Secondary Bacterial and Fungal Pneumonia Complicating SARS-CoV-2 and Influenza Infections in Lung Transplant Recipients

PURPOSE: Select bacterial and mold infections are known risk factors for chronic allograft dysfunction (CLAD) in a subset of lung transplant recipients (LTR). Secondary bacterial (SBI) and fungal infections (SFI) have been described among people with severe influenza infection and COVID-19 requiring mechanical ventilation, but the incidence and clinical outcomes of LTR who develop secondary infections following respiratory viral infections (RVI) are not well described. METHODS: We conducted a retrospective study of LTR who were diagnosed with either influenza or COVID-19 from January 2011-May 2021. Infection definitions and CLAD stage were defined according the International Society of Heart and Lung Transplantation guidelines. RESULTS: Fifty-seven LTR with influenza and 33 with COVID-19 were identified. Eleven (19%) of the LTR with influenza developed SBI and seven (21%) with COVID-19 developed SBI (p=0.83). Among patients who developed SBI, Pseudomonas aeruginosa was the most common isolated pathogen (44%). Five (9%) and 7 (21%) LTR developed SFI within 90 days post Influenza and COVID-19 infection, respectively (p = 0.09). Among patients with fungal infection, Aspergillus species were the most common pathogen (75%). At 180 days post RVI, all-cause mortality was higher in LTR with SBI (17%) compared to those without (3%), p=0.02. Mortality was similarly higher in LTR with SFI (33%), compared to those without (1.3%), p<0.0001. At 180 days post RVI, LTR with SBI had progression of CLAD stage 43% vs 11%, p=0.004. Based on univariable logistic regression, LTR who had augmented corticosteroids at time of RVI, and lower respiratory tract infection (LRTI) had higher risk of SFI (odds ratio (OR) of 6.57 (1.8, 23.9), p=0.002 and 12.5 (2.53, 61.7), p=0.004, respectively). There were trends of increased OR of SBI among LTR with LRTI and LTR requiring ICU admission due to RVI with the ORs of 2.78 (0.98, 8.01), p=0.06 and 3.77 (0.90, 15.84), p=0.07, respectively. CONCLUSION: Secondary bacterial and fungal infections are associated with increased all-cause mortality in LTR with influenza and COVID-19, and in the case of SBI, also associated with CLAD stage progression. LTR with LRTI and augmented steroids may be at increased risk of secondary fungal infections. Strategies to mitigate and improve diagnosis may warrant further examination.