Efficacy of a Fosfomycin-Containing Regimen for Treatment of Severe Pneumonia Caused by Multidrug-Resistant Acinetobacter baumannii: A Prospective, Observational Study

Optimized fosfomycin regimens for treating carbapenem-resistant Acinetobacter baumannii in critically ill patients with varying degrees of renal function

Fosfomycin has been used to treat carbapenem-resistant Acinetobacter baumannii (CRAB) infections. However, there is insufficient information on dosage adjustment among critically ill patients with renal impairment. This study aims to evaluate the attainment of PK/PD targets for different dosage regimens of CRAB treatment in critically ill patients based on their renal function. Monte Carlo simulations were conducted to assess the probability of achieving time above the minimum inhibitory concentration (T > MIC) of 80% and 100% and to determine the cumulative fraction response (CFR) against institutional MICs. Our results demonstrated that administering fosfomycin 20-24 g/day to individuals with normal renal function (CrCl ≥60 mL/min) achieved the target at a MIC of ≤64 and ≤32 μg/mL during the first 24 h of treatment and at steady state, respectively. Notably, those with renal impairment achieved higher MIC values at a steady state despite dosage reduction. None of the regimens reached the target CFR. Our study suggested that administering fosfomycin at least 20 g/day to those with normal renal function provides sufficient exposure throughout the treatment course when the MIC value is ≤32 μg/mL. Less aggressive dosing regimens are advisable for patients with renal impairment. Additional clinical studies are necessary to verify our suggestions.

Combination therapy with IV fosfomycin for adult patients with serious Gram-negative infections: a review of the literature

Treatment of patients with serious infections due to resistant Gram-negative bacteria remains highly problematic and has prompted clinicians to use existing antimicrobial agents in innovative ways. One approach gaining increased therapeutic use is combination therapy with IV fosfomycin. This article reviews the preclinical pharmacokinetic/pharmacodynamic (PK/PD) infection model and clinical data surrounding the use of combination therapy with IV fosfomycin for the treatment of serious infections caused by resistant Gram-negative bacteria. Data from dynamic in vitro and animal infection model studies of highly resistant Enterobacterales and non-lactose fermenters are positive and suggest IV fosfomycin in combination with a β-lactam, polymyxin or aminoglycoside produces a synergistic effect that rivals or surpasses that of other aminoglycoside- or polymyxin-containing regimens. Clinical studies performed to date primarily have involved patients with pneumonia and/or bacteraemia due to Klebsiella pneumoniae, Pseudomonas aeruginosa or Acinetobacter baumannii. Overall, the observed success rates with fosfomycin combination regimens were consistent with those reported for other combination regimens commonly used to treat these patients. In studies in which direct treatment comparisons can be derived, the results suggest that patients who received fosfomycin combination therapy had similar or improved outcomes compared with other therapies and combinations, especially when it was used in combination with a β-lactam that (1) targets PBP-3 and (2) has exceptional stability in the presence of β-lactamases. Collectively, the data indicate that combination therapy with IV fosfomycin should be considered as a potential alternative to aminoglycoside or polymyxin combinations for patients with antibiotic-resistant Gram-negative infections when benefits outweigh risks.

The impact and risk factors for developing pneumogenic bacteremia in carbapenem-resistant Acinetobacter baumannii nosocomial pneumonia in the intensive care unit: A multicenter retrospective study

OBJECTIVES

This study analyzed the risk and impact of developing pneumogenic bacteremia in patients with CRAB nosocomial pneumonia in ICU.

METHODS

This is multicenter retrospective study. Clinical outcomes were compared between bacteremia and non-bacteremia group, and the risk factors for mortality and developing pneumogenic CRAB bacteremia were analyzed.

RESULTS

After patient recruitment, 164 cases were in the bacteremia group, and 519 cases were in the non-bacteremia group. The bacteremia group had 22.4 percentage of increase in-hospital mortality than the non-bacteremia group (68.3% vs 45.9%, P < 0.001). Multivariate analysis showed bacteremia was an independent risk factor for in-hospital mortality (aHR = 2.399, P < 0.001). A long time-interval between ICU admission and pneumonia onset was an independent risk factor for developing bacteremia (aOR = 1.040, P = < 0.001). Spearman's rank correlation analysis indicated a high correlation between the days from ICU admission to pneumonia onset and the days of ventilator use before pneumonia onset (correlation coefficient (ρ) = 0.777).

CONCLUSIONS

In patients with CRAB nosocomial pneumonia, bacteremia increased the in-hospital mortality, and a longer interval from ICU admission to pneumonia onset was an independent risk factor for developing bacteremia, which was highly associated with the use of mechanical ventilation.

Treatment of infections caused by carbapenem-resistant Acinetobacter baumannii

Patients with severe carbapenem-resistant Acinetobacter baumannii (CRAB) infections currently face significant treatment challenges. When patients display signs of infection and the clinical suspicion of CRAB infections is high, appropriate treatment should be immediately provided. However, current treatment plans and clinical data for CRAB are limited. Inherent and acquired resistance mechanisms, as well as host factors, significantly restrict options for empirical medication. Moreover, inappropriate drug coverage can have detrimental effects on patients. Most existing studies have limitations, such as a restricted sample size, and are predominantly observational or non-randomized, which report significant variability in patient infection severity and comorbidities. Therefore, a gold-standard therapy remains lacking. Current and future treatment options of infections due to CRAB were described in this review. The dose and considerable side effects restrict treatment options for polymyxins, and high doses of ampicillin-sulbactam or tigecycline appear to be the best option at the time of initial treatment. Moreover, new drugs such as durlobactam and cefiderocol have substantial therapeutic capabilities and may be effective salvage treatments. Bacteriophages and antimicrobial peptides may serve as alternative treatment options in the near future. The advantages of a combination antimicrobial regimen appear to predominate those of a single regimen. Despite its significant nephrotoxicity, colistin is considered a primary treatment and is often used in combination with antimicrobials, such as tigecycline, ampicillin-sulbactam, meropenem, or fosfomycin. The Infectious Diseases Society of America (IDSA) has deemed high-dose ampicillin-sulbactam, which is typically combined with high-dose tigecycline, polymyxin, and other antibacterial agents, the best option for treating serious CRAB infections. A rational combination of drug use and the exploration of new therapeutic drugs can alleviate or prevent the effects of CRAB infections, shorten hospital stays, and reduce patient mortality.

Understanding antimicrobial pharmacokinetics in critically ill patients to optimize antimicrobial therapy: A narrative review

Effective treatment of sepsis not only demands prompt administration of appropriate antimicrobials but also requires precise dosing to enhance the likelihood of patient survival. Adequate dosing refers to the administration of doses that yield therapeutic drug concentrations at the infection site. This ensures a favorable clinical and microbiological response while avoiding antibiotic-related toxicity. Therapeutic drug monitoring (TDM) is the recommended approach for attaining these goals. However, TDM is not universally available in all intensive care units (ICUs) and for all antimicrobial agents. In the absence of TDM, healthcare practitioners need to rely on several factors to make informed dosing decisions. These include the patient's clinical condition, causative pathogen, impact of organ dysfunction (requiring extracorporeal therapies), and physicochemical properties of the antimicrobials. In this context, the pharmacokinetics of antimicrobials vary considerably between different critically ill patients and within the same patient over the course of ICU stay. This variability underscores the need for individualized dosing. This review aimed to describe the main pathophysiological changes observed in critically ill patients and their impact on antimicrobial drug dosing decisions. It also aimed to provide essential practical recommendations that may aid clinicians in optimizing antimicrobial therapy among critically ill patients.

Current and novel therapies for management of Acinetobacter baumannii-associated pneumonia

Acinetobacter baumannii is a common pathogen associated with hospital-acquired pneumonia showing increased resistance to carbapenem and colistin antibiotics nowadays. Infections with A. baumannii cause high patient fatalities due to their capability to evade current antimicrobial therapies, emphasizing the urgency of developing viable therapeutics to treat A. baumannii-associated pneumonia. In this review, we explore current and novel therapeutic options for overcoming therapeutic failure when dealing with A. baumannii-associated pneumonia. Among them, antibiotic combination therapy administering several drugs simultaneously or alternately, is one promising approach for optimizing therapeutic success. However, it has been associated with inconsistent and inconclusive therapeutic outcomes across different studies. Therefore, it is critical to undertake additional clinical trials to ascertain the clinical effectiveness of different antibiotic combinations. We also discuss the prospective roles of novel antimicrobial therapies including antimicrobial peptides, bacteriophage-based therapy, repurposed drugs, naturally-occurring compounds, nanoparticle-based therapy, anti-virulence strategies, immunotherapy, photodynamic and sonodynamic therapy, for utilizing them as additional alternative therapy while tackling A. baumannii-associated pneumonia. Importantly, these innovative therapies further require pharmacokinetic and pharmacodynamic evaluation for safety, stability, immunogenicity, toxicity, and tolerability before they can be clinically approved as an alternative rescue therapy for A. baumannii-associated pulmonary infections.

Intravenous fosfomycin for treatment of severe infections caused by carbapenem-resistant Acinetobacter baumannii: A multi-centre clinical experience

BACKGROUND

Severe infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) have been reported increasingly over the past few years. Many in-vivo and in-vitro studies have suggested a possible role of intravenous fosfomycin for the treatment of CRAB infections.

METHODS

This multi-centre, retrospective study included patients treated with intravenous fosfomycin for severe infections caused by CRAB admitted consecutively to four hospitals in Italy from December 2017 to December 2022. The primary goal of the study was to evaluate the risk factors associated with 30-day mortality in the study population. A propensity score matched analysis was added to the model.

RESULTS

One hundred and two patients with severe infections caused by CRAB treated with an intravenous fosfomycin-containing regimen were enrolled in this study. Ventilator-associated pneumonia (VAP) was diagnosed in 59% of patients, primary bacteraemia in 22% of patients, and central-venous-catheter-related infection in 16% of patients. All patients were treated with a regimen containing intravenous fosfomycin, mainly in combination with cefiderocol (n=54), colistin (n=48) or ampicillin/sulbactam (n=18). Forty-eight (47%) patients died within 30 days. Fifty-eight (57%) patients experienced clinical therapeutic failure. Cox regression analysis showed that diabetes, primary bacteraemia and a colistin-containing regimen were independently associated with 30-day mortality, whereas adequate source control of infection, early 24-h active in-vitro therapy, and a cefiderocol-containing regimen were associated with survival. A colistin-based regimen, A. baumannii colonization and primary bacteraemia were independently associated with clinical failure. Conversely, adequate source control of infection, a cefiderocol-containing regimen, and early 24-h active in-vitro therapy were associated with clinical success.

CONCLUSIONS

Different antibiotic regimens containing fosfomycin in combination can be used for treatment of severe infections caused by CRAB.

Antibiotic Treatment of Carbapenem-Resistant Acinetobacter baumannii Infections in View of the Newly Developed β-Lactams: A Narrative Review of the Existing Evidence

It is estimated that antimicrobial resistance (AMR) is responsible for nearly 5 million human deaths worldwide each year and will reach 10 million by 2050. Carbapenem-resistant Acinetobacter baumannii (CRAB) infections represent the fourth-leading cause of death attributable to antimicrobial resistance globally, but a standardized therapy is still lacking. Among the antibiotics under consideration, Sulbactam/durlobactam seems to be the best candidate to replace current back-bone agents. Cefiderocol could play a pivotal role within combination therapy regimens. Due to toxicity and the pharmacokinetics/pharmacodynamics (PK/PD) limitations, colistin (or polymyxin B) should be used as an alternative agent (when no other options are available). Tigecycline (or minocycline) and fosfomycin could represent suitable partners for both NBLs. Randomized clinical trials (RCTs) are needed to better evaluate the role of NBLs in CRAB infection treatment and to compare the efficacy of tigecycline and fosfomycin as partner antibiotics. Synergism should be tested between NBLs and "old" drugs (rifampicin and trimethoprim/sulfamethoxazole). Huge efforts should be made to accelerate pre-clinical and clinical studies on safer polymyxin candidates with improved lung activity, as well as on the iv rifabutin formulation. In this narrative review, we focused the antibiotic treatment of CRAB infections in view of newly developed β-lactam agents (NBLs).

Treatment Strategies of Colistin Resistance Acinetobacter baumannii Infections

Acinetobacter baumannii has emerged as a pressing challenge in clinical practice, mainly due to the development of resistance to multiple antibiotics, including colistin, one of the last-resort treatments. This review highlights all the possible mechanisms of colistin resistance and the genetic basis contributing to this resistance, such as modifications to lipopolysaccharide or lipid A structures, alterations in outer membrane permeability via porins and heteroresistance. In light of this escalating threat, the review also evaluates available treatment options. The development of new antibiotics (cefiderocol, sulbactam/durlobactam) although not available everywhere, and the use of various combinations and synergistic drug combinations (including two or more of the following: a polymyxin, ampicillin/sulbactam, carbapenems, fosfomycin, tigecycline/minocycline, a rifamycin, and aminoglycosides) are discussed in the context of overcoming colistin resistance of A. baumannii infections. Although most studied combinations are polymyxin-based combinations, non-polymyxin-based combinations have been emerging as promising options. However, clinical data remain limited and continued investigation is essential to determine optimal therapeutic strategies against colistin-resistant A. baumannii.

Intravenous fosfomycin in combination regimens as a treatment option for difficult-to-treat infections due to multi-drug-resistant Gram-negative organisms: A real-life experience

AIM

To investigate the efficacy of intravenous (IV) fosfomycin as combination therapy for treatment of difficult-to-treat (DTT) acute and subacute infections with multi-drug-resistant (MDR) Gram-negative bacteria (GNB), and risk factors associated with 90-day mortality.

METHODS

A retrospective, observational, monocentric study enrolled patients treated with IV fosfomycin in combination regimens (≥72 h) for proven DTT-MDR-GNB infection. Multi-variate regression analysis identified independent risk factors for 90-day mortality. A propensity score for receiving fosfomycin was performed to control for confounding factors.

RESULTS

In total, 70 patients were included in this study: 54.3% had carbapenem-resistant isolates, 31.4% had ceftazidime/avibactam-resistant isolates and 28.6% had ceftolozane/tazobactam-resistant isolates. The main pathogens were Pseudomonas aeruginosa (57.1%) and Klebsiella pneumoniae (22.9%). The most prevalent infections were nosocomial pneumonia (42.9%), osteomyelitis (17.1%) and intra-abdominal infections. All-cause 30- and 90-day mortality were 15.7% and 31.4%, respectively (18.9% and 50% considering acute DTT-MDR-GNB infections alone). Relapse at 30 days occurred in 22.9% of cases (29% with emergence of fosfomycin resistance). Mortality at 90 days was independently associated with septic shock and ceftolozane/tazobactam resistance. The relationship between resistance to ceftolozane/tazobactam and 90-day mortality was confirmed to be significant after adjustment by propensity score analysis (hazard ratio 5.84, 95% confidence interval 1.65-20.68; P=0.006).

CONCLUSIONS

Fosfomycin seems to be a promising salvage, combination treatment in DTT-MDR-GNB infections. Resistance to ceftolozane/tazobactam seems to be independently associated with treatment failure. Randomized clinical trials focusing on pathogen and infection sites are needed urgently to demonstrate the superiority of fosfomycin in combination with other agents for the resolution of DTT-MDR-GNB infections.

Current Therapeutic Approaches for Multidrug-Resistant and Extensively Drug-Resistant Acinetobacter baumannii Infections

The treatment of Acinetobacter baumannii infections remains a challenge for physicians worldwide in the 21st century. The bacterium possesses a multitude of mechanisms to escape the human immune system. The consequences of A. baumannii infections on morbidity and mortality, as well on financial resources, remain dire. Furthermore, A. baumannii superinfections have also occurred during the COVID-19 pandemic. While prevention is important, the antibiotic armamentarium remains the most essential factor for the treatment of these infections. The main problem is the notorious resistance profile (including resistance to carbapenems and colistin) that this bacterium exhibits. While newer beta lactam/beta-lactamase inhibitors have entered clinical practice, with excellent results against various infections due to Enterobacteriaceae, their contribution against A. baumannii infections is almost absent. Hence, we have to resort to at least one of the following, sulbactam, polymyxins E or B, tigecycline or aminoglycosides, against multidrug-resistant (MDR) and extensively drug-resistant (XDR) A. baumannii infections. Furthermore, the notable addition of cefiderocol in the fight against A. baumannii infections represents a useful addition. We present herein the existing information from the last decade regarding therapeutic advances against MDR/XDR A. baumannii infections.

How to treat severe Acinetobacter baumannii infections

PURPOSE OF REVIEW

To update the management of severe Acinetobacter baumannii infections (ABI), particularly those caused by multi-resistant isolates.

RECENT FINDINGS

The in vitro activity of the various antimicrobial agents potentially helpful in treating ABI is highly variable and has progressively decreased for many of them, limiting current therapeutic options. The combination of more than one drug is still advisable in most circumstances. Ideally, two active first-line drugs should be used. Alternatively, a first-line and a second-line drug and, if this is not possible, two or more second-line drugs in combination. The emergence of new agents such as Cefiderocol, the combination of Sulbactam and Durlobactam, and the new Tetracyclines offer therapeutic options that need to be supported by clinical evidence.

SUMMARY

The apparent limitations in treating infections caused by this bacterium, the rapid development of resistance, and the serious underlying situation in most cases invite the search for alternatives to antibiotic treatment, the most promising of which seems to be bacteriophage therapy.

Bibliometric Analysis of Global Research Output on Antimicrobial Resistance among Pneumonia Pathogens (2013-2023)

Antimicrobial resistance (AMR) is a pressing global concern, posing significant challenges to the effective treatment of infections, including pneumonia. This bibliometric analysis aims to investigate the research output on AMR among pneumonia pathogens from 2013 to 2023. Data were extracted from the Web of Science Core Collection (WOS-CC) using an inclusive search strategy. The analysis included 152 relevant studies published in 99 different sources, involving 988 authors and yielding an average of 16.33 citations per document over the past decade. The findings reveal a notable increase in research on AMR among pneumonia pathogens, indicating a growing awareness of this critical issue. Collaborative studies were prevalent, with the majority of authors engaging in joint research efforts. Bradford's Law identified twelve core journals that were instrumental in disseminating research in this field, with "Medicine" emerging as the most prolific journal. The USA and China emerged as the leading contributors, while Germany displayed a strong inclination towards collaborative research. Intermountain Medical Center, Saitama Medical University, and Udice-French Research Universities were the most productive institutions, and Yayan J. and Rasche K. were the top authors. Furthermore, the analysis identified commonly encountered microorganisms such as Acinetobacter baumanii and Klebsiella pneumoniae in the context of AMR. Time-based analysis of keywords highlighted the significance of terms like "community-acquired pneumonia" and "ventilator-associated pneumonia". Overall, this comprehensive study sheds light on the global research landscape of AMR among pneumonia pathogens. The insights gained from this analysis are essential for guiding future research priorities and collaborative efforts to combat AMR effectively and improve treatment outcomes for pneumonia and related infections. As the frequency of reports concerning resistance among pneumonia pathogens, notably A. baumannii and K. pneumoniae, continues to rise, there is an immediate requirement for pharmaceutical manufacturers and healthcare providers to respond proactively and ready themselves for the forthcoming implications of this matter. It also underscores the importance of knowledge dissemination and evidence-based interventions to address this growing public health challenge. However, the study acknowledges the limitations associated with using a single publication database and encourages the inclusion of data from other sources in future research.

Guidelines for the diagnosis, treatment, prevention and control of infections caused by carbapenem-resistant gram-negative bacilli

The dissemination of carbapenem-resistant Gram-negative bacilli (CRGNB) is a global public health issue. CRGNB isolates are usually extensively drug-resistant or pandrug-resistant, resulting in limited antimicrobial treatment options and high mortality. A multidisciplinary guideline development group covering clinical infectious diseases, clinical microbiology, clinical pharmacology, infection control, and guideline methodology experts jointly developed the present clinical practice guidelines based on best available scientific evidence to address the clinical issues regarding laboratory testing, antimicrobial therapy, and prevention of CRGNB infections. This guideline focuses on carbapenem-resistant Enterobacteriales (CRE), carbapenem-resistant Acinetobacter baumannii (CRAB), and carbapenem-resistant Pseudomonas aeruginosa (CRPA). Sixteen clinical questions were proposed from the perspective of current clinical practice and translated into research questions using PICO (population, intervention, comparator, and outcomes) format to collect and synthesize relevant evidence to inform corresponding recommendations. The grading of recommendations, assessment, development and evaluation (GRADE) approach was used to evaluate the quality of evidence, benefit and risk profile of corresponding interventions and formulate recommendations or suggestions. Evidence extracted from systematic reviews and randomized controlled trials (RCTs) was considered preferentially for treatment-related clinical questions. Observational studies, non-controlled studies, and expert opinions were considered as supplementary evidence in the absence of RCTs. The strength of recommendations was classified as strong or conditional (weak). The evidence informing recommendations derives from studies worldwide, while the implementation suggestions combined the Chinese experience. The target audience of this guideline is clinician and related professionals involved in management of infectious diseases.

Efficacy of cefiderocol- vs colistin-containing regimen for treatment of bacteraemic ventilator-associated pneumonia caused by carbapenem-resistant Acinetobacter baumannii in patients with COVID-19

INTRODUCTION

Ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) in patients hospitalized in intensive care units (ICUs) is an important and challenging complication, including in patients with coronavirus disease 2019 (COVID-19). Considering the poor lung penetration of most antibiotics, including intravenous colistin due to the poor pharmacokinetics/pharmacodynamics at the infection site, the choice of the best antibiotic regimen is still being debated.

METHODS

This single-centre, observational study was conducted from March 2020 to August 2022, and included all patients hospitalized consecutively with VAP and concomitant bloodstream infection due to CRAB in the COVID-ICU. The main goal of the study was to evaluate risk factors associated with survival or death at 30 days from VAP onset. A propensity score for receiving therapy was added to the model.

RESULTS

During the study period, 73 patients who developed VAP and concomitant positive blood cultures caused by CRAB were enrolled in the COVID-ICU. Of these patients, 67 (91.7%) developed septic shock, 42 (57.5%) had died at 14 days and 59 (80.8%) had died at 30 days. Overall, 54 (74%) patients were treated with a colistin-containing regimen and 19 (26%) were treated with a cefiderocol-containing regimen. Cox regression analysis showed that chronic obstructive pulmonary disease and age were independently associated with 30-day mortality. Conversely, cefiderocol-containing regimens and cefiderocol + fosfomycin in combination were independently associated with 30-day survival, as confirmed by propensity score analysis.

CONCLUSIONS

This real-life study in patients with bacteraemic VAP caused by CRAB provides useful suggestions for clinicians, showing a possible benefit of cefiderocol and its association with fosfomycin.

Lights and Shadows of Sepsis Management: Challenges and Future Perspectives

The complex interaction between microorganisms, the host's immune response, and [...].

The Use of Intravenous Fosfomycin in Clinical Practice: A 5-Year Retrospective Study in a Tertiary Hospital in Italy

Fosfomycin in intravenous (IV) formulation has re-emerged as a valuable tool in the treatment of multi-drug resistant (MDR) and extensively drug-resistant (XDR) infections because of its broad spectrum of antibacterial action and pharmacokinetic characteristics. This retrospective study aimed to evaluate how fosfomycin was used in patients admitted to the Polyclinic of Palermo between January 2017 and July 2022. Clinical indications, therapeutic associations, clinical outcomes, and any side effects were analyzed. Intravenous fosfomycin was used in 343 patients, 63% male, with a mean age of 68 years (range 15-95). Urinary tract infections (UTIs) and hospital-acquired pneumonia (HAP) were the main indications for treatment (19% and 18% of the total cases, respectively), followed by skin and soft tissue infections and sepsis. IV fosfomycin was administered in combination with other antibacterial agents, the most common of which were ceftazidime/avibactam (35%), meropenem (17%), and colistin (14%). Nineteen patients received it as monotherapy for UTIs. About 66% had resolution of the infectious process with clinical remission (cure or discharge). Electrolyte disturbances occurred in 2.6% and gastrointestinal symptoms occurred in 2.9%. The data showed that IV fosfomycin is a safe and effective therapeutic option in the treatment of infections with multidrug-resistant microorganisms.

Evaluating the efficiency of a nomogram based on the data of neurosurgical intensive care unit patients to predict pulmonary infection of multidrug-resistant Acinetobacter baumannii

Background

Pulmonary infection caused by multidrug-resistant Acinetobacter baumannii (MDR-AB) is a common and serious complication after brain injury. There are no definitive methods for its prediction and it is usually accompanied by a poor prognosis. This study aimed to construct and evaluate a nomogram based on patient data from the neurosurgical intensive care unit (NSICU) to predict the probability of MDR-AB pulmonary infection.

Methods

In this study, we retrospectively collected patient clinical profiles, early laboratory test results, and doctors' prescriptions (66 variables). Univariate and backward stepwise regression analyses were used to screen the variables to identify predictors, and a nomogram was built in the primary cohort based on the results of a logistic regression model. Discriminatory validity, calibration validity, and clinical utility were evaluated using validation cohort 1 based on receiver operating characteristic curves, calibration curves, and decision curve analysis (DCA). For external validation based on predictors, we prospectively collected information from patients as validation cohort 2.

Results

Among 2115 patients admitted to the NSICU between December 1, 2019, and December 31, 2021, 217 were eligible for the study, including 102 patients with MDR-AB infections (102 cases) and 115 patients with other bacterial infections (115 cases). We randomly categorized the patients into the primary cohort (70%, N=152) and validation cohort 1 (30%, N=65). Validation cohort 2 consisted of 24 patients admitted to the NSICU between January 1, 2022, and March 31, 2022, whose clinical information was prospectively collected according to predictors. The nomogram, consisting of only six predictors (age, NSICU stay, Glasgow Coma Scale, meropenem, neutrophil to lymphocyte ratio, platelet to lymphocyte ratio), had significantly high sensitivity and specificity (primary cohort AUC=0.913, validation cohort 1 AUC=0.830, validation cohort 2 AUC=0.889) for early identification of infection and had great calibration (validation cohort 1,2 P=0.3801, 0.6274). DCA confirmed that the nomogram is clinically useful.

Conclusion

Our nomogram could help clinicians make early predictions regarding the onset of pulmonary infection caused by MDR-AB and implement targeted interventions.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Rifampicin Enhanced Carbapenem Activity with Improved Antibacterial Effects and Eradicates Established Acinetobacter baumannii Biofilms

Biofilm-mediated infections are critical to public health and a leading cause of resistance among pathogens, amounting to a prolonged hospital stay and increased mortality rate in the intensive care unit. In this study, the antibacterial and antibiofilm activities of rifampicin or carbapenem monotherapies were compared with rifampicin and carbapenem combination therapies against rifampicin-resistant and carbapenem-resistant Acinetobacter baumannii isolates. Among 29 CRAB isolates, 24/29 (83%) were resistant to rifampicin, with MIC values between 2-256 µg/mL. Checkerboard assays disclosed that combination therapies at FICIs between 1/8 and 1/4 improved the activity of carbapenems at subinhibitory concentrations. Time-kill kinetics indicated a 2- to 4-log reduction at 1/2 MIC rifampicin + 1/4 MIC carbapenem and 1/4 MIC rifampicin + 1/4 MIC carbapenem against the isolates, with the MIC values ranging from 2-8 µg/mL. The MTT assay revealed a dose-dependent decrease of the cell viability of established bacterial biofilm at 4 MIC rifampicin + 2 MIC carbapenems, with a percentage reduction of 44-75%, compared with monotherapies at 16 MIC. Scanning electron microscopy further confirmed bacterial cell membrane disruption, suggesting a synergism between carbapenem and rifampicin against a representative isolate. The findings demonstrated that the combination of rifampicin with carbapenems could improve antibacterial activities and eradicate established Acinetobacter baumannii biofilm.

Carboxymuconolactone decarboxylase is a prospective molecular target for multi-drug resistant Acinetobacter baumannii-computational modeling, molecular docking and dynamic simulation studies

Multidrug-resistant Acinetobacter baumannii (MDRAb), a priority-I pathogen declared by the World Health Organization, became a potential healthcare concern worldwide with a high mortality rate. Thus, the identification of putative molecular targets and potential lead molecules is an important concern in healthcare. The present study aimed to screen a prospective molecular target and effectual binders for the drug discovery of MDRAb by computational virtual screening approach. Based on the functional role, γ-carboxymuconolactone decarboxylase (CMD) was prioritized as the target and its three-dimensional (3D) structure was computationally modeled. Based on the availability of the 3D structure, twenty-five herbal molecules were selected by database search, and their drug-likeliness, pharmacokinetic, and toxicity features were predicted. The effectual binding of the selected molecules towards CMD was predicted by molecular docking. The stability of the best-docked complexes was predicted by molecular dynamics (MD) simulation for 100 ns and binding energy calculations were carried out by molecular mechanics generalized Born and surface area solvation (MM/GBSA) method. Out of twenty-five molecules screened, hirsutine (an indole alkaloid of Uncaria rhynchophylla) and thymoquinone (a phytochemical of Nigella sativa) were qualified for drug likeliness, pharmacokinetic, and toxicity features and demonstrated significant effectual binding to CMD when compared with the binding of co-crystallized inhibitor and CMD (control). The docked complexes of hirsutine and thymoquinone, and CMD were stabilized by the binding energies of -8. 30 and -8. 46 kcal/mol respectively. These molecules were qualified in terms of ideal drug likeliness, ADME, and toxicity properties. MD simulation studies showed that the ligand-protein complexes were stable throughout the simulation. The binding free energies of the complexes by MMGBSA were estimated to be -42.08157745 kcal/mol and -36.58618242 kcal/mol for hirsutine and thymoquinone respectively when compared with the calculated binding free energy of the control (-28.75032666 kcal/mol). This study concluded that hirsutine and thymoquinone can act as potential lead molecules against CMD and the present hypothesis can be scaled up to develop potential inhibitors against MDRAb.

Gut Microbiota Composition Can Predict Colonization by Multidrug-Resistant Bacteria in SARS-CoV-2 Patients in Intensive Care Unit: A Pilot Study

The SARS-CoV-2 infection has increased the number of patients entering Intensive Care Unit (ICU) facilities and antibiotic treatments. Concurrently, the multi-drug resistant bacteria (MDRB) colonization index has risen. Considering that most of these bacteria are derived from gut microbiota, the study of its composition is essential. Additionally, SARS-CoV-2 infection may promote gut dysbiosis, suggesting an effect on microbiota composition. This pilot study aims to determine bacteria biomarkers to predict MDRB colonization risk in SARS-CoV-2 patients in ICUs. Seventeen adult patients with an ICU stay >48 h and who tested positive for SARS-CoV-2 infection were enrolled in this study. Patients were assigned to two groups according to routine MDRB colonization surveillance: non-colonized and colonized. Stool samples were collected when entering ICUs, and microbiota composition was determined through Next Generation Sequencing techniques. Gut microbiota from colonized patients presented significantly lower bacterial diversity compared with non-colonized patients (p < 0.05). Microbiota in colonized subjects showed higher abundance of Anaerococcus, Dialister and Peptoniphilus, while higher levels of Enterococcus, Ochrobactrum and Staphylococcus were found in non-colonized ones. Moreover, LEfSe analysis suggests an initial detection of Dialister propionicifaciens as a biomarker of MDRB colonization risk. This pilot study shows that gut microbiota profile can become a predictor biomarker for MDRB colonization in SARS-CoV-2 patients.

Efficacy of Fosfomycin-Containing Regimens for Treatment of Bacteremia Due to Pan-Drug Resistant Acinetobacter baumannii in Critically Ill Patients: A Case Series Study

Acinetobacter baumannii (AB) has evolved over the last decades as a major problem in carbapenem-resistant gram-negative nosocomial infections, associated with high mortality rates especially in the intensive care unit (ICU). Recent reports highlight the increasing prevalence of resistance to colistin, a last resort therapeutic option for carbapenem-resistant AB. We retrospectively evaluated the characteristics, treatment regimens and outcomes of twenty patients with pan-drug resistant (PDR) AB primary bacteremia hospitalized in the ICU of the University General Hospital of Patras, during a two-year period (October 2020-September 2022). The 28-day mortality reached 50%. Between survivors and non-survivors, no differences were found regarding age, gender, and Charlson comorbidity index (CCI). However, non-survivors had higher APACHE II scores and higher prevalence of septic shock and COVID-19 infection. A significantly higher percentage in the survivor group received Fosfomycin as part of the combination regimen. Inclusion of fosfomycin in the combination therapeutic regimen was associated with significantly better survival as compared to non-fosfomycin-containing regimens. In view of the increasing prevalence of PDR-AB infections in ICUs, its associated high rates of mortality and the lack of effective treatment options, the observed survival benefit with fosfomycin inclusion in the therapeutic regimen merits further validation in larger prospective studies.

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.

Acinetobacter baumannii Resistance to Sulbactam/Durlobactam: A Systematic Review

Infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) have limited therapeutic options. Sulbactam-durlobactam is a combination of two βlactamase inhibitors with activity against CRAB under phase 3 clinical investigation. We performed a systematic review on in vitro studies reporting A. baumannii resistances against sulbactam/durlobactam. We considered "resistant" species to be those with MIC ≥ 8 mg/L. Ten studies were included in the review (9754 tested isolates). Overall, 2.3% of A. baumannii were resistant to sulbactam/durlobactam, and this percentage rose to 3.4% among CRAB subgroups and to 3.7% among colistin-resistant strains. Resistance was 100% among metallo β-lactamase-producing strains. Overall, in 12.5% of cases, sulbactam/durlobactam resistance was associated with the production of NDM-1, in 31.7% of cases with the substitutions in the PBP3 determinants, and in the remaining cases the resistance mechanism was unknown. In conclusion, A. baumannii resistance towards sulbactam/durlobactam is limited, except for MBL-producing strains.

Prescription Pattern of Intravenous Fosfomycin in a Provincial Hospital in Thailand

BACKGROUND

In Thailand, active antibiotics against Gram-negative bacteria are limited. The re-emergence of intravenous (IV) fosfomycin is an alternative. IV fosfomycin has broad-spectrum activity, relative safety, and availability. The limitations of the clinical use of IV fosfomycin include the lack of susceptibility reports and unclear dosing. Therefore, this study was designed to examine the prescription pattern of IV fosfomycin in Chonburi Hospital, a provincial hospital in Thailand.

MATERIALS AND METHODS

A retrospective descriptive study involving in-patients aged ≥18 years who received IV fosfomycin between February 2019 and January 2020. Data were collected from the electronic patient records.

RESULTS

Of 265 patients, 254 (95.8%) and 11 (4.2%) received IV fosfomycin for treatment and prophylaxis, respectively. IV fosfomycin was prescribed for empirical and definitive treatment. All 166 organisms were Gram-negative bacteria (GNB), including Enterobacterales (47.0%), Acinetobacter baumannii (44.0%), and Pseudomonas aeruginosa (9.0%). Moreover, 141 (87.6%) isolates were carbapenem-resistant GNB (CR-GNB). The most commonly used IV fosfomycin regimen contained colistin or aminoglycosides. Furthermore, 35.3% of the combination regimens contained one active antibiotic. The appropriate dosage of IV fosfomycin for treating urinary tract infection was 71.8%. The 14-day all-cause mortality rate in CR-GNB was 45.0%.

CONCLUSION

IV fosfomycin is reserved for secondary use in treating nosocomial infection with resistant GNB. It is used synergistically with other antibiotics. At least one active antibiotic and the optimal fosfomycin dosage should be considered. An antimicrobial stewardship program should be implemented for the optimal use of fosfomycin.

Evaluation of Fosfomycin-Sulbactam Combination Therapy against Carbapenem-Resistant Acinetobacter baumannii Isolates in a Hollow-Fibre Infection Model

Static concentration in vitro studies have demonstrated that fosfomycin- or sulbactam-based combinations may be efficacious against carbapenem-resistant Acinetobacter baumannii (CRAB). In the present study, we aimed to evaluate the bacterial killing and resistance suppression potential of fosfomycin-sulbactam combination therapies against CRAB isolates in a dynamic infection model. We simulated clinically relevant dosing regimens of fosfomycin (8 g every 8 h, 1 h infusion) and sulbactam (12 g continuous infusion or 4 g every 8 h, 4 h infusion) alone and in combination for 7 days in a hollow-fibre infection model (HFIM) against three clinical isolates of CRAB. The simulated pharmacokinetic profiles in the HFIM were based on fosfomycin and sulbactam data from critically ill patients. Fosfomycin monotherapy resulted in limited bacterial killing. Sulbactam monotherapies resulted in ~ 3 to 4 log10 kill within the first 8 to 32 h followed by regrowth of up to 8 to 10 log10 CFU/mL. A combination of fosfomycin and continuous infusion of sulbactam led to a ~2 to 4 log10 reduction in bacterial burden within the first 24 h, which was sustained throughout the duration of the experiments. A combination of fosfomycin and extended infusion of sulbactam produced a ~4 log10 reduction in colony count within 24 h. This study demonstrated that fosfomycin in combination with sulbactam is a promising option for the treatment of MDR A. baumannii. Further studies are needed to further assess the potential clinical utility of this combination.

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.

In Vitro Activity of Sulbactam-Durlobactam against Carbapenem-Resistant Acinetobacter baumannii Clinical Isolates: A Multicentre Report from Italy

In the present study, the in vitro activity of the sulbactam-durlobactam (SUL-DUR) combination was evaluated against 141 carbapenem-resistant A. baumannii (CRAb) clinical strains collected from six Italian laboratories. Over half (54.6%) of these isolates were resistant to colistin. The SUL-DUR combination was active against these CRAb isolates with MIC₅₀ and MIC₉₀ values of 0.5 mg/L and 4 mg/L, respectively. Only eleven isolates were resistant to SUL-DUR with MIC values ranging from 8 to 128 mg/L. The SUL-DUR resistant A. baumannii exhibited several antimicrobial resistance genes (ARGs) such as bla_OXA-20, bla_OXA-58, bla_OXA-66, bla_ADC-25, aac(6')-Ib3 and aac(6')-Ib-cr and mutations in gyrA (S81L) and parC (V104I, D105E). However, in these isolates, mutations Q488K and Y528H were found in PBP3. Different determinants were also identified in these CRAb isolates, including adeABC, adeFGH, adeIJK, abeS, abaQ and abaR, which encode multidrug efflux pumps associated with resistance to multiple antibacterial agents. This is the first report on the antimicrobial activity of SUL-DUR against carbapenem-resistant A. baumannii isolates selected from multiple regions in Italy.

Antibiotic Treatment of Acinetobacter baumannii Superinfection in Patients With SARS-CoV-2 Infection Admitted to Intensive Care Unit: An Observational Retrospective Study

Introduction

In COVID-19 patients on mechanical ventilation, VAP from Acinetobacter baumannii remains a crucial risk factor for death. Antibiotic resistance represents an important problem in treating this infection. This study aims to describe the evolution of the superinfection from PDR Acinetobacter baumannii in patients with acute respiratory failure from SARS-CoV-2 infection admitted to ICU and compare the impact of two different antibiotic strategies on microbiological negativization.

Methods

Single-center observational retrospective study, including patients admitted to our ICU from March 2020 to May 2021 for acute respiratory failure from SARS-CoV-2 infection who developed PDR Acinetobacter baumannii superinfection. Clinical data at ICU admission were collected, as well as the timing of isolation of Acinetobacter baumannii, its resistance profile, the site of infection, and the antibiotic therapy.

Results

Of the 32 patients enrolled, 10 patients (31.2%) were treated with the combination of high-dose ampicillin/sulbactam, high-dose tigecycline, intravenous and inhaled colistin (Protocol), the other 22 (68.8%) were treated with the combination of two antibiotics (Control). Of the 10 patients in the Protocol group, 8 patients (80%) received also fosfomycin. All patients (100%) in the Protocol group had microbiological negativization, while in the Control group microbiological negativization was observed in 8 (36.4%) patients, p < 0.01.

Conclusion

Our report shows microbiological negativization in all patients treated with the combination therapy of nebulized and intravenous colistin, high-dose tigecycline, and high-dose ampicillin/sulbactam. This combination of antibiotics seems to be a useful alternative when other treatments are not available or fail.

Treatment of ventilator-associated pneumonia due to carbapenem-resistant Gram-negative bacteria with novel agents: a contemporary, multidisciplinary ESGCIP perspective

INTRODUCTION

: In the past 15 years, treatment of VAP caused by carbapenem-resistant Gram-negative bacteria (CR-GNB) has represented an intricate challenge for clinicians.

AREAS COVERED

In this perspective article, we discuss the available clinical data about novel agents for the treatment of CR-GNB VAP, together with general PK/PD principles for the treatment of VAP, in the attempt to provide some suggestions for optimizing antimicrobial therapy of CR-GNB VAP in the daily clinical practice.

EXPERT OPINION

Recently, novel BL and BL/BLI combinations have become available that have shown potent in vitro activity against CR-GNB and have attracted much interest as novel, less toxic, and possibly more efficacious options for the treatment of CR-GNB VAP compared with previous standard of care. Besides randomized controlled trials, a good solution to enrich our knowledge on how to use these novel agents at best in the near future, while at the same time remaining adherent to current evidence-based guidelines, is to improve our collaboration to conduct larger multinational observational studies to collect sufficiently large populations treated in real life with those novel agents for which guidelines currently do not provide a recommendation (in favor or against) for certain causative organisms.

Antibiotic treatment of acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

Acute bacterial skin and skin structure infections (ABSSSI) are a leading cause of morbidity, with a considerable variety of clinical presentation and a wide range of etiological pathogens. Of importance, the spread of multidrug-resistant (MDR) strains (i.e. methicillin-resistant Staphylococcus aureus or Gram-negative bacteria) is increasingly reported in some regions. in this review, we summarize the current clinical approach to patients with ABSSSI.

RECENT FINDINGS

Accurate diagnosis and identification of risk factors for MDR pathogens are key determinants for administering appropriate therapy in patients with ABSSSI. In daily clinical practice, this can be critical as there are many features defining the 'high risk patient' including both disease and host-associated risk factors.

SUMMARY

Antibiotic therapy should be based according to the different clinical spectrum of disease belonging to the ABSSSI, on the pathogens most likely to be involved and local resistance. Careful evaluation of antibiotic therapy after 48-72 h of initial therapy could help clinicians to early identify patients with treatment failure and to consider an alternative approach. Close monitoring of patients with multiple comorbidities, drug-drug interaction or adverse host factors are also necessary.

Carbapenem-resistant Acinetobacter baumannii: Colonization, Infection and Current Treatment Options

Carbapenem-resistant Acinetobacter baumannii (CRAB) causes colonization and infection predominantly in hospitalized patients. Distinction between the two is a challenge. When CRAB is isolated from a non-sterile site (soft tissue, respiratory samples, etc.), it probably represents colonization unless clear signs of infection (fever, elevated white blood count, elevated inflammatory markers and abnormal imaging) are present. Treatment is warranted only for true infections. In normally sterile sites (blood, cerebrospinal fluid) the presence of indwelling medical devices (catheters, stents) should be considered when evaluating positive cultures. In the absence of such devices, the isolate represents an infection and should be treated. If an indwelling device is present and there are no signs of active infection, the device should be replaced if possible, and no treatment is required. If there are signs of an active infection the device should be removed or replaced, and treatment should be administered. Current treatments options and clinical data are limited. No agent or combination regimen has been shown to be superior to any other in randomized clinical trials. Ampicillin-sulbactam appears to have the best evidence for initial use. This is probably due to its ability to saturate penicillin-binding proteins 1 and 3 when given in high dose. Tigecycline when used should be given in high dose as well. Polymyxins are a treatment option but are difficult to dose correctly and have significant side effects. Newer treatment options such as eravacycline and cefiderocol have potential; however, currently there are not enough data to support their use as single agents. Combination therapy appears to be the best treatment option and should always include high-dose ampicillin-sulbactam combined with another active agent such as high-dose tigecycline, polymyxins, etc. These infections require a high complexity of skill, and an infectious disease specialist should be involved in the management of these patients.

The role of Gram-negative bacteria in skin and soft tissue infections

PURPOSE OF REVIEW

Skin and soft tissue infections (SSTIs) are a leading cause of morbidity, emergency department visits and hospitalization. In recent years, the spread of carbapenem-resistant gram-negative bacteria (GNB) is also increasing in SSTIs. However, the armamentarium of available drugs is recently expanding as well. In this review, we reported the most recent data and about management and treatment of SSTIs caused by GNB, mainly for the treatment of carbapenem-resistant Enterobacterales (CRE), Pseudomonas spp and Acinetobacter spp.

RECENT FINDINGS

The increasing incidence of carbapenem-resistant GNB is challenging for management and treatment, considering the high rate of inappropriate empiric and targeted antimicrobial treatments. The role of new antibiotics, mainly licensed for the treatment of other infections, is an object of continuous debate. As a matter of fact, no specific clinical trials on SSTIs have been performed for new drugs; however, recent data about the use in real life of new compounds in clinical practice are available.

SUMMARY

Some recently approved drugs are actually considered the backbone of targeted therapy in patients with severe infections caused by susceptible carbapenem-resistant GNB strains. Prompt diagnosis of cSSTIs is crucial and, when necessary, surgical debridement for source control of infection is the milestone of the treatment. The physicians should be confident to identify patients at high risk for multidrug-resistant pathogens to minimize inappropriate empiric therapy.

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.

The Interplay between Host Defense, Infection, and Clinical Status in Septic Patients: A Narrative Review

Sepsis is a life-threatening condition that arises when the body's response to an infection injures its own tissues and organs. Despite significant morbidity and mortality throughout the world, its pathogenesis and mechanisms are not clearly understood. In this narrative review, we aimed to summarize the recent developments in our understanding of the hallmarks of sepsis pathogenesis (immune and adaptive immune response, the complement system, the endothelial disfunction, and autophagy) and highlight novel laboratory diagnostic approaches. Clinical management is also discussed with pivotal consideration for antimicrobic therapy management in particular settings, such as intensive care unit, altered renal function, obesity, and burn patients.

An Evidence-Based Multidisciplinary Approach Focused on Creating Algorithms for Targeted Therapy of Infection-Related Ventilator-Associated Complications (IVACs) Caused by Pseudomonas aeruginosa and Acinetobacter baumannii in Critically Ill Adult Patients

(1) Background: To develop evidence-based algorithms for targeted antibiotic therapy of infection-related ventilator-associated complications (IVACs) caused by non-fermenting Gram-negative pathogens. (2) Methods: A multidisciplinary team of four experts had several rounds of assessments for developing algorithms devoted to targeted antimicrobial therapy of IVACs caused by two non-fermenting Gram-negative pathogens. A literature search was performed on PubMed-MEDLINE (until September 2021) to provide evidence for supporting therapeutic choices. Quality and strength of evidence was established according to a hierarchical scale of the study design. Six different algorithms with associated recommendations in terms of therapeutic choice and dosing optimization were suggested according to the susceptibility pattern of two non-fermenting Gram-negative pathogens: multi-susceptible Pseudomonas aeruginosa (PA), multidrug-resistant (MDR) metallo-beta-lactamase (MBL)-negative-PA, MBL-positive-PA, carbapenem-susceptible Acinetobacter baumannii (AB), and carbapenem-resistant AB. (3) Results: Piperacillin–tazobactam or fourth-generation cephalosporins represent the first therapeutic choice in IVACs caused by multi-susceptible PA. A carbapenem-sparing approach favouring the administration of novel beta-lactam/beta-lactamase inhibitors should be pursued in the management of MDR-MBL-negative PA infections. Cefiderocol should be used as first-line therapy for the management of IVACs caused by MBL-producing-PA or carbapenem-resistant AB. Fosfomycin-based combination therapy, as well as inhaled colistin, could be considered as a reasonable alternative for the management of IVACs due to MDR-PA and carbapenem-resistant AB. (4) Conclusions: The implementation of algorithms focused on prompt revision of antibiotic regimens guided by results of conventional and rapid diagnostic methodologies, appropriate place in therapy of novel beta-lactams, implementation of strategies for sparing the broadest-spectrum antibiotics, and pharmacokinetic/pharmacodynamic optimization of antibiotic dosing regimens is strongly suggested.

Diagnosis and Treatment of Bacterial Pneumonia in Critically Ill Patients with COVID-19 Using a Multiplex PCR Assay: A Large Italian Hospital's Five-Month Experience

Bacterial pneumonia is a challenging coronavirus disease 2019 (COVID-19) complication for intensive care unit (ICU) clinicians. Upon its implementation, the FilmArray pneumonia plus (FA-PP) panel's practicability for both the diagnosis and antimicrobial therapy management of bacterial pneumonia was assessed in ICU patients with COVID-19. Respiratory samples were collected from patients who were mechanically ventilated at the time bacterial etiology and antimicrobial resistance were determined using both standard-of-care (culture and antimicrobial susceptibility testing [AST]) and FA-PP panel testing methods. Changes to targeted and/or appropriate antimicrobial therapy were reviewed. We tested 212 samples from 150 patients suspected of bacterial pneumonia. Etiologically, 120 samples were positive by both methods, two samples were culture positive but FA-PP negative (i.e., negative for on-panel organisms), and 90 were negative by both methods. FA-PP detected no culture-growing organisms (mostly Staphylococcus aureus or Pseudomonas aeruginosa) in 19 of 120 samples or antimicrobial resistance genes in two culture-negative samples for S. aureus organisms. Fifty-nine (27.8%) of 212 samples were from empirically treated patients. Antibiotics were discontinued in 5 (33.3%) of 15 patients with FA-PP-negative samples and were escalated/deescalated in 39 (88.6%) of 44 patients with FA-PP-positive samples. Overall, antibiotics were initiated in 87 (72.5%) of 120 pneumonia episodes and were not administered in 80 (87.0%) of 92 nonpneumonia episodes. Antimicrobial-resistant organisms caused 78 (60.0%) of 120 episodes. Excluding 19 colistin-resistant Acinetobacter baumannii episodes, AST confirmed appropriate antibiotic receipt in 101 (84.2%) of 120 episodes for one or more FA-PP-detected organisms. Compared to standard-of-care testing, the FA-PP panel may be of great value in the management of COVID-19 patients at risk of developing bacterial pneumonia in the ICU. IMPORTANCE Since bacterial pneumonia is relatively frequent, suspicion of it in COVID-19 patients may prompt ICU clinicians to overuse (broad-spectrum) antibiotics, particularly when empirical antibiotics do not cover the suspected pathogen. We showed that a PCR-based, culture-independent laboratory assay allows not only accurate diagnosis but also streamlining of antimicrobial therapy for bacterial pneumonia episodes. We report on the actual implementation of rapid diagnostics and its real-life impact on patient treatment, which is a gain over previously published studies on the topic. A better understanding of the role of that or similar PCR assays in routine ICU practice may lead us to appreciate the effectiveness of their implementation during the COVID-19 pandemic.

Systematic review and meta-analysis of the proportion and associated mortality of polymicrobial (vs monomicrobial) pulmonary and bloodstream infections by Acinetobacter baumannii complex

BACKGROUND

Differentiating Acinetobacter baumannii complex (ABC) infection from colonization remains difficult and further complicated in polymicrobial infections.

PURPOSE

To assess the frequency of polymicrobial ABC infections and associated mortality. We hypothesized a lower mortality in polymicrobial infections if ABC isolation reflects colonization in some polymicrobial infections.

METHODS

A systematic review was conducted in PubMed, Scopus and CENTRAL for studies reporting ABC pulmonary and bloodstream infections. The proportion of infections that were polymicrobial and the magnitude of the association between polymicrobial (vs monomicrobial) infection and mortality were estimated with meta-analyses.

RESULTS

Based on 80 studies (9759 infections) from 23 countries, the pooled proportion of polymicrobial infection was 27% (95% CI 22-31%) and was similarly high for bloodstream and pulmonary infections. Polymicrobial infection was variably and insufficiently defined in most (95%) studies. Considerable heterogeneity (I² = 95%) was observed that persisted in subgroup analyses and meta-regressions. Based on 17 studies (2675 infections), polymicrobial infection was associated with lower 28-day mortality (OR = 0.75, 95% CI 0.58-0.98, I² = 36%). However, polymicrobial infection was not associated with in-hospital mortality (OR = 0.97, 95% CI 0.69-1.35, I² = 0%) based on 14 studies (953 infections). The quality of evidence (GRADE) for the association of polymicrobial (vs monomicrobial) infection with mortality was low and at high risk of bias.

CONCLUSION

Polymicrobial ABC infections are common and may be associated with lower 28-day mortality. Considering the heterogeneity of polymicrobial infections and limitations of the available literature, more research is required to clarify the clinical impact of polymicrobial (vs monomicrobial) ABC infection.

Multidrug-resistant Acinetobacter baumannii infections in COVID-19 patients hospitalized in intensive care unit

Objectives

Superinfections in patients hospitalized in intensive care unit (ICU) are an important and challenging complication, also in COVID-19. However, no definitive data are available about the role of multidrug-resistant Acinetobacter baumannii (MDR-AB) in COVID-19.

Methods

This was a single-center, cross-sectional study including patients with MDR-AB infections admitted to ICU with or without COVID-19, between January 2019 and January 2021. The primary objective of the study was to evaluate risk factor for MDR-AB infections in ICU patients hospitalized for COVID-19 or other etiology. The secondary endpoints were 30-days mortality in all study population and risk factors associated with development of bloodstream infection (BSI).

Results

During the study period 32 adults with COVID-19 were enrolled and compared with 115 patients admitted in the same ICU for other reasons. We observed a total of 114 deaths, with a survival rate of 29.3%: 18.8% in COVID-19 and 32.2% in control group. Relative risk for MDR-AB infection in COVID-19 showed that serum lactate levels mmol/l > 2, Acinetobacter baumannii colonization, BSI and steroid therapy were observed more frequently in COVID-19 patients. Cox regression analysis showed that serum lactate levels > 2 mmol/l, Acinetobacter baumannii colonization, BSI, and steroid therapy were associated with 30-days mortality. Finally, patients with COVID-19, white blood cells count > 11,000 mm³, serum lactate levels > 2 mmol/l, infections at time of ICU admission, Acinetobacter baumannii colonization, and steroid therapy were independently associated with development of BSI.

Conclusions

Our data highlight the impact of BSI on outcome, the role of Acinetobacter baumannii colonization and the use of steroids on the risk to develop MDR-AB infections also during COVID-19.

Cefiderocol-Based Combination Therapy for "Difficult-to-Treat" Gram-Negative Severe Infections: Real-Life Case Series and Future Perspectives

Cefiderocol is a new cephalosporin displaying against extensively resistant (XDR) Gram-negative bacteria. We report our experience with cefiderocol-based combination therapies as “rescue” treatments in immunocompromised or critically ill patients or in patients with post-surgical infections who had failed previous regimens. A total of 13 patients were treated from 1 September 2020 to 31 March 2021. In total, 5/13 (38%) patients were classified as critically ill, due to severe COVID-19 lung failure; 4/13 (31%) patients had post-surgical infections and 4/13 (31%) had severe infections in immunocompromised subjects due to solid organ transplantation (2/4) or hematological malignancy (2/4). Overall, 10/13 infections were caused by carbapenem-resistant Acinetobacter baumannii, one by KPC-positive ceftazidime/avibactam-resistant Klebsiella pneumonia and two by Pseudomonas aeruginosa XDR. Based on clinical, microbiological and hematobiochemical evaluation, cefiderocol was associated with different companion drugs, particularly with fosfomycin, high-dose tigecycline and/or colistin. Microbiological eradication was achieved in all cases and the 30-day survival rate was 10/13; two patients died due to SARS-CoV-2 lung failure, whereas one death was attributed to subsequent infections. No recurrent infections within 30 days were reported. Finally, we hereby discuss the therapeutic potential of cefiderocol and the possible place in the therapy of this novel drug.

Evaluation of the Synergistic Antibacterial Effects of Fosfomycin in Combination with Selected Antibiotics against Carbapenem-Resistant Acinetobacter baumannii

The spread of multi-drug resistant (MDR) pathogens and the lagging pace in the development of novel chemotherapeutic agents warrant the use of combination therapy as a reliable, cost-effective interim option. In this study, the synergistic effects of fosfomycin in combination with other antibiotics were assessed. Of the 193 isolates, 90.6% were non-susceptible to fosfomycin, with minimum inhibitory concentrations (MICs) of ≥128 µg/mL. Antibacterial evaluation of fosfomycin-resistant isolates indicated multi-drug resistance to various antibiotic classes. Combinations of fosfomycin with 12 commonly used antibiotics synergistically inhibited most fosfomycin-resistant isolates. The fractional inhibitory concentration index indicated that combining fosfomycin with either aminoglycosides, glycylcyclines, fluoroquinolones, or colistin resulted in 2- to 16-fold reduction in the MIC of fosfomycin. Time-kill kinetics further confirmed the synergistic bactericidal effects of fosfomycin in combination with either amikacin, gentamicin, tobramycin, minocycline, tigecycline, or colistin, with more than 99.9% reduction in bacterial cells. Fosfomycin-based combination therapy might serve as an alternative option for the treatment of MDR A. baumannii. Further steps including in vivo efficacy and toxicity in experimental models of infection are required prior to clinical applications.

Recent molecules in the treatment of severe infections caused by ESBL-producing bacteria

Introduction: The widespread increase in resistance to β-lactam antibiotics in Enterobacterales currently represents one of the main threats to human health worldwide. The primary mechanisms of resistance are the production of β-lactamase enzymes that are able to hydrolyze β-lactams.Areas covered: we summarize the most recent advances regarding the main characteristics and spectrum of activity of new available antibiotics and strategies for the treatment of ESBL-producing Enterobacterales infections.Expert opinion: ESBL-producing strains are recognized as a worldwide challenge in the treatment of both hospital- and community-acquired infections. Data from the literature point out the high mortality associated with severe infections due to ESBL strains, especially in patients who developed severe sepsis or septic shock, together with the importance of the source of infection and indicators of severity, as determinants of the patient's outcome. Carbapenems are currently considered the first-line therapy, although the diffusion of resistant strains is an evolving problem and is mandatory the introduction in clinical practice of new drug regimens and treatment strategies, based on clinical data, local epidemiology, and microbiology. As a possible carbapenem-sparing strategy, ceftolozane-tazobactam and ceftazidime-avibactam appear the best-available carbapenem-sparing therapies. The definitive role of new drugs should be definitively assessed.