Treatment of Bloodstream Infections Due to Gram-Negative Bacteria with Difficult-to-Treat Resistance

In vitro activity of cefiderocol against European Enterobacterales, including isolates resistant to meropenem and recentβ-lactam/β-lactamase inhibitor combinations

Carbapenem-resistant Enterobacterales represent a major health threat and have few approved therapeutic options. Enterobacterales isolates were collected from hospitalized inpatients from 49 sites in six European countries (1 January-31 December 2020) and underwent susceptibility testing to cefiderocol and β-lactam/β-lactamase inhibitor combinations. Meropenem-resistant (MIC >8 mg/L) and cefiderocol-susceptible isolates were analyzed by PCR, and cefiderocol-‍resistant isolates by whole-genome sequencing, to identify resistance mechanisms. Overall, 1,909 isolates (including 970 Klebsiella spp., 382 Escherichia coli, and 244 Enterobacter spp.) were collected, commonly from bloodstream infections (43.6%). Cefiderocol susceptibility was higher than approved β-lactam/β-lactamase inhibitor combinations and largely comparable to cefepime-taniborbactam and aztreonam-avibactam against all Enterobacterales (98.1% vs 78.1%-‍97.4% and 98.7%-99.1%, respectively) and Enterobacterales resistant to meropenem (n = 148, including 125 Klebsiella spp.; 87.8% vs 0%-71.6% and 93.2%-98.6%, respectively), β-lactam/β-lactamase inhibitor combinations (66.7%-‍92.1% vs 0%-‍88.1% and 66.7%-97.9%, respectively), and to both meropenem and β-‌lactam/β-lactamase inhibitor combinations (61.9%-65.9% vs 0%-‍20.5% and 76.2%-97.7%, respectively). Susceptibilities to approved and developmental β-lactam/β-lactamase inhibitor combinations against cefiderocol-resistant Enterobacterales (n = 37) were 10.8%-‍56.8% and 78.4%-94.6%, respectively. Most meropenem-resistant Enterobacterales harbored Klebsiella pneumoniae carbapenemase (110/148) genes, although metallo-β-lactamase (35/148) and oxacillinase (OXA) carbapenemase (6/148) genes were less common; cefiderocol susceptibility was retained in β-lactamase producers, other than NDM, AmpC, and non-carbapenemase OXA producers. Most cefiderocol-resistant Enterobacterales had multiple resistance mechanisms, including ≥1 iron uptake-related mutation (37/37), carbapenemase gene (33/37), and ftsI mutation (24/37). The susceptibility to cefiderocol was higher than approved β-lac‌tam/β-lactamase inhibitor combinations against European Enterobacterales, including meropenem- and β-lactam/β-lactamase inhibitor combination-resistant isolates.

IMPORTANCE

This study collected a notably large number of Enterobacterales isolates from Europe, including meropenem- and β-lactam/β-lactamase inhibitor combination-resistant isolates against which the in vitro activities of cefiderocol and developmental β-lactam/β-lactamase inhibitor combinations were directly compared for the first time. The MIC breakpoint for high-dose meropenem was used to define meropenem resistance, so isolates that would remain meropenem resistant with doses clinically available to patients were included in the data. Susceptibility to cefiderocol, as a single active compound, was high against Enterobacterales and was higher than or comparable to available β-lactam/β-lactamase inhibitor combinations. These results provide insights into the treatment options for infections due to Enterobacterales with resistant phenotypes. Early susceptibility testing of cefiderocol in parallel with β-lactam/β-lactamase inhibitor combinations will allow patients to receive the most appropriate treatment option(s) available in a timely manner. This is particularly important when options are more limited, such as against metallo-β-lactamase-producing Enterobacterales.

Activity of Aztreonam/Avibactam and Recently Approved β-Lactamase Inhibitor Combinations against Enterobacterales and Pseudomonas aeruginosa from Intensive Care Unit and Non-Intensive Care Unit Patients

We evaluated the activities of aztreonam/avibactam and recently approved β-lactamase inhibitor combinations (BLICs) to compare the antimicrobial susceptibility patterns of Enterobacterales and Pseudomonas aeruginosa isolated from intensive care unit (ICU) and non-ICU patients. Clinical isolates (1/patient) were consecutively collected from 72 United States medical centres in 2020-2022 and susceptibility tested by broth microdilution. The results for 5421 isolates from ICU patients were analysed and compared to those for 20,649 isolates from non-ICU patients. Isolates from ventilator-associated pneumonia patients were analysed separately. Aztreonam/avibactam inhibited 100.0%/>99.9% Enterobacterales and 100.0%/98.3% of carbapenem-resistant Enterobacterales (CRE) from ICU/non-ICU patients at ≤8 mg/L, respectively. The CRE susceptibility rates were 88.5%/82.9% for ceftazidime/avibactam, 82.1%/81.2% for meropenem/vaborbactam, and 78.2%/72.6% for imipenem/relebactam among ICU/non-ICU isolates. Among the P. aeruginosa isolates from ICU/non-ICU patients, the susceptibility rates were 96.3%/97.6% for ceftazidime/avibactam, 97.2/98.4% for ceftolozane/tazobactam, 97.1%/98.0% for imipenem/relebactam, 77.8%/84.6% for piperacillin/tazobactam, and 76.9%/85.8% for meropenem; aztreonam/avibactam inhibited 78.0%/81.9% of P. aeruginosa at ≤8 mg/L. In summary, lower susceptibility rates were observed among ICU than non-ICU isolates. Aztreonam/avibactam exhibited potent in vitro activity and broad-spectrum activity against Enterobacterales from ICU and non-ICU patients, including CRE and isolates non-susceptible to newer BLICs. Against P. aeruginosa, aztreonam/avibactam showed a spectrum of activity comparable to that of piperacillin/tazobactam, meropenem, and ceftazidime.

The Molecular Mouse System: A New Useful Tool for Guiding Antimicrobial Therapy in Critically Ill Septic Patients

Bloodstream infections (BSI) caused by multidrug-resistant (MDR) bacteria, pose a major threat for patients, especially for those who are immunosuppressed. Rapid pathogen detection and characterization from positive blood cultures are crucial in the management of patients with BSI to enable an adequate and timely antimicrobial therapy. This study aimed to investigate the potential role of the Molecular Mouse system, a new CE IVD molecular test designed to rapidly detect the causative agents of bacteremia and their resistance determinants, in the management of the therapy in critically ill patients. Agreement between the results of the Molecular Mouse and the conventional routine method was also considered. Overall, 100 positive blood cultures were collected from septic critically ill patients from May 2023 to January 2024 and analyzed with Molecular Mouse and routine protocols. The new instrument consistently agreed with the routine protocols in the case of monomicrobial blood cultures, while some discrepancies were obtained in the polymicrobial samples. Antimicrobial resistance genes were detected in 35 samples, with vanA and CTX-M-1/9 groups being the most frequently detected targets. Therapy was adjusted in 42 critically ill patients confirming the importance of new rapid molecular tests in the management of positive blood cultures, to adjust empirical therapy and use new antibiotics accurately.

In vitro development of resistance against antipseudomonal agents: comparison of novel β-lactam/β-lactamase inhibitor combinations and other β-lactam agents

We subjected seven P. aeruginosa isolates to a 10-day serial passaging against five antipseudomonal agents to evaluate resistance levels post-exposure and putative resistance mechanisms in terminal mutants were analyzed by whole-genome sequencing analysis. Meropenem (mean, 38-fold increase), cefepime (14.4-fold), and piperacillin-tazobactam (52.9-fold) terminal mutants displayed high minimum inhibitory concentration (MIC) values compared to those obtained after exposure to ceftolozane-tazobactam (11.4-fold) and ceftazidime-avibactam (5.7-fold). Fewer isolates developed elevated MIC values for other β-lactams and agents belonging to other classes when exposed to meropenem in comparison to other agents. Alterations in nalC and nalD, involved in the upregulation of the efflux pump system MexAB-OprM, were common and observed more frequently in isolates exposed to ceftazidime-avibactam and meropenem. These alterations, along with ones in mexR and amrR, provided resistance to most β-lactams and levofloxacin but not imipenem. The second most common gene altered was mpl, which is involved in the recycling of the cell wall peptidoglycan. These alterations were mainly noted in isolates exposed to ceftolozane-tazobactam and piperacillin-tazobactam but also in one cefepime-exposed isolate. Alterations in other genes known to be involved in β-lactam resistance (ftsI, oprD, phoP, pepA, and cplA) and multiple genes involved in lipopolysaccharide biosynthesis were also present. The data generated here suggest that there is a difference in the mechanisms selected for high-level resistance between newer β-lactam/β-lactamase inhibitor combinations and older agents. Nevertheless, the isolates exposed to all agents displayed elevated MIC values for other β-lactams (except imipenem) and quinolones tested mainly due to alterations in the MexAB-OprM regulators that extrude these agents.

In vitro activity of antibiotics potentially effective against difficult-to-treat strains of Gram-negative rods: retrospective study

Bacterial resistance surveillance is one of the main outputs of microbiological laboratories and its results are important part of antimicrobial stewardship (AMS). In this study, the susceptibility of specific bacteria to selected antimicrobial agents was tested. The susceptibility of 90 unique isolates of pathogens of critical priority obtained from clinically valid samples of ICU patients in 2017-2021 was tested. 50% of these fulfilled difficult-to-treat resistance (DTR) criteria and 50% were susceptible to all antibiotics included in the definition. 10 Enterobacterales strains met DTR criteria, and 2 (20%) were resistant to colistin (COL), 2 (20%) to cefiderocol (FCR), 7 (70%) to imipenem/cilastatin/relebactam (I/R), 3 (30%) to ceftazidime/avibactam (CAT) and 5 (50%) to fosfomycin (FOS). For Enterobacterales we also tested aztreonam/avibactam (AZA) for which there are no breakpoints yet. The highest MIC of AZA observed was 1 mg/l, MIC range in the susceptible cohort was 0.032-0.064 mg/l and in the DTR cohort (incl. class B beta-lactamase producers) it was 0.064-1 mg/l. Two (13.3%) isolates of Pseudomonas aeruginosa (15 DTR strains) were resistant to COL, 1 (6.7%) to FCR, 13 (86.7%) to I/R, 5 (33.3%) to CAT, and 5 (33.3%) to ceftolozane/tazobactam. All isolates of Acinetobacter baumannii with DTR were susceptible to COL and FCR, and at the same time resistant to I/R and ampicillin/sulbactam. New antimicrobial agents are not 100% effective against DTR. Therefore, it is necessary to perform susceptibility testing of these antibiotics, use the data for surveillance (including local surveillance) and conform to AMS standards.

Antibiotic therapy for nonfermenting Gram-negative bacilli infections: future perspectives

PURPOSE OF REVIEW

Serious infections caused by nonfermenting Gram-negative bacteria (NF-GNB) pose a significant challenge for clinicians due to the limited treatment options available, which are frequently associated with issues of toxicity and unfavourable pharmacokinetic profiles. The aim of this review is to provide a brief overview of the existing data concerning the ongoing development of antiinfective agents targeting NF-GNB.

RECENT FINDINGS

Several agents exhibiting efficacy against NF-GNB are under clinical investigation. Durlobactam-sulbactam and cefepime-taniborbactam emerge as promising therapeutic avenues against carbapenem-resistant Acinetobacter baumanii . Cefepime-zidebactam may serve as a suitable treatment option for urinary tract infections caused by a wide range of NF-GNB. Cefepime-enmetazobactam demonstrates potent in vitro activity against various NF-GNB strains; however, its role as an anti- Pseudomonal agent is inadequately substantiated by available data. Xeruborbactam is a wide β-lactamase inhibitor that can be associated with a range of agents, enhancing in-vitro activity of these against many NF-GNB, including those resistant to newer, broader spectrum options. Lastly, murepavadin appears to be a potential pathogen-specific solution for severe Pseudomonas infections; however, additional investigation is necessary to establish the safety profile of this compound.

SUMMARY

Each of the novel molecules reviewed possesses an interesting range of in-vitro activity against NF-GNB. In addition, some of them have already been proved effective in vivo, underscoring their potential as future treatment options.

Analyses of Extended-Spectrum-β-Lactamase, Metallo-β-Lactamase, and AmpC-β-Lactamase Producing Enterobacteriaceae from the Dairy Value Chain in India

The consumption of milk contaminated with antibiotic-resistant bacteria poses a significant health threat to humans. This study aimed to investigate the prevalence of Enterobacteriaceae producing β-lactamases (ESBL, MBL, and AmpC) in cow and buffalo milk samples from two Indian states, Haryana and Assam. A total of 401 milk samples were collected from dairy farmers and vendors in the specified districts. Microbiological assays, antibiotic susceptibility testing, and PCR-based genotyping were employed to analyze 421 Gram-negative bacterial isolates. The overall prevalence of β-lactamase genes was 10% (confidence interval (CI) (7-13)), with higher rates in Haryana (13%, CI (9-19)) compared to Assam (7%, CI (4-11)). The identified β-lactamase genes in isolates were blaCMY, blaMOX, blaFOX, blaEBC, and blaDHA, associated with AmpC production. Additionally, blaCTX-M1, blaSHV, and blaTEM were detected as ESBL producers, while blaVIM, blaIMP, blaSPM, blaSIM, and blaGIM were identified as MBL producers. Notably, Shigella spp. were the dominant β-lactamase producers among identified Enterobacteriaceae. This study highlights the presence of various prevalent β-lactamase genes in milk isolates, indicating the potential risk of antimicrobial-resistant bacteria in dairy products. The presence of β-lactam resistance raises concern as this could restrict antibiotic options for treatment. The discordance between genotypic and phenotypic methods emphasizes the necessity for comprehensive approaches that integrate both techniques to accurately assess antibiotic resistance. Urgent collaborative action incorporating rational and regulated use of antibiotics across the dairy value chain is required to address the global challenge of β-lactam resistance.

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.

Difficult-to-treat resistant gram-negative blood stream infections - the beginning of a superbug era - a prospective observational study

INTRODUCTION

Carbapenem resistant gram-negative bacterial infections are a growing concern worldwide. However, India is already in the era of a shortage of effective antibiotics for the management of these infections. Moreover, Difficult-to-Treat Resistance (DTR) gram-negative infections, which are not much studied, further complicate the scenario. This study emphasized the incidence and outcomes of DTR infections.

METHODOLOGY

This is a single-center prospective observational study. The study included hospitalised patients aged ≥18 years with gram-negative bacterial bloodstream infections (GNBSI). Blood cultures with the growth of contaminants and/or single positive culture taken from the femoral site were excluded. Incidences of DTR infections and outcomes in the form of 30-day mortality were analysed.

RESULTS

Two hundred forty patients with GNBSI episodes were recorded. The Incidence of DTR GNBSI was 37.9% (91/240). Multivariate analysis found that Hospital-acquired infections, ICU admission and mechanical ventilation were independent risk factors for DTR GNBSI. The most common DTR GNB isolates were Klebsiella pneumoniae (31/49, 63.3%) and Acinetobacter baumannii (26/52, 50%). The adjusted relative risk of mortality was remarkably high in DTR GNBSI (aRR 3.9; 95% CI 1.9-7.9) as compared to CR+/DTR- GNBSI (aRR 0.3; 95% CI 0.1-1.0) and ESCR/CS GNBSI (aRR 1.1; 95% CI 0.5-2.4).

CONCLUSION

DTR GNB infections are growing concern in India and this need to be evaluated in multicentric studies. Moreover, DTR GNBSI was associated with significantly higher mortality and there is need of further empowerment of antibiotic stewardship practices.

Impact of Persistent Multidrug-Resistant Gram-Negative Bacteremia on Clinical Outcome and Mortality

The clinical aspects of persistent bacteremia (PB) caused by gram-negative rods (GNRs) in terms of antimicrobial resistance (AMR) and PB clearance status are unclear. This secondary analysis of a retrospective cohort study investigated differences in PB caused by Enterobacterales and glucose non-fermentative GNRs (NF-GNRs) based on AMR and PB clearance. We retrospectively surveyed medical records at Tohoku University Hospital. Patients for whom blood cultures were performed between January 2012 and December 2021 were recruited. PB cases were grouped based on AMR and PB clearance; the characteristics of PB due to each bacterial pathogen were examined. The main outcome variable was mortality. The late (30-90-day) mortality rate was significantly higher in the multidrug-resistant (MDR) group than in the non-MDR group for Enterobacterales. However, no significant difference was noted in mortality rates between NF-GNRs with and without AMR. Mortality rates tended to be higher in the non-PB-clearance group than in the clearance group for both Enterobacterales and NF-GNRs. Since the mortality rate was higher in the MDR group in the case of Enterobacterales PB, more careful management is necessary for this condition. Follow-up blood cultures and confirming the clearance of PB are useful for improving the survival rate.

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.

Intravenous Fosfomycin: A Potential Good Partner for Cefiderocol. Clinical Experience and Considerations

Multidrug resistant Gram-negative bacteremia represents a therapeutic challenge clinicians have to deal with. This concern becomes more difficult when causing germs are represented by carbapenem resistant Acinetobacter baumannii or difficult-to-treat Pseudomonas aeruginosa. Few antibiotics are available against these cumbersome bacteria, although literature data are not conclusive, especially for Acinetobacter. Cefiderocol could represent a valid antibiotic choice, being a molecule with an innovative mechanism of action capable of overcoming common resistance pathways, whereas intravenous fosfomycin may be an appropriate partner either enhancing cefiderocol activity or avoiding resistance development. Here we report two patients with MDR Gram negative bacteremia who were successfully treated with a cefiderocol/fosfomycin combination.

New antibiotics for Gram-negative pneumonia

Pneumonia is frequently encountered in clinical practice, and Gram-negative bacilli constitute a significant proportion of its aetiology, especially when it is acquired in a hospital setting. With the alarming global rise in multidrug resistance in Gram-negative bacilli, antibiotic therapy for treating patients with pneumonia is challenging and must be guided by in vitro susceptibility results. In this review, we provide an overview of antibiotics newly approved for the treatment of pneumonia caused by Gram-negative bacilli. Ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam have potent activity against some of the carbapenem-resistant Enterobacterales, especially Klebsiella pneumoniae carbapenemase producers. Several novel antibiotics have potent activity against multidrug-resistant Pseudomonas aeruginosa, such as ceftazidime-avibactam, ceftolozane-tazobactam, imipenem-relabactam and cefiderocol. Cefiderocol may also play an important role in the management of pneumonia caused by Acinetobacter baumannii, along with plazomicin and eravacycline.

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').

Epidemiology, Mechanisms of Resistance and Treatment Algorithm for Infections Due to Carbapenem-Resistant Gram-Negative Bacteria: An Expert Panel Opinion

Antimicrobial resistance represents a serious threat for global health, causing an unacceptable burden in terms of morbidity, mortality and healthcare costs. In particular, in 2017, carbapenem-resistant organisms were listed by the WHO among the group of pathogens for which novel treatment strategies are urgently needed. Fortunately, several drugs and combinations have been introduced in recent years to treat multi-drug-resistant (MDR) bacteria. However, a correct use of these molecules is needed to preserve their efficacy. In the present paper, we will provide an overview on the epidemiology and mechanisms of resistance of the most common MDR Gram-negative bacteria, proposing a treatment algorithm for the management of infections due to carbapenem-resistant bacteria based on the most recent clinical evidence.

Early appropriate diagnostics and treatment of MDR Gram-negative infections

The term difficult-to-treat resistance has been recently coined to identify Gram-negative bacteria exhibiting resistance to all fluoroquinolones and all β-lactam categories, including carbapenems. Such bacteria are posing serious challenges to clinicians trying to identify the best therapeutic option for any given patient. Delayed appropriate therapy has been associated with worse outcomes including increase in length of stay, increase in total in-hospital costs and ∼20% increase in the risk of in-hospital mortality. In addition, time to appropriate antibiotic therapy has been shown to be an independent predictor of 30 day mortality in patients with resistant organisms. Improving and anticipating aetiological diagnosis through optimizing not only the identification of phenotypic resistance to antibiotic classes/agents, but also the identification of specific resistance mechanisms, would have a major impact on reducing the frequency and duration of inappropriate early antibiotic therapy. In light of these considerations, the present paper reviews the increasing need for rapid diagnosis of bacterial infections and efficient laboratory workflows to confirm diagnoses and facilitate prompt de-escalation to targeted therapy, in line with antimicrobial stewardship principles. Rapid diagnostic tests currently available and future perspectives for their use are discussed. Early appropriate diagnostics and treatment of MDR Gram-negative infections require a multidisciplinary approach that includes multiple different diagnostic methods and further consensus of algorithms, protocols and guidelines to select the optimal antibiotic therapy.

The Effect of Different Colistin Dosing Regimens on Nephrotoxicity: A Cohort Study

(1) Background: It is not known whether different daily dosing schemes have different effects on colistin nephrotoxicity. We examined the effect of once- versus twice- or thrice-daily doses of colistin on renal function. (2) Methods: We performed a multicenter retrospective cohort study of hospitalized patients with a baseline glomerular filtration rate ≥ 50 mL/min who received intravenously the same colistin dose once (regimen A), twice (regimen B) or thrice daily (regimen C). The primary endpoint was acute kidney injury (AKI), defined as fulfilment of any of the RIFLE (Risk-Injury-Failure-Loss-End stage renal disease) criteria. (3) Results: We included 306 patients; 132 (43.1%) received regimen A, 151 (49.3%) regimen B, and 23 (7.5%) regimen C. Ninety-nine (32.4%) patients developed AKI; there was no difference between regimen A vs. B and C [45 (34.1%) vs. 54 (31.0%), p = 0.57]. In a propensity score−matched cohort, AKI was similar in patients receiving Regimen A, Regimen B, and Regimen C (31.6% vs. 33.3%, p = 0.78). On logistic regression analysis, diabetes was an independent predictor of AKI (OR = 4.59, 95% CI 2.03−10.39, p = 0.001) while eGFR > 80 mL/min (OR = 0.50, 95% CI 0.25−0.99, p = 0.048) was inversely associated with AKI. (4) Conclusions: Colistin once daily is not more nephrotoxic than the standard colistin regimens. The only independent predictor of nephrotoxicity was diabetes mellitus, while eGFR > 80 mL/min had a protective effect.

Bacteriological Profile and Antimicrobial Susceptibility Patterns of Gram-Negative Bloodstream Infection and Risk Factors Associated with Mortality and Drug Resistance: A Retrospective Study from Shanxi, China

Objective

The aim of this study was to analyze the epidemiological of gram-negative bloodstream infection (GNBSI) and establish a risk prediction model for mortality and acquiring multidrug resistant (MDR), the extended spectrum beta-lactamases (ESBLs) producing and carbapenem-resistant (CR) GNBSI.

Methods

This retrospective study covered five years from January 2015 to December 2019. Data were obtained from Hospital Information System (HIS) and microbiology department records. The risk factors for mortality and acquiring MDR, ESBLs-producing and CR GNBSI were analyzed by univariable and multivariable analysis.

Results

A total of 1018 GNBSI cases were collected. A majority of GNBSI patients were in hematology ward (23.77%). There were 38.61% patients who were assigned in the 41–60 age group. Escherichia coli was the most common gram-negative organism (49.90%). Among isolates of GNBSI, 40.47% were found to be MDR strains, 34.09% were found to be ESBLs-producing strains and 7.06% were found to be CR strains. Escherichia coli was the most common MDR (71.36%) and ESBLs-producing strain (77.81%). Acinetobacter baumannii was the most common CR isolate (46.15%). Multivariate analysis indicated that diabetes mellitus, solid organ tumor, non-fermentative bacteria, MDR strain, central venous cannula, urinary catheter, therapy with carbapenems or tigecycline prior 30 days of infection were independent mortality risk factors for GNBSIs. Over all, therapy with tigecycline prior 30 days of infection was the mutual predictor for mortality of GNBSI, acquiring MDR, ESBLs-producing and CR GNBSI (OR, 8.221, OR, 3.963, OR, 3.588, OR, 9.222, respectively, all p < 0.001).

Conclusion

Collectively, our study implies that patients who were diagnosed as GNBSI had a younger age. Therapy with tigecycline was the mutual and paramount predictor for mortality of GNBSI, acquiring MDR, ESBLs-producing and CR GNBSI. Our investigation had provided a theoretical basis for the use of antibiotics and prevention and control of hospital infection in our region.

Prevalence of colistin resistance of Klebsiella pneumoniae isolates in Iran: a systematic review and meta-analysis

Objective

Klebsiella pneumoniae is a gram-negative pathogen common cause of nosocomial infections. Colistin is a last resort antibiotic to treat infections caused by K. pneumoniae. In recent years, the resistance rate to colistin has increased in K. pneumoniae. This study evaluated the prevalence of colistin resistance of K. pneumoniae isolates in Iran using a systematic review and meta-analysis.

Method

A systematic search was performed for relevant articles until August 2021 in the following database: PubMed, Scopus, SID and Google Scholar. The pooled prevalence of colistin resistance in clinical K. pneumoniae isolates analyzed using Comprehensive Meta-Analysis Software (CMA).

Results

Finally, 19 articles with appropriate criteria were included in the meta-analysis. Our results showed 6.9% of the pooled prevalence of colistin resistance in clinical K. pneumoniae isolates in Iran. The results of subgroup analysis demonstrated increase resistance of colistin from 4.8%; (95% CI 1.5–13.9%) in 2013–2018 to 8.2%; (95% CI 3.4–18.6%), in 2019–2021. Also, the results of our study showed a strong association between the carbapenem producing K. pneumoniae and increased resistance to colistin.

Conclusions

This study showed a high prevalence of colistin resistance in K. pneumoniae isolates. It is recommended that regular evaluation be performed to control colistin resistance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-022-00520-8.

Pseudomonas aeruginosa Infections in Cancer Patients

Pseudomonas aeruginosa (P. aeruginosa) is one of the most frequent opportunistic microorganisms causing infections in oncological patients, especially those with neutropenia. Through its ability to adapt to difficult environmental conditions and high intrinsic resistance to antibiotics, it successfully adapts and survives in the hospital environment, causing sporadic infections and outbreaks. It produces a variety of virulence factors that damage host cells, evade host immune responses, and permit colonization and infections of hospitalized patients, who usually develop blood stream, respiratory, urinary tract and skin infections. The wide intrinsic and the increasing acquired resistance of P. aeruginosa to antibiotics make the treatment of infections caused by this microorganism a growing challenge. Although novel antibiotics expand the arsenal of antipseudomonal drugs, they do not show activity against all strains, e.g., MBL (metalo-β-lactamase) producers. Moreover, resistance to novel antibiotics has already emerged. Consequently, preventive methods such as limiting the transmission of resistant strains, active surveillance screening for MDR (multidrug-resistant) strains colonization, microbiological diagnostics, antimicrobial stewardship and antibiotic prophylaxis are of particular importance in cancer patients. Unfortunately, surveillance screening in the case of P. aeruginosa is not highly effective, and a fluoroquinolone prophylaxis in the era of increasing resistance to antibiotics is controversial.

Trends in DTR, CR, ECR, and FQR in Four Common Gram-Negative Bacteria: A Retrospective Study from 2013 to 2021

Purpose

The purpose of this study was to examine the prevalence of four important drug-resistance phenotypes: difficult-to-treat resistance (DTR), fluoroquinolone resistance (FQR), carbapenem resistance (CR), and extended-spectrum cephalosporin resistance (ECR).

Methods

DTR was defined as insensitivity to all the β-lactams and fluoroquinolones tested. We retrospectively analyzed the distribution characteristics of specific drug-resistant phenotypes of the main Gram-negative bacteria causing bloodstream infections (BSIs) in Tongji Hospital (Wuhan, China) between 2013 and 2021: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii.

Results

FQR was the main antimicrobial resistance phenotype of E. coli, accounting for 59.45% (1117/1879, 95% confidence interval, 57.21%-61.65%); the detection rates for CR and DTR were low, accounting for 1.86% (35/1879, 1.34%-2.58%), and 1.81% (34/1879, 1.30%-2.52%), respectively. However, the detection rates for CR and DTR in K. pneumoniae were 38.83% (497/1280, 36.20%-41.53%) and 35.94% (460/1280, 33.35%-38.60%), respectively. In P. aeruginosa, the detection rates of the four drug-resistant phenotypes (DTR, CR, FQR, and ECR) were all < 30%, but conversely, for A. baumannii, the detection rates were all > 80%. The changes in the data from 2013 to 2021 showed upward trends (z > 0) for CR-E. coli, DTR-E. coli, FQR-E. coli, CR-K. pneumoniae, DTR-K. pneumoniae, FQR-K. pneumoniae, and ECR-K. pneumoniae, but downward trends (z < 0) for ECR-E. coli, CR-A. baumannii, DTR-A. baumannii, FQR-A. baumannii, ECR-A. baumannii, CR-P. aeruginosa, DTR-P. aeruginosa, FQR-P. aeruginosa, and ECR-P. aeruginosa.

Conclusion

DTR warrants further attention, especially in in BSI-associated K. pneumoniae and A. baumannii, in which the detection rates were very high. Between 2013 and 2021 in this region, DTR-E. coli and CR-E. coli showed obvious upward trends, whereas DTR-P. aeruginosa and ECR-P. aeruginosa showed obvious downward trends.

Molecular mechanism underlying the TLR4 antagonistic and antiseptic activities of papiliocin, an insect innate immune response molecule

Similar to mammalian TLR4/MD-2, the Toll9/MD-2–like protein complex in the silkworm, Bombyx mori, acts as an innate pattern-recognition receptor that recognizes lipopolysaccharide (LPS) and induces LPS-stimulated expression of antimicrobial peptides such as cecropins. Here, we report that papiliocin, a cecropin-like insect antimicrobial peptide from the swallowtail butterfly, competitively inhibits the LPS-TLR4/MD-2 interaction by directly binding to human TLR4/MD-2. Structural elements in papiliocin, which are important in inhibiting TLR4 signaling via direct binding, are highly conserved among insect cecropins, indicating that its TLR4-antagonistic activity may be related to insect Toll9-mediated immune response against microbial infection. This study highlights the potential of papiliocin as a potent TLR4 antagonist and safe peptide antibiotic for treating gram-negative sepsis.

Antimicrobial peptides are innate immune molecules playing essential roles in insects, which lack the adaptive immune system. Insects possess Toll9, the innate pattern-recognition receptor highly similar to the mammalian Toll-like receptor 4 (TLR4), which is involved in recognizing lipopolysaccharide (LPS). TLR4 is an important therapeutic target, as it causes uncontrolled immune response in sepsis; therefore, identification of TLR4-targeting molecules is imperative. Papiliocin, an insect cecropin derived from the larvae of the swallowtail butterfly, possesses potent antibacterial activities against gram-negative bacteria. We investigated the molecular mechanism underlying the TLR4-antagonistic and antiseptic activities of papiliocin. Binding analysis, docking simulation, and flow cytometry showed that papiliocin inhibited LPS-induced TLR4 signaling by directly binding to TLR4/MD-2 and causing rapid dissociation of LPS from the TLR4/MD-2 complex. R13 and R16 in the N-terminal helix, conserved in insect cecropins, were the key binding sites at the TLR4/MD-2 interface, along with the flexible hinge region, which promoted the interaction of the hydrophobic carboxyl-terminal helix with the MD-2 pocket to competitively inhibit the LPS–TLR4/MD-2 interaction. Papiliocin, an antiendotoxin molecule and TLR4 inhibitor, rescued the pathology of Escherichia coli–induced sepsis in mice more effectively and with lower nephrotoxicity compared to polymyxin B. Our results provide insight into the key structural components and mechanism underlying the TLR4-antagonistic activities of papiliocin, which is essential for the innate immune response of the insect against microbial infection. Papiliocin may be useful for developing a multifunctional alternative to polymyxin B for treating gram-negative sepsis.

Polymyxin B-Based Regimens for Patients Infected with Carbapenem-Resistant Gram-Negative Bacteria: Clinical and Microbiological Efficacy, Mortality, and Safety

Background

The increasing prevalence of carbapenem-resistant Gram-negative bacteria (CR-GNB) represents a global healthcare crisis. This study explored the efficacy and safety of Polymyxin B (PMB)-based regimens and factors influencing their effectiveness.

Methods

Patients with CR-GNB infections treated with PMB for more than three days were enrolled in this retrospective study from 1st June 2018 to 30th April 2020. Data were collected on patient characteristics, bacterial culture, and drug-sensitivity test results; anti-infection treatment regimens, particularly details of PMB use; and adverse drug reactions. Clinical and microbiological efficacy, mortality, and safety of PMB-based regimens in CR-GNB infected patients were evaluated. Univariate analysis and multivariate logistic regression analyses were used to assess factors influencing efficacy and mortality.

Results

A total of 373 CR-GNB strains were cultured from 268 patients. About 41.04% of patients used PMB loading dose of 1.01 (0.84–1.69) mg/kg. Maintenance dose was 0.85 (0.82–1.00) mg/kg q12h. The clinical efficacy rate was 36.57% (98/268), the total bacterial clearance rate of PMB was 39.42%, and the all-cause mortality rate was 33.96%. The adverse drug reaction rate was 19.58%, among which the incidence of renal toxicity was highest (8.21%). Multivariate logistic regression analysis showed that clinical efficacy, bacterial clearance rate, and all-cause mortality were associated with patient-related facts, including mechanical ventilation use, underlying diseases (such as respiratory disease), the type and site of CR-GNB infection, and PMB administration timing and loading dose.

Conclusion

PMB is a relatively safe and effective antibiotic drug for treatment of critically ill patients with CR-GNB infection; however, PMB use should be subject to guidelines recommendations for early administration, loading administration, and adequate administration, which could help to improve the clinical efficacy, microbiological efficacy, and mortality.

Outcomes with Cefiderocol Treatment in Patients with Bacteraemia Enrolled into Prospective Phase 2 and Phase 3 Randomised Clinical Studies

Introduction

A post hoc, descriptive analysis of three prospective, randomised, controlled clinical studies investigating cefiderocol in gram-negative bacterial infections was conducted to assess its efficacy in patients with baseline bacteraemia.

Methods

Data from APEKS-cUTI (NCT02321800), APEKS-NP (NCT03032380) and CREDIBLE-CR (NCT02714595) studies were assessed individually. Patients received cefiderocol 2g, q8h, for 7–14 days or comparators (imipenem/cilastatin [APEKS-cUTI], meropenem [APEKS-NP] or best available therapy [BAT; CREDIBLE-CR]). Bacteraemia and clinical outcomes were assessed at early assessment (EA), end of treatment (EOT) and test of cure (TOC) for patients in the intention-to-treat populations with baseline blood samples positive for aerobic gram-negative species. Eradication, persistence or recurrence of baseline blood pathogen was confirmed from follow-up blood cultures; in the absence of follow-up blood cultures, clinical response, administration of additional antibiotics and vital status were used to assess bacteraemia outcome.

Results

Of 885 patients randomised, 84 had bacteraemia and 89 (cefiderocol: 55, comparators: 34) gram-negative pathogens were isolated, namely Enterobacterales (n = 62) and non-fermenters (n = 27). At EA, on-therapy bacteraemia eradication rates in APEKS-cUTI, APEKS-NP and CREDIBLE-CR were 100% (19/19), 50.0% (4/8) and 72.0% (18/25) with cefiderocol. Corresponding rates for comparators were 77.8% (7/9), 100% (10/10) and 69.2% (9/13), respectively. Persistence in blood at EA was seen in six patients overall (cefiderocol: 3, comparators: 3); indeterminate responses were common (cefiderocol: 8, comparators: 3), usually due to lack of blood cultures. Clinical cure/improvement rates at EA in APEKS-cUTI, APEKS-NP and CREDIBLE-CR were 100% (19/19), 62.5% (5/8) and 64.0% (16/25) with cefiderocol. Corresponding rates for comparators were 77.8% (7/9), 90.0% (9/10) and 30.8% (4/13), respectively. Bacteraemia eradication rates with cefiderocol in APEKS-cUTI, APEKS-NP and CREDIBLE-CR were 89.5%, 37.5% and 60.0% at EOT and 78.9%, 12.5% and 44.0% at TOC.

Conclusion

This descriptive analysis suggests that cefiderocol may be a useful treatment option for gram-negative bacteraemia, including pathogens resistant to other antibiotics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-022-00598-9.

New Antibiotics for Hospital-Acquired Pneumonia and Ventilator-Associated Pneumonia

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) represent one of the most common hospital-acquired infections, carrying a significant morbidity and risk of mortality. Increasing antibiotic resistance among the common bacterial pathogens associated with HAP and VAP, especially Enterobacterales and nonfermenting gram-negative bacteria, has made the choice of empiric treatment of these infections increasingly challenging. Moreover, failure of initial empiric therapy to cover the causative agents associated with HAP and VAP has been associated with worse clinical outcomes. This review provides an overview of antibiotics newly approved or in development for the treatment of HAP and VAP. The approved antibiotics include ceftobiprole, ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, and cefiderocol. Their major advantages include their high activity against multidrug-resistant gram-negative pathogens.

Extended-Spectrum Beta-Lactamase-Producing and Carbapenem-Resistant Enterobacterales in Companion and Animal-Assisted Interventions Dogs

Animal-assisted interventions (AAIs) are being implemented in many countries for the beneficial effects they have on humans. Patients involved in AAI are often individuals at greater risk of acquiring infections, and these activities involve close contact between humans and animals, as is the case with humans living with a pet. The spread of multidrug-resistant Enterobacterales is a serious problem for human health; an integrated One Health strategy is imperative to combat this threat. Companion dogs can be a reservoir of multidrug-resistant pathogens, and animal-to-human transmission could occur during AAI sessions. The aim of this review was to collect the available data on the carriage of extended-spectrum beta-lactamase-producing and carbapenem-resistant Enterobacterales in companion dogs and in an AAI context. Several papers have generally addressed the issue of microbial transmission during AAIs. Studies on the intestinal carriage of extended-spectrum beta-lactamase and/or carbapenem-resistant Enterobacterales have mainly been conducted in companion animals while few data are available on the carriage in dogs participating in AAI sessions. This review aims to draw attention to the antibiotic resistance problem in a One Health context and to the importance of extending infection control measures to this human-animal interface, to keep the balance of benefits/risks for AAIs shifted towards the benefits of these activities.

Role of new antibiotics in extended-spectrum β-lactamase-, AmpC- infections

PURPOSE OF REVIEW

Extended-spectrum β-lactamases (ESBL)- and ampicillinase class C (AmpC)-producing Enterobacterales represent one of the major public threats of the current era. As a consequence, during the last decades there have been great efforts to develop new therapeutic agents against these microorganisms. The aim of this review is to summarize the clinical features associated with novel antibiotics with activity against ESBL- and AmpC-producing isolates.

RECENT FINDINGS

There a number of therapeutic agents with activity against ESBL and AmpC than have been introduced and approved over the past few years. Ceftazidime-avibactam and ceftolozane-tazobactam are both carbapenem sparing agents that appear interesting alternatives for treatment of serious Gram-negative infections. Other new β-lactams/ β-lactamase inhibitors (e.g. cefepime-enmetazobactam; ceftaroline fosamil-avibactam; aztreonam-avibactam and cefepime-zidebactam) as well as eravacycline, omadacycline, and plazomicin are also promising agents for treatment of ESBL- and AmpC- infections, but further clinical data are needed to establish their efficacy in comparison to carbapenems. The role of carbapenems/ β-lactamase inhibitors remains to be clarified.

SUMMARY

New therapeutic agents against ESBL- and AmpC-producing Enterobacterales have distinctive specificities and limitations that require further investigations. Future randomized clinical trials are required to define the best strategy for their use in patients with serious infections due to ESBL- and/or AmpC- infections.

Efficacy and appropriateness of novel antibiotics in response to antimicrobial-resistant Gram-negative bacteria in patients with sepsis in the ICU

INTRODUCTION

There is an ever-increasing range of antibiotic-resistant pathogens that have led to higher community-acquired infections, and substantial mortality rates in critically ill patients.

AREAS COVERED

We have critically appraised available evidence through a structured literature review, investigating effective empiric antibiotic administration and appropriateness on outcomes of critically ill patients with an increased risk of developing resistant pathogens. The use of new antibiotics should be determined based on relevant knowledge of their spectrum and properties to provide effective mode of action for critically ill patients.

EXPERT OPINION

Restricting severely ill patients access to new broad-spectrum empirical drugs is not the answer. Rather there should be a focus on identifying host response to infection to differentiate between colonization or contamination and true infection, and the sensitivity to antibiotics used in the intensive care unit (ICU).

Management relies on adequate antibiotic administration, the ability to monitor response, and facilitate the cessation of antibiotic treatment. The major determinant of patient success in a patient with a severe infection is the 'right' antibiotic or complementary course of treatment. As an overarching criterion, the following 3 appropriate "Ds" should be considered: Dosing, Duration and De-escalation to empirically assess the right antibiotic optimal antimicrobial selection.

Antimicrobial Activity of a Lipidated Temporin L Analogue against Carbapenemase-Producing Klebsiella pneumoniae Clinical Isolates

Over the years, the increasing acquisition of antibiotic resistance genes has led to the emergence of highly resistant bacterial strains and the loss of standard antibiotics' efficacy, including β-lactam/β-lactamase inhibitor combinations and the last line carbapenems. Klebsiella pneumoniae is considered one of the major exponents of a group of multidrug-resistant ESKAPE pathogens responsible for serious healthcare-associated infections. In this study, we proved the antimicrobial activity of two analogues of Temporin L against twenty carbapenemase-producing K. pneumoniae clinical isolates. According to the antibiotic susceptibility assay, all the K. pneumoniae strains were resistant to at least one other class of antibiotics, in addition to beta-lactams. Peptides 1B and C showed activity on all test strains, but the lipidated analogue C expressed the greater antimicrobial properties, with MIC values ranging from 6.25 to 25 µM. Furthermore, the peptide C showed bactericidal activity at MIC values. The results clearly highlight the great potential of antimicrobial peptides both as a new treatment option for difficult-to-treat infections and as a new strategy of drug-resistance control.

Antimicrobial susceptibility of Gram-negative bacteria from intensive care unit and non-intensive care unit patients from United States hospitals (2018-2020)

We evaluated the antimicrobial susceptibility of Gram-negative bacteria recovered from ICU patients in US hospitals and compared them to those from non-ICU patients from the same hospitals during the same period. Overall, 4,680 isolates from ICU patients and 16,263 isolates from non-ICU patients were collected from 70 US medical centers in 2018-2020 and susceptibility tested by the broth microdilution method. Ceftazidime-avibactam and ceftolozane-tazobactam were the most active agents against P. aeruginosa and retained activity against multidrug-resistant (MDR) and extensively drug-resistant (XDR) isolates. Minocycline and trimethoprim-sulfamethoxazole were very active against S. maltophilia, whereas most antimicrobial agents exhibited low susceptibility to A. baumannii. Ceftazidime-avibactam and meropenem-vaborbactam were the most active agents against Enterobacterales, and retained potent activity against ESBL producers, carbapenem-resistant Enterobacterales (CRE), MDR, and XDR isolates. In summary, antimicrobial susceptibility was generally lower and the occurrence of ESBL, CRE, MDR, and XDR phenotypes were clearly higher among ICU compared to non-ICU isolates.

Management of Infections Caused by Multidrug-resistant Gram-negative Pathogens: Recent Advances and Future Directions

During the last decades, the isolation of multidrug-resistant Gram-negative (MDR-GN) bacteria has dramatically increased worldwide and has been associated with significant delays in the administration of adequate antibiotic treatment, resulting in increased morbidity and mortality rates. Given specific challenges to effective therapy with old antibiotics, there is the need to establish adequate clinical and therapeutic recommendations for antibiotic treatment of MDR-GN pathogens. Herein, we will review risk factors for harbouring infections due to MDR-GN bacteria, proposing an algorithm for the choice of empirical treatment when a MDR-GN pathogen is suspected. In addition, we will report our recommendations regarding the first- and second-line treatment options for hospitalized patients with serious infections caused by extended-spectrum β-lactamases producing Enterobacterales, carbapenem-resistant Enterobacterales, MDR Pseudomonas aeruginosa and MDR Acinetobacter baumannii. Recommendations have been specially focused, for each pathogen, on bloodstream infections, nosocomial pneumonia, and urinary tract infections.

Review of Ceftazidime-Avibactam for the Treatment of Infections Caused by Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes a range of serious infections that are often challenging to treat, as this pathogen can express multiple resistance mechanisms, including multidrug-resistant (MDR) and extensively drug-resistant (XDR) phenotypes. Ceftazidime–avibactam is a combination antimicrobial agent comprising ceftazidime, a third-generation semisynthetic cephalosporin, and avibactam, a novel non-β-lactam β-lactamase inhibitor. This review explores the potential role of ceftazidime–avibactam for the treatment of P. aeruginosa infections. Ceftazidime–avibactam has good in vitro activity against P. aeruginosa relative to comparator β-lactam agents and fluoroquinolones, comparable to amikacin and ceftolozane–tazobactam. In Phase 3 clinical trials, ceftazidime–avibactam has generally demonstrated similar clinical and microbiological outcomes to comparators in patients with complicated intra-abdominal infections, complicated urinary tract infections or hospital-acquired/ventilator-associated pneumonia caused by P. aeruginosa. Although real-world data are limited, favourable outcomes with ceftazidime–avibactam treatment have been reported in some patients with MDR and XDR P. aeruginosa infections. Thus, ceftazidime–avibactam may have a potentially important role in the management of serious and complicated P. aeruginosa infections, including those caused by MDR and XDR strains.

Minireview on Novel Anti-infectious Treatment Options and Optimized Drug Regimens for Sepsis

Sepsis, a life-threatening organ dysfunction caused by a dysregulated response to infection is a major public health concern, as it is a leading cause of mortality and critical illness worldwide. Antibiotics are one of the cornerstones of the treatment of sepsis; administering appropriate antibiotics in a rapid fashion to obtain adequate drug concentrations at the site of the infection can improve survival of patients. Nevertheless, it is a challenge for clinicians to do so. Indeed, clinicians today are regularly confronted with infections due to very resistant pathogens, and standard dosage regimens of antibiotics often do not provide adequate antibiotic concentrations at the site of the infection. We provide a narrative minireview of different anti-infectious treatments currently available and suggestions on how to deliver optimized dosage regimens to septic patients. Particular emphasis will be made on newly available anti-infectious therapies.

Drugs in Context Editorial: Review of 2020 and what lies ahead in therapeutic interventions

The year 2020 was dominated by the COVID-19 pandemic, bringing with it unprecedented advancements in the fields of healthcare and therapeutic interventions as well as in vaccine and drug development. Nevertheless, several other advancements in various fields of medicine also deserve attention. Herein, the Senior Editors of Drugs in Context provide us with their expert opinion on the events of 2020 and what lies ahead in 2021.

Mortality of Pandrug-Resistant Klebsiella pneumoniae Bloodstream Infections in Critically Ill Patients: A Retrospective Cohort of 115 Episodes

BACKGROUND

The increased frequency of bacteraemias caused by pandrug-resistant Klebsiella pneumoniae (PDR-Kp) has significant implications. The aim of the present study was to identify predictors associated with mortality of PDR-Kp bacteraemias.

METHODS

Patients with monomicrobial bacteraemia due to PDR-Kp were included. K. pneumoniae was considered PDR if it showed resistance to all available groups of antibiotics. Primary outcome was 30-day mortality. Minimum inhibitory concentrations (MICs) of meropenem, tigecycline, fosfomycin, and ceftazidime/avibactam were determined by Etest, whereas for colistin, the broth microdilution method was applied. bla _KPC, bla _VIM, bla _NDM, and bla _OXA genes were detected by PCR.

RESULTS

Among 115 PDR-Kp bacteraemias, the majority of infections were primary bacteraemias (53; 46.1%), followed by catheter-related (35; 30.4%). All isolates were resistant to tested antimicrobials. bla _KPC was the most prevalent carbapenemase gene (98 isolates; 85.2%). Thirty-day mortality was 39.1%; among 51 patients with septic shock, 30-day mortality was 54.9%. Multivariate analysis identified the development of septic shock, Charlson comorbidity index, and bacteraemia other than primary or catheter-related as independent predictors of mortality, while a combination of at least three antimicrobials was identified as an independent predictor of survival.

CONCLUSIONS

Mortality of PDR-Kp bloodstream infections was high. Administration of at least three antimicrobials might be beneficial for infections in critically ill patients caused by such pathogens.

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

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