Incidence of nosocomial pneumonia and risk of recurrence after antimicrobial therapy in critically ill lung and heart-lung transplant patients

Infections in lung transplanted patients: A review

Lung transplantation can improve the survival of patients with severe chronic pulmonary disorders. However, the short- and long-term risk of infections can increase morbidity and mortality rates. A non-systematic review was performed to provide the most updated information on pathogen, host, and environment-related factors associated with the occurrence of bacterial, fungal, and viral infections as well as the most appropriate therapeutic options. Bacterial infections account for about 50% of all infectious diseases in lung transplanted patients, while viruses represent the second cause of infection accounting for one third of all infections. Almost 10% of patients develop invasive fungal infections during the first year after lung transplant. Pre-transplantation comorbidities, disruption of physical barriers during the surgery, and exposure to nosocomial pathogens during the hospital stay are directly associated with the occurrence of life-threatening infections. Empiric antimicrobial treatment after the assessment of individual risk factors, local epidemiology of drug-resistant pathogens and possible drug-drug interactions can improve the clinical outcomes.

Donor respiratory multidrug-resistant bacteria and lung transplantation outcomes

RATIONALE

Respiratory culture screening is mandatory for all potential lung transplant donors. There is limited evidence on the significance of donor multidrug-resistant (MDR) bacteria on transplant outcomes. Establishing the safety of allografts colonized with MDR bacteria has implications for widening an already limited donor pool.

OBJECTIVES

We aimed to describe the prevalence of respiratory MDR bacteria among our donor population and to test for associations with posttransplant outcomes.

METHODS

This retrospective observational study included all adult patients who underwent lung-only transplantation for the first time at King Faisal Specialist Hospital & Research Centre in Riyadh from January 2015 through May 2022. The study evaluated donor bronchoalveolar lavage and bronchial swab cultures.

MAIN RESULTS

Sixty-seven of 181 donors (37%) had respiratory MDR bacteria, most commonly MDR Acinetobacter baumannii (n = 24), methicillin-resistant Staphylococcus aureus (n = 18), MDR Klebsiella pneumoniae (n = 8), MDR Pseudomonas aeruginosa (n = 7), and Stenotrophomonas maltophilia (n = 6). Donor respiratory MDR bacteria were not significantly associated with allograft survival or chronic lung allograft dysfunction (CLAD) in adjusted hazard models. Sensitivity analyses revealed an increased risk for 90-day mortality among recipients of allografts with MDR Klebsiella pneumoniae (n = 6 with strains resistant to a carbapenem and n = 2 resistant to a third-generation cephalosporin only) compared to those receiving culture-negative allografts (25.0% versus 11.1%, p = 0.04). MDR Klebsiella pneumoniae (aHR 3.31, 95%CI 0.95-11.56) and Stenotrophomonas maltophilia (aHR 5.35, 95%CI 1.26-22.77) were associated with an increased risk for CLAD compared to negative cultures.

CONCLUSION

Our data suggest the potential safety of using lung allografts with MDR bacteria in the setting of appropriate prophylaxis; however, caution should be exercised in the case of MDR Klebsiella pneumoniae.

Prevention and Management of Infections in Lung Transplant Recipients

Anti-rejection medications are essential in preventing organ rejection amongst solid organ transplant recipients; however, these agents also cause profound immunosuppression, predisposing lung transplant recipients (LTRs) to infectious complications. The timely management including prevention, diagnosis, and treatment of such infectious complications is vital to prevent significant morbidity and mortality in solid organ transplant recipients and allograft dysfunction. LTRs are inundated with microbes that may be recognized as commensals in hosts with intact immune systems. Bacterial infections are the most common ones, followed by viral pathogens. Indications of a brewing infectious process may be subtle. Hence, the importance of adapting vigilance around isolated hints through symptomatology and signs is pivotal. Signals to suggest an infectious process, such as fever and leukocytosis, may be dampened by immunosuppressive agents. One must also be vigilant about drug interactions of antibiotics and immunosuppressive agents. Treatment of infections can become challenging, as antimicrobials can interact with immunosuppressive agents, and antimicrobial resistance can surge under antimicrobial pressure. Transplant infectious disease physicians work in concert with transplant teams to obtain specimens for diagnostic testing and follow through with source control when possible. This heavily impacts medical decisions and fosters a multidisciplinary approach in management. Furthermore, the reduction of immunosuppression, although it augments the risk of allograft rejection, is as crucial as the initiation of appropriate antimicrobials when it comes to the management of infections.

Infection with Two Multi-Drug-Resistant Organisms in Solid Organ Transplant Patients Is Associated with Increased Mortality and Prolonged Hospitalization

Background: Solid organ transplant recipients have several risk factors for peri-operative multi-drug-resistant infection: their immune system is dampened as a result of critical illness and surgical stress that may be further impaired by induction immunotherapy and broad-spectrum antibiotic prophylaxis promotes selection for resistant pathogens. Infection with multi-drug-resistant organisms (MDRO) results in morbidity and mortality for solid organ transplant recipients. Patients and Methods: To assess in-hospital mortality and hospitalization duration associated with these infections, we analyzed cross-sectional, retrospective data from the 2016 Agency for Healthcare and Quality, Healthcare Cost and Utilization Project's National Inpatient Sample. Our analysis included 31,105 index admissions records for liver, kidney, heart, lung, and pancreas transplant recipients in the United States. Outcomes were assessed by multivariable regression analysis adjusting for covariables. Results: One percent (355/29,451) of patients with diagnosis of no MDRO infections died, 3% (40/1491) with diagnosis of one MDRO infection died, and 15% (25/166) with diagnosis of two MDRO infections died. Diagnosis of one MDRO infection was associated with a 20-day increase in hospitalization duration (95% confidence interval [CI], 17-22) but not increased odds of death (odds ratio [OR], 1.2; 95% CI, 0.5-2.5). Diagnosis of two MDRO infections was associated with an increased odds of death (OR, 9.6' 95% CI, 3.3-27.9) and a 41-day increase in hospitalization duration (95% CI, 34-49). Conclusions: Strategies to decrease peri-operative MDRO infection may improve survival and decrease duration of hospitalization for solid organ transplant patients.

Worldwide clinical practices in perioperative antibiotic therapy for lung transplantation

Background

Infection is the most common cause of mortality within the first year after lung transplantation (LTx). The management of perioperative antibiotic therapy is a major issue, but little is known about worldwide practices.

Methods

We sent by email a survey dealing with 5 daily clinical vignettes concerning perioperative antibiotic therapy to 180 LTx centers around the world. The invitation and a weekly reminder were sent to lung transplant specialists for a single consensus answer per center during a 3-month period.

Results

We received a total of 99 responses from 24 countries, mostly from Western Europe (n = 46) and the USA (n = 34). Systematic screening for bronchial recipient colonization before LTx was mostly performed with sputum samples (72%), regardless of the underlying lung disease. In recipients without colonization, antibiotics with activity against gram-negative bacteria resistant strains (piperacillin / tazobactam, cefepime, ceftazidime, carbapenems) were reported in 72% of the centers, and antibiotics with activity against methicillin-resistant Staphylococcus aureus (mainly vancomycin) were reported in 38% of the centers. For these recipients, the duration of antibiotics reported was 7 days (33%) or less (26%) or stopped when cultures of donor and recipients were reported negatives (12%). In recipients with previous colonization, antibiotics were adapted to the susceptibility of the most resistant strain and given for at least 14 days (67%).

Conclusion

Practices vary widely around the world, but resistant bacterial strains are mostly targeted even if no colonization occurs. The antibiotic duration reported was longer for colonized 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.

Microbiological findings in bronchoalveolar lavage fluid from lung transplant patients in Sweden

Background

Lung transplant patients experience a high risk of airway infections and microbial colonization of the lung due to constant exposure to the environment through inhaled microorganisms, denervation, reduced ciliary transport, and decreased cough.

Methods

In this nationwide prospective study on Swedish lung transplant patients, we evaluated the microbiological panorama of bacteria, fungi, and virus found in bronchoalveolar lavage fluid (BALF) obtained the first year after lung transplantation (LTx). Differences in microbiological findings depending of concomitant signs of infection and background factors were assessed.

Results

A total of 470 bronchoscopies from 126 patients were evaluated. Sixty‐two percent (n = 293) of BALF samples had positive microbiological finding(s). Forty‐six percent (n = 217) had bacterial growth, 29% (n = 137) fungal growth, and 9% (n = 43) were positive in viral PCR. In 38% of BALF samples (n = 181), a single microbe was found, whereas a combination of bacteria, fungi or virus was found in 24% (n = 112) of bronchoscopies. The most common microbiological findings were Candida albicans, Pseudomonas aeruginosa and coagulase negative Staphylococcus (in 42 (33%), 36 (29%), and 25 (20%) patients, respectively). Microbiological findings were similar in BALF from patients with and without signs of lung infection and the frequency of multidrug resistant (MDR) bacteria was low. No significant association was found between background factors and time to first lung infection.

Conclusion

This study gives important epidemiologic insights and reinforces that microbiological findings have to be evaluated in the light of clinical symptoms and endobronchial appearance in the assessment of lung infections in lung transplant patients.

Morbidity and mortality related to pneumonia and TRACHEOBRONCHITIS in ICU after lung transplantation

Background

Bacterial respiratory infections (BRI) are major complications contributing to increased morbidity and mortality after lung transplantation (LT). This study analyzed epidemiology and outcome of 175 consecutive patients developing BRI in ICU after LT between 2006 and 2012.

Methods

Three situations were described: colonization determined in donors and recipients, pneumonia and tracheobronchitis during the first 28 postoperative days. Severity score, demographic, bacteriologic and outcome data were collected.

Results

26% of donors and 31% of recipients were colonized. 92% of recipients developed BRI, including at least one episode of pneumonia in 19% of recipients. Only 21% of recipients developed BRI with an organism cultured from the donor’s samples, while 40% of recipients developed BRI with their own bacteria cultured before LT. Purulent sputum appears to be an important factor to discriminate tracheobronchitis from pneumonia. When compared to patients with tracheobronchitis, those with pneumonia had longer durations of mechanical ventilation (13 [3–27] vs 3 [29], p = 0.0005) and ICU stay (24 [16–34] vs 14 [9-22], p = 0.002). Pneumonia was associated with higher 28-day (11 (32%) vs 9 (7%), p = 0.0004) and one-year mortality rates (21 (61%) vs 24 (19%), p ≤ 0.0001).

Conclusions

These data confirm the high frequency of BRI right from the early postoperative period and the poor prognosis of pneumonia after LT.

Risks and Epidemiology of Infections After Lung or Heart–Lung Transplantation

Nowadays, lung transplantation is an established treatment option of end-stage pulmonary parenchymal and vascular disease. Post-transplant infections are a significant contributor to overall morbidity and mortality in the lung transplant recipient that, in turn, are higher than in other solid organ transplant recipients. This is likely due to several specific factors such as the constant exposure to the outside environment and the colonized native airway, and the disruption of usual mechanisms of defense including the cough reflex, bronchial circulation, and lymphatic drainage. This chapter will review the common infections that develop in the lung or heart–lung transplant recipient, including the general risk factors for infection in this population, and specific features of prophylaxis and treatment for the most frequent bacterial, viral, and fungal infections. The effects of infection on lung transplant rejection will also be discussed.

Alveolar and serum concentrations of imipenem in two lung transplant recipients supported with extracorporeal membrane oxygenation

Venovenous extracorporeal membrane oxygenation (ECMO) is increasingly used in patients with respiratory failure who fail conventional treatment. Postoperative pneumonia is the most common infection after lung transplantation (40%). Imipenem is frequently used for empirical treatment of nosocomial pneumonia in the intensive care unit. Nevertheless, few data are available on the impact of ECMO on pharmacokinetics, and no data on imipenem dosing during ECMO. Currently, no guidelines exist for antibiotic dosing during ECMO support. We report the cases of 2 patients supported with venovenous ECMO for refractory acute respiratory distress syndrome following single lung transplantation for pulmonary fibrosis, treated empirically with 1 g of imipenem intravenously every 6 h. Enterobacter cloacae was isolated from the respiratory sample of Patient 1 and Klebsiella pneumoniae was isolated from the respiratory sample of Patient 2. Minimum inhibitory concentrations of the 2 isolated strains were 0.125 and 0.25 mg/L, respectively. Both patients were still alive on day 28. This is the first report, to our knowledge, of imipenem concentrations in lung transplantation patients supported with ECMO. This study confirms high variability in imipenem trough concentrations in patients on ECMO and with preserved renal function. An elevated dosing regimen (4 g/24 h) is more likely to optimize drug exposure, and therapeutic drug monitoring is recommended, where available. Population pharmacokinetic studies are indicated to develop evidence-based dosing guidelines for ECMO patients.

Ventilator-associated respiratory infection following lung transplantation

The medical records of 170 adult patients who underwent lung transplantation between January 2010 and December 2012 were reviewed to assess the incidence, causative organisms, risk factors and outcomes of post-operative pneumonia and tracheobronchitis. 20 (12%) patients suffered 24 episodes of ventilator-associated pneumonia. The condition was associated with mean increases of 43 days in mechanical ventilation and of 35 days in hospital stay, and significantly higher hospital mortality (OR 9.0, 95% CI 3.2-25.1). Pseudomonas aeruginosa (eight out of 12 patients were multidrug-resistant) was the most common pathogen, followed by Enterobacteriaceae (one out of five patients produced extended-spectrum β-lactamases). Gastroparesis occurred in 55 (32%) patients and was significantly associated with pneumonia (OR 6.2, 95% CI 2.2-17.2). Ventilator-associated tracheobronchitis was associated with a mean increase of 28 days in mechanical ventilation and 30.5 days in hospital stay, but was not associated with higher mortality (OR 1.2, 95% CI 0.4-3.2). Pseudomonas aeruginosa (six out of 16 patients were multidrug resistant) was the most common pathogen, followed by Enterobacteriaceae (three out of 14 patients produced extended-spectrum β-lactamase). Patients with gastroparesis also had more episodes of ventilator-associated tracheobronchitis (40% versus 12%, p<0.001). In conclusion, ventilator-associated pneumonia following lung transplantation increased mortality. Preventing gastroparesis probably decreases the risk of pneumonia and tracheobronchitis. Multidrug-resistant bacteria frequently cause post-lung-transplantation pneumonia and tracheobronchitis.