Optimal turnaround time for direct identification of microorganisms by mass spectrometry in blood culture.

INTRODUCTION: During the past few years, several studies describing direct identification of bacteria from blood culture using mass spectrometry have been published. These methods cannot, however, be easily integrated into a common laboratory workflow because of the high hands-on time they require. In this paper, we propose a new method of identification with a short hands-on time and a turnaround time shorter than 15min. MATERIALS AND METHODS: Positive blood bottles were homogenised and 600µL of blood were transferred to an Eppendorf tube where 600µL of lysis buffer were added. After homogenisation, a centrifugation step of 4min at 10,500g was performed and the supernatant was discarded. The pellet was then washed and loaded in quadruplicate into wells of a Vitek® MS-DS plate. Each well was covered with a saturated matrix solution and a MALDI-TOF mass spectrometry analysis was performed. Species were identified using the software Myla 3.2.0-2. RESULTS: We analysed 266 positive blood culture bottles. A microorganism grew in 261 cultures, while five bottles remained sterile after 48h of incubation in subculture. Our method reaches a probability of detection at the species level of 77.8% (203/261) with a positive predictive value of 99.5% (202/203). CONCLUSION: We developed a new method for the identification of microorganisms using mass spectrometry, directly performed from a positive blood culture. This method has short hands-on time and turnaround time and can easily take place in the workflow of a laboratory, with comparable results in performance with other methods reported in the literature.

Endoxifen levels and its association with CYP2D6 genotype and phenotype: evaluation of a southern Brazilian population under tamoxifen pharmacotherapy.

BACKGROUND: An association between CYP2D6 variation and clinical outcomes among women with breast cancer treated with tamoxifen (TAM) has been demonstrated, such that the presence of 2 functional CYP2D6 alleles was associated with better clinical outcomes. This association is mainly due to the CYP2D6-mediated hydroxylation of N-desmethyltamoxifen (NDT) to yield endoxifen (EDF), which because of its high antiestrogenic potency, is mainly responsible for the therapeutic efficacy of TAM. The aim of this study was to evaluate the relation of CYP2D6 genotyping and phenotyping with EDF levels and [NDT]/[EDF] metabolic ratio in breast cancer patients from South of Brazil under TAM therapy. METHODS: Trough blood samples were collected from 97 patients. CYP2D6 genotyping was performed with a luminex assay and calculation of genotypic activity scores. Tamoxifen and metabolites EDF, NDT, and 4-hydroxy-TAM were measured in plasma by high performance liquid chromatography with photo diode array detector. CYP2D6 phenotyping was performed by the determination of dextromethorphan (DMT) and dextrorphan (DTF) by high-performance liquid chromatography with fluorescence detection at plasma collected 3 hours after oral administration of 33 mg of DMF. Phenotypes were given according to [DMT]/[DTF] metabolic ratio. RESULTS: CYP2D6 genotyping indicated a prevalence of 4.1% poor metabolizer, 4.1% intermediate metabolizer, 49.5% extensive metabolizer slow activity, 39.2% extensive metabolizer fast activity, and 3.1% ultrarapid metabolizer. Genotype (genotypic activity scores) was significantly correlated with phenotype ([DMT]/[DTF]), with a moderate association (rs = -0.463; P < 0.001). Median plasma concentrations (nanograms per milliliter; N = 97) were TAM 57.17; 4-hydroxy-TAM 1.01; EDF 6.21; NDT 125.50. EDF levels were lower in poor metabolizers than that in extensive metabolizers (P < 0.05). Phenotype showed stronger, but still moderate, association with EDF and [NDT]/[EDF] than genotype (r = -0.507, r = 0.625, P < 0.001 versus r = 0.356, r = 0.516, P < 0.01). Phenotype accounted for 26% of the variability in EDF levels and 38% of [NDT]/[EDF], whereas genotype accounted for 12% and 27%, respectively. CONCLUSIONS: CYP2D6 genotyping and/or phenotyping could not fully predict EDF concentrations. Monitoring EDF itself could be considered during TAM therapy.

Severe acute cardiomyopathy associated with venlafaxine overdose and possible role of CYP2D6 and CYP2C19 polymorphisms.

INTRODUCTION: Venlafaxine (VEN) is a serotonin-norepinephrine-dopamine reuptake inhibitor that causes usually a mild cardiotoxicity when ingested in overdose. We report a patient who developed acute heart failure following overdose. As the toxicokinetic data suggested a prolonged metabolism, genetic polymorphisms for cytochrome P450 isoenzymes CYP2D6 and CYP2C19 were also investigated. CASE REPORT: A 34-year-old woman was admitted to the hospital 10 hours after the ingestion of an 11.25 g overdose of VEN. She was comatose and suffered two self-limited seizures. The electrocardiogram showed diffuse ST segment depression, but normal QRS and QTc duration. The plasma levels on admission were 18,015 and 3,846 ng/ml for VEN and the metabolite O-desmethylvenlafaxine (ODV), respectively. The patient developed severe cardiodepression. The left ventricular shortening fraction was only 9% on echocardiography. The patient was oliguric and required continuous venovenous hemofiltration. The administration of milrinone was required for 12 days, and norepinephrine for 10 days. Left ventricular function recovered. The calculated elimination half-life was 30.8 and 72.2 hours for VEN and ODV, respectively. The patient genotype was CYP2D6*1/*5, the *5 allele corresponding to a complete deletion of CYP2D6 gene. CONCLUSIONS: Severe and sustained cardiotoxicity following VEN overdose may be related to the amount ingested, as well as to the genetic polymorphism for CYP2D6 leading to a delayed elimination of active metabolite.

Lack of evidence of stimulatory autoantibodies to platelet-derived growth factor receptor in patients with systemic sclerosis.

OBJECTIVE: Systemic sclerosis (SSc) is a severe connective tissue disease of unknown etiology, characterized by fibrosis of the skin and multiple internal organs. Recent findings suggested that the disease is driven by stimulatory autoantibodies to platelet-derived growth factor receptor (PDGFR), which stimulate the production of reactive oxygen species (ROS) and collagen by fibroblasts. These results opened novel avenues of research into the diagnosis and treatment of SSc. The present study was undertaken to confirm the presence of anti-PDGFR antibodies in patients with SSc. METHODS: Immunoglobulins from 37 patients with SSc were purified by protein A/G chromatography. PDGFR activation was tested using 4 different sensitive bioassays, i.e., cell proliferation, ROS production, signal transduction, and receptor phosphorylation; the latter was also tested in a separate population of 7 patients with SSc from a different research center. RESULTS: Purified IgG samples from patients with SSc were positive when tested for antinuclear autoantibodies, but did not specifically activate PDGFRalpha or PDGFRbeta in any of the tests. Cell stimulation with PDGF itself consistently produced a strong signal. CONCLUSION: The present results raise questions regarding the existence of agonistic autoantibodies to PDGFR in SSc.