FOR THE TEST: Zosyn = Cefepime (except for neutropenic fever). If not available, Penems (Mero, Erta, etc)
FOR LIFE: The reason you put on Cefepime is pseudomonal coverage. You don't need to treat MRSA empirically right off the bat. Especially if it's only a fever. People DO, but they do it because everyone else uses Vanc and Zosyn, not because they know why. Lets just call Pseudomonas "Gram negative" for righ tnow. You remember why Gram negatives and gram positives are different? Lipopolysaccharides. LPS kills people. It causes massive inflammation and shoots the body into septic shock. Remember, in sepsis its SIRS, not the bug, that causes the damage. The Systemic Immune Response part of systemic immune response syndrome, the body's ability to fight infection, is what leads to devestating consequences. So you don't have two days for cultures to come back. MRSA, on the other hand, regardless of how common it is, can linger in your blood for weeks. In fact, it does (endocarditis, osteomyelitis) but it doesn't kill you. You can wait two days for cultures to come back and tell you "MRSA" or one day for "gram positive cocci in clusters." You DONT have to empirically treat. This is the concept of antibiotic stewardship.
What bug does have LPS? Pseudomonas. What bug doesn't have LPS? MRSA. So why treat empirically for a thing that can just hang around and not do that much damage. What benefit is there to train the regular ole enterococcus to be vancomycin resistant when you aren't getting any mortality benefit?
"Neutropenic patients more vulnerable to pseudomonas. Pseudomonas kills fast because it is gram negative. People who are neutropenic need immediate protection against the thing that kills them fast. Thus, cefepime"
"Neutropenic patients more vulnerable to MRSA. MRSA does not kill fast because it is gram positive. People who are neutropenic do not need immediate protection against the thing that wont kill them fast. Thus, no vanc"
Now, if you don't care about stewardship, and are looking at money, cost, and efficiency, you do both. Why? Because you see TWO DAYS of needed IV antibiotics where you do nothing waiting for cultures to come back. Thats a progress note for two extra days. Thats an ICU or ward bed taken up for two extra days. No insurance company is going to pay for that. At least if you start vanc from the get go, you save TWO DAYS. Who cares about antibiotic resistance. THIS PATIENT, RIGHT NOW is getting out of MY SERVICE! It's not ideal, but it certainly is practical in the system in which we practice. Theoretical correctness (what is tested on step 2) says no need for both vanc and cefepime.
Caveat: HAP/HCAP DOES get vanc and zosyn (cefepime),