Double-carbapenem combination as salvage therapy for untreatable infections by KPC-2-producing Klebsiella pneumoniae

Ertapenem plus meropenem combination treatment in carbapenem-resistant Klebsiella pneumoniae bacteremia: an analysis of 53 cases

Herein, we aimed to describe the outcomes of patients with blood stream infections due to carbapenem-resistant Klebsiella pneumoniae (CR-Kp) who received ertapenem plus meropenem combination treatment (EMCT). A total of 53 patients with culture proven CR-Kp bacteremia treated with ertapenem + meropenem were included. The patients with secondary bacteremia due to urinary tract infection exhibited a significantly lower 1-month mortality (OMM), particularly in those with microbiological eradication and those with end-of-treatment success. Salvage EMCT resulted in 49% 1-month survival.

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside

Sepsis is a life-threatening condition and a significant cause of preventable morbidity and mortality globally. Among the leading causative agents of sepsis are bacterial pathogens Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, along with fungal pathogens of the Candida species. Here, we focus on evidence from human studies but also include in vitro and in vivo cellular and molecular evidence, exploring how bacterial and fungal pathogens are associated with bloodstream infection and sepsis. This review presents a narrative update on pathogen epidemiology, virulence factors, host factors of susceptibility, mechanisms of immunomodulation, current therapies, antibiotic resistance, and opportunities for diagnosis, prognosis, and therapeutics, through the perspective of bloodstream infection and sepsis. A list of curated novel host and pathogen factors, diagnostic and prognostic markers, and potential therapeutical targets to tackle sepsis from the research laboratory is presented. Further, we discuss the complex nature of sepsis depending on the sepsis-inducing pathogen and host susceptibility, the more common strains associated with severe pathology and how these aspects may impact in the management of the clinical presentation of sepsis.

New advances in management and treatment of multidrug-resistant Klebsiella pneumoniae

INTRODUCTION

The management of multidrug-resistant (MDR) Klebsiella pneumoniae (KP) represents a major challenge in the field of infectious diseases. It is associated with a high rate of nosocomial infections with a mortality rate that reaches approximately 50%, even when using an effective antimicrobial therapy. Therefore, combined actions addressing infection control and antibiotic stewardship are required to delay the emergence of resistance. Since new antimicrobial agents targeting MDR-GNB bacteria have been produced during the last years and are now available for physicians to treat MDR, it is fundamental to choose appropriate antimicrobial therapy for K. pneumoniae infection.

AREAS COVERED

The PubMed database was searched to review the most significant recent literature on the topic, including data from articles coming from endemic areas and from the current European and American Guidelines.

EXPERT OPINION

We explore the most effective strategies for prevention of MDR-KP spread and the currently available treatment options, focusing on comparing old strategies and new compounds. We reviewed data concerning newly developed drugs that could play an important role in the future; we also propose a treatment algorithm that could be useful for physicians in daily clinical practice.

Current and Potential Therapeutic Options for Infections Caused by Difficult-to-Treat and Pandrug Resistant Gram-Negative Bacteria in Critically Ill Patients

Carbapenem resistance in Gram-negative bacteria has come into sight as a serious global threat. Carbapenem-resistant Gram-negative pathogens and their main representatives Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa are ranked in the highest priority category for new treatments. The worrisome phenomenon of the recent years is the presence of difficult-to-treat resistance (DTR) and pandrug-resistant (PDR) Gram-negative bacteria, characterized as non-susceptible to all conventional antimicrobial agents. DTR and PDR Gram-negative infections are linked with high mortality and associated with nosocomial infections, mainly in critically ill and ICU patients. Therapeutic options for infections caused by DTR and PDR Gram-negative organisms are extremely limited and are based on case reports and series. Herein, the current available knowledge regarding treatment of DTR and PDR infections is discussed. A focal point of the review focuses on salvage treatment, synergistic combinations (double and triple combinations), as well as increased exposure regimen adapted to the MIC of the pathogen. The most available data regarding novel antimicrobials, including novel β-lactam-β-lactamase inhibitor combinations, cefiderocol, and eravacycline as potential agents against DTR and PDR Gram-negative strains in critically ill patients are thoroughly presented.

In Vitro Activity of Single and Combined Antibiotics against Carbapenem Resistant Enterobacteriaceae Clinical Isolates in Relation to their Resistance Genes

Background: Mortality due to infection with carbapenem-resistant Enterobacteriaceae (CRE) is reported globally and carbapenemase production is the main mechanism of resistance in these isolates. The detection and treatment of carbapenemase-producing Enterobacteriaceae (CPE) is a major challenge in health care facilities. Objectives: The aim of the current study was to evaluate the in-vitro effect of different single and combined antibiotic agents against CRE clinical isolates. Methodology: Fifty CRE isolates were detected using disk diffusion test as a screening test. Species identification and antibiotic susceptibility testing was done using Vitek 2 system. Carbapenemase enzyme production was confirmed by Carba NP test. Multiplex PCR was done to detect carbapenem resistance genes. Antibiotics were tested in the form of single agents (colistin and tigecycline) and combined (tigecycline/ colistin, doripenem/ colistin and dual carbapenem therapy (ertapenem and doripenem) against CRE isolates using E-test method. Results: Most of the CRE isolates were K. pneumoniae, 68%, followed by E. coli, 22%, S. marcescens, 4%, E. cloacae, 4% and C. freundii, 2%. CPE was confirmed in 46 isolates by multiplex PCR; blaNDM-like was the main carbapenem resistance gene in (84%) of the isolates, followed by blaOXA-48-like (6%) and blaKPC-like (2%). Carba NP test detected 90% of CPE isolates. Single use of colistin and tigecycline showed 100% sensitivity against all tested CRE isolates except in blaNDM-like (83%).  Combination of colistin/tigecycline showed synergetic activity in 18% of CRE that was correlated to their carbapenemase R genes showing a significant increase in blaOXA-48-like and blaKPC-like positive isolates (100%) compared to blaNDM-like (7%). Other combinations showed indifferent effect whereas antagonism was not detected in any of the tested combinations. Conclusions: blaNDM-like is the main carbapenemase-producing gene detected among our CPE isolates followed by blaOXA-48-like. Colistin and tigecycline are still effective when used as single agents, and may offer effective treatment options when used in combination for CRE infections. Characterization of carbapenemases is crucial in determining treatment options. There is urgent demand for the development of novel therapeutic agents against NDM-producing CPE isolates.

Modelling of the transmission dynamics of carbapenem-resistant Klebsiella pneumoniae in hospitals and design of control strategies

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as a major threat to global public health. Epidemiological and infection controls associated with CRKP are challenging because of several potential elements involved in a complicated cycle of transmission. Here, we proposed a comprehensive mathematical model to investigate the transmission dynamics of CRKP, determine factors affecting the prevalence, and evaluate the impact of interventions on transmission. The model includes the essential compartments, which are uncolonized, asymptomatic colonized, symptomatic colonized, and relapsed patients. Additionally, symptomatic colonized and relapsed patients were further classified into subpopulations according to their number of treatment failures or relapses. We found that the admission of colonized patients and use of antibiotics significantly impacted the endemic transmission in health care units. Thus, we introduced the treatment efficacy, defined by combining the treatment duration and probability of successful treatment, to characterize and describe the effects of antibiotic treatment on transmission. We showed that a high antibiotic treatment efficacy results in a significantly reduced likelihood of patient readmission in the health care unit. Additionally, our findings demonstrate that CRKP transmission with different epidemiological characteristics must be controlled using distinct interventions.

Effectiveness of a Double-Carbapenem combinations against carbapenem-resistant Gram-negative bacteria

The emergence of carbapenem-resistant organisms posed considerable threat to global health while only limited treatment options are available and led to efforts to discover a novel way to treat them. To evaluate in vitro synergistic activity of meropenem plus ertapenem, a total of 203 carbapenem-resistant strains, collected from 12 provinces and municipalities in China, were examined with a dual carbapenem combination therapy. The statistical software R was used for analysis. Two hundred and one (201) of carbapenem-resistant strains mainly produced four types of carbapenemase: KPC-2 (n = 142, 69.95%), OXA-232 (n = 7, 3.45%), NDM (n = 38, 18.72%; 36 NDM-1, 1 NDM-4, 1 NDM-5), and IMP (n = 15, 7.39%; 1 IMP-26, 10 IMP-30, 4 IMP-4). Fifty-one out of two hundred and three (51/203 or 25.12%) of the examined strains showed a synergistic effect for the meropenem plus ertapenem combination throughout the checkerboard method, while only three isolates showed potential clinically relevant synergy (3/203, 1.48%). An additive effect was observed in 55/203 (27.09%) of the examined strains. Ninety-seven of the examined isolates (47.78%) showed fractional inhibitory concentration (FIC) greater or equal to 2 (indicating antagonism). The synergistic activity of meropenem plus ertapenem combination suggests this combination can be a possible way to treat the infection caused by the carbapenem-resistant organisms, especially for IMP or NDM producer with a lesser minimum inhibitory concentration (MIC) and the infected individual who was not recommended to use colistin or tigecycline.

Evaluation of the Therapeutic Outcomes of Antibiotic Regimen Against Carbapenemase-Producing Klebsiella pneumoniae: A Systematic Review and Meta-Analysis

Background: Carbapenemase-producing Klebsiella pneumoniae (CpKP) has been implicated as an increasing threat to public health. CpKP is a ubiquitous, opportunistic pathogen that causes both hospital and community acquired infections. This organism hydrolyzes carbapenems and other β-lactams and thus, leading to multiple resistance to these antibiotics. Despite the difficult to treat nature of infections caused by CpKP, little has been discussed on the mortality, clinical response and microbiological success rates associated with various antibiotic regimen against CpKP. This meta-analysis was designed to fill the paucity of information on the clinical impact of various antibiotic therapeutic regimens among patients infected with CpKP.

Materials and Methods: Literature in most English databases such as Medline through PubMed, Google Scholar, Web of Science, Cochrane Library and EMBASE, were searched for most studies published between the years 2015–2020. Data were analyzed using the R studio 2.15.2 statistical software program (metaphor and meta Package, Version 2) by random-effects (DerSimonian and Laird) model.

Results: Twenty-one (21) studies including 2841 patients who had been infected with CpKP were analysed. The overall mortality rate was 32.2% (95%CI = 26.23–38.87; I² = 89%; p-value ≤ 0.01, Number of patients = 2716). Pooled clinical and microbiological success rates were 67.6% (95%CI = 58.35–75.64, I² = 22%, p-value = 0.25, Number of patients = 171) and 74.9% (95%CI = 59.02–86.09, I² = 53%, p-value = 0.05, Number of patients = 121), respectively. CpKP infected patients treated with combination therapy are less likely to die as compared to those treated with monotherapy (OR = 0.55, 95%CI = 0.35–0.87, p-value = 0.01, Number of patients = 1,475). No significant difference existed between the mortality rate among 60years and above patients vs below 60years (OR = 0.84, 95%CI = 0.28–2.57, p-value = 0.76, 6 studies, Number of patients = 1,688), and among patients treated with triple therapy vs. double therapy (OR = 0.50, 95%CI = 0.21–1.22, p-value = 0.13, 2 studies, Number of patients = 102). When compared with aminoglycoside-sparing therapies, aminoglycoside-containing therapies had positive significant outcomes on both mortality and microbiological success rates.

Conclusion: New effective therapies are urgently needed to help fight infections caused by this organism. The effective use of various therapeutic options and the strict implementation of infection control measures are of utmost importance in order to prevent infections caused by CpKP. Strict national or international implementation of infection control measures and treatment guidelines will help improve healthcare, and equip governments and communities to respond to and prevent the spread of infectious diseases caused by CpKP.

Treatment of Donor-derived Carbapenem-resistant Klebsiella pneumoniae Infection after Renal Transplantation with Tigecycline and Extended-infusion Meropenem

OBJECTIVE

Donor-derived carbapenem-resistant Klebsiella pneumoniae (CRKP) infection has recently emerged as a critical early complication after renal transplantation. Although CRKP is usually sensitive to tigecycline, monotherapy with this drug is often less than effective. We investigated the efficacy of a combined regimen of tigecycline with high-dose, extended-infusion meropenem in the treatment of donor-derived CRKP infection after kidney transplantation.

METHODS

From Jan. 2016 to Dec. 2017, a total of 12 CRKP isolates were detected from cultures of the organ preservation solution used for soaking the donor kidneys at our institute. Probable or possible donor-derived infection (DDI) was identified in 8 transplant recipients. Clinical data were retrospectively analyzed.

RESULTS

Klebsiella pneumoniae carbapenemase-2 (KPC-2)-producing CRKP was reported to be positive in organ preservation solution cultures at 3.5±0.9 days after transplantation, leading to surgical site (n=3), urinary tract (n=4), and/or bloodstream (n=2) infections in 8 recipients. The drug susceptibility tests showed that CRKP was sensitive to tigecycline, but resistant to meropenem. In 7 patients who received tigecycline combined with high-dose extended-infusion meropenem, DDIs were successfully cured. The length of hospital stay was 31 (18-129) days, and the serum creatinine at discharge was 105.8±16.7 µmol/L. The one remaining patient who received tigecycline combined with intravenous-drip meropenem died of septic shock. A median follow-up of 43 months (33-55) showed no recurrence of new CRKP infection in the 7 surviving recipients.

CONCLUSION

It was suggested that a prompt and appropriate combination therapy using tigecycline with high-dose extended-infusion meropenem is effective in treating donor-derived KPC-2-producing CRKP infection after renal transplantation.

Escalating antimicrobial resistance among Enterobacteriaceae: focus on carbapenemases

Introduction: Over the past few decades, antimicrobial resistance (AMR) has skyrocketed globally among bacteria within the Family Enterobacteriaceae (i.e. Enterobacter spp, Klebsiella spp, Escherichia coli, Proteus spp, Serratia marcescens, Citrobacter spp, and others). Enterobacteriaceae are intestinal flora and are important pathogens in nosocomial and community settings. Enterobacteriaceae spread easily between humans and may acquire AMR via plasmids or other mobile resistance elements. The emergence and spread of multidrug resistant (MDR) clones have greatly limited therapeutic options. Some infections are untreatable with existing antimicrobials.Areas covered: The authors discuss the escalation of CRE globally, the epidemiology and outcomes of CRE infections, the optimal therapy, and the potential role of several new antimicrobials to combat MDR organisms. An exhaustive search for literature related to Enterobacteriaceae was performed using PubMed, using the following key words: antimicrobial resistance; carbapenemases; Enterobacterales; Enterobacteriaceae; Klebsiella pneumoniae; Escherichia coli; global epidemiology; metallo-β-lactamases; multidrug resistance; New Delhi Metalloproteinase-1 (NDM-1); plasmidsExpert opinion: Innovation and development of new classes of antibacterial agents are critical to expand effective therapeutic options. The authors encourage the judicious use of antibiotics and aggressive infection-control measures are essential to minimize the spread of AMR.

Ceftazidime-Avibactam in Combination with In Vitro Non-susceptible Antimicrobials Versus Ceftazidime-Avibactam in Monotherapy in Critically Ill Patients with Carbapenem-Resistant Klebsiella Pneumoniae Infection: A Retrospective Cohort Study

BACKGROUND

No clinical study has investigated the use of ceftazidime-avibactam combination schemes with an in vitro non-susceptible antimicrobial that could be superior to ceftazidime-avibactam monotherapy against carbapenem-resistant Klebsiella pneumoniae.

METHODS

We performed a retrospective cohort study at two tertiary hospitals in China for patients with carbapenem-resistant Klebsiella pneumoniae infection treated with ceftazidime-avibactam for at least 72 h. A Cox proportional hazards regression model was used to evaluate covariates that potentially affected 30-day mortality.

RESULTS

Sixty-two patients were eligible for our study; 41 (66.1%) received ceftazidime-avibactam combination therapy and 21 (33.9%) received ceftazidime-avibactam monotherapy. The overall 30-day mortality was 33.9% (21 patients): 24.4% (10/41) and 47.6% (11/21), P = 0.028, in combination and monotherapy groups, respectively. Combination therapy was significantly associated with lower 30-day mortality (Hazard ratio, 0.167; 95% Confidence Interval, 0.060-0.465, P = 0.001). At the same time, a higher APACHE II score, use of vasoactive drugs and comorbidity of organ transplantation were considered factors that increased mortality. The propensity score showed no significant alterations with other variables after adding it to the final model. In the subgroup analysis, the protective effect was revealed when combined with carbapenems, tigecycline or fosfomycin were applied, and in the following subgroups of patients: with sepsis, with creatinine clearance > 50 mL/min, stayed in the intensive care unit ≤ 30 days or underwent mechanical ventilation.

CONCLUSIONS

Ceftazidime-avibactam combined with another in vitro non-susceptible antimicrobial, especially carbapenems, fosfomycin and tigecycline, could significantly decrease the 30-day mortality rate for critically ill patients with carbapenem-resistant Klebsiella pneumoniae infection. Further investigation should be carried out to confirm this conclusion and identify autofit antimicrobials in ceftazidime-avibactam combination schemes.

Pandrug-resistant Gram-negative bacteria: a systematic review of current epidemiology, prognosis and treatment options

BACKGROUND

The literature on the epidemiology, mortality and treatment of pandrug-resistant (PDR) Gram-negative bacteria (GNB) is scarce, scattered and controversial.

OBJECTIVES

To consolidate the relevant literature and identify treatment options for PDR GNB infections.

METHODS

A systematic search in MEDLINE, Scopus and clinical trial registries was conducted. Studies reporting PDR clinical isolates were eligible for review if susceptibility testing for all major antimicrobials had been performed. Characteristics and findings of retrieved studies were qualitatively synthesized.

RESULTS

Of 81 studies reviewed, 47 (58%) were published in the last 5 years. The reports reflected a worldwide dissemination of PDR GNB in 25 countries in 5 continents. Of 526 PDR isolates reported, Pseudomonas aeruginosa (n=175), Acinetobacter baumannii (n=172) and Klebsiella pneumoniae (n=125) were most common. PDR GNB were typically isolated in ICUs, but several studies demonstrated wider outbreak potential, including dissemination to long-term care facilities and international spread. All-cause mortality was high (range 20%-71%), but appeared to be substantially reduced in studies reporting treatment regimens active in vitro. No controlled trial has been performed to date, but several case reports and series noted successful use of various regimens, predominantly synergistic combinations, and in selected patients increased exposure regimens and newer antibiotics.

CONCLUSIONS

PDR GNB are increasingly being reported worldwide and are associated with high mortality. Several treatment regimens have been successfully used, of which synergistic combinations appear to be most promising and often the only available option. More pharmacokinetic/pharmacodynamic and outcome studies are needed to guide the use of synergistic combinations.

Investigation of double-carbapenem efficiency in experimental sepsis of colistin-resistant Klebsiella pneumoniae

OBJECTIVE:

Klebsiella pneumoniae, a Gram-negative pathogen, especially which produces carbapenemase, is seen as a major threat to public health due to rapid plasmid-mediated spread of resistance and limited therapeutic options available for treatment. Although colistin has been recognized as a “last resort” antimicrobial for multidrug-resistant K. pneumoniae infections, these isolates have developed resistance to colistin as a result of its intensive use. The aim of this study was to evaluate the efficacy of double-carbapenem treatment of colistin-resistant K. pneumoniae experimental sepsis in mice.

METHODS:

In the study, 8–10-week-old Balb-c mice were divided as control groups (positive and negative) and treatment groups (colistin, ertapenem+meropenem, and ertapenem+meropenem+colistin). Sepsis was developed in mice by an intraperitoneal injection of colistin resistant K. pneumoniae. Antibiotics were given intraperitoneally 3 h after bacterial inoculation. Mice in each subgroup were sacrificed with overdose anesthetic at the end of 24–48 h and cultures were made from the heart, lung, liver, and spleen. Furthermore, homogenates of lung and liver were used to detect the number of colony-forming units per gram. Bacterial clearance was evaluated in lung and liver at different time points.

RESULTS:

When the quantitative bacterial loads in the lung and liver tissues are evaluated, no statistically significant difference was observed between different antibiotic treatments (p>0.05). All three treatment options were not effective, especially in 24 h. Only the decrease in bacterial load at the 48^th h of the group treated with ertapenem + meropenem + colistin was found significant (p<0.05) compared to the 24 h.

CONCLUSION:

In the light of these data, it was understood that double-carbapenem application was not sufficient in the treatment of experimental sepsis in mice with colistin-resistant K. pneumoniae. Furthermore, ertapenem + meropenem + colistin combined therapy was not found to be superior to colistin monotherapy or double-carbapenem therapy.

Repurposing the anti-viral drug zidovudine (AZT) in combination with meropenem as an effective treatment for infections with multi-drug resistant, carbapenemase-producing strains of Klebsiella pneumoniae

Multi-drug resistant (MDR) Klebsiella pneumoniae represent a global threat to healthcare due to lack of effective treatments and high mortality rates. The aim of this research was to explore the potential of administering zidovudine (AZT) in combination with an existing antibiotic to treat resistant K. pneumoniae infections. Two MDR K. pneumoniae strains were employed, producing either the NDM-1 or KPC-3 carbapenemase. Efficacy of combinations of AZT with meropenem were compared with monotherapies against infections in Galleria mellonella larvae by measuring larval mortality and bacterial burden. The effect of the same combinations in vitro was determined via checkerboard and time-kill assays. In vitro, both K. pneumoniae strains were resistant to meropenem but were susceptible to AZT. In G. mellonella, treatment with either AZT or meropenem alone offered minimal therapeutic benefit against infections with either strain. In contrast, combination therapy of AZT with meropenem presented significantly enhanced efficacy compared to monotherapies. This was correlated with prevention of bacterial proliferation within the larvae but not elimination. Checkerboard assays showed that the interaction between AZT and meropenem was not synergistic but indifferent. In summary, combination therapy of AZT with meropenem represents a potential treatment for carbapenemase-producing MDR K. pneumoniae and merits further investigation.

In vitro synergy of β-lactam combinations against KPC-producing Klebsiella pneumoniae strains

BACKGROUND

Double carbapenem therapy has been promoted as an alternative treatment for infections due to carbapenemase-producing Enterobacteriaceae where carbapenemase inhibitors are unavailable or when other agents have demonstrated toxicity with equally limited evidence. The capacity of other β-lactams and β-lactamase inhibitors to provide synergistic activity with carbapenems is unclear.

OBJECTIVES

This study sought to investigate the in vitro synergistic potential of other β-lactam/β-lactamase combinations with meropenem against KPC producers.

METHODS

Time-kill assays were performed on 24 unique strains of KPC-producing Klebsiella pneumoniae. Combinations evaluated included meropenem or imipenem with one of the following: ertapenem, piperacillin/tazobactam or ceftolozane/tazobactam. Concentrations used for each drug were those considered physiologically attainable in patients with a time above the concentration exceeding 40%-50% of the dose interval. Combinations were considered to be synergistic when they reduced bacterial cfu/mL by ≥2 log10 at 24 h as compared with the single most active agent.

RESULTS

The combination of piperacillin/tazobactam with meropenem was found to be synergistic against 70.8% of the isolates, followed by ertapenem with meropenem (58.3%) and ceftolozane/tazobactam with meropenem (41.7%). The piperacillin/tazobactam combination was found to be more bactericidal than the other combinations, with 58.3% of isolates demonstrating a ≥4 log10 cfu/mL reduction at 24 h, as compared with 37.5% for ertapenem and 20.8% for ceftolozane/tazobactam combinations.

CONCLUSIONS

The combination of piperacillin/tazobactam with meropenem may be a potential therapy against KPC-producing K. pneumoniae when other therapies are unavailable or prohibitively toxic.

Treatment options for K. pneumoniae, P. aeruginosa and A. baumannii co-resistant to carbapenems, aminoglycosides, polymyxins and tigecycline: an approach based on the mechanisms of resistance to carbapenems

The management of carbapenem-resistant infections is often based on polymyxins, tigecycline, aminoglycosides and their combinations. However, in a recent systematic review, we found that Gram-negative bacteria (GNB) co-resistant to carbapanems, aminoglycosides, polymyxins and tigecycline (CAPT-resistant) are increasingly being reported worldwide. Clinical data to guide the treatment of CAPT-resistant GNB are scarce and based exclusively on few case reports and small case series, but seem to indicate that appropriate (in vitro active) antimicrobial regimens, including newer antibiotics and synergistic combinations, may be associated with lower mortality. In this review, we consolidate the available literature to inform clinicians dealing with CAPT-resistant GNB about treatment options by considering the mechanisms of resistance to carbapenems. In combination with rapid diagnostic methods that allow fast detection of carbapenemase production, the approach proposed in this review may guide a timely and targeted treatment of patients with infections by CAPT-resistant GNB. Specifically, we focus on the three most problematic species, namely Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii. Several treatment options are currently available for CAPT-resistant K. pneumonia. Newer β-lactam-β-lactamase combinations, including the combination of ceftazidime/avibactam with aztreonam against metallo-β-lactamase-producing isolates, appear to be more effective compared to combinations of older agents. Options for P. aeruginosa (especially metallo-β-lactamase-producing strains) and A. baumannii remain limited. Synergistic combination of older agents (e.g., polymyxin- or fosfomycin-based synergistic combinations) may represent a last resort option, but their use against CAPT-resistant GNB requires further study.

Double-carbapenem therapy in the treatment of multidrug resistant Gram-negative bacterial infections: a systematic review and meta-analysis

BACKGROUND

To compare the efficacy and safety of double-carbapenem therapy (DCT) with other antibiotics for the treatment of multidrug resistant (MDR) Gram-negative bacterial infections.

METHODS

Cochrane Library, PubMed, Embase and Web of Science as well as Chinese databases were searched from database establishment to February 2019. All types of studies were included if they had evaluated efficacy and safety of DCT regimens in patients with MDR Gram-negative bacterial infections. Clinical response, microbiological response, adverse events and mortality were the main outcomes. The protocol was registered with PROSPERO No. CRD42019129979.

RESULTS

Three cohort or case-control studies consisting of 235 patients and 18 case series or case reports consisting of 90 patients were included. The clinical and microbiological responses were similar between DCT and other regimens in patients with carbapenem-resistant Enterobacteriaceae (CRE) infection. DCT achieved a lower mortality than comparators in patients with CRE infection (OR = 0.44, 95% CI = 0.24-0.82, P = 0.009). Ertapenem was the most reported antibiotic in DCT regimens in case series or case reports. Moreover, clinical and microbiological improvements were found in 59 (65.6%) and 63 (70%) in total 90 cases, respectively.

CONCLUSIONS

DCT was as effective as other antibiotics in treating MDR Gram-negative bacterial infections, with similar efficacy response and lower mortality. DCT could be an alternative therapeutic option in the treatment of MDR Gram-negative bacterial infections. High-quality randomized controlled trials were required to confirm the beneficial effects of DCT.

Carbapenem-Resistant Enterobacterales: Considerations for Treatment in the Era of New Antimicrobials and Evolving Enzymology

Purpose of Review

Gram-negative resistance is a growing concern globally. Enterobacterales, formerly Enterobacteriaceae, have developed resistance mechanisms to carbapenems that leave very few antimicrobial options in the clinician’s armamentarium.

Recent Findings

New antimicrobials like ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, cefiderocol, and plazomicin have the potential to overcome resistance mechanisms in Enterobacterales including different classes of carbapenemases.

Summary

Novel β-lactam/β-lactamase inhibitors, plazomicin, and cefiderocol give the clinician options that were once not available. Utilizing these options is of the utmost importance when treating carbapenem-resistant Enterobacterales.

Mortality, clinical and microbiological response following antibiotic therapy among patients with carbapenem-resistant Klebsiella pneumoniae infections (a meta-analysis dataset)

This meta-analysis was conducted to assess mortality, clinical and microbiological response following antibiotic therapy among patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) infections. Fifty-four observational studies involving 3195 CRKP-infected patients who received antibiotic treatment were included. We found combination therapy to be associated with lower mortality than monotherapy, but no differences in clinical and microbiological response. Among the various combination therapies, no significant differences in mortality, clinical and microbiological response were found. Moreover, clinical outcomes did not differ significantly among various monotherapies. This report describes the data related to the article entitled: "A systematic review and meta-analysis of treatment outcomes following antibiotic therapy among patients with carbapenem-resistant Klebsiella pneumoniae infections".

Retrospective evaluation of the patients with urinary tract infections due to carbapenemase producing Enterobacteriaceae

In this study, we aimed to investigate retrospectively the patients with carbapenem-resistant Enterobacteriaceae urinary tract infections (UTIs) in the terms of demographic findings, antibiotic sensitivity patterns and clinical features along with the treatment options. This study was performed at a tertiary-care educational university hospital. Adult (>18 years old) patients diagnosed with culture proven UTI due to carbapenem-resistant Klebsiella pneumoniae (between December 2016 to December 2017) were included in the study. Antimicrobial susceptibility testing of the isolates was performed with the VITEK 2 system (bioMérieux). Resistance to imipenem, ertapenem, and meropenem was tested by E-test (bioMérieux). The results were interpreted according to the EUCAST criteria. A total number of 100 patients (34% female, mean age 61.69 ± 1.65 years) were included in this study. One month all-cause mortality rate was 19%. Microbiologic eradication rate was 88.7% while it was significantly higher in combination therapy (65/70 vs. 14/19, p = 0.019) and carbapenem long-lasting (4 h) infusion subgroups (54/56 vs. 2/56, p = 0.005). Relapse and reinfection rates were 61.7 and 29.7%, respectively. Logistic regression analysis for mortality risk factors resulted as history of ertapenem usage (OR: 4.74, 95% CI: 0.678-33.201, p = 0.117), lack of microbiologic eradication (OR: 21.7, 95% CI: 1.906-247.375, p = 0.013) and ICU stay (OR: 54.8, 95% CI: 4.145-726.324, p = 0.002). Combination, carbapenem long-lasting infusion and double carbapenem therapies seem to result in higher microbiologic eradication rates and thus may effect the mortality rates of these group of patients. Randomized-controlled studies should be performed in this critical patient group to confirm these results.

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.

Multidrug-resistant Gram-negative bacterial infections in solid organ transplant recipients-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of infections due to multidrug-resistant (MDR) Gram-negative bacilli in the pre- and post-transplant period. MDR Gram-negative bacilli, including carbapenem-resistant Enterobacteriaceae, MDR Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii, remain a threat to successful organ transplantation. Clinicians now have access to at least five novel agents with activity against some of these organisms, with others in the advanced stages of clinical development. No agent, however, provides universal and predictable activity against any of these pathogens, and very little is available to treat infections with MDR nonfermenting Gram-negative bacilli including A baumannii. Despite advances, empiric antibiotics should be tailored to local microbiology and targeted regimens should be tailored to susceptibilities. Source control remains an important part of the therapeutic armamentarium. Morbidity and mortality associated with infections due to MDR Gram-negative organisms remain unacceptably high. Heightened infection control and antimicrobial stewardship initiatives are needed to prevent these infections, curtail their transmission, and limit the evolution of MDR Gram-negative pathogens, especially in the setting of organ transplantation.

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.

Infections Caused by Carbapenem-Resistant Enterobacteriaceae: An Update on Therapeutic Options

Carbapenems are considered as last-resort antibiotics for the treatment of infections caused by multidrug-resistant Gram-negative bacteria. With the increasing use of carbapenems in clinical practice, the emergence of carbapenem-resistant pathogens now poses a great threat to human health. Currently, antibiotic options for the treatment of carbapenem-resistant Enterobacteriaceae (CRE) are very limited, with polymyxins, tigecycline, fosfomycin, and aminoglycosides as the mainstays of therapy. The need for new and effective anti-CRE therapies is urgent. Here, we describe the current understanding of issues related to CRE and review combination therapeutic strategies for CRE infections, including high-dose tigecycline, high-dose prolonged-infusion of carbapenem, and double carbapenem therapy. We also review the newly available antibiotics which have potential in the future treatment of CRE infections: ceftazidime/avibactam, which is active against KPC and OXA-48 producers; meropenem/vaborbactam, which is active against KPC producers; plazomicin, which is a next-generation aminoglycoside with in vitro activity against CRE; and eravacycline, which is a tetracycline class antibacterial with in vitro activity against CRE. Although direct evidence for CRE treatment is still lacking and the development of resistance is a concern, these new antibiotics provide additional therapeutic options for CRE infections. Finally, we review other potential anti-CRE antibiotics in development: imipenem/relebactam and cefiderocol. Currently, high-dose and combination strategies that may include the new β-lactam/β-lactamase inhibitors should be considered in severe CRE infections to maximize treatment success. In the future, when more treatment options are available, therapy for CRE infections should be individualized and based on molecular phenotypes of resistance, susceptibility profiles, disease severity, and patient characteristics. More high-quality studies are needed to guide effective treatment for infections caused by CRE.

The role of therapy with aminoglycoside in the outcomes of kidney transplant recipients infected with polymyxin- and carbapenem-resistant Enterobacteriaceae

Kidney transplant recipients are at risk for infections due to carbapenem-resistant Enterobacteriaceae (CRE). Polymyxin-resistant CRE (PR-CRE) infections are especially difficult to treat. The aim of this study was to characterize PR-CRE infections among kidney transplant recipients and identify risk factors for treatment failure. This retrospective cohort study involved all kidney transplant recipients with PR-CRE infection between 2013 and 2017 at our center. Minimal inhibitory concentrations for polymyxin B were determined by broth microdilution. Carbapenem-resistant genes (bla_KPC, bla_NDM, and bla_OXA-48), aminoglycoside-resistance genes, and polymyxin-resistant gene mcr-1 were identified by polymerase chain reaction. All but one of the 47PR-CRE infections identified were due to Klebsiella pneumoniae. The most common type of infection (in 54.3%) was urinary tract infection (UTI). Monotherapy was used in 10 cases. Combined treatment regimens included double-carbapenem therapy in 19 cases, oral fosfomycin in 19, and amikacin in 13. Treatment failure occurred in 21 cases (45.7%). Clinical success was achieved 78.9% of patients who used aminoglycosides versus 37.0% of those who not used this drug (p = 0.007). Multivariate analysis showed diabetes mellitus to be a risk factor for treatment failure; amikacin use and UTI were found to be protective. Nine strains were RmtB producers. Although aminoglycosides constitute an important therapeutic option for PR-CRE infection, the emergence of aminoglycoside resistance could have a major impact on the management of CRE infection.

Role of Double-Carbapenem Regimen in the Treatment of Infections due to Carbapenemase Producing Carbapenem-Resistant Enterobacteriaceae: A Single-Center, Observational Study

Purpose

(i) To compare infections caused by carbapenem-susceptible (CS) and carbapenemase producing carbapenem-resistant Enterobacteriaceae (CP-CRE); (ii) to evaluate the clinical effectiveness of the double-carbapenem (DC) regimen in comparison with the best available treatment (BAT) in infections caused by CP-CRE; and (iii) to determine the exact minimal inhibitory concentrations (MICs) of meropenem/ertapenem (MEM/ETP) and the degree of in vitro ETP+MEM synergism in subjects receiving the DC.

Methodology

Over a 3-year period (2014-2017), patients with infections due to Enterobacteriaceae were included in a single-center, retrospective, observational study. According to the susceptibility to carbapenems, subjects were divided into CSE and CP-CRE groups. CP-CRE group was further divided into subjects receiving the DC regimen and those treated with other regimens (BAT group). Clinical characteristics and the presence of 5^th-day response and 60-day outcome were evaluated for DC and BAT groups. The determination of MEM and ETP actual MICs and the MEM+ETP synergistic activity were performed on strains obtained from subjects receiving the DC regimen.

Results

A total of 128 patients were included in the study: 55/128 (43%) with infections due to CP-CRE and 73/128 (57%) with infections due to CSE. Among CP-CRE (n=55), 21 subjects (39%) were treated with the DC regimen whereas 34 (61%) received BAT. No differences in terms of severity of infection, presence/absence of concomitant bacteremia, type of infection, and resolution of infection were found; in contrast, DC group tended to have a higher rate of sepsis or septic shock at the onset of infection and a higher rate of 5^th-day response. MICs 50/90 were 256/512 and 256/256 μg/mL for MEM and ETP, respectively. Overall, complete in vitro synergism was found in 6/20 strains (30%).

Conclusion

The DC regimen is a valid and effective therapeutic option in patients with infections due to KPC producing CRE, including those with bacteremic infection and more severe clinical conditions. The clinical effectiveness is maintained even in the presence of extremely high MEM MICs.

Critical Review of Double-Carbapenem Therapy for the Treatment of Carbapenemase-Producing Klebsiella pneumoniae

OBJECTIVE

To review the clinical data on the effectiveness and safety of double carbapenem therapy (DCT) in patients infected with carbapenemase-producing Klebsiella pneumoniae (CP-Kp).

DATA SOURCES

A literature search was performed utilizing PubMed and EMBASE (from 1966 to May 2018); bibliographies of the retrieved articles were also searched.

STUDY SELECTION AND DATA EXTRACTION

Articles were included if they evaluated patients with infections caused by CP-Kp and were treated with DCT. Meeting abstracts, editorials, and animal and in vitro studies were excluded.

DATA SYNTHESIS

The search strategy revealed 8 case reports and 6 clinical studies (total of 171 patients) that evaluated the administration of ertapenem followed by prolonged infusions of meropenem or doripenem. Most patients were critically ill and commonly had infections in the blood, lungs, and urine. Clinical and microbiological success were reported in 70% of the patients and mortality in 24%. Adverse events, which included mostly seizures, sodium disorders, and gastrointestinal symptoms, were reported in 16 patients; none required interruption of treatment. Relevance to Patient Care and Clinical Practice: This review evaluated the clinical experience of DCT in the treatment of CP-Kp infections, based on case reports and clinical studies, for the potential role of DCT as a therapeutic option.

CONCLUSION

Despite the limited studies, current data suggest that DCT may be an effective and safe strategy to treat CP-Kp. However, large randomized controlled trials are necessary to clearly define the role of DCT.

Wagenlehner F, Zimmer KP, Chakraborty T. Treatment Options for Carbapenem- Resistant Gram-Negative Infections

BACKGROUND

Rates of colonization and infection with carbapenem-resistant Gram-negative pathogens are on the rise, particularly in southeastern European countries, and this is increasingly true in Germany as well. The organisms in question include enterobacteriaceae such as Klebsiella pneumoniae and Escherichia coli and non-fermenting bacteria such as Pseudomonas aeruginosa and Acinetobacter baumannii. As the carbapenems have been the gold standard to date for the systemic treatment of serious infections with Gram-negative bacteria, carbapenem resistance presents new and difficult challenges in therapeutic decision-making, particularly because of the high frequency of coresistance.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed and on other applicable literature.

RESULTS

Multiresistant Gram-negative (MRGN) pathogens are classified in Germany according to their resistance to four different classes of antibiotics; fluoroquinolones, piperacillin, third-generation cephalosporins, and carbapenems. Quadruple MRGN pathogens are resistant to all four groups, triple MRGN pathogens to three of them. There are a number of therapeutic alternatives to carbapenems that can be applied with the aid of sensitive microbiological and/or molecular genetic testing. The following antibiotics are often the only ones that can be used to treat quadruple MRGN pathogens: colistin, aminoglycosides, tigecycline, fosfomycin, ceftazidime/avibactam, and ceftolozan/tazobactam. Carbapenems, too, may still be an option in certain situations. There is also evidence that combinations of antibiotics against which the pathogen is resistant individually can some- times be a valid treatment option; these include combinations of colistin with one or two carbapenems.

CONCLUSION

The treatment of severe infection with carbapenem-resistant pathogens should be individualized and carried out in an interdisciplinary framework, in consideration of antibiotic pharmacokinetics and pharmacodynamics in each case. The treat- ment options are based on evidence from in vitro studies, retrospective studies, and case series, which must be interpreted with caution. Randomized clinical trials are needed to test each of the various combined approaches.

In vitro evaluation of double-carbapenem combinations against OXA-48-producing Klebsiella pneumoniae isolates using time-kill studies

Purpose. The aim of this study was to evaluate the in vitro activity of double-carbapenem combinations against OXA-48-producing Klebsiella pneumoniae clinical isolates.Methodology. Double combinations of ertapenem, meropenem and imipenem were evaluated for synergy and bactericidal activity using the time-kill methodology. All antibiotics were tested at 10 mg l^-1 and at a sub-inhibitory concentration of 0.5× minimum inhibitory concentration (MIC) for isolates with a carbapenem MIC≤8 mg l^-1. Synergy was defined as a ≥2log₁₀ colony-forming units (c.f.u.) ml^-1 decrease of viable colonies at 24 h compared to the most active carbapenem alone.Results. Ten distinct K. pneumoniae clinical isolates were tested. All carried bla _OXA-48 and bla _CTX-M-15, and exhibited an MIC range of 64-128, 4-32 and 1-32 mg l^-1 for ertapenem, meropenem and imipenem, respectively. Out of 48 isolate-combinations, synergy was observed in 9 (18.8 %) and cidal activity was observed in 13 (27.1 %). In vitro synergistic activity was noted for 5 out of 29 (17.2 %) ertapenem-, 6 out of 29 (20.7 %) meropenem- and 7 out of 38 (18.4 %) imipenem-containing combinations. No combination exhibited antagonism. Bactericidal activity was observed in 7 (24.1 %) ertapenem-, 8 (27.6 %) meropenem- and 11 (28.9 %) imipenem-containing combinations. Among the sub-inhibitory concentration combinations, three (15 %) ertapenem-, four (20 %) meropenem- and three (15 %) imipenem-containing ones showed synergistic interaction.Conclusion. Dual combinations of carbapenems, including those containing sub-inhibitory concentrations of antibiotics, were synergistic against multidrug-resistant (MDR) and extensively drug-resistant (XDR) K. pneumoniae isolates harbouring bla _OXA-48.

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.

Management of KPC-producing Klebsiella pneumoniae infections

BACKGROUND

Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) has become one of the most important contemporary pathogens, especially in endemic areas.

AIMS

To provide practical suggestion for physicians dealing with the management of KPC-KP infections in critically ill patients, based on expert opinions.

SOURCES

PubMed search for relevant publications related to the management of KPC-KP infections.

CONTENTS

A panel of experts developed a list of 12 questions to be addressed. In view of the current lack of high-level evidence, they were asked to provide answers on the bases of their knowledge and experience in the field. The panel identified several key aspects to be addressed when dealing with KPC-KP in critically ill patients (preventing colonization in the patient, preventing infection in the colonized patient and colonization of his or her contacts, reducing mortality in the infected patient by rapidly diagnosing the causative agent and promptly adopting the best therapeutic strategy) and provided related suggestions that were based on the available observational literature and the experience of panel members.

IMPLICATIONS

Diagnostic technologies could speed up the diagnosis of KPC-KP infections. Combination treatment should be preferred to monotherapy in cases of severe infections. For non-critically ill patients without severe infections, results from randomized clinical trials are needed for ultimately weighing benefits and costs of using combinations rather than monotherapy. Multifaceted infection control interventions are needed to decrease the rates of colonization and cross-transmission of KPC-KP.

Double carbapenem as a rescue strategy for the treatment of severe carbapenemase-producing Klebsiella pneumoniae infections: a two-center, matched case-control study

Background

Recent reports have suggested the efficacy of a double carbapenem (DC) combination, including ertapenem, for the treatment of carbapenem-resistant Klebsiella pneumoniae (CR-Kp) infections. We aimed to evaluate the clinical impact of such a regimen in critically ill patients.

Methods

This case–control (1:2), observational, two-center study involved critically ill adults with a microbiologically documented CR-Kp invasive infection treated with the DC regimen matched with those receiving a standard treatment (ST) (i.e., colistin, tigecycline, or gentamicin).

Results

The primary end point was 28-day mortality. Secondary outcomes were clinical cure, microbiological eradication, duration of mechanical ventilation and of vasopressors, and 90-day mortality. Forty-eight patients treated with DC were matched with 96 controls. Occurrence of septic shock at infection and high procalcitonin levels were significantly more frequent in patients receiving DC treatment (p < 0.01). The 28-day mortality was significantly higher in patients receiving ST compared with the DC group (47.9% vs 29.2%, p = 0.04). Similarly, clinical cure and microbiological eradication were significantly higher when DC was used in patients infected with CR-Kp strains resistant to colistin (13/20 (65%) vs 10/32 (31.3%), p = 0.03 and 11/19 (57.9%) vs 7/27 (25.9%), p = 0.04, respectively). In the logistic regression and multivariate Cox-regression models, the DC regimen was associated with a reduction in 28-day mortality (OR 0.33, 95% CI 0.13–0.87 and OR 0.43, 95% CI 0.23–0.79, respectively).

Conclusions

Improved 28-day mortality was associated with the DC regimen compared with ST for severe CR-Kp infections. A randomized trial is needed to confirm these observational results.

Trial registration

ClinicalTrials.gov NCT03094494. Registered 28 March 2017.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1769-z) contains supplementary material, which is available to authorized users.