Optimizing Piperacillin Dosing in Pediatric Liver Transplant Recipients: A Case Series.

BACKGROUND: Pathophysiological changes post-liver transplantation impact the pharmacokinetics and pharmacodynamics of antibiotics. Piperacillin, often used in combination with tazobactam, is a key antibiotic after transplantation to its broad-spectrum activity, but there is a lack of specific pharmacokinetic data in this population. This study aims to describe the pharmacokinetic parameters and target attainment of piperacillin in pediatric liver transplant recipients. METHODS: Patients with preserved renal function (estimated glomerular filtration rate > 50 mL/min/1.73 m2) receiving intravenous piperacillin-tazobactam at 112.5 mg/kg every 8 h (100 mg piperacillin/12.5 mg tazobactam), with a rapid infusion (0.5-1 h), were included. Two blood samples per child were collected during the same interval within 48 h of starting therapy. A Bayesian approach was applied to estimate individual pharmacokinetic parameters and perform dosing recommendations against Enterococcus spp., Enterobacterales and Pseudomonas aeruginosa. RESULTS: Eight patients with median age of 8 months were included. Median piperacillin clearance and central volume of distribution for the cohort were 11.11 L/h/70 kg and 9.80 L/70 kg, respectively. Seven patients (87.5%) presented with concentrations below the target of 100% fT > MIC. Simulations suggested that these patients required more frequent dosing and extended duration of infusion to ensure target attainment. One patient (12.5%) had trough concentrations that exceed 16 mg/L and could receive a lower daily dose. CONCLUSIONS: This case series highlights the importance of personalized therapy in pediatric liver transplant recipients due to the unpredictable and highly variable piperacillin pharmacokinetics in this population.

Comparison of vancomycin assays in patients undergoing hemodialysis.

Vancomycin is a glycopeptide antibiotic mainly excreted by glomerular filtration. Therefore, patients undergoing hemodialysis tend to accumulate its crystalline degradation product, which has been associated with cross-reaction in commercial immunoassays. The aim of this study was to assess the performance of two commercial immunoassays for measuring vancomycin levels in patients undergoing hemodialysis. This method-comparison study enrolled patients undergoing hemodialysis at two hospitals in Porto Alegre, Brazil. Vancomycin serum concentrations measured by Chemiluminescent Microparticle Assay (CMIA) and measured by Kinetic Interaction of Microparticles in Solution (KIMS) were compared with Liquid Chromatography coupled with Tandem Mass Spectrometry (LC-MS/MS). A total of 64 samples from 42 patients and 54 samples from 23 patients were included in CMIA and KIMS groups. Both measurements were highly correlated with LC-MS/MS, with Spearman rank correlation coefficient r = 0.840 (p < 0.001) and r = 0.926 (p < 0.001), respectively. No deviation of linearity was observed (p = 0.81 and p = 0.49, respectively). The mean difference between CMIA and LC-MS/MS was -1.19 µg/mL and between KIMS and LC-MS/MS was -2.28 µg/mL. LC-MS/MS measured levels were, on average, 2.64 % higher than CMIA and 8.81 % higher than KIMS. CMIA and KIMS revealed accurate commercial methods to measure vancomycin serum concentrations in patients undergoing hemodialysis.

Switching Vancomycin Monitoring From Trough Concentration to Area Under the Curve Estimation by Bayesian Forecasting: A Short Communication on a Cost-Benefit Study in Resource-Limited Settings.

BACKGROUND: This study was conducted to evaluate the cost-benefit indicators of a vancomycin monitoring protocol based on area under the curve estimation using commercial Bayesian software. METHODS: This quasi-experimental study included patients who were aged >18 years with a vancomycin prescription for >24 hours. Patients who were terminally ill or those with acute kidney injury (AKI) ≤24 hours were excluded. During the preintervention period, doses were adjusted based on the trough concentration target of 15-20 mg/L, whereas the postintervention period target was 400-500 mg × h/L for the area under the curve. The medical team was responsible for deciding to stop the antimicrobial prescription without influence from the therapeutic drug monitoring team. The main outcomes were the incidence of AKI and length of stay. Cost-benefit simulation was performed after statistical analysis. RESULTS: There were 96 patients in the preintervention group and 110 in the postintervention group. The AKI rate decreased from 20% (n = 19) to 6% (n = 6; P = 0.003), whereas the number of vancomycin serum samples decreased from 5 (interquartile range: 2-7) to 2 (interquartile range: 1-3) examinations per patient ( P < 0.001). The mean length of hospital stay for patients was 26.19 days after vancomycin prescription, compared with 17.13 days for those without AKI ( P = 0.003). At our institution, the decrease in AKI rate and reduced length of stay boosted yearly savings of up to US$ 369,000 for 300 patients receiving vancomycin therapy. CONCLUSIONS: Even in resource-limited settings, a commercial Bayesian forecasting-based protocol for vancomycin is important for determining cost-benefit outcomes.

External Evaluation of Population Pharmacokinetic Models of Piperacillin in Preterm and Term Patients from Neonatal Intensive Care.

BACKGROUND AND OBJECTIVES: Piperacillin/tazobactam is extensively used off-label to treat late-onset neonatal sepsis, but safety and pharmacokinetic data in this population are limited. Additionally, the organic immaturity of the newborns contributes to a high piperacillin pharmacokinetic variability. This affects the clinical efficacy of the antibiotic treatment and increases the probability of developing drug resistance. This study aimed to evaluate the predictive performance of reported piperacillin population pharmacokinetic models for their application in a model-informed precision dosing strategy in preterm and term Mexican neonatal intensive care patients. METHODS: Published population pharmacokinetic models for piperacillin which included neonates in their study population were identified. From the reference models, structured models, population pharmacokinetic parameters, and interindividual and residual variability data were extracted to be replicated in pharmacokinetic software (NONMEM® version 7.4). For the clinical study, a sampling schedule was designed, and 2-3 blood samples of 250 µL were taken from neonates who met the inclusion criteria. Piperacillin plasma concentrations were determined by liquid chromatography/tandem mass spectrometry. The clinical treatment data were collected, and piperacillin plasma concentrations were estimated using reference pharmacokinetic models for an a priori or Bayesian approach. Statistical methods were used in terms of bias and precision to evaluate the differences between observed and estimated neonatal piperacillin plasma concentrations with the different approaches and to identify the pharmacokinetic model that best fits the neonatal data. RESULTS: A total of 70 plasma samples were collected from 25 neonatal patients, of which 15 were preterm neonates. The overall median value (range) postnatal age, gestational age, body weight, and serum creatinine at the sampling collecting day were 12 (3-26) days, 34.2 (26-41.1) weeks, 1.78 (0.08-3.90) Kg, 0.47 (0.20-0.90) mg/dL, respectively. Three population pharmacokinetic models for piperacillin in infants up to 2 months were identified, and their predictive performance in neonatal data was evaluated. No pharmacokinetic model was suitable for our population using an a priori approach. The model published by Cohen-Wolkowiez et al. in 2014 with a Bayesian approach showed the best performance of the pharmacokinetic models evaluated in our neonatal data. The procedure requires two blood samples (predose and postdose), and, when applied, it predicted 66.6% of the observations with a relative median absolute predicted error of less than 30%. CONCLUSIONS: The population pharmacokinetic model developed by Cohen-Wolkowiez et al. in 2014 demonstrated superior performance in predicting the plasma concentration of piperacillin in preterm and term Mexican neonatal intensive care patients. The Bayesian approach, including two different piperacillin plasma concentrations, was clinically acceptable regarding bias and precision. Its application for model-informed precision dosing can be an option to optimize the piperacillin dosage in our population.

Impact of Vancomycin trough levels monitoring on uncomplicated methilcillin-resistant Staphylococcus aureus bacteremia in chronic kidney disease on hemodialysis, retrospective cohort.

BACKGROUND: CKD patients on hemodialysis (HD) with Staphylococcus aureus (SA) bacteremia present high morbidity, mortality and increased risk of MRSA. Vancomycin is the antibiotic of choice in these cases, it has a narrow therapeutic margin and inadequate dosage generates a risk of toxicity, therefore, the recommendation is to dosage it through serum levels. METHODS: This is a retrospective cohort study in 3 hospitals of third level of complexity in the city of Medellin in which there were differences in the measurement and implementation of vancomycin25 dosage based on trough levels (VL) in patients with chronic kidney disease on hemodialysis (CKD- HD) with uncomplicated bacteremia based infection by methilcillin-resistant Staphyloccocus aureus (MRSA). The primary outcome was the composite of hospital mortality, clinical response (fever, hemodynamic instability and altered consciousness), complications associated with bacteremia, or bacteriological response failure (positive cultures at first week follow-up) at 7 days. The composite variables were analyzed individually as secondary outcomes. RESULTS: The main unadjusted outcome (OR 1.3, CI 0.6 - 2.7) and adjusted for age, Charlson index, loading dose, initial dose, dosing frequency and MIC to vancomycin (OR 1.2, CI 0.5 - 2.7). Regarding adjusted secondary outcomes: clinical response (OR 1.4 CI 0.3 - 5.8), death (OR 1.3 CI 0.3 - 4.6) and complications (OR 0.9, CI 0.37 - 2.2). CONCLUSIONS: We conclude that the measurement of trough levels in patients with HD-CKD does not modify the composite outcome. The main limitation is the sample size and type of study, randomized control trials may be required to confirm the results presented.

Association between prolonged vancomycin infusion and trough concentrations in children. Retrospective study. / Asociación entre infusión prolongada de vancomicina y concentración valle en niños. Estudio retrospectivo.

Introduction: This study investigated the serum concentration of vancomycin during prolonged infusion in children. Population and methods: This retrospective cohort study included pediatric patients who received vancomycin from June 2017 to June 2020 at a tertiary referral hospital. The patients were divided into two groups according to infusion strategy, the SII (standard intermittent infusion) group and the PI (prolonged infusion) group. Demographic details, infusion period, serum creatinine, duration of vancomycin therapy, trough concentration of vancomycin, and pediatric intensive care unit stay were reviewed. Differences of the concentrations were measured. Results: Sixty-eight patients were included: 31 in the SII group and 37 in the PI group. The trough concentration of vancomycin was significantly higher in the PI group than in SII group (11.2 mg/L [5.9-13.7] vs. 7 mg/L [3.5- 9.3]; p = 0.02). The target attainment rate was higher in the PI group than in the SII group (59.4% and 19.3%, respectively; p = 0.001). There were no significant differences between the SII and PI groups regarding the peak concentrations of vancomycin, final creatinine and peak creatinine. There were no differences between the SII and PI groups regarding the failure events, PICU stay and duration of vancomycin therapy. The multivariable analysis showed that PI was significantly associated with higher trough serum concentrations of vancomycin (OR = 2.27; p = 0.005). Conclusion: Compared to the SII strategy, the PI strategy may be an optimized option to children with severe infection, as it can achieve higher trough concentrations and target concentration attainment.

Introducción: Este estudio investigó la concentración plasmática de vancomicina en los niños, durante la infusión prolongada. Población y métodos: Estudio retrospectivo de una cohorte que incluyó pacientes pediátricos tratados con vancomicina desde junio de 2017 hasta junio de 2020, en un hospital de referencia de nivel III. Los pacientes se dividieron en dos grupos sogún el tipo de infusión: el grupo de infusión intermitente estándar (IIE) y el grupo de infusión prolongada (IP). Se registraron detalles demográficos, periodo de infusión, creatinina plasmática, duranción del tratamiento con vancomicina, concentración valle de vancomicina y permanencia en la unidad de cuidados intensivos pediátricos (UCIP). Se midieron las diferencias entre concentraciones. Resultados: Se incluyeron 68 pacientes, 31 en el gruop IIE y 37 en el grupo IP. La concentración valle de vancomicina fue significativamente más alta en el grupo IP en comparación con el grupo IIE (11,2mg/L [5,9-13,7] vs. 7 mg/L [3,5-9,3]; p = 0,02). La tasa de logro del objetivo fue más alta en el grupo IP que en el grupo IIE (59,4 % y 19,3 % repectivamente; p = 0,001). No hubo diferencias significativas entre ambos grupos en las concentraciones pico de vancomicina, valor de creatinina final, pico de creatinina, fracaso terapéutico, duración de la estadía en la UCIP y duración del tratamiento con vancomicina. El análisis multivariado mostró que la IP se asoció en forma significativa con concentraciones valle más altas de vancomicina (OR: 2,27, p = 0,005). Conclusión: En comparación con la estrategia de IIE, la infusión prolongada puede ser una opción optimizada para los niños con infección grave, porque puede alcanzar concentraciones valle más altas y mejorar la obtención de la concentración objetivo.

The vehicle of administration, feed or water, and prandial state influence the oral bioavailability of amoxicillin in piglets.

Feed and water components may interact with drugs and affect their dissolution and bioavailability. The impact of the vehicle of administration (feed and water) and the prandial condition of weaner piglets on amoxicillin´s oral bioavailability was evaluated. First, amoxicillin's in vitro dissolution and stability in purified, soft, and hard water, as well as release kinetics from feed in simulated gastric and intestinal media were assessed. Then, pharmacokinetic parameters and bioavailability were determined in fasted and fed pigs using soft water, hard water, or feed as vehicles of administration following a balanced incomplete block design. Amoxicillin showed similar dissolution profiles in soft and hard water, distinct from the dissolution profile obtained with purified water. Complete dissolution was only achieved in purified water, and merely reached 50% in soft or hard water. Once dissolved, antibiotic concentrations decreased by around 20% after 24 h in all solutions. Korsmeyer-Peppas model best described amoxicillin release from feed in simulated gastric and intestinal media. Feed considerably reduced antibiotic dissolution in both simulated media. In vivo, amoxicillin exhibited significantly higher bioavailability when delivered via water to fasted than to fed animals, while in-feed administration yielded the lowest values. All treatments showed a similar rate of drug absorption. In conclusion, we demonstrated that water and feed components, as well as feed present in gastrointestinal tract of piglets decrease amoxicillin´s oral bioavailability. Therefore, the use of oral amoxicillin as a broad-spectrum antibiotic to treat systemic infections in pigs should be thoroughly revised.

Analysis of Vancomycin Dosage and Plasma Levels in Critically Ill Adult Patients Requiring Extracorporeal Membrane Oxygenation (ECMO).

Introduction: Critically ill patients undergoing extracorporeal membrane oxygenation (ECMO) exhibit unique pharmacokinetics. This study aimed to assess the achievement of vancomycin therapeutic targets in these patients. Methods: This retrospective cohort study included patients on ECMO treated with vancomycin between January 2010 and December 2018. Ninety patients were analyzed based on ECMO connection modality, baseline creatinine levels, estimated glomerular filtration rate (eGFR), renal replacement therapy (RRT) requirements, and vancomycin loading dose administration. Results: Twenty-three percent of the patients achieved the therapeutic range defined by baseline levels. No significant differences in meeting the therapeutic goal were found in multivariate analysis considering ECMO cannulation modality, initial creatinine level, initial eGFR, RRT requirement, or loading dose use. All trough levels between 15 and 20 mcg/mL achieved an estimated area under the curve/minimum inhibitory concentration (AUC/MIC) between 400 and 600, almost all trough levels over 10 mcg/mL predicted an AUC/MIC >400. Discussion: Achieving therapeutic plasma levels in these patients remains challenging, potentially due to factors such as individual pharmacokinetics and pathophysiology. A trough plasma level between 12 and 20 estimated the therapeutic AUC/MIC for all models, proposing a possible lower target, maintaining exposure, and potentially avoiding adverse effects. Despite being one of the largest cohorts of vancomycin use in ECMO patients studied, its retrospective nature and single-center focus limits its broad applicability.

Adsorption Mass Transfer Zone of Vancomycin in Cartridges With Styrene-Divinylbenzene Sorbent.

Cartridges for hemoadsorption containing styrene-divinylbenzene sorbent are used for multiple conditions, such as intoxication. The mass transfer zone comprises the extension along the longitudinal span of the cartridge where adsorption occurs. The aim of this experiment is to evaluate the mass transfer zone for vancomycin in the HA380 cartridge. The experiment was carried out twice. A saline solution with vancomycin passed through a HA380-modified cartridge at 100 ml/min in a single-pass fashion. The cartridge had four openings along its longitudinal dimension, at 3, 6, 9, and 12 cm. In both experiments, the collection of aliquots occurred at minute 4, in the four openings and pre- and post-cartridge, and an additional sample from the effluent bag at the end of each experiment. In the second experiment, an additional sampling of the same six sites occurred at minute 14. The sigmoidal shape of the curve for the mass transfer zone of vancomycin was similar to the theoretical one. In experiment one, at minute 4, vancomycin clearance was 98.75 ml/min. In experiment two, vancomycin clearance at minutes 4 and 14 was 93.76 and 93.20 ml/min, respectively. This implies an adequate and optimal design of the HA380 cartridge.

Pharmacokinetics of doxycycline hyclate in pigs with a new feed premix formulation.

This study aimed to evaluate the administration of doxycycline hyclate in a long-acting pharmaceutical preparation in pigs when administered either ad libitum as a feed medication or an oral bolus dose. In all instances, the studied dose was 20 mg/kg b.w. A total of 48 healthy crossbred, castrated male pigs (Landrace-Yorkshire) weighing 23 ± 4.3 kg were included in this trial. They were randomly assigned to six groups as follows: two groups for the experimental prototype 1 of doxycycline hyclate administering it ad libitum (Fad-lib) or as forced bolus (Fbolus); two groups for the experimental prototype 2 of doxycycline hyclate as for the former groups (FCad-lib and FCbolus), and two control groups receiving the same dose of doxycycline hyclate, but of a commercial premix, also as previously explained (Cbolus and Cad-lib). Statistical analysis of the mean pharmacokinetic values was carried out with Kruskal-Wallis and Dunn's tests. The relative bioavailability (Fr) of the best prototype, when administered ad libitum (FCad-lib), was five times larger than the reference group (Cadlib). These results allow the proposal that the referred differences achieved in the presented prototypes can mark a notable clinical difference, particularly in pathogens with some resistance.

Plasma disposition of florfenicol after intramuscular administration in rabbits pretreated with pentoxifylline.

This work aimed to assess the effects of the coadministration of pentoxifylline (PTX) on the pharmacokinetic profile of florfenicol (FFC) after intramuscular administration in rabbits. Ten New Zealand white rabbits, 1 year of age and 3.9 ± 0.1 kg body weight, were assigned according to a randomized block design to Group 1 (FFC): treated with 30 mg/kg of FFC intramuscularly, and Group 2 (PTX + FFC) treated with an oral dose of 30 mg/kg PTX 45 min before the intramuscular injection of 30 mg/kg FFC. Blood samples were collected before and at different times between 0.5 and 12.0 h after drug administration. FFC plasma concentrations were determined by high-performance liquid chromatography. Results showed that IM injection of the long-acting formulation of FFC in rabbits resulted in a slow increase in mean plasma concentrations reaching a Cmax of 3.09 ± 0.52 ug/mL at 2.8 ± 0.45 h (Tmax ) after drug administration. While coadministration of PTX and FFC decreased the time to achieve the maximal concentration by modifying the absorption of FFC without changes in the other pharmacokinetic parameters.

Individualized optimization of colistin loading doses.

Colistin remains one of the few available options for the treatment of infections caused by resistant bacteria. Pharmacokinetic (PK) studies have been successful in estimating the appropriate colistin methanesulfonate (CMS) dose to achieve a target colistin concentration. Currently, there is a consensus that the dose of CMS should vary according to the patient renal function since CMS is mainly eliminated by renal route. For this same reason, the loading dose should vary according to the patient's renal capacity; however, this is not the current clinical practice. In this study we develop a framework to determine two key parameters for the loading dose regimen: (1) the optimal dose according to the characteristics (renal function and weight) of the patient; (2) the waiting time before the maintenance dose. Based on a previous PK model, our framework allows a fast parameter sweep so as to select optimal loading dose and waiting time minimizing the deviation between the plasma concentration and a target value. The results showed that patients presenting low creatinine clearance (CrCL) should receive a lower CMS loading dose with longer interval to start maintenance treatment to avoid nephrotoxic colistin concentrations. In cases of high CrCL, the dose should be higher and the interval to the next dose shorter to avoid subtherapeutic concentrations. Optimization of the loading dose should considerably improve colistin therapy, as the target concentration is reached more quickly, without reaching toxic values.

Pharmacokinetic Profile of Norfloxacin in Pigeons / Perfil Farmacocinético da Norfloxacina em Pombos

Through this work, the pharmacokinetics of Norfloxacin in pigeons were explored by using six healthy male pigeons as the subjects for this study. The pharmacokinetic indices of orally administered Norfloxacin were obtained by microbiological assay and then the data were fitted to the two-compartment pharmacokinetic open model to evaluate the distribution and excretion parameters.In the achieved results, the calculated absorption rate constant (Kab) was 1.26 h-1, the maximum achieved concentration of Norfloxacin was 2.75 µg/ml at 1.34 hr., the volume of distribution (Vd/F) was 3.15 L/kg.The half-life (t1/2ß) was 4.9 hrs., the calculated area under the curve of Norfloxacin (AUC0-t) was 16.75 (h*µg)/ml, while the clearance of Norfloxacin (Cl/F) was 0.49 L/hr/kg.In conclusion, the pharmacokinetic parameters of Norfloxacin in pigeons are not far away from other birds like chickens, considering the differences among them. Norfloxacin is a valuable antibacterial agent against susceptible bacterial infections depending on the obtained pharmacokinetic profile.(AU)

Através deste trabalho, a farmacocinética da Norfloxacina em pombos foi explorada usando seis pombos machos saudáveis como sujeitos para este estudo. Os índices farmacocinéticos da norfloxacina, administrada por via oral, foram obtidos por ensaio microbiológico e, em seguida, os dados foram ajustados ao modelo aberto de farmacocinética de dois compartimentos para avaliar os parâmetros de distribuição e excreção. Nos resultados obtidos, a taxa constante de absorção (Kab) calculada foi de 1,26 h-1, a concentração máxima alcançada da Norfloxacina foi de 2,75 µg/ml em 1,34 h, o volume de distribuição (Vd/F) foi de 3,15 L/kg. A meia-vida (t1/2ß) foi de 4,9 h, a área calculada sob a curva de concentração da Norfloxacina (AUC0-t) foi de 16,75 (h*µg)/ml, enquanto a depuração da Norfloxacina (Cl/F) foi de 0,49 L/h/kg. Em conclusão, os parâmetros farmacocinéticos da Norfloxacina em pombos não estão muito longe de outras aves, como galinhas, considerando as diferenças entre eles. A norfloxacina é um agente antibacteriano valioso contra infecções bacterianas susceptíveis, dependendo do perfil farmacocinético obtido.(AU)

Development of a xanthan gum film for the possible treatment of vaginal infections.

Bacterial vaginosis is a vaginal infection that affects 60% of women of reproductive age worldwide. It is mainly caused by the bacterium Gardnerella vaginalis and is a factor that increases the probability of getting sexually transmitted diseases. We aimed to develop a new pharmaceutical form for the treatment of vaginal infections. We employed the solving-casting method to fabricate a polymeric film with Xanthan gum, a natural polymer produced by the bacterium Xanthomonas campestris, and metronidazole, one of the most commonly used drugs for vaginal infections. In order to characterize the film, we measured pH, dose uniformity, dissolution profile, and the percentage of swelling. Moreover, we performed a thermogravimetric analysis and scanning electron microscopy. The results demonstrated a pH suitable for vaginal application and uniform distribution of the drug in the film. Also, the formulation exhibited a high percentage of swelling and a slow release of the drug in a simulated vaginal fluid medium. All these attributes indicated that the manufactured film has ideal characteristics to be used and administered vaginally. It could be an excellent alternative to treat bacterial vaginosis and also improve user adherence.

PK/PD modeling of daptomycin against MRSA and MRSE and Monte Carlo simulation for bacteremia treatment.

OBJECTIVES: The aim of this study was to investigate the effect of daptomycin against methicillin-resistant staphylococci (MRSA and MRSE) bacteremia using computer modeling. METHODS: A pharmacokinetic/pharmacodynamic (PK/PD) modeling strategy to explain the data from an in vitro dynamic model employing time-kill curves for MRSA and MRSE was proposed. Bacterial killing was followed over time by determining viable counts and the resulting time-kill data was analyzed. Monte Carlo simulations were performed using pharmacokinetic parameters and pharmacodynamic data to determine the probabilities of target attainment and cumulative fractions of response in terms of area under the concentration curve/minimum inhibition concentration (MIC) targets of daptomycin. Simulations were conducted to assess the reduction in the number of colony-forming units (CFU)/mL for 18 days of treatment with daptomycin at doses of 6, 8, and 10 mg/kg/24 h or 48 h with variations in creatinine clearance (CLCR): 15-29 mL/min/1.73 m2, 30-49 mL/min/1.73 m2, 50-100 mL/min/1.73 m2, as well as for defining the probability of reaching the target fAUC/MIC = 80 in the same dose and clearance range. A PK/PD model with saturation in the number of bacteria in vitro, growth delay, and bacterial death, as well as Hill's factor, was used to describe the data for both MRSA and MRSE. RESULTS: Monte Carlo simulations showed that for MRSA there was a reduction > 2 log CFU/mL with doses ≥ 6 mg/kg/day in 75th percentile of the simulated population after 18 days of treatment with daptomycin, whereas for MRSE this reduction was observed in 95th percentile of the population. CONCLUSIONS: The presented in vitro PK/PD model and associated modeling approach were able to characterize the time-kill kinetics of MRSA and MRSE. Our study based on PTAs suggests that doses ≥ 6 mg/kg/day of daptomycin should be used to treat bacteremia caused by MRSA and MRSE in patients with CLCR of 15-29 mL/min/1.73 m2. For patients with CLCR ≥ 50 mL/min/1.73 m2, it would be necessary to employ a dose of 10 mg/kg/day to treat complicated bacteremias.

Ceftriaxone and methicillin-susceptible staphylococcus aureus: a perspective from pharmacokinetics/pharmacodynamics studies.

Introduction: Usage of ceftriaxone-based therapy to treat Methicillin-Susceptible Staphylococcus aureus (MSSA) infections is a controversial issue, from in vitro to clinical studies.Area covered: We conducted a literature review using PubMed of articles with ceftriaxone pharmacokinetics parameters and built a probability of target attainment (PTA) based on PK values from stable conditions (non-critically-ill patients) with goals of fT>55%, fT>75%, and fT>100%. Ceftriaxone's minimal inhibitory concentration from 31 MSSA strains (0.25-64 mg/L) was used to build the cumulative fraction response (CFR). The isolates were clinically relevant from blood, bronchoalveolar lavage, and soft tissue biopsy.Expert opinion: The results from controversies about using ceftriaxone for MSSA infections have been commonly addressed in the literature. However, variables such as (i) pharmacokinetic profile, (ii) pharmacodynamic target, (iii) site of infection, and (iv) MIC distributions may influence divergences. From this pharmacokinetics-pharmacodynamics perspective, ceftriaxone may be a reasonable option for MSSA infections when the MIC50 and MIC90 were 4 mg/L and 8 mg/L. CFR analysis demonstrated that ceftriaxone 1 g q24 h could be used if bacteriostasis is the aim (fT>55%), while 1 g q12h should be used for bactericidal effects (fT>75% or fT>100%). These dosing regimens should be considered in other clinical trials.

Antibacterial and antibiotic modifying activity, ADMET study and molecular docking of synthetic chalcone (E)-1-(2-hydroxyphenyl)-3-(2,4-dimethoxy-3-methylphenyl)prop-2-en-1-one in strains of Staphylococcus aureus carrying NorA and MepA efflux pumps.

A large number of infections are caused by multi-resistant bacteria worldwide, adding up to a figure of around 700,000 deaths per year. Because of that many strategies are being developed in order to combat the resistance of microorganisms to drugs, in recent times, chalcones have been studied for this purpose. Chalcones are known as α, ß-unsaturated ketones, characterized by having the presence of two aromatic rings that are joined by a three-carbon chain, they are a class of compounds considered an exceptional model due to chemical simplicity and a wide variety of biological activities, which include anticancer, anti-inflammatory, antioxidants, antimicrobials, anti-tuberculosis, anti-HIV, antimalarial, anti-allergic, antifungal, antibacterial, and antileishmanial. The objective of this work was evaluate the antibacterial and antibiotic modifying activity of chalcone (E)-1-(2-hydroxyphenyl)-3-(2,4-dimethoxy-3-methylphenyl)prop-2-en-1-one against the bacteria Staphylococcus aureus carrying a NorA and MepA efflux pump. The results showed that chalcone was able to synergistically modulate the action of Norfloxacin and Ethidium Bromide against the bacteria Staphylococcus aureus 1199B and K2068, respectively. The theoretical physicochemical and pharmacokinetic properties of chalcone showed that the chalcone did not present a severe risk of toxicity such as genetic mutation or cardiotoxicity, constituting a good pharmacological active ingredient.

A short synthetic peptide, based on LyeTx I from Lycosa erythrognatha venom, shows potential to treat pneumonia caused by carbapenem-resistant Acinetobacter baumannii without detectable resistance.

The emergence of antibiotic-resistant bacteria, especially carbapenem-resistant Acinetobacter baumannii (CRAB), together with relative stagnation in the development of effective antibiotics, has led to enormous health and economic problems. In this study, we aimed to describe the antibacterial spectrum of LyeTx I mnΔK, a short synthetic peptide based on LyeTx I from Lycosa erythrognatha venom, against CRAB. LyeTx I mnΔK showed considerable antibacterial activity against extensively resistant A. baumannii, with minimum inhibitory and bactericidal concentrations ranging from 1 to 16 µM and 2 to 32 µM, respectively. This peptide significantly increased the release of 260 nm-absorbing intracellular material from CRAB, suggesting bacteriolysis. LyeTx I mnΔK was shown to act synergistically with meropenem and colistin against CRAB. The cytotoxic concentration of LyeTx I mnΔK against Vero cells (CC50 = 55.31 ± 5.00 µM) and its hemolytic activity (HC50 = 77.07 ± 4.00 µM) were considerably low; however, its antibacterial activity was significantly reduced in the presence of human and animal serum and trypsin. Nevertheless, the inhalation of this peptide was effective in reducing pulmonary bacterial load in a mouse model of CRAB infection. Altogether, these results demonstrate that the peptide LyeTx I mnΔK is a potential prototype for the development of new effective and safe antibacterial agents against CRAB.

Meropenem use and therapeutic drug monitoring in clinical practice: a literature review.

WHAT IS KNOWN AND OBJECTIVE: Meropenem, a carbapenem antibiotic, is widely prescribed for the treatment of life-threatening infections. The main parameter associated with its therapeutic success is the percentage of time that the levels remain above the minimum inhibitory concentration. Inadequate levels of meropenem can lead to therapeutic failure and increase the possibility of microbial resistance. The employment of strategies involving dose regimens and drug pharmacodynamics has become increasingly important to optimize therapies. In the present study, we conducted a review with the purpose of assembling information about the clinical use of meropenem and therapeutic drug monitoring. METHODS: A literature review emphasizing the application of therapeutic drug monitoring (TDM) of meropenem in clinical practice has been done. To identify articles related to the topic, we performed a standardized search from January 21, 2020 to December 21, 2020, using specific descriptors in PubMed, Lilacs and Embase. RESULTS AND DISCUSSION: In total, 35 studies were included in the review. The daily dose of meropenem commonly ranged from 3 to 6 g/day. Critically ill patients and those with impaired renal function appear to be the most suitable patients for the application of meropenem TDM, in order to guide therapy. We observed that most of the studies recommend TDM and that, in nine locations, the TDM of meropenem and of other beta-lactams is a routine practice. TDM data can help to maximize the clinical outcomes of the treatment with meropenem. It can also improve the patient care by providing suitable levels of meropenem, guiding the most appropriate dose regimens, which is the main parameter associated with therapeutic success. WHAT IS NEW AND CONCLUSION: The findings from this review suggest that the therapeutic monitoring of meropenem can be beneficial, since it adjusts the treatment and aids clinical outcomes. It does so by indicating the appropriate dosage and preventing failure, toxicity and possible antimicrobial resistance. The multidisciplinary effort, basic knowledge and communication among the medical team are also essential.

Inhibitory effect of Brazilian red propolis on planktonic and biofilm forms of Clostridioides difficile.

Clostridioides difficile is a Gram-positive, spore-forming, anaerobic bacillus which is the leading cause of health-care-associated infective diarrhea. The rising incidence of antibiotic resistance in pathogens such as C. difficile makes researches on alternative antibacterial products very important, especially those exploring natural products like propolis. Brazilian Red Propolis, found in the Northeast region of Brazil, is composed by products from regional plants that have the antimicrobial properties. This study aimed to evaluate the in vitro activity of Brazilian Red Propolis (BRP) against C. difficile strains in planktonic and biofilm forms. The susceptibility of four strains of C. difficile to BRP was analyzed by broth microdilution method and vancomycin was included as control drug. BRP-exposed C. difficile cells were evaluated by scanning electron microscopy (SEM). Then, the effects of BRP on growing and mature C. difficile biofilms were also evaluated. BRP minimum inhibitory concentration was 625 µg/mL against all tested strains, while vancomycin MIC range was 0.5-2 µg/mL. SEM showed the loss of homogeneity in bacterial cell wall and cell fragmentation, after BRP-exposure. BRP, at MIC, reduced (P < 0.05) the biomass, matrix proteins and matrix carbohydrates of growing biofilms, and, at 8xMIC, reduced (P < 0.05) the biomass and matrix proteins of mature biofilms. The present study demonstrated that BRP inhibits planktonic growth, damages cell wall, decreases biofilm growth and harms mature biofilms of C. difficile.