulfamethoxazole (1/19 ratio), or vancomycin against 12 isolates of Acinetobacter baumannii (n = 4), Pseudomonas aeruginosa (n = 4), and Klebsiella pneumoniae (n = 4). The strains included six multidrug-resistant clinical isolates, K. pneumoniae ATCC 700603, A. baumannii ATCC 19606, P. aeruginosa ATCC 27853, and their colistin-resistant derivatives (KPm1, ABm1, and PAm1, respectively). Antimicrobial susceptibilities were assessed by broth microdilution and population analysis profiles. The potential for synergy of colistin combinations was evaluated using a checkerboard assay, as well as static time-kill experiments at 0.5× and 0.25× MIC. The MIC ranges of vancomycin, trimethoprim, and trimethoprim-sulfamethoxazole (1/19) were ≥128, 4 to ≥128, and 2/38 to >128/2,432 µg/ml, respectively. Colistin resistance demonstrated little impact on vancomycin, trimethoprim, or trimethoprim-sulfamethoxazole MIC values. Isolates with subpopulations heterogeneously resistant to colistin were observed to various degrees in all tested isolates. In time-kill assays, all tested combinations were synergistic against KPm1 at 0.25× MIC and 0.5× MIC and ABm1 and PAm1 at 0.5× MIC. In contrast, none of the tested combinations demonstrated synergy against any colistin-susceptible P. aeruginosa isolates and clinical strains of K. pneumoniae isolates. Only colistin plus trimethoprim or trimethoprim-sulfamethoxazole was synergistic and bactericidal at 0.5× MIC against K. pneumoniae ATCC 700603. Colistin resistance seems to promote the in vitro activity of unconventional colistin combinations. Additional experiments are warranted to understand the clinical significance of these observations.

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, 10(8.5) CFU/g) for 120 h. Simulated regimens included telavancin at 10 mg/kg every 24 h (q24h; peak, 87.5 mg/liter; t(1/2), 7.5 h), daptomycin at 6 mg/kg q24h (peak, 95.7 mg/liter; t(1/2), 8 h), and vancomycin at 1 g q12h (peak, 30 mg/liter; t(1/2), 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-log(10) 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 log(10) CFU/g), SA-684 (56 to 120 h; -3.06 log(10) CFU/g), and CB1814 (48 to 120 h; -4.9 log(10) 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.

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 [fC(max)] is 15.2 µg/ml, and half-life [T(1/2)] is 2.5 h) versus ceftriaxone at 1 g q24h (fC(max) = 23 µg/ml, T(1/2) = 8 h) against six clinical S. pneumoniae isolates in a one-compartment in vitro pharmacokinetic/pharmacodynamic 96-h model (starting inoculum of 10(7) 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 log(10) 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 log(10) CFU/ml) and was significantly (P ≤ 0.012) better than ceftriaxone (72 to 96 h, -2.03 log(10) CFU/ml). Against the ceftriaxone-resistant strains, ceftaroline displayed sustained bactericidal activity at 96 h and was significantly better than ceftriaxone (SP211 [-5.91 log(10) CFU/ml, P ≤ 0.002], SP 90 [-5.26 log(10) CFU/ml, P ≤ 0.008], and SP1466 [-5.14 log(10) 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.

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 ∼10(9) CFU/g of vegetations, with dose escalation and de-escalation initiated on the fourth day. Daptomycin MIC values ranged from 0.5 to 1 µg/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.

Evaluation of ceftaroline activity versus daptomycin (DAP) against DAP-nonsusceptible methicillin-resistant Staphylococcus aureus strains in an in vitro pharmacokinetic/pharmacodynamic model.

The objective of this study was to investigate the potential role of ceftaroline, a new broad-spectrum cephalosporin, as a therapeutic option for the treatment of daptomycin-nonsusceptible (DNS) methicillin-resistant Staphylococcus aureus (MRSA) infections. Four clinical DNS MRSA strains, R5717, R5563, R5996 (heteroresistant vancomycin-intermediate S. aureus) and R5995 (vancomycin-intermediate S. aureus) were evaluated in a two-compartment hollow-fiber in vitro pharmacokinetic/pharmacodynamic model at a starting inoculum of 10(7) CFU/ml for 96 h. Simulated regimens were ceftaroline at 600 mg every 12 h (q12h) (maximum free-drug concentration [fC(max)], 15.2 µg/ml; serum half-life [t(1/2)], 2.3 h), daptomycin at 6 mg/kg q24h (fC(max), 7.9 µg/ml; t(1/2), 8 h), and daptomycin at 10 mg/kg q24h (fC(max), 15.2 µg/ml; t(1/2), 8 h). Differences in CFU/ml between 24 and 96 h were evaluated by analysis of variance with Tukey's post-hoc test. Bactericidal activity was defined as a ≥3-log(10) CFU/ml decrease in the colony count from the initial inoculum. The ceftaroline MIC values were 0.25, 0.5, 0.5, and 0.5 µg/ml, and the daptomycin MIC values were 2, 2, 4, and 4 µg/ml for R5717, R5563, R5996, and R5995, respectively. Ceftaroline displayed sustained bactericidal activity against 3 of the 4 strains at 96 h (R5717, -3.1 log(10) CFU/ml; R5563, -2.5 log(10) CFU/ml; R5996, -5.77 log(10) CFU/ml; R5995, -6.38 log(10) CFU/ml). Regrowth occurred during the daptomycin at 6-mg/kg q24h regimen (4 strains) and the daptomycin at 10-mg/kg q24h regimen (3 strains). At 96 h, ceftaroline was significantly more active, resulting in CFU/ml counts lower than those obtained with daptomycin at 6 mg/kg q24h (4 strains, P ≤ 0.008) and daptomycin at 10 mg/kg q24 h (3 strains, P ≤ 0.001). Isolates with increased MIC values for daptomycin (all 4 strains) but not for ceftaroline were recovered. Ceftaroline was effective against the 4 isolates tested and may provide a clinical option for the treatment of DNS MRSA infections.

Characterizing vancomycin-resistant Enterococcus strains with various mechanisms of daptomycin resistance developed in an in vitro pharmacokinetic/pharmacodynamic model.

Two daptomycin (DAP) regimens were evaluated in a pharmacokinetic/pharmacodynamic (PK/PD) model, and the mutants recovered were examined for changes in phenotypic characteristics. Three Enterococcus faecium strains (vancomycin-resistant Enterococcus [VRE] ATCC 51559, VRE 12311, and VRE SF 12047) were utilized in a 7-day, 1-compartment in vitro PK/PD model. The simulated dosing regimens were DAP at 6 mg/kg/day (free C(max) [fC(max)] = 7.9 µg/ml, half-life [t(1/2)] = 8 h) and DAP at 10 mg/kg/day (fC(max) = 13.17 µg/ml, t(1/2) = 8 h). Samples were plated daily on Mueller-Hinton agar containing DAP at 16 µg/ml and 50 mg/liter Ca(2+) to assess the emergence of DAP resistance. For each strain, the mutant with the highest DAP MIC was then evaluated for changes in relative surface charge, cell wall thickness, and cytoplasmic membrane depolarization induced by DAP. The initial DAP MICs were 4 µg/ml for all 3 strains. A dose-dependent response and regrowth were observed for DAP 6 mg/kg/day and DAP 10 mg/kg/day against all 3 strains. Mutants of VRE ATCC 51559 (MIC = 128 and 64 µg/ml) and VRE 12311 (MIC = 256 and 32 µg/ml) were recovered from the DAP 6 mg and DAP 10 mg regimen, respectively. For VRE SF 12047, a mutant (MIC = 64 µg/ml) was recovered from the DAP 6 mg model. All mutants displayed an increase in relative surface charge compared to those of their respective parent strains. The DAP-resistant mutants displayed a 43 to 58% increase in cell wall thickness (P < 0.0001), while DAP membrane depolarization decreased by 53 to 65% compared to that of the susceptible strains. VRE with DAP resistance displayed increased surface charge, increased cell wall thickness, and decreased depolarization induced by DAP, consistent with previous observations in Staphylococcus aureus with reduced DAP susceptibility. Further characterization of DAP-resistant VRE is warranted.

Pseudomonas aeruginosa in bronchiectasis: infection, inflammation, and therapies.

Introduction: Bronchiectasis is a chronic endobronchial suppurative disease characterized by irreversibly dilated bronchi damaged by repeated polymicrobial infections and predominantly, neutrophilic airway inflammation. Some consider bronchiectasis a syndromic consequence of several different causes whilst others view it as an individual disease entity. In most patients, identifying an underlying cause remains challenging. The acquisition and colonization of affected airways by Pseudomonas aeruginosa represent a critical and adverse clinical consequence for its progression and management.Areas covered: In this review, we outline clinical and pre-clinical peer-reviewed research published in the last 5 years, focusing on the pathogenesis of bronchiectasis and the role of P. aeruginosa and its virulence in shaping host inflammatory and immune responses in the airway. We further detail its role in airway infection, the lung microbiome, and address therapeutic options in bronchiectasis.Expert opinion:P. aeruginosa represents a key pulmonary pathogen in bronchiectasis that causes acute and/or chronic airway infection. Eradication can prevent adverse clinical consequence and/or disease progression. Novel therapeutic strategies are emerging and include combination-based approaches. Addressing airway infection caused by P. aeruginosa in bronchiectasis is necessary to prevent airway damage, loss of lung function and exacerbations, all of which contribute to adverse clinical outcome.

Development of a Good Clinical Practice inspection checklist to assess clinical trial sites in Vietnam.

BACKGROUND: Assessing the capacity of a healthcare institution to conduct and manage clinical research studies is challenging, especially in developing countries where resources are limited. The objective of this study was to develop a practical and transparent tool for the Vietnam Ministry of Health (MOH) to assess institutions' capacity to lead clinical trials in line with local and international regulations. METHODS: We reviewed the literature, relevant official international and national guidelines, regulations and checklists for clinical sites' assessment to identify key indicators of clinical research capacity. We developed a Good Clinical Practice (GCP) inspection checklist consisting of a questionnaire with 30 key criteria, including 16 core criteria and 14 recommended criteria, related to four central aspects of clinical research management (ie, governance, operations, infrastructures and human resources). Following a detailed review and assessment by a panel of experts, sponsors and academic investigators, we assessed the checklist's applicability in a pilot study involving 10 sites with various clinical research experiences. RESULTS: Independently of their clinical research experience, all participating institutions fulfilled most of the core criteria. In contrast, a significant variability was observed in the compliance to recommended capacity criteria, especially those related to governance (certifications and reporting) as well as operations (existence of a clinical research coordination unit or electronic trial management system). CONCLUSIONS: A GCP inspection checklist was successfully developed to support the MOH in the assessment of institutions' capacity to conduct clinical research. Additional efforts from all stakeholders are now warranted to provide local sites with sustainable capacity development resources that will further build up and harmonise Vietnamese clinical research settings.

Population Pharmacokinetics and Dose Optimization of Ceftazidime and Imipenem in Patients with Acute Exacerbations of Chronic Obstructive Pulmonary Disease.

BACKGROUND: Ceftazidime and imipenem have been increasingly used to treat Acute Exacerbations of Chronic Obstructive Pulmonary Disease (AECOPD) due to their extended-spectrum covering Pseudomonas aeruginosa. This study aims to describe the population pharmacokinetic (PK) and pharmacodynamic (PD) target attainment for ceftazidime and imipenem in patients with AECOPD. METHODS: We conducted a prospective PK study at Bach Mai Hospital (Viet Nam). A total of 50 (ceftazidime) and 44 (imipenem) patients with AECOPD were enrolled. Population PK analysis was performed using Monolix 2019R1 and Monte Carlo simulations were conducted to determine the optimal dose regimen with respect to the attainment of 60% and 40% fT>MIC for ceftazidime and imipenem, respectively. A dosing algorithm was developed to identify optimal treatment doses. RESULTS: Ceftazidime and imipenem PK was best described by a one-compartment population model with a volume of distribution and clearance of 23.7 L and 8.74 L/h for ceftazidime and 15.1 L and 7.88 L/h for imipenem, respectively. Cockcroft-Gault creatinine clearance represented a significant covariate affecting the clearance of both drugs. Increased doses with prolonged infusion were found to cover pathogens with reduced susceptibility. CONCLUSIONS: This study describes a novel and versatile three-level dosing algorithm based on patients' renal function and characteristic of the infective pathogen to explore ceftazidime and imipenem optimal regimen for AECOPD.

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-log(10) 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-log(10) 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.

Activities of high-dose daptomycin, vancomycin, and moxifloxacin alone or in combination with clarithromycin or rifampin in a novel in vitro model of Staphylococcus aureus biofilm.

Biofilm formation is an important virulence factor that allows bacteria to resist host responses and antibacterial agents. The aim of the study was to assess the in vitro activities of several antimicrobials alone or in combination against two Staphylococcus aureus isolates in a novel pharmacokinetic/pharmacodynamic (PK/PD) model of biofilm for 3 days. One methicillin-susceptible S. aureus strain (SH1000) and one methicillin-resistant S. aureus strain (N315) were evaluated in a modified biofilm reactor with polystyrene coupons. Simulated regimens included vancomycin (VAN) plus rifampin (RIF), moxifloxacin (MOX), and high doses (10 mg/kg of body weight/day) of daptomycin (DAP) alone or combined with RIF or clarithromycin (CLA). Against viable planktonic bacteria (PB) and biofilm-embedded bacteria (BB) of SH1000, neither DAP nor MOX alone was bactericidal. In contrast, the combination of DAP or MOX with CLA significantly increased the activity of the two agents against both PB and BB (P < 0.01), and DAP plus CLA reached the limit of detection at 72 h. Against PB of N315, DAP alone briefly achieved bactericidal activity at 24 h, whereas sustained bactericidal activity was observed at 32 h with VAN plus RIF. Overall, only a minimal reduction was observed with both regimens against BB (<2.8 log(10) CFU/ml). Finally, the combination of DAP and RIF was bactericidal against both PB and BB, achieving the limit of detection at 72 h. In conclusion, we developed a novel in vitro PK/PD model to assess the activities of antimicrobials against mature bacterial biofilm. Combinations of DAP or MOX with CLA were the most effective regimens and may represent promising options to treat persistent infections caused by S. aureus biofilms.

In vitro activity of the new multivalent glycopeptide-cephalosporin antibiotic TD-1792 against vancomycin-nonsusceptible Staphylococcus isolates.

TD-1792 is a glycopeptide-cephalosporin heterodimer antibiotic with activity against a broad spectrum of gram-positive pathogens that includes methicillin-susceptible and -resistant Staphylococcus aureus. The objective of the present study was to evaluate the in vitro activity of TD-1792 against a collection of clinical isolates of vancomycin-intermediate Staphylococcus spp. (VISS), heteroresistant VISS (hVISS), and vancomycin-resistant S. aureus (VRSA). The TD-1792, vancomycin, daptomycin, linezolid, and quinupristin-dalfopristin MICs and minimum bactericidal concentrations (MBCs) were determined for 50 VISS/hVISS isolates and 3 VRSA isolates. Time-kill experiments (TKs) were then performed over 24 h with two vancomycin-intermediate S. aureus strains and two VRSA strains, using each agent at multiples of the MIC. TD-1792 and daptomycin were also evaluated in the presence and absence of 50% human serum to determine the effects of the proteins on their activities. Most of the VISS/hVISS isolates were susceptible to all agents except vancomycin. TD-1792 exhibited the lowest MIC values (MIC(90) = 0.125 microg/ml), followed by quinupristin-dalfopristin and daptomycin (MIC(90) = 1 microg/ml) and then linezolid (MIC(90) = 2 microg/ml). The presence of serum resulted in a 2- to 8-fold increase in the TD-1792 and daptomycin MIC values. In TKs, QD demonstrated bactericidal activity at multiples of the MIC that simulated therapeutic levels, whereas linezolid was only bacteriostatic. Both TD-1792 and daptomycin demonstrated rapid bactericidal activities against all isolates tested. The presence of proteins had only a minimal impact on the activity of TD-1792 in TKs. TD-1792 exhibited significant in vitro activity against multidrug-resistant Staphylococcus isolates and represents a promising candidate for the treatment of infections caused by gram-positive organisms.

Towards a fair and transparent research participant compensation and reimbursement framework in Vietnam.

BACKGROUND: Providing compensation for participants in clinical research is well established and while 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 Oxford University Clinical Research Unit (OUCRU) internal reimbursement documentation over a 10-y 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 Vietnam.

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.

In vitro activity of ceftaroline against methicillin-resistant Staphylococcus aureus and heterogeneous vancomycin-intermediate S. aureus in a hollow fiber model.

Ceftaroline is a broad-spectrum injectable cephalosporin exhibiting bactericidal activity against a variety of bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Using a two-compartment in vitro pharmacokinetic/pharmacodynamic (PK/PD) model, we evaluated the activity of ceftaroline at 600 mg every 8 h (q8h) and q12h in comparison with that of vancomycin at 1,000 mg q12h over a 72-h time period against six clinical MRSA isolates, including two heterogeneous vancomycin-intermediate S. aureus (hVISA) isolates. The MIC and minimum bactericidal concentration ranged between 0.125 to 2 and 0.5 to 2 microg/ml for ceftaroline and vancomycin, respectively. In the PK/PD model, ceftaroline was superior to vancomycin against all isolates (P < 0.05), except one to which it was equivalent. No difference in activity was observed between both q8 and q12h dosing regimens of ceftaroline. Bacterial regrowth was observed after 32 h for two isolates treated with ceftaroline. This regrowth was uncorrelated to resistance, instability of the drug, or tolerance. However, subpopulations with higher MICs to ceftaroline were found by population analysis for these two isolates. Finally, and in contrast to ceftaroline, MIC elevations up to 8 to 12 microg/ml were observed with vancomycin for the hVISA isolates. In conclusion, in addition to a lower potential to select resistant mutants, ceftaroline demonstrated activity equal to or greater than vancomycin against MRSA isolates. Although further in vitro and in vivo investigations are warranted, ceftaroline appears to be a promising alternative for the treatment of MRSA infections.

Activity of telavancin against Staphylococcus aureus strains with various vancomycin susceptibilities in an in vitro pharmacokinetic/pharmacodynamic model with simulated endocardial vegetations.

We investigated the activity of telavancin, a novel lipoglycopeptide, alone and combined with gentamicin or rifampin (rifampicin) against strains of Staphylococcus aureus with various vancomycin susceptibilities. Strains tested included methicillin (meticillin)-resistant S. aureus (MRSA) 494, methicillin-sensitive S. aureus (MSSA) 1199, heteroresistant glycopeptide-intermediate S. aureus (hGISA) 1629, which was confirmed by a population analysis profile, and glycopeptide-intermediate S. aureus (GISA) NJ 992. Regimens of 10 mg/kg telavancin daily and 1 g vancomycin every 12 h were investigated alone and combined with 5 mg/kg gentamicin daily or 300 mg rifampin every 8 h in an in vitro model with simulated endocardial vegetations over 96 h. Telavancin demonstrated significantly greater killing than did vancomycin (P < 0.01) for all isolates except MRSA 494 (P = 0.07). Telavancin absolute reductions, in log(10) CFU/g, at 96 h were 2.8 +/- 0.5 for MRSA 494, 2.8 +/- 0.3 for MSSA 1199, 4.2 +/- 0.2 for hGISA 1629, and 4.1 +/- 0.3 for GISA NJ 992. Combinations of telavancin with gentamicin significantly enhanced killing compared to telavancin alone against all isolates (P < 0.001) except MRSA 494 (P = 0.176). This enhancement was most evident against hGISA 1629, where killing to the level of detection (2 log(10) CFU/g) was achieved at 48 h (P < 0.001). The addition of rifampin to telavancin resulted in significant (P < 0.001) enhancement of killing against only MSSA 1199. No changes in telavancin susceptibilities were observed. These results suggest that telavancin may have therapeutic potential, especially against strains with reduced susceptibility to vancomycin. Combination therapy, particularly with gentamicin, may improve bacterial killing against certain strains.