Community-Acquired MRSA in the Wound Clinic

  Despite its global impact, community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) remains at its most prevalent here in the US.¹ And within the US, it may just be that our outpatient wound care clinics have yet to actually feel the full force of the deadly bacteria. Yes, the worst may be yet to come.    “The most common presentation of CA-MRSA is skin and soft-tissue infections (SSTIs), and as a result, wound care clinics are likely to see an increase in the number and the complexity of wound infections,” said Buddy Creech, MD, MPH, assistant professor of pediatric infectious diseases at Vanderbilt University, Nashville, TN.   As Creech explains, boils and skin abscesses are not necessarily the type of symptoms that keep healthcare providers tossing and turning all night; but they are, by volume, the most problematic, especially when considering the presence of CA-MRSA.    “In the last year or two, the rates for CA-MRSA seem to have plateaued, but staph is a master adapter,” Creech said. “Every few years staph appears in a slightly different version — neonatal sepsis in the 1960s, menstrual-associated toxic shock syndrome in women during the ’70s and ’80s, hospital infections in the ’80s and ’90s, and now CA-MRSA. Therefore, we always have to be diligent to recognize staph’s many different ‘colors.’”   It’s tough to predict just how prevalent CA-MRSA will become in the wound clinic and other healthcare settings as time passes. Still, there are a few certainties that wound care providers can take heed of when it comes to effective treatment and best practice toward prevention.

MRSA’s Recent Emergence

  One common theory, particularly among the general public and the media, pertaining to the overuse of antibiotics as a cause to MRSA overall is only accurate to a point, explains Robert L. Buka, MD, JD, section chief in the department of dermatology at Mount Sinai School of Medicine, founder and medical director of Bobby Buka MD Dermatology, New York (www.bobbybukamd.com).    “The critics who talk about the overuse when it comes to someone who comes in for the ‘sniffles’ and sore throat when the primary care provider prescribes, say, Augmentin, that kind of inappropriate use of antibiotics for viral issues can rapidly lead to bacterial resistance,” he said. “But the guilty parties are not those who are reaching for antibiotics in the presence of clear [SSTIs].”   In 2008, Talan and colleagues found that about 83% of patients who presented to the emergency department with purulent SSTIs had abscesses, compared to about 79% of admissions for the same complaint in 2004.² Another study found that severe skin infections are the seventh most common reason for hospital admissions among children, whereas in 2000, they ranked 13th.³ Cellulitis, folliculitis/furunculosis, and impetigo have also been identified as cutaneous presentations of CA-MRSA⁴ (see Figures 1 and 2).    “CA-MRSA infections typically begin as skin infections, with patients presenting with single or multiple forms of erythematous pustular skin lesions, commonly progressing to skin abscesses that are usually painful, swollen, draining [pus], and causing fever,” explained Noel Manyindo, MD, MBA, of the Department of Global Health & Population at Harvard School of Public Health. “Central ulceration is sometimes present. Misdiagnosis as folliculitis or insect bite is not uncommon.”   The emergence of CA-MRSA as a more significant problem than healthcare-acquired (HA-MRSA) has occurred in conjunction with the prevalence of cutaneous symptoms over more severe MRSA complications like bone infections and pneumonia. A significant majority of MRSA-related SSTIs are caused by the community-acquired strain compared to the hospital-acquired strain (75% versus 37%, respectively).⁵ This statistic, from 2003, coincides with the time period that CA-MRSA started to appear.    “The emergence of CA-MRSA was really in the first half of the last decade, between about 2000 and 2004,” said Patrick S. Romano, MD, professor of medicine and pediatrics at University of California, Davis School of Medicine. “It was only episodically reported in series before 2000, and then, in larger series starting in 2004, it was apparent that it had become a prominent pathogen, at least for [SSTIs] presenting to emergency departments.”   With these shifts in MRSA subtype and symptomatology, a new patient population has emerged that is atypical of the standard MRSA patient. Once again, the healthcare community, particularly settings like outpatient wound clinics, are thrust under the microscope as carrier suspects.    “Doctors and nurses and respiratory technicians go home at the end of the day, and, unless everybody’s washing 100 percent of the time, they’re going home to kids who have underdeveloped immune systems and diabetic parents who don’t have fully immune-competent immune systems,” Buka said. “MRSA has always had the potential to affect healthy people, [but] those are examples of how CA-MRSA got a foothold in the community. Once it gains that foothold in non-hospitalized patients, we start to see the infection in certain categories of people — boarding schools and dormitory students and people living in close quarters in the community setting and metropolitan areas (see sidebar). We’re seeing this expanding bubble get larger and larger.”   The emergence of CA-MRSA in these healthy individuals is indicative of the impact that this new strain is having on people who would not generally be perceived as susceptible to MRSA.    “You have to look no further than those who we would say are some of the healthiest people in our society — young athletes and the military who are on active deployment,” Creech added. “Those are the people that we typically think of as being in very good medical shape and very good physical shape, and they are two groups that have been disproportionately affected by CA-MRSA.”

Burden on Wound Clinics

  As outpatient wound clinics continue to be more susceptible to exposure to patients living with CA-MRSA, they’re also more at risk for being facilitators for its spread in and of themselves. This places a responsibility on wound care clinics as a frontline care planning source to not just detect CA-MRSA more quickly, but to treat and provide education related to infection prevention and spread of the bacteria more effectively.   On the basic level, this can be accomplished through non-strenuous means in the clinic such as practicing strict hand hygiene, cleaning equipment before and after patient encounters, and wearing gowns and/or gloves as appropriate when in contact with a patient infected with MRSA or other resistant organisms. However, from a more sophisticated clinical standpoint, the challenge of treating and stalemating CA-MRSA is much greater and troubling, according to Buka.    “We’re probably overdue for a revision of that algorithm of what to do on that first presentation because MRSA is so prevalent,” said Buka, adding that he, too, is seeing an increase in MRSA, as approximately 50 % of his cultures now reveal MRSA compared to about 20 % over the last year. “And I’m talking predominately about community-acquired MRSA. I think a lot of it is handled by primary care physicians who are following the literature as it’s currently posed, which will tell you to start with something like Keflex as the baseline for [SSTI], and we just miss coverage of MRSA — which enables it to spread during that missed period or be partially treated and spread to other contacts.”   Buka was quick to note that he’s not referring to negligence among providers here. “It’s not that primary providers are doing anything ‘wrong,’ it’s that the literature needs revision because what we end up doing is treating half of our infections with something that doesn’t target the bug we’re trying to kill for the first two weeks, and that enables the vector to spread,” he continued. “Making things like doxycycline a first-line agent is something that bears consideration.”   Until then, wound clinics might be best suited to focus on what they can have their patients do when at home to assist in the fight against infection spread, and that amounts to a systematic plan to thwart colonization.    “I don’t think there’s a single patient in my practice who hasn’t ping-ponged his or her MRSA through the rest of the family,” Buka said. “Any person who’s not treated for colonization will give it to another member in their household within three months.”   His recommendations include soaking with a half cup of bleach in a full bathtub for 10 minutes once per week — “that brings bacterial counts down on the skin” — and mupirocin for the nose, peri-anal, axilla, groin area, 3 times per day for 5 days —“in an effort to decrease MRSA in these warm, dark, moist places where we know the bacteria lives.”   This is not intended to be considered a “cure,” however.    “I still see some of these same patients come back once every two or three years, as opposed to once every couple months, if they’re following the regimen,” Buka related. “I would love to have better direction from our infectious disease colleagues as to how to best eliminate MRSA from those areas for good. There are a number of opinions out there, and mixed literature, but there’s no standard of care.”

Defining Current Treatment

  At its core, MRSA, in any form, is a staph infection, which is not a significant challenge clinically; but resistance to the beta-lactam class of antibiotics — the penicillin and cephalosporin antibiotics — is what makes treatment so difficult.   Currently, several strategies are utilized to combat CA-MRSA: antibiotics, incision and drainage (I&D), and prevention of recurrence. In January 2011, the Infectious Diseases Society of America (IDSA) issued an updated version of its clinical guidelines for treating MRSA infections. These guidelines recommend a variety of antibiotics for CA-MRSA: clindamycin (Cleocin), doxycycline (Adoxa, others), tigecycline (Tygacil), trimethoprim-sulfamethoxazole (Bactrim, trimethoprim-sulfamethoxazole) and vancomycin (Vancocin).⁶   Clindamycin. This lincomycin antibiotic is approved by the US Food and Drug Administration (FDA) for treating serious infections caused by S. aureus.⁶ It is widely used in the treatment of SSTIs and has been effective against CA-MRSA in children.^6,7 Some research has suggested the drug works by inhibiting the toxin production that may play a role in MRSA pathogenicity.⁸ There are side effects associated and some resistance to the drug in recent years has raised questions.^4,6 In addition to a resistance that seems, to a degree, regional, clindamycin resistance is also particularly increased in cystic fibrosis patients, making the drug a poor choice for these individuals.⁴ Side effects of clindamycin are primarily gastrointestinal problems.⁶   Doxycycline. Of the tetracyclines available for CA-MRSA, doxycycline is preferred, as it has been shown to have adequate coverage against MRSA and better anti-streptococcal activity.⁴ Doxycycline is FDA-approved for the treatment of SSTIs due to S. aureus, although not specifically for S. aureus infections caused by MRSA. Data on such use are limited.⁶ Recently, there have been concerns about resistance. It appears that CA-MRSA may have inducible resistance to doxycycline through the tetracycline resistance gene tet(K).⁴ Doxycycline is not suggested for use in children younger than 9 because of adverse effects, including discoloration of teeth and inhibition of bone growth.⁴ Other side effects to doxycycline include gastrointestinal intolerance, photosensitivity, drug hypersensitivity, and skin pigmentation.⁴   Tigecycline. This glycylcycline, a derivative of the tetracyclines, is FDA-approved for adults with SSTIs and intra-abdominal infections.⁶ Because it has demonstrated a large volume of distribution and high concentration in tissues and low concentrations in serum, as well as bacteriostatic activity against MRSA, it is not recommended for the treatment of patients with bacteremia.⁶   Trimethoprim-sulfamethoxazole. Known by the brand name Bactrim and abbreviated as TMP-SMX, this drug is “a valuable antibiotic of choice for CA-MRSA.”⁴ While the drug is not FDA-approved for the treatment of any staphylococcal infections, 95%-100% of MRSA strains have been demonstrated as susceptible in vitro, and it has become a strong option for outpatient treatment.⁶ In addition, antibiotic resistance to TMP-SMX has not been identified as a significant problem in facilities where the treatment is used routinely.⁸   Vancomycin. A 15-year study of the changing epidemiology of MRSA revealed that all CA-MRSA isolates in the series were susceptible to vancomycin.⁹ Another study states the drug “is reserved for treatment of infections caused by multi-resistant MRSA strains and for patients with severe systemic infections.”⁵ It is safe and effective for both children and adults.⁶ ISDA guidelines state vancomycin has been “the mainstay of parenteral therapy for MRSA infections,” though it is noted that efficacy has come into question in recent years, particularly because of its slow bactericidal activity, the emergence of resistant strains, and possible “MIC creep” among susceptible strains.⁶   Mupirocin. Recommended, specifically, for nasal decolonization, given twice per day for 5-10 days.⁷   Additionally, chlorhexidine is an agent used by surgeons before a procedure for hand washing, explains Romano, but it is also available in a weaker concentration that can be used for bathing. Some evidence supports the use of chlorhexidine baths for the prevention of recurrent CA-MRSA infections.⁷ These baths work by bringing the bacterial counts on the skin down, according to Buka.

Preventing Recurrence

  Getting rid of MRSA “is the easier part,” explains Buka. “Preventing it from becoming recurrent can be more challenging.”   Creech agrees. “The combination of virulent organism and draining pus [in the wound clinic] is one that makes infection control a nightmare,” he said. “Wound care clinics should be particularly astute at ensuring that infectious organisms from one patient are not spread to another patient.”   A study in Clinical Infectious Diseases from December 2011 compared decolonization of the CA-MRSA-infected individual alone to decolonization of the entire household. The results showed that while household decolonization was not more effective than individual decolonization for eradication of CA-MRSA, decolonization of every individual in the household did decrease recurrent SSTIs.¹⁰ Among 126 of 147 total cases completing the 12-month follow up, “S. aureus was eradicated from 54% of the index group versus 66% of the household group (P = .28). Over 12 months, recurrent SSTI was reported in 72% of cases in the index group and 52% in the household group (P = .02). SSTI incidence in household contacts was significantly lower in the household versus index group during the first 6 months; this trend continued at 12 months.”¹⁰   Proper hygiene is the key to controlling CA-MRSA from the onset. Strategies for halting the spread of the disease can lessen the impact once an individual becomes ill, and there are effective treatment options but efforts are still needed.    “Given that there’s this uncertainty about whether prevention works, our strategy still relies, principally, on early detection of infections and proper treatment when infections arise,” Romano said. “That’s still going to be the primary focus, but that may change as we get more evidence about prevention.”   CA-MRSA is “the most common infection in the United States right now,” Creech stressed. “What we desperately need is a proactive way to prevent it, because those who have been practicing for a long time will tell you that, about every 10-15 years, there’s another wave of a new sort of version of staph infections. What we really need is a vaccine, and there are finally [a few] candidates that are in the pipeline so that, within the next decade, we may see a vaccine that, especially in those who are the highest risk, could prevent the disease from the get-go.”   Buka also points to the ability of the bacteria to continue to adapt when considering the long-range implications for this wound care population.    “The outlook, I think, depends upon how rapidly these bacteria adjust to the agents we now have for MRSA,” he said. “And that’s happening with some of the new antibiotics, like lincomycin, which we use in acute cases where we find a Bactrim-doxycycline-clindamycin resistance. That’s happening, which is frightening, but it’s happening on a very small scale, currently.”   Romano concurs. “I think that our data and others suggests that we’ve probably reached a new equilibrium in terms of the prevalence of the organism in the community and the incidence of associated infections,” he said. “This is not something that’s rising exponentially, it’s not a true epidemic at this point; so we’re at a new equilibrium and it’s changed how we practice medicine, in that you have to use antibiotics that are active against most strains of CA-MRSA, and we have to have a little more readiness with the knife, so to speak, to drain these abscesses before they get too large.”   I&D procedures (see Figures 3 and 4) can be done alone or in combination with antibiotics — the choice of one or both should be made on a case-by-case basis.    “A decade ago, two decades ago, the standard of care for these types of boils was to lance it at the doctor’s office or the emergency room and, as long as the draining procedure went well, you probably didn’t even need antibiotics,” Creech said. “By getting the pus out, you’re also getting the bacteria out. When CA-MRSA came around, people were a little bit nervous to do that, just because we didn’t have proof that it would work; but over time people have felt more comfortable in just draining it and not putting the patient on antibiotics.”   Evaluation of each patient for specific symptoms is the key to determining if and when antibiotics are needed in addition to I&D, according to Romano.    “It’s differentiating whether it’s just cellulitis without a collection of pus, or is there an abscess,” he said. “I think it’s generally accepted that, if there’s an abscess or a collection of pus, that pus needs to be drained. It’s draining the pus, but usually the abscess is surrounded by some cellulitis, some soft tissue infection, and so then the patient usually has to be treated with antibiotics. There are some patients who present only with cellulitis without abscess. One of the features of this organism is that it tends to be more likely to form abscesses than the other pathogens that cause cellulitis.”   A literature review of CA-MRSA in the US from 2011 cites “incision and drainage of purulence and application of heat as the most effective treatment of abscesses regardless of the infecting organism … Antibiotic management of CA-MRSA is different from infections caused by HA-MRSA; therefore, it is important to differentiate the organism through culture and susceptibility confirmation to determine whether CA-MRSA is susceptible to less costly antimicrobials and leave more expensive antibiotics as last resorts.”¹¹ Joe Darrah is managing editor of TWC. Julia Ernst is a contributing writer.

References

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