• Katarzyna Talaga-Ćwiertnia, Agnieszka Sroka-Oleksiak, Barbara Zapała, Dominika Salamon, Agnieszka Krawczyk, Monika Brzychczy-Włoch, and Tomasz Gosiewski.
• Department of Molecular Medical Microbiology, Division of Microbiology, Faculty of Medicine, Jagiellonian University Medical College, Kraków, Poland
• Pol. Arch. Med. Wewn. 2023 Aug 30; 133 (7-8).

IntroductionThe effects of SARS‑CoV‑2 infection on the composition of the upper respiratory tract (URT) microbiota are yet to be established, and more attention to this topic is needed.ObjectivesThe study aimed to assess the bacterial profile and the possible association between the URT microbiota composition and the SARS‑CoV‑2 viral load.Patients And MethodsNasopharyngeal swabs were taken from 60 adult patients with SARS‑CoV‑2 infection who were divided into 3 groups based on the quantification cycle (Cq) value in the quantitative polymerase chain reaction test: group I (n = 20), Cq lower than or equal to 31 (high replication rate); group II (n = 20), Cq greater than 31 and lower than 38 (low replication rate), and group III (n = 20), Cq higher than or equal to 38 (virus eliminated from the nasopharyngeal epithelial cells). The obtained genetic libraries of 16S rRNA were sequenced and taxonomic diversity profiling was performed to determine the α- and β‑biodiversity in each group.ResultsA significantly lower abundance of Prevotella species was noted in group I, as compared with groups II and III. Akkermansia muciniphila, Faecalibacterium prausnitzii, Fusicatenibacterium saccharivorans, and Bacteroides dorei abundance was characteristic of and significantly greater in group I than in groups II and III. Overall, the microbiota composition was the most diverse in group I, whereas groups II and III were more homogenous in terms of taxonomic diversity.ConclusionsThe arbitrary division of patients according to the SARS‑CoV‑2 viral load was reflected in diverse composition of their bacterial microbiota, which implies an association between these 2 factors. The patients with a low viral replication rate and those who eliminated the virus from the epithelial cells belonged to a group with a less diverse microbiota community than the patients with a high viral replication rate.

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