Carbapenem-resistant Acinetobacter baumannii Bacteremia in Liver Transplant Recipients

A comprehensive evaluation of risk factors for mortality, infection and colonization associated with CRGNB in adult solid organ transplant recipients: a systematic review and meta-analysis

BACKGROUND

The burden of carbapenem-resistant gram-negative bacteria (CRGNB) among solid organ transplant (SOT) recipients has not been systematically explored. Here, we discern the risk factors associated with CRGNB infection and colonization in SOT recipients.

METHODS

This study included observational studies conducted among CRGNB-infected SOT patients, which reported risk factors associated with mortality, infection or colonization. Relevant records will be searched in PubMed, Embase and Web of Science for the period from the time of database construction to 1 March 2023.

RESULTS

A total of 23 studies with 13,511 participants were included, enabling the assessment of 27 potential risk factors. The pooled prevalence of 1-year mortality among SOT recipients with CRGNB was 44.5%. Prolonged mechanical ventilation, combined transplantation, reoperation and pre-transplantation CRGNB colonization are salient contributors to the occurrence of CRGNB infections in SOT recipients. Renal replacement therapy, post-LT CRGNB colonization, pre-LT liver disease and model for end-stage liver disease score increased the risk of infection. Re-transplantation, carbapenem use before transplantation and ureteral stent utilization increaesd risk of CRGNB colonization.

CONCLUSION

Our study demonstrated that SOT recipients with CRGNB infections had a higher mortality risk. Invasive procedure may be the main factor contribute to CRGNB infection.

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.

Epidemiology and Management of Infections in Liver Transplant Recipients

Background: Improvements in liver transplant (LT) outcomes are attributed to advances in surgical techniques, use of potent immunosuppressants, and rigorous pre-LT testing. Despite these improvements, post-LT infections remain the most common complication in this population. Bacteria constitute the most common infectious agents, while fungal and viral infections are also frequently encountered. Multi-drug-resistant bacterial infections develop because of polymicrobial overuse and prolonged hospital stays. Immediate post-LT infections are commonly caused by viruses. Conclusions: Appropriate vaccination, screening of both donor and recipients before LT and antiviral prophylaxis in high-risk individuals are recommended. Antimicrobial drug resistance is common in high-risk LT and associated with poor outcomes; epidemiology and management of these cases is discussed. Additionally, we also discuss the effect of coronavirus disease 2019 (COVID-19) infection and monkeypox in the LT population.

Epidemiology and outcomes associated with enterococcal blood stream infection among liver and kidney transplant recipients

Bloodstream infections (BSIs) account for 18% of bacterial infections in the first year after solid organ transplantation (SOT). Enterococcus accounts for up to 20% of BSIs in this population, with vancomycin-resistant enterococcus (VRE) posing a particular risk. This is a retrospective, case-control study of adult liver and kidney transplant recipients between 01/01/2016 and 06/30/2021 that characterizes the epidemiology and outcomes of enterococcal BSIs in liver and kidney transplantations at a single institution. Subjects with an enterococcal BSI within the first 6 months post-transplant were compared to those with non-enterococcal BSIs in the same period. We identified 26 subjects with enterococcal BSIs and 28 controls with non-enterococcal BSIs (n = 54; 10.3%). Cases were mostly liver transplant recipients (n = 20; 77%) with a median MELD at transplant of 33 (range 14-43); controls included 14 KT recipients (50%). Groups differed significantly (all p < .05) by factors including perioperative transfusion requirements, need for reoperation, and number of interventions post-transplant. Cases had a median time of 25.5 days to infection and controls 100.5 days (p < .0001). There were no differences in 1-year mortality between the groups. Enterococcus faecium was the predominant species of Enterococcus (n = 23; 88.5%), with a majority (91.3%) of the isolates being VRE. In our liver and kidney transplants, enterococcal BSIs occurred early among liver transplant recipients. The high incidence of VRE among E. faecium isolates in this population warrants further investigation into the optimal approach to empiric antimicrobials for bacteremia in the early post-transplant period.

Epidemiology and Prevention of Early Infections by Multi-Drug-Resistant Organisms in Adults Undergoing Liver Transplant: A Narrative Review

Invasive bacterial infections are a leading cause of morbidity and mortality after liver transplant (LT), especially during the first months after LT, and infections due to multi-drug-resistant organisms (MDRO) are increasing in this setting. Most of the infections in patients in intensive care unit arise from the endogenous microflora and, for this reason, pre-LT MDRO rectal colonization is a risk factor for developing MDRO infections in the post-LT. Moreover, the transplanted liver may carry an increased risk of MDRO infections due to organ transportation and preservation, to donor intensive care unit stay and previous antibiotic exposure. To date, little evidence is available about how MDRO pre-LT colonization in donors and recipients should address LT preventive and antibiotic prophylactic strategies, in order to reduce MDRO infections in the post-LT period. The present review provided an extensive overview of the recent literature on these topics, with the aim to offer a comprehensive insight about the epidemiology of MDRO colonization and infections in adult LT recipients, donor-derived MDRO infections, possible surveillance, and prophylactic strategies to reduce post-LT MDRO infections.

Incidence, mortality, and risk factors associated with carbapenem-resistant Acinetobacter baumannii bacteremia within 30 days after liver transplantation

Carbapenem-resistant Acinetobacter baumannii bacteremia (CRAB-B) is a fatal infectious complication of liver transplantation (LT). This study investigated the incidence, effects, and risk factors associated with CRAB-B during the early post-LT period. Among 1051 eligible LT recipients, 29 patients experienced CRAB-B within 30 days of LT with a cumulative incidence of 2.7%. In the patients with CRAB-B (n = 29) and matched controls (n = 145) by nested-case control design, the cumulative incidence of death on days 5, 10, and 30 from the index date was 58.6%, 65.5%, and 65.5%, and 2.1%, 2.8%, and 4.2%, respectively (p < .001). Pre-transplant MELD (OR 1.11, 95% confidence interval [CI] 1.04-1.19, p = .002), severe encephalopathy (OR 4.62, 95% CI 1.24-18.61, p = .025), donor body mass index (OR .57, 95% CI .41-.75, p < .001), and reoperation (OR 6.40, 95% CI 1.19-36.82, p = .032) were independent risk factors for 30-day CRAB-B. CRAB-B showed extremely high mortality within 30 days after LT, especially within 5 days after its occurrence. Therefore, assessment of risk factors and early detection of CRAB, followed by proper treatment, are necessary to control CRAB-B after LT.

Drug Resistance and Risk Factors for Acquisition of Gram-Negative Bacteria and Carbapenem-Resistant Organisms Among Liver Transplant Recipients

Introduction

Infections caused by Gram-negative bacteria, in particular carbapenem-resistant organisms (CRO), pose a great threat to liver transplant (LT) recipients. Understanding the risk factors for Gram-negative and CRO infections and the drug resistance of corresponding bacteria will help guide the prevention and treatment of these infections.

Methods

Data on the composition, distribution and drug resistance of Gram-negative bacteria and CRO among LT recipients were collected. The risk factors for Gram-negative and CRO infections were identified via univariate and multivariate analysis.

Results

A total of 45 episodes of Gram-negative infection, including 20 episodes of CRO infection, occurred in 19.9% (27/136) of LT recipients. Klebsiella pneumoniae was the dominant pathogenic bacteria (14/45; 31.1%). The most common site of infection was the abdominal cavity/bile duct (11/27; 40.7%). Eleven (8.1%) patients died within 2 months after LT, and two deaths were related to Gram-negative infection. Gram-negative bacteria were relatively sensitive to tigecycline and polymyxin B, with resistance of 26.7 and 11.1%, respectively. CRO had lower resistance to ceftazidime/avibactam (45.5%) and polymyxin B (10%). A univariate analysis showed that male sex, infection within 2 months prior to LT, duration of surgery ≥ 400 min, reoperation, indwelling urethral catheter use ≥ 3 days and elevated alanine aminotransferase on day 1 post-LT were associated with Gram-negative infection. Multivariate logistic regression analysis revealed that infection within 2 months prior to LT [odds ratio (OR) = 4.426, 95%CI: 1.634–11.99, P = 0.003], duration of surgery ≥ 400 min [OR = 3.047, 95%CI: 1.194–7.773, P = 0.02] and indwelling urethral catheter use ≥ 3 days [OR = 5.728, 95%CI: 1.226–26.763, P = 0.026] were independent risk factors for Gram-negative infection after LT, and that only carbapenem use ≥ 3 days within 15 days prior to infection [OR = 14, 95%CI: 1.862–105.268, P = 0.01] was related to the occurrence of CRO infections.

Conclusion

The incidence of Gram-negative and CRO infections was high in the early post-LT period. The most common infection site was the abdominal cavity/bile duct, and the dominant pathogen was K. pneumoniae. Patients with infections within 2 months prior to LT, prolonged surgery time or delayed urethral catheter removal were prone to Gram-negative infection. Carbapenem exposure was correlated with CRO infections.

Chronic Wound Infection Model of Acinetobacter baumannii in Outbred Mice

INTRODUCTION

We established a murine wound infection model with doxycycline treatment against multidrug-resistant Acinetobacter baumannii (AB5075) in Institute of Cancer Research (ICR) outbred mice.

METHODS

Using three groups of neutropenic ICR mice, two full-thickness dorsal dermal wounds (6 mm diameter) were made on each mouse. In two groups, wounds were inoculated with 7.0 × 104 colony-forming units of AB5075. Of these two groups, one received a 6-day regimen of doxycycline while the other was sham treated with phosphate-buffered saline as placebo control. Another uninfected/untreated group served as a control. Wound closure, clinical symptoms, bacterial burden in wound beds and organs, and wound histology were investigated.

RESULTS

Doxycycline-treated wounds completely healed by day 21, but untreated, infected wounds failed to heal. Compared to controls, wound infections without treatment resulted in significant reductions in body weight and higher bacterial loads in wound beds, lung, liver, and spleen by day 7. Histological evaluation of wounds on day 21 revealed ulcerated epidermis, muscle necrosis, and bacterial presence in untreated wounds, while wounds treated with doxycycline presented intact epidermis.

CONCLUSIONS

Compared to the previously developed BALB/c dermal wound model, this study demonstrates that the mouse strain selected impacts wound severity and resolution. Furthermore, this mouse model accommodates two dorsal wounds rather than only one. These variations offer investigators increased versatility when designing future studies of wound infection. In conclusion, ICR mice are a viable option as a model of dermal wound infection. They accommodate two simultaneous dorsal wounds, and upon infection, these wounds follow a different pattern of resolution compared to BALB/c mice.

Antibiotic-Resistant Infections and Treatment Challenges in the Immunocompromised Host: An Update

This article reviews antibiotic resistance and treatment of bacterial infections in the growing number of patients who are immunocompromised: solid organ transplant recipients, the neutropenic host, and persons with human immunodeficiency virus and AIDS. Specific mechanisms of resistance in both gram-negative and gram-positive bacteria, as well as newer treatment options are addressed elsewhere and are only briefly discussed in the context of the immunocompromised host.

Severe Sepsis Mimicking Primary Nonfunction Following Liver Transplantation: Normothermic Machine Perfusion Is a Potential Environment for Bacterial Overgrowth and Transmission From Donor to Recipient. A Case Report

Primary nonfunction (PNF) in the early postoperative period following liver transplantation is fatal if not managed appropriately with early retransplantation. Severe early allograft dysfunction can mimic PNF. The identification of treatable causative factors such as sepsis, hepatic artery, or portal vein thrombosis is essential to distinguish it from PNF, and their early management may avoid the need for retransplantation. In this article, we describe a case of sepsis-induced severe liver dysfunction from a contaminated graft perfused with normothermic machine perfusion (NMP), which presented in a manner similar to PNF. The implications of graft contamination are poorly described. To our knowledge, this is the first report of bacterial contamination of a graft that underwent NMP and subsequently caused severe sepsis in the recipient. The conditions created with NMP may be optimal for certain micro-organisms to thrive. The role of the liver in the immune system is complex as it provides an essential barrier to enterically derived portal venous pathogens and produces numerous acute phase proteins that augment the systemic immune response. Additionally, the liver is also known to restrain harmful and excessive systemic immune responses such as those that occur with the sepsis syndrome. The relationship between bacterial graft contamination, sepsis, and graft dysfunction may be multidirectional.

Therapeutic Drug Monitoring of Meropenem and Piperacillin in Critical Illness-Experience and Recommendations from One Year in Routine Clinical Practice

Various studies have reported insufficient beta-lactam concentrations in critically ill patients. The extent to which therapeutic drug monitoring (TDM) in clinical practice can reduce insufficient antibiotic concentrations is an ongoing matter of investigation. We retrospectively evaluated routine meropenem and piperacillin measurements in critically ill patients who received antibiotics as short infusions in the first year after initiating a beta-lactam TDM program. Total trough concentrations above 8.0 mg/L for meropenem and above 22.5 mg/L for piperacillin were defined as the breakpoints for target attainment. We included 1832 meropenem samples and 636 piperacillin samples. We found that 39.3% of meropenem and 33.6% of piperacillin samples did not reach the target concentrations. We observed a clear correlation between renal function and antibiotic concentration (meropenem, r = 0.53; piperacillin, r = 0.63). Patients with renal replacement therapy or creatinine clearance (CrCl) of <70 mL/min had high rates of target attainment with the standard dosing regimens. There was a low number of patients with a CrCl >100 mL/min that achieved the target concentrations with the maximum recommended dosage. Patients with impaired renal function only required TDM if toxic side effects were noted. In contrast, patients with normal renal function required different dosage regimens and TDM-guided therapy to reach the breakpoints of target attainment.

Prevalence, Risk Factors And Treatment Of The Most Common Gram-Negative Bacterial Infections In Liver Transplant Recipients: A Review

Advances in surgical techniques and immunosuppressive agents have made solid organ transplant (Tx) an important strategy for treatment of end-stage organ failures. However, the incidence of infections following Tx due to Gram-negative pathogens is on the rise. These infections are associated with increased mortality and morbidity in patients following transplantation, including liver Tx. Thus, managing infections in liver Tx recipients is a big challenge, requiring prompt medical attention. Considering the important effect of Gram-negative bacterial infections on the outcomes of liver Tx recipients, the most prevalent Gram-negative pathogens including Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Escherichia coli will be discussed in this review.

Exploring the whole standard operating procedure for phage therapy in clinical practice

We have entered the post-antibiotic era. Phage therapy has recently been given renewed attention because bacteriophages are easily available and can kill bacteria. Many reports have demonstrated successful phage treatment of bacterial infection, whereas some studies have shown that phage therapy is not as effective as expected. In general, establishment of a standard operating procedure will ensure the success of phage therapy. In this paper, the whole operating procedure for phage therapy in clinical practice is explored and analyzed to comprehensively understand the success of using phage for the treatment of bacterial infectious disease in the future. The procedure includes the following: enrollment of patients for phage therapy; establishment of phage libraries; pathogenic bacterial isolation and identification; screening for effective phages against pathogenic bacteria; phage formulation preparation; phage preparation administration strategy and route; monitoring the efficacy of phage therapy; and detection of the emergence of phage-resistant strains. Finally, we outline the whole standard operating procedure for phage therapy in clinical practice. It is believed that phage therapy will be used successfully, especially in personalized medicine for the treatment of bacterial infectious diseases. Hopefully, this procedure will provide support for the entry of phage therapy into the clinic as soon as possible.