The Use of Therapeutic Drug Monitoring to Optimize Treatment of Carbapenem-Resistant Enterobacter Osteomyelitis

A Systematic Review of the Effect of Therapeutic Drug Monitoring on Patient Health Outcomes during Treatment with Carbapenems

Adjusting dosing regimens based on measurements of carbapenem levels may improve carbapenem exposure in patients. This systematic review aims to describe the effect carbapenem therapeutic drug monitoring (TDM) has on health outcomes, including the emergence of antimicrobial resistance (AMR). Four databases were searched for studies that reported health outcomes following adjustment to dosing regimens, according to measurements of carbapenem concentration. Bias in the studies was assessed with risk of bias analysis tools. Study characteristics and outcomes were tabulated and a narrative synthesis was performed. In total, 2 randomised controlled trials (RCTs), 17 non-randomised studies, and 19 clinical case studies were included. Significant variation in TDM practice was seen; consequently, a meta-analysis was unsuitable. Few studies assessed impacts on AMR. No significant improvement on health outcomes and no detrimental effects of carbapenem TDM were observed. Five cohort studies showed significant associations between achieving target concentrations and clinical success, including suppression of resistance. Studies in this review showed no obvious improvement in clinical outcomes when TDM is implemented. Optimisation and standardisation of carbapenem TDM practice are needed to improve intervention success and enable study synthesis. Further suitably powered studies of standardised TDM are required to assess the impact of TMD on clinical outcomes and AMR.

Efficacy of generic meropenem products in combination with colistin in carbapenemase-producing Klebsiella pneumoniae experimental osteomyelitis

Guidelines for the management of carbapenemase-producing Enterobacterales (CPE) infections recommend a combination of two active agents, including meropenem if the minimum inhibitory concentration (MIC) is ≤8 mg/L. The therapeutic equivalence of meropenem generics has been challenged. We compared the bactericidal activity of meropenem innovator (AstraZeneca) and four generic products (Actavis, Kabi, Mylan and Panpharma), both in vitro and in vivo, in association with colistin. In vitro time-kill studies were performed at 4 × MIC. An experimental model of KPC-producing Klebsiella pneumoniae osteomyelitis was induced in rabbits by tibial injection of a sclerosing agent followed by 2 × 10⁸ CFU of K. pneumoniae KPC-99YC (meropenem MIC = 4 mg/L; colistin MIC = 1 mg/L). At 14 days after inoculation, treatment for 7 days started in seven groups of ≥10 rabbits, including a control group, a colistin group, and one group for each meropenem product (i.e. the innovator and four generics), in combination with colistin. In vitro, meropenem + colistin was bactericidal with no viable bacteria after 6 h, and this effect was similar with all meropenem products. In the osteomyelitis model, there was no significant difference between meropenem generics and the innovator when combined with colistin. Colistin-resistant strains were detected after treatment with colistin + meropenem innovator (n = 3) and generics (n = 3). The efficacy of four meropenem generics did not differ from the innovator in vitro and in an experimental rabbit model of KPC-producing K. pneumoniae osteomyelitis in terms of bactericidal activity and the emergence of resistance.

Case series of carbapenemase-producing Enterobacteriaceae osteomyelitis: Feel it in your bones

OBJECTIVES

Limited data have been reported regarding osteomyelitis due to carbapenemase-producing Enterobacteriaceae (CPE), including co-infections with extended-spectrum β-lactamase (ESBL)-producing micro-organisms.

METHODS

We conducted a retrospective study in a reference centre for bone and joint infections from 2011 to 2019 among patients infected with CPE.

RESULTS

Nine patients (mean age 46.8 ± 16.6 years), including three with infected implants, were identified. Infections were mostly polymicrobial (n = 8/9), including Staphylococcus aureus (n = 6/9). CPE were mainly OXA-48-type, associated with ESBL-producing Enterobacteriaceae (n = 8/9), of which 5/9 isolates were Klebsiella pneumoniae. Control of the infection was achieved in seven cases.

CONCLUSIONS

CPE osteomyelitides are essentially polymicrobial and fluoroquinolone-resistant infections, highlighting the need for efficient surgery with implant removal.

Contemporaneous management of ampicillin infusions in the outpatient setting through the use of therapeutic drug monitoring

The use of ampicillin in the outpatient setting has traditionally been avoided because of the short half-life and instability in solution of this drug. However, recent in vitro data and two case series support the safe and effective administration of ampicillin by continuous infusion in the community. Therapeutic drug monitoring (TDM) of beta-lactam antibiotics can be used to optimise antibiotic exposure and ensure adequate clinical responses. A case series is presented of patients receiving ampicillin via prolonged infusion in the outpatient setting, with TDM to ensure adequate plasma antibiotic levels were achieved. Three patients who received ampicillin by continuous infusion under the Outpatient Parenteral Antimicrobial Therapy (OPAT) program are described, including details of antibiotic dose and steady-state plasma drug concentration as measured by high-performance liquid chromatography. All three patients had an infection with ampicillin-susceptible Enterococcus faecalis; one patient had post-partum endometritis, one had urosepsis and one had a complex polymicrobial bone and joint infection. Adequate plasma drug levels were achieved in all patients. Management of the antibiotic temperature and infusion times, and appropriate timing of drug levels in the community were required. Two patients achieved clinical cure, while the third required further surgical debridement and antibiotic therapy. TDM in this setting enabled the contemporaneous management and dose alteration of ampicillin. Ampicillin may be a safe and effective drug when administered by continuous infusion with appropriate TDM in the community setting.

Using machine learning to optimize antibiotic combinations: dosing strategies for meropenem and polymyxin B against carbapenem-resistant Acinetobacter baumannii

OBJECTIVES

Increased rates of carbapenem-resistant strains of Acinetobacter baumannii have forced clinicians to rely upon last-line agents, such as the polymyxins, or empirical, unoptimized combination therapy. Therefore, the objectives of this study were: (a) to evaluate the in vitro pharmacodynamics of meropenem and polymyxin B (PMB) combinations against A. baumannii; (b) to utilize a mechanism-based mathematical model to quantify bacterial killing; and (c) to develop a genetic algorithm (GA) to define optimal dosing strategies for meropenem and PMB.

METHODS

A. baumannii (N16870; MIC_meropenem = 16 mg/L, MIC_PMB = 0.5 mg/L) was studied in the hollow-fibre infection model (initial inoculum 10⁸ cfu/mL) over 14 days against meropenem and PMB combinations. A mechanism-based model of the data and population pharmacokinetics of each drug were used to develop a GA to define the optimal regimen parameters.

RESULTS

Monotherapies resulted in regrowth to ~10¹⁰ cfu/mL by 24 h, while combination regimens employing high-intensity PMB exposure achieved complete bacterial eradication (0 cfu/mL) by 336 h. The mechanism-based model demonstrated an SC₅₀ (PMB concentration for 50% of maximum synergy on meropenem killing) of 0.0927 mg/L for PMB-susceptible subpopulations versus 3.40 mg/L for PMB-resistant subpopulations. The GA had a preference for meropenem regimens that improved the %T > MIC via longer infusion times and shorter dosing intervals. The GA predicted that treating 90% of simulated subjects harbouring a 10⁸ cfu/mL starting inoculum to a point of 10⁰ cfu/mL would require a regimen of meropenem 19.6 g/day 2 h prolonged infusion (2 hPI) q5h + PMB 5.17 mg/kg/day 2 hPI q6h (where the 0 h meropenem and PMB doses should be 'loaded' with 80.5% and 42.2% of the daily dose, respectively).

CONCLUSION

This study provides a methodology leveraging in vitro experimental data, a mathematical pharmacodynamic model, and population pharmacokinetics provide a possible avenue to optimize treatment regimens beyond the use of the 'traditional' indices of antibiotic action.

The impact of carbapenem resistance on clinical deterioration and mortality in patients with liver disease

BACKGROUND & AIMS

Infections with multidrug-resistant gram-negative bacteria are significantly impairing the prognosis of patients with liver disease. In particular, carbapenem resistance further narrows therapeutic options. This study investigates the impact of carbapenem-resistant gram-negative bacteria on the outcome of patients with liver disease and cirrhosis.

METHODS

Between January 2011 and July 2015, 132 patients treated at the tertiary liver transplant centre at University Hospital Frankfurt, Germany, were tested positive for carbapenem-resistant gram-negative bacteria and retrospectively analysed in this study. Risk factors for fatal outcome were evaluated using multivariate regression analysis. Competing-risk analysis was performed on patients tested positive for Enterobacteriaceae or non-fermenting species, for example, Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophilia. Subgroup analysis of cirrhotic patients was performed on a matched cohort of cirrhotic patients, comparable model for end-stage liver disease and tested negative for carbapenem-resistant gram-negative bacteria.

RESULTS

97 (73.5%) and 35 (26.5%) patients were infected or colonised with carbapenem-resistant gram-negative bacteria respectively. Within the observation period, 61/132 (46.2%) patients died, with sepsis being the leading cause (38/61, 62.3%). Decompensated liver disease, sepsis and admission to intensive care unit were independent risk factors for fatal outcome. Lethal sepsis in patients positive for non-fermenting bacteria was significantly more frequent than in those positive for Enterobacteriaceae, independently from liver function. Subgroup analysis of cirrhotic patients showed that sepsis (54.9% vs 13%) and lethal sepsis were significantly more frequent after detection of carbapenem-resistant gram-negative bacteria, independently from localisation of pathogen detection.

CONCLUSIONS

Patients with advanced liver disease are prone to fatal infections caused by carbapenem-resistant gram-negative bacteria.

Extended infusion of beta-lactam antibiotics: optimizing therapy in critically-ill patients in the era of antimicrobial resistance

INTRODUCTION

Beta-lactams are at the cornerstone of therapy in critical care settings, but their clinical efficacy is challenged by the rise in bacterial resistance. Infections with multi-drug resistant organisms are frequent in intensive care units, posing significant therapeutic challenges. The problem is compounded by a dearth in the development of new antibiotics. In addition, critically-ill patients have unique physiologic characteristics that alter the drugs pharmacokinetics and pharmacodynamics. Areas covered: The prolonged infusion of antibiotics (extended infusion [EI] and continuous infusion [CI]) has been the focus of research in the last decade. As beta-lactams have time-dependent killing characteristics that are altered in critically-ill patients, prolonged infusion is an attractive approach to maximize their drug delivery and efficacy. Several studies have compared traditional dosing to EI/CI of beta-lactams with regard to clinical efficacy. Clinical data are primarily composed of retrospective studies and some randomized controlled trials. Several reports show promising results. Expert commentary: Reviewing the currently available evidence, we conclude that EI/CI is probably beneficial in the treatment of critically-ill patients in whom an organism has been identified, particularly those with respiratory infections. Further studies are needed to evaluate the efficacy of EI/CI in the management of infections with resistant organisms.