Real-Time Optimization of Pharmacodynamic Target Attainment at Infection Site during Treatment of Post-Neurosurgical Ventriculitis Caused by Carbapenem-Resistant Gram Negatives with Ceftazidime-Avibactam-Based Regimens: A Report of Two Cases

A Difficult Case of Ventriculitis in a 40-Year-Old Woman with Acute Myeloid Leukemia

Ventriculitis and nosocomial meningitis caused by carbapenem-resistant Gram-negative and vancomycin-resistant Gram-positive bacteria represent a growing treatment challenge. A case of ventriculitis and bacteremia caused by carbapenem-resistant, KPC-producing Klebsiella pneumoniae and vancomycin-resistant Enterococcus faecium in a young woman with acute leukemia who was successfully treated with meropenem/vaborbactam (MVB), rifampicin, and linezolid is described in this paper. This case report emphasizes the importance of a multidisciplinary strategy, including infectious focus control, for the treatment of device-associated central nervous system (CNS) infections from multidrug-resistant bacteria. Considering the novel resistance patterns, more research on drug penetration into the central nervous system, as well as on the necessity of association therapies, is needed.

Treatment of infections caused by multi-drug-resistant Gram-negative bacilli: A practical approach by the Italian (SIMIT) and French (SPILF) Societies of Infectious Diseases

INTRODUCTION

The emergence of multi-drug-resistant Gram-negative bacilli and the development of new antibiotics have complicated the selection of optimal regimens. International guidelines are valuable tools, but are limited by the scarcity of high-quality randomized trials in many situations.

METHODS

A panel of experts from the French and Italian Societies of Infectious Diseases aimed to address unresolved issues in clinical practice based on their experience, an updated literature review and open discussions.

RESULTS

The panel reached consensus for the following 'first choices': (i) cefepime for ventilator-acquired pneumonia due to AmpC β-lactamase-producing Enterobacterales; (ii) the β-lactam/β-lactamase inhibitor combination most active in vitro, or cefiderocol combined with fosfomycin, and aerosolized colistin or aminoglycosides, for severe pneumonia due to Pseudomonas aeruginosa resistant to ceftolozane-tazobactam; (iii) high-dose piperacillin-tazobactam (including loading dose and continuous infusion) for complicated urinary tract infections (cUTIs) caused by extended-spectrum β-lactamase-producing Enterobacterales with piperacillin-tazobactam minimum inhibitory concentration (MIC) ≤8 mg/L; (iv) high-dose cefepime for cUTIs due to AmpC β-lactamase-producing Enterobacterales other than Enterobacter spp. if cefepime MIC ≤2 mg/L; (v) ceftolozane-tazobactam or ceftazidime-avibactam plus metronidazole for intra-abdominal infections (IAIs) due to third-generation cephalosporin-resistant Enterobacterales; (vi) ceftazidime-avibactam plus aztreonam plus metronidazole for IAIs due to metallo-β-lactamase-producing Enterobacterales; (vii) ampicillin-sulbactam plus colistin for bloodstream infections (BSIs) caused by carbapenem-resistant Acinetobacter baumannii; (viii) meropenem-vaborbactam for BSIs caused by Klebsiella pneumoniae carbapenemase-producing Enterobacterales; and (ix) ceftazidime-avibactam plus fosfomycin for neurological infections caused by carbapenem-resistant P. aeruginosa.

CONCLUSIONS

These expert choices were based on the necessary balance between antimicrobial stewardship principles and the need to provide optimal treatment for individual patients in each situation.

Meropenem-Vaborbactam for the Treatment of Post-Neurosurgical Meningitis Caused by KPC Producer Klebsiella Pneumoniae: A Case Report and Review of the Literature

Meningitis and ventriculitis, due to carbapenem-resistant Enterobacterales, are frequently associated with significant morbidity and mortality. In the case of multi-drug-resistant pathogens, it is necessary to consider the limited susceptibility profile as well as the penetration of the antimicrobials into the brain. Limited data are available regarding the treatment of central nervous system infections caused by carbapenem-resistant Enterobacterales. We report a study of a patient treated with meropenem-vaborbactam in the case of post-neurosurgical meningitis due to carbapenemase-producing Klebsiella pneumoniae (CPKP).

The pharmacokinetics/pharmacodynamics of ceftazidime/avibactam for central nervous system infections caused by carbapenem-resistant Gram-negatives: a prospective study

OBJECTIVES

To describe the pharmacokinetics/pharmacodynamics (PK/PD) of ceftazidime/avibactam in critically ill patients with CNS infections.

METHODS

A prospective study of critically ill patients with CNS infections who were treated with ceftazidime/avibactam and the steady-state concentration (Css) of ceftazidime/avibactam in serum and/or CSF was conducted between August 2020 and May 2023. The relationship between PK/PD goal achievement, microbial eradication and the clinical efficacy of ceftazidime/avibactam was evaluated.

RESULTS

Seven patients were finally included. The ceftazidime/avibactam target attainment in plasma was optimal for three, quasi-optimal for one and suboptimal for three. In three patients with CSF drug concentrations measured, ceftazidime/avibactam target attainment in CSF was 100% (3/3), which was optimal. The AUCCSF/serum values were 0.59, 0.44 and 0.35 for ceftazidime and 0.57, 0.53 and 0.51 for avibactam. Of the seven patients, 100% (7/7) were treated effectively, 71.4% (5/7) achieved microbiological eradication, 85.7% (6/7) survived and 14.3% (1/7) did not survive.

CONCLUSIONS

The limited clinical data suggest that ceftazidime/avibactam is effective in the treatment of CNS infections caused by MDR Gram-negative bacilli (MDR-GNB), can achieve the ideal drug concentration of CSF, and has good blood-brain barrier penetration.

Intravenous Fosfomycin for Systemic Multidrug-Resistant Pseudomonas aeruginosa Infections

Human Pseudomonas infections have high morbidity and mortality rates. Pseudomonas bacteria can cause sepsis or septic shock; they produce biofilm and commonly exhibit a multidrug-resistant phenotype. The choice of antimicrobial therapy in many cases is challenging, and deep knowledge of clinical, microbiological, and pharmacological issues is required. Intravenous fosfomycin is being repurposed in a combination given its favorable pharmacokinetic/pharmacodynamic properties (a small molecule with favorable kinetic both in bloodstream infection and in deep-seated infections), antibiofilm activity, and its interesting synergistic effects with other antimicrobials. Recent literature on epidemiological, microbiological, pharmacological, and clinical data on intravenous fosfomycin therapy against Pseudomonas is herein reviewed and discussed.

Treatment of Ventriculitis and Meningitis After Neurosurgery Caused by Carbapenem-Resistant Enterobacteriaceae (CRE): A Challenging Topic

Post-neurosurgical infection is a common complication of neurosurgery, and serious infection can threaten the life of patients. In recent years, the increase in multidrug-resistant bacteria, especially carbapenem-resistant Enterobacteriaceae (CRE), has proved fatal to patients. Although there are a few cases of CRE meningitis and few clinical trials have been carried out, it has attracted increasing attention with the increasing probability of its occurrence, especially considering that there are few successful cases. An increasing number of studies are also looking for the risk factors and clinical symptoms of CRE intracranial infection. In terms of treatment, some new antibiotics are gradually being used in the clinic, but due to the complicated drug-resistant mechanism of CRE and the obstruction of the blood‒brain barrier (BBB), the therapeutic effect is still very poor. In addition, obstructive hydrocephalus and brain abscess caused by CRE meningitis are still important causes of patient death and are also difficult to treat.

Performance of Ceftazidime-Avibactam 30/20-μg and 10/4-μg Disks for Susceptibility Testing of Enterobacterales and Pseudomonas aeruginosa

Ceftazidime-avibactam, a new β-lactam-β-lactamase inhibitor combination, is active against multidrug-resistant Enterobacterales and Pseudomonas aeruginosa isolates and has became available for clinical use in China in the latter half of 2019. In this study, we evaluated the performance of the disk diffusion test with ceftazidime-avibactam 10/4-μg and 30/20-μg disks, compared with the reference broth microdilution method, with a collection of 467 Enterobacterales and 182 P. aeruginosa nonduplicate clinical isolates. The results of antimicrobial susceptibility testing indicated that the categorical agreement (CA) of ceftazidime-avibactam 10/4-μg disk testing for all tested Enterobacterales isolates was 99.8%, with 0.5% very major errors (VMEs) and no major error (ME). The CA of ceftazidime-avibactam 10/4-μg disk testing for all tested P. aeruginosa isolates was 87.9%, with 15.5% MEs and no VME. The CA of ceftazidime-avibactam 30/20-μg disk testing for all tested Enterobacterales isolates was 99.4%, with 1.5% VMEs and no ME. The CA of ceftazidime-avibactam 30/20-μg disk testing for all tested P. aeruginosa isolates was 91.8%, with 2.5% VMEs and 9.9% MEs. Overall, ceftazidime-avibactam 10/4-μg disk testing showed superior performance and was more suitable for assessment of the susceptibility of Enterobacterales and P. aeruginosa isolates. IMPORTANCE Multidrug-resistant Enterobacterales and P. aeruginosa strains have become a global public threat, with the emergence and prevalence of plasmid-mediated extended-spectrum β-lactamases (ESBLs), AmpC cephalosporinases, and carbapenemases disseminated worldwide. Ceftazidime-avibactam, which is commercially available, has shown excellent in vitro activity against multidrug-resistant and carbapenem-resistant Enterobacterales and P. aeruginosa isolates. Moreover, ceftazidime-avibactam has shown promise in treating infections caused by multidrug-resistant and carbapenem-resistant isolates. The disk diffusion test for ceftazidime-avibactam is the most common antimicrobial susceptibility testing method in most laboratories in China. The accurate detection of ceftazidime-avibactam susceptibility is of great significance for the rational clinical application of drugs. Here, we evaluated the performance of the ceftazidime-avibactam 10/4-μg and 30/20-μg disk diffusion tests, compared with the reference broth microdilution method, with clinical Enterobacterales and P. aeruginosa isolates.

Jumping into the future: overcoming pharmacokinetic/pharmacodynamic hurdles to optimize the treatment of severe difficult to treat-Gram-negative infections with novel beta-lactams

INTRODUCTION

The choice of best therapeutic strategy for difficult-to-treat resistance (DTR) Gram-negative infections currently represents an unmet clinical need.

AREAS COVERED

This review provides a critical reappraisal of real-world evidence supporting the role of pharmacokinetic/pharmacodynamic (PK/PD) optimization of novel beta-lactams in the management of DTR Gram-negative infections. The aim was to focus on prolonged and/or continuous infusion administration, penetration rates into deep-seated infections, and maximization of PK/PD targets in special renal patient populations. Retrieved findings were applied to the three most critical clinical scenarios of Gram-negative resistance phenotypes (i.e. carbapenem-resistant Enterobacterales; difficult-to-treat resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii).

EXPERT OPINION

Several studies supported the role of PK/PD optimization of beta-lactams in the management of DTR Gram-negative infections for both maximizing clinical efficacy and preventing resistance emergence. Optimizing antimicrobial therapy with novel beta-lactams based on the so called 'antimicrobial therapy puzzle' PK/PD concepts may represent a definitive jump into the future toward a personalized patient management of DTR Gram negative infections. Establishing a dedicated and coordinated multidisciplinary team and implementing a real-time TDM-guided personalized antimicrobial exposure optimization of novel beta-lactams based on expert clinical pharmacological interpretation, could represent crucial cornerstones for the proper management of DTR Gram-negative infections.

Ceftazidime-Avibactam Treatment for Severe Post-Neurosurgical Meningitis and Abscess Caused by Extended-Spectrum β-Lactamase Escherichia coli in a Pediatric Patient: A Case Report

Post-neurosurgical infections caused by multidrug-resistant Enterobacterales are difficult to treat due to limited therapeutic options. Ceftazidime-avibactam (CAZ-AVI), a combination of cephalosporin and a novel β-lactamase inhibitor, has exhibited potential activity against multi/extensive drug-resistant (MDR/XDR) gram-negative bacilli. Several reports have described the successful treatment of central infections caused by MDR/XDR Pseudomonas aeruginosa or Enterobacterales. However, data on the efficacy and effective drug distribution of CAZ-AVI in the central nervous system (CNS), particularly in children, are lacking. We report a case of a 4-year-old girl with post-neurosurgical meningitis and abscess caused by extended-spectrum β-lactamase-producing Escherichia coli successfully treated with CAZ-AVI. CAZ-AVI therapeutic drug monitoring was performed to evaluate its efficacy and effective drug distribution in the CNS. We measured CAZ (15.6, 7.1, and 3.5 μg/mL) and AVI (4.0, 2.1, and 1.2 μg/mL) in cerebrospinal fluid (CSF) samples obtained 3, 5, and 7 h after the administration of the 15th CAZ-AVI dose (2.5 g, q8h, iv), respectively. We also measured CAZ (57.0 and 25.8 μg/mL) and AVI (11.3 and 4.5 μg/mL) in serum samples obtained 3 and 5 h after the administration, respectively. CAZ-AVI achieved an adequate CSF concentration throughout the drug interval. Our case provides evidence for using CAZ-AVI to treat CNS infections.

The Blood-Brain Barrier and Pharmacokinetic/Pharmacodynamic Optimization of Antibiotics for the Treatment of Central Nervous System Infections in Adults

Bacterial central nervous system (CNS) infections are serious and carry significant morbidity and mortality. They encompass many syndromes, the most common being meningitis, which may occur spontaneously or as a consequence of neurosurgical procedures. Many classes of antimicrobials are in clinical use for therapy of CNS infections, some with established roles and indications, others with experimental reporting based on case studies or small series. This review delves into the specifics of the commonly utilized antibacterial agents, updating their therapeutic use in CNS infections from the pharmacokinetic and pharmacodynamic perspectives, with a focus on the optimization of dosing and route of administration that have been described to achieve good clinical outcomes. We also provide a concise synopsis regarding the most focused, clinically relevant information as pertains to each class and subclass of antimicrobial therapeutics. CNS infection morbidity and mortality remain high, and aggressive management is critical in ensuring favorable patient outcomes while averting toxicity and upholding patient safety.

Pharmacokinetic/Pharmacodynamic Analysis of Continuous-Infusion Fosfomycin in Combination with Extended-Infusion Cefiderocol or Continuous-Infusion Ceftazidime-Avibactam in a Case Series of Difficult-to-Treat Resistant Pseudomonas aeruginosa Bloodstream Infections and/or Hospital-Acquired Pneumonia

Objectives: To perform a pharmacokinetic/pharmacodynamic (PK/PD) analysis of continuous-infusion (CI) fosfomycin combined with extended-infusion (EI) cefiderocol or CI ceftazidime-avibactam in a case series of severe difficult-to-treat Pseudomonas aeruginosa (DTR-PA) infections. Methods: A single-center retrospective study of patients who were treated with CI fosfomycin plus EI cefiderocol or CI ceftazidime-avibactam for severe DTR-PA infections and who underwent therapeutic drug monitoring (TDM), from 1 September 2021 to 30 June 2022 was performed. Concentrations were measured at steady-state (Css) for CI fosfomycin and ceftazidime-avibactam and at trough (Cmin) for EI cefiderocol. Joint PK/PD targets of combination therapy were analyzed (thresholds: area-under-the curve to minimum inhibitory concentration (AUC/MIC) ratio > 40.8 for fosfomycin; ceftazidime Css/MIC ratio ≥ 4 coupled with avibactam Css > 4 mg/L for ceftazidime-avibactam; Cmin/MIC ratio ≥ 4 for cefiderocol). Joint PK/PD targets of the combination therapy were analyzed and defined as optimal when both were achieved, quasi-optimal if only one of the two was achieved, and suboptimal if none of the two was achieved). The relationship between joint PK/PD target attainment and microbiological response was assessed. Results: Six patients (three pneumonia, two BSI + pneumonia, and one BSI) were included. The joint PK/PD targets were optimal in four cases and quasi-optimal in the other two. Microbiological eradication (ME) occurred in 4/4 of patients with optimal joint PK/PD targets and in one of the two patients with quasi-optimal joint PK/PD targets. Conclusions: Attaining optimal joint PK/PD targets with a combo-therapy of CI fosfomycin plus EI cefiderocol or CI ceftazidime-avibactam could represent an effective strategy for granting favorable microbiological outcomes in patients with DTR-PA pneumonia and/or BSI.

Healthcare-associated central nervous system infections

PURPOSE OF REVIEW

The aim of this review is to provide a practical and updated summary on healthcare-associated central nervous system infections and their management.

RECENT FINDINGS

The term 'healthcare-associated ventriculitis and meningitis' has recently been coined and clinical practical guidelines have been published on the management of these nosocomial infections. Many aspects have still to be further investigated (e.g. cerebrospinal fluid biomarkers, indications for novel antibiotics, intrathecal antimicrobial regimens).

SUMMARY

Clinicians should maintain a high index of suspicion for healthcare-associated central nervous system infections in patients with specific risk factors (i.e. recent neurosurgery, cerebrospinal shunts, drains or implantable devices, head/spinal traumatic events), taking into account systemic signs, and alterations in microbiological, imaging, cerebrospinal fluid findings. The diagnosis is often difficult to confirm because of reduced levels of consciousness or coma. Both Gram-positive and Gram-negative (often multidrug-resistant or even pandrug-resistant) microorganisms may be the cause. Selection of antibiotics must consider susceptibility and penetration into the central nervous system. Ineffective treatments are frequent, and mortality can reach 60%. Future research should focus on the diagnostic performance of biomarkers and on the use of novel antimicrobial regimens, especially for the treatment of difficult to treat infections.

A Post-Neurosurgical Infection due to KPC-Producing Klebsiella pneumoniae Treated with Meropenem-Vaborbactam: A Case Report

This case report describes a patient with a KPC-producing K. pneumoniae post-neurosurgical infection with bacteremia. There is limited evidence to guide antibiotic treatment decisions for such infections. The patient was treated with meropenem-vaborbactam. Meropenem-vaborbactam monotherapy was associated with bacteremia clearance.

Update of clinical application in ceftazidime-avibactam for multidrug-resistant Gram-negative bacteria infections

PURPOSE

Multidrug-resistant Gram-negative bacteria (MDR-GNB) have become a major global public health threat. Ceftazidime-avibactam (CAZ-AVI) is a newer combination of β-lactam/β-lactamase inhibitor, with activity against carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA). The aim of this review is to describe the recent real-world experience of CAZ-AVI for the infections due to MDR-GNB.

METHODS

We searched PubMed, Embase and Google Scholar for clinical application in CAZ-AVI for MDR-GNB infections. Reference lists were reviewed and synthesized for narrative review.

RESULTS

MDRGNB infections are associated with higher mortality significantly comparing to drug-susceptible bacterial infections. Fortunately, CAZ-AVI shows significant benefits for infections due to KPC or OXA-48 CRE, comparing to colistin, carbapenem, aminoglycoside and other older agents, even in those with immunocompromised status. The efficacy of CAZ-AVI varies in different infection sites due to CRE, which is lower in pneumonia. Early use is associated with improved clinical outcomes. Noteworthy, when adopted as salvage therapy, CAZ-AVI is still superior to other GNB active antibiotics. CAZ-AVI plus aztreonam is recommended as the first line of MBL-CRE infections. However, for infections caused by KPC- and OXA-48-producing isolates, further investigations are needed to demonstrate the benefit of combination therapy. Besides CRE, CAZ-AVI is also active to MDR-PA. However, the development of resistance in CRE and MDR-PA against CAZ-AVI is alarming, and more investigations and studies are needed to prevent, diagnose, and treat infections due to CAZ-AVI-resistant pathogens.

CONCLUSIONS

CAZ-AVI appears to be a valuable therapeutic option in MDR-GNB infections. Using CAZ-AVI appropriately to improve efficacy and decrease the emergence of resistance is important.