The bacteria Staphylococcus aureus and streptococci are most frequently the cause.
[merckmanuals.com]
In the majority of patients the illness was caused by Staphylococcus aureus, and the rest had Hemophilus influenzae infection.
[ncbi.nlm.nih.gov]
Various Staphylococcus species (e.g., S. aureus, S. pneumonia, S. pyogenes ) and less frequently, Haemophilus influenza, can cause windpipe inflammation.
[phaa.com]