How is combination therapy used to treat microbial infections?

One -two punch: Much like in boxing, doctors can fight the germs that cause infection using various techniques. Most of the time, just one antibiotic (one punch) is needed to hit and knock out a germ. For some of the tough ones (like Pseudomonas) we may use 2. Other infections may require different strategies, particularly if it's severe. The rationale is to attack the germs in different ways and 'win' the fight!