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Background: Treatment of multidrug-resistant (MDR) tuberculosis with linezolid is characterized by high rates of adverse events. Evidence on therapeutic drug monitoring to predict drug toxicity is scarce. This study aimed to evaluate the association of linezolid trough concentrations with severe toxicity., Methods: We retrospectively assessed consecutive patients started on linezolid for MDR tuberculosis between 2011 and 2017. The primary outcome was severe mitochondrial toxicity (SMT) due to linezolid, defined as neurotoxicity or myelotoxicity leading to drug discontinuation. The impact of plasma linezolid trough concentrations >2 mg/L was assessed in multivariate Cox proportional hazards models including time-varying covariates., Results: SMT occurred in 57 of 146 included patients (39%) at an incidence rate of 0.38 per person-year (95% confidence interval, .30-.49). A maximum linezolid trough concentration >2 mg/L was detected in 52 patients (35.6%), while the mean trough concentration was >2 mg/L in 22 (15%). The adjusted hazard ratio for SMT was 2.35 (95% confidence interval, 1.26-4.38; P = .01) in patients with a mean trough concentration >2 mg/L and 2.63 (1.55-4.47; P < .01) for SMT after the first detection of a trough concentration >2 mg/L. In an exploratory analysis, higher maximum trough concentrations were dose-dependently associated with toxicity, while lowering elevated trough concentrations did not restore baseline risk., Conclusions: Linezolid trough concentrations >2 mg/L are strongly associated with the development of severe treatment-emergent toxicity in patients treated for MDR tuberculosis. Pending further prospective evidence, an individual risk-benefit assessment on the continuation of linezolid treatment is warranted in any patient with trough concentrations >2 mg/L., Competing Interests: Potential conflicts of interest. M. F. J. serves on the safety boards of the endTB (NCT 02754765) and endTB-Q (NCT 03896685) trials and has participated in prospective infectious sample collection for a study on tools for tuberculosis diagnosis (reference no. 18.12.27. 42115 for Cerba Xpert France). L. G. is a principal investigator in the aforementioned trials. G. P. has been a speaker for Gilead Sciences, Merck France, Pfizer, Takeda, Theratechnologies, and ViiV Healthcare and has received honoraria for lectures and presentations (payments to self). All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background and Objectives: Pneumococcal meningitis is a devastating disease that requires adequate meningeal antibiotic penetration to limit the mortality. Despite a large usage in this indication, data about CSF concentration of cefotaxime during pneumococcal meningitis in adults are scarce. Therefore, we aimed to describe the CSF concentration obtained after high-dose cefotaxime administration in adult patients treated for Streptococcus pneumoniae meningitis., Patients and Methods: In this multicentre, observational, retrospective study, cases of adult patients with S. pneumoniae meningitis hospitalized between January 2013 and October 2019 for whom cefotaxime concentration was measured in CSF were reviewed., Results: Cefotaxime concentration was analysed in 44 CSF samples collected among 31 patients. Median (IQR) age was 61 years (52-69). Dexamethasone was administered in 27 subjects. Median (IQR) cefotaxime daily dosage was 15 g (12-19), corresponding to 200 mg/kg (150-280). CSF samples were collected approximately 5 days after cefotaxime initiation. Median (IQR, range) cefotaxime CSF concentration was 10.3 mg/L (4.8-19.3, 1.2-43.4). Median (range) MIC for Streptococcus pneumoniae was 0.25 mg/L (0.008-1) (n = 22). The median (IQR, range) CSF/MIC ratio was 38 (12-146, 4-1844). Twenty-five CSF concentrations (81%) were above 10 times the MIC. Cefotaxime was discontinued in two patients for toxicity. In-hospital mortality rate was 29%., Conclusions: Adult patients with pneumococcal meningitis treated with a high dose of cefotaxime (200 mg/kg/day) had elevated CSF concentrations with satisfying pharmacokinetics/pharmacodynamics parameters and tolerability profile. This study brings reassuring pharmacological data regarding the use of high-dose cefotaxime monotherapy for treating pneumococcal meningitis with susceptible strains to cefotaxime., (© The Author(s) 2021. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Pneumonia, skin and soft tissue infections are more frequent in obese patients and are most often treated by co-amoxiclav, using similar dosing regimens to those used for non-obese subjects. No data are available on amoxicillin pharmacokinetics among obese subjects receiving co-amoxiclav., Materials and Methods: Prospective, single-centre, open-label, non-randomized, crossover pharmacokinetic trial having enrolled obese otherwise healthy adult subjects. A first dose of co-amoxiclav (amoxicillin/clavulanate 1000/200 mg) was infused IV over 30 min, followed by a second dose (1000/125 mg) administered orally, separated by a washout period of ≥24 h. We assayed concentrations of amoxicillin by a validated ultra HPLC-tandem MS technique. We estimated population pharmacokinetic parameters of amoxicillin by non-linear mixed-effect modelling using the SAEM algorithm developed by Monolix., Results: Twenty-seven subjects were included in the IV study, with 24 included in the oral part of the study. Median body weight and BMI were 109.3 kg and 40.6 kg/m2, respectively. Amoxicillin pharmacokinetics were best described by a two-compartment model with first-order elimination. Mean values for clearance, central volume, intercompartmental clearance and peripheral volume were, respectively, 14.6 L/h, 9.0 L, 4.2 L/h and 6.4 L for amoxicillin. Oral bioavailability of amoxicillin was 79.7%. Amoxicillin Cmax after oral administration significantly reduced with weight (P = 0.013). Dosing simulations for amoxicillin predicted that most of the population will achieve the pharmacodynamic target of fT>MIC ≥40% with the regimen of co-amoxiclav 1000/200 mg (IV) or 1000/125 mg (oral) q8h for MICs titrated up to 0.5 mg/L (IV) and 1 mg/L (oral)., Conclusions: Pharmacokinetic/pharmacodynamic goals for amoxicillin can be obtained in obese subjects., (© The Author(s) 2020. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: In infants, the mode of acquisition of CC17 group B Streptococcus (GBS), the hypervirulent clone responsible for late-onset disease (LOD), remains elusive., Methods: In a prospective multicenter study in France, we evaluated GBS colonization in mother-baby pairs with 2 months of follow-up between 2012 and 2015. Criteria included positivity for GBS colonization at antenatal screening or at delivery. Maternal vaginal samples and infant oral cavity and stool samples were analyzed at delivery, 21 ± 7 days (D21), and 60 ± 7 days (D60) post-delivery., Results: A total of 890 mother-baby pairs were analyzed. GBS colonized 7%, 21%, and 23% of the infants at birth, D21, and D60, respectively, of which 10%, 11%, and 13% were identified as CC17 GBS. Concordance between maternal and infant GBS type was 96%. At D21, the main risk factors for infant colonization by GBS were simultaneous maternal colonization of the vagina (odds ratio [OR], 4.50; 95% confidence interval [CI], 1.69-15.61) and breast milk (OR, 7.93; 95% CI, 3.81-17.14). Importantly, 38% (95% CI, 23%-56%) of infants colonized by CC17 GBS appeared colonized for the first time at D60 vs 18% (95% CI, 14%-24%; P < .049) of infants colonized by non-CC17 GBS. Multivariate analysis showed a higher risk for de novo infant colonization by CC17 at D60 than by other GBS (OR, 2.45; 95% CI, 1.02-5.88)., Conclusions: The high incidence of CC17 GBS in LOD is likely due to an enhanced post-delivery mother-to-infant transmission., (© The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Background: Moxifloxacin retains partial activity against some fluoroquinolone-resistant mutants of Mycobacterium tuberculosis . Levofloxacin is presumed to be as active as moxifloxacin against drug-susceptible tuberculosis and to have a better safety profile., Objectives: To compare the in vivo activity of levofloxacin and moxifloxacin against M. tuberculosis strains with various levels of fluoroquinolone resistance., Methods: BALB/c mice were intravenously infected with 10 6 M. tuberculosis H37Rv and three isogenic mutants: GyrA A90V, GyrB E540A and GyrB A543V. Treatment with 50 or 100 mg/kg levofloxacin and 60 or 66 mg/kg moxifloxacin was given orally every 6 h, for 4 weeks., Results: Levofloxacin 50 and 100 mg/kg q6h and moxifloxacin 60 and 66 mg/kg q6h generated AUCs in mice equivalent to those of levofloxacin 750 and 1000 mg/day and moxifloxacin 400 and 800 mg/day, respectively, in humans. Moxifloxacin 60 and 66 mg/kg q6h had bactericidal activity against strain H37Rv (MIC ≤ 0.25 mg/L) and mutants GyrB E540A and GyrB A543V (MIC = 0.5 mg/L). Against mutant GyrA A90V (MIC = 2 mg/L), moxifloxacin 60 mg/kg q6h did not prevent bacillary growth, whereas 66 mg/kg q6h had bacteriostatic activity. Levofloxacin 50 mg/kg q6h had bactericidal activity against H37Rv (MIC ≤ 0.25 mg/L) but not against the mutant strains. Levofloxacin 100 mg/kg q6h had bactericidal activity against H37Rv and mutants GyrB E540A (MIC = 0.5 mg/L) and GyrB A543V (MIC= 1 mg/L) but not against mutant GyrA A90V (MIC = 4 mg/L)., Conclusions: All mutations reduced fluoroquinolone activity, even those classified as susceptible according to phenotypic tests. High-dose levofloxacin is less effective than high-dose moxifloxacin against both fluoroquinolone-resistant and -susceptible M. tuberculosis strains in mice., (© The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objectives: Emerging evidence supports the use of therapeutic drug monitoring (TDM) of β-lactams for intensive care unit (ICU) patients to optimize drug exposure, although limited detail is available on how sites run this service in practice. This multicentre survey study was performed to describe the various approaches used for β-lactam TDM in ICUs., Methods: A questionnaire survey was developed to describe various aspects relating to the conduct of β-lactam TDM in an ICU setting. Data sought included: β-lactams chosen for TDM, inclusion criteria for selecting patients, blood sampling strategy, analytical methods, pharmacokinetic (PK)/pharmacodynamic (PD) targets and dose adjustment strategies., Results: Nine ICUs were included in this survey. Respondents were either ICU or infectious disease physicians, pharmacists or clinical pharmacologists. Piperacillin (co-formulated with tazobactam) and meropenem (100% of units surveyed) were the β-lactams most commonly subject to TDM, followed by ceftazidime (78%), ceftriaxone (43%) and cefazolin (43%). Different chromatographic and microbiological methods were used for assay of β-lactam concentrations in blood and other biological fluids (e.g. CSF). There was significant variation in the PK/PD targets (100% fT>MIC up to 100% fT>4×MIC) and dose adjustment strategies used by each of the sites., Conclusions: Large variations were found in the type of β-lactams tested, the patients selected for TDM and drug assay methods. Significant variation observed in the PK/PD targets and dose adjustment strategies used supports the need for further studies that robustly define PK/PD targets for ICU patients to ensure a greater consistency of practice for dose adjustment strategies for optimizing β-lactam dosing with TDM.

Background: Intrapartum antibiotic prophylaxis is currently given to mothers who test positive for group B streptococcus (GBS) by antenatal culture-based screening, with a risk-based approach for cases with an unknown GBS status. A rapid real-time polymerase chain reaction (PCR) assay for the detection of GBS became available recently, making intrapartum screening possible. We aimed to assess its diagnostic accuracy and to compare it with antenatal screening., Methods: We conducted a prospective study in a French hospital. All pregnant women giving birth at the maternity ward were considered for inclusion, except those with planned cesarean delivery, with delivery at <35 weeks gestation, and who received antibiotic therapy before admission. We performed GBS culture (the reference standard) and a molecular GBS test (Xpert GBS; Cepheid) on intrapartum specimens. Decisions about intrapartum antibiotic prophylaxis were based on the current GBS screening by culture at 35-37 weeks gestation., Results: We prospectively enrolled 968 pregnant women from April 2007 through March 2008. The overall molecular GBS test yield was 89.2%. Among the 863 women with available results, the molecular GBS test had a sensitivity of 98.5%, specificity of 99.6%, positive predictive value of 97.8%, and negative predictive value of 99.7%. The positive predictive value of antenatal culture for identifying colonization status at delivery was low (58.3%), whereas the negative predictive value was imperfect (92.1%)., Conclusions: This real-time PCR assay is a highly accurate test to identify intrapartum GBS carriers at point of care. This new tool could enhance the exact identification of candidates for intrapartum antibiotic prophylaxis, including women with preterm rupture of membranes or preterm labor.