Use of colistin in adult patients: A cross-sectional study

Clinical effectiveness of cefiderocol for the treatment of bloodstream infections due to carbapenem-resistant Acinetobacter baumannii during the COVID-19 era: a single center, observational study

BACKGROUND

We assessed the clinical effectiveness of cefiderocol (CFDC) in comparison with colistin (COL) for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) bloodstream infections (BSI).

MATERIALS/METHODS

Retrospective cohort study including adults with CRAB-BSI. Outcomes were mortality, clinical cure and adverse events during therapy. The average treatment effect of CFDC compared to COL was weighted with the inverse-probability treatment weight (IPTW).

RESULTS

Overall, 104 patients were included (50 CFDC, 54 COL), median age 66.5 years, median Charlson Comorbidity Index 5, septic shock in 33.6% of patients. Primary BSI accounted for 43.3% of cases, followed by ventilator-associated pneumonia (VAP) (26%), catheter-related BSI (20.2%) and hospital-acquired pneumonia (HAP) (9.6%). Although not significantly, mortality at all time points was lower for CFDC than COL, while clinical cure was higher in CFDC than COL (66% vs. 44.4%, p = 0.027). Adverse events were more frequent in COL than CFDC-group (38.8% vs. 10%, p < 0.0001), primarily attributed to acute kidney injury (AKI) in the COL group. Patients with bacteremic HAP/VAP treated with CFDC had a significant lower 30-d mortality and higher clinical cure than COL (p = 0.008 and p = 0.0008, respectively). Increment of CCI (p = 0.005), ICU (p = 0.025), SARS-CoV2 (p = 0.006) and ECMO (p < 0.0001) were independently associated with 30-d mortality, while receiving CFDC was not associated with survival.

CONCLUSIONS

CFDC could represent an effective and safe treatment option for CRAB BSI, especially in patients with bacteremic HAP/VAP and frail patients where the risk of acute renal failure during therapy should be avoided.

Impact of clinical pharmacist's interventions on clinical outcomes in appropriate use of colistin: a prospective pre-post intervention study

This study aims to evaluate the clinical pharmacist's contribution impact on the appropriate use of colistin. Our study was conducted prospectively in patients in the Internal Diseases Intensive Care Unit of Gazi University Medical Faculty Hospital for eight months. The first four months of the study were with the observation group, while the next four months were with the intervention group. The study determined how the active participation of clinical pharmacists had affected the appropriateness of colistin use. The results showed that the appropriate use of colistin was higher in the intervention group than in the observational group; furthermore, incidence of nephrotoxicity was lower. The difference between both groups was statistically significant (p < 0.001, p < 0.05), respectively. This study showed that the clinical pharmacist's active intervention by following the patients increased the frequency and percentage of the appropriate use of colistin. This decreased the incidence of nephrotoxicity, colistin's most important side effect.

An overview of gram-negative bacteria with difficult-to-treat resistance: definition, prevalence, and treatment options

INTRODUCTION

Difficult-to-treat resistance (DTR) is a newly proposed resistance phenotype characterized by resistance to all first-line drugs. The emergence of DTR as a new resistance phenotype has significant implications for clinical practice. This new concept has the potential to be widely used instead of traditional phenotypes.

AREAS COVERED

This study carried out a detailed analysis about the definition, application, and evolution of various resistance phenotypes. We collected all the research articles on Gram-negative bacteria with difficult-to-treat resistance (GNB-DTR), analyzed the DTR in each region and each bacterial species. The advantages and doubts of DTR, the dilemma of GNB-DTR infections and the potential therapeutic strategies are summarized in the review.

EXPERT OPINION

Available studies show that the prevalence of GNB-DTR is not optimistic. Unlike traditional resistance phenotypes, DTR is more closely aligned with the clinical treatment perspective and can help with the prompt selection of an appropriate treatment plan. Currently, potential treatment options for GNB-DTR include a number of second-line drugs and novel antibiotics. However, the definition of first-line drugs is inherently dynamic. Therefore, the DTR concept based on first-line drugs needs to be continuously updated and refined, considering the emergence of new antibiotics, resistance characteristics, and pathogen prevalence in different regions.

Microbiologic Cure with a Simplified Dosage of Intravenous Colistin in Adults: A Retrospective Cohort Study

Purpose

Colistin's FDA weight-based dosing (WBD) and frequency are both expressed in a broad range. Therefore, a simplified fixed-dose regimen (SFDR) of intravenous colistin based on three body-weight segments has been established for adults. The SFDR falls within the WBD range of each body-weight segment and accounts for the pharmacokinetic features. This study compared microbiologic cure with colistin SFDR to WBD in critically ill adults.

Patients and Methods

A retrospective cohort study was conducted for colistin orders from January 2014 to February 2022. The study included ICU patients who received intravenous colistin for carbapenem-non-susceptible, colistin-intermediate Gram-negative bacilli infections. Patients received the SFDR after the protocol was implemented, as the WBD was previously used. The primary endpoint was microbiologic cure. Secondary endpoints were 30-day infection recurrence and acute kidney injury (AKI).

Results

Of the 228 screened patients, 84 fulfilled the inclusion and matching criteria (42 in each group). The microbiologic cure rate was 69% with the SFDR and 36% with the WBD [p=0.002]. Infection recurred in four of the 29 patients who had a microbiologic cure with the SFDR (14%), and in six of the 15 patients with WBD (40%); [p=0.049]. AKI occurred in seven of the 36 SFDR patients who were not on hemodialysis (19%) and 15 of the 33 WBD patients (46%); [p=0.021].

Conclusion

In this study, colistin SFDR was associated with a higher microbiologic cure in carbapenem-non-susceptible, colistin-intermediate Gram-negative bacilli infections and with a lower incidence of AKI in critically ill adults compared to WBD.

Acinetobacter baumannii in the critically ill: complex infections get complicated

Acinetobacter baumannii is increasingly associated with various epidemics, representing a serious concern due to the broad level of antimicrobial resistance and clinical manifestations. During the last decades, A. baumannii has emerged as a major pathogen in vulnerable and critically ill patients. Bacteremia, pneumonia, urinary tract, and skin and soft tissue infections are the most common presentations of A. baumannii, with attributable mortality rates approaching 35%. Carbapenems have been considered the first choice to treat A. baumannii infections. However, due to the widespread prevalence of carbapenem-resistant A. baumannii (CRAB), colistin represents the main therapeutic option, while the role of the new siderophore cephalosporin cefiderocol still needs to be ascertained. Furthermore, high clinical failure rates have been reported for colistin monotherapy when used to treat CRAB infections. Thus, the most effective antibiotic combination remains disputed. In addition to its ability to develop antibiotic resistance, A. baumannii is also known to form biofilm on medical devices, including central venous catheters or endotracheal tubes. Thus, the worrisome spread of biofilm-producing strains in multidrug-resistant populations of A. baumannii poses a significant treatment challenge. This review provides an updated account of antimicrobial resistance patterns and biofilm-mediated tolerance in A. baumannii infections with a special focus on fragile and critically ill patients.

Burden of severe infections due to carbapenem-resistant pathogens in intensive care unit

Intensive care units (ICU) for various reasons, including the increasing age of admitted patients, comorbidities, and increasingly complex surgical procedures (e.g., transplants), have become "the epicenter" of nosocomial infections, these are characterized by the presence of multidrug-resistant organisms (MDROs) as the cause of infection. Therefore, the perfect match of fragile patients and MDROs, as the cause of infection, makes ICU mortality very high. Furthermore, carbapenems were considered for years as last-resort antibiotics for the treatment of infections caused by MDROs; unfortunately, nowadays carbapenem resistance, mainly among Gram-negative pathogens, is a matter of the highest concern for worldwide public health. This comprehensive review aims to outline the problem from the intensivist's perspective, focusing on the new definition and epidemiology of the most common carbapenem-resistant MDROs (Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales) to emphasize the importance of the problem that must be permeating clinicians dealing with these diseases.

Cefiderocol-Based versus Colistin-Based Regimens for Severe Carbapenem-Resistant Acinetobacter baumannii Infections: A Propensity Score-Weighted, Retrospective Cohort Study during the First Two Years of the COVID-19 Pandemic

BACKGROUND

A large increase in multi-drug-resistant Acinetobacter baumannii, especially carbapenem-resistant strains, occurred during the first two years of the COVID-19 pandemic, posing important challenges in its treatment. Cefiderocol appeared to be a good option for the treatment of Carbapenem-resistant Acinetobacter baumannii (CR-Ab), but to date, the guidelines and evidence available are conflicting.

METHODS

We retrospectively included a group of patients with CR-Ab infections (treated with colistin- or cefiderocol-based regimens) at Padua University Hospital (August 2020-July 2022) and assessed predictors of 30-day mortality, and differences in microbiological and clinical treatment. To evaluate the difference in outcomes, accounting for the imbalance in antibiotic treatment allocation, a propensity score weighting (PSW) approach was adopted.

RESULTS

We included 111 patients, 68% males, with a median age of 69 years (IQR: 59-78). The median duration of antibiotic treatment was 13 days (IQR:11-16). In total, 60 (54.1%) and 51 (45.9%) patients received cefiderocol- and colistin-based therapy, respectively. Notably, 53 (47.7%) patients had bloodstream infections, while 58 (52.3%) had pneumonia. Colistin was combined in 96.1%, 80.4%, and 5.8% of cases with tigecycline, meropenem, and fosfomycin, respectively. Cefiderocol was combined in 13.3%, 30%, and 18.3% of cases with fosfomycin, tigecycline, and meropenem, respectively. At the baseline, the two treatment groups significantly differed in age (patients treated with colistin were significantly older), the prevalence of diabetes and obesity (more frequent in the group treated with colistin), length of stay (longer in the group receiving cefiderocol), and type of infection (BSI were more frequent in the group receiving cefiderocol). The proportion of patients who developed acute kidney injury was significantly higher in the colistin group. By using PSW, no statistically significant differences emerged for mortality or clinical and microbiological cure between the two groups. No independent predictors were detected for hospital mortality or clinical cure, while for the length of stay, the only selected predictor was age, with a non-linear effect (p-value 0.025 for non-linearity) on the prolongation of hospital stay of 0.25 days (95% CI 0.10-0.39) at increasing ages (calculated over the IQR).

CONCLUSIONS

Cefiderocol treatment did not differ in terms of main outcomes and safety profile from colistin-based regimens. More prospective studies with a larger number of patients are required to confirm our results.

Empirical antibiotic therapy for difficult-to-treat Gram-negative infections: when, how, and how long?

PURPOSE OF REVIEW

To discuss empirical therapy for severe infections due to Gram-negative bacteria with difficult-to-treat resistance (GNB-DTR) in current clinical practice, focusing in particular on the positioning of novel therapeutic agents and rapid diagnostic tests.

RECENT FINDINGS

The current era of novel agents active against GNB-DTR and showing differential activity against specific determinants of resistance is an unprecedented scenario, in which the clinical reasoning leading to the choice of the empirical therapy for treating severe GNB-DTR infections is becoming more complex, but it also allows for enhanced treatment precision.

SUMMARY

Novel agents should be used in line with antimicrobial stewardship principles, aimed at reducing selective pressure for antimicrobial resistance. However, this does not mean that they should not be used. Indeed, excesses in restrictive uses may be unethical by precluding access to the most effective and less toxic treatments for patients with severe GNB-DTR infections. Given these premises (the 'how'), empirical treatment with novel agents should be considered in all patients with risk factors for GNB-DTR and severe clinical presentation of acute infection (the 'when'). Furthermore, empirical novel agents should preferably be continued only for a few hours, until de-escalation, modification, or confirmation (as targeted therapy) is made possible by the results of rapid diagnostic tests (the 'how long').

Assessing Colistin Resistance by Phenotypic and Molecular Methods in Carbapenem-resistant Enterobacterales in a Tertiary Care Hospital in Pakistan

Introduction

Members of Enterobacterales are very common pathogens, which continue to show resistance to many antibiotics. Carbapenem performed well for some time. Colistin was the final hope for the carbapenem-resistant Enterobacterales, but resistance against it has virtually tied the clinician's hands, especially when it comes to treating critically ill patients.

Purpose

Detection of colistin resistance by the agar method as well as by the polymerase chain reaction (mobilized colistin resistance-1 gene) in carbapenem-resistant Enterobacterales.

Materials and Methods

A cross-sectional study from Dec 2019 to Dec 2020 was conducted at the Department of Microbiology, Army Medical College, National University of Medical Sciences Rawalpindi Pakistan. Antimicrobial susceptibility of Enterobacterales was determined according to the Kirby-Bauer disc diffusion method except for colistin. Colistin agar was used, in concentrations of 2 µg/mL and 4 µg/mL. Results were interpreted according to Clinical and Laboratory Standards Institute guidelines 2020. Mobilized colistin-resistant-1 gene in the carbapenem resistant Enterobacterales was detected by performing real-time polymerase chain reaction assay.

Results

Among the 172 carbapenem-resistant Enterobacterales 18 isolates were resistant using the colistin agar test. Whereas by molecular method colistin resistance was detected among 10 isolates that carried mobilized colistin resistance 1 gene, making the frequency of the MCR-1 gene 5.81%. Seventy percent of isolates were from paired blood samples. Eight patients, from whom the colistin resistant gene was isolated expired.

Conclusion

Colistin resistance is a very serious issue and should not be missed in a clinical microbiology laboratory. The phenotypic agar test method is an excellent option for routine use, as it combines ease of performance with affordable cost. However, molecular methods are essential for the detection of mobilized colistin resistance gene (1-9) for epidemiological purposes.

Resistance to beta-lactams in Gram-negative bacilli: relevance and potential therapeutic alternatives

The indiscriminate and massive antibiotic use in the clinical practice and in agriculture or cattle during the past few decades has produced a serious world health problem that entails high morbidity and mortality: the antibiotic multi-drug resistance. In 2017 and 2019, the World Health Organization published a list of urgent threats and priorities in the context of drug resistance, which only included Gram-negative bacteria and specially focused on carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa, as well as carbapenem and third generation cephalosporin-resistant Enterobacteriaceae. This scenario emphasizes the need of developing and testing new antibiotics from different families, such as new beta-lactams, highlighting cefiderocol and its original mechanism of action; new beta-lactamase inhibitors, with vaborbactam or relebactam among others; new quinolones such as delafloxacin, and also omadacycline or eravacycline, as members of the tetracycline family. The present work reviews the importance and impact of Gram-negative bacterial infections and their resistance mechanisms, and analyzes the current therapeutic paradigm as well as the role of new antibiotics with a promising future in the era of multi and pan-drug resistance.

Colistin Therapy, Survival and Renal Replacement Therapy in Burn Patients: A 10-Year Single-Center Cohort Study

Purpose

Patients and Methods

Results

Conclusion

Editorial for the Special Issue: "Current and Novel Antimicrobial Strategies for Bacterial and Fungal Infections by Resistant Organisms"

The pandemic driven by the SARS-CoV-2 infection has compelled health services globally to direct all available human and economic resources toward fighting the novel coronavirus [...].

Clinical Efficacy and Nephrotoxicity of the Loading Dose Colistin for the Treatment of Carbapenem-Resistant Acinetobacter baumannii in Critically Ill Patients

Carbapenem-resistant Acinetobacter baumannii (CRAB) is one of the most common causes of nosocomial infections in critically ill patients. Colistin methanesulfonate (CMS), an inactive prodrug, has been considered as a last-resort treatment for CRAB infection in critically ill patients. The objective of this study was to assess 30-day survival and nephrotoxicity in critically ill patients who received non-loading dose (LD) versus LD of CMS for CRAB infection treatment. Between 2012 and 2017, this retrospective cohort analysis was performed at Chiang Mai University Hospital (CMUH), focusing on critically ill patients with CRAB infection who received either non-LD or LD of CMS. A total of 383 patients met the criteria for inclusion. At the 30th day of treatment, the survival rate of patients in the LD CMS group was 1.70 times (adjusted HR) of those in the non-LD group (95% CI = 1.17-2.50, p = 0.006). Clinical response was significantly higher in the LD CMS group than non-LD CMS group (aHR, 1.35, 95% CI, 1.01-1.82, p = 0.046). In addition, a microbiological response-eradication of pre-treatment isolated pathogens in post-treatment cultures-in patients with LD CMS was 1.57 times that of patients with non-LD CMS (95% CI, 1.15-2.15, p = 0.004). Additionally, there was a significant difference in nephrotoxicity between LD CMS and non-LD CMS (aHR, 1.57, 95% CI, 1.14-2.17, p = 0.006). Based on these results, LD CMS should be used to increase the opportunity of patients to achieve favourable outcomes. However, LD CMS was found associated with an increase in nephrotoxicity, so renal function should be closely monitored when LD colistin was administered.

Factors Associated with Inadequate Intravenous Colistin Dosages: Post Hoc Analysis of a Multicenter, Cross-Sectional Study

Colistin is a last-resort agent for the treatment of infections due to Gram-negative bacteria with difficult-to-treat resistance. The primary objective of this post hoc analysis of a cross-sectional study conducted in 22 Italian hospitals was to assess factors associated with inadequate intravenous colistin dosage. Overall, 187 patients receiving intravenous colistin were included in the analyses. Inadequate colistin dosages were administered in 27% of cases (50/187). In multivariable analysis, AKI (dummy variable with KDIGO stage 0 as a reference, odds ratio (OR) 3.98 with 95% confidence interval (CI) 1.48–10.74 for stage 1, OR 4.44 with 95% CI 1.17–16.93 for stage 2, OR 9.41 with 95% CI 1.59–55.70 for stage 3; overall p = 0.001) retained an independent association with inadequate colistin dosage, whereas the presence of a central venous catheter was associated with adequate colistin dosage (OR: 0.34 for inadequate dosage, 95% CI: 0.16–0.72, p = 0.004). These results were confirmed in an additional multivariable model with the center as a random effect. The association between AKI and inadequate dosage may reflect the perception of an increased risk of nephrotoxicity in patients with impaired renal function, which nonetheless should not be accompanied by dosage reductions beyond those recommended and could represent the target of dedicated antimicrobial stewardship efforts.

Current and future perspectives in the treatment of multidrug-resistant Gram-negative infections

Microbial resistance is a serious threat to human health worldwide. Among the World Health Organisation's list of priority resistant bacteria, three are listed as critical-the highest level of concern-and all three are Gram-negative. Gram-negative resistance has spread worldwide via a variety of mechanisms, the most problematic being via AmpC enzymes, extended-spectrum β-lactamases, and carbapenemases. A combination of older drugs, many with high levels of toxicity, and newer agents are being used to combat multidrug resistance, with varying degrees of success. This review discusses the current treatments for multidrug-resistant Gram-negative bacteria, including new agents, older compounds, and new combinations of both, and some new treatment targets that are currently under investigation.

Multidisciplinary approach to a septic COVID-19 patient undergoing veno-venous extracorporeal membrane oxygenation and receiving thoracic surgery

A multidisciplinary approach appears to be fundamental for the treatment of critically ill patients with COVID-19, improving clinical outcomes, even in the most severe cases. Such severe cases are advisable to be collegially discussed between intensivists, surgeons, infectious disease, and other physicians potentially involved.

Resistance to ceftazidime/avibactam in infections and colonisations by KPC-producing Enterobacterales: a systematic review of observational clinical studies

OBJECTIVES

Ceftazidime/avibactam (CAZ-AVI), approved in 2015, is an important first-line option for Klebsiella pneumoniae carbapenemase-producing Enterobacterales (KPC-E). Although still uncommon, resistance to CAZ-AVI has emerged and may represent a serious cause of concern.

METHODS

We performed a systematic literature review of clinical and microbiological features of infections and colonisations by CAZ-AVI-resistant KPC-E, focused on the in vivo emergence of CAZ-AVI resistance in different clinical scenarios.

RESULTS

Twenty-three papers were retrieved accounting for 42 patients and 57 isolates, mostly belonging to K. pneumoniae ST258 harbouring D179Y substitution in the KPC enzyme. The USA, Greece and Italy accounted for 80% of cases. In one-third of isolates resistance was not associated with previous CAZ-AVI exposure. Moreover, 20% of the strains were colistin-resistant and 80% were extended-spectrum β-lactamase (ESBL)-producers. The majority of infected patients had severe underlying diseases (39% cancer, 22% solid-organ transplantation) and 37% died. The abdomen, lung and blood were the most involved infection sites. Infections by CAZ-AVI-resistant strains were mainly treated with combination therapy (85% of cases), with meropenem being the most common (65%) followed by tigecycline (30%), gentamicin (25%), colistin (25%) and fosfomycin (10%). Despite the emergence of resistance, 35% of patients received CAZ-AVI.

CONCLUSION

Taken together, these data highlight the need for prompt susceptibility testing including CAZ-AVI for Enterobacterales, at least in critical areas. Resistance to CAZ-AVI is an urgent issue to monitor in order to improve both empirical and targeted CAZ-AVI use as well as the management of patients with infections caused by CAZ-AVI-resistant strains.

Emergence of Nosocomial Pneumonia Caused by Colistin-Resistant Escherichia coli in Patients Admitted to Chest Intensive Care Unit

(1) Background: Colistin is a last-resort antibiotic used in treating multidrug-resistant Gram-negative infections. The growing emergence of colistin resistance in Escherichia coli (E. coli) represents a serious health threat, particularly to intensive care unit (ICU) patients. (2) Methods: In this work, we investigated the emergence of colistin resistance in 140 nosocomial E. coli isolated from patients with pneumonia and admitted to the chest ICU over 36 months. Virulence and resistance-related genes and E. coli pathotypes in colistin-resistant and colistin-sensitive isolates were determined. (3) Results: Colistin resistance was observed in 21/140 (15%) of the nosocomial E. coli isolates. The MIC₅₀ of the resistant strains was 4 mg/L, while MIC₉₀ was 16 mg/L. Colistin-resistant isolates were also co-resistant to amoxicillin, amoxicillin/clavulanic, aztreonam, ciprofloxacin, and chloramphenicol. The mechanism of colistin resistance was represented by the presence of mcr-1 in all resistant strains. Respectively, 42.9% and 36.1% of colistin-resistant and colistin-sensitive groups were extended-spectrum β-lactamase (ESBL) producers, while 23.8% and 21% were metallo β-lactamase (MBL) producers. bla_TEM-type was the most frequently detected ESBL gene, while bla_IMP-type was the most common MBL in both groups. Importantly, most resistant strains showed a significantly high prevalence of astA (76.2%), aggR (76.2%), and pic (52.4%) virulence-related genes. Enteroaggregative E. coli (76%) was the most frequently detected genotype among the colistin-resistant strains. (4) Conclusion: The high colistin resistance rate observed in E. coli strains isolated from patients with nosocomial pneumonia in our university hospital is worrisome. These isolates carry different drug resistance and virulence-related genes. Our results indicate the need for careful monitoring of colistin resistance in our university hospital. Furthermore, infection control policies restricting the unnecessary use of extended-spectrum cephalosporins and carbapenems are necessary.

The Impact of Carbapenem Resistance on Mortality in Patients With Klebsiella Pneumoniae Bloodstream Infection: An Individual Patient Data Meta-Analysis of 1952 Patients

INTRODUCTION

Available evidence from observational studies and meta-analyses has highlighted an increased mortality in patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) bloodstream infections (BSI) compared with their carbapenem-susceptible (CSKP) counterparts, but the exact reasons for this outcome difference are still to be determined.

METHODS

We updated the search of a previous meta-analysis through four databases up to April 2018. A two-stage individual-patient data (IPD) meta-analysis was conducted, building an adjusting model to account for age, comorbidities and activity of empirical and targeted antimicrobial therapy. The protocol was registered on PROSPERO (identifier: CRD42018104256).

RESULTS

IPD data were obtained from 14 out of 28 eligible observational studies. A total of 1952 patients were investigated: 1093 in the CRKP group and 859 in the CSKP group. Patients with CRKP-BSI had a twofold risk of death compared with CSKP-infected patients [adjusted odds ratio (aOR) 2.17; 95% confidence interval (CI) 1.56-3.04; I² = 44.1%]. Mortality was higher in patients with CRKP BSI, in both the subgroup of absent/inactive (aOR 1.75; 95% CI 1.24-2.47; I² = 0) and of active initial therapy (aOR 2.66; 95% CI 1.70-4.16; I² = 16%) as well as in case of active targeted therapy (aOR 2.21; 95% CI 1.36-3.59; I² = 58%).

CONCLUSION

Resistance to carbapenem is associated with worse outcome in patients with BSI by Klebsiella pneumoniae even adjusting for comorbidities and treatment appropriateness according to in vitro activity of empirical and targeted therapy. This applies to a scenario dominated by colistin-based therapies for CRKP. Further studies are needed to compare the mortality difference between CRKP and CSKP cases in the light of new anti-CRKP antimicrobials.

Spontaneous bacterial peritonitis due to carbapenemase-producing Enterobacteriaceae: Etiology and antibiotic treatment

Carbapenem antibiotics were first introduced in the 1980s and have long been considered the most active agents for the treatment of multidrug-resistant gram-negative bacteria. Over the last decade, carbapenem-resistant Enterobacteriaceae (CRE) have emerged as organisms causing spontaneous bacterial peritonitis. Infections caused by CRE have shown a higher mortality rate than those caused by bacteria sensitive to carbapenem antibiotics. Current antibiotic guidelines for the treatment of spontaneous bacterial peritonitis are insufficient, and rapid de-escalation of empiric antibiotic treatment is not widely recognized. This review summarizes the molecular characteristics, epidemiology and possible treatment of spontaneous bacterial peritonitis caused by CRE.

Treatment of severe infections due to metallo-β-lactamases-producing Gram-negative bacteria

In the last decades, there was an important paucity of agents for adequately treating infections due to metallo-β-lactamases-producing Gram-negative bacteria (MBL-GNB). Cefiderocol, a novel siderophore cephalosporin showing in vitro activity against MBL-GNB, has been recently marketed, and a combination of aztreonam and ceftazidime/avibactam has shown a possible favorable effect on survival of patients with severe MBL-GNB infections in observational studies. Other agents showing in vitro activity against MBL-GNB are currently in clinical development (e.g., cefepime/taniborbactam, LYS228, cefepime/zidebactam) that could be an important addition to our future armamentarium for severe MBL-GNB infections. Nonetheless, we should not discontinue our efforts to optimize the use of non-β-lactams agents, since they could remain an essential last-resort or alternative option in selected cases.

Therapeutic options for difficult-to-treat Acinetobacter baumannii infections: a 2020 perspective

INTRODUCTION

Treatment of severe infections due to Acinetobacter baumannii with difficult-to-treat resistance (DTR-AB), which exhibits resistance to all β-lactams, β-lactam/β-lactamases inhibitor combinations, and fluoroquinolones, remains a challenge for clinicians.

AREAS COVERED

The present perspective provides a personal view on both current and future agents for the treatment of severe DTR-AB infections.

EXPERT OPINION

We currently are in a transition era for the treatment of DTR-AB infections, where in the past 20 years, polymyxin-based regimens have become the most used approach (although possibly suboptimal, there were few or no alternatives) and where in the next 20 years, polymyxins will likely be replaced by less toxic novel agents as first-line choices. Two novel antimicrobial agents have been recently approved that show activity against DTR-AB, cefiderocol and eravacycline, while durlobactam/sulbactam is in phase-3 of clinical development. In the near future, these agents could become important first-line choices for the treatment of DTR-AB within approved indications, or for off-label indications in the absence of dependable alternatives. Good-quality post-marketing experiences remain necessary for arising clinically relevant questions and guiding the design of further dedicated randomized controlled trials to stably optimize the use of novel agents for DTR-AB infections in the next decades.

Optimization of inhalable liposomal powder formulations and evaluation of their in vitro drug delivery behavior in Calu-3 human lung epithelial cells

Inhalation therapy has advantages for the treatment of multidrug resistant bacterial lung infections with high drug concentrations at the infection sites in the airways and reduced systemic exposure. We have developed liposomal formulations for pulmonary delivery of synergistic ciprofloxacin (Cipro) and colistin (Col) as the potential candidate for treatment of lung infections caused by multidrug resistant Gram-negative bacteria. This study aims to: (1) further optimize the powder formulation by adding drying stabilizers (polyvinyl pyrrolidone or poloxamer) to protect the liposomes during spray-freeze-drying; (2) evaluate the transport and cellular uptake of drugs in a human lung epithelial Calu-3 cell model. The liposomal powder formulations were produced using the ultrasonic spray-freeze-drying technique. The optimal formulation (F5) used mannitol (8% w/v) and sucrose (2% w/v) as the internal lyoprotectants. Adding external lyoprotectants/aerosolization enhancers (i.e. 8% w/v mannitol, 2% w/v sucrose and 1%, w/w PVP 10) produced the superior rehydrated EE values of ciprofloxacin and colistin (50.2 ± 0.9% for Cipro and 37.8 ± 1.2% for Col) as well as satisfactory aerosol performance (FPF: 34.2 ± 0.8% for Cipro and 33.6 ± 0.9% for Col). The cytotoxicity study indicated that F5 with the colistin concentration at 50 μg/mL and ciprofloxacin at 200 μg/mL was not cytotoxic to human lung epithelial Calu-3 cells. The intracellular uptake of ciprofloxacin was concentration-dependent in Calu-3 cells and the uptake of A-B was more than that of B-A for all samples (p < 0.05). This study demonstrates that co-delivery of ciprofloxacin and colistin in a single liposome can lower the transport capability of both drugs across the Calu-3 cell monolayer and their accumulation in the cells. These findings indicate that co-loaded liposomal powder of ciprofloxacin and colistin is a promising potential treatment for respiratory infections caused by multidrug resistant Gram-negative bacteria.

Novel strategies for the management of bacterial and fungal infections in patients with liver cirrhosis: focus on new antimicrobials

Introduction: Liver cirrhosis is a frequent condition caused by different etiologies. Bacterial and fungal infections are common complications, representing an independent prognostic stage in patients with cirrhosis, dramatically worsening their clinical outcomes.Areas covered: The present review article addresses manifold points and to this purpose an inductive literature search of MEDLINE database through PubMed was performed. First, it provides an overview on the mechanisms underlying immune disfunctions in patients with cirrhosis, who are prone to develop infections being at higher risk than the general population. Second, commonest types of bacterial and fungal infections in patients with advanced liver disease are described, focusing on their deleterious impact as decompensating events. Third, the rise of multidrug-resistant (MDR) bacteria and fungi as causative agents of infection in cirrhotic subjects is illustrated. Eventually, the most promising novel therapeutic options against MDR pathogens and fungi are reviewed.Expert opinion: The management of bacterial and fungal infections in patients with cirrhosis is difficult, due to the frequent co-existence of renal impairment, low platelet count and other conditions that limit the antimicrobial choice. New antibacterial and antifungal compounds may overcome this issue by providing a better tolerability profile, along with equal or superior efficacy compared with older drugs.

Ceftolozane/tazobactam for difficult-to-treat Pseudomonas aeruginosa infections: A systematic review of its efficacy and safety for off-label indications

Ceftolozane/tazobactam (C/T) is a novel β-lactam/β-lactamase inhibitor combination targeting Enterobacteriaceae and Pseudomonas aeruginosa (PA). It is approved in adult patients for complicated urinary tract infections (cUTIs) and complicated intra-abdominal infections (cIAIs) as well as for nosocomial pneumonia. It displays excellent activity against PA, even multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. The aim of this systematic review (PROSPERO protocol no. CRD42019117350) was to summarise the available evidence from observational studies regarding the efficacy and safety of off-label use of C/T when administered to treat MDR- or XDR-PA infections. The MEDLINE and Embase databases were screened from inception up to 30 June 2019. Studies were deemed eligible if they described real-life use of C/T in the case of MDR- or XDR-PA infections for non-approved indications. Exclusion criteria were cIAIs, cUTIs, pneumonia (unless occurring in a paediatric population) and infections by non-MDR/XDR-PA. Thirty articles fulfilled the inclusion criteria. In total, 130 cases of MDR- or XDR-PA infections treated with C/T in 128 patients were described. The most relevant off-label uses were skin and soft-tissue infection (49/30; 37.7%), bone and joint infection (42/130; 32.3%) and bloodstream infection (23/130; 17.7%). Five cases involved paediatric patients. The overall clinical success rate was 76.2%. The most common adverse event was hypokalaemia (4.2%, in 48 evaluable cases). C/T may be a useful therapeutic option for difficult-to-treat infections by PA even outside the framework of approved indications. Further studies are necessary to better define new indications for the drug.