Treatment of Serratia marcescens meningitis with prolonged infusion of meropenem

Neonatal Brain Abscess with Serratia marcescens after Intrauterine Infection: A Case Report

Brain abscesses are a possible complication of bacterial sepsis or central nervous system infection but are uncommon in the neonatal period. Gram-negative organisms often cause them, but Serratia marcescens is an unusual cause of sepsis and meningitis in this age group. This pathogen is opportunistic and frequently responsible for nosocomial infections. Despite the existing antibiotics and modern radiological tools, mortality and morbidity remain significant in this group of patients. We report an unusual unilocular brain abscess in a preterm neonate caused by Serratia marcescens. The infection had an intrauterine onset. The pregnancy was achieved through assisted human reproduction techniques. It was a high-risk pregnancy, with pregnancy-induced hypertension, imminent abortion, and required prolonged hospitalization of the pregnant woman with multiple vaginal examinations. The infant was treated with multiple antibiotic cures and percutaneous drainage of the brain abscess associated with local antibiotic treatment. Despite treatment, evolution was unfavorable, complicated by fungal sepsis (Candida parapsilosis) and multiple organ dysfunction syndrome.

A guide to therapeutic drug monitoring of β-lactam antibiotics

Therapeutic drug monitoring (TDM) opens the door to personalized medicine, yet it is infrequently applied to β-lactam antibiotics, one of the most commonly prescribed drug classes in the hospital setting. As we continue to understand more about β-lactam pharmacodynamics (PD) and wide inter- and intra-patient variability in pharmacokinetics (PK), the utility of TDM has become increasingly apparent. For β-lactams, the time that free concentrations remain above the minimum inhibitory concentration (MIC) as a function of the dosing interval (%fT>MIC) has been shown to best predict antibacterial effect. Many studies have shown that β-lactam %fT>MIC exposures are often suboptimal across a wide variety of disease states and clinical settings. A limitation to implementing this practice is the general lack of understanding on how to best operationalize this intervention and interpret the results. The instrumentation and expertise needed to quantify β-lactams for TDM is rarely available locally, but certain laboratories advertise these services and perform them regularly. Familiarity with the modalities and nuances of antimicrobial susceptibility testing is crucial to establishing β-lactam concentration targets that meet the relevant exposure thresholds. Evaluation of these concentrations is best accomplished using population PK software and Bayesian modeling, for which a multitude of programs are available. While TDM of β-lactams has shown an ability to increase the rate of target attainment, there is currently limited evidence to suggest that it leads to improved clinical outcomes. Although consensus guidelines for β-lactam TDM do not exist in the United States, guidance would help to promote this important practice and better standardize the approach across institutions. Herein, we discuss the basis for β-lactam TDM, review supporting evidence, and provide guidance for implementation in specific patient populations.

Is Meropenem as a Monotherapy Truly Incompetent for Meropenem-Nonsusceptible Bacterial Strains? A Pharmacokinetic/Pharmacodynamic Modeling With Monte Carlo Simulation

Infections due to meropenem-nonsusceptible bacterial strains (MNBSs) with meropenem minimum inhibitory concentrations (MICs) ≥ 16 mg/L have become an urgent problem. Currently, the optimal treatment strategy for these cases remains uncertain due to some limitations of currently available mono- and combination therapy regimens. Meropenem monotherapy using a high dose of 2 g every 8 h (q 8 h) and a 3-h traditional simple prolonged-infusion (TSPI) has proven to be helpful for the treatment of infections due to MNBSs with MICs of 4–8 mg/L but is limited for cases with higher MICs of ≥16 mg/L. This study demonstrated that optimized two-step-administration therapy (OTAT, i.e., a new administration model of i.v. bolus plus prolonged infusion) for meropenem, even in monotherapy, can resolve this problem and was thus an important approach of suppressing such highly resistant bacterial isolates. Herein, a pharmacokinetic (PK)/pharmacodynamic (PD) modeling with Monte Carlo simulation was performed to calculate the probabilities of target attainment (PTAs) and the cumulative fractions of response (CFRs) provided by dosage regimens and 39 OTAT regimens in five dosing models targeting eight highly resistant bacterial species with meropenem MICs ≥ 16 mg/L, including Acinetobacter baumannii, Acinetobacter spp., Enterococcus faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Stenotrophomonas maltophilia, were designed and evaluated. The data indicated that meropenem monotherapy administered at a high dose of 2 g q 8 h and as an OTAT achieved a PTA of ≥90% for isolates with an MIC of up to 128 mg/L and a CFR of ≥90% for all of the targeted pathogen populations when 50% f T > MIC (50% of the dosing interval during which free drug concentrations remain above the MIC) is chosen as the PD target, with Enterococcus faecalis being the sole exception. Even though 50% f T > 5 × MIC is chosen as the PD target, the aforementioned dosage regimen still reached a PTA of ≥90% for isolates with an MIC of up to 32 mg/L and a CFR of ≥90% for Acinetobacter spp., Pseudomonas aeruginosa, and Klebsiella pneumoniae populations. In conclusion, meropenem monotherapy displays potential competency for infections due to such highly resistant bacterial isolates provided that it is administered as a reasonable OTAT but not as the currently widely recommended TSPI.

Pharmacokinetics-pharmacodynamics issues relevant for the clinical use of beta-lactam antibiotics in critically ill patients

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients and beta-lactams are the most common antibiotic class used. Critically ill patient's pathophysiological factors lead to altered pharmacokinetics and pharmacodynamics of beta-lactams.A comprehensive bibliographic search in PubMed database of all English language articles published from January 2000 to December 2017 was performed, allowing the selection of articles addressing the pharmacokinetics or pharmacodynamics of beta-lactam antibiotics in critically ill patients.In critically ill patients, several factors may increase volume of distribution and enhance renal clearance, inducing high intra- and inter-patient variability in beta-lactam concentration and promoting the risk of antibiotic underdosing. The duration of infusion of beta-lactams has been shown to influence the fT > minimal inhibitory concentration and an improved beta-lactam pharmacodynamics profile may be obtained by longer exposure with more frequent dosing, extended infusions, or continuous infusions.The use of extracorporeal support techniques in the critically ill may further contribute to this problem and we recommend not reducing standard antibiotic dosage since no drug accumulation was found in the available literature and to maintain continuous or prolonged infusion, especially for the treatment of infections caused by multidrug-resistant bacteria.Prediction of outcome based on concentrations in plasma results in overestimation of antimicrobial activity at the site of infection, namely in cerebrospinal fluid and the lung. Therefore, although no studies have assessed clinical outcome, we recommend using higher than standard dosing, preferably with continuous or prolonged infusions, especially when treating less susceptible bacterial strains at these sites, as the pharmacodynamics profile may improve with no apparent increase in toxicity.A therapeutic drug monitoring-guided approach could be particularly useful in critically ill patients in whom achieving target concentrations is more difficult, such as obese patients, immunocompromised patients, those infected by highly resistant bacterial strains, patients with augmented renal clearance, and those undergoing extracorporeal support techniques.

Population Pharmacokinetics and Dosing Regimen Optimization of Meropenem in Cerebrospinal Fluid and Plasma in Patients with Meningitis after Neurosurgery

Meropenem is used to manage postneurosurgical meningitis, but its population pharmacokinetics (PPK) in plasma and cerebrospinal fluid (CSF) in this patient group are not well-known. Our aims were to (i) characterize meropenem PPK in plasma and CSF and (ii) recommend favorable dosing regimens in postneurosurgical meningitis patients. Eighty-two patients were enrolled to receive meropenem infusions of 2 g every 8 h (q8h), 1 g q8h, or 1 g q6h for at least 3 days. Serial blood and CSF samples were collected, and concentrations were determined and analyzed via population modeling. Probabilities of target attainment (PTA) were predicted via Monte Carlo simulations, using the target of unbound meropenem concentrations above the MICs for at least 40% of dosing intervals in plasma and at least of 50% or 100% of dosing intervals in CSF. A two-compartment model plus another CSF compartment best described the data. The central, intercentral/peripheral, and intercentral/CSF compartment clearances were 22.2 liters/h, 1.79 liters/h, and 0.01 liter/h, respectively. Distribution volumes of the central and peripheral compartments were 17.9 liters and 3.84 liters, respectively. The CSF compartment volume was fixed at 0.13 liter, with its clearance calculated by the observed drainage amount. The multiplier for the transfer from the central to the CSF compartment was 0.172. Simulation results show that the PTAs increase as infusion is prolonged and as the daily CSF drainage volume decreases. A 4-hour infusion of 2 g q8h with CSF drainage of less than 150 ml/day, which provides a PTA of >90% for MICs of ≤8 mg/liter in blood and of ≤0.5 mg/liter or 0.25 mg/liter in CSF, is recommended. (This study has been registered at ClinicalTrials.gov under identifier NCT02506686.)

Success With Extended-Infusion Meropenem After Recurrence of Baclofen Pump-Related Achromobacter Xylosoxidans Meningitis in an Adolescent

A 13-year-old female experienced a recurrence of baclofen pump-related central nervous system (CNS) infection caused by Achromobacter, despite absence of retained foreign material. Due to the failure of meropenem (120 mg/kg/d in divided doses every 8 hours and infused over 30 minutes) in the initial infection, the dose was infused over 4 hours during the recurrence. Meropenem is an antibiotic for which efficacy is time dependent, and 4-hour versus 30-minute infusions have been shown to prolong the time the concentration of the antibiotic exceeds the minimum inhibitory concentration (MIC) of the organism at the site of infection (T>MIC). Meropenem serum concentrations were obtained and indicated that T>MIC was at least 75% of the dosing interval. Our patient improved with no noted recurrences or adverse effects on the extended-infusion meropenem regimen. Utilization of extended-infusion beta-lactam dosing whenever possible in the treatment of serious infections caused by gram-negative organisms should be considered, as this dosing appears to be safe and improves the probability of achieving pharmacokinetic/pharmacodynamic goals.

The effect of borneol on the concentration of meropenem in rat brain and blood

Meropenem is a carbapenem antibiotic with a wide spectrum of activity against both Gram-positive and Gram-negative bacteria. Because of its clinical efficacy, meropenem is an excellent choice for the treatment of serious infections in both adults and children. The knowledge of tissue concentrations of antibiotic in an infection site is valuable for the prediction of treatment outcome. The aim of the present study is to investigate the effect of borneol on the concentration of meropenem in rat brain and blood and to find the potential relationships of the combined use of medicine and traditional Chinese medicine. Analysis of meropenem in the dialysates was achieved using the microdialysis technique and HPLC. At 40 min after the administration of an intraperitoneal injection of meropenem, the concentration of meropenem in brain in borneol+meropenem group was 2.25 (0.35) μg ml(-1), which was significantly higher than that in meropenem group [1.20 (0.12) μg ml(-1); P < 0.01]. Within 80 min of drug administration, the AUCbrain/AUCblood (area under the curve, AUC) in the borneol+meropenem group was 1.2 times that of the meropenem group. Borneol can increase the concentration of meropenem in the cerebrospinal fluid, but has no influence on its blood concentration. This study represents a successful application of the microdialysis technique, which is an effective method for the study of pharmacokinetics of meropenem.

Carbapenems in the USA: focus on doripenem

The threat of antibacterial resistance continues to increase globally, and therapeutic options for the treatment of some serious infectious diseases are diminishing. The carbapenems are a potent class of broad-spectrum drugs, and their stability against hydrolysis by many important beta-lactamases make them an important weapon in the treatment of beta-lactamase-producing bacterial pathogens. This review focuses on four carbapenems of clinical importance in the USA: imipenem, meropenem, ertapenem and doripenem. After a historical review of carbapenem development, these four carbapenems are evaluated based on their mechanism of action, spectrum of activity, potency, pharmacodynamics, clinical pharmacokinetics, clinical profiles and toxicity issues.

Serratia marcescens spinal epidural abscess formation following acupuncture

The formation of spinal epidural abscess following acupuncture is very rare. We herein report the case of a 54-year-old woman who presented with progressive low back pain and fever with a root sign. She underwent surgical decompression, with an immediate improvement of the low back pain. A culture of the epidural abscess grew Serratia marcescens. One year postoperatively, magnetic resonance imaging revealed the almost complete eradication of the abscess. This case is the first case of Serratia marcescens-associated spinal epidural abscess formation secondary to acupuncture. The characteristics of spinal epidural abscess that develop after acupuncture and how to prevent such complications are also discussed.

Continuous versus intermittent infusions of antibiotics for the treatment of severe acute infections

BACKGROUND

Intravenous broad-spectrum antibiotics are indicated for the treatment of severe infections. However, the emergence of infections caused by multi-drug resistant organisms in conjunction with a lack of novel antibiotics has prompted the investigation of alternative dosing strategies to improve clinical efficacy and tolerability. To optimise pharmacokinetic and pharmacodynamic antibiotic parameters, continuous antibiotic infusions have been compared to traditional intermittent antibiotic infusions.

OBJECTIVES

To compare the clinical efficacy and safety of continuous intravenous administration of concentration-dependent and time-dependent antibiotics to traditional intermittent intravenous administration in adults with severe acute bacterial infections.

SEARCH METHODS

The following electronic databases were searched in September 2012: The Cochrane Injuries Group Specialised Register, Cochrane Central Register of Controlled Trials (The Cochrane Library), MEDLINE (OvidSP), EMBASE (OvidSP), CINAHL, ISI Web of Science: Science Citation Index Expanded (SCI-EXPANDED), ISI Web of Science: Conference Proceedings Citation Index-Science (CPCI-S). The reference lists of all relevant material, the Internet and the trials registry www.clinicaltrials.gov for completed and ongoing trials were also searched.

SELECTION CRITERIA

Randomized controlled trials in adults with a bacterial infection requiring intravenous antibiotic therapy comparing continuous versus intermittent infusions of antibiotics were included. Both time-dependent and concentration-dependent antibiotics were considered.

DATA COLLECTION AND ANALYSIS

Three independent authors performed data extraction for the included studies. All data was cross-checked and disagreements resolved by consensus. An intention to treat analysis was conducted using a random-effects model.

MAIN RESULTS

Twenty-nine studies met inclusion criteria with a combined total of over 1,600 patients. The majority of included studies were judged to be at unclear or high risk of bias with regard to randomisation sequence generation, allocation concealment, blinding, management of incomplete outcome data, selective outcome reporting, and other potential threats to validity. No studies were judged to be at low risk of bias for all methodological quality items assessed. There were no differences in all-cause mortality (n=1241, RR 0.89, 95% CI 0.67 - 1.20, p=0.45), infection recurrence (n=398, RR 1.22, 95% CI 0.35 - 4.19, p=0.76), clinical cure (n=975, RR 1.00, 95% CI 0.93 - 1.08, p=0.98), and superinfection post-therapy (n=813, RR 1.08, 95% CI 0.60 - 1.94, p=0.79). There were no differences in safety outcomes including adverse events (n=575, RR 1.02, 95% CI 0.94 - 1.12, p=0.63), serious adverse events (n=871, RR 1.36, 95% CI 0.80 - 2.30, p=0.26), and withdrawal due to adverse events (n=871, RR 2.03, 95% CI 0.52 - 7.95, p=0.31). A difference was observed in the subgroup analyses of clinical cure in septic versus non-septic patients, where intermittent antibiotic infusions were favoured for clinical cure in septic patients. However, this effect was not consistent between random-effects and fixed-effects analyses. No differences were found in sensitivity analyses conducted.

AUTHORS' CONCLUSIONS

There were no differences in mortality, infection recurrence, clinical cure, superinfection post-therapy, and safety outcomes when comparing continuous infusions of intravenous antibiotics to traditional intermittent infusions of antibiotics. However, the wide confidence intervals suggest that beneficial or harmful effects cannot be ruled out for all outcomes. Therefore, the current evidence is insufficient to recommend the widespread adoption of continuous infusion antibiotics in the place of intermittent infusions of antibiotics. Further large prospective randomised trials, with consistent and complete reporting of clinical outcome measures, conducted with concurrent pharmacokinetic and pharmacodynamic studies in special populations are required to determine whether adoption of continuous antibiotic infusions is warranted in specific circumstances.