Etiology and microbial patterns of pulmonary infiltrates in patients with orthotopic liver transplantation

Predictive performance of Metagenomic Next Generation Sequencing in early detection of post-liver transplantation infections

Objective

To evaluate the predictive performance of metagenomic next-generation sequencing (mNGS) in identifying and predicting pulmonary infections following liver transplantation and to investigate its association with patient outcomes within the initial four-week post-transplantation period.

Methods

We retrospectively analyzed 41 liver transplant patients with suspected pulmonary infections from August 2022 to May 2023. Bronchoalveolar lavage fluid (BALF) samples were collected on the first postoperative day for metagenomic next generation sequencing (mNGS) and culture. The predictive capability of mNGS for subsequent infections was assessed by monitoring inflammatory biomarkers and comparing the detection rates with culture methods. Real-time Polymerase Chain Reaction (Rt-PCR) was used to monitor Human betaherpesvirus 5 (CMV) and Human parvovirus B19 (B19) weekly during a four-week postoperative period. Inflammatory biomarkers and blood coagulation function were evaluated on specific days throughout the first, third, fifth, and during four weeks following surgery. The study was conducted until August 2023 to evaluate the patients' prognostic survival outcome, classifying them into groups based on the mortality and survival.

Results

The analysis included a total of 41 patients, comprising 32 males and 9 females, with an average age of 52 (47, 63) years. Within one week after liver transplantation, there were 7 cases of bacterial infections, 5 cases of fungal infections, 19 cases of mixed infections, 8 cases without any infection, and 2 cases with unidentified pathogen-associated infections. mNGS successfully predicted 39 (72 %) strains of pathogens, while culture-based methods only detected 28 (52 %) strains. Among the 8 patients diagnosed as non-infected, culture methods identified positive results in 4 cases (50 %), whereas mNGS yielded positive results in 7 cases (87.5 %). The detection rates of CMV and B19 by Rt-PCR within 4 weeks after liver transplantation were 61 % and 17 %, respectively (25/41, 7/41) among the patients. During the study period, a total of 9 patients succumbed while 32 patients survived. The death group and the survival group exhibited significant differences in CRP, HGB, and INR levels at specific monitoring time points. The proportion of CMV detection in blood was significantly higher in the death group compared to the surviving group. Elevated CRP level was identified as a prognostic risk factor.

Conclusions

Despite the presence of false positives, mNGS still presents a potential advantage in predicting pulmonary infection pathogens following liver transplantation. Furthermore, the levels of CRP and CMV carrier status within four weeks post-surgery exhibit significant associations with patient survival and prognosis.

Pneumonia in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These guidelines from the AST Infectious Diseases Community of Practice review the diagnosis and management of pneumonia in the post-transplant period. Clinical presentations and differential diagnosis for pneumonia in the solid organ transplant recipient are reviewed. A two-tier approach is proposed based on the net state of immunosuppression and the severity of presentation. With a lower risk of opportunistic, hospital-acquired, or exposure-specific pathogens and a non-severe presentation, empirical therapy may be initiated under close clinical observation. In all other patients, or those not responding to the initial therapy, a more aggressive diagnostic approach including sampling of tissue for microbiological and pathological testing is warranted. Given the broad range of potential pathogens, a microbiological diagnosis is often key for optimal care. Given the limited literature comparatively evaluating diagnostic approaches to pneumonia in the solid organ transplant recipient, much of the proposed diagnostic algorithm reflects clinical experience rather than evidence-based data. It should serve as a template which may be modified according to local needs. The same holds true for the suggested empiric therapies, which need to be adapted to the local resistance patterns. Further study is needed to comparatively evaluate diagnostic and empiric treatment strategies in SOT recipients.

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.

Intensive Care of Pulmonary Complications Following Liver Transplantation

Chronic liver disease has been associated with pulmonary dysfunction both before and after liver transplantation. Post-liver transplantation pulmonary complications can affect both morbidity and mortality often necessitating intensive care during the immediate postoperative period. The major pulmonary complications include pneumonia, pleural effusions, pulmonary edema, and atelectasis. Poor clinical outcomes have been known to be associated with age, severity of liver dysfunction, and preexisting lung disease as well as perioperative events related to fluid balance, particularly transfusion and fluid volumes. Delineating each and every one of these pulmonary complications and their associated risk factors becomes paramount in guiding specific therapeutic strategies.

Causes of Hemoptysis in Renal Transplant Patients

OBJECTIVES

Hemoptysis is a symptom that can be caused by airway disease, pulmonary parenchymal disease, or pulmonary vascular disease, or it can be idiopathic. Infection is the most common cause of hemoptysis, accounting for 60% to 70% of cases. Hemoptysis is also an initial symptom of diffuse alveolar hemorrhage syndrome, although it may be absent at presentation in one-third of patients. Diffuse alveolar hemorrhage is characterized by disruption of the alveolar-capillary basement membranes because of either injury or inflammation of the arterioles, venules, or capillaries, resulting in bleeding in alveolar spaces. To date, no study in the literature has investigated the cause of hemoptysis in renal transplant patients. In this retrospective study, we aimed to investigate the causes of hemoptysis in renal recipients.

MATERIALS AND METHODS

The data included in this study were obtained from 352 renal transplant patients who were consulted by the pulmonology department regarding hemoptysis between 2011 and 2017 at Baskent University. Patient medical records were reviewed for demographic, clinical, radiographic, bronchoscopic features, and microbiology data. Immunosuppressive drugs and clinical outcome data were also noted.

RESULTS

This study included 352 renal transplant patients (139 male patients with mean age of 34.9 ± 7 years and 113 female patients with mean age of 31.1 ± 5 years). Hemoptysis was detected in 17 patients (4.8%),with 3 (0.85%) having massive hemoptysis as a result of diffuse alveolar hemorrhage syndrome. Fourteen of our patient group (4%) had pneumonia, and Aspergillus species was detected in 5 patients (1.4%). The only reason for diffuse alveolar hemorrhage was immunosuppressive agents, including sirolimus and mycophenolate mofetil.

CONCLUSIONS

Hemoptysis is an important respiratory symptom in renal transplant patients. Although community- or hospital-acquired pneumonia may result in hemoptysis, drug-induced diffuse alveolar hemorrhage and Aspergillus infection should be considered for causes in renal transplant patients.

Lower Respiratory Tract Infections

This review will focus on the infectious etiologies and more common noninfectious causes of lower respiratory tract syndromes among major immunosuppressed populations. The changing epidemiology of infections in the era of highly active antiretroviral therapy (HAART) in the case of HIV-positive patients and the impacts of both newer immune-suppressant therapies and anti-infective prophylaxis for other immunocompromised hosts will be discussed, with emphasis on diagnostic approaches and practice algorithms.

Bacterial and fungal infections in the early post-transplantation period after liver transplantation: etiologic agents and their susceptibility

OBJECTIVE

It has been reported in many studies that one of the main factors influencing morbidity and mortality in patients receiving transplants is infection after transplantation.

PATIENTS AND METHODS

The study included 190 adult patients undergoing orthotopic liver transplantation (OLT) between September 2001 and December 2007. All the patients were followed prospectively for infections from the OLT date and during the first 4 weeks after surgery. Immunosuppression consisted of steroids and tacrolimus. Antimicrobial prophylaxis included piperacillin/tazobactam, fluconazole, and selective bowel decontamination (SBD) was performed. Samples of clinical materials were investigated for microbiological cultures. The micro-organisms were cultured and identified in accordance with standard bacteriological procedures. Susceptibility testing was performed using Clinical and Laboratory Standards Institute procedures.

RESULTS

From 190 OLT recipients, 2213 clinical samples were obtained for microbiological examination. Positive cultures were found in 27.2% (n = 603) of all samples tested; 1252 strains were collected. Gram-positive bacteria were found in 64.1% (n = 802), Gram-negative bacteria were found in 31.6% (n = 396), and fungal strains were isolated in 4.3% (n = 54). Surgical site specimens (n = 1031) were obtained from 190 recipients during the first month after transplantation. Positive cultures accounted for 29.2% (n = 301) of all samples tested. Among the isolated microbial strains (n = 677), most common were Gram-positive bacteria (73.7%; n = 499). Gram-negative bacteria comprised 25.1% (n = 170). There were fungal strains in 1.2% (n = 8). There were 539 urine specimens. Positive cultures accounted for 16.7% (n = 90) of those. Among the isolated microbial strains (n = 210), most common were Gram-negative bacteria (62.4%; n = 131). Gram-positive bacteria comprised 28.6% (n = 60) and fungi 9% (n = 19). There were 549 blood specimens. Positive cultures were found in 30.6% (n = 168) of all samples tested. Among the isolated microbial strains (n = 263), most common were Gram-positive bacteria in 72.3% (n = 190); Gram-negative bacteria were found in 26.2% (n = 69), and fungal strains were isolated in 1.5% (n = 4). There were 69 respiratory tract specimens. Positive cultures were found in 46.4% (n = 32) of all samples tested. Among the isolated microbial strains (n = 84), most common were Gram-positive bacteria (51.2%; n = 43); Gram-negative bacteria comprised 27.4% (n = 23) and fungi 21.4% (n = 18).

CONCLUSIONS

(1) Surgical site samples were predominated samples after LTx. (2) Our study showed Gram-positive bacteria were 64.1% (n = 802), Gram-negative bacteria, 31.6% (n = 396) and fungal strains isolated in 4.3% (n = 54). (3) The increased proportion of isolates of multi-drug-resistant bacterial strains (methicillin resistant coagulase negative Staphylococcus, vancomycin-resistant Enterococcus, high-level aminoglycoside resistance, and extended- spectrum β-lactamase). (4) These data indicate strict cooperation infection control procedures in these patients.

Importance of radiological detection of early pulmonary acute complications of liver transplantation: analysis of 259 cases

PURPOSE

Pulmonary complications are common causes of morbidity and mortality after orthotopic liver transplantation (OLT) and consist of atelectasis, pleural effusion, pulmonary oedema, adult respiratory distress syndrome (ARDS) and pneumonia. The aim of this paper is to describe the incidence of pulmonary complications after OLT during the first postoperative week and to evaluate the informative value of the chest X-ray (CXR) in clinical practice.

MATERIALS AND METHODS

Patients who underwent OLT at the Ancona Transplant Centre between August 2005 and August 2012 were included in this retrospective study. The CXR and, if performed, the thoracic computed tomography (TCT) scans performed during the first 7 postoperative days were reviewed, and the radiological findings for atelectasis, pleural effusion, pulmonary oedema, ARDS and pneumonia were independently assessed and quantified by two radiologists according to the Fleischner Society criteria. Cases of pneumothorax after thoracentesis were assessed. Development of pneumonia was defined as the simultaneous presence of positive CXR or TCT and positive serological or fluid samples and clinical symptoms; the prevalence of infectious agents was assessed. The radiological reports produced in the clinical setting were compared with the findings.

RESULTS

Among 259 patients included, atelectasis was observed in 227 patients (87.6 %); pleural effusion in 250 (96.5 %); pulmonary oedema in 204 (78 %); ARDS in seven patients (2.6 %); and pneumothorax in 37 patients (14 %). Pneumonia occurred in 32 cases (12.3 %). Pulmonary oedema was underestimated in the radiological reports in 104 cases (40 %).

CONCLUSIONS

Knowledge about postoperative pulmonary complications and collaboration between the radiologist and clinician are essential for improving the management of OLT recipients.

[Nosocomial infection in patients receiving a solid organ transplant or haematopoietic stem cell transplant]

Bacterial infections are the most common infections in solid organ transplant recipients. These infections occur mainly in the first month after transplantation and are hospital-acquired. Nosocomial infections cause significant morbidity and are the most common cause of mortality in this early period of transplantation. These infections are caused by multi-drug resistant (MDR) microorganisms, mainly Gram-negative enterobacteria, non-fermentative Gram-negative bacilli, enterococci, and staphylococci. The patients at risk of developing nosocomial bacterial infections are those previously colonized with MDR bacteria while on the transplant waiting list. Intravascular catheters, the urinary tract, the lungs, and surgical wounds are the most frequent sources of infection. Preventive measures are the same as those applied in non-immunocompromised, hospitalized patients except in patients at high risk for developing fungal infection. These patients need antifungal therapy during their hospitalization, and for preventing some bacterial infections in the early transplant period, patients need vaccinations on the waiting list according to the current recommendations. Although morbidity and mortality related to infectious diseases have decreased during the last few years in haematopoietic stem cell transplant recipients, they are still one of the most important complications in this population. Furthermore, as occurs in the general population, the incidence of nosocomial infections has increased during the different phases of transplantation. It is difficult to establish general preventive measures in these patients, as there are many risk factors conditioning these infections. Firstly, they undergo multiple antibiotic treatments and interventions; secondly, there is a wide variability in the degree of neutropenia and immunosuppression among patients, and finally they combine hospital and home stay during the transplant process. However, some simple measures could be implemented to improve the current situation.

Diagnostic bronchoscopy in solid-organ and hematopoietic stem cell transplantation

Fiberoptic bronchoscopy is a valuable diagnostic tool in solid-organ and hematopoietic stem cell transplant recipients presenting with a range of pulmonary complications. This article provides a comprehensive overview of the utility and potential adverse effects of diagnostic bronchoscopy for transplant recipients. Recommendations are offered on the selection of patients, the timing of bronchoscopy, and the samples to be obtained across the spectrum of suspected pulmonary complications of transplantation. Based on review of the literature, the authors recommend early diagnostic bronchoscopy over empiric treatment in transplant recipients with evidence of certain acute, subacute, or chronic pulmonary processes. This approach may be most critical when an underlying infectious etiology is suspected. In the absence of prompt diagnostic information on which to base effective treatment, the risks associated with empiric antimicrobial therapy, including medication side effects and the development of antibiotic resistance, compound the potential harm of delaying targeted management.

Pulmonary complications after elective liver transplantation-incidence, risk factors, and outcome

After liver transplantation (LT), postoperative pulmonary complications (PPC) occur in approximately 35% to 50% of the recipients. Among these PPC, pneumonia is the most frequently encountered. Pulmonary dysfunction has also been widely reported among patients awaiting LT. The links between this dysfunction and PPC have not been clearly established. In this present cohort study, we evaluated the incidence and profile of post-LT pneumonia and identified potential preoperative risk factors.

METHODS

The postoperative clinical course of 212 liver transplant recipients between January 2008 and April 2010 was analyzed. These patients were treated in a single intensive care unit and received standardized postoperative care.

RESULTS

During the postoperative period, 47 (22%) patients developed pneumonia, of whom 20 (43%) developed respiratory failure requiring mechanical ventilation. Univariate analysis showed that several preoperative factors (age of recipient, model for end-stage liver disease score, indication for LT, platelet count, and restrictive lung pattern revealed by preoperative pulmonary function tests) and the transfusion (blood units and fresh frozen plasma units) during the operative period were associated with pneumonia. Using multivariate analysis by logistic regression, only a restrictive lung pattern (odds ratio=3.14; 95% confidence interval, 1.51-6.51; P=0.002) and the international normalized ratio measured prior LT (OR=4.95; 95% confidence interval, 1.86-8.59; P=0.0004) were independent predictors of pneumonia after LT.

CONCLUSION

Pneumonia is common among patients undergoing LT and is a major cause of morbidity. A restrictive pattern on preoperative pulmonary testing and a higher international normalized ratio measured prior LT were associated with more risk of postoperative pneumonia.

Radiological spectrum of pulmonary infections in patients post solid organ transplantation

Pneumonia remains an important source of morbidity and mortality in transplant recipients. Since clinical findings are nonspecific and cultures may be time-consuming, imaging plays an important role in establishing the probable etiology of pneumonia. Plain films are used as an initial study. However, they have a limited capacity in differentiating the causative factors. HRCT is used as a problem-solving tool in patients with unclear plain film findings and/or no response to treatment. The main advantage of HRCT is a very detailed depiction of the lung parenchyma. Even though HRCT findings are not always specific, there are several sings that are more common in certain types of pneumonia. The aim of the article is to present radiological findings suggestive of a particular causative microorganism and show how they can narrow the differential diagnosis when coupled with clinical data.

Multidrug-resistant bacterial infection in solid organ transplant recipients

The most frequent complication from infection after solid organ transplantation is bacterial infection. This complication is more frequent in organ transplantation involving the abdominal cavity, such as liver or pancreas transplantation, and less frequent in heart transplant recipients. The sources, clinical characteristics, antibiotic resistance and clinical outcomes vary according to the time of onset after transplantation. Most bacterial infections during the first month post-transplantation are hospital acquired, and there is usually a high incidence of multidrug-resistant bacterial infections. The higher incidence of complications from bacterial infection in the first month post-transplantation may be associated with high morbidity. Of special interest due to their frequency are infections by S. aureus, enterococci, Gram-negative enteric and non-fermentative bacilli. Opportunistic bacterial infections may occur at any time on the posttransplant timeline, but are more frequent between months two and six, the period in which immunosuppression is higher. The most frequent bacterial species causing opportunistic infections in organ transplant recipients are Listeria monocytogenes and Nocardia spp. After month six, posttransplantation solid organ transplant patients usually develop conventional community-acquired bacterial infections, especially urinary tract infections by E. coli and S. pneumoniae pneumonia. In this article we review the clinical characteristics, epidemiology, diagnosis and prognosis of bacterial infections in solid organ transplant patients.

Etiologies, risk factors, and outcomes of bacterial pneumonia after living donor liver transplantation

The prevalence and clinical characteristics of bacterial pneumonia after living donor liver transplantation (LDLT) have not yet been elucidated. We performed a retrospective analysis of 346 LDLT recipients. Fifty patients (14.5%) experienced bacterial pneumonia after LDLT, and they had a higher short-term mortality rate (42.0%) than patients with other types of bacterial infections after LDLT. Gram-negative bacteria accounted for 84.0% of the causative pathogens. A multivariate analysis showed that preoperative diabetes (P < 0.01), United Network for Organ Sharing status 1 or 2A (P < 0.01), and an operative blood loss > 10 L (P = 0.03) were significant risk factors for bacterial pneumonia after LDLT. Post-LDLT pneumonia was associated with the following post-LDLT events: the prolonged use of mechanical ventilation (≥3 days), a prolonged stay in the intensive care unit (≥7 days), the creation of a tracheostomy, primary graft dysfunction, the use of mycophenolate mofetil, and the need for renal replacement therapy. Among patients with bacterial pneumonia, the mortality rate was higher for patients with delayed-onset pneumonia, which occurred at least 10 days after transplantation (n = 15), and it was significantly associated with graft dysfunction. A combination of broad-spectrum antibiotics and aminoglycosides provided cover for most gram-negative bacteria except Stenotrophomonas maltophilia, which was associated with a longer period of mechanical ventilation and was resistant to commonly used broad-spectrum antibiotics. Delayed-onset bacterial pneumonia is a serious type of bacterial infection after LDLT and is frequently associated with graft dysfunction. The multidrug resistance of S. maltophilia is an issue that needs to be addressed.

Early-onset pneumonia after liver transplantation: microbiological findings and therapeutic consequences

Early-onset hospital-acquired pneumonia (E-HAP) is one of the leading causes of sepsis and mortality after liver transplantation (LT). The appropriate antimicrobial therapy is crucially important for surviving sepsis in this context. The aim of this study was to analyze microbiological findings, associated factors, and optimal antibiotic regimens for E-HAP after LT. Patients demonstrating E-HAP in a single-center cohort of 148 LT recipients were prospectively detected. The diagnosis of pneumonia relied on a combination of supportive clinical findings and a positive culture of a lower respiratory tract sample. E-HAP was considered present if pneumonia occurred within 6 days of intensive care unit (ICU) admission after LT. Twenty-three patients (15.5%) developed E-HAP, which were caused by 36 pathogens (61.1% were gram-negative bacilli, and 33.3% were classified as hospital-acquired). For patients who developed E-HAP, the duration of mechanical ventilation and the ICU stay were significantly longer. Despite a trend toward higher mortality at any time in the E-HAP group, there was no significant difference in mortality between patients with E-HAP and patients without E-HAP. Lactatemia, vasopressor requirements, Simplified Acute Physiology Score II (SAPS II) score on ICU admission, and mechanical ventilation lasting more than 48 hours after LT were associated with E-HAP. Combinations of broad-spectrum β-lactams and aminoglycosides were active against more than 91% of the encountered pathogens. However, antibiotic de-escalation was possible in more than one-third of cases after identification of the pathogens. In conclusion, E-HAP after LT is a severe condition that appears to be influenced by physiological derangements induced by the surgery, such as lactatemia, vasopressor requirements, and mechanical ventilation requirements, as well as the postoperative SAPS II score. At the time of treatment initiation, an antimicrobial regimen usually proposed for late-onset pneumonia should be followed.

Donor mannose-binding lectin deficiency increases the likelihood of clinically significant infection after liver transplantation

BACKGROUND

Mannose-binding lectin (MBL) is an important mediator of innate immunity and is synthesized primarily by the liver. Low MBL levels are common, are due primarily to polymorphisms in the gene encoding MBL (MBL2), and are associated with an increased risk of infection, particularly when immunity is compromised. We report a large, retrospective study that examined the association between MBL status and clinically significant infection following orthotopic liver transplantation.

METHODS

One hundred two donor-recipient orthotopic liver transplantation pairs were studied. Five polymorphisms in the promoter and coding regions of MBL2 were examined. MBL levels were measured, using the mannan-binding and C4-deposition assays, in serum samples obtained before and after transplantation. Associations between MBL status, as assessed by serum MBL levels and MBL2 genotype, and time to first clinically significant infection (CSI) after transplantation were examined in survival analysis with consideration of competing risks.

RESULTS

The median duration of follow-up after orthotopic liver transplantation was 4 years. Thirty-six percent of recipients developed CSI after transplantation. The presence of MBL2 coding mutations in the donor was significantly associated with CSI in the recipient; the cumulative incidence function of infection was 55% in recipients of deficient livers, compared with 32% for recipients of wild-type livers (P = .002). Infection was not associated with recipient MBL2 genotype. Low MBL levels after orthotopic liver transplantation levels (mannan-binding <1 microg/mL or C4 deposition <0.2 C4 U/microL) were also associated with CSI (cumulative incidence function, 52% vs. 20%, P = .003; and cumulative incidence function, 54% vs. 24%, P = .007, respectively). In multivariate analysis, mutation in the MBL2 coding region of the donor (hazard ratio, 2.8; P = .005) and the use of cytomegalovirus prophylaxis (hazard ratio, 2.6; P = .005) were independently associated with CSI.

CONCLUSIONS

Recipients of MBL-deficient livers have almost a 3-fold greater likelihood of developing CSI and may benefit from MBL replacement.

Pulmonary and blood stream infections in adult living donor and cadaveric liver transplant patients

BACKGROUND

Infectious complications occur in approximately 50% of cadaveric liver transplant (CDLT) recipients. Living-donor liver transplantation (LDLT) is an established alternative to shorten the waiting time. Currently, the incidence of pulmonary infections after LDLT and the microbiologic causes are unknown. In the present cohort study, we compared the incidence and profiles of pulmonary and blood stream infections (BSI) between LDLT and CDLT recipients. We hypothesized a lower incidence in LDLT recipients.

METHODS

The clinical course of 55 LDLT recipients consecutively transplanted between January 2003 and December 2006 was analyzed. The 173 CDLT recipients who were transplanted in the same period served as a control group. Patients were treated in a single Intensive Care Unit, applying standardized postoperative care.

RESULTS

Mean model for end-stage liver disease score did not differ between LDLT and CDLT recipients (14.2 vs. 13.3). The overall incidence of pulmonary and BSI for both groups was 8% and 24%, respectively. Pulmonary infections were experienced by 18% of LDLT versus 5% of CDLT recipients (P=0.005) and BSI occurred in 33% of LDLT versus 21% of CDLT recipients (P=0.1).

CONCLUSIONS

In contrast to our hypothesis, LDLT recipients experienced significantly more pulmonary infections and a trend toward increased higher incidence of BSI. These findings emphasize the need for future research on the causative agents and prevention of infection in LDLT recipients. The observation that patients with pulmonary infection had a significantly reduced 1-year survival rate underscores the importance of our observations.

Pulmonary complications following adult liver transplantation

PURPOSE

Pulmonary complications frequently occur after liver transplantation, but the risk factors associated with them have not been fully determined. We therefore sought to identify risk factors for pulmonary complications among adult liver transplant recipients.

METHODS

We retrospectively reviewed the medical records of 128 consecutive adult patients who underwent 131 liver transplantations during 2001. We evaluated the incidence, time of onset, and outcome of radiographically determined pulmonary complications, as well as the factors predictive of infectious complications.

RESULTS

Postoperative chest roentgenograms detected 68 cases of pulmonary complications, including pleural effusion (n = 50), atelectasis (n = 6), pneumonia (n = 6), pulmonary edema (n = 5), and acute respiratory distress syndrome associated with pneumonia (n = 1). Of the seven patients with pneumonia, five died. On univariate analysis the risk factors predictive for pneumonia were high serum creatinine and total bilirubin, hemodialysis at the time of occurrence, and history of acute rejection and on multivariate analysis increased total bilirubin and history of acute rejection. Pulmonary complications were dependent on the medical condition at the time of occurrence rather than on the preoperative condition.

CONCLUSIONS

Although the incidence of pneumonia in liver recipients was relatively low, the mortality rate in patients who developed this complication was high. High-risk patients undergoing liver transplantation thus require early diagnosis and intensive treatment to diminish the morbidity and mortality associated with pulmonary complications.

Transplant-related immunosuppression: a review of immunosuppression and pulmonary infections

Solid organ and hematopoietic stem cell transplantation are definitive therapies for a variety of end-stage diseases. Immunosuppression has improved graft survival but leaves the patient susceptible to infectious complications. Of these, pulmonary infections are the leading cause of morbidity and mortality in the transplant recipient. Allograft rejection is mediated primarily by T cells, with B cells playing a role via antibody production. Depending on the transplant type, rejection can be hyperacute, acute, or chronic. Hyperacute rejection occurs as an immediate response to preformed antibodies to donor human leukocyte antigens. Acute cellular rejection involves recipient T-cell recognition of human leukocyte antigen molecules expressed on donor-derived, antigen-presenting cells (direct allorecognition) or presentation of donor-derived peptides by recipient antigen-presenting cells to recipient T cells (indirect allorecognition). Once the alloantigens are recognized as foreign, the activation, proliferation, and production of cytokines by T lymphocytes and other immune cells lead to the amplification of the alloimmune response. This complex process involves the generation of effector T cells, antibody production by activated B cells, and macrophage activation. Alloimmunity is facilitated by the production of many cytokines, chemokines, and other effector molecules, such as complement. The immunosuppressants involve many classes of drugs, including antibody therapies that eliminate specific groups of cells or alter signaling pathways used by effector cells. The article reviews the agents and associated infections.

Microbiologic features and outcome of pneumonia in transplanted patients

We prospectively evaluated lower respiratory tract infections in solid organ transplantation (SOT) patients to determine the microbiologic diagnosis and clinical outcomes. We diagnosed 83 cases of pneumonia, 38 of which were community acquired and 45 were nosocomial. Those with bilateral infiltrates or absence of improvement after 3 days of treatment underwent fiberoptic bronchoscopy. Bacterial pneumonia was the most frequent diagnosis and mixed infection predominated in the nosocomial group (11/45 nosocomial versus 1/38 community). Fiberoptic bronchoscopy with bronchoalveolar lavage had higher diagnostic yield in nosocomial pneumonia (77% versus 47%). Mortality differences between the 2 groups were 58% nosocomial versus 8% community-acquired infections (P < 0.001). SOT patients with nosocomial pneumonia, or those who needed mechanical ventilation, had a high mortality rate and benefits from the fiberoptic diagnostic techniques.

Fatal pneumonia caused by Panton-Valentine Leucocidine-positive methicillin-resistant Staphylococcus aureus (PVL-MRSA) transmitted from a healthy donor in living-donor liver transplantation

Severe infections are the most dangerous complications in liver transplantation and their prevention is one of the major goals. A 60-year-old Saudi-Arabian female with decompensated hepatitis C liver cirrhosis received a right-lobe liver graft from her healthy daughter. After 9 days, the patient developed a rapidly progressive necrotizing pneumonia that was fatal in spite of extracorporal lung assist. The pneumonia was due to a Panton-Valentine Leucocidine-positive (PVL) methicillin-resistant Staphylococcus aureus (MRSA), or "community-acquired" MRSA, that had not been detectable in the patient preoperatively. The same strain of PVL-MRSA could be demonstrated in the nares of the asymptomatic donor, but not of other relatives, patients, or medical staff. These findings strongly suggest transmission of PVL-MRSA from the donor to the recipient. This case demonstrates a previously unknown, and potentially fatal, risk in living-donor liver transplantation: transmission of a severe infection from a healthy donor to the recipient.

Bacterial and Mycobacterial Pneumonia in Transplant Recipients

Bacteria and myobacteria are important pulmonary pathogens in transplant recipients and are the focus of this article. Although considerable overlap exists, there are significant differences in the epidemiology and clinical presentation of these organisms in solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients. The first section of this article focuses on infections in SOT recipients (predominantly heart, liver, lung, and kidney transplant recipients), and the latter addresses these infections in HSCT recipients.

Pulmonary Complications of Transplantation: Radiographic Considerations

The aim of this article is to clarify radiographic definitions associated with common parenchymal patterns encountered in the transplant population and to discuss the most common pathologic causes responsible for each pattern. The article also touches on radiographic findings signifying complications of other intrathoracic structures, including the airways, pleural space, and mediastinum.

High-resolution computed tomography (HRCT) of lung infections in non-AIDS immunocompromised patients

Non-AIDS immunocompromised patients are susceptible to infections by a wide range of organisms. In the past several decades, advances in the treatment of cancer, organ transplantation, and immunosuppressive therapy have resulted in large numbers of patients who develop abnormalities in their immune system. Moreover, mildly impaired host immunity as it occurs in chronic debilitating illness, diabetes mellitus, malnutrition, alcoholism, advanced age, prolonged corticosteroid administration, and chronic obstructive lung disease have also been regarded as predisposing factors of pulmonary infections. Imaging plays a crucial role in the detection and management of patients with pulmonary infectious diseases. When pulmonary infection is suspected, knowledge of the varied radiographic manifestations will narrow the differential diagnosis, helping to direct additional diagnostic measures and serving as an ideal tool for follow-up examinations. Combination of pattern recognition with knowledge of the clinical setting is the best approach to pulmonary infection occurring in the immunocompromised patients.

Spectrum of pneumonia in the current era of liver transplantation and its effect on survival

OBJECTIVE

To examine the frequency and microbial pattern of pneumonia and its effect on survival in the current era of orthotopic liver transplantation (OLT).

PATIENTS AND METHODS

At the Mayo Clinic in Jacksonville, Fla, the medical records of consecutive patients who underwent their first OLT between February 1998 and January 2001 were retrospectively reviewed through the end of the first year posttransplantation.

RESULTS

Of 401 study patients, 20 developed pneumonia; estimates of incidence with corresponding 95% confidence interval (CI) at 1 and 12 months were 3% (1%-5%) and 5% (3%-7%), respectively. Pseudomonas aeruginosa was the predominant microorganism identified (in 8 of 14 patients) during the first month after transplantation. Between the second and sixth months, 2 of the 4 cases of pneumonia were due to fungal infections of Aspergillus fumigatus. Cytomegalovirus was associated with Aspergillus in 1 patient. No other viral or Pneumocystis carnil pneumonia was diagnosed. There were only 2 cases of pneumonia between 7 months and 1 year after transplantation, neither of which was fungal. Approximately 40% (95% CI, 14%-58%) of patients with pneumonia died within 1 month after diagnosis. The relative risk of mortality in the first month after onset of pneumonia was estimated to be 24 (95% CI, 10-54), which is strong evidence of increased risk of mortality with pneumonia (P<0.001).

CONCLUSIONS

Pneumonia appears to occur less often after OLT than previously reported but still has a substantial negative effect on survival. In the early period after OLT, P. aeruginosa continues to be the predominant organism causing pneumonia.

Pneumonia in the solid organ transplant patient

As the field of solid organ transplantation has grown, so has the importance of infectious complications in this select group of patients. Chronic immunosuppression compromises the natural host defenses that typically prevent lower respiratory tract infections and makes the solid organ transplant recipient especially susceptible to pneumonia. Evaluation of pneumonia in this population differs owing to the potential for opportunistic infections. Lung transplant recipients are particularly susceptible to pneumonia and pose unique diagnostic dilemmas. An understanding of the time line for the different key pathogens after transplantation aids the initial evaluation and management.

Clinical usefulness of bronchoalveolar lavage in heart transplant recipients with suspected lower respiratory tract infection

BACKGROUND

Bronchoscopy with bronchoalveolar lavage (BAL) is the recommended initial invasive diagnostic procedure when lower respiratory tract infection is suspected in solid-organ transplant recipients. In this study, we evaluated the clinical impact and safety of bronchoscopy with BAL in heart transplant recipients.

METHODS

We reviewed all 44 consecutive diagnostic bronchoscopies with BAL that were performed in 35 heart transplant recipients at Helsinki University Central Hospital between May 1988 and December 2001.

RESULTS

Bronchoscopy findings established specific microbiologic diagnoses in 18 of 44 (41%) cases, and 14 of 44 (32%) bronchoscopic findings led to changes in therapy. The diagnostic yield of bronchoscopy from 1 to 6 months after transplantation was 73%, significantly better (p = 0.002) than diagnostic yield during the first month (18%) and after 6 months (28%). Pneumocystis carinii and cytomegalovirus were the most frequently detected pathogens in the BAL fluid. Cytomegalovirus pneumonia carried a high mortality rate (44%), whereas all patients with P carinii pneumonia recovered. Fourteen episodes were diagnosed as bacterial pneumonia, but because of empiric antibiotic therapy that was started widely before bronchoscopy, a microbiologic diagnosis was established in only 1 case. However, all patients with community-acquired pneumonia responded to empiric therapy. Four cases of major complications occurred after bronchoscopy, all cardiovascular but none fatal.

CONCLUSIONS

Bronchoscopy with BAL is a useful diagnostic tool in heart transplant recipients, especially between 1 and 6 months after transplantation.

Pulmonary complications of solid organ and hematopoietic stem cell transplantation

The ability to successfully transplant solid organs and hematopoietic stem cells represents one of the landmark medical achievements of the twentieth century. Solid organ transplantation has emerged as the standard of care for select patients with severe vital organ dysfunction and hematopoietic stem cell transplantation has become an important treatment option for patients with a wide spectrum of nonmalignant and malignant hematologic disorders, genetic disorders, and solid tumors. Although advances in surgical techniques, immunosuppressive management, and prophylaxis and treatment of infectious diseases have made long-term survival an achievable goal, transplant recipients remain at high risk for developing a myriad of serious and often life-threatening complications. Paramount among these are pulmonary complications, which arise as a consequence of the immunosuppressed status of the recipient as well as from such factors as the initial surgical insult of organ transplantation, the chemotherapy and radiation conditioning regimens that precede hematopoietic stem cell transplantation, and alloimmune mechanisms mediating host-versus-graft and graft-versus-host responses. As the population of transplant recipients continues to grow and as their care progressively shifts from the university hospital to the community setting, knowledge of the pulmonary complications of transplantation is increasingly germane to the contemporary practice of pulmonary medicine.

The diagnosis of pneumonia in renal transplant recipients using invasive and noninvasive procedures

STUDY OBJECTIVES

We used invasive and noninvasive procedures to determine the causes of pneumonia in renal transplant recipients.

SUBJECTS AND METHODS

We retrospectively surveyed 565 renal transplant recipients (transplants received March 1984 to August 2001) to find those with pneumonia. Noninvasive diagnostic methods included serologic testing, and blood and sputum cultures with stains. Invasive procedures included fiberoptic bronchoscopy and percutaneous transthoracic procedures.

RESULTS

A total of 92 patients were enrolled. Of these, 71 patients had a definite etiologic diagnosis of pneumonia. The major infectious pathogens were bacterial (n = 21) and mixed bacterial infection (n = 10), Mycobacterium tuberculosis (TB) [n = 18], and fungi (n = 8). Noninvasive and invasive procedures led to the diagnosis of pneumonia in 31.5% (n = 29) and 45.6% (n = 42) of patients, respectively. Bronchoscopy was used in 64 patients, with a diagnostic yield of 38 cases (59.3%). Patients were 3.62 times more likely to contract pneumonia within 12 months of renal transplantation than they were > or =12 months thereafter (95% confidence interval, 1.33 to 9.84). Twenty-seven of the 92 patients (29.3%) died. The pneumonia mortality rate has dropped significantly since 1996 (41.8% vs 10.8%, p = 0.002).

CONCLUSION

Both invasive and noninvasive procedures are useful in the diagnosis of pneumonia, with declining mortality, in renal transplant recipients. Bacterial and mixed bacterial infection, TB, and fungal infection are the most common pathogens; cases are most likely to occur within 1 year after renal transplantation.

Pulmonary Infiltrates in the Non-HIV-Infected Immunocompromised Patient

Pulmonary complications remain a major cause of both morbidity and mortality in immunocompromised patients. When such individuals present with radiographic infiltrates, the clinician faces a diagnostic challenge. The differential diagnosis in this setting is broad and includes both infectious and noninfectious processes. Rarely are the radiographic findings classic for one disease, and most potential etiologies have overlapping clinical and radiographic appearances. In recent years, several themes have emerged in the literature on this topic. First, an aggressive approach to identifying a specific etiology is necessary; as a corollary, diagnostic delay increases the risk for mortality. Second, the evaluation of these infiltrates nearly always entails bronchoscopy. Bronchoscopy allows identification of some etiologies with certainty, and often allows for the exclusion of infectious agents even if the procedure is otherwise unrevealing. Third, early use of CT scanning regularly demonstrates lesions missed by plain radiography. Despite these advances, initial therapeutic interventions include the use of broad-spectrum antibiotics and other anti-infectives in order to ensure that the patients is receiving appropriate therapy. With the results of invasive testing, these treatments are then narrowed. Frustratingly, outcomes for immunocompromised patients with infiltrates remain poor.

Therapy of ventilator-associated pneumonia. A patient-based approach based on the ten rules of "The Tarragona Strategy"

Therapy of ventilator-associated pneumonia should be a patient-based approach focusing on some key features are listed here: early initial therapy should be based on broad-spectrum antibiotics. Empirical treatment may be targeted after direct staining and should be modified according to good-quality quantitative microbiological findings, but should never be withdrawn in presence of negative direct staining or delayed until microbiological results are available. Courses of therapy should be given at high doses according to pharmacodynamic and tissue penetration properties. Prolonging antibiotic treatment does not prevent recurrences. Methicillin-sensitive Staphylococcus aureus should be expected in comatose patients. Methicillin-resistant Staphylococcus aureus should not be expected in patients without previous antibiotic coverage. Pseudomonas aeruginosa should be covered with combination therapy. Antifungal therapy, even when Candida spp is isolated in significant concentrations, is not recommended for intubated nonneutropenic patients. Vancomycin, given at the standard doses and route of administration for the treatment of VAP caused by Gram-positive pathogens, is associated with poor outcomes. The choice of initial antibiotic should be based on the patient's previous antibiotic exposure and comorbidities, and local antibiotic susceptibility patterns, which should be updated regularly.

Liver failure, transplantation, and critical care

The management of patients for end-stage liver disease in the ICU mandates a multidisciplinary approach and intense monitoring. Orthotopic liver transplantation still remains the only definitive therapy. Given the increasing disparity between the number of potential recipients and available cadaver organs, the current challenge is to optimize outcome with the limited resource. In recent years, considerable progress has been made in developing specific and supportive medical measures. Future research should target a better understanding of mechanisms responsible for liver cell death and liver regeneration, as well as developments in xenotransplantation, hepatocyte transplantation, and liver-directed gene therapy.

Prognostic factors of non-HIV immunocompromised patients with pulmonary infiltrates

STUDY OBJECTIVES

To assess the outcome and the prognostic factors in 200 non-HIV immunocompromised patients with pulmonary infiltrates (PIs).

DESIGN

Prospective observational study.

SETTING

An 800-bed university hospital.

PATIENTS

Two hundred non-HIV immunocompromised patients (hematologic malignancies, 79 patients; hematopoietic stem cell transplants [HSCTs], 61 patients; and solid-organ transplants, 60 patients).

METHODS

Investigation of prognostic factors related to mortality using a multiple logistic regression model.

RESULTS

Specific diagnosis of the PI was obtained in 78% of the cases (infectious origin was determined in 74%). The overall mortality rate was 39% (78 of 200 patients). Patients with HSCT had the highest mortality rate (53%). A requirement for mechanical ventilation (odds ratio [OR], 28; 95% confidence interval [CI], 9 to 93), an APACHE (acute physiology and chronic health evaluation) II score of > 20 (OR, 5.5; 95% CI, 2 to 14.7), and a delay of > 5 days in establishing a specific diagnosis (OR, 3.4; 95% CI, 1.2 to 9.6) were the variables associated with mortality at the multivariate analysis. The subgroup analysis based on underlying disease confirmed the prognostic significance of these variables and the infectious etiology for the PI.

CONCLUSIONS

Mortality in immunocompromised patients is high, particularly in patients undergoing HSCT. Achieving an earlier diagnosis potentially may improve the mortality rate of these patients.

Aerobic Gram-negative Bacillary Pneumonia

Gram-negative bacilli (GNB) are a common cause of severe hospital-acquired pneumonia. Due to changes in the health care environment and selective antimicrobial pressure, these bacteria also are becoming a more common cause of pneumonia in venues outside of the traditional hospital setting and are increasingly resistant to antimicrobial agents. Risk factors for acquisition of GNB allow the clinician to efficiently identify patients who are likely to have pneumonia due to these pathogens. Available diagnostic techniques have a limited capacity to accurately detect GNB pulmonary infection. Yet, a pathogen specific diagnosis and knowledge of local resistance patterns are quintessential elements in formulating an effective treatment plan. This article reviews the epidemiologic characteristics, pathogenesis, and current management issues of GNB pneumonia.