Acinetobacter baumanniiinfection in solid organ transplant recipients

Challenges of Antimicrobial Resistance and Stewardship in Solid Organ Transplant Patients

Purpose of Review

Without effective antimicrobials, patients cannot undergo transplant surgery safely or sustain immunosuppressive therapy. This review examines the burden of antimicrobial resistance in solid organ transplant recipients and identifies opportunities for antimicrobial stewardship.

Recent Findings

Antimicrobial resistance has been identified to be the leading cause of death globally. Multidrug-resistant pathogens are associated with significant morbidity and mortality in transplant recipients. Methicillin-resistant S. aureus affects liver and lung recipients, causing bacteremia, pneumonia, and surgical site infections. Vancomycin-resistant enterococci is a nosocomial pathogen primarily causing bacteremia in liver recipients. Multidrug-resistant Gram-negative pathogens present urgent and serious threats to transplant recipients. Extended-spectrum beta-lactamase-producing E. coli and K. pneumoniae commonly cause bacteremia and intra-abdominal infections in liver and kidney recipients. Carbapenemase-producing Enterobacterales, mainly K. pneumoniae, are responsible for infections early-post transplant in liver, lung, kidney, and heart recipients. P. aeruginosa and A. baumannii continue to be critical threats. While there are new antimicrobial agents targeting resistant pathogens, judicious prescribing is crucial to minimize emerging resistance. The full implications of the COVID-19 global pandemic on antimicrobial resistance in transplant recipients remain to be understood. Currently, there are no established standards on the implementation of antimicrobial stewardship interventions, but strategies that leverage existing antimicrobial stewardship program structure while tailoring to the needs of transplant recipients may help to optimize antimicrobial use.

Summary

Clinicians caring for transplant recipients face unique challenges tackling emerging antimcirobial resistance. Coordinated antimicrobial stewardship interventions in collaboration with appropriate expertise in transplant and infectious diseases may mitigate against such threats.

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.

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.

Infections due to multidrug-resistant organisms following heart transplantation: Epidemiology, microbiology, and outcomes

BACKGROUND

Infections secondary to multidrug-resistant organisms (MDRO) have emerged as a growing problem in solid organ transplantation (SOT). Most of the published data on MDRO infections in SOT pertains to abdominal organ transplantation and data specific to heart transplantation (HT) are limited.

METHODS

This is a retrospective review of HT recipients at our institution from 2011 to 2016; with the aim to investigate the epidemiology, microbiologic spectrum, and outcomes in patients with post-HT MDRO infections, classified as multidrug-resistant (MDR), extensively drug-resistant (XDR), and pandrug-resistant (PDR) using standardized definitions.

RESULTS

Of the 149 HT recipients, 82 episodes of bacterial infection were seen in 46 patients (31%) in the year following HT. Thirty (37%) were due to MDR pathogens and 13 (16%) were XDR. The most common gram-negative MDR pathogens were extended-spectrum beta-lactamase (ESBL) Escherichia coli and Klebsiella pneumoniae; while XDR pathogens were most commonly Pseudomonas aeruginosa followed by carbapenem-resistant Klebsiella pneumoniae. Majority of infection episodes were bloodstream (54, 66%) followed by pulmonary infection (20, 24%). Within a year after transplant, HT recipients with any bacterial infection had significantly higher mortality versus those without infection; and XDR infections were associated with a 26-fold greater hazard of death on average compared to those without infection (adjusted HR, 26.1; 95% CI, 6.4-107.0; P < .001). There were no PDR infections.

CONCLUSION

Bacterial infections were a significant predictor of 1-year post-HT mortality, which was highest among those with XDR infections. This study highlights the burden of MDRO infections in HT recipients and identifies an area of future research.

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.

Is hospital-acquired pneumonia different in transplant recipients?

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are serious complications in transplant patients. The aim of this review is to summarize the evidence regarding nosocomial pneumonia in transplant recipients, including HAP in non-ventilated patients and VAP, and to identify future directions for improvement.A comprehensive literature search in the PubMed/MEDLINE database was performed. Articles written in English and published between 1990 and November 2018 were included. HAP/VAP in transplant patients usually occurs early post-transplant, particularly during neutropenia in haematopoietic stem cell transplant recipients. Bacteria are the leading cause of nosocomial pneumonia for both immunocompetent and transplant recipients, being Gram negative organisms, and especially Pseudomonas aeruginosa, highly prevalent. Multidrug-resistant bacteria are of special concern. Pneumonia in the transplant setting may be caused by opportunistic pathogens, and the differential diagnosis needs to be extended to other non-infectious complications. The most relevant opportunistic pathogens are Aspergillus fumigatus, Pneumocystis jirovecii and cytomegalovirus. Nevertheless, they are an exceptional cause of nosocomial pneumonia, and usually occur in severely immunosuppressed patients not receiving antimicrobial prophylaxis. Performing bronchoalveolar lavage may improve the rate of aetiological diagnosis, leading to a change in therapeutic management and improved outcomes. The optimal length of antibiotic therapy for bacterial HAP/VAP has not been well defined, but it should perhaps be longer than in the general population. Mortality associated with HAP/VAP is high. HAP/VAP in transplant patients is frequent and is associated with increased mortality. There is room for improvement in gaining knowledge about the management of HAP/VAP in this population.

Estimating the burden of antimicrobial resistance: a systematic literature review

Background

Accurate estimates of the burden of antimicrobial resistance (AMR) are needed to establish the magnitude of this global threat in terms of both health and cost, and to paramaterise cost-effectiveness evaluations of interventions aiming to tackle the problem. This review aimed to establish the alternative methodologies used in estimating AMR burden in order to appraise the current evidence base.

Methods

MEDLINE, EMBASE, Scopus, EconLit, PubMed and grey literature were searched. English language studies evaluating the impact of AMR (from any microbe) on patient, payer/provider and economic burden published between January 2013 and December 2015 were included. Independent screening of title/abstracts followed by full texts was performed using pre-specified criteria. A study quality score (from zero to one) was derived using Newcastle-Ottawa and Philips checklists. Extracted study data were used to compare study method and resulting burden estimate, according to perspective. Monetary costs were converted into 2013 USD.

Results

Out of 5187 unique retrievals, 214 studies were included. One hundred eighty-seven studies estimated patient health, 75 studies estimated payer/provider and 11 studies estimated economic burden. 64% of included studies were single centre. The majority of studies estimating patient or provider/payer burden used regression techniques. 48% of studies estimating mortality burden found a significant impact from resistance, excess healthcare system costs ranged from non-significance to $1 billion per year, whilst economic burden ranged from $21,832 per case to over $3 trillion in GDP loss. Median quality scores (interquartile range) for patient, payer/provider and economic burden studies were 0.67 (0.56-0.67), 0.56 (0.46-0.67) and 0.53 (0.44-0.60) respectively.

Conclusions

This study highlights what methodological assumptions and biases can occur dependent on chosen outcome and perspective. Currently, there is considerable variability in burden estimates, which can lead in-turn to inaccurate intervention evaluations and poor policy/investment decisions. Future research should utilise the recommendations presented in this review.

Trial registration

This systematic review is registered with PROSPERO (PROSPERO CRD42016037510).

Clinical Characteristics of Acinetobacter baumannii Infection in Solid-Organ Transplant Recipients

OBJECTIVES

Acinetobacter baumannii, depending on the immune status of the host, may result in one of the most serious hospital infections. Infections involving A. baumannii infection have been recently rising. However, little is known about the clinical features of A. baumannii infection in solid-organ transplant recipients. We aimed to share our clinical experiences with A. baumannii infection in our transplant recipients.

MATERIALS AND METHODS

Between 2011 and 2017, 41 solid-organ transplant patients developed A. baumannii infection at Baskent University Hospital. Medical records were reviewed, and patient demographics, microbiology results, and overall outcome data were noted.

RESULTS

Of 41 solid-organ transplant patients with A. baumannii infection, 29 were male and 12 were female patients with mean age of 47.15 ± 13.24 years. Our infection rate with A. baumannii infection was 6.1%. The most common sites of infection were deep tracheal aspirate (48.8%)and bloodstream (36.6%). Onset of infection 1 year posttransplant was identified in 58.5% of recipients. Risk factors included presence of invasive procedures (56.1%) and administration of high-dose corticosteroids for rejection 1 year before infection (68.3%). Thirty-day mortality rate was 41.5% (17/41 patients) and was not associated with the infection site, microbiological cure, clinical cure, and drug resistance in our study group.

CONCLUSIONS

Acinetobacter baumannii is an important cause of hospital-acquired infection and mortality worldwide. A major problem with A. baumannii infection is delayed initiation of appropriate antibiotic treatment and the rising numbers of extensively drug-resistant organisms. Predicting the potential risk factors, especially in the already at-risk solid-organ transplant population, has an important role in patient outcomes.

Antibiotic-Resistant Infections and Treatment Challenges in the Immunocompromised Host

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.

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.

Hospital-Associated Infections

Hospital-associated infection (HAI) in immunocompromised patients can result in high rates of morbidity and mortality. Infections caused by multidrug-resistant organisms (MDROs) are especially worrisome because of the limited choice of remaining antibiotics available when a patient becomes colonized or infected with an MDRO. It is therefore important that immunocompromised patients be cared for in an environment that limits the risk for acquiring infections. However, with healthcare being increasingly delivered in settings other than the traditional inpatient hospital wards, a bigger effort will need to be set forth to prevent or rapidly diagnose HAI. The last few years have seen a significant increase in the number of singleplex and multiplex molecular assays for the detection of many of the organisms responsible for HAI, but more is needed as infections caused by organisms like Legionella pneumophila and Aspergillus species are still diagnosed with methods that have relatively low yield and are slow to provide actionable results. Finally, the use of novel techniques for outbreak investigations will provide new information on transmission of infectious agents in healthcare settings and allow stronger, evidence-based recommendations to be developed for prevention of HAIs in the immunocompromised host.

Mouse model of colonization of the digestive tract with Acinetobacter baumannii and subsequent pneumonia

AIM

Implementing a mouse model of Acinetobacter baumannii (AB) digestive colonization and studying the propensity of an intestinal reservoir of AB to be at the origin of pneumonia.

MATERIALS & METHODS

After a disruption of the digestive flora by piperacillin-tazobactam, two multidrug-resistant AB strains were intranasally inoculated to two cohorts of ten mice daily. For each strain, five mice were rendered transiently neutropenic.

RESULTS & CONCLUSION

One strain persisted several weeks in the digestive tract, even after stopping piperacillin-tazobactam injections, leading to the hypothesis that some AB strains can authentically colonize the gut. Most of the immunocompromised mice experienced clinical signs and positive lung cultures, which were associated with positive spleen cultures, an argument in favor of bacterial translocation.

Abscess of Native Kidney Caused by Carbapenem-Resistant Acinetobacter baumannii (CRAB) in Renal Transplantation: A Case Report

BACKGROUND

Abscess of native kidney is a rare postoperative event after renal transplantation. This report describes a case of back pain, fever and pyuria caused by carbapenem-resistant Acinetobacter baumannii (CRAB) in a patient who underwent renal-transplantation.

CASE REPORT

A 40-year-old man, presenting with hypertension and renal failure, underwent renal transplantation 1 month previously. He developed sudden intense back pain and fever (39°C). There was normal blood flow in graft kidney but there were the swelling and cyst of right native kidney. We aspirated the pus in native kidney and performed the native nephrectomy. The carbapenem-resistant Acinetobacter baumannii (CRAB) was isolated as in pus and native kidney. We performed the tigecyline monotherapy during 3 weeks. He recovered without complication after treatment.

CONCLUSIONS

To our knowledge, no report in the literature to date describes abscess in native kidney secondary to CRAB in a renal transplant. Infections caused by CRAB have become critical for immunosuppressed patients. The presence of complication greater risk, by an organism whose pathogenicity and virulence are not yet elucidated should determine an aggressive empirical antimicrobial therapy.

Lung Transplantation in a Multidrug-Resistant Gram-Negative Acinetobacter Baumannii-Colonized Patient: A Case Report

Colonization or infection with various pathogens is frequently found in patients listed for lung transplantation. We describe a case of a 50-year-old woman with α-1-antitrypsin deficiency, which was listed for double-lung transplantation, with multidrug-resistant gram-negative Acinetobacter baumannii (MRGN4-Ab) skin colonization. Transplantation was successfully performed. Colistin (Polymyxine E) was administered intravenously and through inhalation in the first month. MRGN4-Ab was still detectable in skin swabs without evidence of infection. After good recovery and clinical inapparence, the patient was discharged 2 months after transplantation.

The Distribution, Drug Resistance, and Clinical Characteristics of Acinetobacter baumannii Infections in Solid Organ Transplant Recipients

OBJECTIVE

Acinetobacter baumannii has become a major problem among solid organ transplant (SOT) recipients. The aim of this study was to investigate the distribution, drug resistance, and clinical characteristics of A baumannii infections in SOT recipients.

METHODS

We retrospectively identified 78/1,850 (4.2%) SOT recipients who developed A baumannii infections from January 1, 2003, to April 1, 2015, and evaluated the distribution, drug resistance, and clinical characteristics of these infections.

RESULTS

Over the study period, 101 episodes of A baumannii infection occurred in 78 SOT recipients, with respiratory tract (37.6%) and blood (35.6%) as the most common sites of infection. Fifty-six episodes of A baumannii infection were accompanied with a serum creatinine level of >1.5 mg/dL. Multidrug resistance (MDR) or extensive drug resistance (XDR) occurred in 83.2%. Antibiotic resistance rate of all A baumannii to 8 of 9 antibiotics investigated was >50%. Seventy-eight percent of A baumannii were carbapenem-resistant. All but one A baumannii isolates tested against polymyxin B were susceptible. There were 40 (51.3%) overall in-hospital deaths and 31 (39.7%) infection-related deaths.

CONCLUSIONS

A baumannii infections are associated with high morbidity and mortality in SOT recipients, and MDR or XDR is common. Prevention measures are essential, and combination therapy of antibiotics are needed to improve the outcomes of SOT recipients with A baumannii infections.

Predictors of mortality in solid-organ transplant recipients with infections caused by Acinetobacter baumannii

Acinetobacter baumannii can cause a serious infection in solid-organ transplant (SOT) recipients, and more data on A. baumannii infection is needed. We sought to investigate the epidemiology and distribution of A. baumannii isolates in SOT recipients. We also investigated the risk factors for overall in-hospital mortality and infection-related 30-day mortality using multivariate logistic regression analysis. A double-center retrospective study of SOT recipients who were infected with A. baumannii between January 2003 and January 2015 was conducted. A total of 71 individuals developed 93 episodes of A. baumannii infection, with a mean age of 44.5 years (44.5±11.9 years). Ninety percent of recipients had nosocomial origin A. baumannii infection, with the bloodstream as the most common site of infection (32.4%). Septic shock developed in 23.9% (17 of 71) of all recipients with A. baumannii infection. Morbidity and mortality rates of A. baumannii infections were high in SOT recipients. The incidence rate of A. baumannii infection in SOT recipients was 3.9% (71 of 1,821). Overall in-hospital mortality and infection-related 30-day mortality were 53.5% (38 of 71) and 40.8% (29 of 71), respectively. Risk factors independently associated with overall in-hospital mortality were mechanical ventilation at onset of A. baumannii infection (odds ratio [OR] 6.29, 95% confidence interval [CI] 1.48-26.85; P=0.013), liver or liver-kidney transplantation (OR 15.33, 95% CI 1.82-129.18; P=0.012), and late-onset A. baumannii infection (OR 7.61, 95% CI 1.07-54.36; P=0.043). A platelet count <50,000/mm(3) (OR 12.76, 95% CI 1.28-126.81; P=0.030) and mechanical ventilation at onset of A. baumannii infection (OR 189.98, 95% CI 13.23-2,728.81; P<0.001) were identified as independent risk factors for infection-related 30-day mortality. In conclusion, the morbidity and mortality rates of A. baumannii infections were high in SOT recipients. Mechanical ventilation at onset of A. baumannii infection was associated with higher overall in-hospital mortality and infection-related mortality. For overall in-hospital mortality, liver or liver-kidney transplantation and late-onset A. baumannii infection, and for infection-related mortality, thrombocytopenia were also risk factors, respectively.

Toll-Like Receptor 9 Contributes to Defense against Acinetobacter baumannii Infection

Acinetobacter baumannii is a common nosocomial pathogen capable of causing severe diseases associated with significant morbidity and mortality in impaired hosts. Pattern recognition receptors, such as the Toll-like receptors (TLRs), play a key role in pathogen detection and function to alert the immune system to infection. Here, we examine the role for TLR9 signaling in response to A. baumannii infection. In a murine model of A. baumannii pneumonia, TLR9(-/-) mice exhibit significantly increased bacterial burdens in the lungs, increased extrapulmonary bacterial dissemination, and more severe lung pathology compared with those in wild-type mice. Following systemic A. baumannii infection, TLR9(-/-) mice have significantly increased bacterial burdens in the lungs, as well as decreased proinflammatory cytokine and chemokine production. These results demonstrate that TLR9-mediated pathogen detection is important for host defense against the opportunistic pathogen Acinetobacter baumannii.