Pharmacokinetics of vancomycin

Influence of konjac glucomannan and its derivatives on the oral pharmacokinetics of antimicrobial agent in antibiotics cocktails: Keep vigilant on dietary fiber supplement

In this study, konjac glucomannan (KGM) and its derivatives were gavaged as dietary fiber supplements, followed by a single dose of antibiotic cocktail (Abx) containing amoxicillin, neomycin, metronidazole and vancomycin in mice. The effects of dietary fiber on the pharmacokinetics and tissue distribution of each antibiotic were investigated. The results showed that the specific effects of KGM and its derivatives on the absorption, distribution, and elimination of certain antibiotics varied and depended on the nature of the fibers and the characteristics of the antibiotics. Explicitly, the ingestion of KGM and its derivatives enhanced the absorption of metronidazole by 1.7 times and hindered that of amoxicillin by nearly 36 % without affecting the absorption of neomycin sulfate and vancomycin. KGM and its derivatives had no effect on the distribution of amoxicillin and metronidazole, but DKGM and KGM hindered the distributions of neomycin sulfate (from 1.25 h to 1.62 h) and vancomycin (from 0.95 h to 1.14 h), respectively. KGM and its derivatives promoted the elimination of amoxicillin by nearly 38 % while prolonging that of metronidazole by >50 %. KOGM boosted the elimination of neomycin sulfate and vancomycin, but KGM differed from DKGM in acting on the elimination of both.

Model-informed precision dosing in vancomycin treatment

Introduction: While vancomycin remains a widely prescribed antibiotic, it can cause ototoxicity and nephrotoxicity, both of which are concentration-associated. Overtreatment can occur when the treatment lasts for an unnecessarily long time. Using a model-informed precision dosing scheme, this study aims to develop a population pharmacokinetic (PK) and pharmacodynamic (PD) model for vancomycin to determine the optimal dosage regimen and treatment duration in order to avoid drug-induced toxicity. Methods: The data were obtained from electronic medical records of 542 patients, including 40 children, and were analyzed using NONMEM software. For PK, vancomycin concentrations were described with a two-compartment model incorporating allometry scaling. Results and discussion: This revealed that systemic clearance decreased with creatinine and blood urea nitrogen levels, history of diabetes and renal diseases, and further decreased in women. On the other hand, the central volume of distribution increased with age. For PD, C-reactive protein (CRP) plasma concentrations were described by transit compartments and were found to decrease with the presence of pneumonia. Simulations demonstrated that, given the model informed optimal doses, peak and trough concentrations as well as the area under the concentration-time curve remained within the therapeutic range, even at doses smaller than routine doses, for most patients. Additionally, CRP levels decreased more rapidly with the higher dose starting from 10 days after treatment initiation. The developed R Shiny application efficiently visualized the time courses of vancomycin and CRP concentrations, indicating its applicability in designing optimal treatment schemes simply based on visual inspection.

A Rare Case of Chronic Photophobia Associated With Oral Vancomycin Therapy: Exploring the Relationship

Vancomycin is a widely used tricyclic glycopeptide antibiotic for treating various Gram-positive infections, including Clostridium difficile colitis. Although considered generally safe, it has been associated with several side effects. In this case report, we highlight a rare adverse effect in which a patient experienced chronic photophobia following treatment with oral vancomycin. This sheds light upon a potential relationship between oral vancomycin therapy and photophobia, emphasizing the need for increased awareness in clinical practice and urging further investigation into this association.

Devlin S, Gomes ALC, Moore G, Slingerland J, Shouval R, Armijo GK, DeWolf S, Fei T, Clurman A, Fontana E, Amoretti LA, Wright RJ, Andrlova H, Miltiadous O, Perales MA, Taur Y, Peled JU, van den Brink MRM. Preservation of the fecal microbiome is associated with reduced severity of graft-versus-host disease

Following allogeneic hematopoietic cell transplantation (allo-HCT), the gastrointestinal (GI) tract is frequently affected by acute graft-versus-host disease (aGVHD), the pathophysiology of which is associated with a dysbiotic microbiome. Since microbial composition varies along the length of the GI tract, the authors hypothesized that microbiome features correlate with the pattern of organ involvement after allo-HCT. We evaluated 266 allo-HCT recipients from whom 1303 stool samples were profiled by 16S ribosomal gene sequencing. Patients were classified according to which organs were affected by aGVHD. In the 20 days prior to disease onset, GVHD patients had lower abundances of members of the class Clostridia, lower counts of butyrate producers, and lower ratios of strict-to-facultative (S/F) anaerobic bacteria compared with allograft recipients who were free of GVHD. GI GVHD patients showed significant reduction in microbial diversity preonset. Patients with lower GI aGVHD had lower S/F anaerobe ratios compared with those with isolated upper GI aGVHD. In the 20 days after disease onset, dysbiosis was observed only in GVHD patients with GI involvement, particularly those with lower-tract disease. Importantly, Clostridial and butyrate-producer abundance as well as S/F anaerobe ratio were predictors of longer overall survival; higher abundance of butyrate producers and higher S/F anaerobe ratio were associated with decreased risk of GVHD-related death. These findings suggest that the intestinal microbiome can serve as a biomarker for outcomes of allo-HCT patients with GVHD.

A review of recent advances in the treatment of adults with complicated urinary tract infection

INTRODUCTION

Complicated urinary tract infections (cUTIs) entail diverse clinical conditions that could be managed differently and not necessarily with premature empiric therapy. Since multidrug-resistant organisms (MDROs) are widely spreading worldwide, the possibility of encountering these resistant bacteria is inevitably part of the daily life of physicians who manage cUTIs.

AREAS COVERED

The advances in the management of cUTIs are explored, illustrating: 1) a proposed therapeutical approach to cUTIs within the antimicrobial stewardship context; 2) evidence regarding novel antibiotics targeting MDROs. Evidence research has been performed through MEDLINE/PubMed using appropriate keywords and terms regarding cUTIs published before June 2022.

EXPERT OPINION

Novel antimicrobial drugs are available in the clinicians' armamentarium. Selecting the optimal therapy for suitable patients may be challenging given the multifaceted group of cUTIs. Carbapenems use is widely increasing, the role of old β-lactam/β-lactamase inhibitors is constantly revised, and novel drugs lack real-life studies. Understanding the different ranges of the complexity of patients affected by cUTIs may help select the most suitable antibiotic for every single case. More multicentric observational studies targeting cUTIs are needed to elucidate the appropriate drug based on patient characteristics and presentations, providing stronger recommendations for cases encountered in everyday clinical practice.

Recent Advances in the Development of Semisynthetic Glycopeptide Antibiotics: 2014-2022

The accelerated appearance of drug-resistant bacteria poses an ever-growing threat to modern medicine's capacity to fight infectious diseases. Gram-positive species such as methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pneumoniae continue to contribute significantly to the global burden of antimicrobial resistance. For decades, the treatment of serious Gram-positive infections relied upon the glycopeptide family of antibiotics, typified by vancomycin, as a last line of defense. With the emergence of vancomycin resistance, the semisynthetic glycopeptides telavancin, dalbavancin, and oritavancin were developed. The clinical use of these compounds is somewhat limited due to toxicity concerns and their unusual pharmacokinetics, highlighting the importance of developing next-generation semisynthetic glycopeptides with enhanced antibacterial activities and improved safety profiles. This Review provides an updated overview of recent advancements made in the development of novel semisynthetic glycopeptides, spanning the period from 2014 to today. A wide range of approaches are covered, encompassing innovative strategies that have delivered semisynthetic glycopeptides with potent activities against Gram-positive bacteria, including drug-resistant strains. We also address recent efforts aimed at developing targeted therapies and advances made in extending the activity of the glycopeptides toward Gram-negative organisms.

Antimicrobial safety considerations in critically ill patients: part II: focused on anti-microbial toxicities

INTRODUCTION

Antibiotic prescription is a challenging issue in critical care settings. Different pharmacokinetic and pharmacodynamic properties, polypharmacy, drug interactions, and high incidence of multidrug-resistant microorganisms in this population can influence the selection, safety, and efficacy of prescribed antibiotics.

AREAS COVERED

In the current article we searched PubMed, Scopus and Google Scholar for neurotoxicities, hematologic toxicity and fluid stewardship in intensive care units.

EXPERT OPINION

Critically ill patients who receive antimicrobial agents should be monitored for neurological, hematologic toxicities especially seizure, thrombocytopenia, and clostridioides infections. Other toxicities including QTc prolongation, electrolyte disturbances, liver enzyme elevation, and infusion-related reactions were being considered. Other changes, including fluid overload, hypoalbuminemia, augmented renal clearance, increased cardiac outputs in septic shock, and acute kidney injury, may influence treatment efficiency and patient outcome.

Population Pharmacokinetics of Vancomycin in Pregnant Women

Objective: Vancomycin is a glycopeptide antibacterial indicated for serious gram-positive infections. Pharmacokinetics (PK) of vancomycin have not been described in pregnant women. This study aims to characterize the PK disposition of vancomycin in pregnant women based on data acquired from a database of routine hospital care for therapeutic drug monitoring to better inform dosing decisions.

Methods: In this study, plasma drug concentration data from 34 pregnant hospitalized women who were administered intravenous vancomycin was analyzed. A population pharmacokinetic (PPK) model was developed using non-linear mixed effects modeling. Model selection was based on statistical criterion, graphical analysis, and physiologic relevance. Using the final model AUC_0-24 (PK efficacy index of vancomycin) was compared with non-pregnant population.

Results: Vancomycin PK in pregnant women were best described by a two-compartment model with first-order elimination and the following parameters: clearance (inter individual variability) of 7.64 L/hr (32%), central volume of 67.35 L, inter-compartmental clearance of 9.06 L/h, and peripheral volume of 37.5 L in a typical patient with 175 ml/min creatinine clearance (CRCL) and 45 kg fat-free mass (FFM). The calculated geometric mean of AUC_0-24 for the pregnant population was 223 ug.h/ ml and 226 ug.h/ ml for the non-pregnant population.

Conclusion: Our analysis suggests that vancomycin PK in pregnant women is consistent with non-pregnant adults and the dosing regimens used for non-pregnant patients may also be applicable to pregnant patients.

Vancomycin-Loaded Microneedle Arrays against Methicillin-Resistant Staphylococcus Aureus Skin Infections

Skin and soft tissue infections (SSTIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major healthcare burden, often treated with intravenous injection of the glycopeptide antibiotic vancomycin (VAN). However, low local drug concentration in the skin limits its treatment efficiency, while systemic exposure promotes the development of resistant bacterial strains. Topical administration of VAN on skin is ineffective as its high molecular weight prohibits transdermal penetration. In order to implement a local VAN delivery, microneedle (MN) arrays with a water-insoluble support layer for the controlled administration of VAN into the skin are developed. The utilization of such a support layer results in water-insoluble needle shafts surrounded by drug-loaded water-soluble tips with high drug encapsulation. The developed MN arrays can penetrate the dermal barriers of both porcine and fresh human skin. Permeation studies on porcine skin reveal that the majority of the delivered VAN is retained within the skin. It is shown that the VAN-MN array reduces MRSA growth both in vitro and ex vivo on skin. The developed VAN-MN arrays may be extended to several drugs and may facilitate localized treatment of MRSA-caused skin infections while minimizing adverse systemic effects.

Roles of Phytoestrogen in the Pathophysiology of Intracranial Aneurysm

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Targeting Internalized Staphylococcus aureus Using Vancomycin-Loaded Nanoparticles to Treat Recurrent Bloodstream Infections

The bacterial pathogen Staphylococcus aureus is a leading cause of bloodstream infections, where patients often suffer from relapse despite antibiotic therapy. Traditional anti-staphylococcal drugs display reduced effectivity against internalised bacteria, but nanoparticles conjugated with antibiotics can overcome these challenges. In the present study, we aimed to characterise the internalisation and re-emergence of S. aureus from human endothelial cells and construct a new formulation of nanoparticles that target intracellular bacteria. Using an in vitro infection model, we demonstrated that S. aureus invades and persists within endothelial cells, mediated through bacterial extracellular surface adhesion, Fibronectin-binding protein A/B. After internalising, S. aureus localises to vacuoles as determined by transmission electron microscopy. Viable S. aureus emerges from endothelial cells after 48 h, supporting the notion that intracellular persistence contributes to infection relapses during bloodstream infections. Poly lactic-co-glycolic acid nanoparticles were formulated using a water-in-oil double emulsion method, which loaded 10% vancomycin HCl with 82.85% ± 12 encapsulation efficiency. These non-toxic nanoparticles were successfully taken up by cells and demonstrated a biphasic controlled release of 91 ± 4% vancomycin. They significantly reduced S. aureus intracellular growth within infected endothelial cells, which suggests future potential applications for targeting internalised bacteria and reducing mortality associated with bacteraemia.

Peri-operative antibiotics acutely and significantly impact intestinal microbiota following bariatric surgery

Bariatric surgery is the most effective treatment for weight loss. Vertical sleeve gastrectomy (VSG) involves the resection of ~ 80% of the stomach and was conceived to purely restrict oral intake. However, evidence suggests more complex mechanisms, particularly postoperative changes in gut microbiota, in facilitating weight loss and resolving associated comorbidities. VSG in humans is a complex procedure and includes peri-operative antibiotics and caloric restriction in addition to the altered anatomy. The impact of each of these factors on the intestinal microbiota have not been evaluated. The aim of this study was to determine the relative contributions of each of these factors on intestinal microbiota composition following VSG prior to substantial weight loss. Thirty-two obese patients underwent one of three treatments: (1) VSG plus routine intravenous peri-operative antibiotics (n = 12), (2) VSG with intravenous vancomycin chosen for its low intestinal penetrance (n = 12), and (3) caloric restriction (n = 8). Fecal samples were evaluated for bacterial composition prior to and 7 days following each intervention. Only patients undergoing VSG with routine peri-operative antibiotics showed a significant shift in community composition. Our data support the single dose of routine peri-operative antibiotics as the most influential factor of intestinal microbial composition acutely following VSG.

Gut microbiota modulate dendritic cell antigen presentation and radiotherapy-induced antitumor immune response

Alterations in gut microbiota impact the pathophysiology of several diseases, including cancer. Radiotherapy (RT), an established curative and palliative cancer treatment, exerts potent immune modulatory effects, inducing tumor-associated antigen (TAA) cross-priming with antitumor CD8+ T cell elicitation and abscopal effects. We tested whether the gut microbiota modulates antitumor immune response following RT distal to the gut. Vancomycin, an antibiotic that acts mainly on gram-positive bacteria and is restricted to the gut, potentiated the RT-induced antitumor immune response and tumor growth inhibition. This synergy was dependent on TAA cross presentation to cytolytic CD8+ T cells and on IFN-γ. Notably, butyrate, a metabolite produced by the vancomycin-depleted gut bacteria, abrogated the vancomycin effect. In conclusion, depletion of vancomycin-sensitive bacteria enhances the antitumor activity of RT, which has important clinical ramifications.

Impact of antimicrobial therapy on the gut microbiome

The gut microbiome is now considered an organ unto itself and plays an important role in health maintenance and recovery from critical illness. The commensal organisms responsible for the framework of the gut microbiome are valuable in protection against disease and various physiological tasks. Critical illness and the associated interventions have a detrimental impact on the microbiome. While antimicrobials are one of the fundamental and often life-saving modalities in septic patients, they can also pave the way for subsequent harm because of the resulting damage to the gut microbiome. Contributing to many of the non-specific signs and symptoms of sepsis, the balance between the overuse of antimicrobials and the clinical need in these situations is often difficult to delineate. Given the potency of antimicrobials utilized to treat septic patients, the effects on the gut microbiome are often rapid and long-lasting, in which case full recovery may never be observed. The overgrowth of opportunistic pathogens is of significant concern as they can lead to infections that become increasingly difficult to treat. Continued research to understand the disturbances within the gut microbiome of critically ill patients and their outcomes is essential to help develop future therapies to circumvent damage to, or restore, the microbiome. In this review, we discuss the impact of the antimicrobials often used for the treatment of sepsis on the gut microbiota.

Butyrate Ameliorates Antibiotic-Driven Type 1 Diabetes in the Female Offspring of Nonobese Diabetic Mice

Maternal gut dysbiosis affects the development of the offspring immune system. Our previous study has indicated that microbial metabolite butyrate directly shapes pancreatic immune tolerance and dampens type 1 diabetes (T1D) progression. Therefore, maternal butyrate intervention may protect their offspring from maternal gut dysbiosis-accelerated T1D. To test this, pregnant nonobese diabetic (NOD) mice were treated with vancomycin in drinking water with or without a butyrate-supplemented diet during gestation and nursing (oral vancomycin is used to induce maternal gut dysbiosis). Three weeks after delivery, T1D-associated innate and adaptive immune cells were detected to investigate the effects of butyrate on the vancomycin-exacerbated pancreatic immune disorder in dams and pups. The results showed that butyrate inhibited maternal vancomycin-exacerbated secretion of proinflammation cytokines (interferon γ and interleukin-1β) and maternal vancomycin-exacerbated recruitment of interferon γ⁺ T cells (cytotoxic T lymphocytes 1 cells and T helper type 1 cells) in the pancreas of the female offspring, thus dampening T1D development. The protection may be due to butyrate inhibiting the activation of pancreatic dendritic cells (DCs). Our data thus demonstrate that maternal gut dysbiosis can exacerbate pancreatic-directed autoimmunity in the female offspring through T cell- and DC-associated mechanisms that are inhibited by butyrate.

Gastrointestinal Tract Dysbiosis Enhances Distal Tumor Progression through Suppression of Leukocyte Trafficking

The overall use of antibiotics has increased significantly in recent years. Besides fighting infections, antibiotics also alter the gut microbiota. Commensal bacteria in the gastrointestinal tract are crucial to maintain immune homeostasis, and microbial imbalance or dysbiosis affects disease susceptibility and progression. We hypothesized that antibiotic-induced dysbiosis of the gut microbiota would suppress cytokine profiles in the host, thereby leading to changes in the tumor microenvironment. The induced dysbiosis was characterized by alterations in bacterial abundance, composition, and diversity in our animal models. On the host side, antibiotic-induced dysbiosis caused elongated small intestines and ceca, and B16-F10 melanoma and Lewis lung carcinoma progressed more quickly than in control mice. Mechanistic studies revealed that this progression was mediated by suppressed TNFα levels, both locally and systemically, resulting in reduced expression of tumor endothelial adhesion molecules, particularly intercellular adhesion molecule-1 (ICAM-1) and a subsequent decrease in the number of activated and effector CD8⁺ T cells in the tumor. However, suppression of ICAM-1 or its binding site, the alpha subunit of lymphocyte function-associated antigen-1, was not seen in the spleen or thymus during dysbiosis. TNFα supplementation in dysbiotic mice was able to increase ICAM-1 expression and leukocyte trafficking into the tumor. Overall, these results demonstrate the importance of commensal bacteria in supporting anticancer immune surveillance, define an important role of tumor endothelial cells within this process, and suggest adverse consequences of antibiotics on cancer control. SIGNIFICANCE: Antibiotic-induced dysbiosis enhances distal tumor progression by altering host cytokine levels, resulting in suppression of tumor endothelial adhesion molecules and activated and effector CD8⁺ T cells in the tumor.

Clinical Pharmacology of Antibiotics

Antimicrobial pharmacology and its effect on prescribing is quite complex. Selecting an antibiotic that will optimally treat an infection while minimizing adverse effects and the development of resistance is only the first step, as one must also consider the patient's individual pharmacokinetic alterations and the pharmacodynamic properties of the drug when prescribing it as well. Patients with CKD may have alterations in their protein binding, volumes of distribution, kidney clearance, and nonrenal clearance that necessitates antibiotic dose adjustments to prevent the development of toxicity. Knowledge of a drug's pharmacodynamics, defined as the relationship between drug exposure and antibacterial efficacy, provides some guidance regarding the optimal way to make dose adjustments. Different pharmacodynamic goals, such as maximizing the time that free (unbound) drug concentrations spend above the minimum inhibitory concentration (MIC) for time dependent drugs (e.g., β-lactams) or maximizing the free peak-to-MIC ratio for concentration-dependent antibiotics (e.g., aminoglycosides), require different adjustment strategies; for instance, decreasing the dose while maintaining normal dosing frequency or giving normal (or even larger) doses less frequently, respectively. Patients receiving hemodialysis have other important prescribing considerations as well. The nephrologist or patient may prefer to receive antibiotics that can be administered intravenously toward the end of a dialysis session. Additionally, newer dialysis technologies and filters can increase drug removal more than originally reported. This review will discuss the place in therapy, mechanism of action, pharmacokinetic, pharmacodynamic, and other pharmacologic considerations encountered when prescribing commonly used antibiotics in patients with chronic kidney disease or ESKD.

An Unusual Case of Ototoxicity with Use of Oral Vancomycin

Introduction

Systemic absorption of oral vancomycin is poor due to the size of the molecule and its pharmacokinetics. It has an elimination half life of 5-11 hours in patients with normal renal function. We present a rare case of ototoxicity after oral vancomycin administration and detectable serum vancomycin levels 24 hours after cessation of vancomycin.

Case Presentation

A 42-year-old woman with a history of hypertension, diabetes mellitus, and previously treated Clostridium difficile colitis presented with abdominal pain and diarrhea for two weeks. Clostridium difficile infection was confirmed by PCR, and at the time of diagnosis and initiation of therapy, the patient had normal renal function. Vancomycin was initiated at a dose of 125 mg po q6h. After the third dose of oral vancomycin, the patient reported new symptoms of lightheadedness, sensations of "buzzing" and whistling of bilateral ears, and decreased perception of hearing described as "clogged ears." The patient reported to the emergency department the next day due to worsening of these symptoms, and vancomycin dosing was reduced to every 8 hours; however, the patient reported the auditory symptoms persisted. On day three, vancomycin was discontinued with gradual resolution of symptoms over the next 12 hours. On day four, a serum random vancomycin level obtained 24 hours after the last dose was detectable at 2 mcg/dl. Temporal association of the patient's symptoms and improvement with cessation of therapy along with a detectable vancomycin level indicates systemic absorption of oral vancomycin with subsequent ototoxicity.

Discussion

The potential for absorption of oral vancomycin is not well described and is attributed to compromised intestinal epithelium allowing for increased drug absorption. Few studies suggested that oral vancomycin may result in therapeutic or even potentially toxic levels of serum vancomycin in patients with impaired renal function. Ototoxicity may be a transient or permanent side effect of vancomycin therapy and is related to high serum levels. Symptoms usually resolve after decreasing the dose or cessation of vancomycin. No detectable serum vancomycin levels were found in 98% of the patients treated with oral vancomycin in a prospective study. The described case is unusual because despite normal renal function, the patient still developed ototoxicity, and systemic absorption of the drug was confirmed with a measurable vancomycin level approximately 24 hours after the drug was stopped. Additionally, the only other medication prescribed to the patient at the time of vancomycin administration was metformin at a dose of 500 mg po bid which has no known idiosyncratic interactions potentiating adverse side effects to vancomycin. This case reflects that some patients may be more susceptible to increased systemic absorption via the oral route, and the possibility for ototoxicity should be considered and discussed with patients while prescribing oral vancomycin.

Vancomycin-resistant enterococci in acute myeloid leukemia and myelodysplastic syndrome patients undergoing induction chemotherapy with idarubicin and cytarabine

We conducted a retrospective study to determine the risk factors associated with vancomycin-resistant enterococci (VRE) acquisition/infection in newly diagnosed acute myeloid leukemia and myelodysplastic syndrome patients undergoing chemotherapy with the 7 + 3 regimen of cytarabine and idarubicin. Although only 2.5% (6/235) patients were colonized with VRE on admission, 59% (134/229) of patients acquired VRE during their hospitalization. Multivariable analysis identified the use of intravenous vancomycin (p = .024; HR: 1.548) and cephalosporin (p = .009; HR: 1.596) as the risk factors for VRE acquisition. VRE infection developed in 14% (33/229) of patients, with bloodstream infections accounting for 82% (27/33) of cases. VRE infection occurred in 25/126 (20%) of the VRE-colonized patients, but only 8/103 (8%) of those who were not (p = .01). Our study provides the evidence for the role of intravenous cephalosporin and vancomycin in VRE acquisition and highlights the clinical significance of VRE colonization in these patients.

Microbiome mediation of infections in the cancer setting

Infections encountered in the cancer setting may arise from intensive cancer treatments or may result from the cancer itself, leading to risk of infections through immune compromise, disruption of anatomic barriers, and exposure to nosocomial (hospital-acquired) pathogens. Consequently, cancer-related infections are unique and epidemiologically distinct from those in other patient populations and may be particularly challenging for clinicians to treat. There is increasing evidence that the microbiome is a crucial factor in the cancer patient's risk for infectious complications. Frequently encountered pathogens with observed ties to the microbiome include vancomycin-resistant Enterococcus, Enterobacteriaceae, and Clostridium difficile; these organisms can exist in the human body without disease under normal circumstances, but all can arise as infections when the microbiome is disrupted. In the cancer patient, such disruptions may result from interventions such as chemotherapy, broad-spectrum antibiotics, or anatomic alteration through surgery. In this review, we discuss evidence of the significant role of the microbiome in cancer-related infections; how a better understanding of the role of the microbiome can facilitate our understanding of these complications; and how this knowledge might be exploited to improve outcomes in cancer patients and reduce risk of infection.

SaMpling Antibiotics in Renal Replacement Therapy (SMARRT): an observational pharmacokinetic study in critically ill patients

Background

Optimal antibiotic dosing is key to maximising patient survival, and minimising the emergence of bacterial resistance. Evidence-based antibiotic dosing guidelines for critically ill patients receiving RRT are currently not available, as RRT techniques and settings vary greatly between ICUs and even individual patients. We aim to develop a robust, evidence-based antibiotic dosing guideline for critically ill patients receiving various forms of RRT. We further aim to observe whether therapeutic antibiotic concentrations are associated with reduced 28-day mortality.

Methods/Design

We designed a multi-national, observational pharmacokinetic study in critically ill patients requiring RRT. The study antibiotics will be vancomycin, linezolid, piperacillin/tazobactam and meropenem. Pharmacokinetic sampling of each patient’s blood, RRT effluent and urine will take place during two separate dosing intervals. In addition, a comprehensive data set, which includes the patients’ demographic and clinical parameters, as well as modality, technique and settings of RRT, will be collected. Pharmacokinetic data will be analysed using a population pharmacokinetic approach to identify covariates associated with changes in pharmacokinetic parameters in critically ill patients with AKI who are undergoing RRT for the five commonly prescribed antibiotics.

Discussion

Using the comprehensive data set collected, the pharmacokinetic profile of the five antibiotics will be constructed, including identification of RRT and other factors indicative of the need for altered antibiotic dosing requirements. This will enable us to develop a dosing guideline for each individual antibiotic that is likely to be relevant to any critically ill patient with acute kidney injury receiving any of the included forms of RRT.

Trial registration

Australian New Zealand Clinical Trial Registry (ACTRN12613000241730) registered 28 February 2013

Continuous versus intermittent infusion of vancomycin in adult patients: A systematic review and meta-analysis

Continuous infusion of vancomycin (CIV) and intermittent infusion of vancomycin (IIV) are two major administration strategies in clinical settings. However, previous articles comparing the efficacy and safety of CIV versus IIV showed inconsistent results. Therefore, a meta-analysis was conducted to compare the efficacy and safety of CIV and IIV. PubMed, the Cochrane Library and Web of Science up to June 2015 were searched using the keywords 'vancomycin', 'intravenous', 'parenteral', 'continuous', 'intermittent', 'discontinuous', 'infusion', 'administration' and 'dosing'. Eleven studies were included in the meta-analysis. Neither heterogeneity nor publication bias were observed. Patients treated with CIV had a significantly lower incidence of nephrotoxicity compared with patients receiving IIV [risk ratio (RR)=0.61, 95% confidence interval (CI) 0.47-0.80; P<0.001]. No significant difference in treatment failure between the two groups was detected. Mortality between patients receiving CIV and patients receiving IIV was similar (RR=1.15, 95% CI 0.85-1.54; P=0.365). This meta-analysis showed that CIV had superior safety compared with IIV, whilst the clinical efficacy was not significantly different. A further multicentre, randomised controlled trial is required to confirm these results.

Intestinal Blautia Is Associated with Reduced Death from Graft-versus-Host Disease

The relationship between intestinal microbiota composition and acute graft-versus-host disease (GVHD) after allogeneic blood/marrow transplantation (allo-BMT) is not well understood. Intestinal bacteria have long been thought to contribute to GVHD pathophysiology, but recent animal studies in nontransplant settings have found that anti-inflammatory effects are mediated by certain subpopulations of intestinal commensals. Hypothesizing that a more nuanced relationship may exist between the intestinal bacteria and GVHD, we evaluated the fecal bacterial composition of 64 patients 12 days after BMT. We found that increased bacterial diversity was associated with reduced GVHD-related mortality. Furthermore, harboring increased amounts of bacteria belonging to the genus Blautia was associated with reduced GVHD lethality in this cohort and was confirmed in another independent cohort of 51 patients from the same institution. Blautia abundance was also associated with improved overall survival. We evaluated the abundance of Blautia with respect to clinical factors and found that loss of Blautia was associated with treatment with antibiotics that inhibit anaerobic bacteria and receiving total parenteral nutrition for longer durations. We conclude that increased abundance of commensal bacteria belonging to the Blautia genus is associated with reduced lethal GVHD and improved overall survival.

Estimation of glomerular filtration rate to adjust vancomycin dosage in critically ill patients: superiority of the Chronic Kidney Disease Epidemiology Collaboration equation?

The purpose of this study was to determine the best estimate of glomerular filtration rate (GFR) to adjust vancomycin (VAN) dosage in critically ill patients. Seventy-eight adult intensive care unit patients received a 15 mg/kg loading dose of VAN plus a 30 mg/kg/day continuous infusion. Steady-state concentration was measured 48 hours later and the dose was adjusted to obtain a target concentration ranging from 20 to 25 mg/l. GFR was estimated by measured creatinine clearance (CLCR), Cockcroft, Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. The required dose providing the target concentration was 36±17 mg/kg/day. The first dosage had to be increased in 51% of all patients and in 84% of trauma patients (highest GFR), but had to be decreased in 17% of patients. The closest relationship between clearances of vancomycin was observed with CKD-EPI to GFR. The correlation between clearances of vancomycin and measured CLCR was significant but was rather poor with Cockcroft and Modification of Diet in Renal Disease equation. On the Bland and Altman plots, measured CLCR provided a lower bias but a larger confidence interval and a weaker precision than CKD-EPI. For VAN dose adjustments in intensive care unit patients, Cockcroft formula and Modification of Diet in Renal Disease should be used with caution. In clinical practice, the physician does not have at their disposal the patient's measured CLCR when prescribing. The CKD-EPI appears to be the best predictor of clearances of vancomycin for calculation of a therapeutic VAN regimen.

Therapeutic drug monitoring of antimicrobials

Optimizing the prescription of antimicrobials is required to improve clinical outcome from infections and to reduce the development of antimicrobial resistance. One such method to improve antimicrobial dosing in individual patients is through application of therapeutic drug monitoring (TDM). The aim of this manuscript is to review the place of TDM in the dosing of antimicrobial agents, specifically the importance of pharmacokinetics (PK) and pharmacodynamics (PD) to define the antimicrobial exposures necessary for maximizing killing or inhibition of bacterial growth. In this context, there are robust data for some antimicrobials, including the ratio of a PK parameter (e.g. peak concentration) to the minimal inhibitory concentration of the bacteria associated with maximal antimicrobial effect. Blood sampling of an individual patient can then further define the relevant PK parameter value in that patient and, if necessary, antimicrobial dosing can be adjusted to enable achievement of the target PK/PD ratio. To date, the clinical outcome benefits of a systematic TDM programme for antimicrobials have only been demonstrated for aminoglycosides, although the decreasing susceptibility of bacteria to available antimicrobials and the increasing costs of pharmaceuticals, as well as emerging data on pharmacokinetic variability, suggest that benefits are likely.

A case of spontaneous methicillin-resistant Staphylococcus aureus meningitis in a health care worker

Meningitis caused by Staphylococcus aureus is an unusual illness that is often associated with bacteremia, contiguous infection and/or a post-neurosurgical state. Until recently, most cases were caused by methicillin-susceptible strains, but there are a few reports of methicillinresistant S aureus strains causing meningitis. A new case of meningitis caused by methicillin-resistant S aureus in a neonatal intensive care nurse who did not have bacteremia or neurosurgery is reported. The patient made a full recovery after treatment with vancomycin and rifampin.

Clearance of vancomycin during continuous infusion in Intensive Care Unit patients: correlation with measured and estimated creatinine clearance and serum cystatin C

Vancomycin (VAN) dosing requires adjustment to renal function, which is often estimated using the Cockcroft-Gault formula; however, its precision is poor in Intensive Care Unit (ICU) patients. VAN clearance (CL(Van)) during continuous infusion was prospectively determined in 25 ICU patients [14 male, 11 female; age range 31-82 years; body mass index (BMI) 16.5-41.5 kg/m²; Acute Physiology and Chronic Health Evaluation (APACHE) II score at admission 8-36; creatinine clearance 25-195 mL/min] and its correlation with measured creatinine clearance (CL(Crea)), estimated creatinine clearance using the Cockcroft-Gault formula (CL(CG)) and estimated glomerular filtration rate according to Hoek's formula based on serum cystatin C (GFR(Hoek)) was investigated. The correlation between CL(Van) and CL(Crea) was very good (r²=0.88), but it was rather poor with CL(CG) (r² = 0.37) and was acceptable with GFR(Hoek) (r² = 0.70). For VAN dose adjustments in ICU patients, determination of cystatin C may be an interesting and practical alternative to measured CL(Crea), whereas the Cockcroft-Gault formula should be used with caution.

Vancomycin revisited: a reappraisal of clinical use

Vancomycin has been used for decades to treat serious systemic gram positive infections. Extensive use over time has demonstrated vancomycin is not nephrotoxic even when used in high dosage, i.e., twice the usual dose. Since vancomycin is not nephrotoxic, there is no rationale for dosing vancomycin based on serum vancomycin levels. Since vancomycin is eliminated by GFR, vancomycin dosing should be based on creatinine clearance. Vancomycin obeys "concentration dependent" kinetics and higher than usual doses may be useful in some infections (eg, osteomyelitis). Widespread vancomycin use has resulted in increased VRE prevalence worldwide. Among staphylococci, vancomycin induced cell wall thickening results in "permeability mediated" resistance to vancomycin, as well as other anti-staphylococcal antibiotics. "Permeability mediated" resistance accounts for the common clinical observation that MRSA infections treated with vancomycin often resolve slowly or not at all. Other effective MRSA antibiotics are available (eg, linezolid, daptomycin, minocycline, or tigecycline) and are more reliably effective, do not increase staphylococcal resistance or increase VRE prevalence.

Pharmacodynamics of antibiotics to treat multidrug-resistant Gram-positive hospital infections

Hospital infection due to multidrug-resistant Gram-positive bacteria may often represent a life-threatening challenge; thus, to appropriately combat them, clinicians should be confident and systematically apply several important pharmacodynamic concepts. The concept of 'correct antibiotic treatment' should include, in addition to an appropriate choice in terms of antimicrobial susceptibility, an appropriate dosage and administration schedule consistent with the pharmacodynamic principles. In the next few years, it is expected that some of the anti-Gram-positive antimicrobial agents that are currently under investigation will be added to the therapeutic armamentarium. However, optimization of the usage of old drugs still remains a clinical priority and a scientific challenge, whose dignity may be considered of similar importance to that of the assessment of the possible therapeutic role of the new compounds.

Evaluation of Bayesian predictability of vancomycin concentration using population pharmacokinetic parameters in pediatric patients

The objective of this study was to evaluate the Bayesian predictability of vancomycin (VCM) pharmacokinetics in Japanese pediatric patients using one-compartment population pharmacokinetic (PPK) parameters, which we reported previously. The validity of the PPK model was evaluated by bootstrap method and cross validation method, and the Bayesian predictive performance was examined. The predictive performance of the PPK model for premature patients was also examined. The cross validation method showed the predictability to be acceptable for practical use, especially for predicting trough concentration using other trough data. However, for the external premature patient data, this PPK model did not seem to be adequate. A theoretical approach using a simulation technique was also examined to evaluate the predictive performance. The results suggested that the predictability at the peak was not necessarily good at all sampling times and the predictability at the trough was better when a later time point was used. The optimal sampling time for prediction of VCM concentration in pediatric patients is discussed.

Epileptogenic Activity of Methicillin-Resistant Staphylococcus aureus (MRSA) Antibiotics in Rats

The present study was undertaken to clarify the epileptogenic activity induced by intracerebroventricular injection (i.c.v.) of antibiotics effective in methicillin-resistant Staphylococcus aureus (MRSA) in chronically electrode implanted rats. Teicoplanin (10-100 microg, i.c.v.) caused dose-related electroencephalographic (EEG) seizure characterized by an uninterrupted high voltage and wave complex. At the same time, the rats showed forelimb clonus, head nodding, jumping and severe convulsion. At a high dose (100 microg, i.c.v.), the drug caused a severe twisting immediately after the intracerebroventricular injection (i.c.v.) followed by jumping and violent convulsion with a continuous rhythmic spike and wave complex in EEG. On the other hand, vancomycin (30-1000 microg, i.c.v.) caused no or almost no epileptogenic activity in terms of behavior and in EEG. However, at a high dose (1000 microg, i.c.v.), the drug caused an occasional spike from the hippocampus without showing any behavioral changes in the rats. Fosfomycin (30-1000 microg, i.c.v.), cefazolin (10-100 microg, i.c.v.) and penicillin G (30-300 microg, i.c.v.), used as reference drugs, caused dose-dependent epileptogenic activity in both EEG. From these findings, it was found that teicoplanin caused a potent epileptogenic activity, different to vancomycin. Therefore, it can be concluded that vancomycin may be safety on epileptogenic activity used for the clinical purpose of infections caused by MRSA.

Vancomycin versus teicoplanin in the therapy of experimental methicillin-resistant Staphylococcus aureus (MRSA) meningitis

The aim of this study was to compare the antibacterial activity of teicoplanin and vancomycin in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) meningitis using a rabbit meningitis model. The MRSA strain ATCC 43300 was used to infect the rabbits. The vancomycin group received 20 mg/kg vancomycin every 12h (q12h), the teicoplanin group received 6 mg/kg teicoplanin q12h and the control group did not receive any treatment. Drug levels were measured using a bioassay technique. Bacterial counts in the treatment groups were significantly lower (P<0.05) than those of the control group at 12 h and 24 h after treatment. When the treatment groups were compared, the bacterial counts after 12 h or 24 h of treatment were similar (P>0.05). These data suggest that the antibacterial activity of vancomycin and teicoplanin are similar in experimental MRSA meningitis of rabbits.

Post-neurosurgical nosocomial bacterial meningitis in adults: microbiology, clinical features, and outcomes

The clinical data of 62 adult patients who suffered post-neurosurgical nosocomial bacterial meningitis, retrospectively collected over a 16-year period, were studied. Cases were divided into two groups based on the date of presentation, the first period being 1986-1993 and the second 1994-2001. Fever and progressive consciousness disturbance were the most consistent clinical features - signs that may also be attributed to other postoperative neurosurgical problems. The common pathogens included Staphylococcus aureus, coagulase negative Staphylococcus, Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter baumannii. An increase in polymicrobial infections and multi-antibiotic resistance during the second period was identified. In the first half of the study, mortality was 22%, and in the second half 36%. Adult post-neurosurgical nosocomial bacterial meningitis has become an important clinical problem. The choice of appropriate empirical antibiotics is challenging and must be guided by an awareness of the relative frequency of various pathogens and the increasing incidence of resistant strains. Although high mortality rates may, in part, be related to the primary brain pathology, early diagnosis and the timely use of antibiotics based on antimicrobial susceptibility testing are essential for survival.

Meningitis due to methicillin-resistant Staphylococcus aureus (MRSA): Review of 10 cases

We evaluated retrospectively, 10 MRSA meningitis cases in our hospital that occurred between January 1999 and June 2004. All were post-neurosurgical and were considered to have hospital-acquired meningitis. Fever, leukocytosis, variable conscious levels were the most common findings. Six patients were treated with regimens including teicoplanin, and four with vancomycin. Mean duration of treatment was 23.5+/-18.8 days (range, 3-60 days). One patient died. In cases of MRSA meningitis, intravenous vancomycin is the mainstay of therapy. However, six of these 10 patients were successfully treated with regimens including teicoplanin, suggesting that this agent may be an alternative to vancomycin in the therapy of these cases.

Evidence for biliary excretion of vancomycin into stool during intravenous therapy: potential implications for rectal colonization with vancomycin-resistant enterococci

Sixty-three stool samples and five bile samples were prospectively collected from 33 patients receiving intravenous vancomycin therapy and were quantitatively analyzed for vancomycin by a competitive immunoassay. Vancomycin was excreted via bile into the stools of almost all patients at concentrations of 3.3 to 94.8 microg/ml after >/=5 days of a therapy of 1 g every 12 h.

[An example of simulation for a better understanding of PK/PD relationship of antibiotics]

The interpretation of PK/PD indices is specific to each class of antibiotics. In order to illustrate this, we developed a multidisciplinary tutorial program based on simulation of clinical cases. Three drugs were included in this software: tobramycin, vancomycin and azithromycin. From the dosage regimen proposed by the user, the model simulates a plotting of antibiotic plasma concentrations vs. time (tobramycin, vancomycin and azithromycin) and tissue concentrations (azithromycin). Peak and trough concentrations are calculated at steady-state. A commentary is provided to evaluate the efficacy of treatment and to assist the user in improving his prescription of tobramycin or vancomycin. T(> MIC) (time the concentration remains above the MIC) and AUC(24) (area under the concentration-time curve) are calculated in plasma and tissues for azithromycin. In order to create a link between theoretical pharmacokinetics and clinical practice, we propose this model as a simulation of antibiotic monitoring. We put the emphasis on interactivity and simulation, leading to applied reasoning and decision making. It illustrates (i) the influence of pharmacokinetic parameters, location of infection and bactericidal kinetics on the use of three different classes of antibiotics, (ii) the role of route of administration, dosing and intervals between administrations on therapeutic response and (iii) the influence of erratic administrations on clinical efficacy.

Effects of linezolid on staphylococcal adherence versus time of treatment

Staphylococcus epidermidis has emerged as a major nosocomial pathogen that is often associated with infections of indwelling medical devices. Microbial adhesion to implanted foreign materials is a prerequisite for establishing infection. We studied the time-dependent anti-adhesion effects of linezolid and vancomycin on three S. epidermidis clinical isolates. Minimum inhibitory concentration (MIC) values were identical for both agents for all three isolates (2 mg/l). Bacterial suspensions were added to polystyrene wells and treated with 0.5-4 times the MIC of linezolid or vancomycin at 0, 2, 4 or 6 h post-inoculation. Supra-inhibitory (2 and 4 x MIC) and inhibitory (MIC) concentrations of linezolid demonstrated potent anti-adhesion activity following 2 and 4 h deferred treatments. Even at sub-inhibitory concentrations (0.5 x MIC), suppression of staphylococcal adherence to polystyrene was still evident in most cultures. Linezolid at two and four times the MIC also exerted significant inhibitory effects in cultures that had been treated with a 6-h delay. Supra-inhibitory and inhibitory concentrations of vancomycin administered 2 h post-infection appeared equally effective as linezolid. However, sub-inhibitory concentrations of vancomycin showed minimal or no activity against bacterial adhesion. When vancomycin treatments were delayed by 4 h, only concentrations above the MIC prevented adherence. Linezolid has promising in vitro anti-adhesion activity that merits further studies to determine its role in the management of foreign-body infections.

Treatment of staphylococcal ventriculitis associated with external cerebrospinal fluid drains: a prospective randomized trial of intravenous compared with intraventricular vancomycin therapy

OBJECT

Staphylococcal ventriculitis may be a complication in temporary external ventricular drains (EVDs). The limited penetration of vancomycin into the cerebrospinal fluid (CSF) is well known; the pharmacodynamics and efficacy of systemically compared with intraventricularly administered vancomycin is examined in this prospective study.

METHODS

Ten patients in whom EVDs were implanted to treat intracranial hemorrhage and who were suffering from drain-associated ventriculitis were randomized into two treatment groups. Five of these patients (median age 47 years) were treated with 2 g/day vancomycin administered intravenously (four infusions/day, Group 1), and the other five(median age 49 years) received 10 mg vancomycin intraventricularly once daily (Group 2). Vancomycin levels were measured in serum and CSF six times a day. The maximum vancomycin level in CSF was 1.73 +/- 0.4 micro/ml in Group 1 and 565.58 +/- 168.71 microg/ml 1 hour after vancomycin application in Group 2 (mean +/- standard deviation). Vancomycin levels above the recommended trough level of 5 microg/ml in CSF were never reached in Group 1, whereas in Group 2 they below the trough level (3.74 +/- 0.66 microg/ml) only at 21 hours after intraventricular vancomycin application. The vancomycin level in the serum was constant within therapeutic levels in Group 1, whereas in Group 2 in most instances vancomycin was almost below a measurable concentration. In both groups bacteriologically and laboratory-confirmed CSF clearance could be obtained.

CONCLUSIONS

Intraventricular vancomycin application is a safe and efficacious treatment modality in drain-associated ventriculitis, with much higher vancomycin levels being achieved in the ventricular CSF than by intravenous administration.

Evaluation of estimated and measured creatinine clearances for predicting the pharmacokinetics of vancomycin in adult liver transplant recipients

This study examined the pharmacokinetics and dosing requirements of vancomycin in adult liver transplant recipients and also evaluated the predictability of determining vancomycin-dosing requirements utilizing an estimated creatinine clearance (CrCl) approach. Twenty adult liver transplant recipients were included in this analysis. Vancomycin pharmacokinetic parameters and dosing requirements calculated from estimated CrCl and population-based pharmacokinetic equations were compared with values calculated using serum concentrations and assuming a one-compartment model. Compared with the values obtained using equations to estimate the CrCl and vancomycin pharmacokinetics (t, Cl, and Vd), the actual values were statistically different for half-life and clearance (11.0 vs. 16.4 hours and 52 vs. 36 mL/min, respectively; P < 0.01). Additionally, CrCl that were estimated using population-based formulas significantly overestimated actual CrCl calculated using 24-hour urine collections (65-78 vs. 43 mL/min; P < 0.05). The results from this study indicate that serum creatinine concentrations do not adequately predict glomerular filtration rates (GFR) or vancomycin clearance in adult liver transplant recipients. Based on these results, the use of 24-hour urine CrCl to predict GFR and serum concentrations to properly dose vancomycin is advocated.