<i>Pseudomonas</i> Infections: Matching Causes and Prevention

Peter L. Salgo, MD: I heard something else that I think we need to at least mention. I think it was you who said that if you have pseudomonas colonization, we then have pseudomonas infection and invasive disease. What’s the difference?

Jason Pogue, PharmD, BCPS-AQID: The clear thing is that a lot of patients are colonized with all kinds of microbiology, but we’re only concerned with patients who actually develop clinical infections from the same place. Colonization will often precede infection occurring, but certainly we’re concerned about the patients once they develop the pneumonia from them having that longstanding colonization of the organism.

Peter L. Salgo, MD: I want to bring it back full circle then, which goes to what I was saying. You can be colonized with pseudomonas, but in order to get an invasive infection with pseudomonas, don’t you need to be sicker? Don’t you need to be one of those patients who’s already, in some way, really ill? Or can you just get pseudomonas out of the blue?

Marin Hristos Kollef, MD: Generally, healthy patients in the community don’t develop pseudomonal infection for the most part. There may be a few exceptions to that rule, but to develop a true pseudomonal infection, it really requires certain host factors. I think that’s what we’ve been commenting on.

Peter L. Salgo, MD: Right.

Marin Hristos Kollef, MD: In addition to the host factors, I think it is important to recognize that it’s a very virulent organism, and I think the audience really needs to be clear on that particular point. Because it’s a virulent organism and it has certain virulent mechanisms in place, antibiotic therapy does become important. We don’t have mechanisms for treating the virulence of the pathogen, so we have to really err on the side of treating it with an appropriate antibiotic regimen.

Peter L. Salgo, MD: Death to bugs; death to pseudomonas.

Marin Hristos Kollef, MD: Death to pseudomonas, but focusing on the antimicrobial aspect of it, since we have limited options for tackling the virulence factors.

Peter L. Salgo, MD: Right.

Andrew Shorr, MD: More importantly, focusing on prevention. There are things that we can do to prevent severe infection in our critically ill patients, whether it’s early ambulation, early liberation from the ventilator, less sedation, or chlorhexidine bathing. One place where we take infection prevention very seriously in the hospital is actually the ICU, where we have bundles of protocols that are evidence based and have been shown in randomized trials to effectively prevent some severe infections. And so, if you’re going to work in an environment where you know it’s enriched for the risk and bad outcomes associated with the bug you’re describing, then it’s incumbent upon all of us to actually start this conversation at, what are we doing for prevention?

Peter L. Salgo, MD: You want to back off. Before we even talk about antibiotics, if we could prevent people from becoming infected—or if they’re colonized, we could prevent it from becoming invasive&mdash;that’s the ideal.

Andrew Shorr, MD: Correct.

Peter L. Salgo, MD: We have techniques for that. Whether it’s a VAP (ventilator-associated pneumonia) bundle or something else—as you said, chlorhexidine&mdash;that would be ideal, right?

Andrew Shorr, MD: The data for chlorhexidine are more controversial than they used to be. We’ve got a positive trial, but we’ve got some follow-up on negative trials.

Peter L. Salgo, MD: I heard a chuckle on the right side of me.

Andrew Shorr, MD: Your patient smells better if they’re bathed in chlorhexidine every day, but I think it speaks to the fact that people are striving to find good, effective, inexpensive strategies, some of which have abundant evidence in support, some of which are controversial when you make a decision about the risk-benefit tradeoff.

Jason Pogue, PharmD, BCPS-AQID: I think with some of the most invasive things that we do, there’s a conscious effort in the ICU to shorten the duration. So, ventilation might be an option for that.

Peter L. Salgo, MD: Absolutely.

Jason Pogue, PharmD, BCPS-AQID: Pulling in the central line sooner on these patients. Those are known risk factors for hospital-acquired infections, chlorhexidine in particular. And so, I think a lot of effort to prevention comes along those lines.

Peter L. Salgo, MD: By the way, I think the correct phrase now is health care facility associated infection. It’s morphed again.

Yoav Golan, MD: Obviously, another component that is very important in our efforts to prevent infection is our use of antibiotics. What antibiotics are we choosing as a matter of protocol? We’re going to discuss this later, but a lot of that is actually in our hands.

Peter L. Salgo, MD: We talk about pseudomonas as if it affects 1 organ system. People always think about pseudomonas pneumonia, which is common, but there are lots of other pseudomonas infections, too, right?

Andrew Shorr, MD: Pseudomonas is a pathogen that, once it sets up shop in your hospital, can cause any kind of infection because it’s a bug-host interaction. It can certainly be a leading pathogen in a ventilator-associated or hospital-acquired pneumonia, but it can still be a leading pathogen in bloodstream infection. My colleagues in the surgical ICU see surgical-site infections in postoperative mediastinitis after CABG (coronary artery bypass graft). If pseudomonas is around, pseudomonas will find a place to get in, and it’s very much the same way with acinetobacter. If it has set up shop, it’s not specific for 1 infection or 1 organ infection. It causes infections in any of those syndromes, even including urinary tract infection. You need to be vigilant.

Peter L. Salgo, MD: Is there one infection that’s worse than others?

Yoav Golan, MD: Before that, just to add to what Andy says, I think it’s important to understand the biology of pseudomonas when you try to predict the kinds of infections. It’s important to remember that pseudomonas is ubiquitous. It’s a moisture type of bacteria. It can exist in the environment. It tends to colonize people, particularly people who get antibiotics and are in health care institutions, particularly on mucosa surfaces. And anything you do to violate the integrity of the mucosa—by putting a line that breaks the mucosa going into the vein, by using a urinary catheter that dilates the mucosa of the urinary tract, by using endotracheal tubes, and so forth&mdash;will provide pseudomonas with an opportunity. So, you tell me what kind of violation of the mucosa you had with your patient and I’ll tell you what the patient is going to be vulnerable to develop.

Peter L. Salgo, MD: But that’s not unique to pseudomonas. You can say that that for staph infections. You can say that for anybody, right?

Yoav Golan, MD: Absolutely. This is not unique to pseudomonas. What is unique to pseudomonas are a few factors. One is, as Andy said, that once you get colonized with it, it’s really hard to get rid of it. It’ a long-term colonization. If you look at the risk of infections, it’s right into colonization and how long you are going to be colonized with the bacteria. What is the ability of this bacteria to survive the antibiotics in the environment, as pseudomonas has a great ability? Pseudomonas is not unique in principle, but it’s more quantitative. That makes it more likely to infect those patients.

Peter L. Salgo, MD: What scares you guys more? Is it pseudomonas pneumonitis? Pseudomonas cystitis? Pseudomonas something else? Is there 1 organ system that, when infected with pseudomonas, is worse than all the others?

Yoav Golan, MD: What scares me the most is once it infects my sickest patients. Because they are the least able to tolerate infection and they’re the ones who require the most aggressive approach.

Peter L. Salgo, MD: Aren’t they the ones who are most likely to get it? That’s what makes this bug so nasty, among other things.

Andrew Shorr, MD: Right, but it is in some way a tautology, right?

Peter L. Salgo, MD: Right.

Andrew Shorr, MD: I think about Yoav’s point about it being a function of the patient, not a function of the bug. If you’ve had a kidney transplant, I’m worried about an ascending tract infection from pseudomonas.

Peter L. Salgo, MD: Sure.

Andrew Shorr, MD: If you’ve been on a ventilator with acute lung injury from flu or on ECMO (extracorporeal membrane oxygenation) for 2 weeks, I’m worried about pneumonia. It is a pathogen that goes where the host offense is weakest. Can I say that pneumonia is associated with the highest accrued mortality rate pseudomonas versus urinary tract infections? Yes, sure, but that’s because it’s easy to eradicate pus in the bladder and it’s hard to eradicate pus in the lung. So, that’s also true for every other pathogen.