Beta-Lactam Antibiotics Can Be Measured in the Exhaled Breath Condensate in Mechanically Ventilated Patients: A Pilot Study.

Different techniques have been proposed to measure antibiotic levels within the lung parenchyma; however, their use is limited because they are invasive and associated with adverse effects. We explore whether beta-lactam antibiotics could be measured in exhaled breath condensate collected from heat and moisture exchange filters (HMEFs) and correlated with the concentration of antibiotics measured from bronchoalveolar lavage (BAL). We designed an observational study in patients undergoing mechanical ventilation, which required a BAL to confirm or discard the diagnosis of pneumonia. We measured and correlated the concentration of beta-lactam antibiotics in plasma, epithelial lining fluid (ELF), and exhaled breath condensate collected from HMEFs. We studied 12 patients, and we detected the presence of antibiotics in plasma, ELF, and HMEFs from every patient studied. The concentrations of antibiotics were very heterogeneous over the population studied. The mean antibiotic concentration was 293.5 (715) ng/mL in plasma, 12.3 (31) ng/mL in ELF, and 0.5 (0.9) ng/mL in HMEF. We found no significant correlation between the concentration of antibiotics in plasma and ELF (R2 = 0.02, p = 0.64), between plasma and HMEF (R2 = 0.02, p = 0.63), or between ELF and HMEF (R2 = 0.02, p = 0.66). We conclude that beta-lactam antibiotics can be detected and measured from the exhaled breath condensate accumulated in the HMEF from mechanically ventilated patients. However, no correlations were observed between the antibiotic concentrations in HMEF with either plasma or ELF.

Plasma and Renal Cortex Meropenem Concentrations in Patients Undergoing Percutaneous Renal Biopsy.

BACKGROUND: Urinary tract infection (UTI) is the most common bacterial infection in the world. Some cases can have serious complication as death by septic shock. With the increasing spread of multidrug-resistant bacteria, the therapeutic possibilities against the complicated UTI are exhausted, forcing the use of broad-spectrum antibiotics such as meropenem. OBJECTIVES: To evaluate the penetrating ability of meropenem to renal tissue using an enzymatic biosensor in samples of renal cortex and its correlation with plasma levels. METHOD: We conducted a descriptive study in humans with indication of kidney biopsy. Meropenem was administered 1 hour before performing the biopsy, and the concentrations of meropenem in a series of samples of plasma and renal biopsy were determined. RESULTS: Renal biopsy and plasma samples of 14 patients, 64% women with body mass index of 26.3 kg/m2 (SD ± 2.9) and estimated glomerular filtration rate of 57.5 mL/min/1.73 m2 (SD ± 44.1), were examined. Renal biopsy was done at 68.9 minutes (SD ± 20.3), and the second plasma sample was obtained at 82.1 minutes (SD ± 21.2) and the third at 149.6 minutes (SD ± 31.5). The mean kidney meropenem concentration was 3.1 µg/mL (SD ± 1.9). For each patient, a decay curve of plasma meropenem concentration was constructed. The proportion of meropenem concentrations in renal tissue and plasma at biopsy moment was 14% (SD ± 10) with an interquartile range of 5.5-20.3%. With normal renal function, meropenem can achieve a bactericidal effect towards bacteria with MIC-90 < 0.76 µg/mL in the renal parenchyma. CONCLUSIONS: Meropenem is effective to treat the most frequent uropathogens with the bactericidal effect. Nevertheless, for resistant bacteria, it is necessary to adjust the dose to achieve adequate parenchymal concentration.

Effect of Lactamase Inhibitors on the Biosensor Penp during the Measurement of Lactam Antibiotics Concentration.

PenP is a fluorescent biosensor of lactam antibiotics (LA). It is structurally derived from the mutant lactamase TEM-1 comprising the substitution E166C, where fluorescein is covalently linked to cysteine. The presence of LA in the medium produces a change in the intrinsic fluorescence level of the biosensor, and the integral of the fluorescence level over time correlates directly with the LA concentration. Previously, we have successfully used PenP to determine the concentration of lactam antibiotics in clinical samples. The use of lactamase inhibitors (LI) is a common strategy to enhance the effect of LA due to the inhibition of an important resistance mechanism of pathogenic microorganisms. Structurally, LI and LA share the common element of recognition of lactamases (the lactam ring), but they differ in the reversibility of the mechanism of interaction with said enzyme. Because the biological recognition domain of PenP is derived from a lactamase, LI is expected to interfere with the PenP detection capabilities. Surprisingly, this work provides evidence that the effect of LI is marginal in the determination of LA concentration mediated by PenP.

Evaluation of Meropenem Pharmacokinetics in an Experimental Acute Respiratory Distress Syndrome (ARDS) Model during Extracorporeal Membrane Oxygenation (ECMO) by Using a PenP ß-Lactamase Biosensor.

INTRODUCTION: The use of antibiotics is mandatory in patients during extracorporeal membrane oxygenation (ECMO) support. Clinical studies have shown high variability in the antibiotic concentrations, as well as sequestration of them by the ECMO circuit, suggesting that the doses and/or interval administration used during ECMO may not be adequate. Thus, a fast response sensor to estimate antibiotic concentrations in this setting would contribute to improve dose adjustments. The biosensor PenP has been shown to have a dynamic range, sensitivity and specificity useful for pharmacokinetic (PK) tests in healthy subjects. However, the use of this biosensor in the context of a complex critical condition, such as ECMO during acute respiratory distress syndrome (ARDS), has not been tested. OBJECTIVES: To describe, by using PenP Biosensor, the pharmacokinetic of meropenem in a 24-h animal ARDS/ECMO model. METHODS: The PK of meropenem was evaluated in a swine model before and during ECMO. RESULTS: The PK parameters such as maximum concentration (Cmax), elimination rate constant (Ke), and cleareance (Cl), were not significantly altered during ECMO support. CONCLUSIONS: (a) ECMO does not affect the PK of meropenem, at least during the first 24 h; and (b) PenP has the potential to become an effective tool for making medical decisions associated with the dose model of antibiotics in a critical patient context.

Method Based on the ß-Lactamase PenPC Fluorescent Labeled for ß-Lactam Antibiotic Quantification in Human Plasma.

Recently, Wong et al. have successfully developed a fluorescent biosensor based on the PenPC ß-lactamase which changes its intrinsic fluorescence in presence of ß-lactam antibiotics (BLAs). Here, we studied systematically this correlation among the fluorescence change of the biosensor and the concentration of different BLAs aimed at developing a novel method for estimating the concentration of a wide range of BLAs. This method showed high precision and specificity and very low interference from clinically relevant samples. We were able to monitor the pharmacokinetics of meropenem in healthy volunteers as well as in an ill animal model too, indicating that the implemented method could be suitable for clinical practice.

[Therapeutic monitoring of antibiotics: New methodologies: biosensors]. / Monitorización terapéutica de antibióticos: Nuevas metodologías: biosensores.

The pharmacokinetics of antibiotics, especially in severely ill patients, may be profoundly altered due to multiple pathophysiological changes. Recent studies have shown that empiric dosing recommendations for ICU patients are inadequate to effectively treat a broad range of susceptible organisms and need to be reconsidered. Therapeutic drug monitoring (TDM) is an important mean for optimizing drug utilization and doses for the purpose of improving the clinical effectiveness. However, it is very challenging to quantify plasma antibiotic concentrations in clinical situations as a routine practice, because of the high costs and complexities associated with advanced instrumental techniques. Currently there are not routine and low cost methods to determine the presence and concentration of ß-lactam antibiotics in plasma patients in a clinical setup. Indeed, such analytical methods are based on chromatographic techniques mainly used in research. Here we describe and comment different techniques, focusing on our preliminary experience using biosensors.