In the last several months I've done quite a bit of reading and listening to the topic of gut health and immunity. I've been persuaded to believe that the quantity and diversity of the bacterial population in your gut are a large influence in how an immune system responds to an attack.
I've learned that fiber and resistant starch are key food for the bugs in our lower GI track. I guess the mainstream advice that we need more fiber in our diet has been good advice. I've always thought that the fiber was there to add bulk to our stool. Now I'm reading that the fiber feeds our gut bacteria. I've taken to supplementing resistant starch and have observed positive effects, including an absence of colds.
We never know about the successful resistance to immune attacks. We only know about the failures, the bugs that get through.
I haven't answered your main question, however. I do believe that high blood glucose diminishes our immune response. In the past, I've had more sinus infections than before I was diagnosed with diabetes. I know that diabetics suffer with more urinary track infections. Science does tell us that we pass very high blood glucose from the kidneys and to the bladder.
I think controlling blood glucose is essential to our overall health, including resistance to infections. But I think that gut health, quantity and diversity of bacteria, are the main drivers of our immune systems. High BGs also effect the environment of the lower GI.
You may risk your exposure to more and different bugs by working in health care but the determinative influence is your ability to defend against attacks. We've all had the experience of being the only member of the household to not come down with some virulent virus. That's been a mystery to me. I remember someone once said that if we could see all the bacteria and viruses in our environment, we would be afraid to go anywhere.
I think you're smart to take all necessary precautions to protect yourself in your job but you need to realize that the biggest influence is the quality of your gut and therefore your immune system. I've read that the microbes in our gut outnumber our bodies' cells by 10 to 1. I've also read the hypothesis that its been these gut bugs over evolutionary time have educated our immune system to defend us properly.