Late respiratory infection after lung transplantation

Focus on Pneumonia After Organ Transplantation: Is There a Need for Specific Medical Care in the Emergency Department?

BACKGROUND

Pneumonia is a major cause of hospitalization and has a substantial impact on health care costs. Diagnosis and treatment of pneumonia in solid organ transplant (SOT) patients remain a challenge for clinicians in the emergency department. This study aimed to evaluate demographic features, clinical patterns, history of hospitalization, and diagnosis of adult patients after organ(s) transplantation (liver, kidney, pancreas) with severe pneumonia requiring hospitalization. The aim is to determine whether patients undergoing SOT receive or require specific care and whether they need to be prioritized.

METHOD

This was a single-center observational study of adult patients after SOT with severe pneumonia requiring hospitalization. The data set for the analysis included only patients with pneumonia as the main reason for hospitalization. The diagnosis of pneumonia was suspected based on the American Thoracic Society criteria.

RESULTS

The study revealed that the standard of care for patients with a history of SOT did not significantly differ from care provided to the non-SOT patients with pneumonia admitted to the same hospital during a 94-week period.

CONCLUSION

There were notable differences, such as post-transplant patients being transferred more quickly to the hospital ward, having longer hospital stays, and receiving antibiotics earlier than the non-SOT group.

Bacterial infections in lung transplantation

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

Divergent airway microbiomes in lung transplant recipients with or without pulmonary infection

BACKGROUND

Lung transplant (LTx) recipients are at increased risk for airway infections, but the cause of infection is often difficult to establish with traditional culture-based techniques. The objectives of the study was to compare the airway microbiome in LTx patients with and without ongoing airway infection and identify differences in their microbiome composition.

METHODS

LTx recipients were prospectively followed with bronchoalveolar lavage (BAL) during the first year after transplantation. The likelihood of airway infection at the time of sampling was graded based on clinical criteria and BAL cultures, and BAL fluid levels of the inflammatory markers heparin-binding protein (HBP), IL-1β and IL-8 were determined with ELISA. The bacterial microbiome of the samples were analysed with 16S rDNA sequencing and characterized based on richness and evenness. The distance in microbiome composition between samples were determined using Bray-Curtis and weighted and unweighted UniFrac.

RESULTS

A total of 46 samples from 22 patients were included in the study. Samples collected during infection and samples with high levels of inflammation were characterized by loss of bacterial diversity and a significantly different species composition. Burkholderia, Corynebacterium and Staphylococcus were enriched during infection and inflammation, whereas anaerobes and normal oropharyngeal flora were less abundant. The most common findings in BAL cultures, including Pseudomonas aeruginosa, were not enriched during infection.

CONCLUSION

This study gives important insights into the dynamics of the airway microbiome of LTx recipients, and suggests that lung infections are associated with a disruption in the homeostasis of the microbiome.

Management and prophylaxis of bacterial and mycobacterial infections among lung transplant recipients

Bacterial and mycobacterial infections are associated with morbidity and mortality in lung transplant recipients. Infectious complications are categorized by timing post-transplant: <1, 1–6, and >6 months. The first month post-transplant is associated with the highest risk of infection. During this period, infections are most commonly healthcare-associated, and include infections related to surgical complications. The lungs and bloodstream are common sites of infections. Common healthcare-associated organisms include methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative bacilli such as Pseudomonas aeruginosa, and Clostridioides difficile. More than 1-month post-transplant, opportunistic infections can occur. Tuberculosis occurs in 0.8–10% of lung transplant recipients which reflects variation in background prevalence. The majority of post-transplant tuberculosis stems from reactivation of untreated or undiagnosed latent tuberculosis. Most post-transplant tuberculosis occurs in the lungs and develops within a year of transplant. Non-tuberculous mycobacteria commonly colonize the lungs of lung transplant candidates and are often hard to eradicate even with prolonged courses of antimycobacterial agents. Drug interactions between antimycobacterial agents and calcineurin and mTOR inhibitors also complicates treatment post-transplant. Given that infection adversely impacts outcomes after lung transplant, and that anti-infective therapy is often less effective after transplant, infection prevention is key to long-term success. A comprehensive approach that includes pre-transplant evaluation, perioperative prophylaxis, long-term antimicrobial prophylaxis, immunization, and safer living at home and in the community, should be employed to minimize the risk of infection.

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.

Infectious complications of bronchial stenosis in lung transplant recipients

BACKGROUND

Bronchial stenosis is a known complication of lung transplantation, but there are limited data regarding whether transplant recipients with bronchial stenosis develop more infectious complications than those without bronchial stenosis.

METHODS

We conducted a retrospective single-center observational cohort study between January 1, 2011 and September 29, 2016 of 35 lung transplant recipients diagnosed with bronchial stenosis and a random sample of 35 lung transplant recipients without bronchial stenosis. Data collected included donor/recipient demographic and anatomic information, respiratory cultures, episodes of respiratory infections diagnosed using CDC-NNIS criteria, hospitalizations, and 1-year all-cause mortality. Patients were followed up to 1 year after transplant.

RESULTS

Bronchial stenosis occurred at a median of 54 days post-transplant (range 5-365 days). Bronchial stenosis patients spent more time in the hospital (87.4 vs 46.8 days, P = 0.011) and had more total hospitalizations (4.54 vs 2.37, P < 0.01) than their counterparts. The relative risk of pneumonia among cases vs controls was 4.0 (95% CI 2.2-7.3, P < 0.01); for purulent tracheobronchitis the relative risk was 3.1 (95% CI 1.6-6.1, P < 0.01). Patients with bronchial stenosis were significantly more likely to have respiratory cultures growing Staphylococcus aureus (RR 5.0; P = 0.001) and Pseudomonas aeruginosa (RR 2.1, P = 0.026). Mortality within the first year following transplant was equal in both the groups (14.3% vs 14.3%).

CONCLUSIONS

There was no significant increase in 1-year mortality for lung transplant patients who developed bronchial stenosis. However, bronchial stenosis patients had significantly higher risks of pneumonia and tracheobronchitis, and spent more days in the hospital than those without bronchial stenosis.

Infections after lung transplantation: time of occurrence, sites, and microbiologic etiologies

BACKGROUND/AIMS

Infections are major causes of both early and late death after lung transplantation (LT). The development of prophylaxis strategies has altered the epidemiology of post-LT infections; however, recent epidemiological data are limited. We evaluated infections after LT at our institution by time of occurrence, site of infections, and microbiologic etiologies.

METHODS

All consecutive patients undergoing lung or heart-lung transplantation between October 2008 and August 2014 at our institution were enrolled. Cases of infections after LT were initially identified from the prospective registry database, which was followed by a detailed review of the patients' medical records.

RESULTS

A total of 108 episodes of post-LT infections (56 bacterial, 43 viral, and nine fungal infections) were observed in 34 LT recipients. Within 1 month after LT, the most common bacterial infections were catheter-related bloodstream infections (42%). Pneumonia was the most common site of bacterial infection in the 2- to 6-month period (28%) and after 6 months (47%). Cytomegalovirus was the most common viral infection within 1 month (75%) and in the 2- to 6-month period (80%). Respiratory viruses were the most common viruses after 6 months (48%). Catheter-related candidemia was the most common fungal infection. Invasive pulmonary aspergillosis developed after 6 months. Survival rates at the first and third years were 79% and 73%, respectively.

CONCLUSIONS

Although this study was performed in a single center, we provide valuable and recent detailed epidemiology data for post-LT infections. A further multicenter study is required to properly evaluate the epidemiology of post-LT infections in Korea.