Intravenous plus inhaled versus intravenous colistin monotherapy for lower respiratory tract infections: A systematic review and meta-analysis

Outcome of intravenous and inhaled polymyxin B treatment in patients with multidrug-resistant gram-negative bacterial pneumonia

PURPOSE

The incidence of pneumonia caused by multidrug-resistant gram-negative bacteria (MDR GNB) is increasing, which imposes significant burden on public health. Inhalation combined with intravenous polymyxins has emerged as a viable treatment option. However, pharmacokinetic studies focusing on intravenous and inhaled polymyxin B (PMB) are limited.

METHODS

This study included seven patients with MDR GNB-induced pneumonia who were treated with intravenous plus inhaled PMB from March 1 to November 30, 2022, in the intensive care unit of the First Affiliated Hospital of Zhejiang University School of Medicine. Clinical outcomes and therapeutic drug monitoring data of PMB in both plasma and epithelial lining fluid (ELF) were retrospectively reviewed.

RESULTS

Median PMB concentrations in the ELF were 7.83 (0.72-66.5), 116.72 (17.37-571.26), 41.1 (3.69-133.78) and 33.82 (0.83-126.68) mg/L at 0, 2, 6 and 12 h, respectively, and were much higher than those detected in the serum. ELF concentrations of PMB at 0, 2, 6 and 12 h were higher than the minimum inhibitory concentrations of pathogens isolated from the patients. Steady-state concentrations of PMB in the plasma were >2 mg/L in most patients. Of the patients, 57.14% were cured and 71.43% showed a favourable microbiological response. The incidence of side effects with PMB was low.

CONCLUSIONS

Inhaled plus intravenous PMB can achieve high ELF concentrations and favourable clinical outcomes without an increased adverse effect profile. This treatment approach appears promising for the treatment of patients with pneumonia caused by MDR-GNB.

Guidelines for Antibacterial Treatment of Carbapenem-Resistant Enterobacterales Infections

This guideline aims to promote the prudent use of antibacterial agents for managing carbapenem-resistant Enterobacterales (CRE) infections in clinical practice in Korea. The general section encompasses recommendations for the management of common CRE infections and diagnostics, whereas each specific section is structured with key questions that are focused on antibacterial agents and disease-specific approaches. This guideline covers both currently available and upcoming antibacterial agents in Korea.

High-Loading-Dose Colistin with Nebulized Administration for Carbapenem-Resistant Acinetobacter baumannii Pneumonia in Critically Ill Patients: A Retrospective Cohort Study

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections pose a serious threat, with high morbidity and mortality rates. This retrospective cohort study, conducted at Nakornping Hospital between January 2015 and October 2022, aimed to evaluate the efficacy and safety of a high loading dose (LD) of colistin combined with nebulized colistin in critically ill patients with CRAB pneumonia. Of the 261 patients included, 95 received LD colistin, and 166 received LD colistin with nebulized colistin. Multivariate Cox regression analysis, adjusted for baseline covariates using inverse probability weighting, showed no significant difference in 30-day survival between patients who received LD colistin and those who received LD colistin with nebulized colistin (adjusted hazard ratio [aHR]: 1.17, 95% confidence interval [CI]: 0.80-1.72, p = 0.418). Likewise, there were no significant differences in clinical response (aHR: 0.93, 95% CI: 0.66-1.31, p = 0.688), microbiological response (aHR: 1.21, 95% CI: 0.85-1.73, p = 0.279), or nephrotoxicity (aHR: 1.14, 95% CI: 0.79-1.64, p = 0.492) between the two treatment groups. No significant adverse events related to nebulized colistin were reported. These findings suggest that the addition of nebulized colistin may not offer additional benefits in terms of 30-day survival, clinical or microbiological response, or nephrotoxicity in these patients.

Structure-Interaction Relationship of Polymyxins with Lung Surfactant

Multidrug-resistant Gram-negative bacteria present an urgent and formidable threat to the global public health. Polymyxins have emerged as a last-resort therapy against these 'superbugs'; however, their efficacy against pulmonary infection is poor. In this study, we integrated chemical biology and molecular dynamics simulations to examine how the alveolar lung surfactant significantly reduces polymyxin antibacterial activity. We discovered that lung surfactant is a phospholipid-based permeability barrier against polymyxins, compromising their efficacy against target bacteria. Next, we unraveled the structure-interaction relationship between polymyxins and lung surfactant, elucidating the thermodynamics that govern the penetration of polymyxins through this critical surfactant layer. Moreover, we developed a novel analog, FADDI-235, which exhibited potent activity against Gram-negative bacteria, both in the presence and absence of lung surfactant. These findings shed new light on the sequestration mechanism of lung surfactant on polymyxins and importantly pave the way for the rational design of new-generation lipopeptide antibiotics to effectively treat Gram-negative bacterial pneumonia.

Prevalence of Pseudomonas aeruginosa and its antibiotic resistance in patients who have received Hematopoietic Stem-Cell Transplantation; A globally Systematic Review

Gram-negative bacteria are infectious and life-threatening agents after hematopoietic stem cell transplantation (HSCT). So, this study aimed to investigate the prevalence of Pseudomonas aeruginosa and its antibiotic resistance in patients who have received Hematopoietic Stem-Cell Transplantation through a systematic review. The systematic search was done with key words; Pseudomonas aeruginosa, hematopoietic stem cell transplantation from 2000 to the end of July 2023 in Google Scholar and PubMed/Medline, Scopus, and Web of Science. Twelve studies were able to include our study. Quality assessment of studies was done by Appraisal tool for Cross-Sectional Studies. The most of the included studies were conducted as allo-HSCT. Infections such as respiratory infection, urinary infection and bacteremia have occurred. The rate of prevalence with P. aeruginosa has varied between 3 and 100%. The average age of the participants was between 1 and 74 years. The rate of prevalence of P. aeruginosa resistant to several drugs has been reported to be variable, ranging from 20 to 100%. The highest antibiotic resistance was reported against cefotetan (100%), and the lowest was related to tobramycin (1.8%) followed by amikacin, levofloxacin and ciprofloxacin with the prevalence of 16.6%. Our findings showed a high prevalence and antibiotic resistance rate of P. aeruginosa in Hematopoietic stem cell transplantation. Therefore, more serious health measures should be taken in patients after transplantation.

The Efficacy and Safety of Intravenous Colistin Plus Aerosolized Colistin Versus Intravenous Colistin Alone in Critically Ill Trauma Patients With Multi-Drug Resistant Gram-Negative Bacilli Infection

BACKGROUND AND AIM

Gram-negative bacteria (GNB) with potential multiple drug resistance (MDR) have emerged as a major group of organisms causing ventilator-associated pneumonia (VAP). Higher concentrations are deposited directly in the lungs when antibiotics are given via inhalation, minimizing systemic side effects. This study aims to compare the efficacy and safety of intravenous plus aerosolized colistin versus intravenous (IV) colistin alone in critically ill trauma patients who reported MDR-GNB infection on endotracheal aspirate culture.

METHODS

A hundred patients were recruited in the Intensive Care Unit, Trauma Centre, Institute of Medical Sciences, Banaras Hindu University, Varanasi, and randomly assigned to the control (n=50) group, which received IV colistin plus aerosolized colistin and the intervention group (n = 50), which received IV colistin alone. Changes in total leucocyte count (TLC), renal function test (RFT), endotracheal aspirate culture, 24-hour urine output, length of ICU stay, and 28-day ICU mortality were investigated.

RESULTS

Patients receiving intravenous plus nebulized colistin therapy had a better outcome compared to IV colistin alone in terms of faster eradication of MDR-GNB infection. A rise in serum urea and creatinine levels was seen in both groups, which were significantly higher, along with a decrease in urine output in the group receiving intravenous colistin alone. No significant difference was observed in serum sodium and potassium levels in the RFT protocol, length of ICU stay, or 28-day ICU mortality.

CONCLUSION

Intravenous nebulized colistin could be considered a better alternative therapy for VAP caused by multi-drug-resistant Gram-negative bacteria in the ICU in terms of faster microbiological cure and lesser nephrotoxicity.

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

Purpose

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

Patients and Methods

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

Results

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

Conclusion

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

High-Dose Nebulized Colistin Methanesulfonate and the Role in Hospital-Acquired Pneumonia Caused by Gram-Negative Bacteria with Difficult-to-Treat Resistance: A Review

Hospital-acquired pneumonia, including ventilator-associated pneumonia (VAP) due to difficult-to-treat-resistant (DTR) Gram-negative bacteria, contributes significantly to morbidity and mortality in ICUs. In the era of COVID-19, the incidences of secondary nosocomial pneumonia and the demand for invasive mechanical ventilation have increased dramatically with extremely high attributable mortality. Treatment options for DTR pathogens are limited. Therefore, an increased interest in high-dose nebulized colistin methanesulfonate (CMS), defined as a nebulized dose above 6 million IU (MIU), has come into sight. Herein, the authors present the available modern knowledge regarding high-dose nebulized CMS and current information on pharmacokinetics, clinical studies, and toxicity issues. A brief report on types of nebulizers is also analyzed. High-dose nebulized CMS was administrated as an adjunctive and substitutive strategy. High-dose nebulized CMS up to 15 MIU was attributed with a clinical outcome of 63%. High-dose nebulized CMS administration offers advantages in terms of efficacy against DTR Gram-negative bacteria, a favorable safety profile, and improved pharmacokinetics in the treatment of VAP. However, due to the heterogeneity of studies and small sample population, the apparent benefit in clinical outcomes must be proven in large-scale trials to lead to the optimal use of high-dose nebulized CMS.

Efficacy and safety of intravenous combined with aerosolised polymyxin versus intravenous polymyxin alone in the treatment of multidrug-resistant gram-negative bacterial pneumonia: A systematic review and meta-analysis

Background

Previous studies have questioned the efficacy and safety of intravenous combined with aerosolised (IV + AS) polymyxin versus intravenous (IV) polymyxin alone in the treatment of patients with multidrug-resistant gram-negative bacterial (MDR-GNB) pneumonia. Therefore, we conducted a meta-analysis to evaluate the efficacy and safety of IV + AS polymyxin in the treatment of MDR-GNB pneumonia.

Methods

We identified all relevant studies by searching the PubMed, EMBASE and Cochrane library databases from their inception to May 31, 2022. All included studies were evaluated using the Newcastle Ottawa scale (NOS) checklist. The summary relative risk (RR) and 95% confidence interval (CI) were used to determine the outcome differences between the IV + AS and the IV groups. Subgroup analysis was performed based on population, polymyxin dose and kinds of polymyxin.

Results

A total of 16 studies were included in the meta-analysis. The IV + AS group had lower mortality (RR = 0.86, 95% CI: 0.77-0.97, P = 0.01) than the IV group. Subgroup analysis revealed that IV + AS polymyxin could reduce mortality only when used in low doses. Simultaneously, the IV + AS group outperformed the IV group in terms of clinical response rate, clinical cure rate, microbiological eradication and duration of mechanical ventilation. The duration of hospitalisation and the incidence of nephrotoxicity did not differ significantly between the two groups.

Conclusions

IV + AS polymyxin is beneficial in the treatment of MDR-GNB pneumonia. It could lower patient mortality and improve clinical and microbial outcomes without increasing the risk of nephrotoxicity. However, retrospective analysis in the majority of studies and heterogeneity between studies implies that our findings must be interpreted carefully.

How to Use Nebulized Antibiotics in Severe Respiratory Infections

Difficult-to-treat pulmonary infections caused by multidrug-resistant (MDR) pathogens are of great concern because their incidence continues to increase worldwide and they are associated with high morbidity and mortality. Nebulized antibiotics are increasingly being used in this context. The advantages of the administration of a nebulized antibiotic in respiratory tract infections due to MDR include the potential to deliver higher drug concentrations to the site of infection, thus minimizing the systemic adverse effects observed with the use of parenteral or oral antibiotic agents. However, there is an inconsistency between the large amount of experimental evidence supporting the administration of nebulized antibiotics and the paucity of clinical studies confirming the efficacy and safety of these drugs. In this narrative review, we describe the current evidence on the use of nebulized antibiotics for the treatment of severe respiratory infections.

Inhaled Colistimethate Sodium in the Management of Patients with Bronchiectasis Infected by Pseudomonas aeruginosa: A Narrative Review of Current Evidence

International guidelines on the treatment of bronchiectasis indicate that the use of inhaled antibiotics is effective, especially in symptomatic chronic bronchial infection (CBI) due to Pseudomonas aeruginosa (PA). To date, however, no such treatment has been approved by regulatory agencies. Of the inhaled antibiotics on the market, colistimethate sodium (colistin) is one of the most used in many countries, either in its nebulized presentation or as dry powder. Among the characteristics of this antibiotic, it is worth noting that its main target is the lipopolysaccharide in the outer membrane of the cell wall of gram-negative bacteria and that it has a low rate of resistance to PA (<1%). Most observational studies have shown that the use of colistin in patients with bronchiectasis and CBI due to PA results in a decrease in both the number and severity of exacerbations, an improvement in quality of life, a decrease in sputum volume and purulence, and a high rate of PA eradication, although there are no clear differences with respect to other inhaled antibiotics. However, the lack of randomized clinical trials (RCT) with positive results for its main variable (exacerbations) in an intention-to-treat analysis has prevented its approval by regulatory agencies as a formal indication for use in bronchiectasis. The PROMIS program, made up of two RCT with identical methodology, is currently underway. The first of these RCT (already concluded) has demonstrated a clearly positive effect on the group randomized to colistin in its main variable (number of annual exacerbations), while the results of the second are still pending. This review presents exhaustive information on the pharmacological and microbiological characteristics of colistin, the results of the studies carried out to date, and the future challenges associated with this treatment.

Treatment of Acinetobacter baumannii severe infections

Acinetobacter baumannii is a Gram-negative, multidrug-resistant (MDR) pathogen that causes nosocomial infections, especially in intensive care units (ICUs) and immunocompromised patients. A. baumannii has developed a broad spectrum of antimicrobial resistance, associated with a higher mortality rate among infected patients compared with other non-baumannii species. In terms of clinical impact, resistant strains are associated with increases in both in-hospital length of stay and mortality. A. baumannii can cause a variety of infections, especially ventilator-associated pneumonia, bacteremia, and skin wound infections, among others. The most common risk factors for the acquisition of MDR A. baumannii are previous antibiotic use, mechanical ventilation, length of ICU and hospital stay, severity of illness, and use of medical devices. Current efforts are focused on addressing all the antimicrobial resistance mechanisms described in A. baumannii, with the objective of identifying the most promising therapeutic scheme.

Antibiotic Therapy for Difficult-to-Treat Infections in Lung Transplant Recipients: A Practical Approach

Lung transplant recipients are at higher risk to develop infectious diseases due to multi-drug resistant pathogens, which often chronically colonize the respiratory tract before transplantation. The emergence of these difficult-to-treat infections is a therapeutic challenge, and it may represent a contraindication to lung transplantation. New antibiotic options are currently available, but data on their efficacy and safety in the transplant population are limited, and clinical evidence for choosing the most appropriate antibiotic therapy is often lacking. In this review, we provide a summary of the best evidence available in terms of choice of antibiotic and duration of therapy for MDR/XDR P. aeruginosa, Burkholderia cepacia complex, Mycobacterium abscessus complex and Nocardia spp. infections in lung transplant candidates and recipients.

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.

Successful treatment of pneumonia caused by multidrug-resistant Pseudomonas aeruginosa after allogeneic hematopoietic stem cell transplantation with colistin and amikacin inhalation therapy

Pseudomonas aeruginosa is a Gram-negative bacillus that often causes severe infections during immunosuppression in patients with hematologic malignancies. P. aeruginosa can easily acquire drug resistance, and often develops into multidrug-resistant P. aeruginosa (MDRP). Although many antibiotics are used in combination to treat MDRP infections, colistin and amikacin are less likely to be transferred to the lungs, and inhalation therapy may be used. Herein, we report a Case of pneumonia caused by MDRP after allogeneic hematopoietic stem cell transplantation (HSCT) treated with inhaled colistin and amikacin. This 61-year-old female patient was diagnosed with myelodysplastic syndromes and underwent allogeneic HSCT from an 8/8 HLA-matched unrelated donor after reduced-intensity conditioning. On the day of the stem cell infusion, the patient's sputum culture was found to be positive for MDRP. The patient subsequently developed bacteremia, pneumonia, and lung abscess caused by MDRP, and we administered multidrug antibiotic therapy including colistin and amikacin inhalation therapy. The patient's blood cultures were subsequently turned negative, and the lung abscess disappeared. To our knowledge, this is the first case of MDRP pneumonia after HSCT in which colistin and amikacin inhalation therapy was effective.

Nebulized Colistin in Ventilator-Associated Pneumonia and Tracheobronchitis: Historical Background, Pharmacokinetics and Perspectives

Clinical evidence suggests that nebulized colistimethate sodium (CMS) has benefits for treating lower respiratory tract infections caused by multidrug-resistant Gram-negative bacteria (GNB). Colistin is positively charged, while CMS is negatively charged, and both have a high molecular mass and are hydrophilic. These physico-chemical characteristics impair crossing of the alveolo-capillary membrane but enable the disruption of the bacterial wall of GNB and the aggregation of the circulating lipopolysaccharide. Intravenous CMS is rapidly cleared by glomerular filtration and tubular excretion, and 20-25% is spontaneously hydrolyzed to colistin. Urine colistin is substantially reabsorbed by tubular cells and eliminated by biliary excretion. Colistin is a concentration-dependent antibiotic with post-antibiotic and inoculum effects. As CMS conversion to colistin is slower than its renal clearance, intravenous administration can lead to low plasma and lung colistin concentrations that risk treatment failure. Following nebulization of high doses, colistin (200,000 international units/24h) lung tissue concentrations are > five times minimum inhibitory concentration (MIC) of GNB in regions with multiple foci of bronchopneumonia and in the range of MIC breakpoints in regions with confluent pneumonia. Future research should include: (1) experimental studies using lung microdialysis to assess the PK/PD in the interstitial fluid of the lung following nebulization of high doses of colistin; (2) superiority multicenter randomized controlled trials comparing nebulized and intravenous CMS in patients with pandrug-resistant GNB ventilator-associated pneumonia and ventilator-associated tracheobronchitis; (3) non-inferiority multicenter randomized controlled trials comparing nebulized CMS to intravenous new cephalosporines/ß-lactamase inhibitors in patients with extensive drug-resistant GNB ventilator-associated pneumonia and ventilator-associated tracheobronchitis.

[Infections due to multidrug-resistant pathogens : Pathogens, resistance mechanisms and established treatment options]

The increase in resistant pathogens has long been a global problem. Complicated life-threatening infections due to multidrug-resistant pathogens (MRD) meanwhile occur regularly in intensive care medicine. An important and also potentially modifiable factor of the rapid spread of resistance is the irrational use of broad spectrum antibiotics in human medicine. In addition to many other resistance mechanisms, beta-lactamases play an important role in Gram-negative pathogens. They are not uncommonly the leading reason of difficult to treat infections and the failure of known routinely used broad spectrum antibiotics, such as cephalosporins, (acylamino)penicillins and carbapenems. Strategies for containment of MRDs primaríly target the rational use of antibiotics. In this respect interdisciplinary treatment teams, e.g. antibiotic stewardship (ABS) and infectious diseases stewardship (IDS) play a major role.

Inhalation with intravenous loading dose of colistin in critically ill patients with pneumonia caused by carbapenem-resistant gram-negative bacteria

Background:

Despite the increasing use of colistin in clinical practice, the optimal dosing, and administration route have not been established. This study aimed to evaluate the clinical outcome and safety of intravenous (IV) colistin with a loading dose (LD) and adjunctive aerosolized (AS) colistin administration in critically ill patients with hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP) caused by carbapenem-resistant gram-negative bacteria (CRGNB).

Methods:

We retrospectively reviewed 191 critically ill patients who received colistin for the treatment of HAP or VAP caused by CRGNB. Patients were divided into three groups: non-LD IV (patients received only IV colistin without LD), LD IV (patients received only IV colistin with LD), and AS–LD (patients received IV colistin with LD and adjunctive AS colistin).

Results:

There was no difference in clinical response between the three groups. However, the rate of microbiological eradication was significantly higher in the AS–LD group (60%) than in the non-LD IV (31%), and LD IV (33%) groups (p = 0.010). Patients treated with adjunctive AS colistin in combination with LD IV had significantly lower 30-day mortality rates than patients treated with IV colistin alone (p = 0.027). After adjusting for potential confounding factors, adjunctive AS colistin was still significantly associated with lower mortality (adjusted OR 0.338, CI 95% 0.132–0.864, p = 0.024). However, nephrotoxicity did not change according to the use of LD regimen and AS colistin administration (p = 0.100).

Conclusions:

Adjunctive AS colistin in combination with IV colistin with LD was related to an improved 30-day mortality and microbiological outcome without an increase in nephrotoxicity in critically ill patients with HAP and VAP caused by CRGNB.

The reviews of this paper are available via the supplemental material section.

Treatment of Ventilator-associated Pneumonia with High-dose Colistin Under Continuous Veno-venous Hemofiltration

Background and Objectives

High-dose colistin (COL) ensures adequate treatment of pneumonia caused by multidrug resistant gram-negative bacteria (MDR-GNB) but must be weighed against a higher risk of nephrotoxicity. Continuous veno-venous hemofiltration (CVVH) clears COL by filtering and membrane adsorption that permits to avoid dose accumulation and excessively high peak concentrations. We evaluated clinical/microbiological efficacy of the high-dose COL treatment under CVVH in patients with newly diagnosed MDR-GNB ventilator-associated pneumonia (VAP).

Methods

Observational cohort study in critically ill adult patients with MDR-GNB VAP. Colistimethate sodium (CMS) was administered as a 9 million international units (MIU) of loading dose followed by 3 × 4.5 MIU daily. CVVH was performed over a highly adsorptive membrane. Clinical and microbiological efficacies were assessed at the end of therapy. In survivors, serum creatinine level was evaluated before and at the end of therapy.

Results

Fourteen patients (8 male patients, aged 57 ± 14 years) were consecutively included. Isolated pathogens were Pseudomonas aeruginosa in 7, Klebsiella pneumoniae in 5, and other Enterobacteriaceae in 2 patients. A favorable clinical response was observed in 9 patients (64%). Full and presumed microbiological eradication was observed in 12 patients (86%). Two patients were diagnosed with Stage 1 acute kidney injury.

Conclusions

In patients with MDR-GNB VAP, CVVH may represent an interesting option to enable effective high-dose COL treatment.

Epidemiology and Treatment of Multidrug-Resistant and Extensively Drug-Resistant Pseudomonas aeruginosa Infections

In recent years, the worldwide spread of the so-called high-risk clones of multidrug-resistant or extensively drug-resistant (MDR/XDR) Pseudomonas aeruginosa has become a public health threat. This article reviews their mechanisms of resistance, epidemiology, and clinical impact and current and upcoming therapeutic options. In vitro and in vivo treatment studies and pharmacokinetic and pharmacodynamic (PK/PD) models are discussed. Polymyxins are reviewed as an important therapeutic option, outlining dosage, pharmacokinetics and pharmacodynamics, and their clinical efficacy against MDR/XDR P. aeruginosa infections. Their narrow therapeutic window and potential for combination therapy are also discussed. Other "old" antimicrobials, such as certain β-lactams, aminoglycosides, and fosfomycin, are reviewed here. New antipseudomonals, as well as those in the pipeline, are also reviewed. Ceftolozane-tazobactam has clinical activity against a significant percentage of MDR/XDR P. aeruginosa strains, and its microbiological and clinical data, as well as recommendations for improving its use against these bacteria, are described, as are those for ceftazidime-avibactam, which has better activity against MDR/XDR P. aeruginosa, especially strains with certain specific mechanisms of resistance. A section is devoted to reviewing upcoming active drugs such as imipenem-relebactam, cefepime-zidebactam, cefiderocol, and murepavadin. Finally, other therapeutic strategies, such as use of vaccines, antibodies, bacteriocins, anti-quorum sensing, and bacteriophages, are described as future options.

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

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

Reservoirs of resistance: polymyxin resistance in veterinary-associated companion animal isolates of Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is an opportunistic pathogen and a major cause of infections. Widespread resistance in human infections are increasing the use of last resort antimicrobials such as polymyxins. However, these have been used for decades in veterinary medicine. Companion animals are an understudied source of antimicrobial resistant P. aeruginosa isolates. This study evaluated the susceptibility of P. aeruginosa veterinary isolates to polymyxins to determine whether the veterinary niche represents a potential reservoir of resistance genes for pathogenic bacteria in both animals and humans.

METHODS AND RESULTS

Clinical P. aeruginosa isolates (n=24) from UK companion animals were compared for antimicrobial susceptibility to a panel of human-associated isolates (n=37). Minimum inhibitory concentration (MIC) values for polymyxin B and colistin in the companion animals was significantly higher than in human isolates (P=0.033 and P=0.013, respectively). Genotyping revealed that the veterinary isolates were spread throughout the P. aeruginosa population, with shared array types from human infections such as keratitis and respiratory infections, suggesting the potential for zoonotic transmission. Whole genome sequencing revealed mutations in genes associated with polymyxin resistance and other antimicrobial resistance-related genes.

CONCLUSION

The high levels of resistance to polymyxin shown here, along with genetic similarities between some human and animal isolates, together suggest a need for sustained surveillance of this veterinary niche as a potential reservoir for resistant, clinically relevant bacteria in both animals and humans.

Can Nebulised Colistin Therapy Improve Outcomes in Critically Ill Children with Multi-Drug Resistant Gram-Negative Bacterial Pneumonia?

In the past decade, multidrug-resistant (MDR) gram-negative bacteria have become a major problem, especially for patients in intensive care units. Recently, colistin became the last resort therapy for MDR gram-negative bacteria infections. However, nebulised colistin use was limited to adult patients. Thus, we investigated the efficacy and safety of nebulised colistin treatment against MDR microorganisms in the paediatric intensive care unit (PICU). Data of all patients admitted for various critical illnesses (January 2016 to January 2019) were reviewed. Differences between groups (with and without a history of nebulised colistin) were compared. Of 330 patients, 23 (6.97%) used nebulised colistin. Significant relationships were found between nebulised colistin usage and several prognostic factors (inotropic drug use (p = 0.009), non-invasive mechanical ventilation (p ≤ 0.001), duration in PICU (p ≤ 0.001), and C-reactive protein level (p = 0.003)). The most common microorganism in tracheal aspirate and sputum cultures was Pseudomonas aeruginosa (13 patients). The most common underlying diagnosis was cystic fibrosis, noted in 6 patients. No serious nephrotoxicity and neurotoxicity occurred. This study showed that colistin can be safely used directly in the airway of critically ill children. However, nebulised colistin use did not have a positive effect on mortality and prognosis.