My assumption is that IV treatment would have minimal affect on...

My assumption is that IV treatment would have minimal affect on gut microbiome, while having the best possible impact on blood borne sepsis bugs. If the drug can be given via IV that is a great advantage for the drug as a drug treatment. And also for the gut microbiome, which also brings a major advantage for ongoing health.

Animal and human microbiomes are a fascinating emerging field of study. Each human population has a different pile of bugs in their guts depending on where on earth they live and what they eat. I.e. those who live in the arctic on seafood vs equatorial rainforest vs savannah vs desert dwellers etc. Those with the most diverse microbiomes tend to have better gut health. Western junk food diet full of highly refined foods is the worst possible diet for our microbiome, and its fragile unstable balance is frequently pushed out of kilter by invasive bugs and nutrient imbalances. People who have received a fecal transplant from healthier communities do quite well, especially if they were sick before, but they cannot readily sustain that diversity when still eating the western diet. FYI the gut has a pretty direct link to the brain, and neurotransmitters from the gut affect the brain. The bugs often secrete those same neurotransmitters and these get transmitted to the brain. Effectively the bugs are saying to the brain, "Hey, go eat some XYZ, some of us need more of that stuff down here!" One could even say that it gives us a 'gut feeling' of what we need to be healthy. We should listen to the good bugs more. However an unhealthy microbiome sends us in the wrong direction as far as our appetites go. The bug's imbalanced consensus requests are for the wrong stuff. (One could deduce the political implications in that too!) This is as true with other species as it is with us. Cows given a wide choice of plant species to eat other than just plain grass will select what their guts need. This makes for healthier cows, with lower methane and CO2 emissions, and better healthier meat too. There are lessons here.