Does Sample Size, Sampling Strategy, or Handling of Concentrations Below the Lower Limit of Quantification Matter When Externally Evaluating Population Pharmacokinetic Models?

BACKGROUND AND OBJECTIVES: Precision dosing requires selecting the appropriate population pharmacokinetic model, which can be assessed through external evaluations (EEs). The lack of understanding of how different study design factors influence EE study outcomes makes it challenging to select the most suitable model for clinical use. This study aimed to evaluate the impact of sample size, sampling strategy, and handling of concentrations below the lower limit of quantification (BLQ) on the outcomes of EE for four population pharmacokinetic models using vancomycin and tobramycin as examples. METHODS: Three virtual patient populations undergoing vancomycin or tobramycin therapy were simulated with varying sample size and sampling scenarios. The three approaches used to handle BLQ data were to (1) discard them, (2) impute them as LLOQ/2, or (3) use a likelihood-based approach. EEs were performed with NONMEM and R. RESULTS: Sample size did not have an important impact on the EE results for a given scenario. Increasing the number of samples per patient did not improve predictive performance for two out of the three evaluated models. Evaluating a model developed with rich sampling did not result in better performance than those developed with regular therapeutic drug monitoring. A likelihood-based method to handle BLQ samples impacted the outcomes of the EE with lower bias for predicted troughs. CONCLUSIONS: This study suggests that a large sample size may not be necessary for an EE study, and models selected based on TDM may be more generalizable. The study highlights the need for guidelines for EE of population pharmacokinetic models for clinical use.

Efficacy of adjunctive inhaled colistin and tobramycin for ventilator-associated pneumonia: systematic review and meta-analysis.

INTRODUCTION: Ventilator-associated pneumonia (VAP) presents a significant challenge in intensive care units (ICUs). Nebulized antibiotics, particularly colistin and tobramycin, are commonly prescribed for VAP patients. However, the appropriateness of using inhaled antibiotics for VAP remains a subject of debate among experts. This study aims to provide updated insights on the efficacy of adjunctive inhaled colistin and tobramycin through a comprehensive systematic review and meta-analysis. METHODS: A thorough search was conducted in MEDLINE, EMBASE, LILACS, COCHRANE Central, and clinical trials databases ( www. CLINICALTRIALS: gov ) from inception to June 2023. Randomized controlled trials (RCTs) meeting specific inclusion criteria were selected for analysis. These criteria included mechanically ventilated patients diagnosed with VAP, intervention with inhaled Colistin and Tobramycin compared to intravenous antibiotics, and reported outcomes such as clinical cure, microbiological eradication, mortality, or adverse events. RESULTS: The initial search yielded 106 records, from which only seven RCTs fulfilled the predefined inclusion criteria. The meta-analysis revealed a higher likelihood of achieving both clinical and microbiological cure in the groups receiving tobramycin or colistin compared to the control group. The relative risk (RR) for clinical cure was 1.23 (95% CI: 1.04, 1.45), and for microbiological cure, it was 1.64 (95% CI: 1.31, 2.06). However, there were no significant differences in mortality or the probability of adverse events between the groups. CONCLUSION: Adjunctive inhaled tobramycin or colistin may have a positive impact on the clinical and microbiological cure rates of VAP. However, the overall quality of evidence is low, indicating a high level of uncertainty. These findings underscore the need for further rigorous and well-designed studies to enhance the quality of evidence and provide more robust guidance for clinical decision-making in the management of VAP.

Impact of pH modification of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus).

BACKGROUND: Commercial tobramycin ophthalmic solution is frequently used empirically to treat ocular disorders in equines, despite being primarily formulated for use in humans. It has been noted that tobramycin MIC90 concentration (minimal inhibitory concentration to 90% of microbial growth) rapidly declined following topical administration. It is hypothesized that adjustment of the pH of the empirically used tobramycin ophthalmic solution -prepared for human use- with the pH of the tears of donkeys, could increase the bioavailability of the drug and subsequently improve its penetration to the aqueous humor. Therefore, this study aimed to evaluate the impact of pH adjustment of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus). The study was conducted on six (n = 6) clinically healthy donkeys. In each donkey, one eye was randomly selected to receive 210 µg tobramycin of the commercial tobramycin (CT) and used as a positive control (C group, n = 6). The other eye (treated eye) received 210 µg of the modified tobramycin ophthalmic solution (MT) (T group, n = 6). Tears and aqueous humor samples were collected 5-, 10-, 15-, 30- min, and 1-, 2-, 4-, and 6 h post-instillation. RESULTS: Modifying the pH of the empirically used commercial tobramycin ophthalmic solution in donkeys at a pH of 8.26 enhanced the drug's bioavailability. The MIC90 of the most hazardous bacteria isolated from equines' eyes such as Pseudomonas aeruginosa (MIC90 = 128 µg/ml) and Staphylococcus aureus (MIC90 = 256 µg/ml) was covered early (5 min post-instillation) and over a longer period in donkey tears (239-342 min) and aqueous humor (238-330 min) with the modified tobramycin solution. CONCLUSIONS: Adjustment of the pH of the commercial tobramycin ophthalmic solution, empirically used by veterinarians to treat donkeys' ophthalmic infections at a pH of 8.26, isotonic with the donkeys' tears pH, resulting in higher concentrations of tobramycin in tears and aqueous humor for a longer time.

Development of a tobramycin-loaded calcium alginate microsphere/chitosan composite sponge with antibacterial effects as a wound dressing.

Traditional dressings exhibit several disadvantages, as they frequently lead to bacterial infections, cause severe tissue adhesion and perform a relatively single function. Therefore, in this study, a composite sponge dressing with antibacterial properties and excellent physicochemical properties was developed. Six groups of tobramycin-loaded calcium alginate microspheres were prepared by changing the amount of tobramycin added, and the optimal group was selected. Then, seven groups of tobramycin-loaded calcium alginate microsphere/chitosan composite sponges were fabricated via a solvent blending process and a freeze-drying method. The surface morphology, physicochemical properties,in vitrodegradation properties,in vitrodrug release properties, antibacterial properties and cytotoxicity of the composite sponges were examined. Group 3.0 contained the best microspheres with the largest drug loading capacity, good swelling performance and cumulative drug release rate, obvious and sustained antibacterial activity, and good cytocompatibility. The tobramycin-loaded calcium alginate microsphere/chitosan composite sponges exhibited three-dimensional porous structures, and their porosity, swelling rate, water absorption and water retention rates and water vapor transmission rate met the standards needed for an ideal dressing. The comprehensive performance of the sponge was best when 20 mg of drug-loaded microspheres was added (i.e. group 20). The cumulative drug release rate of the sponge was 29.67 ± 4.14% at 7 d, the diameters of the inhibition zones against the three bacteria were greater than 15 mm, and L929 cell proliferation was promoted. These results demonstrated that the tobramycin-loaded calcium alginate microsphere/chitosan composite sponge with 20 mg of tobramycin-loaded microspheres shows promise as a dressing for infected wounds.

Synergistic effects of inhaled aztreonam plus tobramycin on hypermutable cystic fibrosis Pseudomonas aeruginosa isolates in a dynamic biofilm model evaluated by mechanism-based modelling and whole genome sequencing.

OBJECTIVE: Hypermutable Pseudomonas aeruginosa strains are highly prevalent in chronic lung infections of patients with cystic fibrosis (CF). Acute exacerbations of these infections have limited treatment options. This study aimed to investigate inhaled aztreonam and tobramycin against clinical hypermutable P. aeruginosa strains using the CDC dynamic in vitro biofilm reactor (CBR), mechanism-based mathematical modelling (MBM) and genomic studies. METHODS: Two CF multidrug-resistant strains were investigated in a 168 h CBR (n = 2 biological replicates). Regimens were inhaled aztreonam (75 mg 8-hourly) and tobramycin (300 mg 12-hourly) in monotherapies and combination. The simulated pharmacokinetic profiles of aztreonam and tobramycin (t1/2 = 3 h) were based on published lung fluid concentrations in patients with CF. Total viable and resistant counts were determined for planktonic and biofilm bacteria. MBM of total and resistant bacterial counts and whole genome sequencing were completed. RESULTS: Both isolates showed reproducible bacterial regrowth and resistance amplification for the monotherapies by 168 h. The combination performed synergistically, with minimal resistant subpopulations compared to the respective monotherapies at 168 h. Mechanistic synergy appropriately described the antibacterial effects of the combination regimen in the MBM. Genomic analysis of colonies recovered from monotherapy regimens indicated noncanonical resistance mechanisms were likely responsible for treatment failure. CONCLUSION: The combination of aztreonam and tobramycin was required to suppress the regrowth and resistance of planktonic and biofilm bacteria in all biological replicates of both hypermutable multidrug-resistant P. aeruginosa CF isolates. The developed MBM could be utilised for future investigations of this promising inhaled combination.

Nlmixr2 Versus NONMEM: An Evaluation of Maximum A Posteriori Bayesian Estimates Following External Evaluation of Gentamicin and Tobramycin Population Pharmacokinetic Models.

The objective of this project is to compare the results of the same study carried out on NONMEM and nlmixr2. This analysis consists of evaluating previously published population pharmacokinetic models of gentamicin and tobramycin in our population of interest with sparse concentrations. A literature review was performed to determine the gentamicin and tobramycin models in critically ill adult patients. In parallel, gentamicin and tobramycin dosing data, information on the treatment, the patient, and the bacteria were collected retrospectively in 2 Quebec establishments. The external evaluations were previously performed using NONMEM Version 7.5. Model equations were rewritten with R, and external evaluations were performed using nlmixr2. Predictive performance was assessed based on the estimation of bias and imprecision of the prediction error for maximum a posteriori (MAP) Bayesian PK parameter and observed concentrations. Comparison between nlmixr2 and NONMEM was performed on 4 gentamicin and 3 tobramycin population pharmacokinetic models. Compared to NONMEM, for gentamicin and tobramycin clearance and central volume of distribution, nlmixr2 produced individual pharmacokinetic parameters with bias values ranging from -32.5% to 5.67% and imprecision values ranging from 6.33% to 32.5%. Despite these differences, population bias and imprecision for sparse concentrations were low and ranged from 0% to 5.3% and 0.2% to 6.5%, respectively. The external evaluations performed with both software packages resulted in the same interpretation in terms of population predictive performance for all 7 models. Nlmxir2 showed comparable predictive performance with NONMEM with sparse concentrations that are, at most, sampled twice within a single dose administration (peak and trough).

A comparison of aminoglycoside antibiotic serum concentrations collected by peripheral veins and peripherally inserted central catheters in adults with cystic fibrosis.

BACKGROUND: People with cystic fibrosis (PwCF) are frequently hospitalized for treatment of pulmonary exacerbation. The Cystic Fibrosis Foundation Pulmonary Guidelines support the use of intravenous aminoglycosides with therapeutic drug monitoring for the treatment of pulmonary exacerbation due to Pseudomonas aeruginosa. Serum intravenous tobramycin concentrations are commonly collected by peripheral venipuncture (PV). Discomfort associated with collection of samples by PV prompts collection via PICC, but the accuracy of intravenous tobramycin serum levels collected by PICC has not been documented in adult PwCF. The primary study objective was to evaluate the difference between intravenous tobramycin serum levels collected by PV and PICC in adult PwCF. METHODS: The authors conducted a prospective case-control study of adult PwCF admitted to University of Utah Health for a pulmonary exacerbation receiving tobramycin by a single lumen PICC. The authors compared tobramycin peak and random serum levels collected by PV and PICC using a detailed flush and waste protocol. RESULTS: The authors analyzed a total of 19 patients with peripheral and PICC samples. The mean tobramycin peak collected by PV (27.2 mcg/mL) was similar to the mean peak collected by PICC (26.9 mcg/mL) (paired samples Wilcoxon signed-rank test, p = .94). The correlation coefficient was 0.88 (95% CI = 0.85-0.91, p < .001). CONCLUSION: Tobramycin serum samples collected by PICC appear to be similar in value to PV collections. Collecting aminoglycoside levels by PICC rather than PV may reduce patient discomfort and improve quality of life. Additional multicenter studies are needed to confirm these results.

An Antibiotic Nanobomb Constructed from pH-Responsive Chemical Bonds in Metal-Phenolic Network Nanoparticles for Biofilm Eradication and Corneal Ulcer Healing.

In the treatment of refractory corneal ulcers caused by Pseudomonas aeruginosa, antibacterial drugs delivery faces the drawbacks of low permeability and short ocular surface retention time. Hence, novel positively-charged modular nanoparticles (NPs) are developed to load tobramycin (TOB) through a one-step self-assembly method based on metal-phenolic network and Schiff base reaction using 3,4,5-trihydroxybenzaldehyde (THBA), ε-poly-ʟ-lysine (EPL), and Cu2+ as matrix components. In vitro antibacterial test demonstrates that THBA-Cu-TOB NPs exhibit efficient instantaneous sterilization owing to the rapid pH responsiveness to bacterial infections. Notably, only 2.6 µg mL-1 TOP is needed to eradicate P. aeruginosa biofilm in the nano-formed THBA-Cu-TOB owing to the greatly enhanced penetration, which is only 1.6% the concentration of free TOB (160 µg mL-1). In animal experiments, THBA-Cu-TOB NPs show significant advantages in ocular surface retention, corneal permeability, rapid sterilization, and inflammation elimination. Based on molecular biology analysis, the toll-like receptor 4 and nuclear factor kappa B signaling pathways are greatly downregulated as well as the reduction of inflammatory cytokines secretions. Such a simple and modular strategy in constructing nano-drug delivery platform offers a new idea for toxicity reduction, physiological barrier penetration, and intelligent drug delivery.

Tobramycin-mediated self-assembly of DNA nanostructures for targeted treatment of Pseudomonas aeruginosa-infected lung inflammation.

Pseudomonas aeruginosa (PA) is one of the most common multidrug-resistant pathogens found in clinics, often manifesting as biofilms. However, due to the emergence of superbugs in hospitals and the overuse of antibiotics, the prevention and treatment of PA infections have become increasingly challenging. Utilizing DNA nanostructures for packaging and delivering antibiotics presents an intervention strategy with significant potential. Nevertheless, construction of functional DNA nanostructures with multiple functionalities and enhanced stability in physiological settings remains challenging. In this study, the authors propose a magnesium-free assembly method that utilizes tobramycin (Tob) as a mediator to assemble DNA nanostructures, allowing for the functionalization of DNA nanostructures by combining DNA and antibiotics. Additionally, our study incorporates maleimide-modified DNA into the nanostructures to act as a targeting moiety specifically directed towards the pili of PA. The targeting ability of the constructed functional DNA nanostructure significantly improves the local concentration of Tob, thereby reducing the side effects of antibiotics. Our results demonstrate the successful construction of a maleimide-decorated Tob/DNA nanotube (NTTob-Mal) for the treatment of PA-infected lung inflammation. The stability and biocompatibility of NTTob-Mal are confirmed, highlighting its potential for clinical applications. Furthermore, its specificity in recognizing and adhering to PA has been validated. In vitro experiments have shown its efficacy in inhibiting PA biofilm formation, and in a murine model, NTTob-Mal has exhibited significant therapeutic effectiveness against PA-induced pneumonia. In summary, the proposed antibiotic drug-mediated DNA nanostructure assembly approach holds promise as a novel strategy for targeted treatment of PA infections.

Inhaled antimicrobial prescribing for Pseudomonas aeruginosa infections in Europe.

BACKGROUND: Prescribers have an increasing range of inhaled antimicrobial formulations to choose from when prescribing both eradication and chronic suppression regimens in cystic fibrosis (CF). This study aimed to investigate the decision-making process behind prescribing of inhaled antimicrobials for Pseudomonas aeruginosa infections. METHODS: A questionnaire was developed using Microsoft Forms and then forwarded to 57 Principal Investigators (PIs), at each of the CF centres within the European Cystic Fibrosis Society-Clinical Trials Network (ECFS-CTN). Data collection occurred between November 2021 and February 2022. RESULTS: The response rate was 90 % (n = 51/57 PIs), with at least 50 % of CF centers in each of the 17 countries represented in the ECFS-CTN. Physicians used a median of eight factors in their decision-making process with delivery formulations (92.2 %), adherence history (84.3 %), and antibiotic side-effect profile (76.5 %) often selected. Nebulised tobramycin or colistin were frequently selected as the inhaled antimicrobial in first-line eradication (n = 45, 88.2 %) and chronic suppression regimens (n = 42, 82.4 %). Combination regimens were more often chosen in eradication (first-line: n = 35, 68.6 %, second-line: n = 34, 66.7 %) and later chronic suppression regimens (third-line: n = 27, 52.9 %) than monotherapy. For pwCF also prescribed CFTR modulator therapies, most PIs did not alter inhaled antimicrobial regimens (n = 40, 78.4 %), with few pwCF (n = 18, 35.3 %) or PIs (n = 10, 19.6 %) deciding to stop inhaled antimicrobials. CONCLUSIONS: The inhaled antimicrobial prescribing decision-making process is multifactorial. Nebulised tobramycin or colistin are often used in initial eradication and chronic suppression regimens. To date, CFTR modulator therapy has had a limited impact on the prescribing of inhaled antimicrobial regimens.

Necessity of Tobramycin trough Levels in Once Daily Iv-Treatment in Patients with Cystic Fibrosis.

BACKGROUND: Once daily intravenous (iv) treatment with tobramycin for Pseudomonas aeruginosa infection in patients with cystic fibrosis (pwCF) is frequently monitored by measuring tobramycin trough levels (TLs). Although the necessity of these TLs is recently questioned in pwCF without renal impairment, no study has evaluated this so far. The aim of this observational study was to evaluate the frequency of increased tobramycin TLs in pwCF treated with a once daily tobramycin dosing protocol. METHODS: Patient records of all consecutive once daily iv tobramycin courses in 35 pwCF between 07/2009 and 07/2019 were analyzed for tobramycin level, renal function, co-medication and comorbidity. RESULTS: Eight elevated TLs (2.9% of 278 courses) were recorded in four patients, two with normal renal function. One of these resolved without adjustment of tobramycin dosages suggesting a test timing or laboratory error. In the other patient the elevated tobramycin level decreased after tobramycin dosage adjustment. Six of the elevated levels occurred in two patients with chronic renal failure. In 15 other patients with reduced glomerular filtration rate (GFR) (36 courses) but normal range creatinine no case of elevated tobramycin trough levels was detected. Neither cumulative tobramycin dosages nor concomitant diabetes or nutritional status were risk factors for elevated TLs. CONCLUSION: Our data show that elevated tobramycin TLs are rare but cannot be excluded, so determination of tobramycin TLs is still recommended for safety.

Inhaled antibiotics for pulmonary exacerbations in cystic fibrosis.

BACKGROUND: Cystic fibrosis is a genetic disorder in which abnormal mucus in the lungs is associated with susceptibility to persistent infection. Pulmonary exacerbations are when symptoms of infection become more severe. Antibiotics are an essential part of treatment for exacerbations and inhaled antibiotics may be used alone or in conjunction with oral antibiotics for milder exacerbations or with intravenous antibiotics for more severe infections. Inhaled antibiotics do not cause the same adverse effects as intravenous antibiotics and may prove an alternative in people with poor access to their veins. This is an update of a previously published review. OBJECTIVES: To determine if treatment of pulmonary exacerbations with inhaled antibiotics in people with cystic fibrosis improves their quality of life, reduces time off school or work, and improves their long-term lung function. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis Group's Cystic Fibrosis Trials Register. Date of the last search: 7 March 2022. We also searched ClinicalTrials.gov, the Australia and New Zealand Clinical Trials Registry and WHO ICTRP for relevant trials. Date of last search: 3 May 2022. SELECTION CRITERIA: Randomised controlled trials in people with cystic fibrosis with a pulmonary exacerbation in whom treatment with inhaled antibiotics was compared to placebo, standard treatment or another inhaled antibiotic for between one and four weeks. DATA COLLECTION AND ANALYSIS: Two review authors independently selected eligible trials, assessed the risk of bias in each trial and extracted data. They assessed the certainty of the evidence using the GRADE criteria. Authors of the included trials were contacted for more information. MAIN RESULTS: Five trials with 183 participants are included in the review. Two trials (77 participants) compared inhaled antibiotics alone to intravenous antibiotics alone and three trials (106 participants) compared a combination of inhaled and intravenous antibiotics to intravenous antibiotics alone. Trials were heterogenous in design and two were only available in abstract form. Risk of bias was difficult to assess in most trials but, for four out of five trials, we judged there to be a high risk from lack of blinding and an unclear risk with regards to randomisation. Results were not fully reported and only limited data were available for analysis. One trial was a cross-over design and we only included data from the first intervention arm. Inhaled antibiotics alone versus intravenous antibiotics alone Only one trial (18 participants) reported a perceived improvement in lifestyle (quality of life) in both groups (very low-certainty evidence). Neither trial reported on time off work or school. Both trials measured lung function, but there was no difference reported between treatment groups (very low-certainty evidence). With regards to our secondary outcomes, one trial (18 participants) reported no difference in the need for additional antibiotics and the second trial (59 participants) reported on the time to next exacerbation. In neither case was a difference between treatments identified (both very low-certainty evidence). The single trial (18 participants) measuring adverse events and sputum microbiology did not observe any in either treatment group for either outcome (very low-certainty  evidence). Inhaled antibiotics plus intravenous antibiotics versus intravenous antibiotics alone Inhaled antibiotics plus intravenous antibiotics may make little or no difference to quality of life compared to intravenous antibiotics alone. None of the trials reported time off work or school. All three trials measured lung function, but found no difference between groups in forced expiratory volume in one second (two trials; 44 participants; very low-certainty evidence) or vital capacity (one trial; 62 participants). None of the trials reported on the need for additional antibiotics. Inhaled plus intravenous antibiotics may make little difference to the time to next exacerbation; however, one trial (28 participants) reported on hospital admissions and found no difference between groups. There is likely no difference between groups in adverse events (very low-certainty evidence) and one trial (62 participants) reported no difference in the emergence of antibiotic-resistant organisms (very low-certainty evidence). AUTHORS' CONCLUSIONS: We identified only low- or very low-certainty evidence to judge the effectiveness of inhaled antibiotics for the treatment of pulmonary exacerbations in people with cystic fibrosis. The included trials were not sufficiently powered to achieve their goals. Hence, we are unable to demonstrate whether one treatment was superior to the other or not. Further research is needed to establish whether inhaled tobramycin may be used as an alternative to intravenous tobramycin for some pulmonary exacerbations.

Computational Fluid Dynamics (CFD) Guided Spray Drying Recommendations for Improved Aerosol Performance of a Small-Particle Antibiotic Formulation.

PURPOSE: The objective of this study was to implement computational fluid dynamics (CFD) simulations and aerosol characterization experiments to determine best-case spray drying conditions of a tobramycin excipient enhanced growth (Tobi-EEG) formulation for use in a pediatric air-jet dry powder inhaler (DPI). METHODS: An iterative approach was implemented in which sets of spray drying conditions were explored using CFD simulations followed by lead candidate selection, powder production and in vitro aerosol testing. CFD simulations of a small-particle spray dryer were performed to capture droplet drying parameters and surface-averaged temperature and relative humidity (RH) conditions in the powder collection region. In vitro aerosol testing was performed for the selected powders using the pediatric air-jet DPI, cascade impaction, and aerosol transport through a pediatric mouth-throat (MT) model to a tracheal filter. RESULTS: Based on comparisons of CFD simulations and in vitro powder performance, recommended drying conditions for small-particle powders with electrostatic collection include: (i) reducing the CFD-predicted drying parameters of κavg and κmax to values below 3 µm2/ms and 114 µm2/ms, respectively; (ii) maintaining the Collector Surface RH within an elevated range, which for the Tobi-EEG formulation with l-leucine was 20-30 %RH; and (iii) ensuring that particles reaching the collector were fully dried, based on a mass fraction of solute CFD parameter. CONCLUSIONS: Based on the newly recommended spray dryer conditions for small particle aerosols, delivery performance of the lead Tobi-EEG formulation was improved resulting in >60% of the DPI loaded dose passing through the pediatric MT model.

Tobramycin Supplemented Small-Diameter Vascular Grafts for Local Antibiotic Delivery: A Preliminary Formulation Study.

Peripheral artery occlusive disease is an emerging cardiovascular disease characterized by the blockage of blood vessels in the limbs and is associated with dysfunction, gangrene, amputation, and a high mortality risk. Possible treatments involve by-pass surgery using autologous vessel grafts, because of the lack of suitable synthetic small-diameter vascular prosthesis. One to five percent of patients experience vascular graft infection, with a high risk of haemorrhage, spreading of the infection, amputation and even death. In this work, an infection-proof vascular graft prototype was designed and manufactured by electrospinning 12.5% w/v poly-L-lactic-co-glycolic acid solution in 75% v/v dichloromethane, 23.8% v/v dimethylformamide and 1.2% v/v water, loaded with 0.2% w/wPLGA. Polymer and tobramycin concentrations were selected after viscosity and surface tension and after HPLC-UV encapsulation efficiency (EE%) evaluation, respectively. The final drug-loaded prototype had an EE% of 95.58% ± 3.14%, with smooth fibres in the nanometer range and good porosity; graft wall thickness was 291 ± 20.82 µm and its internal diameter was 2.61 ± 0.05 mm. The graft's antimicrobic activity evaluation through time-kill assays demonstrated a significant and strong antibacterial activity over 5 days against Staphylococcus aureus and Escherichia coli. An indirect cell viability assay on Normal Human Dermal Fibroblasts (NHDF) confirmed the cytocompatibility of the grafts.

Intra-articular administration of vancomycin and tobramycin during primary cementless total knee arthroplasty : determination of intra-articular and serum elution profiles.

AIMS: Intra-articular administration of antibiotics during primary total knee arthroplasty (TKA) may represent a safe, cost-effective strategy to reduce the risk of acute periprosthetic joint infection (PJI). Vancomycin with an aminoglycoside provides antimicrobial cover for most organisms isolated from acute PJI after TKA. However, the intra-articular doses required to achieve sustained therapeutic intra-articular levels while remaining below toxic serum levels is unknown. The purpose of this study is to determine the intra-articular and serum levels of vancomycin and tobramycin over the first 24 hours postoperatively after intra-articular administration in primary cementless TKA. METHODS: A prospective cohort study was performed. Patients were excluded if they had poor renal function, known allergic reaction to vancomycin or tobramycin, received intravenous vancomycin, or were scheduled for same-day discharge. All patients received 600 mg tobramycin and 1 g of vancomycin powder suspended in 25 cc of normal saline and injected into the joint after closure of the arthrotomy. Serum from peripheral venous blood and drain fluid samples were collected at one, four, and 24 hours postoperatively. All concentrations are reported in µg per ml. RESULTS: A total of 22 patients were included in final analysis. At one, four, and 24 hours postoperatively, mean (95% confidence interval (CI)) serum concentrations were 2.4 (0.7 to 4.1), 5.0 (3.1 to 6.9), and 4.8 (2.8 to 6.9) for vancomycin and 4.9 (3.4 to 6.3), 7.0 (5.8 to 8.2), and 1.3 (0.8 to 1.8) for tobramycin; intra-articular concentrations were 1,900.6 (1,492.5 to 2,308.8), 717.9 (485.5 to 950.3), and 162.2 (20.5 to 304.0) for vancomycin and 2,105.3 (1,389.9 to 2,820.6), 403.2 (266.6 to 539.7), and 98.8 (0 to 206.5) for tobramycin. CONCLUSION: Intra-articular administration of 1 g of vancomycin and 600 mg of tobramycin as a solution after closure of the arthrotomy in primary cementless TKA achieves therapeutic intra-articular concentrations over the first 24 hours postoperatively and does not reach sustained toxic levels in peripheral blood. Cite this article: Bone Joint J 2021;103-B(11):1702-1708.

Efficacy of Problem-Solving Intervention to Improve Adherence in Adolescents and Adults with Cystic Fibrosis.

BACKGROUND: Adherence to treatment by adolescents and adults with cystic fibrosis (CF) is often poor. OBJECTIVES: To assess the impact of a focused clinical intervention on adherence in individual patients, including help in problem-solving key barriers to adherence. To implement a patient-centered problem-solving intervention using CF My Way tools. To identify and overcome a selected barrier to adherence. METHODS: Medication possession ratios (MPRs), number of airway clearance sessions, forced expiratory volume (FEV1), body mass index (BMI), and health-related quality of life (HRQoL) were measured before and after the intervention. RESULTS: Sixteen patients with CF, aged 23.4 ± 6.7 years, participated. MPR increased for colistimethate sodium and tobramycin inhalations from a median of 21 (range 0-100) to 56 (range 0-100), P = 0.04 and 20 (range 0-100) to 33.3 (range 25-100), P = 0.03, respectively. BMI standard deviation score rose from -0.37 to -0.21, P = 0.05. No significant improvements were found in FEV1, airway clearance, or HRQoL scores. CONCLUSIONS: The CF My Way problem-solving intervention increased adherence to medical treatments by removing barriers directly related to the needs and goals of young adults with CF.

Effect of Local Delivery of Vancomycin and Tobramycin on Bone Regeneration.

OBJECTIVE: A bone defect rat model was established to investigate the osteogenic effect of local delivery two antibiotics (vancomycin and tobramycin powder) on bone regeneration. METHODS: Twenty-four Sprague-Dawley (SD) male rats (6 to 8 weeks, 200 to 250 g) were used in this study. All these rats were randomly divided into four groups. Based on dose conversion between rat and human via body surface area, the rat dose of two antibiotics was 88µg/g and 176 µg/g for vancomycin and tobramycin, respectively. Con group (no antibiotic), Van group (vancomycin, 88 µg/g), Tob group (tobramycin 176 µg/g), and Van+Tob group (vancomycin 88µg/g combined with tobramycin 176 µg/g). A 5.0-mm full-thickness standardized mandibular bone defect was performed with a drill in each rat and different antibiotic powders were placed over the bone defect space, respectively. All these animals were sacrificed after 12 weeks post-operation. The mandible bones were harvested for further radiographic and histologic analysis. The bone volume/total volume (BV/TV) ratio, bone volume (BV), and bone fractional area (BFA) in the defect area via micro-computed tomography (µCT scanning) were further analyzed. Then, we performed a histological assessment via hematoxylin and eosin (H&E) and Masson's trichrome staining to analyze bone regeneration and also analyze the number of osteoblasts per filed. RESULTS: There were no postoperative deaths, signs of vancomycin-related or tobramycin-related toxicity, or signs of systemic illness in any of the four groups. All wounds healed well, and no complications or surgical site infection were observed in all rats. From the µCT scans analyses, there was less bone regeneration in the Van group than in the Con group (BV/TV: F = 64.29, R2  = 0.9602; P = 0.0052; BFA: F = 76.17, R2  = 0.9662, P = 0.0007; BV: F = 194.4, R2  = 0.9865, P = 0.0022). However, when the tobramycin and vancomycin were combined, an increase in bone defect re-ossification was found in the Van+Tob group than in the Van group (BV/TV: F = 64.29, R2  = 0.9602, P = 0.0033; BFA: F = 76.17, R2  = 0.9662, P = 0.0006; BV: F = 194.4, R2  = 0.9865, P = 0.0033). Routine H&E and Masson staining supported the finding of µCT scanning. Quantitative indices confirmed that both the bone regeneration and the number of osteoblasts per filed in the defect area was higher in the Van+Tob group than in the Van group (percentage of bone tissue: F = 145.7, R2  = 0.9562, P = 0.0008; number of osteoblasts per file; F = 67.3, R2  = 0.9098, P < 0.0001). There was no significant difference between the Con group and the Van+Tob group on the number of osteoblasts each field (F = 145.7, R2  = 0.9562, P > 0.9999). CONCLUSION: For bone defect, local application of vancomycin combined with tobramycin was recommended over vancomycin alone. This animal study presents data suggesting that the use of local delivery of vancomycin and tobramycin should be investigated further in clinical studies.

Distinct contribution of hyperbaric oxygen therapy to human neutrophil function and antibiotic efficacy against Staphylococcus aureus.

Staphylococcus aureus (SA) causes superficial and severe endovascular infections. The present in vitro study investigates the anti-SA mechanisms of hyperbaric oxygen therapy (HBOT) on direct bacterial killing, antibiotic potentiation, and polymorphonuclear leukocyte (PMN) enhancement. SA was exposed to isolated human PMNs, tobramycin, ciprofloxacin, or benzylpenicillin. HBOT was used as one 90-min session. Bacterial survival was evaluated after 4 h by quantitative bacteriology. PMN functionality as reactive oxygen species (ROS) production was measured by means of dihydrorhodamine 123 analysis. We showed that HBOT exhibits significant direct anti-SA effects. HBOT increased the anti-SA effects of PMNs by 18% after PMA stimulation (p = 0.0004) and by 15% in response to SA (p = 0.36). HBOT showed an additive effect as growth reductions of 26% to sub-MICs of tobramycin (p = 0.0057), 44% to sub-MICs of ciprofloxacin (p = 0.0001), and 26% to sub-MICs of penicillin (p = 0.038). The present in vitro study provides evidence that HBOT has differential mechanisms mediating its anti-SA effects. Our observation supports the clinical possibility for adjunctive HBOT to augment the host immune response and optimize the efficacy of antibiotic treatments.

Bayesian Forecasting for Intravenous Tobramycin Dosing in Adults With Cystic Fibrosis Using One Versus Two Serum Concentrations in a Dosing Interval.

BACKGROUND: Intravenous tobramycin treatment requires therapeutic drug monitoring (TDM) to ensure safety and efficacy when used for prolonged treatment, as in infective exacerbations of cystic fibrosis. The 24-hour area under the concentration-time curve (AUC24) is widely used to guide dosing; however, there remains variability in practice around methods for its estimation. The objective of this study was to determine the potential for a sparse-sampling strategy using a single postinfusion tobramycin concentration and Bayesian forecasting to assess the AUC24 in routine practice. METHODS: Adults with cystic fibrosis receiving once-daily tobramycin had paired concentrations measured 2 hours (c1) and 6 hours (c2) after the end of infusion as routine monitoring. AUC24 exposures were estimated using Tucuxi, a Bayesian forecasting application that incorporates a validated population pharmacokinetic model. Simulations were performed to estimate AUC24 using the full data set using c1 and c2, compared with estimates using depleted data sets (c1 or c2 only), with and without concentration data from earlier in the course. The agreement between each simulation condition and the reference was assessed graphically and numerically using the median difference (∆) AUC24 and (relative) root mean square error (rRMSE) as measures of bias and accuracy, respectively. RESULTS: A total of 55 patients contributed 512 concentrations from 95 tobramycin courses and 256 TDM episodes. Single concentration methods performed well, with median ∆AUC24 <2 mg·h·L-1 and rRMSE of <15% for sequential c1 and c2 conditions. CONCLUSIONS: Bayesian forecasting implemented in Tucuxi, using single postinfusion concentrations taken 2-6 hours after tobramycin administration, yield similar exposure estimates to more intensive (two-sample) methods and are suitable for routine TDM practice.

A pH-sensitive oxidized-dextran based double drug-loaded hydrogel with high antibacterial properties.

Delayed healing or non-healing of wounds caused by bacterial infection is still a difficult medical problem. Nowadays, the topical application of antibiotics is a common treatment for infections. However, subinhibitory concentrations or high dose of antibiotics leads to the antibacterial effect counterproductive. So it's necessary to put forward an on-demand drug delivery to solve this tough issue. In this paper, a pH-responsive hydrogel was prepared by oxidized dextran (Dex-CHO), sulfadiazine (SD) and tobramycin (TOB). The hydrogel was designed by the environment in the early immature stage of biofilm (pH 5.0). Schiff bases can release drugs in slightly acidic environment. The hydrogel showed injectable, pH-sensitive drug release, and great biocompatibility. Released SD and TOB exhibited a synergistic effect therefore the hydrogel showed high antibacterial activity. This study provides an easy and promising strategy to develop smart hydrogels that aim at topical administration of antibiotics and come up with a new treatment of local bacterial infections.