Shifts in the swine nasal microbiota following challenge in a longitudinal study.

is a widespread, highly infectious bacterial pathogen that causes respiratory disease in swine and increases the severity of respiratory infections caused by other viral or bacterial pathogens. However, the impact of infection on the swine respiratory microbiota has not been thoroughly investigated. Here, we aim to assess the influence of infection on the community structure and abundance of members of the swine nasal microbiota. To do so, the nasal microbiota of a non-infected control group and a group infected with (BB group) were characterized prior to strain KM22 challenge (day 0) and on selected days in the weeks following challenge (days 1, 3, 7, 10, 14, 21, 36, and 42). was cultured from nasal samples of the BB group to assess nasal colonization. The results showed that colonization did not persistently affect the nasal bacterial diversity of either of the treatment groups (alpha diversity). However, the bacterial community structures (beta diversity) of the two treatment groups significantly diverged on day 7 when peak colonization levels of were detected. This divergence continued through the last sampling time point. In addition, (unclassified), , and (unclassified) showed increased abundances in the BB group relative to the control group at various time points. This study revealed that colonization can disturb the upper respiratory tract microbiota, and further research is warranted to assess how these disturbances can impact susceptibility to secondary infections by other respiratory pathogens.