Bacterial Infections During Hospital Stay and Their Impact on Mortality After Lung Transplantation: A Single-Center Study

Respiratory infections in lung transplant recipients

PURPOSE OF REVIEW

Morbidity and mortality rates after lung transplantation still remain higher than after other forms of solid organ transplantation, primarily due to a higher risk of infections and the development of chronic lung allograft dysfunction. Thus, a tiered approach highlighting the most significant respiratory pathogens including common opportunistic infections along with diagnostic, treatment and prevention strategies, including vaccination and prophylaxis is needed.

RECENT FINDINGS

The need for intense immunosuppressive therapy to prevent rejection, coupled with the transplanted lung's constant exposure to environment and impaired local defence mechanisms leads to frequent infections. Viral and bacterial infections are most frequent while fungal infections mainly involve the tracheobronchial tract but may be fatal in case of disseminated disease. Some infectious agents are known to trigger acute rejection or contribute to chronic allograft dysfunction. Invasive testing in the form of bronchoscopy with bronchoalveolar lavage is standard and increasing experience in point of care testing is gained to allow early preemptive therapy.

SUMMARY

Timely diagnosis, treatment, and ongoing monitoring are essential, but this can be difficult due to the wide variety of potential pathogens.

Pulmonary bacterial infection after lung transplantation: risk factors and impact on short-term mortality

OBJECTIVE

To explore the risk factors for pulmonary bacterial infection (PBI) after lung transplantation (LTX) and to evaluate the impact of PBI on short-term postoperative mortality.

METHODS

We retrospectively analyzed data on 549 recipients who underwent LTX at the Affiliated Wuxi People's Hospital of Nanjing Medical University, China, between January 2018 and December 2021. The risk factors for PBI after LTX were explored by univariate analysis and multivariate logistic regression. Cox proportional hazards regression models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of one-, two-, and three-year mortality. Subgroup analysis was performed by the time of postoperative PBI (≤7 days or 8-30 day after surgery).

RESULTS

The incidence of postoperative PBI in 549 recipients was 82.70% (454/549). Preoperative history of infections with multidrug-resistant bacteria (OR 12.34, 95% CI 1.69-1572.39), Acinetobacter baumannii infection in donor (OR 3.08, 95% CI 1.26-9.66), and longer cold ischemia time (OR 1.16, 95% CI 1.03-1.32) were risk factors for postoperative PBI. Postoperative PBI was associated with one-year (HR 1.80, 95% CI 1.09-2.96), two-year (HR 1.91, 95% CI 1.20-3.04), and three-year mortality (HR 2.03, 95% CI 1.29-3.19). Subgroup analysis showed that PBI within 7 days after surgery was associated with one-year (HR 1.86, 95% CI 1.12-3.08), two-year (HR 1.99, 95% CI 1.25-3.17), and three-year mortality (HR 2.13, 95% CI 1.35-3.36), while PBI at 8-30 days after surgery was not associated with short-term mortality (one-year: HR 1.36, 95% CI 0.69-2.69; two-year: HR 1.48, 95% CI 0.80-2.76; three-year: HR 1.51, 95% CI 0.82-2.77).

CONCLUSIONS

Donor-recipient and surgical factors are risk factors for PBI after LTX. Active prevention and treatment of PBI within the first 7 days after surgery may improve short-term survival.

Description, clinical impact and early outcome of S. maltophilia respiratory tract infections after lung transplantation, A retrospective observational study

BACKGROUND AND RESEARCH QUESTION

S. maltophilia infections are associated with significant morbidity and mortality. Little is known regarding its presentation, management, and outcome in lung transplant recipients.

STUDY DESIGN AND METHODS

This retrospective case control study reviewed S. maltophilia respiratory tract infection in lung transplant recipients (01/01/2011-31/01/2020) and described the clinical, microbiological and outcome characteristics matched with lung transplant recipients without respiratory tract infection.

RESULTS AND INTERPRETATION

We identified 63 S. maltophilia infections in lung transplant recipients. Among them none were colonized before transplantation. Infections occurred a median of 177 (IQR: 45- 681) days post transplantation. Fifty-four (85.7 %) patients received trimethoprim-sulfamethoxazole (400/80 mg three times a week) to prevent Pneumocystis jirovecii pneumonia (PJP). S. maltophilia strains were susceptible to trimethoprim-sulfamethoxazole, levofloxacin, minocycline and ceftazidime in respectively 85.7 %, 82.5 %, 96.8 % and 34.9 % of cases. Median duration of treatment was 9 days (IQR 7-11.5). Clinical and microbiological recurrence were observed in respectively 25.3 % and 39.7 % of cases. Combination therapy was not associated with a decrease in the risk of recurrence and did not prevent the emergence of resistance. S. maltophilia respiratory tract infection was associated with a decline in FEV-1 at one year.

CONCLUSION

S. maltophilia is an important cause of lower respiratory tract infection in lung transplant recipients. Trimethoprim-sulfamethoxazole use as prophylaxis for PJP doesn't prevent S. maltophilia infection among lung transplant recipients. Levofloxacin and trimethoprim-sulfamethoxazole appear to be the two molecules of choice for the treatment of these infections and new antibiotic strategies (cefiderocol, aztreonam/avibactam) are currently being evaluated for multi-resistant S. maltophilia infections.

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.

Donor derived cell free DNA% is elevated with pathogens that are risk factors for acute and chronic lung allograft injury

BACKGROUND

Acute and chronic forms of lung allograft injury are associated with specific respiratory pathogens. Donor-derived cell free DNA (ddcfDNA) has been shown to be elevated with acute lung allograft injury and predictive of long-term outcomes. We examined the %ddcfDNA values at times of microbial isolation from bronchoalveolar lavage (BAL).

METHODS

Two hundred and six BAL samples from 51 Lung Transplant Recipients (LTRs) with concurrently available plasma %ddcfDNA were analyzed along with microbiology and histopathology. Microbial species were grouped into bacterial, fungal, and viral and "higher risk" and "lower risk" cohorts based on historical association with downstream allograft dysfunction. Analyses were performed to determine pathogen category association with %ddcfDNA, independent of inter-subject variability.

RESULTS

Presence of microbial isolates in BAL was not associated with elevated %ddcfDNA compared to samples without isolates. However, "higher risk" bacterial and viral microbes showed greater %ddcfDNA values than lower risk species (1.19% vs. 0.65%, p < 0.01), independent of inter-subject variability. Histopathologic abnormalities concurrent with pathogen isolation were associated with higher %ddcfDNA compared to isolation episodes with normal histopathology (medians 1.23% and 0.66%, p = 0.05). Assessments showed no evidence of correlation between histopathology or bronchoscopy indication and presence of higher risk vs. lower risk pathogens.

CONCLUSION

%ddcfDNA is higher among cases of microbial isolation with concurrent abnormal histopathology and with isolation of higher risk pathogens known to increase risk of allograft dysfunction. Future studies should assess if %ddcfDNA can be used to stratify pathogens for risk of CLAD and identify pathogen associated injury prior to histopathology.

Acute respiratory failure among lung transplant adults requiring intensive care: Changing spectrum of causative organisms and impact of procalcitonin test in the diagnostic workup

BACKGROUND

The aim was to identify the causing organisms and assess the association of procalcitonin (PCT) with bacterial pneumonia within 24 hours of intensive care unit admission (ICU-A) among lung transplant (LT) adult recipients.

METHODS

Secondary analysis from a prospective cohort study. All LT adults admitted to ICU for acute respiratory failure (ARF) over 5 years were included. Patients were followed until hospital discharge or death.

RESULTS

Fifty-eight consecutive LT patients were enrolled. The most important cause of ICU-A due to ARF was pneumonia 29 (50%) followed by acute rejection 3 (5.2%) and bronchiolitis obliterans syndrome exacerbation 3 (5.2%). Microorganisms were isolated from 22/29 cases with pneumonia (75.9%): 17 (77.2%) bacterial, 4 (18.2%) viral, 1 (4.5%) Aspergillus fumigates, with Pseudomonas aeruginosa being the most common cause (45.5%) of pneumonia, with 10 patients presenting chronic colonization by P aeruginosa. Median [Interquartile range (IQR)] PCT levels within 24 hours after admission were higher in pneumonia (1.5 µg/L; IQR:0.3-22.0), than in non-pneumonia cases (0.2 µg/L; IQR:0.1-0.7) (P = .019) and PCT levels within 24 hours helped to discriminate bacterial pneumonia (8.2 µg/L; IQR:0.2-43.0) from viral pneumonia and non-pneumonia cases (0.2 µg/L; IQR:0.1-0.7). The overall negative predictive value for bacterial pneumonia was 85.1%, increasing to 91.6% among episodes after 6 months of LT.

CONCLUSIONS

Causes of severe pneumonia in LT are changing, with predominant role of P aeruginosa and respiratory viruses. PCT ≤ 0.5 μg/L within 24 hours helps to exclude bacterial pneumonia diagnosis in LT adults requiring ICU-A. A negative PCT test allows antimicrobial de-escalation and requires an alternative diagnostic to bacterial pneumonia.