Veronique Stove

Meropenem and piperacillin/tazobactam prescribing in critically ill patients: Does augmented renal clearance affect pharmacokinetic/pharmacodynamic target attainment when extended infusions are used?

BackgroundCorrect antibiotic dosing remains a challenge for the clinician. The aim of this study was to assess the influence of augmented renal clearance on pharmacokinetic/pharmacodynamic target attainment in critically ill patients receiving meropenem or piperacillin/tazobactam, administered as an extended infusion.MethodsThis was a prospective, observational, pharmacokinetic study executed at the medical and surgical intensive care unit at a large academic medical center. Elegible patients were adult patients without renal dysfunction receiving meropenem or piperacillin/tazobactam as an extended infusion. Serial blood samples were collected to describe the antibiotic pharmacokinetics. Urine samples were taken from a 24-hour collection to measure creatinine clearance. Relevant data were drawn from the electronic patient file and the intensive care information system.ResultsWe obtained data from 61 patients and observed extensive pharmacokinetic variability. Forty-eight percent of the patients did not achieve the desired pharmacokinetic/pharmacodynamic target (100% f T>MIC), of which almost 80% had a measured creatinine clearance >130 mL/min. Multivariate logistic regression demonstrated that high creatinine clearance was an independent predictor of not achieving the pharmacokinetic/pharmacodynamic target. Seven out of nineteen patients (37%) displaying a creatinine clearance >130 mL/min did not achieve the minimum pharmacokinetic/pharmacodynamic target of 50% f T>MIC.ConclusionsIn this large patient cohort, we observed significant variability in pharmacokinetic/pharmacodynamic target attainment in critically ill patients. A large proportion of the patients without renal dysfunction, most of whom displayed a creatinine clearance >130 mL/min, did not achieve the desired pharmacokinetic/pharmacodynamic target, even with the use of alternative administration methods. Consequently, these patients may be at risk for treatment failure without dose up-titration.

P-Cadherin Promotes Cell-Cell Adhesion and Counteracts Invasion in Human Melanoma

Malignant transformation of melanocytes frequently coincides with alterations in epithelial cadherin (E-cadherin) expression, switching on of neural cadherin (N-cadherin), and, when progressed to a metastatic stage, loss of membranous placental cadherin (P-cadherin). In vitro studies of melanoma cell lines have shown invasion suppressor and promoter roles for E-cadherin and N-cadherin, respectively. In the present study, we investigated the effect of P-cadherin on aggregation and invasion using melanoma cells retrovirally transduced with human P-cadherin. De novo expression of P-cadherin in P-cadherin-negative cell lines (BLM and HMB2) promoted cell-cell contacts and Ca2+-dependent cell-cell aggregation in two- and three-dimensional cultures, whereas it counteracted invasion. These effects were not observed following P-cadherin transduction of endogenously P-cadherin-positive MeWo cells. In addition, P-cadherin-transduced BLM cells coaggregated with keratinocytes and showed markedly reduced invasion in a reconstructed skin model. The proadhesive and anti-invasive effects of P-cadherin were abolished on targeted mutation of its intracellular juxtamembrane domain or its extracellular domain. For the latter mutation, we mimicked a known missense mutation in P-cadherin (R503H), which is associated with congenital hypotrichosis with juvenile macular dystrophy.

P-Cadherin Is Up-Regulated by the Antiestrogen ICI 182,780 and Promotes Invasion of Human Breast Cancer Cells

P-cadherin expression in breast carcinomas has been associated with tumors of high histologic grade and lacking estrogen receptor-α, suggesting a link between these proteins. In the MCF-7/AZ breast cancer cell line, blocking estrogen receptor-α signaling with the antiestrogen ICI 182,780 induced an increase of P-cadherin, which coincided with induction of in vitro invasion. Retroviral transduction of MCF-7/AZ cells, as well as HEK 293T cells, showed the proinvasive activity of P-cadherin, which requires the juxtamembrane domain of its cytoplasmic tail. This study establishes a direct link between P-cadherin expression and the lack of estrogen receptor-α signaling in breast cancer cells and suggests a role for P-cadherin in invasion, through its interaction with proteins bound to the juxtamembrane domain.

Human Immunodeficiency Virus Nef Induces Rapid Internalization of the T-Cell Coreceptor CD8αβ

ABSTRACT Human immunodeficiency virus (HIV) Nef is a membrane-associated protein decreasing surface expression of CD4, CD28, and major histocompatibility complex class I on infected cells. We report that Nef strongly down-modulates surface expression of the β-chain of the CD8αβ receptor by accelerated endocytosis, while CD8 α-chain expression is less affected. By mutational analysis of the cytoplasmic tail of the CD8 β-chain, an FMK amino acid motif was shown to be critical for Nef-induced endocytosis. Although independent of CD4, endocytosis of the CD8 β-chain was abrogated by the same mutations in Nef that affect CD4 down-regulation, suggesting common molecular interactions. The ability to down-regulate the human CD8 β-chain was conserved in HIV-1, HIV-2, and simian immunodeficiency virus SIVmac239 Nef and required an intact AP-2 complex. The Nef-mediated internalization of receptors, such as CD4, major histocompatibility complex class I, CD28, and CD8αβ, may contribute to the subversion of the host immune system and progression towards AIDS.

Quantification of seven β-lactam antibiotics and two β-lactamase inhibitors in human plasma using a validated UPLC-MS/MS method

There is an increasing interest in monitoring plasma concentrations of β-lactam antibiotics. The objective of this work was to develop and validate a rapid ultra-performance liquid chromatographic method with tandem mass spectrometric detection (UPLC-MS/MS) for simultaneous quantification of amoxicillin, ampicillin, cefuroxime, cefazolin, ceftazidime, meropenem, piperacillin, clavulanic acid and tazobactam. Sample clean-up included protein precipitation with acetonitrile and back-extraction of acetonitrile with dichloromethane. Six deuterated β-lactam antibiotics were used as internal standards. Chromatographic separation was performed on a Waters ACQUITY UPLC system using a BEH C(18) column (1.7 μm, 100 mm×2.1 mm) applying a binary gradient elution of water and acetonitrile both containing 0.1% formic acid. The total run time was 5.5 min. The developed method was validated in terms of precision, accuracy, linearity, matrix effect and recovery. The assay has now been successfully used to determine concentrations of amoxicillin/clavulanic acid, cefuroxime and meropenem in plasma samples from intensive care patients.

Soluble N‐cadherin in human biological fluids

Classical cadherins such as E‐, P‐ and N‐cadherin are transmembrane proteins that mediate cell–cell adhesion, and are important in embryogenesis, maintenance of tissue integrity and cancer. Proteolytic shedding of the extracellular domain results in the generation of soluble E‐, P‐ or N‐cadherin ectodomains. Circulating soluble E‐ and P‐cadherin have been described in the serum, and elevated levels were detected in cancer patients when compared with healthy persons. Here we report the presence of soluble N‐cadherin, a 90‐kD protein fragment, in the serum of both healthy persons and cancer patients, using a direct ELISA and immunoprecipitation. A correlation was found between prostate specific antigen and soluble N‐cadherin, and significantly elevated levels were detected in prostate cancer follow‐up patients. The N‐cadherin protein is neo‐expressed by carcinomas of the prostate, and is responsible for epithelial to fibroblastic transition. This is reflected by the higher concentrations of soluble N‐cadherin in prostate cancer patients than in healthy persons.

Glomerular Filtration Rate Is a Confounder for the Measurement of Soluble Mesothelin in Serum

The mesothelin gene encodes a 71-kDa precursor protein that is subsequently cleaved into a soluble megakaryocyte potentiating factor and a membrane-bound part, mesothelin. Mesothelin can be shed as “soluble mesothelin” or “soluble mesothelin-related protein” (SMRP),1 which is an approximately 40-kDa biomarker of malignant mesothelioma, an asbestos-related cancer (1). Mesothelioma typically occurs in middle-aged men, and the renal function or the glomerular filtration rate (GFR) can occasionally decrease in these patients and in individuals at risk of developing mesothelioma. Renal impairment leads to the accumulation of low molecular weight proteins in the blood [e.g., cystatin C (13 kDa) and β-trace protein (BTP) (23–29 kDa)], and these proteins have been used as markers of the GFR. Such renal impairment can also cause the accumulation of soluble mesothelin, as has previously been reported for a limited number of cases(2). Our aim, therefore, was to thoroughly investigate the impact of renal function on serum SMRP concentrations. We enrolled 66 individuals (49 men and 17 women; median age, 58 years; range, 24–80 years), who were referred for measurement of 51Cr-EDTA clearance to estimate the GFR. We excluded patients with asbestos-related diseases/malignancies, patients with endometrial, ovarian, cervix, lung, breast, pancreatic, or gastrointestinal cancer, and patients with leukemia, because these conditions can overexpress mesothelin (3)(4). The study was approved by the ethics committee of both participating hospitals, and participants gave written informed consent. …

Assays for therapeutic drug monitoring of β-lactam antibiotics: A structured review

In some patient groups, including critically ill patients, the pharmacokinetics of β-lactam antibiotics may be profoundly disturbed due to pathophysiological changes in distribution and elimination. Therapeutic drug monitoring (TDM) is a strategy that may help to optimise dosing. The aim of this review was to identify and analyse the published literature on the methods used for β-lactam quantification in TDM programmes. Sixteen reports described methods for the simultaneous determination of three or more β-lactam antibiotics in plasma/serum. Measurement of these antibiotics, due to low frequency of usage relative to some other tests, is generally limited to in-house chromatographic methods coupled to ultraviolet or mass spectrometric detection. Although many published methods state they are fit for TDM, they are inconvenient because of intensive sample preparation and/or long run times. Ideally, methods used for routine TDM should have a short turnaround time (fast run-time and fast sample preparation), a low limit of quantification and a sufficiently high upper limit of quantification. The published assays included a median of 6 analytes [interquartile range (IQR) 4-10], with meropenem and piperacillin being the most frequently measured β-lactam antibiotics. The median run time was 8 min (IQR 5.9-21.3 min). There is also a growing number of methods measuring free concentrations. An assay that measures antibiotics without any sample preparation would be the next step towards real-time monitoring; no such method is currently available.

Variability in protein binding of teicoplanin and achievement of therapeutic drug monitoring targets in critically ill patients: Lessons from the DALI Study

The aims of this study were to describe the variability in protein binding of teicoplanin in critically ill patients as well as the number of patients achieving therapeutic target concentrations. This report is part of the multinational pharmacokinetic DALI Study. Patients were sampled on a single day, with blood samples taken both at the midpoint and the end of the dosing interval. Total and unbound teicoplanin concentrations were assayed using validated chromatographic methods. The lower therapeutic range of teicoplanin was defined as total trough concentrations from 10 to 20 mg/L and the higher range as 10-30 mg/L. Thirteen critically ill patients were available for analysis. The following are the median (interquartile range) total and free concentrations (mg/L): midpoint, total 13.6 (11.2-26.0) and free 1.5 (0.7-2.5); trough, total 11.9 (10.2-22.7) and free 1.8 (0.6-2.6). The percentage free teicoplanin for the mid-dose and trough time points was 6.9% (4.5-15.6%) and 8.2% (5.5-16.4%), respectively. The correlation between total and free antibiotic concentrations was moderate for both the midpoint (ρ = 0.79, P = 0.0021) and trough (ρ = 0.63, P = 0.027). Only 42% and 58% of patients were in the lower and higher therapeutic ranges, respectively. In conclusion, use of standard dosing for teicoplanin leads to inappropriate concentrations in a high proportion of critically ill patients. Variability in teicoplanin protein binding is very high, placing significant doubt on the validity of total concentrations for therapeutic drug monitoring in critically ill patients.

Erythrocyte Indices in the Assessment of Iron Status in Dialysis-Dependent Patients with End-Stage Renal Disease on Continuous Erythropoietin Receptor Activator versus Epoetin β Therapy

Background: European guidelines stress that iron status should be regularly assessed for the optimal management of renal anemia. These guidelines include the hemoglobin content of reticulocytes and the percentage of hypochromic RBC as markers for functional iron deficiency. Recently, equivalents of these indices have become available on the automated hematology analyzer Sysmex XE-2100, these being reticulocyte hemoglobin equivalent (Ret-He) and DF-HYPO XE, respectively. Methods: In a prospective study, we closely monitored these parameters in dialysis-dependent patients with end-stage renal disease during the switch from a first-generation epoetin (EPO) once weekly to a third-generation EPO [continuous erythropoietin receptor activator (CERA)] once monthly. As a control, patients staying on EPO β were monitored. Results: During follow-up, no changes in erythrocyte indices were noticed in the EPO β group. By contrast, in the CERA group, a decrease in Ret-He and an increase in DF-HYPO XE were transiently found 7–10 days after administration. The transient state of functional iron deficiency could not be prevented by extra intravenous iron. Conclusion: Fluctuations in Ret-He and DF-HYPO XE have to be taken into account when these parameters are used for the assessment of iron-deficient states. We suggest that a fixed time point in the CERA schedule should be chosen for iron monitoring.