Respiratory Infections | June 19, 2024 | FREE
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Fungal, bacterial pathogens in lungs differ in severe influenza versus COVID-19

Potential bacterial pathogens and aspergillosis were detected in 20% and 38% of patients with influenza and 37% and 31% of those with COVID-19, respectively, in a recent Belgian study.

Infectious agents differ in patients with severe influenza versus COVID-19, a recent study found.

The retrospective study, conducted in Belgium, included mechanically ventilated influenza and COVID-19 patients with or without invasive aspergillosis who had bronchoalveolar lavage (BAL) for bacterial and fungal culture within two weeks after ICU admission. Patients admitted for influenza between Oct. 1, 2009, and March 8, 2020, and COVID-19 patients admitted between March 1, 2020, and November 14, 2022, were included. The goal of the study was to compare the lung bacterial microbiome and its association with viral and fungal infection, immunity, and outcomes in patients with severe influenza or COVID-19, with or without aspergillosis. A subset of these patients, as well as a subset of patients who required noninvasive ventilation, also underwent 16S rRNA gene sequencing and testing of the viral and bacterial load of BAL samples. The results were published June 11 by the American Journal of Respiratory and Critical Care Medicine.

The study included 142 patients with influenza and 281 patients with COVID-19 who required mechanical ventilation and had had a bacterial culture performed. Most COVID-19 patients (91.8%) and 70% of influenza patients received high-dose corticosteroids during the first two weeks of their ICU stay. Antibiotics were more commonly administered to influenza patients than COVID-19 patients in the five days before ICU admission, but almost all patients received antibiotics in the first two weeks of the ICU stay, with a median duration of 11 days for both cohorts.

Twenty percent of patients with influenza and 37% of those with COVID-19 had potential bacterial pathogens, and 38% and 31% had aspergillosis, respectively. Influenza and COVID-19 patients had similar cumulative incidences of bacterial pathogen detection in the first three days after ICU admission, but rates then plateaued in the former group while continuing to increase in the latter. Bacterial pathogens in BAL were significantly associated with 90-day mortality only in influenza patients, especially those with influenza-associated pulmonary aspergillosis. Increased pro-inflammatory pulmonary cytokine responses to bacterial pathogens were seen in patients with COVID-19 but not those with influenza.

The authors noted that the study samples for 16S rRNA gene sequencing were collected retrospectively from their hospital biobank and that bacteria genus and species could not be determined in all patients, among other limitations. "In conclusion, our results show the relevance of studying tripartite viral-fungal-bacterial pathogen interactions in addition to the classical viral-fungal and viral-bacterial co-infections. Besides bacterial superinfection, aspergillosis must be sought for in all critically ill influenza patients," they wrote. "Prospective studies investigating the lung microbiome, providing integration with metabolomics, and animal work, will be required to improve our insight in the complex interplay between the host, virus, fungus and bacteria."