Effectiveness and safety of high-dose tigecycline-containing regimens for the treatment of severe bacterial infections

Evaluating tigecycline dosing for hospital-acquired pneumonia patients: insights from physiologically-based pharmacokinetic modeling of lung exposure

Tigecycline is increasingly used off-label for hospital-acquired pneumonia (HAP), though its efficacy and optimal dosing remain uncertain. Lung exposure to tigecycline may be affected by pulmonary pH changes induced by bacterial infections. This study used a physiologically -based pharmacokinetic (PBPK) model to evaluate the impact of pH shifts on lung exposure and assess the efficacy of various dosing regimens. A lung PBPK model for tigecycline was developed and validated using plasma and lung concentration data from clinical pharmacokinetic studies. Simulations evaluated the impact of pH alterations from 6.6 (healthy) to 5.6 (infection) on lung exposure. Three clinical dosing regimens-standard (100 mg loading dose +50 mg q12h), median (150 mg loading dose +75 mg q12h), and high dose (200 mg loading dose +100 mg q12h)-were assessed by calculating the probability of target attainment (PTA) in lung compartments, including epithelial lining fluid (ELF) and alveolar cells (ACs), across a MIC range of 0.125-32 mg/L. The model reasonably captured tigecycline exposure in plasma and lung. Pulmonary pH alterations had minimal impact on tigecycline AUC in ELF but led to a significant 12.39-fold increase in AUC within ACs at pH 5.6. For pathogens with MIC ≤1 mg/L, all three dosing regimens achieved PTA ≥90% in ELF. However, for MIC >2 mg/L, only the high-dose regimen provided satisfactory PTA. The lung PBPK model provides valuable insights into tigecycline PK in HAP patients and underscores the need to optimize dosing for pneumonia with resistant pathogens.

Identification of Risk Factors and Predictive Indicators for Tigecycline-Associated Hypofibrinogenemia

To investigate the prevalence, clinical manifestations, and risk factors of hypofibrinogenemia after tigecycline use, which can disrupt coagulation and potentially hinder antimicrobial therapy. This observational study was conducted from January to December 2021 at a tertiary general hospital in China. All patients over 18 years old who received tigecycline for more than 48 h were included. After treatment with tigecycline, patients were divided into two groups based on fibrinogen plasma concentrations of less than 2.0 g/L. Multivariable logistic regression was performed to identify risk factors for hypofibrinogenemia associated with tigecycline. A total of 50 patients (mean age 71.3 ± 20.2 years) were analyzed. The median duration of treatment was 8 days (range: 3 to 20 days). Among the 24 patients who developed hypofibrinogenemia, three gastrointestinal bleeding events were observed, and four of these patients required fibrinogen administration. We identified the total therapeutic dose (odds ratio (OR) = 15.28, 95% confidence interval (CI) 2.10-111.02, p = 0.01) and a baseline direct bilirubin level greater than 0.4 mg/dL (OR = 5.79, 95% CI 1.13-27.98, p = 0.04) as risk factors for tigecycline-induced hypofibrinogenemia. Conversely, a baseline fibrinogen level (OR = 0.53, 95% CI 0.29-0.97, p = 0.04) appeared to be a protective factor. Healthcare professionals should be aware that the administration of tigecycline may be associated with hypofibrinogenemia and severe adverse reactions. Regular monitoring of coagulation is essential, particularly for patients with liver dysfunction, low baseline fibrinogen levels, elevated baseline direct bilirubin levels, or those receiving higher total therapeutic doses.

Pharmacokinetic/pharmacodynamic evaluation of tigecycline dosing in a hollow fiber infection model against clinical bla-KPC producing Klebsiella Pneumoniae isolates

The FDA announced a boxed warning for tigecycline due to progression of infections caused by Gram-negative bacteria and increased risk of mortality during treatment. Plasma exposure of tigecycline might not prevent bacteraemia in these cases from the focuses. Hence, we evaluated intensified dosing regimens and breakpoints that might suppress bloodstream infections, caused by progression of infection by e.g., Gram-negatives. A pharmacometric model was built from tigecycline concentrations (100-600 mg daily doses) against clinical Klebsiella pneumoniae isolates (MIC 0.125-0.5 mg/L). Regrowth occurred at clinically used doses and stasis was only achieved with 100 mg q8h for the strain with the lowest studied MIC of 0.125 mg/L. Stasis at 24 h was related to fAUC/MIC of 38.5. Our study indicates that even intensified dosing regimens might prevent bloodstream infections only for MIC values ≤0.125 mg/L for tigecycline. This indicates an overly optimistic breakpoint of 1 mg/L for Enterobacterales, which are deemed to respond to the tigecycline high dose regimen (EUCAST Guidance Document on Tigecycline Dosing 2022).

Single-cell microfluidics enabled dynamic evaluation of drug combinations on antibiotic resistance bacteria

The rapid spread of antibiotic resistance has become a significant threat to global health, yet the development of new antibiotics is outpaced by emerging new resistance. To treat multidrug-resistant bacteria and prolong the lifetime of existing antibiotics, a productive strategy is to use combinations of antibiotics and/or adjuvants. However, evaluating drug combinations is primarily based on end-point checkerboard measurements, which provide limited information to study the mechanism of action and the discrepancies in the clinical outcomes. Here, single-cell microfluidics is used for rapid evaluation of the efficacy and mode of action of antibiotic combinations within 3 h. Focusing on multidrug-resistant Acinetobacter baumannii, the combination between berberine hydrochloride (BBH, as an adjuvant) and carbapenems (meropenem, MEM) or β-lactam antibiotic is evaluated. Real-time tracking of individual cells to programmable delivered antibiotics reveals multiple phenotypes (i.e., susceptible, resistant, and persistent cells) with fidelity. Our study discovers that BBH facilitates the accumulation of antibiotics within cells, indicating synergistic effects (FICI = 0.5). For example, the combination of 256 mg/L BBH and 16 mg/L MEM has a similar killing effect (i.e., the inhibition rates >90%) as the MIC of MEM (64 mg/L). Importantly, the synergistic effect of a combination can diminish if the bacteria are pre-stressed with any single drug. Such information is vital for understanding the underlying mechanisms of combinational treatments. Overall, our platform provides a promising approach to evaluate the dynamic and heterogenous response of a bacterial population to antibiotics, which will facilitate new drug discovery and reduce emerging antibiotic resistance.

Safety and effectiveness of tigecycline combination therapy in renal transplant patients with infection due to carbapenem-resistant gram-negative bacteria

Background

Carbapenem-resistant gram-negative bacterial (CRGNB) infections are increasing among kidney transplant recipients, and effective therapeutic options are limited. This study aimed to investigate the efficacy and adverse events associated with combination therapy tigecycline in renal transplant patients with CRGNB infections.

Methods

This study retrospectively analyzed 40 Chinese patients with confirmed or suspected CRGNB infections who received tigecycline therapy. The patients' case features and clinical and microbiological data were analyzed.

Results

A total of 40 renal transplant recipients received tigecycline therapy for a median duration of 9 (range, 3-25) days. CRGNB isolates were obtained from the organ preservation solution of the donor kidney in 28 patients, with confirmed transmission in 4 patients. Infections were detected in the bloodstream, urinary tract, sputum, and wound. The most prevalent isolates were Klebsiella pneumoniae (75%, 30/40), Acinetobacter baumannii (15%, 6/40), and Escherichia coli (10%, 4/40). A clinical response was observed in 32 (80%) patients. The 28-day all-cause mortality rate was 7.5% (3/40), while the one-year all-cause mortality rate was 2.5% (1/40). While one patient died owing to severe pancreatitis, no serious adverse events related to tigecycline therapy were reported. However, multiple indices of liver function and pancreatitis precursors increased after treatment with tigecycline compared to before treatment.

Conclusion

Tigecycline therapy appears to be well tolerated in renal transplant recipients with multidrug-resistant bacterial infections. Nevertheless, attention should be paid to adverse reactions related to tigecycline therapy, especially gastrointestinal reactions, and the related laboratory tests should be closely monitored.

Clinical Experience with Off-Label Intrathecal Administration of Selected Antibiotics in Adults: An Overview with Pharmacometric Considerations

Drain-associated intracerebral infections are life-threatening emergencies. Their treatment is challenging due to the limited penetration of antibiotics to the site of infection, resulting in potentially inadequate exposure. The emergence of multidrug-resistant pathogens might force the use of off-label intrathecal (IT) doses of antibiotics. We reviewed the literature on general aspects determining intrathecal dosing regimen, using pharmacometric knowledge. We summarised clinical experience with IT doses of antibiotics that are usually not used intrathecally, as well as the outcome of the cases and concentrations reached in the cerebrospinal fluid (CSF). Factors determining the IT regimen are the size of the ventricle system and the CSF drainage volume. With regard to pharmacometrics, pharmacokinetic/pharmacodynamic indices are likely similar to those in non-cerebral infections. The following number (N) of cases were described: benzylpenicillin (>50), ampicillin (1), ceftazidime (2), cephaloridine (56), ceftriaxone (1), cefotiam (1), meropenem (57), linezolid (1), tigecycline (15), rifampicin (3), levofloxacin (2), chloramphenicol (3) and daptomycin (8). Many side effects were reported for benzylpenicillin in the 1940-50s, but for the other antibiotics, when administered correctly, all side effects were minor and reversible. These data might help when choosing an IT dosing regimen in case there is no alternative option due to antimicrobial resistance.

Population pharmacokinetics of tigecycline in critically ill patients

Objective: In critically ill patients, the change of pathophysiological status may affect the pharmacokinetic (PK) process of drugs. The purpose of this study was to develop a PK model for tigecycline in critically ill patients, identify the factors influencing the PK and optimiz dosing regimens.

Method: The concentration of tigecycline was measured LC-MS/MS. We established population PK model with the non-linear mixed effect model and optimized the dosing regimens by Monte Carlo simulation.

Result: A total of 143 blood samples from 54 patients were adequately described by a one-compartment linear model with first-order elimination. In the covariate screening analysis, the APACHEII score and age as significant covariates. The population-typical values of CL and Vd in the final model were 11.30 ± 3.54 L/h and 105.00 ± 4.47 L, respectively. The PTA value of the standard dose regimen (100 mg loading dose followed by a 50 mg maintenance dose at q12 h) was 40.96% with an MIC of 2 mg/L in patients with HAP, the ideal effect can be achieved by increasing the dosage. No dose adjustment was needed for Klebsiella pneumoniae for AUC0–24/MIC targets of 4.5 and 6.96, and the three dose regimens almost all reached 90%. A target AUC0–24/MIC of ≥17.9 reached 100% in patients with cSSSI in the three tigecycline dose regimens, considering MIC ≤ 0.25 mg/L.

Conclusion: The final model indicated that APACHEII score and age could affect the Cl and Vd of tigecycline, respectively. The standard dose regimen of tigecycline was often not able to obtain satisfactory therapeutic effects for critically ill patients. For patients with HAP and cIAI caused by one of three pathogens, the efficacy rate can be improved by increasing the dose, but for cSSSI infections caused by Acinetobacter baumannii and K. pneumoniae, it is recommended to change the drug or use a combination of drugs.

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 high-dose tigecycline, by Monte Carlo simulation, in plasma and sputum of patients with hospital-acquired pneumonia

WHAT IS KNOWN AND OBJECTIVE

To Investigate the pharmacokinetic/pharmacodynamic (PK/PD) parameters of high-dose tigecycline in plasma and sputum of patients with hospital-acquired pneumonia (HAP), and provide a therapeutic regimen of multidrug-resistant bacteria (MDRB) infections.

METHODS

Blood/sputum samples were collected at intervals after tigecycline had reached a steady-state. Tigecycline concentrations in specimens were determined by high-performance liquid chromatography (HLPC), PK parameters were evaluated by WinNonlin software using a non-compartment model. The probability of target attainments (PTAs) at different minimal inhibitory concentrations (MICs) were calculated for achieving the PK/PD index with Crystal Ball software by 10,000-patient Monte Carlo Simulation.

RESULTS

In plasma, the maximum concentration (C_max ) and area under the concentration-time curve from 0 to 12 h (AUC_0-12h ) were 2.21 ± 0.17 mg/L and 15.29 ± 1.13 h mg/L, respectively. In sputum, they were 2.48 ± 0.21 mg/L and 19.46 ± 1.82 h mg/L, respectively. The mean lung penetration rate was 127.27%. At the MIC ≤4 mg/L, the PTAs in plasma and sputum were 100.00%. When the MIC increased to 8 mg/L, the PTAs in plasma and sputum mostly were < 90.00% according to two criteria.

WHAT IS NEW AND CONCLUSION

In this study, we explored PK/PD of high-dose tigecycline in plasma and sputum. From a PK/PD perspective, high-dose tigecycline had greater therapeutic outcomes in HAP treatment caused by MDRB. Antimicrobial-drug concentrations should be determined to optimize their clinical use.

Microbiological characteristics and risk factors on prognosis associated with Acinetobacter baumannii bacteremia in general hospital: A single-center retrospective study

OBJECTIVE

Acinetobacter baumannii is one of the most important pathogenic bacteria causing nosocomial infections and has a high mortality rate. Assessment of the microbiological characteristics and risk factors on prognosis associated with A.baumannii is essential. In this study, we aimed to investigate the clinical characteristics and prognostic risk factors of patients with A.baumannii bacteremia.

PATIENTS AND METHODS

This study retrospectively analyzed the antibiotic resistance of pathogens based on the clinical data of A.baumannii bacteremia patients presented in a tertiary teaching hospital from 2017 to 2022. Logistic regression and decision tree identified the prognostic risk factors for patients with baumannemia. Kaplan-Meier method was used for survival analysis between MDR and Non-MDR groups. The area under receiver-operating characteristic curve (ROC curve) was used to compare the predictive value of the APACHE II score and Sequential Organ Failure Assessment (SOFA) score.

RESULTS

A total of 110 patients with positive A. Baumannii blood cultures were included. Most of the patients were from intensive care unit (ICU) wards. The drug sensitivity results showed that the resistance rate of A. baumannii to colistin was the lowest (1.1%), followed by tigecycline (3.6%).The survival time of MDR group was significantly shorter than that of Non-MDR group. Multivariate analysis showed that, APACHE II score and SOFA score were independent risk factors affecting the prognosis of 28 days of A.baumannii bacteremia. And both scores displayed excellent AUROCs (SOFA: 0.909, APACHE II: 0.895 in predicting 28-day mortality). The two scoring systems were highly correlated and predicted no significant difference (r 2 = 0.4410, P < 0.001). We found that SOFA > 7 and APACHE II > 21 are associated with significantly higher mortality rates.

CONCLUSION

A.baumannii bacteremia have the highest incidence in the ICU, with high drug resistance and mortality rates. The survival time of patients with MDR A. Baumannii bacteremia was significantly shortened. The SOFA score and APACHE II score can reflect the severity of A.baumannii bacteremia patients and evaluate the 28-day prognosis. In addition, for the convenience of calculation, the SOFA score may be more clinically useful than the APACHE II score in predicting the mortality rate of A.baumannii bacteremia.

Influence of Antibiotics on Functionality and Viability of Liver Cells In Vitro

(1) Antibiotics are an important weapon in the fight against serious bacterial infections and are considered a common cause of drug-induced liver injury (DILI). The hepatotoxicity of many drugs, including antibiotics, is poorly analyzed in human in vitro models. (2) A standardized assay with a human hepatoma cell line was used to test the hepatotoxicity of various concentrations (Cmax, 5× Cmax, and 10× Cmax) of antibiotics. In an ICU, the most frequently prescribed antibiotics, ampicillin, cefepime, cefuroxime, levofloxacin, linezolid, meropenem, rifampicin, tigecycline, and vancomycin, were incubated with HepG2/C3A cells for 6 days. Cell viability (XTT assay, LDH release, and vitality), albumin synthesis, and cytochrome 1A2 activity were determined in cells. (3) In vitro, vancomycin, rifampicin, and tigecycline showed moderate hepatotoxic potential. The antibiotics ampicillin, cefepime, cefuroxime, levofloxacin, linezolid, and meropenem were associated with mild hepatotoxic reactions in test cells incubated with the testes Cmax concentration. Rifampicin and cefuroxime showed significantly negative effects on the viability of test cells. (4) Further in vitro studies and global pharmacovigilance reports should be conducted to reveal underlying mechanism of the hepatotoxic action of vancomycin, rifampicin, tigecycline, and cefuroxime, as well as the clinical relevance of these findings.

Clinical Efficacy, Antibiotic Resistance Genes, Virulence Factors and Outcome of Hospital-Acquired Pneumonia Induced by Klebsiella pneumoniae Carbapenemase 2-Producing with Tigecycline Treatment in the ICU

Purpose

Tigecycline is an agent for carbapenemase-producing Klebsiella pneumonia (KPC-KP), given its penetration into lung tissues. Our study focused on the molecular and clinical efficacy of tigecycline for hospital-acquired pneumonia (HAP) in the ICU.

Patients and Methods

A retrospective cohort study of 52 adult KPC-KP HAP patients by searching hospital medical records from January 2018 to December 2020 was established to investigate the epidemiology of KPC-KP infections for tigecycline treatment and the associated clinical efficacy of tigecycline. The KPC-KP isolates underwent multilocus sequence typing. Molecular typing, antimicrobial resistance, and virulence profiling were also analyzed by whole-genome sequencing of KPC-KP.

Results

Among 52 patients with KPC-KP, the ICU mortality rate was 14/52 (27%), and there was no significant statistical difference in mortality between the effective group and failure group (p = 0.754). However, the duration of tigecycline was statistically different between the two groups of patients (14.4 vs 10 days, p=0.046). The total bacterial clearance rate was 6/52 (11.5%). There was no significant statistical difference in both groups (p=0.416). Antibiotic resistance genes (aac3iia) and virulence gene (AREO-iutA, Capsule-wzc) were negatively correlated with clinical efficacy (p = 0.011, OR = 1.237).

Conclusions

Bla_kpc was the main carbapenemase in all K. pneumoniae strains. ST11-KL64 KPC-KP was the most common virulence factors in KPC-KP isolates. This study suggested that antibiotic resistance genes (aac3iia) and virulence gene (AREO-iutA, Capsule-wzc) were independent mortality risk factors for patients with Klebsiella pneumoniae carbapenemase-2 producing K. pneumoniae infections, when during the tigecycline treatment. Molecular analysis of K. pneumoniae may provide an option when choosing the antimicrobial treatment.

Successful Treatment of Postneurosurgical Ventriculitis Caused by Extensively Drug-resistant Acinetobacter baumannii in a Child: Case Report

Introduction: The incidence of postneurosurgical Acinetobacter baumannii ventriculitis/meningitis, primarily due to drug-resistant strains, has increased considerably in recent years. However, limited therapeutic options are available because most antibiotics poorly penetrate the blood-brain barrier, especially in pediatric patients. Case Presentation: A five-year-old boy developed ventriculitis due to extensively drug-resistant A. baumannii (XDRAB) after bilateral frontal external ventricular drainage for spontaneous intraventricular hemorrhage. The boy was safely and successfully treated with intraventricular (IVT)/intrathecal (ITH) polymyxin B together with intravenous tigecycline plus cefoperazone/sulbactam. Conclusions: In the present case, postneurosurgical XDRAB ventriculitis was closely associated with intraventricular hemorrhage and the placement of external ventricular drainage. IVT/ITH polymyxin B combined with intravenous tigecycline and cefoperazone sulbactam could be a therapeutic option against XDRAB ventriculitis in children.

Infectious Diseases Society of America Guidance on the Treatment of AmpC β-lactamase-Producing Enterobacterales, Carbapenem-Resistant Acinetobacter baumannii, and Stenotrophomonas maltophilia Infections

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. A previous guidance document focused on infections caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa). Here, guidance is provided for treating AmpC β-lactamase-producing Enterobacterales (AmpC-E), carbapenem-resistant Acinetobacter baumannii (CRAB), and Stenotrophomonas maltophilia infections.

METHODS

A panel of six infectious diseases specialists with expertise in managing antimicrobial-resistant infections formulated questions about the treatment of AmpC-E, CRAB, and S. maltophilia infections. Answers are presented as suggestions and corresponding rationales. In contrast to guidance in the previous document, published data on optimal treatment of AmpC-E, CRAB, and S. maltophilia infections are limited. As such, guidance in this document is provided as "suggested approaches" based on clinical experience, expert opinion, and a review of the available literature. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment suggestions are provided, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Suggestions apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of September 17, 2021 and will be updated annually. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance-2.0/.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Impact of Tigecycline's MIC in the Outcome of Critically Ill Patients with Carbapenemase-Producing Klebsiella pneumoniae Bacteraemia Treated with Tigecycline Monotherapy-Validation of 2019's EUCAST Proposed Breakpoint Changes

Background: Tigecycline is a therapeutic option for carbapenemase-producing Klebsiella pneumoniae (CP-Kp). Our aim was to evaluate the impact of the tigecycline’s minimum inhibitory concentration (MIC) in the outcome of patients with CP-Kp bacteraemia treated with tigecycline monotherapy. Methods: Patients with monomicrobial bacteraemia due to CP-Kp that received appropriate targeted monotherapy or no appropriate treatment were included. Primary outcome was 30-day mortality. MICs of meropenem, tigecycline, and ceftazidime/avibactam were determined by Etest, whereas for colistin, the broth microdilution method was applied. PCR for bla_KPC, bla_VIM, bla_NDM, and bla_OXA genes was applied. Results: Among 302 CP-Kp bacteraemias, 32 isolates (10.6%) showed MICs of tigecycline ≤ 0.5 mg/L, whereas 177 (58.6%) showed MICs that were 0.75–2 mg/L. Colistin and aminoglycoside susceptibility was observed in 43.0% and 23.8% of isolates, respectively. The majority of isolates carried bla_KPC (249; 82.5%), followed by bla_VIM (26; 8.6%), both bla_KPC and bla_VIM (16; 5.3%), and bla_NDM (11; 3.6%). Fifteen patients with tigecycline MIC ≤ 0.5 mg/L and 55 with MIC 0.75–2 mg/L were treated with tigecycline monotherapy; 30-day mortality was 20.0% and 50.9%, respectively (p = 0.042). Mortality of 150 patients that received other antimicrobials was 24.7%; among 82 patients that received no appropriate treatment, mortality was 39.0%. No difference in 30-day mortality was observed between patients that received tigecycline (MIC ≤ 0.5 mg/L) or other antimicrobials. Conclusion: Tigecycline monotherapy was as efficacious as other antimicrobials in the treatment of bloodstream infections due to CP-Kp isolates with a tigecycline’s MIC ≤ 0.5 mg/L.

Hypofibrinogenemia induced by high-dose tigecycline-case report and review of literature

RATIONALE

Extensive off-label use may affect the safety profile of tigecycline. Tigecycline-associated hypofibrinogenemia is potentially life threatening, although the frequency of life-threatening reactions is unknown and their incidence is easily overlooked. We report a case of 2 instances of treatment with high-dose tigecycline, each of which presented with hypofibrinogenemia.

PATIENT CONCERNS

An 86-year-old male patient was treated twice with high-dose tigecycline and presented with hypofibrinogenemia both times. The decrease in fibrinogen occurred within 3 to 7 days of tigecycline treatment. Other coagulation parameters had slightly prolonged values.

DIAGNOSES

Coagulopathy and hypofibrinogenemia.

INTERVENTIONS

We discontinued the tigecycline.

OUTCOMES

The fibrinogen level normalized within 5 days after the withdrawal of tigecycline. Following 80 days of hospitalization, the patient was transferred to the rehabilitation hospital for further treatment.

LESSONS

We suggest routine strict monitoring of coagulation parameters, particularly fibrinogen. Attention should be paid to below-normal fibrinogen levels due to increased bleeding risk and severity of reaction at fibrinogen levels below 1 g/L.

Is it time to move away from polymyxins?: evidence and alternatives

Increasing burden of carbapenem resistance and resultant difficult-to-treat infections are of particular concern due to the lack of effective and safe treatment options. More recently, several new agents with activity against certain multidrug-resistant (MDR) and extensive drug-resistant (XDR) Gram-negative pathogens have been approved for clinical use. These include ceftazidime-avibactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, plazomicin, and cefiderocol. For the management of MBL infections, clinically used triple combination comprising ceftazidime-avibactam and aztreonam is hindered due to non-availability of antimicrobial susceptibility testing methods and lack of information on potential drug-drug interaction leading to PK changes impacting its safety and efficacy. Moreover, in several countries including Indian subcontinent and developing countries, these new agents are yet to be made available. Under these circumstances, polymyxins are the only last resort for the treatment of carbapenem-resistant infections. With the recent evidence of suboptimal PK/PD particularly in lung environment, limited efficacy and increased nephrotoxicity associated with polymyxin use, the Clinical and Laboratory Standards Institute (CLSI) has revised both colistin and polymyxin B breakpoints. Thus, polymyxins 'intermediate' breakpoint for Enterobacterales, P. aeruginosa, and Acinetobacter spp. are now set at ≤ 2 mg/L, implying limited clinical efficacy even for isolates with the MIC value 2 mg/L. This change has questioned the dependency on polymyxins in treating XDR infections. In this context, recently approved cefiderocol and phase 3 stage combination drug cefepime-zidebactam assume greater significance due to their potential to act as polymyxin-supplanting therapies.

Efficacy and safety of tigecycline in treatment of pneumonia caused by MDR Acinetobacter baumannii: a systematic review and meta-analysis

BACKGROUND

Use of tigecycline in treating MDR Acinetobacter baumannii (MDRAB) remains controversial.

OBJECTIVES

To comprehensively assess the safety and efficacy of tigecycline in pneumonia caused by Acinetobacter baumannii.

METHODS

PubMed, Embase, Web of Science and Cochrane library databases were searched up to 12 March 2019. Studies were included if they compared tigecycline-based regimens with other antibiotic regimens for treating AB pulmonary infections and we pooled the clinical outcomes, microbiological response, adverse events or mortality.

RESULTS

One prospective study and nine retrospective studies were included in this meta-analysis. The results showed similar clinical cure rates (OR = 1.04, 95% CI = 0.60-1.81; P = 0.89) and mortality rates (OR = 1.11, 95% CI = 0.65-1.89; P = 0.71) comparing tigecycline groups with the control groups. However, a significantly lower microbiological eradication rate was found in the tigecycline groups (OR = 0.43, 95% CI = 0.27-0.66; P = 0.0001). Incidence of nephrotoxicity in tigecycline-based regimens was significantly lower than in colistin-based regimens (OR = 0.34, 95% CI = 0.16-0.74, I2 = 35%, P = 0.006). There were no randomized controlled trials (RCTs) included; incomplete safety data and regional bias caused by the majority of the studies originating in China are the main limitations of this meta-analysis.

CONCLUSIONS

Tigecycline can be used for treating MDRAB pulmonary infections owing to efficacy similar to that of other antibiotics. Moreover, tigecycline did not show a higher risk of mortality. Considering the lower microbiological eradication rate for tigecycline, which is likely to induce antimicrobial resistance, well-designed RCTs for high-dose tigecycline in treating pneumonia caused by AB are still needed.

Optimization of tigecycline dosage regimen for different infections in the patients with hepatic or renal impairment

OBJECTIVE

The objective of this study was to investigate the cumulative fraction of response (CFR) of various tigecycline dosing regimens in patients with hepatic or renal impairment.

METHODS

Monte Carlo simulations were performed using pharmacokinetic parameters and microbiological data to evaluate various tigecycline regimens in patients with hepatic or renal impairment.

RESULTS

For HAP and cIAI, the regimen of 25 mg q12h achieved CFR values of >90% in Child-Pugh C patients against Gram-positive bacteria and partial Gram-negative bacteria (Escherichia coli and Klebsiella oxytoca). However, dose increases of tigecycline was mostly required for Enterobacter cloacae, Klebsiella pneumoniae and Acinetobacter baumanni. The conventional tigecycline regimen (50 mg q12h) was effective for HAP and cIAI caused by Gram-positive bacteria and Escherichia coli in patients with renal impairment. For HAP caused by Klebsiella pneumoniae and Enterobacter cloacae, patients with severe renal failure can use the standard dose regimen 50 mg q12h, and other patients need to increase the dose of tigecycline. However, when treating cSSSI caused by Acinetobacter baumannii, Enterobacter cloacae and Klebsiella pneumoniae, all tigecycline maintenance doses have a CFR <90%.

CONCLUSIONS

It is necessary to optimize tigecycline dosage regimens in patients with hepatic or renal impairment in order to maximise clinical response and minimise the probability of exposure-related toxicity.

Pharmacokinetics of high-dose tigecycline in critically ill patients with severe infections

Background

In critically ill patients, the use of high tigecycline dosages (HD TGC) (200 mg/day) has been recently increasing but few pharmacokinetic/pharmacodynamic (PK/PD) data are available. We designed a prospective observational study to describe the pharmacokinetic/pharmacodynamic (PK/PD) profile of HD TGC in a cohort of critically ill patients with severe infections.

Results

This was a single centre, prospective, observational study that was conducted in the 20-bed mixed ICU of a 1500-bed teaching hospital in Rome, Italy. In all patients admitted to the ICU between 2015 and 2018, who received TGC (200 mg loading dose, then 100 mg q12) for the treatment of documented infections, serial blood samples were collected to measure steady-state TGC concentrations. Moreover, epithelial lining fluid (ELF) concentrations were determined in patients with nosocomial pneumonia. Amongst the 32 non-obese patients included, 11 had a treatment failure, whilst the other 21 subjects successfully eradicated the infection. There were no between-group differences in terms of demographic aspects and main comorbidities. In nosocomial pneumonia, for a target AUC_0-24/MIC of 4.5, 75% of the patients would be successfully treated in presence of 0.5 mcg/mL MIC value and all the patients obtained the PK target with MIC ≤ 0.12 mcg/mL. In intra-abdominal infections (IAI), for a target AUC_0-24/MIC of 6.96, at least 50% of the patients would be adequately treated against bacteria with MIC ≤ 0.5 mcg/mL. Finally, in skin and soft-tissue infections (SSTI), for a target AUC_0-24/MIC of 17.9 only 25% of the patients obtained the PK target at MIC values of 0.5 mcg/mL and less than 10% were adequately treated against germs with MIC value ≥ 1 mcg/mL. HD TGC showed a relevant pulmonary penetration with a median and IQR ELF/plasma ratio (%) of 152.9 [73.5–386.8].

Conclusions

The use of HD TGC is associated with satisfactory plasmatic and pulmonary concentrations for the treatment of severe infections due to fully susceptible bacteria (MIC < 0.5 mcg/mL). Even higher dosages and combination strategies may be suggested in presence of difficult to treat pathogens, especially in case of SSTI and IAI.

Tigecycline-associated hypofibrinogenemia in a real-world setting

Background Tigecycline is a broad-spectrum antibiotic used to treat infections that do not respond to first-line treatments. High-doses and extended treatments are common; therefore, adverse events might be more frequent and severe than those observed in clinical trials. Several case-reports have referred hypofibrinogenemia in patients who received tigecycline. Objective To analyse the impact of tigecycline use on coagulation parameters, and identify which variables could be related with this. Setting The study was performed at Hospital Universitari Vall Hebron, in Barcelona, Spain. Method Observational, retrospective study. All patients older than 18, who received tigecycline for > 72 h from January 2016 to March 2018 were included. Clinical and laboratory data from before, during and at the end of tigecycline treatment were retrospectively collected. Differences between means were analyzed using the paired-sample Student's t-test. Binary logistic regression was performed to identify risk factors for hypofibrinogenemia. Main outcome measure Mean difference in fibrinogen plasma concentration and INR, before and at the end of tigecycline treatment. Results 78 patients (mean age 65; SD ± 15.5 years) were identified. The most common indications for tigecycline treatment were abdominal (66%), respiratory tract (16%) and skin&soft tissue (10%) infections. High-dose tigecycline was used in 62% of cases and the median duration of treatment was 12 days. Hypofibrinogenemia occurred in 12 patients, 5 bleeding events were observed and 4 of them required fibrinogen administration. Tigecycline caused significant alterations in fibrinogen plasma concentration (mean decrease 1.76 g/L; IC 95% 1.36 to 2.15) as well as INR (mean increase 0.11; IC 95% 0.05 to 0.17). Both were recovered after treatment cessation. We identified duration of treatment > 4 weeks (OR = 6.6), high-dose tigecycline (OR = 4.75) and high protein C levels (OR = 4.2) as independent variables associated with fibrinogen decrease, but not renal impairment. Conclusions Tigecycline administration has been related with hypofibrinogenemia, especially when high-doses of tigecycline are used. Health professionals should be aware of the potentially severe tigecycline-associated hypofibrinogenemia and monitor coagulation during treatment, especially when high-doses of tigecycline are used.

High-Dose Tigecycline in Elderly Patients with Pneumonia Due to Multidrug-Resistant Acinetobacter baumannii in Intensive Care Unit

Purpose

The association between clinical and microbiological outcomes and high-dose tigecycline (TGC) was assessed in elderly (≥60 years old) patients with hospital-acquired and ventilator-associated pneumonia due to multidrug-resistant Acinetobacterbaumannii(A. baumannii). This study also assessed tigecycline combination with different antibiotics and its influence on the outcome.

Patients and Methods

An observational retrospective cohort study was conducted. Patients over 60 years old were treated with standard-dose (SD) TGC (100-mg intravenous TGC initially, followed by 50-mg doses administered intravenously twice daily) and high-dose (HD) TGC (200-mg intravenous TGC initially, followed by 100-mg doses administered intravenously twice daily) for a microbially confirmed infection. The outcome was 30-day crude mortality, co-administered antimicrobial agent and the microbial eradication percentage in both groups.

Results

A total of 48 multidrug-resistant A. baumannii respiratory patients were identified. Tigecycline was administered to 85% of ventilation-associated pneumonia (VAP) patients (28/33) in the SD group and 80% of VAP patients (12/15) in the HD group. Combined therapy was the major treatment option in both groups, accounting for 85% and 87%, respectively. Median treatment duration in both groups was 7.36 vs 8.6 days, respectively. Survival days were 13.61 vs 12.4 days (P=0.357), respectively. The 30-day crude mortality was 39.4% (13/33) for the SD group and 14% (2/15) for the HD group (P=0.098). The microbial eradication rate of respiratory specimens in the SD group was higher than that in the HD group (P=0.02). The variables associated with 30-day crude mortality were chronic obstructive pulmonary disease (hazard ratio [HR] 11.63, 95% CI 1.094–123.058; P=0.042), tigecycline treatment duration (HR 0.690, 95% CI 0.515–0.926; P=0.013), and surgery before infection (HR 79.276, 95% CI 6.983–899.979; P=0.000). High-dose tigecycline was not associated with 30-day crude mortality (adjusted HR 0.329, 95% CI 0.074–1.460; P=0.145). Combined antibiotics was also not different between the two groups.

Conclusions

High-dose tigecycline was not associated with 30-day crude mortality in elderly patients with pneumonia due to multidrug-resistant A. baumannii, although the microbial eradication rate was high.

Clinical characteristics and risk factors of tigecycline-associated hypofibrinogenaemia in critically ill patients

Purpose

To analyze the clinical features and risk factors of tigecycline-associated hypofibrinogenaemia and study whether cefoperazone/sulbactam combined with tigecycline aggravates coagulopathy or hypofibrinogenaemia.

Methods

A retrospective case–control study of patients with severe infection who were treated with tigecycline was conducted. Patients were assigned to the hypofibrinogenaemia group (< 2.0 g/L) and normal fibrinogen (normal) group (≥ 2.0 g/L) to assess the clinical features of patients with tigecycline-associated hypofibrinogenaemia. The traits of patients treated with cefoperazone/sulbactam in the hypofibrinogenaemia group were also analyzed.

Results

In total, 127 patients were enrolled in the study, including 71 patients with hypofibrinogenaemia and 56 patients with normal fibrinogen levels. Hypofibrinogenaemia developed at a median of 6 (4–8) days after tigecycline treatment, and the fibrinogen level returned to normal at a median of 3 (3–5) days after tigecycline discontinuation. In the multivariate analysis, intra-abdominal infection (p = 0.005), fibrinogen level at tigecycline initiation (p < 0.001), maintenance dose (p = 0.039), and treatment duration (p = 0.002) were found to be related to hypofibrinogenaemia. Treatment with cefoperazone/sulbactam was not associated with hypofibrinogenaemia (p = 0.681), but patients treated with cefoperazone/sulbactam had a higher incidence of coagulopathy (p = 0.009) and needed more blood products (p = 0.003) than those treated without cefoperazone/sulbactam.

Conclusion

Tigecycline-associated hypofibrinogenaemia often developed on the 6th (4th–8th) day of tigecycline use and was associated with intra-abdominal infection, fibrinogen level at tigecycline initiation, maintenance dose, and treatment duration of tigecycline but not cefoperazone/sulbactam.

Intrathecal Antibacterial and Antifungal Therapies

Intrathecal administration of anti-infectives is indicated in central nervous system infections by multiresistant pathogens when drugs that can reach adequate cerebrospinal fluid (CSF) concentrations by systemic therapy are not available. Antibiotics that readily pass the blood-brain and blood-CSF barriers and/or that have low toxicity allowing an increase in the daily dosage should not be used for intrathecal therapy. Intrathecal therapy is accompanied by systemic treatment. Antibacterials indispensable for intrathecal therapy include aminoglycosides, colistin, daptomycin, tigecycline, and vancomycin. Limited experience suggests the utility of the antifungals amphotericin B and caspofungin. Intraventricular administration ensures distribution throughout the CSF compartment, whereas intralumbar dosing often fails to attain adequate antibiotic concentrations in the ventricles. The individual dose is determined by the estimated size of the CSF space and by the estimated clearance from CSF. For moderately lipophilic anti-infectives with a molecular weight above approximately 1,000 g/mol, as well as for hydrophilic drugs with a molecular weight above approximately 400 g/mol, one daily dose is normally adequate. The ventricular drain should be clamped for 15 to 120 min to facilitate the distribution of the anti-infective in the CSF space. Therapeutic drug monitoring of the trough levels is necessary only in cases of therapeutic failure.

Successful High-Dosage Monotherapy of Tigecycline in a Multidrug-Resistant Klebsiella pneumoniae Pneumonia-Septicemia Model in Rats

Background: Recent scientific reports on the use of high dose tigecycline monotherapy as a “drug of last resort” warrant further research into the use of this regimen for the treatment of severe multidrug-resistant, Gram-negative bacterial infections. In the current study, the therapeutic efficacy of tigecycline monotherapy was investigated and compared to meropenem monotherapy in a newly developed rat model of fatal lobar pneumonia–septicemia. Methods: A Klebsiella pneumoniae producing extended-spectrum β-lactamase (ESBL) and an isogenic variant producing K. pneumoniae carbapenemase (KPC) were used in the study. Both strains were tested for their in vitro antibiotic susceptibility and used to induce pneumonia–septicemia in rats, which was characterized using disease progression parameters. Therapy with tigecycline or meropenem was initiated at the moment that rats suffered from progressive infection and was administered 12-hourly over 10 days. The pharmacokinetics of meropenem were determined in infected rats. Results: In rats with ESBL pneumonia–septicemia, the minimum dosage of meropenem achieving survival of all rats was 25 mg/kg/day. However, in rats with KPC pneumonia–septicemia, this meropenem dosage was unsuccessful. In contrast, all rats with KPC pneumonia–septicemia were successfully cured by administration of high-dose tigecycline monotherapy of 25 mg/kg/day (i.e., the minimum tigecycline dosage achieving 100% survival of rats with ESBL pneumonia–septicemia in a previous study). Conclusions: The current study supports recent literature recommending high-dose tigecycline as a last resort regimen for the treatment of severe multidrug-resistant bacterial infections. The use of ESBL- and KPC-producing K. pneumoniae strains in the current rat model of pneumonia–septicemia enables further investigation, helping provide supporting data for follow-up clinical trials in patients suffering from severe multidrug-resistant bacterial respiratory infections.

Effectiveness and Safety of High Dose Tigecycline for the Treatment of Severe Infections: A Systematic Review and Meta-Analysis

BACKGROUND

Studies assessing the effect of high dose tigecycline on severe infections are limited and remain controversial.

OBJECTIVES

To assess systematically the effectiveness and safety of high dose tigecycline in the treatment of severe infections.

METHODS

Pubmed, Web of Science, Embase, MEDLINE, Cochrane Library and ClinicalTrials were searched up to February 20, 2019 for studies that compared the effectiveness and safety of high dose tigecycline with standard dose tigecycline or other non-tigecycline-containing regimens in the treatment of severe infections. Rates for all-cause mortality, clinical cure, microbiological eradication and adverse events were analysed.

RESULTS

Ten studies with 593 patients were included. The results indicated that using high dose tigecycline resulted in better outcomes compared with controls with lower all-cause mortality (OR 0.44, 95% CI 0.30-0.66, p < 0.0001), higher clinical cure (OR 3.43, 95% CI 2.09-5.63, p < 0.00001), higher microbiological eradication (OR 2.25, 95% CI 1.44-3.50, p = 0.0003), and without increasing adverse events rates. Subgroup analysis showed that high dose tigecycline reduced all-cause mortality in nosocomial acquired pneumonia (OR 0.39, 95% CI 0.22-0.70, p = 0.002), bloodstream infections (OR 0.19, 95% CI 0.06-0.58, p = 0.004) and mixed infections (OR 0.20, 95% CI 0.07-0.59, p = 0.003), with no statistical differences in complicated intra-abdominal infections (OR 2.04, 95% CI 0.80-5.23, p = 0.14). In carbapenem-resistant pathogens, the microbiological eradication rate in those given high dose tigecycline did not differ from controls (OR 1.07, 95% CI 0.44-2.60, p = 0.87), although mortality was reduced (OR 0.20, 95% CI 0.09-0.45, p = 0.0001). The main limitation of the review is that most of the included studies are observational studies with small sample sizes and high risks of bias.

CONCLUSIONS

High dose tigecycline treatment is effective and safe for severe infections owing to its lower all-cause mortality, higher clinical cure, microbiological eradication and comparable adverse events. However, as a result of the high risks of bias of the included studies, well-designed randomised clinical trials are warranted to establish the effectiveness and safety of high dose tigecycline compared with standard dose tigecycline and other commonly used antibiotics.

Treatment of Carbapenem-Resistant Enterobacteriaceae Infections in Children

Infections due to carbapenem-resistant Enterobacteriaceae (CRE) are increasingly prevalent in children and are associated with poor clinical outcomes. Optimal treatment strategies for CRE infections continue to evolve. A lack of pediatric-specific comparative effectiveness data, uncertain pediatric dosing regimens for several agents, and a relative lack of new antibiotics with pediatric indications approved by the US Food and Drug Administration (FDA) collectively present unique challenges for children. In this review, we provide a framework for antibiotic treatment of CRE infections in children, highlighting relevant microbiologic considerations and summarizing available data related to the evaluation of FDA-approved antibiotics (as of September 2019) with CRE activity, including carbapenems, ceftazidime-avibactam, meropenem-vaborbactam, imipenem/cilastatin-relebactam, polymyxins, tigecycline, eravacycline, and plazomicin.

Colistin-sparing approaches with newer antimicrobials to treat carbapenem-resistant organisms: Current evidence and future prospects

Antimicrobial resistance is on the rise across the globe. Increasing incidence of infections due to carbapenem resistance organisms is becoming difficult to treat, due to the limited availability of therapeutic agents. Very few agents such as colistin, fosfomycin, tigecycline and minocycline are widely used, despite its toxicity. However, with the availability of novel antimicrobials, beta-lactam/beta-lactamase inhibitor-based and non-beta-lactam-based agents could be of great relief. This review covers three important aspects which include (i) current management of carbapenem-resistant infections, (ii) determination of specific types of carbapenemases produced by multidrug-resistant and extensively drug-resistant Gram-negative pathogens and (iii) the currently available novel beta-lactam/beta-lactamase inhibitors and non-beta-lactam-based agents' laboratory findings, clinical outcome and implications.

Multidrug Resistant Acinetobacter baumannii: Resistance by Any Other Name Would Still be Hard to Treat

PURPOSE OF REVIEW

Acinetobacter baumannii (AB) is an infamous nosocomial pathogen with a seemingly limitless capacity for antimicrobial resistance, leading to few treatment options and poor clinical outcomes. The debatably low pathogenicity and virulence of AB are juxtaposed by its exceptionally high rate of infection-related mortality, likely due to delays in time to effective antimicrobial therapy secondary to its predilection for resistance to first-line agents. Recent studies of AB and its infections have led to a burgeoning understanding of this critical microbial threat and provided clinicians with new ammunition for which to target this elusive pathogen. This review will provide an update on the virulence, resistance, diagnosis, and treatment of multidrug resistant (MDR) AB.

RECENT FINDINGS

Advances in bacterial genomics have led to a deeper understanding of the unique mechanisms of resistance often present in MDR AB and how they may be exploited by new antimicrobials or optimized combinations of existing agents. Further, improvements in rapid diagnostic tests (RDTs) and their more pervasive use in combination with antimicrobial stewardship interventions have allowed for more rapid diagnosis of AB and decreases in time to effective therapy. Unfortunately, there remains a paucity of high-quality clinical data for which to inform the optimal treatment of MDR AB infections. In fact, recently completed studies have failed to identify a combination regimen that is consistently superior to monotherapy, despite the benefits demonstrated in vitro. Encouragingly, new and updated guidelines offer strategies for the treatment of MDR AB and may help to harmonize the use of high toxicity agents such as the polymyxins. Finally, new antimicrobial agents such as eravacycline and cefiderocol have promising in vitro activity against MDR AB but their place in therapy for these infections remains to be determined. Notwithstanding available clinical trial data, polymyxin-based combination therapies with either a carbapenem, minocycline, or eravacycline remain the treatment of choice for MDR, particularly carbapenem-resistant, AB. Incorporating antimicrobial stewardship intervention with RDTs relevant to MDR AB can help avoid potentially toxic combination therapies and catalyze the most important modifiable risk factor for mortality-time to effective therapy. Further research efforts into pharmacokinetic/pharmacodynamic-based dose optimization and clinical outcomes data for MDR AB continue to be desperately needed.

Treatment Options for Carbapenem-resistant Gram-negative Bacterial Infections

Antimicrobial resistance has become one of the greatest threats to public health, with rising resistance to carbapenems being a particular concern due to the lack of effective and safe alternative treatment options. Carbapenem-resistant gram-negative bacteria of clinical relevance include the Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii, and more recently, Stenotrophomonas maltophilia. Colistin and tigecycline have been used as first-line agents for the treatment of infections caused by these pathogens; however, there are uncertainties regarding their efficacy even when used in combination with other agents. More recently, several new agents with activity against certain carbapenem-resistant pathogens have been approved for clinical use or are reaching late-stage clinical development. They include ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, plazomicin, eravacycline, and cefiderocol. In addition, fosfomycin has been redeveloped in a new intravenous formulation. Data regarding the clinical efficacy of these new agents specific to infections caused by carbapenem-resistant pathogens are slowly emerging and appear to generally favor newer agents over previous best available therapy. As more treatment options become widely available for carbapenem-resistant gram-negative infections, the role of antimicrobial stewardship will become crucial in ensuring appropriate and rationale use of these new agents.

Optimizing therapy in carbapenem-resistant Enterobacteriaceae infections

PURPOSE OF REVIEW

In the absence of randomized clinical trial data, questions remain regarding the optimal treatment of carbapenem-resistant Enterobacteriaceae (CRE) infections. CRE have historically been susceptible to polymyxins, tigecycline or aminoglycosides (mostly gentamicin), and these antibiotics have long been considered the drugs of choice for CRE infections, although varying rates of resistance to all have been reported. This review looks at data from clinical studies assessing the outcomes of CRE infections treated with different antibiotic regimens.

RECENT FINDINGS

The recently approved fixed-dose combination agent, ceftazidime-avibactam (CAZ-AVI), is active against KPC and OXA-48-producing Enterobacteriaceae. The limited clinical data available on CAZ-AVI indicate that it is associated with survival benefits relative to other commonly used regimens, although development of resistance is a concern. New drugs active against CRE isolates (including the recently approved meropenem-vaborbactam) are in different stages of development.

SUMMARY

CAZ-AVI and meropenem-vaborbactam seem destined to become the backbone of target therapy for high-risk patients with severe infections caused by susceptible CRE strains. However, empirical therapy should be based on risk factors to be defined in the near future, whereas the necessity of combinations with CAZ-AVI requires further studies. Polymyxins are still important options for low-risk patients with susceptible CRE infections, but also for high-risk patients in regions where metallo-β-lactamase-producing CRE predominate because CAZ-AVI and meropenem-vaborbactam are both ineffective against these strains.

Spontaneous Knee Hemarthrosis Due to Hypofibrinogenemia Following Tigecycline Treatment for Periprosthetic Joint Infection

Tigecycline, a recently approved antibiotic, has a broad spectrum of antimicrobial activity. Its unique structure and properties make tigecycline a valuable option for the treatment of infections caused by many multidrug-resistant organisms. We present a case of an 82-year-old patient who developed a significant decrease of fibrinogen levels after the addition of tigecycline to his antibiotic regimen. The patient was treated for a periprosthetic knee joint infection caused by a multidrug-resistant extended-spectrum beta-lactamase-producing Escherichia coli. The reduction of fibrinogen levels, in this case, prompted severe spontaneous hemarthrosis. Tigecycline treatment was discontinued and coagulation disorders were normalized within the next few days. After several days, the joint had to be surgically debrided. Hypofibrinogenemia is a very scarcely reported side effect of tigecycline that can cause spontaneous hemarthrosis.

Carbapenemases in Enterobacteriaceae: Detection and Antimicrobial Therapy

Carbapenem-resistant Enterobacteriaceae (CRE) have spread rapidly around the world in the past few years, posing great challenges to human health. The plasmid-mediated horizontal transmission of carbapenem-resistance genes is the main cause of the surge in the prevalence of CRE. Therefore, the timely and accurate detection of CRE, especially carbapenemase-producing Enterobacteriaceae, is very important for the clinical prevention and treatment of these infections. A variety of methods for the rapid detection of CRE phenotypes and genotypes have been developed for use in clinical microbiology laboratories. To overcome the lack of efficient antibiotics, CRE infections are often treated with combination therapies. Moreover, novel drugs and emerging strategies appeared successively and in various stages of development. In this article, we summarized the global distribution of various carbapenemases. And we focused on summarizing and comparing the advantages and limitations of the detection methods and the therapeutic strategies of CRE primarily.

Comparative serum bactericidal activity of meropenem-based combination regimens against extended-spectrum beta-lactamase and KPC-producing Klebsiella pneumoniae

Combination therapies are frequently used in the treatment of multidrug-resistant Klebsiella pneumoniae infection without consensus regarding which combination is the most effective. We compared bactericidal titres from sera collected from critically ill patients receiving meropenem plus tigecycline (n = 5), meropenem plus colistin (n = 5), or meropenem, colistin and tigecycline (n = 5) against K. pneumoniae isolates that included ESBL-producing (n = 7) and KPC-producing strains (n = 14) with varying sensitivity patterns to colistin and tigecycline. Meropenem concentrations (C_min) were measured in all samples by LC-MS/MS, and indexed to respective pathogen MICs to explore differences in patterns of bactericidal activity for two versus three drug combination regimens. All combination regimens achieved higher SBTs against ESBL (median reciprocal titre 128, IQR 32-256) versus KPC (4, IQR 2-32) strains. Sera from patients treated with meropenem-colistin yielded higher median SBTs (256, IQR 64-512) than either meropenem-tigecycline (32, IQR 8-256; P < 0.001). The addition of tigecycline was associated with a lower probability of achieving a reciprocal SBT above 8 when meropenem concentrations were below the MIC (P = 0.04). Although the clinical significance is unknown, sera from patients receiving tigecycline-based combination regimens produce lower serum bactericidal titres against ESBL or KPC-producing K. pneumoniae. SBTs may represent a useful complimentary endpoint for comparing pharmacodynamics of combinations regimens for MDR Enterobacteriaceae.

The "Old" and the "New" Antibiotics for MDR Gram-Negative Pathogens: For Whom, When, and How

The recent expansion of multidrug resistant and pan-drug-resistant pathogens poses significant challenges in the treatment of healthcare associated infections. An important advancement, is a handful of recently launched new antibiotics targeting some of the current most problematic Gram-negative pathogens, namely carbapenem-producing Enterobacteriaceae (CRE) and carbapenem-resistant P. aeruginosa (CRPA). Less options are available against carbapenem-resistant Acinetobacter baumannii (CRAB) and strains producing metallo-beta lactamases (MBL). Ceftazidime-avibactam signaled a turning point in the treatment of KPC and partly OXA- type carbapenemases, whereas meropenem-vaborbactam was added as a potent combination against KPC-producers. Ceftolozane-tazobactam could be seen as an ideal beta-lactam backbone for the treatment of CRPA. Plazomicin, an aminoglycoside with better pharmacokinetics and less toxicity compared to other class members, will cover important proportions of multi-drug resistant pathogens. Eravacycline holds promise in the treatment of infections by CRAB, with a broad spectrum of activity similar to tigecycline, and improved pharmacokinetics. Novel drugs and combinations are not to be considered "panacea" for the ongoing crisis in the therapy of XDR Gram-negative bacteria and colistin will continue to be considered as a fundamental companion drug for the treatment of carbapenem-resistant Enterobacteriaceae (particularly in areas where MBL predominate), for the treatment of CRPA (in many cases being the only in vitro active drug) as well as CRAB. Aminoglycosides are still important companion antibiotics. Finally, fosfomycin as part of combination treatment for CRE infections and P. aeruginosa, deserves a greater attention. Optimal conditions for monotherapy and the "when and how" of combination treatments integrating the novel agents will be discussed.

Evaluation of treatment options for methicillin-resistant Staphylococcus aureus infections in the obese patient

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a major cause of infection in both the hospital and community setting. Obesity is a risk factor for infection, and the prevalence of this disease has reached epidemic proportions worldwide. Treatment of infections in this special population is a challenge given the lack of data on the optimal antibiotic choice and dosing strategies, particularly for treatment of MRSA infections. Obesity is associated with various physiological changes that may lead to altered pharmacokinetic parameters. These changes include altered drug biodistribution, elimination, and absorption. This review provides clinicians with a summary of the literature pertaining to the pharmacokinetic and pharmacodynamic considerations when selecting antibiotic therapy for the treatment of MRSA infections in obese patients.

Extensively drug-resistant Gram-negative bacterial bloodstream infection in hematological disease

Background

Extensively drug-resistant Gram-negative bacterial (XDR-GNB) bloodstream infection (BSI) is difficult to treat and is associated with a high mortality rate in patients with hematological diseases. The aim of this study is to investigate the predisposing risk factors and the efficacy of the antibiotic treatment in these patients, including exploration of efficacy and adverse effects of high-dose tigecycline.

Methods

Between January 2013 and December 2017, 27 XDR-GNB BSI patients with hematological diseases were diagnosed and retrospectively reviewed in the current study.

Results

Clinical response in patients with severe complications (such as severe neutropenia >10 days, grade III–IV acute graft-versus-host disease (aGVHD), and concurrent pneumonia) was significantly lower than in patients without or with only mild complications (P=0.033). The efficacy rate was 62.5% (10/16) in patients with tigecycline-based combination therapy regimen, 77.8% (7/9) with a high-dose tigecycline regimen, and 42.9% (3/7) with a standard-dose tigecycline regimen (P=0.36). The 30-day survival rates of patients undergoing high-dose or standard-dose tigecycline treatment were 66.7% (95% CI: 28.2–87.8) and 57.1% (95% CI: 17.2–83.7), respectively, (P=0.603). Patients with mild complications were associated with superior 30-day survival rates than patients with severe complications (93.8% vs 36.4%, P=0.001), >10 days of neutropenia (90.9% vs 33.3%, P=0.012), severe aGVHD (100% vs 40%, P=0.049), and concurrent pneumonia (84.6% vs 57.1%, P=0.048).

Conclusion

Our study indicated that XDR-GNB BSI in patients of hematological diseases with severe complications, such as long duration of neutropenia (>10 days) and severe aGVHD were associated with poor clinical response and short survival. We first indicated that these patients undergoing high-dose tigecycline treatment had an improved clinical response and an increased 30-day survival rate compared with the standard-dose group, although the differences were not statistically significant. This might be due to more severe complicated patients enrolled in high-dose group and the limited number size in our study.

Adverse events of high-dose tigecycline in the treatment of ventilator-associated pneumonia due to multidrug-resistant pathogens

The off-label uses of tigecycline (TGC) to treat ventilator-associated pneumonia (VAP) have aroused worldwide concerns. The efficacy about TGC has been recently reported. However, the adverse events (AEs) remain controversial. Our study aims to analyze the safety of the high-dose (HD) regimens in the treatment of VAP due to multidrug-resistant (MDR) pathogens.The clinical data of 134 patients who were diagnosed with VAP from January 2013 to December 2015 in the NeuroScience Care Unit (NCU) were analyzed retrospectively. The incidence and the occurrence time of AEs, 28-day mortality, and the factors of clinical effectiveness were explored.A total of 54 patients received the standard dose group (SD), 69 in the HD, and 11 in the nonstandard HD group (NHD). Acinetobacter baumannii were the main pathogenic bacteria. There was no statistic difference in the incidence of AEs and the 28-day mortality among the 3 groups (P > .05). Total bilirubin (TBIL) increased significantly after SD of TGC treatment (P = .004). Liver dysfunction occurred the latest (10.83 ± 7.08), not in the duration of HD group (9.63 ± 3.92), whereas in the SD group (13.00 ± 7.57) and NHD group (12.64 ± 3.70). Patients with septic shock, MODS, and higher APACHE II score were of high risk in mortality. The HD group was associated with higher clinical effective rate and bacteria clearance rate.HD TGC was relatively safe and tolerable in ICU patients. The risk of side effects was related to the TGC duration, although not increased as the dosage rose. Full course of the HD regimen was associated with better outcomes for the treatment of VAP patients, especially for the MDR gram-negative bacilli infection. Inappropriate antimicrobial treatment might lead to clinical treatment failure.

A retrospective, comparative analysis of risk factors and outcomes in carbapenem-susceptible and carbapenem-nonsusceptible Klebsiella pneumoniae bloodstream infections: tigecycline significantly increases the mortality

Background

Carbapenem-nonsusceptible Klebsiella pneumoniae (CnSKP) is rapidly emerging as a life-threatening nosocomial infection. The efficacy of tigecycline in the treatment of bloodstream infections (BSIs) remains controversial.

Methods

Data from a total of 428 patients with carbapenem-susceptible Klebsiella pneumoniae (CSKP) and CnSKP BSIs were collected at a single center between January 2013 and December 2015. A three-part analysis was conducted to identify the risk factors associated with CnSKP, explore prognosis, and evaluate treatments.

Results

Data from 428 patients with Klebsiella pneumoniae (KP) BSIs were included, 31.5% (n=135) of them with CnSKP. Multivariate analysis showed that prior hospitalization, urinary catheterization, the use of immunosuppressive agents, prior use of antibiotics, pulmonary disease, and high Acute Physiology and Chronic Health Evaluation (APACHE) II scores were independent risk factors for CnSKP-BSIs. The 30-day mortality was higher in patients with CnSKP than in those with CSKP (58.5% vs 15.4%; P<0.001). In patients with KP-BSIs, neutropenia, multiple organ dysfunction, respiratory failure, CnSKP infection, high APACHE II score, and tigecycline therapy were independently associated with higher mortality risk. Among patients whose APACHE II score was <15, higher mortality rates were observed in patients treated with tigecycline than in those treated with other antibiotics (45.3% vs 7.7%; P<0.001). Central venous catheterization, multiple organ dysfunction, and high APACHE II scores were independent risk factors for death from CnSKP.

Conclusion

A significant increase in the incidence of CnSKP-BSIs was observed during the study period, with a higher mortality rate found in these patients. Exposure to carbapenems and severe illness were independent risk factors for the development of CnSKP-BSIs, and tigecycline therapy resulted in a significant increase in mortality.

Pharmacokinetic and Pharmacodynamic Considerations of Antibiotics of Last Resort in Treating Gram-Negative Infections in Adult Critically Ill Patients

PURPOSE OF REVIEW

We provide an overview of antimicrobials that are considered last resort for the treatment of resistant gram-negative infections in adult critically ill patients. The role in therapy, pharmacodynamic (PD) goals, and pharmacokinetic (PK) changes in critical illness for aminoglycosides, polymyxins, tigecycline, fosfomycin, and fluoroquinolones are summarized.

RECENT FINDINGS

Altered PK in septic patients in the intensive care unit (ICU) is observed with many of our agents of last resort. Based on the available literature, dosage adjustments may be required to optimize PK parameters and meet PD targets for most effective bacterial killing. Data is limited, studies are conducted in heterogeneous patient populations, and conclusions are frequently conflicting. Strategic dosing regimens such as high-dose extended interval dosing of aminoglycosides or loading doses with colistin and polymyxin B are examples of ways to optimize antibiotic PK in critically ill patients. Benefits of these strategies must be balanced with risks of increased toxicity. Patients with resistant gram-negative infections may present with septic shock in the ICU. Sepsis can significantly alter the PK of antibiotics and require dosage adjustments to attain optimal drug levels. An understanding of PK and PD properties of these agents of last resort will help to maximize therapeutic efficacy while minimizing toxic effects.

Once Daily High Dose Tigecycline Is Optimal: Tigecycline PK/PD Parameters Predict Clinical Effectiveness

OBJECTIVE

The clinical effectiveness of tigecycline depends on appropriate use, and PK/PD (pharmacokinetic/pharmacodynamic) parameters related to dose and dosing interval.

METHODS

In our 600-bed university-affiliated teaching hospital, we conducted a tigecycline efficacy review over a three-month period in 34 evaluable patients. Parameters assessed included clinical response, cure or treatment failure, once daily as q12h dosing, maintenance dosing, high dose vs. standard loading regimens, adverse effects, and the effect of infectious disease consultation on outcomes.

RESULTS

We found once daily high dose tigecycline (HDT) was highly effective in treating serious systemic infections due to MDR Gram-positive/negative pathogens as well as C. difficile colitis. Adverse effects were infrequent and limited to mild nausea/vomiting. Once daily HDT was highly effective, and the few treatment failures were related to suboptimal/split dosing regimens.

CONCLUSION

Once daily HDT was highly effective when used to treat susceptible pathogens and when optimally dosed, i.e., 200-400 mg (IV) loading dose ×1, followed by a once daily maintenance dose of 100-200 mg (IV) q24h.

Salvage tigecycline in high risk febrile neutropenic patients with hematological malignancies: a prospective multicenter study

The purpose of this prospective, multi-center study was to examine the efficacy and safety of tigecycline as empirical treatment in neutropenic patients with hematological malignancies who failed to respond to first-line antibiotics. A total of 125 patients with persistent fever (>72 h) despite first-line antibiotics received empirical treatment with tigecycline (loading dose of 100 mg, followed by 50 mg every 12 h). The use of other antimicrobial agents was not restricted. Treatment success rate was 68.0%. Subgroup analysis revealed a success rate of 73.1% in patients with pneumonia and 35.3% in patients with bacteremia. Toxicities were moderate with gastrointestinal symptoms being the main side effects. In conclusion, tigecycline-based antibacterial regimen was a justifiable empirical treatment in febrile neutropenic patients who failed to respond to first-line antibiotics except those with bacteremia. For patients with bacteremia, trials on higher-dose of tigecycline are needed.

Treatment of Infections Caused by Extended-Spectrum-Beta-Lactamase-, AmpC-, and Carbapenemase-Producing Enterobacteriaceae

Therapy of invasive infections due to multidrug-resistant Enterobacteriaceae (MDR-E) is challenging, and some of the few active drugs are not available in many countries. For extended-spectrum β-lactamase and AmpC producers, carbapenems are the drugs of choice, but alternatives are needed because the rate of carbapenem resistance is rising. Potential active drugs include classic and newer β-lactam-β-lactamase inhibitor combinations, cephamycins, temocillin, aminoglycosides, tigecycline, fosfomycin, and, rarely, fluoroquinolones or trimethoprim-sulfamethoxazole. These drugs might be considered in some specific situations. AmpC producers are resistant to cephamycins, but cefepime is an option. In the case of carbapenemase-producing Enterobacteriaceae (CPE), only some "second-line" drugs, such as polymyxins, tigecycline, aminoglycosides, and fosfomycin, may be active; double carbapenems can also be considered in specific situations. Combination therapy is associated with better outcomes for high-risk patients, such as those in septic shock or with pneumonia. Ceftazidime-avibactam was recently approved and is active against KPC and OXA-48 producers; the available experience is scarce but promising, although development of resistance is a concern. New drugs active against some CPE isolates are in different stages of development, including meropenem-vaborbactam, imipenem-relebactam, plazomicin, cefiderocol, eravacycline, and aztreonam-avibactam. Overall, therapy of MDR-E infection must be individualized according to the susceptibility profile, type, and severity of infection and the features of the patient.

Efficacy and safety of tigecycline monotherapy versus combination therapy for the treatment of hospital-acquired pneumonia (HAP): a meta-analysis of cohort studies

The broad spectrum antibiotic tigecycline shows promising efficacy against many multiple drug resistant (MDR) pathogens. However, its clinical efficacy in the treatment of hospital-acquired pneumonia (HAP) is unclear. Several studies have reported on the treatment failures of tigecycline monotherapy, suggesting that it may not be sufficient to control severe infections. Combination therapy has become an option to treat MDR bacterial infections. We conducted a literature search using PubMed, Cochrane Library, Embase, Elsevier and the Web of Knowledge databases up to 29 February 2017 to identify relevant published studies. Studies were considered eligible if they were a cohort study that assessed mortality and the safety of tigecycline monotherapy versus combination therapy with other antimicrobial agents for HAP. The primary outcome was treatment mortality rate, while the secondary outcomes were adverse events. Meta-analysis was done using fixed-effects models. Five trials were included. The monotherapy tigecycline had a higher mortality compared to the combination therapy group. There was a significant difference for the treatment of HAP. However, two prospective cohort studies showed that there was no significant difference in mortality rate between the tigecycline monotherapy and the tigecycline combination therapy. Three retrospective cohort studies showed that tigecycline monotherapy had a high mortality rate. Tigecycline combination therapy efficiently treats HAP. There is a great need for well-designed studies to evaluate the effectiveness and safety of combination therapies as they compare to tigecycline monotherapy.

High-dose tigecycline for the treatment of nosocomial carbapenem-resistant Klebsiella pneumoniae bloodstream infections: A retrospective cohort study

Carbapenem-resistant Klebsiella pneumoniae (CRKP) bloodstream infection (BSI) has become increasingly frequent threat recently, especially in the intensive care unit (ICU). High-dose tigecycline (TGC) regimen is proposed due to the limitation of treatment options. We investigated the efficacy and safety of high-dose TGC combination regimens for treating CRKP BSI. Furthermore, the risk factors for mortality were also determined.This was a single center retrospective cohort study conducted from 2014 to 2016. A total of 40 patients with nosocomial CRKP BSI admitted to the ICU were included; they were classified into two groups according to the treatment regimens with high-dose TGC (HD group) or not (non-HD group). In-hospital mortality rates and microbiologic responses from both groups were reviewed and compared. Besides, the survival and non-survival groups were compared to identify the risk factors of mortality.Twenty-three patients constituted the HD group (high-dosage TGC regimen was administered as 200 mg loading dose followed by 100 mg every 12 h) and 17 patients constituted the non-HD group (standard dose TGC therapy as 100 mg loading dose followed by 50 mg every 12 h and other antibiotics). The in-hospital mortality was 52.2% in the HD group and 76.5% in the non-HD group (P = .117). The Kaplan-Meier test showed significantly longer survival times in the HD group (mean: 83 days vs 28 days; P = .027). Microbiological eradication was observed in 13 patients (56.5%) in the HD group and 6 patients (36.3%) in the non-HD group (P = .184). A smaller fraction of patients in the HD group were subjected to vasoactive therapy (52.2% vs 88.2%; P = .016) compared to the non-HD group. There was no significant difference in the manifestation of adverse effects between the two groups. In the multivariate analysis, multiple organ dysfunction syndrome (MODS), vasoactive therapy, and exposure to carbapenems were regarded as the independent predictors of mortality.A therapeutic regimen consisting of a high dose of TGC was associated with significantly longer survival time and numerically lower mortality in CRKP BSI. Adverse events were not increased with the double dose therapy.

Tigecycline-associated hypofibrinogenemia: A case report and review of the literature

Tigecycline, a glycylcycline-derived antibacterial that has been approved for the treatment of various infections, is widely used for multi-drug resistant bacteria. Coagulopathy is an uncommon side effect during tigecycline treatment and is easily overlooked when it occurs. We reported the effect of tigecycline (50 mg every twelve hours) treatment in an 87-year-old man, with Gram negative bacillary pneumonia and respiratory failure. After 7 days of tigecycline treatment, a significant drop of hemoglobin and patchy ecchymosis over both thighs were suddenly observed despite stable clinical condition. There was no abnormality in his platelet count and coagulation profile except for low fibrinogen level. Ecchymosis and anemia subsided gradually after blood component therapy. Although his clinical condition improved, hypofibrinogenemia persisted and recovered after 5 days of tigecycline discontinuation, suggesting probable tigecycline associated hypofibrinogenemia.

Burden and Management of Multidrug-Resistant Organisms in Palliative Care

Palliative care includes comprehensive strategies to optimize quality of life for patients and families confronting terminal illness. Infections are a common complication in terminal illness, and infections due to multidrug-resistant organisms (MDROs) are particularly challenging to manage in palliative care. Limited data suggest that palliative care patients often harbor MDRO. When MDROs are present, distinguishing colonization from infection is challenging due to cognitive impairment or metastatic disease limiting symptom assessment and the lack of common signs of infection. Multidrug-resistant organisms also add psychological burden through infection prevention measures including patient isolation and contact precautions which conflict with the goals of palliation. Moreover, if antimicrobial therapy is indicated per goals of care discussions, available treatment options are often limited, invasive, expensive, or associated with adverse effects that burden patients and families. These issues raise important ethical considerations for managing and containing MDROs in the palliative care setting.

Activity of cefiderocol (S-649266) against carbapenem-resistant Gram-negative bacteria collected from inpatients in Greek hospitals

Background

Cefiderocol (S-649266), a siderophore cephalosporin, utilizes a novel mechanism of entry into the periplasmic space of Gram-negative bacteria and is broadly stable to ESBLs and carbapenemases.

Methods

A collection of carbapenem-resistant Gram-negative bacteria isolated from clinical specimens in 18 Greek hospitals was tested for susceptibility to cefiderocol, meropenem, ceftazidime, cefepime, ceftazidime/avibactam, ceftolozane/tazobactam, aztreonam, amikacin, ciprofloxacin, colistin and tigecycline. Broth microdilution plates were used to determine MICs.

Results

In total 189 non-fermentative Gram-negative bacteria (107 Acinetobacter baumannii and 82 Pseudomonas aeruginosa ) and 282 Enterobacteriaceae (including 244 Klebsiella pneumoniae , 14 Enterobacter cloacae and 11 Providencia stuartii ) were studied. For both A. baumannii and P. aeruginosa the MIC 90 of cefiderocol was 0.5 mg/L. For K. pneumoniae , E. cloacae and P. stuartii the MIC 90 of cefiderocol was 1, 1 and 0.5 mg/L, respectively. Tigecycline was the second most active antibiotic, followed by colistin.

Conclusions

Cefiderocol exhibited greater antimicrobial activity in vitro against carbapenem-resistant Gram-negative bacteria than comparator antibiotics.