Aztreonam is an antibiotic. Like penicillin it works by preventing dividing bacterial cells from forming a new cell wall. Unfortunately, like penicillin, it has no effect against bacteria without a well defined cell wall, and many bacteria, incluing staphylococcus, have become resistant to it. However, patients who have an allergy to penicillin are unlikely to be allergic to Aztreonam as well. However, Aztreonam is generally ineffective when given orally so is usually given by intravenous or intramuscular injection. It can also be used in an inhaler.
Joe Dugan is given aztreonam when it is believed he has an e. coli infection from unpasteurized cider.