|
Sign up to receive email notification of new issues |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||
A New Paradigm for the Management of Skin and Soft Tissue Infections (SSTI) in the Era of MRSAHow will rapid MRSA/SA test results affect treatment algorithms
Recently, Cepheid convened a panel of experts in emergency medicine, surgery, infectious disease, and epidemiology to discuss how treatment algorithms might change in response to having rapid test results available. Doctors David Alland, MD, Samir Awad, MD, Stanley Deresinski, MD, FACP, and David Talan, MD, FACEP, FIDSA expressed their perspectives on being able to know whether a patient’s infection was caused by MSSA or MRSA while the patient is still in the emergency room. Emergency department (ED) physicians thrive on action. Their practice is exemplified by constant multiple demands for their attention and their decisions, and they like it that way. So when patients show up with infected lesions that the patients describe as “spider bites,” if the patients are not systemically ill and the lesions are not considered severe, emergency department physicians instinctively want to take action. “Drain and refrain” (from prescribing antimicrobials) has been at least one publicized approach to such situations.1 And in fact, in most cases (90.5% in one study), the patient without other risk factors does well with drainage alone.2 But wouldn’t it be helpful to know the identity of the offending organism? If infected patients knew that their infection was caused by the infamous methicillin-resistant Staphylococcus aureus (MRSA), for example, they might take precautions to avoid reinfection, or they might modify their personal hygiene practices to prevent spreading the infection to family members, friends, or close contacts. MRSA patients have a dramatically higher risk of reinfection. One study showed that 29% of MRSA-colonized or infected patients became reinfected, often at a different site and sometimes with very serious, even fatal, infections, within 18 months of their initial infection.3 Colonized patients and healthcare workers can also pass the organism to family members or other close contacts.4-5 A recent New England Journal of Medicine poll found that even without culture results, 53% of North American respondents would treat a young athlete with a wound infection with an anti-MRSA antibiotic after incision and drainage.6 A problem with those culture results remains. The results are available two days after the ED visit, and the physician who saw that patient is no longer responsible for the care of that patient. So either that physician must attempt to contact the patient on his day off, or an ED nurse, with many other more pressing tasks, must spend precious time trying to locate and speak with the patient. If the lesion has healed properly, the patient may not appreciate the call.
The patient and his or her family will certainly wonder why they, the nurses, and the doctors could go in and out of the room freely for two days, and suddenly now they need to put on gowns and gloves. Suddenly there are fewer visits for patient care, and the sense of worry and concern grows and grows.7 Understandably, everyone involved is just a bit grumpier and the previously non-colonized roommate possibly even unhappier.
This test offers an exciting new option for diagnosing infections rapidly and accurately. If surgeons knew that a patient’s wound was infected with MSSA and not MRSA, they could be confident that their cephalosporin or extended-spectrum penicillin therapy would be effective. Alternatively, they could avoid using vancomycin, which is not as effective as beta-lactam drugs for MSSA. If they knew that the wound carried MRSA, they could opt for vancomycin or one of several newer antimicrobial agents that are highly effective against MRSA. Recent studies have shown that appropriate treatment improves patient outcomes, which is the major goal of all healthcare institutions.8 The most widely used algorithm for SSTIs today is the one developed by Centers for Disease Control and Prevention (CDC), the American Medical Association, and the Infectious Diseases Society of America (Figure 1a, 1b). Empiric therapy options are listed in the algorithm for presumptive treatment of MRSA. Figure 2 provides an often-used algorithm for pediatric patients presents more details on the lesion size and location.9 Using these references as guidelines, our panel had a free-flowing discussion about how the use of rapid results for MSSA and MRSA might change their practices. 
Dr. David Talan started the discussion with his assertion that there are three types of patients. First, there are those who are critically ill, further characterized by Dr. Stanley Deresinski as patients with immediate life- or limb-threatening conditions, for whom physicians must start antimicrobial therapy immediately. There is no time to wait for the results of a rapid microbiology diagnostic test, no matter how quickly the results are available. Empiric treatment must be immediate to decrease mortality in this very ill group of patients. The second group of patients is one for which an algorithm that includes a rapid diagnostic arm makes sense. These patients present with an SSTI but they are not systemically ill and the infection is not necrotizing or a bite wound. Dr. Deresinski agrees that this is the type of patient for whom a rapid MRSA result would impact therapy. A rapid result showing the presence of MSSA and not MRSA, for example, would indicate that treatment with vancomycin or a newer, more expensive anti-MRSA agent, such as linezolid, daptomycin, or tigecycline is unnecessary. Knowing up front that nafcillin or cephalexin will be effective both simplifies and lowers the cost of treatment. 
Dr. Talan and Dr. Samir Awad noted that a third type of patient presents with an SSTI that is chronic (not necrotizing fasciitis) and likely to be polymicrobial. Such patients require debridement of the wound and long-term antimicrobial therapy. For these patients, a rapid result showing the presence of MSSA or MRSA will help the physician to target the anti-staphylococcal therapy. In Dr. Awad’s institution, having this information within one hour would prevent the overutilization of anti-MRSA therapy in approximately 30% of the patients. Dr. David Alland concurred with this assessment. He pointed out that anti-MSSA therapy is not only less expensive, but is given for shorter duration. According to Dr. Alland, the negative predictive value of a rapid test has to be extremely good to reap these benefits. The panel also discussed how the use of a rapid test would alter the management of hospitalized patients. One obvious arena for immediate utilization of the results is for the patient undergoing surgery. Vancomycin as a preemptive prophylactic agent could be avoided, with two positive consequences:
Another positive outcome would be institution of appropriate infection control measures before the patient was placed in a room. Until all hospitals in the United States have migrated to all-private rooms, the problem of patient placement and proper isolation will remain a key infection control issue.10
The findings of the Institute for Healthcare Improvement, new guidelines from CDC and professional societies, and the plethora of states enacting legislation mandating MRSA surveillance and subsequent action have magnified the need for cost-effective strategies in healthcare settings. Cost-effectiveness studies such as those of Forrest and colleagues can be cited to mitigate the perceived price barriers to enacting the new molecular technology-based tests.12 New antimicrobial agents that are due to be released in the coming year, such as ceftibiprole, dalbavancin, televancin, and oritavancin, are highly effective but are likely to be expensive, emphasizing the need for such cost-benefit studies. Finally, the experts noted that they could simplify a protocol for outpatient treatment of SSTI if they knew up front that MRSA was the etiological agent. The following points were discussed:
In summary, our panel of experts expressed great enthusiasm for the ability to quickly identify those patients with skin and soft tissue infections who harbored either S. aureus or MRSA. These distinguished clinicians anticipate a new era in which more rapid information will lead to better initial treatment choices.
References
|
 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||
What if the infection is severe enough that the patient is admitted to the hospital? Of course cultures will be obtained. If the cultures show the patient is infected with MRSA, then the patient is placed on contact precautions or moved to a private room—but this information isn’t available for at least two days.
For nearly three decades, the Star Trek Tricorder used by Dr. McCoy to get an instantaneous diagnosis of a patient’s malady with a single, non-invasive pass over the patient’s body was the best of medical science fiction. With FDA clearance of Cepheid’s moderate-complexity Xpert™ MRSA/SA Skin and Soft Tissue Infection (SSTI) on-demand molecular test, we are one step closer to real-time diagnosis—although we still have to use a swab! A new diagnostic paradigm is emerging, and ED doctors will have to rethink their practices. Starting now, the presence of either Staphylococcus aureus (i.e., MSSA) or MRSA in a swab from a wound lesion can be determined within one hour of sample collection—right in the ED, if desired.
A less-recognized benefit of knowing that MRSA is the cause of an SSTI is that an antimicrobial agent known to have anti-toxin activity, such as linezolid or clindamycin could be used to potentially reduce the severity of the infection.11 Even before the organism is destroyed, its toxin-producing abilities are inhibited by these ribosomal-active agents. MRSA toxins, including Panton-Valentine leukocidin, alpha toxin, and toxic shock toxin, contribute to virulence of the organisms that carry them.
