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The panelists review the risk factors for MRSA and discuss key treatment considerations for patients with diabetic foot infections, with an emphasis on those who have a history of MRSA.
Dr. Armstrong: If someone has had a previous history of an infection caused by antibiotic resistant bacteria, of any type in any part of the body, is the patient more likely to develop future infections with these organisms?
Dr. Joseph: I know that there are certain associated risk factors with community-acquired MRSA. However, I’m not aware of any data on this. When I’m talking to people about patients who are so-called high risk patients for MRSA, I tell them that if the patient had a previous history of MRSA, then one can pretty much presume that the new infection is also MRSA.
Dr. Lipsky: I am also not aware of a specific study that has addressed this point. Certainly, the risks for developing infections with resistant organisms usually persist with these patients. They tend to have the same diseases that put them at risk for the first infection. Furthermore, now they’ve been exposed to more antimicrobial therapy, which is the main driver of risk. In addition, patients who have been infected once with organisms like Staph aureus often have anterior nares colonization with the organism. The organisms tend to shed from their anterior nares onto their skin and they thus develop Staph infections of any wounds or of intravascular catheter sites.
|  | | “It’s okay to start empiric therapy against resistant
organisms but we should also quickly
discontinue the therapy if we later find that it is unnecessary.”
— Dr. Lipsky
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I think it is highly probable that a patient who once had an infection with MRSA or another resistant organism will be at a higher risk to have it again in the future. One should monitor these patients carefully when they develop infections.
Dr. Armstrong: So all the ingredients are there to produce another problem just as one might find with the history of a recent ulcer. If a patient who had a previous infection with a resistant organism is readmitted to the hospital perhaps within the past year, should we treat the patient as if he or she has another infection with a resistant organism? Should patients be prophylaxed against that, for instance, with a glycopeptide like vancomycin or with quinupristin/dalfopristin or an oxazolidinone?
Dr. Lavery: In my institution, there are a growing number of primary care physicians who initially use vancomycin for patients who are admitted for diabetic foot infection. They start them on vancomycin, for good or ill, because of the high prevalence of MRSA from the community, without regard for previous infections.
Dr. Lipsky: We should be clear about this. Are we talking about a patient who comes in with an infection and we’re directing empiric therapy against resistant organisms including MRSA? Or are we talking about a patient who is hospitalized for another reason, say a diabetic patient with a myocardial infarction, who previously had an MRSA infection? Should we be checking for MRSA colonization and perhaps even truly giving prophylactic antibiotics in that situation to prevent a future infection?
Dr. Armstrong: Let’s focus on the foot-related aspects of those with a prior history of an infection with MRSA.
Dr. Lavery: I absolutely think those people are at the top of the list for empiric anti-MRSA therapy. However, I think the level of critical assessment in determining whether they’ve had a previous infection is lower. I think that the threshold to use vancomycin in our institution is much lower than it used to be.
Dr. Joseph: At the Coatesville Veterans Affairs Medical Center, patients with diabetic foot infections are admitted to the acute care floor. They are almost automatically placed on IV or some sort of anti-MRSA therapy empirically. That’s just because we know there is such a high prevalence of MRSA in the VA population.
However, one could certainly proceed with empiric anti-MRSA therapy for patients who are at risk for MRSA infection and this would include those who have had a previous MRSA infection.
In the Jan. 15, 2003 issue of Clinical Infectious Diseases, Salgado et. al., list their assessment of risk factors for MRSA.4 These risk factors include: recent hospitalization ranging from one to 24 months; recent outpatient visits within 12 months; recent nursing home admissions within 12 months; recent antibiotic exposure within 12 months; chronic illness such as end-stage renal disease, diabetes; malignancy; injection drug use; and close contact with a person with an established MRSA infection.
|  | | Here is a view of a medial space diabetic foot infection secondary to a retained foreign body.
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Dr. Lipsky: That’s almost everybody in our hospital.
Dr. Joseph: When you look at the patients coming in with diabetic foot infections and they have these risk factors for MRSA, I think we’re getting to the point where it’s almost imperative to start these patients empirically with therapies against these resistant gram-positive organisms, pending the culture results.
Determining A Threshold For Empiric Treatment
Dr. Armstrong: Dr. Lipsky, what do you think the threshold should be in terms of the prevalence of resistant organisms in a hospital, at which the clinician should begin empirically treating for that resistant organism?
Dr. Lipsky: Opinions vary on this. My belief is that when somebody who is systemically ill comes in with a potentially serious infection, then the threshold should be quite low — perhaps as low as 5 percent — for covering organisms that need to be treated immediately. On the other hand, consider a mild wound infection. When you can get the culture report back 24 or 48 hours later and find out the patient had an organism that you weren’t adequately treating, I would advocate a higher threshold.
I would rarely fault a clinician for starting empiric therapy that covers MRSA or other resistant organisms. However, there is the question of what do you do when you get the culture reports back and they don’t show those organisms? Too often, physicians continue the antibiotics because the patient appears to be doing well. They either fear that that they missed the resistant organism or didn’t get an appropriate specimen. Unfortunately, sometimes cultures aren’t done in the first place. Then you have a patient who is committed to a course of therapy. This is not a problem if treatment is just a few days or a week, but in the case of osteomyelitis, it might be six weeks or more.
Therefore, I think we have to stress one of the points we brought up in our first Podiatry Today and WOUNDS supplement.3 We need to obtain appropriate specimens for culture and be sure of what the infecting organism is and what its antibiotic susceptibility is. It’s okay to start empiric therapy but we should also quickly discontinue the therapy if it’s unnecessary. |
