Methicillin-resistant Staphylococcus aureus (MRSA) was first described in the United Kingdom in 1961 shortly after methicillin was introduced.1 Initially, MRSA was associated with hospitalized patients and those possessing established risk factors such as indwelling catheters, previous surgical/wound debridement or antibiotic use, dialysis, intravenous drug use, and immunosuppression.2,3 This pathogen, subsequently termed hospital-acquired MRSA (HA-MRSA), is molecularly distinct from its equally virulent counterpart, community-associated MRSA (CA-MRSA), which is now on the rise among populations without associated risk factors.4 Today MRSA remains a major public health concern in both hospital and community settings.
Epidemiology
CA-MRSA infections are recognized by investigators all over the world as a problem of epidemic proportions.1,3 The first report of CA-MRSA in patients without risk factors occurred in Australia in 1993, but did not gain national attention until it was described in athletes and prisons in Los Angeles in 2002.1 The first cases of children diagnosed with CA-MRSA were reported in 1998. Since then, the pathogen has been reported throughout the world, affecting both rural and urban areas with isolated outbreaks occurring in distinct communities.1,2,3,4
CA-MRSA is frequently reported in close-contact settings such as sport teams, prisons, daycare centers and the military. It is also seen more frequently seen among certain ethnicities including Native Americans, Alaskan Natives and Pacific Islanders.1,2,3,4
Clinical Manifestations
The presentation of CA-MRSA ranges from its most common manifestation of skin and soft-tissue infections to fatal necrotizing pneumonias, sepsis, osteomyelitis, toxic shock syndrome and pyelonephritis.3
Skin Manifestations
The most common skin manifestation in CA-MRSA is a solitary abscess or furuncle with or without accompanying cellulitis.3 CA-MRSA infections that present as red and tender papules are commonly misinterpreted as spider or insect bites.3 The incidence of CA-MRSA-associated lesions varies greatly, ranging from 3% to 25% in folliculitis and from 7% to 20% in impetigo.3 Acute paronchia involving the nail fold or the adjacent soft tissue of the toe or finger has also been reported to be associated with CA-MRSA infections.3
Severe Complications
Severe complications of CA-MRSA infections have been described in cases that are initially neglected or insufficiently treated. These include complex cellulitis infections, which may develop further into infectious myositis and/or osteomyelitis. In addition, virulent CA-MRSA isolates positive for Panton Valentine Leukocidin toxin have been associated with lethal post-influenza necrotizing pneumonias.
Systemic Infections
Most systemic infections present clinically as leucopenia, hemoptysis, and furunculosis, frequently progressing to a fatal outcome with a mortality rate often exceeding 25%.1,2,3 Necrotizing fasciitis and necrotizing myositis have been described in eight patients with CA-MRSA–associated abscesses.3
Invasive Infections
Although CA-MRSA has been traditionally associated with a full recovery in healthy children, there have been occasional reports of invasive infections and some fatalities.5 A study at Texas Children’s Hospital in Houston revealed severe sepsis and coagulopathy in 12 adolescents with CA-MRSA–associated infections out of 14 Staphyloccocus aureus infections total.5 Thirteen of these patients exhibited pulmonary involvement with associated bone and/or joint infection.5
Anticipation of CA-MRSA
As the incidence of this microbe continues to increase, it is important that effective treatment and infection control programs are implemented to help curb the mortality, morbidity, and financial burden associated with CA-MRSA.
Within the office, clinicians should always consider CA-MRSA as a potential pathogen in cases of impetigo or cellulitis and culture infections early.
A general recommendation for the management of suspected CA-MRSA skin infections is to always culture within the initial visit, especially when incision and drainage are required.
Treatment
Treatment of a CA-MRSA infection depends on the severity of the infection, the type of skin and soft tissue infection and the patient’s risk factors for MRSA.
Incision and Drainage
The most important therapy for CA-MRSA–associated skin infections, especially abscesses, is incision and drainage. Although depending on the severity of the infection, antibiotics may be used, most uncomplicated abscesses with a diameter less than 5 cm respond to drainage alone.6
A prospective study by Lee et al following children with CA-MRSA–associated abscesses illustrates this point. In this study, antibiotics were given to all patients and drainage was performed in 96% of patients.6 Only 7% percent of the patients were prescribed an effective antibiotic. There was no significant difference in response in patients who received an antibiotic that was susceptible to their isolate compared to those who did not.1,2,6
However, these recommendations should be taken with caution as other investigators have noted a worsening or recurrence of CA-MRSA and severe complications where incision and drainage were performed but appropriate antibiotics were withheld.3
Antibiotics
A general consensus is that antibiotics should not replace drainage for the treatment of abscesses, but should be used instead as adjunctive therapy. A delay in drainage or the administration of effective antibiotics may lead to adverse effects.
As noted earlier, a general recommendation for the management of suspected CA-MRSA skin infections is to culture early. If a culture is not performed during an initial visit and the infection progresses, subsequent cultures may be negative despite poor pathogen susceptibility.
The choice of antibiotic therapy in the treatment of CA-MRSA infections depends on the severity of the infection and the prevalence of MRSA in the community.3 In a community with a higher rate of methicillin-sensitive Staphylococcus aureus (MSSA) than MRSA, or in uncomplicated S. aureus skin infections, initial empiric antibiotic therapy choices may consist of a cephalosporin, a penicillinase-resistant penicillin, or a beta-lactam/beta-lactamase inhibitor combination.3 If cultures from the initial visit come back CA-MRSA–positive, appropriate antibiotics such as sulfonamides or fluoroquinolones may be used while a full nomogram is pending.
Sulfas, particularly trimethoprim-sulfamethoxazole, remain the drugs of choice for confirmed uncomplicated CA-MRSA infections and in areas with a high prevalence of CA-MRSA infections, especially when the rate of inducible clindamycin resistance is high. However, the presence of beta-hemolytic streptococci for which this antibiotic does not provide coverage should be considered, especially when an infection presents as erypselas or cellulitis.1,3,7 In such cases, the addition of beta-lactam antibiotics is recommended in combination with traditional TMP-SMX antibiotic treatment.
Tetracyclines serve as another alternative to treatment of confirmed CA-MRSA cutaneous infections but also do not show activity against beta-hemolytic streptococci. Their use is contraindicated in children 8 years of age and younger.3
Fluoroquinolones have also been widely used in the treatment of MRSA infections and are currently the first-line treatment for hospitalized patients with severe invasive S. aureus infection. Overuse of this broad-spectrum antibiotic has been associated with fluoroquinoline-resistant MRSA and resistance to other bacteria. Thus fluoroquinolone use should be reserved for confirmed susceptible CA-MRSA infections when the use of other antibiotics is contraindicated.1,3
Clindamycin has been traditionally used as empiric therapy for uncomplicated skin infections and can be used alone or in combination therapy with rifampin. A major advantage over trimethoprim-sulfamethoxazole is that clindamycin covers beta-hemolytic streptococci. Due to increasing rates of constitutive and inducible resistance associated with macrolides, clindamycin use is usually not recommended, especially in areas with high rates of resistance (rates greater than 10% to 15%). However, its use remains effective in CA-MRSA–associated invasive infections when used as part of a combination therapy in areas with low reported resistance.
Hospitalized Patient Treatment
Patients with severe CA-MRSA infections requiring hospitalization and parenteral treatment include those who present with fever, large abscesses, hypotension, extensive necrosis or hemorrhage, and gas within infected tissue.1 Certain patient populations such as the immuno-compromised, diabetics and infants younger than 6 months should also be hospitalized.7
Intravenous vancomycin is considered first-line treatment in such cases. However, culture confirmation of MRSA is recommended as beta-lactams and penicillinase-resistant penicillins such as oxacillin and naficillin have been shown to be more effective than vancomycin in the treatment of MSSA.3,7 Also of note, in vitro studies suggest that CA-MRSA isolates are more susceptible to synergistic combinations of vancomycin and gentamycin than vancomycin alone when compared to HA-MRSA strains.
In severely ill patients, linezolid is more effective than vancomycin and can be used as an alternative treatment in patients with impaired renal function or poor venous access. However, it is expensive and serious side effects may include myelosuppression, peripheral neuropathy, and thrombocytopenia.1,2
Other alternatives for severe invasive infections include daptomycin, quinupristin-dalfopristin, tigecycline, ceftobiprole and teicoplanin.1,2,3,5,7
Daptomycin, a cyclic lipopeptide that exhibits concentration-dependent killing, has a success rate similar to that of vancomycin and has shown sensitivity in some MRSA isolates heteroresistant to vancomycin.1,7 Some resistance has been reported and its use has been rendered ineffective in the treatment of CA-MRSA-associated pneumonia due to poor lung tissue penetrance.1
Ceftobiprole medocaril, a new cephalosporin, is currently being investigated as treatment in MRSA infections. Thus far, it has been shown to be of similar efficacy to vancomycin. Further clinical studies are needed to elucidate resistance and the efficacy of these newer agents.
Recurrence Prevention
The recurrence rate of CA-MRSA–associated skin infections is high and depends on the persistence of colonization of the anterior nares. The anterior nares are the most common site of colonization in Staphylococcus aureus, and elimination of the organism at this site may prevent recurrent S. aureus infection.8
Mupirocin is the most effective among topical antibiotics for decolonization of the intranasal CA-MRSA.8 However, its use has decreased due to increasing resistance associated with long-term use.8
A variety of agents have been used in preventing skin surface colonization and include chlorhexidine, povidone iodine, quaternary ammonium compounds, triclosan, and Dakin’s solution.
Cholorhexidine gluconate is the most common antiseptic used in health care settings,1 but has been associated with resistance. This can be overcome by combining alcohol with the chlorhexidine. As a disinfectant, ethanol has shown to be the most effective.
On the Rise
Both HA-MRSA and CA-MRSA infections are increasing in prevalence and becoming a major public health concern. CA-MRSA is genetically distinct from HA-MRSA and most commonly presents as skin and soft tissue infections. Although much less common, complications of CA-MRSA such as necrotizing pneumonia are on the rise and continue to be a major cause of morbidity and mortality in healthcare settings. Thus, a multidisciplinary approach to curbing the growing epidemic should include implementation of active surveillance programs, early detection and treatment of suspicious cutaneous infections, and prevention of transmission by education.
Methicillin-resistant Staphylococcus aureus (MRSA) was first described in the United Kingdom in 1961 shortly after methicillin was introduced.1 Initially, MRSA was associated with hospitalized patients and those possessing established risk factors such as indwelling catheters, previous surgical/wound debridement or antibiotic use, dialysis, intravenous drug use, and immunosuppression.2,3 This pathogen, subsequently termed hospital-acquired MRSA (HA-MRSA), is molecularly distinct from its equally virulent counterpart, community-associated MRSA (CA-MRSA), which is now on the rise among populations without associated risk factors.4 Today MRSA remains a major public health concern in both hospital and community settings.
Epidemiology
CA-MRSA infections are recognized by investigators all over the world as a problem of epidemic proportions.1,3 The first report of CA-MRSA in patients without risk factors occurred in Australia in 1993, but did not gain national attention until it was described in athletes and prisons in Los Angeles in 2002.1 The first cases of children diagnosed with CA-MRSA were reported in 1998. Since then, the pathogen has been reported throughout the world, affecting both rural and urban areas with isolated outbreaks occurring in distinct communities.1,2,3,4
CA-MRSA is frequently reported in close-contact settings such as sport teams, prisons, daycare centers and the military. It is also seen more frequently seen among certain ethnicities including Native Americans, Alaskan Natives and Pacific Islanders.1,2,3,4
Clinical Manifestations
The presentation of CA-MRSA ranges from its most common manifestation of skin and soft-tissue infections to fatal necrotizing pneumonias, sepsis, osteomyelitis, toxic shock syndrome and pyelonephritis.3
Skin Manifestations
The most common skin manifestation in CA-MRSA is a solitary abscess or furuncle with or without accompanying cellulitis.3 CA-MRSA infections that present as red and tender papules are commonly misinterpreted as spider or insect bites.3 The incidence of CA-MRSA-associated lesions varies greatly, ranging from 3% to 25% in folliculitis and from 7% to 20% in impetigo.3 Acute paronchia involving the nail fold or the adjacent soft tissue of the toe or finger has also been reported to be associated with CA-MRSA infections.3
Severe Complications
Severe complications of CA-MRSA infections have been described in cases that are initially neglected or insufficiently treated. These include complex cellulitis infections, which may develop further into infectious myositis and/or osteomyelitis. In addition, virulent CA-MRSA isolates positive for Panton Valentine Leukocidin toxin have been associated with lethal post-influenza necrotizing pneumonias.
Systemic Infections
Most systemic infections present clinically as leucopenia, hemoptysis, and furunculosis, frequently progressing to a fatal outcome with a mortality rate often exceeding 25%.1,2,3 Necrotizing fasciitis and necrotizing myositis have been described in eight patients with CA-MRSA–associated abscesses.3
Invasive Infections
Although CA-MRSA has been traditionally associated with a full recovery in healthy children, there have been occasional reports of invasive infections and some fatalities.5 A study at Texas Children’s Hospital in Houston revealed severe sepsis and coagulopathy in 12 adolescents with CA-MRSA–associated infections out of 14 Staphyloccocus aureus infections total.5 Thirteen of these patients exhibited pulmonary involvement with associated bone and/or joint infection.5
Anticipation of CA-MRSA
As the incidence of this microbe continues to increase, it is important that effective treatment and infection control programs are implemented to help curb the mortality, morbidity, and financial burden associated with CA-MRSA.
Within the office, clinicians should always consider CA-MRSA as a potential pathogen in cases of impetigo or cellulitis and culture infections early.
A general recommendation for the management of suspected CA-MRSA skin infections is to always culture within the initial visit, especially when incision and drainage are required.
Treatment
Treatment of a CA-MRSA infection depends on the severity of the infection, the type of skin and soft tissue infection and the patient’s risk factors for MRSA.
Incision and Drainage
The most important therapy for CA-MRSA–associated skin infections, especially abscesses, is incision and drainage. Although depending on the severity of the infection, antibiotics may be used, most uncomplicated abscesses with a diameter less than 5 cm respond to drainage alone.6
A prospective study by Lee et al following children with CA-MRSA–associated abscesses illustrates this point. In this study, antibiotics were given to all patients and drainage was performed in 96% of patients.6 Only 7% percent of the patients were prescribed an effective antibiotic. There was no significant difference in response in patients who received an antibiotic that was susceptible to their isolate compared to those who did not.1,2,6
However, these recommendations should be taken with caution as other investigators have noted a worsening or recurrence of CA-MRSA and severe complications where incision and drainage were performed but appropriate antibiotics were withheld.3
Antibiotics
A general consensus is that antibiotics should not replace drainage for the treatment of abscesses, but should be used instead as adjunctive therapy. A delay in drainage or the administration of effective antibiotics may lead to adverse effects.
As noted earlier, a general recommendation for the management of suspected CA-MRSA skin infections is to culture early. If a culture is not performed during an initial visit and the infection progresses, subsequent cultures may be negative despite poor pathogen susceptibility.
The choice of antibiotic therapy in the treatment of CA-MRSA infections depends on the severity of the infection and the prevalence of MRSA in the community.3 In a community with a higher rate of methicillin-sensitive Staphylococcus aureus (MSSA) than MRSA, or in uncomplicated S. aureus skin infections, initial empiric antibiotic therapy choices may consist of a cephalosporin, a penicillinase-resistant penicillin, or a beta-lactam/beta-lactamase inhibitor combination.3 If cultures from the initial visit come back CA-MRSA–positive, appropriate antibiotics such as sulfonamides or fluoroquinolones may be used while a full nomogram is pending.
Sulfas, particularly trimethoprim-sulfamethoxazole, remain the drugs of choice for confirmed uncomplicated CA-MRSA infections and in areas with a high prevalence of CA-MRSA infections, especially when the rate of inducible clindamycin resistance is high. However, the presence of beta-hemolytic streptococci for which this antibiotic does not provide coverage should be considered, especially when an infection presents as erypselas or cellulitis.1,3,7 In such cases, the addition of beta-lactam antibiotics is recommended in combination with traditional TMP-SMX antibiotic treatment.
Tetracyclines serve as another alternative to treatment of confirmed CA-MRSA cutaneous infections but also do not show activity against beta-hemolytic streptococci. Their use is contraindicated in children 8 years of age and younger.3
Fluoroquinolones have also been widely used in the treatment of MRSA infections and are currently the first-line treatment for hospitalized patients with severe invasive S. aureus infection. Overuse of this broad-spectrum antibiotic has been associated with fluoroquinoline-resistant MRSA and resistance to other bacteria. Thus fluoroquinolone use should be reserved for confirmed susceptible CA-MRSA infections when the use of other antibiotics is contraindicated.1,3
Clindamycin has been traditionally used as empiric therapy for uncomplicated skin infections and can be used alone or in combination therapy with rifampin. A major advantage over trimethoprim-sulfamethoxazole is that clindamycin covers beta-hemolytic streptococci. Due to increasing rates of constitutive and inducible resistance associated with macrolides, clindamycin use is usually not recommended, especially in areas with high rates of resistance (rates greater than 10% to 15%). However, its use remains effective in CA-MRSA–associated invasive infections when used as part of a combination therapy in areas with low reported resistance.
Hospitalized Patient Treatment
Patients with severe CA-MRSA infections requiring hospitalization and parenteral treatment include those who present with fever, large abscesses, hypotension, extensive necrosis or hemorrhage, and gas within infected tissue.1 Certain patient populations such as the immuno-compromised, diabetics and infants younger than 6 months should also be hospitalized.7
Intravenous vancomycin is considered first-line treatment in such cases. However, culture confirmation of MRSA is recommended as beta-lactams and penicillinase-resistant penicillins such as oxacillin and naficillin have been shown to be more effective than vancomycin in the treatment of MSSA.3,7 Also of note, in vitro studies suggest that CA-MRSA isolates are more susceptible to synergistic combinations of vancomycin and gentamycin than vancomycin alone when compared to HA-MRSA strains.
In severely ill patients, linezolid is more effective than vancomycin and can be used as an alternative treatment in patients with impaired renal function or poor venous access. However, it is expensive and serious side effects may include myelosuppression, peripheral neuropathy, and thrombocytopenia.1,2
Other alternatives for severe invasive infections include daptomycin, quinupristin-dalfopristin, tigecycline, ceftobiprole and teicoplanin.1,2,3,5,7
Daptomycin, a cyclic lipopeptide that exhibits concentration-dependent killing, has a success rate similar to that of vancomycin and has shown sensitivity in some MRSA isolates heteroresistant to vancomycin.1,7 Some resistance has been reported and its use has been rendered ineffective in the treatment of CA-MRSA-associated pneumonia due to poor lung tissue penetrance.1
Ceftobiprole medocaril, a new cephalosporin, is currently being investigated as treatment in MRSA infections. Thus far, it has been shown to be of similar efficacy to vancomycin. Further clinical studies are needed to elucidate resistance and the efficacy of these newer agents.
Recurrence Prevention
The recurrence rate of CA-MRSA–associated skin infections is high and depends on the persistence of colonization of the anterior nares. The anterior nares are the most common site of colonization in Staphylococcus aureus, and elimination of the organism at this site may prevent recurrent S. aureus infection.8
Mupirocin is the most effective among topical antibiotics for decolonization of the intranasal CA-MRSA.8 However, its use has decreased due to increasing resistance associated with long-term use.8
A variety of agents have been used in preventing skin surface colonization and include chlorhexidine, povidone iodine, quaternary ammonium compounds, triclosan, and Dakin’s solution.
Cholorhexidine gluconate is the most common antiseptic used in health care settings,1 but has been associated with resistance. This can be overcome by combining alcohol with the chlorhexidine. As a disinfectant, ethanol has shown to be the most effective.
On the Rise
Both HA-MRSA and CA-MRSA infections are increasing in prevalence and becoming a major public health concern. CA-MRSA is genetically distinct from HA-MRSA and most commonly presents as skin and soft tissue infections. Although much less common, complications of CA-MRSA such as necrotizing pneumonia are on the rise and continue to be a major cause of morbidity and mortality in healthcare settings. Thus, a multidisciplinary approach to curbing the growing epidemic should include implementation of active surveillance programs, early detection and treatment of suspicious cutaneous infections, and prevention of transmission by education.
Methicillin-resistant Staphylococcus aureus (MRSA) was first described in the United Kingdom in 1961 shortly after methicillin was introduced.1 Initially, MRSA was associated with hospitalized patients and those possessing established risk factors such as indwelling catheters, previous surgical/wound debridement or antibiotic use, dialysis, intravenous drug use, and immunosuppression.2,3 This pathogen, subsequently termed hospital-acquired MRSA (HA-MRSA), is molecularly distinct from its equally virulent counterpart, community-associated MRSA (CA-MRSA), which is now on the rise among populations without associated risk factors.4 Today MRSA remains a major public health concern in both hospital and community settings.
Epidemiology
CA-MRSA infections are recognized by investigators all over the world as a problem of epidemic proportions.1,3 The first report of CA-MRSA in patients without risk factors occurred in Australia in 1993, but did not gain national attention until it was described in athletes and prisons in Los Angeles in 2002.1 The first cases of children diagnosed with CA-MRSA were reported in 1998. Since then, the pathogen has been reported throughout the world, affecting both rural and urban areas with isolated outbreaks occurring in distinct communities.1,2,3,4
CA-MRSA is frequently reported in close-contact settings such as sport teams, prisons, daycare centers and the military. It is also seen more frequently seen among certain ethnicities including Native Americans, Alaskan Natives and Pacific Islanders.1,2,3,4
Clinical Manifestations
The presentation of CA-MRSA ranges from its most common manifestation of skin and soft-tissue infections to fatal necrotizing pneumonias, sepsis, osteomyelitis, toxic shock syndrome and pyelonephritis.3
Skin Manifestations
The most common skin manifestation in CA-MRSA is a solitary abscess or furuncle with or without accompanying cellulitis.3 CA-MRSA infections that present as red and tender papules are commonly misinterpreted as spider or insect bites.3 The incidence of CA-MRSA-associated lesions varies greatly, ranging from 3% to 25% in folliculitis and from 7% to 20% in impetigo.3 Acute paronchia involving the nail fold or the adjacent soft tissue of the toe or finger has also been reported to be associated with CA-MRSA infections.3
Severe Complications
Severe complications of CA-MRSA infections have been described in cases that are initially neglected or insufficiently treated. These include complex cellulitis infections, which may develop further into infectious myositis and/or osteomyelitis. In addition, virulent CA-MRSA isolates positive for Panton Valentine Leukocidin toxin have been associated with lethal post-influenza necrotizing pneumonias.
Systemic Infections
Most systemic infections present clinically as leucopenia, hemoptysis, and furunculosis, frequently progressing to a fatal outcome with a mortality rate often exceeding 25%.1,2,3 Necrotizing fasciitis and necrotizing myositis have been described in eight patients with CA-MRSA–associated abscesses.3
Invasive Infections
Although CA-MRSA has been traditionally associated with a full recovery in healthy children, there have been occasional reports of invasive infections and some fatalities.5 A study at Texas Children’s Hospital in Houston revealed severe sepsis and coagulopathy in 12 adolescents with CA-MRSA–associated infections out of 14 Staphyloccocus aureus infections total.5 Thirteen of these patients exhibited pulmonary involvement with associated bone and/or joint infection.5
Anticipation of CA-MRSA
As the incidence of this microbe continues to increase, it is important that effective treatment and infection control programs are implemented to help curb the mortality, morbidity, and financial burden associated with CA-MRSA.
Within the office, clinicians should always consider CA-MRSA as a potential pathogen in cases of impetigo or cellulitis and culture infections early.
A general recommendation for the management of suspected CA-MRSA skin infections is to always culture within the initial visit, especially when incision and drainage are required.
Treatment
Treatment of a CA-MRSA infection depends on the severity of the infection, the type of skin and soft tissue infection and the patient’s risk factors for MRSA.
Incision and Drainage
The most important therapy for CA-MRSA–associated skin infections, especially abscesses, is incision and drainage. Although depending on the severity of the infection, antibiotics may be used, most uncomplicated abscesses with a diameter less than 5 cm respond to drainage alone.6
A prospective study by Lee et al following children with CA-MRSA–associated abscesses illustrates this point. In this study, antibiotics were given to all patients and drainage was performed in 96% of patients.6 Only 7% percent of the patients were prescribed an effective antibiotic. There was no significant difference in response in patients who received an antibiotic that was susceptible to their isolate compared to those who did not.1,2,6
However, these recommendations should be taken with caution as other investigators have noted a worsening or recurrence of CA-MRSA and severe complications where incision and drainage were performed but appropriate antibiotics were withheld.3
Antibiotics
A general consensus is that antibiotics should not replace drainage for the treatment of abscesses, but should be used instead as adjunctive therapy. A delay in drainage or the administration of effective antibiotics may lead to adverse effects.
As noted earlier, a general recommendation for the management of suspected CA-MRSA skin infections is to culture early. If a culture is not performed during an initial visit and the infection progresses, subsequent cultures may be negative despite poor pathogen susceptibility.
The choice of antibiotic therapy in the treatment of CA-MRSA infections depends on the severity of the infection and the prevalence of MRSA in the community.3 In a community with a higher rate of methicillin-sensitive Staphylococcus aureus (MSSA) than MRSA, or in uncomplicated S. aureus skin infections, initial empiric antibiotic therapy choices may consist of a cephalosporin, a penicillinase-resistant penicillin, or a beta-lactam/beta-lactamase inhibitor combination.3 If cultures from the initial visit come back CA-MRSA–positive, appropriate antibiotics such as sulfonamides or fluoroquinolones may be used while a full nomogram is pending.
Sulfas, particularly trimethoprim-sulfamethoxazole, remain the drugs of choice for confirmed uncomplicated CA-MRSA infections and in areas with a high prevalence of CA-MRSA infections, especially when the rate of inducible clindamycin resistance is high. However, the presence of beta-hemolytic streptococci for which this antibiotic does not provide coverage should be considered, especially when an infection presents as erypselas or cellulitis.1,3,7 In such cases, the addition of beta-lactam antibiotics is recommended in combination with traditional TMP-SMX antibiotic treatment.
Tetracyclines serve as another alternative to treatment of confirmed CA-MRSA cutaneous infections but also do not show activity against beta-hemolytic streptococci. Their use is contraindicated in children 8 years of age and younger.3
Fluoroquinolones have also been widely used in the treatment of MRSA infections and are currently the first-line treatment for hospitalized patients with severe invasive S. aureus infection. Overuse of this broad-spectrum antibiotic has been associated with fluoroquinoline-resistant MRSA and resistance to other bacteria. Thus fluoroquinolone use should be reserved for confirmed susceptible CA-MRSA infections when the use of other antibiotics is contraindicated.1,3
Clindamycin has been traditionally used as empiric therapy for uncomplicated skin infections and can be used alone or in combination therapy with rifampin. A major advantage over trimethoprim-sulfamethoxazole is that clindamycin covers beta-hemolytic streptococci. Due to increasing rates of constitutive and inducible resistance associated with macrolides, clindamycin use is usually not recommended, especially in areas with high rates of resistance (rates greater than 10% to 15%). However, its use remains effective in CA-MRSA–associated invasive infections when used as part of a combination therapy in areas with low reported resistance.
Hospitalized Patient Treatment
Patients with severe CA-MRSA infections requiring hospitalization and parenteral treatment include those who present with fever, large abscesses, hypotension, extensive necrosis or hemorrhage, and gas within infected tissue.1 Certain patient populations such as the immuno-compromised, diabetics and infants younger than 6 months should also be hospitalized.7
Intravenous vancomycin is considered first-line treatment in such cases. However, culture confirmation of MRSA is recommended as beta-lactams and penicillinase-resistant penicillins such as oxacillin and naficillin have been shown to be more effective than vancomycin in the treatment of MSSA.3,7 Also of note, in vitro studies suggest that CA-MRSA isolates are more susceptible to synergistic combinations of vancomycin and gentamycin than vancomycin alone when compared to HA-MRSA strains.
In severely ill patients, linezolid is more effective than vancomycin and can be used as an alternative treatment in patients with impaired renal function or poor venous access. However, it is expensive and serious side effects may include myelosuppression, peripheral neuropathy, and thrombocytopenia.1,2
Other alternatives for severe invasive infections include daptomycin, quinupristin-dalfopristin, tigecycline, ceftobiprole and teicoplanin.1,2,3,5,7
Daptomycin, a cyclic lipopeptide that exhibits concentration-dependent killing, has a success rate similar to that of vancomycin and has shown sensitivity in some MRSA isolates heteroresistant to vancomycin.1,7 Some resistance has been reported and its use has been rendered ineffective in the treatment of CA-MRSA-associated pneumonia due to poor lung tissue penetrance.1
Ceftobiprole medocaril, a new cephalosporin, is currently being investigated as treatment in MRSA infections. Thus far, it has been shown to be of similar efficacy to vancomycin. Further clinical studies are needed to elucidate resistance and the efficacy of these newer agents.
Recurrence Prevention
The recurrence rate of CA-MRSA–associated skin infections is high and depends on the persistence of colonization of the anterior nares. The anterior nares are the most common site of colonization in Staphylococcus aureus, and elimination of the organism at this site may prevent recurrent S. aureus infection.8
Mupirocin is the most effective among topical antibiotics for decolonization of the intranasal CA-MRSA.8 However, its use has decreased due to increasing resistance associated with long-term use.8
A variety of agents have been used in preventing skin surface colonization and include chlorhexidine, povidone iodine, quaternary ammonium compounds, triclosan, and Dakin’s solution.
Cholorhexidine gluconate is the most common antiseptic used in health care settings,1 but has been associated with resistance. This can be overcome by combining alcohol with the chlorhexidine. As a disinfectant, ethanol has shown to be the most effective.
On the Rise
Both HA-MRSA and CA-MRSA infections are increasing in prevalence and becoming a major public health concern. CA-MRSA is genetically distinct from HA-MRSA and most commonly presents as skin and soft tissue infections. Although much less common, complications of CA-MRSA such as necrotizing pneumonia are on the rise and continue to be a major cause of morbidity and mortality in healthcare settings. Thus, a multidisciplinary approach to curbing the growing epidemic should include implementation of active surveillance programs, early detection and treatment of suspicious cutaneous infections, and prevention of transmission by education.
