Multidrug-resistant Acinetobacter baumannii infections in lung transplant patients in the cardiothoracic intensive care unit

Burden and Management of Multi-Drug Resistant Organism Infections in Solid Organ Transplant Recipients Across the World: A Narrative Review

Solid organ transplant (SOT) recipients are particularly susceptible to infections caused by multidrug-resistant organisms (MDRO) and are often the first to be affected by an emerging resistant pathogen. Unfortunately, their prevalence and impact on morbidity and mortality according to the type of graft is not systematically reported from high-as well as from low and middle-income countries (HIC and LMIC). Thus, epidemiology on MDRO in SOT recipients could be subjected to reporting bias. In addition, screening practices and diagnostic resources may vary between countries, as well as the availability of new drugs. In this review, we aimed to depict the burden of main Gram-negative MDRO in SOT patients across HIC and LMIC and to provide an overview of current diagnostic and therapeutic resources.

Impact of Immunosuppressed Status on Prognosis of Carbapenem-Resistant Organisms Bloodstream Infections

INTRODUCTION

The impact of immunosuppression on prognosis of carbapenem-resistant organism (CRO) bloodstream infection (BSI) remains unclear. The aim of this study was to clarify the relationship between immunosuppression and mortality of CRO-BSI and to identify the risk factors associated with mortality in immunosuppressed patients.

METHODS

This retrospective study included 279 patients with CRO-BSI from January 2018 to March 2023. Clinical characteristics and outcomes were compared between the immunosuppressed and immunocompetent patients. The relationship between immunosuppression and 30-day mortality after BSI onset was assessed through logistic-regression analysis, propensity score matching (PSM) and inverse probability of treatment weighting (IPTW). Factors associated with mortality in immunosuppressed patients were analyzed using multivariable logistic regression analysis.

RESULTS

A total of 88 immunocompetent and 191 immunosuppressed patients were included, with 30-day all-cause mortality of 58.8%. Although the 30-day mortality in immunosuppressed patients was significantly higher than in immunocompetent patients (46.6% vs. 64.4%, P = 0.007), immunosuppression was not an independent risk factor for mortality in multivariate logistic regression analysis (odds ratio [OR] 3.53, 95% confidence interval [CI] 0.74-18.89; P = 0.123), PSM (OR 1.38, 95% CI 0.60-3.18; P = 0.449,) or IPTW (OR 1.40, 95% CI 0.58-3.36; P = 0.447). For patients with CRO-BSI, regardless of immune status, appropriate antibiotic therapy was associated with decreased 30-day mortality, while Charlson comorbidity index (CCI), intensive care unit (ICU)-acquired infection and thrombocytopenia at CRO-BSI onset were associated with increased mortality.

CONCLUSION

Despite the high mortality rate of CRO-BSI, immunosuppression did not affect the mortality. Appropriate antibiotic therapy is crucial for improving the prognosis of CRO-BSI, regardless of the immune status.

Treatment of Staphylococcus aureus infection with sphingosine in ex vivo perfused and ventilated lungs

BACKGROUND

Ex vivo lung perfusion (EVLP) has expanded the donor pool for lung transplantation. Pulmonary Staphylococcus aureus infection, especially that caused by multidrug-resistant strains, is a severe threat to posttransplantation outcomes. Sphingosine is a lipid compound that exhibits broad-spectrum antibacterial activity. Therefore, we aimed to evaluate the effects of S aureus infection on EVLP and whether sphingosine administration during EVLP prevents infection with S aureus.

METHODS

Eighteen pigs were randomly assigned to 3 groups: uninfected, infected with S aureus with NaCl treatment, or infected with sphingosine treatment. Bacterial numbers were determined before and after treatment. Sphingosine concentrations in the lung tissues were determined using biochemical assays. Lung histology, lung physiological parameters, perfusate content, lung weight, and cell death were measured to analyze the effects of infection and sphingosine administration on EVLP.

RESULTS

Sphingosine administration significantly reduced the bacterial load. The concentration of sphingosine in the bronchial epithelium was elevated after sphingosine administration. S aureus infection increased pulmonary artery pressure and pulmonary vascular resistance. Lung edema, histology scores, lactate and lactate dehydrogenase levels in the perfusate, ΔPO2 in the perfusate, static lung compliance, and lung peak airway pressure did not differ among the groups.

CONCLUSIONS

Infection of S aureus did not affect the lung function during EVLP but induced higher pulmonary artery pressure and pulmonary vascular resistance. Administration of sphingosine effectively eliminated S aureus without side effects in isolated, perfused, and ventilated pig lungs.

Etiologic characteristics revealed by mNGS-mediated ultra-early and early microbiological identification in airway secretions from lung transplant recipients

Background

Post-operative etiological studies are critical for infection prevention in lung transplant recipients within the first year. In this study, mNGS combined with microbial culture was applied to reveal the etiological characteristics within one week (ultra-early) and one month (early) in lung transplant recipients, and the epidemiology of infection occurred within one month.

Methods

In 38 lung transplant recipients, deep airway secretions were collected through bronchofiberscope within two hours after the operation and were subjected to microbial identification by mNGS and microbial culture. The etiologic characteristics of lung transplant recipients were explored. Within one month, the infection status of recipients was monitored. The microbial species detected by mNGS were compared with the etiological agents causing infection within one month.

Results

The detection rate of mNGS in the 38 airway secretions specimens was significantly higher than that of the microbial culture (P<0.0001). MNGS identified 143 kinds of pathogenic microorganisms; bacterial pathogens account for more than half (72.73%), with gram-positive and -negative bacteria occupying large proportions. Fungi such as Candida are also frequently detected. 5 (50%) microbial species identified by microbial culture had multiple drug resistance (MDR). Within one month, 26 (68.42%) recipients got infected (with a median time of 9 days), among which 10 (38.46%) cases were infected within one week. In the infected recipients, causative agents were detected in advance by mNGS in 9 (34.62%) cases, and most of them (6, 66.67%) were infected within one week (ultra-early). In the infection that occurred after one week, the consistency between mNGS results and the etiological agents was decreased.

Conclusion

Based on the mNGS-reported pathogens in airway secretions samples collected within two hours, the initial empirical anti-infection regimes covering the bacteria and fungi are reasonable. The existence of bacteria with MDR forecasts the high risk of infection within 48 hours after transplant, reminding us of the necessity to adjust the antimicrobial strategy. The predictive role of mNGS performed within two hours in etiological agents is time-limited, suggesting continuous pathogenic identification is needed after lung transplant.

The Prevalence of Multidrug-Resistant Acinetobacter baumannii and Its Vaccination Status among Healthcare Providers

There is growing concern among healthcare providers worldwide regarding the prevalence of multidrug-resistant Acinetobacter baumannii (A. baumannii). Some of the worst hospital-acquired infections, often in intensive care units (ICUs), are caused by this bacterial pathogen. In recent years, the rise in multidrug-resistant A. baumannii has been linked to the overuse of antimicrobial drugs and the lack of adequate infection control measures. Infections caused by this bacterial pathogen are the result of prolonged hospitalization and ICU stays, and they are associated with increased morbidity and mortality. This review outlines the epidemiology, risk factors, and antimicrobial resistance associated with A. baumannii in various countries, with a special focus on the Kingdom of Saudi Arabia. In response to the growing concern regarding this drug-resistant bacteria, fundamental information about its pathology has been incorporated into the development of vaccines. Although these vaccines have been successful in animal models, their effectiveness in humans remains unproven. The review will discuss the development of A. baumannii vaccines, potential related obstacles, and efforts to find an effective strategy against this pathogen.

Relationship between immunosuppression and intensive care unit-acquired colonization and infection related to multidrug-resistant bacteria: a prospective multicenter cohort study

PURPOSE

The impact of immunosuppression on intensive care unit (ICU)-acquired colonization and infection related to multidrug-resistant (MDR) bacteria (ICU-MDR-col and ICU-MDR-inf, respectively) is unknown.

METHODS

We carried out an observational prospective cohort study in 8 ICUs in France (all with single-bed rooms and similar organizational characteristics). All consecutive patients with an ICU stay > 48 h were included, regardless of immune status, and followed for 28 days. Patients underwent systematic screening for colonization with MDR bacteria upon admission and every week subsequently. Immunosuppression was defined as active cancer or hematologic malignancy, neutropenia, solid-organ transplant, use of steroids or immunosuppressive drugs, human immunodeficiency virus infection and genetic. The primary endpoint was the incidence rate of a composite outcome including ICU-MDR-col and/or ICU-MDR-inf.

RESULTS

750 patients (65.9% males, median age 65 years) were included, among whom 264 (35.2%) were immunocompromised. Reasons for ICU admission, severity scores and exposure to invasive devices and antibiotics during ICU stay were comparable between groups. After adjustment for center and pre-specified baseline confounders, immunocompromised patients had a lower incidence rate of ICU-MDR-col and/or ICU-MDR-inf (adjusted incidence ratio 0.68, 95% CI 0.52-0.91). When considered separately, the difference was significant for ICU-MDR-col, but not for ICU-MDR-inf. The distribution of MDR bacteria was comparable between groups, with a majority of Enterobacteriacae resistant to third-generation cephalosporins (~ 74%).

CONCLUSION

Immunocompromised patients had a significantly lower incidence rate of a composite outcome including ICU-MDR-col and/or ICU-MDR-inf. This finding points to the role of contact precautions and isolation measures, and could have important implications on antibiotic stewardship in this population.

Upregulated circulating mir-424 and its’ diagnostic value for gram-negative bacteremia after thoracic transplantation

Aims

Early post-transplant complications such as acute graft rejection and infections are associated with high morbidity and mortality of heart and lung transplant recipients who are in vital need of immunosuppressive therapy. MiR-424 is a member of the miR-16 family, which plays an important physiological role in the development of cardiovascular and respiratory pathology, is involved in the regulation of monocyte and macrophage differentiation, and has an immunosuppressive potential. The aim of the study was to determine the diagnostic value of circulating miR-424 as a potential biomarker of post-transplant complications in heart and lung transplant recipients.

Methods

The study enrolled 83 heart transplant recipients, aged 18 to 70 (48 ± 13) years; 26 lung transplant recipients, aged 10 to 74 (36 ± 16) years. The miR-424 plasma expression was detected by real-time PCR (Qiagen, USA). Significance of miR-424 level was assessed through the ΔCt method. Acute graft rejection was verified by the results of endomyocardial or transbronchial biopsy. Post-transplant infectious complications were verified through microbiological identification of bacteremia from blood cultures.

Results

Our study shows miR-424 upregulation in plasma of patients with chronic heart or respiratory failure in comparison with healthy individuals (p = 0.003 and p = 0.04 resp.). There was a direct correlation of miR-424 expression with red blood cells and hemoglobin levels in patients before heart transplantation (p = 0.01 and p = 0.03 resp.). After transplantation the expression of plasma miR-424 correlated with the level of C-reactive protein (CRP) both in heart (r = 0.75; p = 0.02) and lung (r = 0.50; p = 0.04) transplant recipients. The expression of plasma miR-424 correlated with tacrolimus blood concentration after heart transplantation (r = 0.38; p = 0.04). The miR-424 level didn't differ in heart or lung transplant recipients with and without acute graft rejection (p = 0.47 and p = 0.78 resp.), but was significantly higher in heart and lung transplant recipients with gram-negative bacteremia (p = 0.002). When the miR-424 level is above a threshold value (−5.72 fold change), the relative risk of bacteremia is RR = 3.84 [95% CI 1.94–7.61]; Se = 60.0%; Sp = 89.2%. CRP concentration above 7 mg/L in duplex test with miR-424 improves the diagnostic characteristics of miR-424 for post-transplant gram-negative bacteremia in heart and lung transplant recipients up to RR = 9.17 [95% CI 1.37–61.46]; Se = 83.3% and Sp = 90.1%.

Conclusion

MiR-424 plasma expression was upregulated in patients with chronic heart and respiratory failure and in heart and lung transplant recipients in the early post-transplant period. The duplex test, including miR-424 and CRP, has a diagnostic value for detecting the high risk of post-transplant gram-negative bacteremia in heart and lung transplant recipients.

Multidrug-resistant infections in solid organ transplant recipients: a focus on risk factors, prevention and treatment strategies

Solid organ transplantation is the best therapeutic option for patients with end-stage organ disease and, according to the data from international registries, there has been a steady increase in numbers and results. However, post-transplant infections remain a fearsome complication with, in the last decade, an increasing incidence of episodes due to antibiotic-resistant bacteria and opportunistic agents. In this paper, we summarize the most relevant and updated knowledge concerning infections from multidrug-resistant germs in solid organ transplant recipients, focusing on risk factors, treatment and prevention strategies, and antimicrobial pharmacokinetics relevant to this particular population of patients.

Bacterial infections in lung transplantation

Lung transplantation has lower survival rates compared to other than other solid organ transplants (SOT) due to higher rates of infection and rejection-related complications, and bacterial infections (BI) are the most frequent infectious complications. Excess morbidity and mortality are not only a direct consequence of these BI, but so are subsequent loss of allograft tolerance, rejection, and chronic lung allograft dysfunction due to bronchiolitis obliterans syndrome (BOS). A wide variety of pathogens can cause infections in lung transplant recipients (LTRs), including a number of nosocomial pathogens and other multidrug-resistant (MDR) pathogens. Although pneumonia and intrathoracic infections predominate, LTRs are at risk of a number of types of infections. Risk factors include altered anatomy and function of airways, impaired immunity, the microbial flora of the donor and recipient, underlying medical conditions, and genetic factors. Further work on immune monitoring has the potential to improve outcomes. The infecting agents can be derived from the donor lung, pre-existing recipient flora, or acquired from the environment over time. Certain infections may preclude lung transplantation, but this varies from center to center, and more recent studies suggest fewer patients should be disqualified. New molecular methods allow microbiome studies of the lung, gut, and other sites that may further our knowledge of how airway colonization can result in infection and allograft loss. Surveillance, early diagnosis, and aggressive antimicrobial therapy of BI is critical in LTRs. Antibiotic resistance is a major barrier to successful management of these infections. The availability of new agents for MDR Gram-negatives may improve outcomes. Other new therapies, such as bacteriophage therapy, show promise for the future. Finally, it is important to prevent infections through peri-transplant prophylaxis, vaccination, and infection control measures.

New drugs for difficult bugs: management of multidrug-resistant gram-negative infections in solid organ transplant recipients

PURPOSE OF REVIEW

Multidrug-resistant Gram-negative bacteria remain a significant threat to patient and allograft survival. Management of these infections in solid organ transplant (SOT) recipients remains challenging due to a limited antimicrobial pipeline and reliance on novel agents, which have not been systematically evaluated in the transplant population.

RECENT FINDINGS

Novel antimicrobials, including the second-generation β-lactam/β-lactamase inhibitors, cefiderocol, plazomicin and eravacycline, have been developed to combat infections due to multidrug-resistant Gram-negative infections, but each has microbiologic and therapeutic niches and warrant further study in SOT recipients.

SUMMARY

This review summarizes therapeutic options for extended-spectrum β-lactamase-producing Enterobacterales, carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa with difficult-to-treat resistance in SOT recipients and emphasizes recently approved antimicrobial agents.

[The problem of global development of antibiotic resistant nosocomial pathogens]

The problem of global expansion of multidrug-resistant nosocomial infections pathogens is under special attention at the moment. Antibiotic resistance increasing give us the limited treatment options. This problem is particularly acute for transplant clinics, because of patients need lifelong immunosuppressive therapy. From the one hand this ensures stable allograft functioning, but from the other increases the risk of severe infectious complications in the postoperative period. The purpose of this article is analysis carbapenem resistance dynamics of Klebsiella spp., Acinetobacter spp., Pseudomonas spp. and Staphylococcus spp. isolated from the blood of recipients of donor organs from 2009 to 2019 in the Shumakov National Medical Research Center of Transplantology and Artificial Organs. A significant annual decrease of carbapenem-sensitive strains of Klebsiella spp. and Acinetobacter spp. are shown. The study of a distinctive pathogen resistance profile specific to each institution can help one in selecting an adequate antimicrobial strategy and is an effective predictive tool for controlling the growth of multidrug-resistant microorganisms.

Synthesis of 4,4'-(4-Formyl-1H-pyrazole-1,3-diyl)dibenzoic Acid Derivatives as Narrow Spectrum Antibiotics for the Potential Treatment of Acinetobacter Baumannii Infections

Acinetobacter baumannii has emerged as one of the most lethal drug-resistant bacteria in recent years. We report the synthesis and antimicrobial studies of 25 new pyrazole-derived hydrazones. Some of these molecules are potent and specific inhibitors of A. baumannii strains with a minimum inhibitory concentration (MIC) value as low as 0.78 µg/mL. These compounds are non-toxic to mammalian cell lines in in vitro studies. Furthermore, one of the potent molecules has been studied for possible in vivo toxicity in the mouse model and found to be non-toxic based on the effect on 14 physiological blood markers of organ injury.

Challenges in the Diagnosis and Management of Bacterial Lung Infections in Solid Organ Recipients: A Narrative Review

Respiratory infections pose a significant threat to the success of solid organ transplantation, and the diagnosis and management of these infections are challenging. The current narrative review addressed some of these challenges, based on evidence from the literature published in the last 20 years. Specifically, we focused our attention on (i) the obstacles to an etiologic diagnosis of respiratory infections among solid organ transplant recipients, (ii) the management of bacterial respiratory infections in an era characterized by increased antimicrobial resistance, and (iii) the development of antimicrobial stewardship programs dedicated to solid organ transplant recipients.

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.

Multidrug-resistant Acinetobacter baumannii infection in lung transplant recipients: risk factors and prognosis

Backgrounds: Infectious complication is an important cause of poor outcome of lung transplantation (LT). Infections with Acinetobacter baumannii (A. baumannii) are problematic, because of limited therapeutic option due to increasing resistance to antibiotics. However, there are few studies on A. baumannii infection in lung transplant recipients. Thus, we aimed to investigate epidemiology and risk factors for infection with A. baumannii in lung transplant recipients. Methods: Lung transplant recipients ≥18 years of age in a university hospital were enrolled in this retrospective cohort study. Risk factors for infection with multidrug resistant A. baumannii and 90-day mortality were analysed. Results: Fifty-one of 96 lung transplant recipients experienced A. baumannii infection. Infected patients had a significantly higher 90-day mortality rate than uninfected (19.6% vs. 2.2%, p = .009). High blood urea nitrogen (BUN) before transplantation (odds ratio [OR] 1.16; p = .008), long duration of surgery (OR 1.16; p = .029) and hypoalbuminemia before transplantation (OR 4.01; p = .037) were independent risk factors for infection with multidrug resistant A. baumannii. On multivariate analysis, severe thrombocytopenia (OR 28.69; p = .005), high serum creatinine (OR 1.48; p = .042) and infection with multidrug resistant A. baumannii (OR 22.58; p = .031) were independent risk factors for 90-day mortality. Conclusions: Prolonged surgery, high BUN and hypoalbuminemia before LT were significant risk factors for infection with multidrug resistant A. baumannii. Severe thrombocytopenia, high serum creatinine and infection with multidrug resistant A. baumannii infection were independent risk factors for 90-day mortality.

Management of multidrug resistant Gram-negative bacilli infections in solid organ transplant recipients: SET/GESITRA-SEIMC/REIPI recommendations

Solid organ transplant (SOT) recipients are especially at risk of developing infections by multidrug resistant (MDR) Gram-negative bacilli (GNB), as they are frequently exposed to antibiotics and the healthcare setting, and are regulary subject to invasive procedures. Nevertheless, no recommendations concerning prevention and treatment are available. A panel of experts revised the available evidence; this document summarizes their recommendations: (1) it is important to characterize the isolate's phenotypic and genotypic resistance profile; (2) overall, donor colonization should not constitute a contraindication to transplantation, although active infected kidney and lung grafts should be avoided; (3) recipient colonization is associated with an increased risk of infection, but is not a contraindication to transplantation; (4) different surgical prophylaxis regimens are not recommended for patients colonized with carbapenem-resistant GNB; (5) timely detection of carriers, contact isolation precautions, hand hygiene compliance and antibiotic control policies are important preventive measures; (6) there is not sufficient data to recommend intestinal decolonization; (7) colonized lung transplant recipients could benefit from prophylactic inhaled antibiotics, specially for Pseudomonas aeruginosa; (8) colonized SOT recipients should receive an empirical treatment which includes active antibiotics, and directed therapy should be adjusted according to susceptibility study results and the severity of the infection.

Sterilization of Lung Matrices by Supercritical Carbon Dioxide

Lung engineering is a potential alternative to transplantation for patients with end-stage pulmonary failure. Two challenges critical to the successful development of an engineered lung developed from a decellularized scaffold include (i) the suppression of resident infectious bioburden in the lung matrix, and (ii) the ability to sterilize decellularized tissues while preserving the essential biological and mechanical features intact. To date, the majority of lungs are sterilized using high concentrations of peracetic acid (PAA) resulting in extracellular matrix (ECM) depletion. These mechanically altered tissues have little to no storage potential. In this study, we report a sterilizing technique using supercritical carbon dioxide (ScCO2) that can achieve a sterility assurance level 10(-6) in decellularized lung matrix. The effects of ScCO2 treatment on the histological, mechanical, and biochemical properties of the sterile decellularized lung were evaluated and compared with those of freshly decellularized lung matrix and with PAA-treated acellular lung. Exposure of the decellularized tissue to ScCO2 did not significantly alter tissue architecture, ECM content or organization (glycosaminoglycans, elastin, collagen, and laminin), observations of cell engraftment, or mechanical integrity of the tissue. Furthermore, these attributes of lung matrix did not change after 6 months in sterile buffer following sterilization with ScCO2, indicating that ScCO2 produces a matrix that is stable during storage. The current study's results indicate that ScCO2 can be used to sterilize acellular lung tissue while simultaneously preserving key biological components required for the function of the scaffold for regenerative medicine purposes.