There are a variety of spaces in the neck that can become infected: peritonsillar, retropharyngeal, submandibular. They can all dissect down the neck and into the chest as well as lead to airway obstruction.
Poor dentition, trauma.
Abscesses: Streptococci (esp milleri) + anaerobes + HACEK ( Haemophilus species, Aggregatibacter species, Cardiobacterium species, Eikenella species, and Kingella species). Gram negative aerobic rods should not occur unless the dentition is really rasty: rotting black nubs of teeth. And they always have a significant other, who, I presume, kisses them.
Lemierres Disease: septic thrombophlebitis of the internal jugular. Patient presents with a sore throat, fevers, and septic emboli on CXR; due to Fusobacterium necrophorum but occasionally other anaerobes or other organisms. I have seen a smattering of S. aurues causing Lemierres.
Steroids, combined with drainage, is perhaps the best therapy (PubMed).
They say never put a mirror in the back of the throat to look at the vocal cords as you can precipitate obstruction. I have seen it twice in my career, with disasterous results.
One of my few areas of magical thinking: if you put a tracheostomy kit in the room, the patient will never need it.