Outsmarting Resistant Infections - Episode 9

Understanding Gram-Positive Nosocomial Infections

Peter L. Salgo, MD: You know what we’re going to do, we’re going to shift gears slightly. We’re going to go from the gram-negatives over to the gram-positives because we already do the gram-negatives. That’s why we’re going to do the gram-positives. And although it is tempting to say we want to talk about community-acquired gram-positive infections in hospitalized patients, as you pointed out, it’s a gray area. The community-acquired infections and the hospital-acquired infections, they’re all sort of mushing together. So, why don’t we start with, are there differences between community-acquired bacterial infections versus hospital health care—acquired infections, in the emergency department, for example, specifically with regard to gram-positives?

Jason Pogue, PharmD, BCPS-AQID: Yes. I think that this is another situation where it becomes syndromic in nature and with what disease state you’re presenting with. Again, we talk a lot about community-acquired MRSA with regards to skin infections, for example. But it’s a certain type of skin infection. It’s purulent, it’s an abscess. So, knowing those types of presenting factors. Like I mentioned earlier, people talk about community-acquired MRSA as it relates to things like community-acquired pneumonia. And while it’s absolutely true that it’s a very infrequent pathogen in community-acquired pneumonia, when it does occur, it’s a nasty bug. And so, when patients present with severe necrotizing pneumonia, it has to be in your differential. So, what I would say, I guess, is more knowing. It’s crucial that we know the patients who are at risk for it and how they present, and that’s when we know we have to cover for it.

Peter L. Salgo, MD: But wait. If you say you have to know the patients who are at risk for it who come into the emergency room, how can you know that if, in fact, the MDR pathogens are out there in the community? Is it safe? I think it used to be safe to say, “Oh, this patient is coming in from home with a skin infection; it’s not going to be an MDR bug.” Is that a safe assumption anymore? I’m sensing it’s not.

Jason Pogue, PharmD, BCPS-AQID: I wouldn’t say it’s a safe assumption. Without getting into that health care—associated piece of the story, because, again, are they actually coming from home or are they coming from some other…

Peter L. Salgo, MD: You can parse that out.

Jason Pogue, PharmD, BCPS-AQID: Let’s take that piece out of the story and just say they’re coming from home. Is it safe to say it’s not this? And I think the answer is no in certain disease states. Like I said, there are particular ways when you see MRSA present in a community-acquired infection, there are flags that kind of allude that to you. But even when you talk about pneumococcus—again, drug-resistant pneumococcus is an issue—you’ll see the same things that play true. Are you in a community that has high rates of it? Has your patient gotten macrolides in the past? It’s the same kind of concept. It’s just being applied now out to the community.

Peter L. Salgo, MD: But are you implying—and I seem to have heard this, and I want to be very clear—that MRSA, in terms of its clinical presentation, without regard to its antibiotic resistance, it’s a Staph aureus? Does it present differently than ordinary Staph aureus?

Jason Pogue, PharmD, BCPS-AQID: You can see an association because, again, there’s a blurry line between MRSA and MSSA.

Peter L. Salgo, MD: Is he going to say it depends?

Jason Pogue, PharmD, BCPS-AQID: It depends, yes. But the simple answer is, yes, it can present differently because the strains of community-acquired MRSA have been associated with a bunch of different virulence factors. But now that has kind of been portrayed in some of our MSSA as well, which really muddies that water. But it’s notorious in a skin infection, again, to see purulence, to see an abscess. Those are the types of things you see with MRSA, and again, you don’t really see it with MSSA to the same degree, although you can. But you know that MRSA has a higher likelihood of being a player in that scenario.

Peter L. Salgo, MD: Because that, to me, is a real change. Because I was always taught that Staph aureus is Staph aureus and the resistance of the Staph aureus simply means you’ve got to treat it differently. But it’s a bad bug, when you get it in your blood. Like dogs and cats sleeping together, mass hysteria, Staph aureus. And you’re telling me that MRSA is a bad Staph aureus compared to another Staph aureus?

Jason Pogue, PharmD, BCPS-AQID: And I’m not saying that MSSA is a good Staph aureus.

Peter L. Salgo, MD: I didn’t say that.

Jason Pogue, PharmD, BCPS-AQID: I want to be clear about that.

Peter L. Salgo, MD: It’s just more bad.

Jason Pogue, PharmD, BCPS-AQID: I would say that, again, we’re talking specifically in patients presenting from the community with certain disease states. And what you’ll find in the hospital is a lot of those virulence factors that I talked about now exist in MSSA as well. So, you see the same types of things. I think the biggest difference, at least in my opinion, is we have better drugs to treat MSSA than we do with MRSA.

Debra Goff, PharmD, FCCP: Right. I was going to say part of the badness is because we have basically 1 drug to treat them with parenterally that we’re still arguing how to dose it 3 decades later.

Peter L. Salgo, MD: This would be vancomycin?

Debra Goff, PharmD, FCCP: Yes, that would be correct. And so, that created some of the challenges. You have a drug that probably if it came to clinical trials today, I’m not sure where it would be. And it probably wouldn’t be in the position that it is in most hospitals now. So, that creates some of the badness with Staph aureus.

Peter L. Salgo, MD: Let me nail this if I can. We’re talking about a really bad actor here. We’re talking about MRSA out in the community. Do we have a number? What is the prevalence of MRSA out there in the real world? Does anybody know really?

Andrew Shorr, MD: In terms of infections brought into the hospital, what proportion are MRSA?

Peter L. Salgo, MD: Yes. What is the prevalence of a MRSA from the community to come into your ER?

Andrew Shorr, MD: So, the guys at UCLA have probably done the best study on this. They have a multi-ER surveillance system across the country, and they say that about 30% to 40% of the Staphand these data are old, so it’s probably higher now—coming into emergency departments in community-onset kinds of infections are MRSA. And that’s a miss of USA400 and USA300, these kinds of toxin and nontoxin-producing strains. And so, again, it’s a mess because it’s a very promiscuous bug and these plasmids move back and forth, left and right.

Peter L. Salgo, MD: My daughter, who is 13 years old, if she heard those numbers would probably text, “OMG, 40%.” We are really blurring the line. The whole sense of, “Oh, it’s a community-acquired bug, a little vancomycin, go home, have a nice life.” Not so much anymore, yes? This sounds icky. How’s that?

Sandy J. Estrada Lopez, PharmD, BCPS (AQID): Absolutely.