Treatment of Skin Infections in the Age of MRSA
Treatment of Skin Infections in the Age of MRSA
Author: Kristen Kent, MD, Emergency Physician, St. Anne's Hospital, Fall River, MA.
Peer Reviewer: Michael C. Plewa, MD, FACEP, Research Director, St. Vincent Mercy Medical Center Emergency Medicine Residency, Toledo, OH.
Introduction
Methicillin-resistant Staphylococcus aureus (MRSA) outside of the hospital setting has complicated the management of skin and soft-tissue infections (SSTIs). Healthcare-associated MRSA (HA-MRSA) has been studied for some time, but with the emergence of community-associated MRSA (CA-MRSA) there are new concerns regarding pathogenesis, treatment, and prevention.
This article summarizes review articles, experts' opinion, retrospective reviews, and prospective observations to discuss the treatment of skin infections in the age of CA- MRSA.
What Type of "MRSA" Causes SSTI?
Source: Millar BC, Loughrey A, Elborn JS, et al. Proposed definitions of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). J Hosp Infect 2007;67:109-113.
This review article distinguishes the major differences between HA-MRSA and CA-MRSA and proposes definitions for subgroups of CA-MRSA. "MRSA" describes the specific antibiotic resistance of S. aureus to methicillin. In community populations, MRSA was first noticed among intravenous drug users in the 1980s, and in healthy community individuals in the 1990s. With the emergence of CA-MRSA, the CDC drafted criteria to distinguish CA-MRSA from HA-MRSA using epidemiological information. The criteria include risk factors such as no medical history of MRSA; no health facility contact in the past year; and no dialysis, surgery, or placement of medical devices in the past year. However, these criteria do not take into account the microbiological and genetic aspects of CA-MRSA.
Recently, there has been confusion in the medical literature from synonymously used terms all referring to non-HA-MRSA (i.e., community-acquired, community-associated, community-derived) and its sub-definitions (i.e., Panton-Valentine leukocidin gene) [PVL]-negative, CA-MRSA-like). Today, "community-associated-MRSA" is the preferred term when referring to non-HA-MRSA.
The authors propose 3 terms to sub-define CA-MRSA based on clinical, epidemiological, and microbiological characteristics: PVL+ CA-MRSA, PVL- CA-MRSA, and nosocomial CA-MRSA. In PVL+ CA-MRSA and PVL- CA-MRSA: MRSA must be confirmed; the patient originates from the community; the isolate is sensitive to most classes of antibiotics except beta-lactam agents; the infection usually presents as a SSTI (although other clinical manifestations may be present); and the isolate contains the staphylococcus cassette chromosome mec (SCCmec) type IV or V gene. PVL+ CA-MRSA also contains the Panton-Valentine leukocidin gene, while PVL- CA-MRSA does not. Nosocomial CA-MRSA must be confirmed as MRSA; it is susceptible to most antibiotics except beta-lactams and contains SCCmec type IV or V. However, it does not have to originate in the community and does not always present as the typical SSTI.
Commentary
CA-MRSA, the type of MRSA that typically causes SSTIs, is clinically, epidemiologically, and genetically different from HA-MRSA. It is resistant to methicillin antibiotics but is generally more susceptible to a greater number of antibiotics than HA-MRSA. Patients who manifest infections are usually healthy patients without the risk factors typically associated with HA-MRSA. CA-MRSA is now being found in health care settings along with HA-MRSA.
MRSA can be further characterized genetically, specifically by SCCmec type IV or V and the presence or absence of the PVL toxin. SCCmec is the gene that encodes for methicillin resistance; CA-MRSA typically carries SCCmec IV or V. The PVL toxin gene has been regarded as a virulence factor of MRSA and also can be found in methicillin-sensitive S. aureus. As we review the treatment of SSTIs in the age of MRSA, it may become apparent how the characterization would be helpful and the subclassifications and definition may evolve.
Note from the author: Although community-associated is advocated as the preferred term, when summarizing the following articles, the term used by the authors of the respective papers will be used in the summary.
How Prevalent Is MRSA in Patients with Purulent SSTIs?
Source:Moran GJ, Krishnadasan A, Gorwitz RJ, et al. Methicillin-resistant S. aureus infections among patients in the emergency department. N Engl J Med 2006;355:666-674.
This prospective study investigated the prevalence of MRSA as a cause of SSTIs among adult emergency department patients from 11 metropolitan areas, characterized the bacteriologic characteristics of S. aureus isolated from SSTIs, and also evaluated factors potentially associated with MRSA SSTIs. Patients age 18 and older who presented to a university-affiliated emergency department with purulent SSTIs of less than one week duration were included in the study. Perirectal abscesses and non-purulent cellulitis were not included. Specimens from the patient's infected areas were obtained and the antimicrobial susceptibility of S. aureus to routinely tested antibiotics was determined. Also, available S. aureus isolates were sent to the CDC for further characterization, including testing for the presence of certain enterotoxin genes and the SCCmec type.
MRSA was the most common isolate at 10 of 11 of the emergency departments. It was isolated from 59% of all patients included in the study, but its incidence ranged from 15% to 74% in each of the institutions included. Of MRSA cultures, 100% were susceptible to trimethoprim-sulfamethoxazole (TMP-SMX) and rifampin. Of the 218 MRSA isolates sent to the CDC, 216 were characteristic of CA-MRSA, 214 contained SCCmec IV, 213 contained PVL toxin genes, and 212 were typed as clone US300. Features associated with the isolation of MRSA as compared with the isolation of other bacteria included: antibiotic use in the month prior to enrollment, a lesion attributed to a "spider bite," history of MRSA infection, and recent contact with someone with a similar skin infection. Of the 406 patients who had treatment information available, 19% received incision and drainage alone, 10% received antibiotics alone, 66% received both, and 5% neither. Of patients who received an antibiotic, 100 of 175 received one that was not concordant with the results of the susceptibility testing. However, although follow-up was limited, 238 out of 248 reported resolved or improved infection at the time of phone follow-up.
Commentary
This article addresses the high prevalence of MRSA. Overall, MRSA was isolated from most of the SSTIs in the study. Almost all of the MRSA isolates obtained from the purulent SSTIs were characterized as CA-MRSA, contained PVL toxin and SCCmec IV genes, and were typed as US300. US300 is the most common CA-MRSA clone in the United States. Although most patients were prescribed antibiotics, the majority of the prescribed antibiotics did not cover the pathogen isolated. These data do not show an increased failure rate in the treatment of those receiving discordant antibiotics; however, follow-up was limited.
Non-purulent SSTIs were not included in the study. Within the study, there was a varying degree of prevalence of CA-MRSA in different areas of the country; this may be true for settings such as rural or community emergency departments that differ from metropolitan academic settings. Although the study addresses prevalence, the results regarding follow-up for resolution of infection were limited by an insufficient number of patients to draw a definitive conclusion. Follow-up also was conducted by telephone interview, biased by patient subjectivity, and patients were not directly assessed by a clinician.
What Do Experts Recommend for Management of CA-MRSA?
Source: Gorwitz RJ, Jernigan DB, Powers JH, et al, and Participants in the CDC-Convened Experts' Meeting on Management of MRSA in the Community. Strategies for clinical management of MRSA in the community: Summary of an experts' meeting convened by the Centers for Disease Control and Prevention. 2006. Available at http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca.html.
This report summarizes strategies for management of MRSA in the community and is based on the MRSA experts' meeting at the Centers for Disease Control and Prevention (CDC) in 2004, as well as other data available as of January 2006.
CA-MRSA causes a similar spectrum of disease to MSSA (methicillin-susceptible S. aureus), with furuncles, carbuncles, and abscesses being the most frequent; however, more severe infections may be encountered as well. Clinicians should routinely ask about other close contacts or household members with similar infections.
Incision and drainage should be routine treatment. For small lesions that are not amenable to incision and drainage, moist heat may be satisfactory to aid drainage. Culture and sensitivity testing should be performed from infection sites to help with management of individual patients, as well as to help determine local susceptibility and resistance patterns. Factors that may influence the initiation of empirical antibiotic treatment may include: severity and rapidity of lesion progression, evidence of systemic illness, associated co-morbidities or immune suppression of the patient, extremes of age, a lesion that is anatomically difficult to drain, and lack of response to treatment after incision and drainage alone. The incidence of CA-MRSA varies geographically in the United States; therefore, when empiric antibiotic treatment is initiated, it is more important to be knowledgeable of local resistance patterns for the pathogens than to categorize MRSA as community- or hospital-associated. There are no data to determine a specific MRSA prevalence rate that would warrant antibiotics aimed at MRSA, but >10-15% has been recommended by some experts. Molecular typing and identification of toxin genes does not effect clinical management decisions.
More data are needed from controlled clinical trials to determine optimal antibiotic treatment for CA-MRSA, but TMP-SMX, clindamycin, tetracyclines, and rifampin have been suggested. TMP-SMX is not FDA-approved for the treatment of staphylococcal infections, although the literature contains several reports of successful treatment with it. Also, TMP-SMX is not effective for group A streptococcus SSTI and is not recommended in women in the third trimester of pregnancy nor in infants younger than age 2. Clindamycin is linked with Clostridium difficile-associated disease and there are reports of unsuccessful treatment. Long-acting tetracyclines (doxycycline, minocycline) may be more effective than tetracycline, although tetracyclines are not recommended during pregnancy or for children younger than age 8. Rifampin should not be used as a single agent because resistant strains of S. aureus occur rapidly and drug-drug interactions are common with this medication. Linezolid covers both MRSA and group A streptococcus but can cause dose- and duration-dependent reversible myelosuppression and is expensive. There also are rare reports of resistance developing in S. aureus. Linezolid should be reserved for severe infections and prescribed in conjunction with infectious disease consultation. Fluoroquinolones and macrolides are not optimal choices for empiric use to treat CA-MRSA because of high resistance. Intravenous antibiotics may be appropriate for patients with severe staphylococcus infections.
It is not necessary to routinely collect nasal cultures on patients with possible CA-MRSA infection, and there are no data to support the use of decolonization regimens for contacts or patients with CA-MRSA infection. However, after standard precautions are used, decolonization may be reasonable to employ when there are recurrences of infection or ongoing transmission in closely associated cohorts. Standard infection control precautions should be used in both in- and out-patient healthcare settings. Contact precautions also should be taken for patients with wound drainage that cannot be contained and for patients who are suspected to be colonized or infected with MRSA in acute care inpatient settings. Patient education is critical to management, and patients who cannot maintain adequate hygiene should be excluded from activities that involve close contact with others. Patients should be instructed to return if they have systemic or worsening local symptoms or if their symptoms do not improve within 48 hours.
Commentary
These guidelines for the management of CA-MRSA are helpful, especially since there are discrepancies in the medical literature. Incision and drainage should be routine and empiric antibiotics are discretionary. TMP-SMX is probably the most commonly prescribed antibiotic for CA-MRSA SSTI even though it is not FDA approved for such.
MRSA colonization not only occurs in the nares, but also the pharynx, axilla, rectum, and perineum; this may be important in transmission of infection but more data are needed. There has been debate regarding whom to test for nasal colonization and whether decolonization will help prevent transmission; the report finds no evidence for this testing as a routine measure.
Limitations of this report include that it is 2 years old and is based on a meeting the occurred approximately 4 years ago; a great deal of research on MRSA has occurred since this time. The next report is due out in the summer of 2008.
Do Antibiotics Change Treatment Outcomes of CA-MRSA SSTIs?
Source:Ruhe JJ, Smith N, Bradsher RW, et al. Community-onset methicillin-resistant Staphylococcus aureus skin and soft-tissue infections: impact of antimicrobial therapy on outcome. Clin Infect Dis 2007;44:777-784.
This retrospective study investigated the effect of active antimicrobial therapy on the outcome of patients with uncomplicated community-onset MRSA SSTIs. Clinical microbiology laboratory records at 2 tertiary care medical centers identified patients 18 years and older with community-onset MRSA SSTIs. The medical records of these patients were obtained, and patients with cutaneous abscess, furuncles, carbuncles, and cellulitis were included. Patients with folliculitis or impetigo were excluded, as well as patients with complicated SSTIs. The primary outcome was treatment failure.
The study included 492 patients with a total of 531 episodes of community-onset MRSA SSTIs, defined as a MRSA specimen obtained during an outpatient visit or within 48 hours of admission to the hospital. Of the community-onset MRSA, 351 subjects had CA-MRSA (defined as community-onset MRSA and no risk factors for healthcare-associated infection including surgery, dialysis, long-term care facility residence, indwelling medical device, and previous isolation of MRSA). Of the patients, 8.5% (45 subjects) failed treatment, which was defined as the need for additional incision and drainage, subsequent hospitalization, occurrence of a new cultured MRSA SSTI while receiving antibiotics, and/or antibiotic failure 2 days after incision and drainage or positive wound culture. Of those who received active antimicrobial therapy, 95% (296 patients) had success in treatment, versus 87% (190 patients) of those who did not receive active antimicrobial therapy. The only independent predictor of treatment failure was failure to initiate active antimicrobial therapy within 48 hours of incision and drainage or positive culture, if no incision and drainage was performed. Of the patients who received incision and drainage (427 episodes), failure to initiate active antimicrobial therapy within 48 hours also was the only independent predictor of treatment failure.
The results are only moderately statistically significant; the success rate was 95% in those who received active antibiotics and 87% in those who did not. It may be reasonable to closely monitor patients with MRSA SSTI after incision and drainage to limit antimicrobial therapy until more studies identify patients who would most benefit from active antimicrobial therapy.
Commentary
This study investigated the effectiveness of active antibiotic therapy for patients with simple SSTIs. It precisely defines specific outcomes and treatment failure, and includes a greater number of subjects than most studies published. The results show that most SSTIs treated with incision and drainage do not have treatment failure without antibiotic therapy. However, unlike other studies, it found a significant improvement in those who received active, or concordant, antibiotic therapy compared with those who did not.
The retrospective design offers the possibility of selection, information, and outcome biases, and the subjects were not randomized to treatment. This allowed for unmeasured differences in the patients or treatments. The study also included a short follow-up period, missing potential reinfections or worsening infections after the follow-up period. The bottom line is that the verdict is still out on the benefit of antibiotics after incision and drainage of simple SSTIs.
What Are the Outcomes of Hospitalized CA-MRSA Patients?
Source:Miller LG, Quan C, Shay A, et al. A prospective investigation of outcomes after hospital discharge for endemic, community-acquired methicillin-resistant and -susceptible Staphylococcus aureus skin infection. Clin Infect Dis 2007;44:483-492.
This prospective study compares the long-term outcomes of patients with CA-MRSA skin infections with patients with CA-MSSA skin infections. It included 280 hospitalized patients from February 2004 to October 2004 who grew S. aureus from a culture obtained within 72 hours after admission to the hospital. Treatment was at the discretion of the patient's health care provider. The primary outcome was clinical nonresponse 30 days after enrollment in the study. Nonresponse was defined as infection relapse at the original site or S. aureus infection at a separate body site, and the need for antibiotics after the initial planned antibiotic treatment.
Of the 280 patients in the study, 202 had community-acquired S. aureus and 78 had healthcare-acquired S. aureus. Of the community-acquired S. aureus infected patients, 60% had community-acquired MRSA and 40% had community-acquired MSSA. Community-acquired MRSA had a high degree of resistance to macrolides and fluoroquinolones; was universally susceptible to TMP-SMX, rifampin, and vancomycin; and had a high degree of susceptibility to clindamycin and tetracycline. Community-acquired MSSA cultures were highly susceptible to all antibiotics tested except penicillin. Patients who did not respond to treatment were less likely to have had incision and drainage. No other host or treatment factors were found to be associated with nonresponse. Of note, discordant antibiotic therapy was not associated with a higher nonresponse rate. Patients with community-acquired MRSA were more likely than those with community-acquired MSSA to have had a higher rate of self-reported cure, although clinical non-response, the primary outcome variable, was not different between groups. Patients with community-acquired MRSA also were less likely than patients with community-acquired MSSA to be rehospitalized during the 30 days after initial hospitalization. There was a nonsignificant trend for patients with community-acquired MRSA to be more likely than community-acquired MSSA patients to report a household contact with a new skin infection at day 30. There was no difference in these outcomes at 120 days.
Commentary
This study shows similar rates of nonresponse to treatment for CA-MSSA and CA-MRSA in hospitalized patients with skin infections. At 30 days, the only difference found between nonresponders and responders was that the nonresponders were less likely to have undergone incision and drainage.
The prospective design allowed for systematic collection of data during the patients' hospitalization and highly detailed epidemiological and clinical data, which may not be found with a review of medical charts. However, this study was an observational study and did not randomize treatment, allowing for unmeasured factors to effect results. In fact, the authors state the patients with CA-MSSA tended to have more co-morbidities, suggesting that the patients with CA-MSSA were less healthy than the patients with CA-MRSA at baseline. Also, only two-thirds of the patients completed the day-30 follow-up interview and follow-up was based on telephone interviews, which are limited by recall and patient subjectivity.
Are Antibiotics Necessary After Incision and Drainage of Simple Abscesses Caused by MRSA?
Source: Hankin A, Everett WW. Are antibiotics necessary after incision and drainage of a cutaneous abscess? Ann Emerg Med 2007;50:49-51.
The authors searched medline and EMBASE to review original published research articles focusing on prescribing antibiotics after incision and drainage of an abscess. Only five original published research articles were found on this topic, in addition to one abstract.
The first article reviewed is an unblinded clinical trial from the 1970s that randomized 219 abscesses to one of 4 treatment groups: 1) incision and curettage and primary closure after IV clindamycin followed by 4 days of oral clindamycin; 2) incision and curettage and primary closure without antibiotics; 3) incision and drainage with loose packing and antibiotics; and 4) incision and drainage with loose packing without antibiotics. The results suggest that treatment with antibiotics may marginally reduce recurrence rates. A randomized, double-blinded, placebo-controlled trial from the 1980s included 50 patients who received incision and drainage with normal saline irrigation and loose packing and then were randomized to cephradine or placebo for 7 days. Because of a high rate (96%) of resolution in each group, the authors concluded that antibiotics were not justified in patients with normal host defenses after incision and drainage of an abscess. The abstract is a randomized, placebo-controlled trial of cephalexin after incision and drainage in a population in which MRSA was highly prevalent. Of the 110 cultures that grew S. aureus isolates, 93% of patients had clinical resolution in the placebo arm, compared with 86% in antibiotic arm. In the placebo group, 89% of wounds that grew MRSA had clinical resolution; compared with 88% in the cephalexin arm, this argues against empiric antibiotics. In a prospective observational study of 69 children who presented to the emergency department for treatment of a cutaneous abscess that grew MRSA in culture, all of the patients who were discharged from the ED on antibiotics concordant with sensitivity testing improved, as did 94% in the group with inappropriate (discordant) antibiotics. The study concluded that for SSTIs of less than 5 cm in children without co-morbidities, incision and drainage is adequate and antibiotics may not be necessary. A prospective, multicenter study1 assessing the prevalence of CA-MRSA among adult patients suggested that incision and drainage alone may be sufficient treatment for simple cutaneous abscesses. The last study was a retrospective review of 441 cultured abscesses, 284 grew MRSA, and 259 of these were treated with discordant antibiotics. Of the discordant antibiotic-treated abscesses, 99.1% had full resolution; 98.8% of concordant antibiotic-treated abscesses had full resolution. This suggests that antibiotics may be unnecessary after incision and drainage.
In conclusion, the available literature does not support prescribing antibiotics after incision and drainage of simple cutaneous abscesses, even in areas where MRSA is highly prevalent.
Commentary
This article was included in the best available evidence section of Annals of Emergency Medicine, which includes articles with enough evidence to draw a reasonable conclusion, but where sufficient literature to make an evidence-based systematic review to support guidelines is lacking.
Of the 6 studies reviewed, 2 of them where performed before there was the high prevalence of CA-MRSA that is encountered now. The abstract compared cephalexin, an antibiotic not clinically effective against MRSA, versus placebo, so it is difficult to say if an antibiotic that has susceptible coverage of CA-MRSA would be beneficial. In the remaining 3 studies, the conclusion was based on the fact that discordant antibiotic therapy did not have an advantage over concordant antibiotic therapy; a placebo was not included. A multi-center, double-blinded, randomized, placebo-controlled clinical trial is needed to make a stronger conclusion, but with the information that is available, routine administration of antibiotics may not be of any benefit.
Are Clinicians Altering Prescription Practices Because of CA-MRSA?
Source:Gupta K, MacIntyre A, Vanasse G, et al. Trends in prescribing beta-lactam antibiotics for treatment of community-associated methicillin-resistant Staphylococcus aureus infections. J Clin Microbiol 2007;45:3930-3934.
Gupta et al investigated the molecular epidemiology of CA-MRSA and the prescribing patterns of antibiotics for SSTIs at their hospital from January 2004 to December 2006. They reviewed the medical records of patients who had a MRSA positive culture and met the epidemiological definition of CA-MRSA, defined as no hospitalizations within the last year, no history of MRSA colonization or infection, and culture obtained within 48 hours of hospital admission, as well as a susceptibility pattern sensitive to most antibiotics. Molecular testing also was performed on MRSA isolates. The medical records were reviewed to verify the community-associated epidemiology, the initial antimicrobial agent prescribed, and whether or not incision and drainage was performed. The prevalence of CA-MRSA SSTIs was found by dividing the number of patients with CA-MRSA SSTIs by the number of patients with any S. aureus SSTIs.
The authors found that the prevalence of CA-MRSA increased for each of the 3 years of the study from 9% in 2004 to 21% in 2006. Molecular testing found that 92% of confirmed CA-MRSA strains were positive for PVL over the 3-year period. The majority of patients with SSTIs underwent incision and drainage, and the rate of using a beta-lactam as initial empirical therapy for SSTIs due to CA-MRSA decreased each year of the study from 86% in 2004 to 60% in 2006.
Commentary
This study demonstrates the increased prevalence of CA-MRSA along with the decreased prescription of beta-lactams, suggesting that clinicians are recognizing CA-MRSA and tailoring treatment. Although there is a trend of decreased beta-lactam antibiotic prescriptions, it is not as significant as the increase in CA-MRSA SSTIs. In the last year of the study (2006), 60% of patients presenting with CA-MRSA SSTIs still received a beta-lactam antibiotic.
The study was conducted at one hospital, so the generability of the results may be limited. It also does not address whether the prescription of antibiotics, beta-lactam or not, made a difference in outcome.
What Should Be the Focus for Prevention of CA-MRSA SSTIs?
Source:Miller LG, Diep BA. Clinical practice: colonization, fomites, and virulence: rethinking the pathogenesis of community-associated methicillin-resistant Staphylococcus aureus infection. Clin Infect Dis 2008;46:752-760.
This review article addresses the pathogenesis of CA-MRSA infection in the context of colonization, fomites, and virulence. Clinical practice and medical studies have tried to investigate ways to eliminate CA-MRSA colonization, especially from the nares, as a way to decrease infection. This practice originates from strategies to prevent infection of HA-MRSA. However, CA-MRSA has a different pathogenesis than HA-MRSA, and there are few data on the association of CA-MRSA infection and colonization of the nares by this pathogen. In CA-MRSA, skin-skin and skin-fomite contact may represent more important transmission routes; outbreaks of CA-MRSA have been associated with broken skin and contaminated fomites such as towels, whirlpools, stethoscopes, and workstations.
The prevalence of MRSA increased remarkably with the emergence of CA-MRSA clone US300, which now accounts for more than 50% of all S. aureus infections. The presence of PVL is strongly associated with US300, as well as other strains. Once regarded as a strong virulence factor, the role of PVL in the pathogenesis of CA-MRSA is unclear. Another genetic element, Type I arginine catabolic mobile element (ACME), is linked to increased virulence of CA-MRSA and is thought to enhance the growth and survival of US300 in human skin.
Commentary
This article points out that CA-MRSA is unique from HA-MRSA and that prevention of this infection needs to be treated differently than what has been employed for HA-MRSA. More studies are needed to determine the most effective and efficient means of prevention, but it may be more beneficial to focus on decontaminating fomites and protecting skin integrity rather than decolonization methods. Although prevention of infection by decolonization has been tried with agents such as mupirocin and chlorhexidine washes, these often have high recurrence rates in the long term. Standard prevention measures should be employed first before resorting to these more aggressive measures.
Conclusion
CA-MRSA is a significant cause of SSTI today. Although its prevalence varies geographically, it is on the rise. Because of CA-MRSA there are new concerns regarding the management of SSTIs. As established practice, the primary treatment for abscesses is incision and drainage; prescribing antibiotics after this primary treatment is of uncertain benefit. Antibiotics come with their own risks, including side effects, allergic reactions, and emerging resistance. Much of the literature concludes that antibiotics are not necessary because discordant antibiotic therapy does not seem to have a significant failure rate after incision and drainage. However, there is a lack of prospective, randomized, placebo-controlled trials.
With the emergence of CA-MRSA, there has been a change from the practice of empirically prescribing a beta-lactam antibiotic for SSTIs. However, this deviation has not been as quick or significant as the proportion of CA-MRSA that now causes SSTI. TMP-SMX is clinically effective against CA-MRSA, although it is not approved by the FDA for this purpose. It is important to keep in mind that TMP-SMX does not cover group A streptococcus; therefore, it would not be unreasonable to add a beta-lactam if it was thought to be needed. Linezolid covers both MRSA and group A streptococcus, but is expensive, has dose- and duration-dependent adverse effects, and there is fear of CA-MRSA developing resistance.
The pathogenesis of CA-MRSA is different than HA-MRSA. Although nasal colonization has been associated with infection of HA-MRSA, skin-skin contact and skin-fomite contact may be more important with CA-MRSA. Therefore, standard precautions and patient education should be the first line of prevention.
Reference
1. Moran GJ, Krishnadasan A, Gorwitz RJ, et al. Methicillin-resistant S. aureus infections among patients in the emergency department. N Engl J Med 2006;355:666-674.
Methicillin-resistant Staphylococcus aureus (MRSA) outside of the hospital setting has complicated the management of skin and soft-tissue infections (SSTIs). Healthcare-associated MRSA (HA-MRSA) has been studied for some time, but with the emergence of community-associated MRSA (CA-MRSA) there are new concerns regarding pathogenesis, treatment, and prevention.Subscribe Now for Access
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