Epidemiology of methicillin-resistant Staphylococcus aureus at a children's hospital

Identification of botanicals with potential therapeutic use against methicillin-resistant Staphylococcus aureus (MRSA) infections

Staphylococcus aureus is an opportunistic pathogen. Over- and improper-use of pharmaceuticals against S. aureus has led to the development of antibiotic resistance, including methicillin-resistant S. aureus (MRSA). This study examined the efficacy of botanical extracts as an alternative form of treatment to S. aureus and MRSA, including penicillin/methicillin-resistant S. aureus (Pen^R ), and multidrug resistant S. aureus (MDR). Initial screening of botanicals was done via a minimum inhibitory concentration procedure. In addition, a temporal growth curve was performed in order to quantify the growth of the bacteria in the presence of the extracts. Results demonstrated 13 botanicals that had varying activities against S. aureus, Pen^R , and MDR. These botanicals were separated into mild, moderate, and highly efficacious based on the concentration needed to inhibit bacterial growth. These results propose a comparison of botanical-derived antimicrobial extracts that may be utilized against S. aureus and different antibiotic resistant strains of MRSA.

Epidemiology and treatment of community-associated methicillin-resistantStaphylococcus aureusin children

Similar to the epidemiology of methicillin-sensitive Staphylococcus aureus, community-associated methicillin-resistant S. aureus infections occur in children in different regions of the USA and throughout the world. Although minor skin and soft-tissue infections predominate, life-threatening invasive disease and death can result. The novel genetic elements, staphylococcal cassette chromosome mec IV and V, explain the narrow antibiotic resistance pattern, and suggest the mechanism of spread among staphylococci. Panton-Valentine leukocidin apparently plays a role in its pathogenesis. Clindamycin therapy is often effective for treatment, but inducible resistance can develop if the isolate exhibits macrolide resistance due to the erm mechanism. Other drugs displaying in vitro activity against community-associated methicillin-resistant S. aureus include trimethoprim-sulfamethoxazole, tetracyclines, quinolones, linezolid and vancomycin. While experience in pediatric patients is limited, daptomycin, ketolides, glycylcyclines, newer glycopeptides and beta-lactamase-stable cephalosporins may be useful in the future. Further research could include well-designed studies of mechanisms of virulence, continued surveillance of changes in pathogenicity and susceptibility, as well as treatment effectiveness.

Nosocomial transmission of community-acquired methicillin-resistant Staphylococcus aureus in a well-infant nursery of a teaching hospital

BACKGROUND

Infection due to community-acquired strains of methicillin-resistant Staphylococcus aureus (CA-MRSA) has been reported with increasing frequency. Herein is described the nosocomial transmission of CA-MRSA involving 13 neonates and two mothers in a well-infant nursery in a teaching hospital in Saudi Arabia.

METHODS

From October to November 2009, temporally related cases of CA-MRSA skin and soft-tissue infection occurred in newborns shortly after discharge from a well-infant nursery. An outbreak investigation including case identification, review of medical records, staff screening, environmental cultures, pulsed-field gel electrophoresis, and a case-control study were conducted. Controls were selected from among asymptomatic neonates admitted to the same nursery and matched for the day of admission.

RESULTS

Fifteen subjects were found to be CA-MRSA positive: 13 neonates and two mothers. The crude attack rate among neonates was 5.5% during the outbreak period. All 13 neonates presented with skin and soft-tissue infection; one of the mothers had mastitis and a breast abscess. The source of the outbreak was not evident. Pulsed-field gel electrophoresis showed that all of the tested isolates from one strain except one, all contained the staphylococcal cassette chromosome mec (SCCmec) type IV.

CONCLUSION

MRSA strains that initially emerged in the community are now causing disease in health-care settings. Adherence to standard infection control practices, including consistent hand hygiene, in newborn nurseries is important to prevent transmission in such settings.

Methicillin-resistant Staphylococcus aureus colonization and risk of subsequent infection in critically ill children: importance of preventing nosocomial methicillin-resistant Staphylococcus aureus transmission

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) colonization is a predictor of subsequent infection in hospitalized adults. The risk of subsequent MRSA infections in hospitalized children colonized with MRSA is unknown.

METHODS

Children admitted to an academic medical center's pediatric intensive care unit between March 2007 and March 2010 were included in the study. Anterior naris swabs were cultured to identify children with MRSA colonization at admission. Laboratory databases were queried and National Healthcare Safety Network definitions applied to identify patients with MRSA infections during their hospitalization or after discharge.

RESULTS

The MRSA admission prevalence among 3140 children was 4.9%. Overall, 56 children (1.8%) developed an MRSA infection, including 13 (8.5%) colonized on admission and 43 (1.4%) not colonized on admission (relative risk [RR], 5.9; 95% confidence interval [CI], 3.4-10.1). Of those, 10 children (0.3%) developed an MRSA infection during their hospitalization, including 3 of 153 children (1.9%) colonized on admission and 7 of 2987 children (0.2%) not colonized on admission (RR, 8.4; 95% CI, 2.7-25.8). African-Americans and those with public health insurance were more likely to get a subsequent infection (P < .01 and P = .03, respectively). We found that 15 children acquired MRSA colonization in the pediatric intensive care unit, and 7 (47%) developed a subsequent MRSA infection.

CONCLUSIONS

MRSA colonization is a risk factor for subsequent MRSA infection in children. Although MRSA colonized children may have lower risks of subsequent infection than adults, children who acquire MRSA in the hospital have similarly high rates of infection. Preventing transmission of MRSA in hospitalized children should remain a priority.

A nosocomial outbreak of community-associated methicillin-resistant Staphylococcus aureus among healthy newborns and postpartum mothers

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increasingly been isolated from individuals with no predisposing risk factors; however, such strains have rarely been linked to outbreaks in the hospital setting. The present study describes the investigation of an outbreak of CA-MRSA that occurred in the maternal-newborn unit of a large community teaching hospital in Toronto, Ontario.

METHODS

Screening and clinical specimens collected from mothers and newborns delivered during the outbreak period, as well as from staff on the affected unit, were submitted for microbiological testing. Computerized delivery logs and nursing notes were reviewed, and a case control study was conducted.

RESULTS

Analysis by pulsed-field gel electrophoresis revealed 38 babies and seven mothers with MRSA colonization and/or infection by the same unique strain (Canadian MRSA-10-related) from September to December 2004. Isolates were characterized as having the staphylococcal chromosome cassette mec type IVa and were positive for the Panton-Valentine leukocidin gene. No one health care worker was associated with all cases; however, mothers and newborns exposed to one particular nurse (Nurse A) were almost 23 times (odds ratio 22.7, 95% CI 3.3 to 195.9) more likely to acquire MRSA than those with no such contact. MRSA was successfully isolated from Nurse A and from an environmental swab of a telephone recently used by Nurse A; both isolates matched the pulsed-field gel electrophoresis pattern of the outbreak strain.

CONCLUSION

The first nosocomial outbreak of CA-MRSA among healthy newborns and postpartum mothers in Canada is described. Effective control of sustained MRSA transmission within an institution may require prompt identification, treatment and monitoring of colonized and/or infected staff.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Antibiotic management of Staphylococcus aureus infections in US children's hospitals, 1999-2008

OBJECTIVES

The objective of this study was to describe trends in antibiotic management for Staphylococcus aureus infections among hospitalized children from 1999 to 2008.

METHODS

A retrospective study was conducted by using the Pediatric Health Information Systems database to describe antibiotic treatment of inpatients with S aureus infection at 25 children's hospitals in the United States. Patients who were admitted from 1999 to 2008 with International Classification of Diseases, Ninth Revision, Clinical Modification codes for S aureus infection were included. Trends in the use of vancomycin, clindamycin, linezolid, trimethoprim-sulfamethoxazole, cefazolin, and oxacillin/nafcillin were examined for percentage use and days of therapy per 1000 patient-days.

RESULTS

A total of 64813 patients had a discharge diagnosis for S aureus infection. The incidence of methicillin-resistant S aureus (MRSA) infections during this period increased 10-fold, from 2 to 21 cases per 1000 admissions, whereas the methicillin-susceptible S aureus infection rate remained stable. Among patients with S aureus infections, antibiotics that treat MRSA increased from 52% to 79% of cases, whereas those that treat only methicillin-susceptible S aureus declined from 66% to <30% of cases. Clindamycin showed the greatest increase, from 21% in 1999 to 63% in 2008. Similar trends were observed by using days of therapy per 1000 patient-days.

CONCLUSIONS

Antibiotic prescribing patterns for the treatment of S aureus infections have changed significantly during the past decade, reflecting the emergence of community-associated MRSA. Clindamycin is now the most commonly prescribed antibiotic for S aureus infections among hospitalized children. The substantial use of clindamycin emphasizes the importance of continuous monitoring of local S aureus susceptibility patterns.

Trends in incidence of late-onset methicillin-resistant Staphylococcus aureus infection in neonatal intensive care units: data from the National Nosocomial Infections Surveillance System, 1995-2004

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being reported to cause outbreaks in neonatal intensive care units (NICUs). We assessed the scope and magnitude of MRSA infections with disease onset after 3 days of age (late-onset MRSA infections) in NICUs.

METHODS

We analyzed data reported by NICUs participating in the National Nosocomial Infections Surveillance system from 1995 through 2004. For each surveillance month, all healthcare-associated infections as defined by National Nosocomial Infections Surveillance criteria were reported, along with antimicrobial susceptibility patterns of the isolates. We pooled the data from all NICUs by birth weight category and calendar year. Poisson regression was used to assess changes in incidence of late-onset MRSA infections per 10,000 patient-days.

RESULTS

Overall, 149 NICUs reported 4831 S. aureus infections and 5,878,139 patient-days. Methicillin testing data were available for 4302 S. aureus isolates, of which 975 (23%) were MRSA. Incidence of late-onset MRSA infection per 10,000 patient-days, combining all birthweight categories, increased 308% from 0.7 in 1995 to 3.1 in 2004 (P < 0.001). A significant increase in incidence of MRSA infections was observed among all 4 birthweight categories analyzed separately (<or=1000 g, 1001-1500 g, 1501-2500 g, and >2500 g). The distribution of MRSA infection by type of infection did not vary during the study period; 299 (31%) of MRSA infections were bloodstream infections, 174 (18%) were pneumonia, and 161 (17%) were conjunctivitis.

CONCLUSION

The incidence of late-onset MRSA infections increased substantially between 1995 and 2004, indicating a need to reinforce infection control recommendations and to explore potential sources and routes of transmission.

Report of a hospital neonatal unit outbreak of community-associated methicillin-resistantStaphylococcus aureus

Community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) with the type IV staphylococcal chromosomal cassettemec(SCCmec) is rarely reported as being acquired in hospital. We report a hospital outbreak, in Grampian, Scotland, of eight cases of skin and soft-tissue infections due to such a strain. All patients had been in the labour, delivery and maternity units of a small community hospital during a 7-month period. Typing by pulsed-field gel electrophoresis showed the isolates to be a single strain closely related to the USA800 lineage (paediatric clone) and additional typing confirmed it as ST5-MRSA-IV. Genes for exfoliative toxin A (ETA) and enterotoxin D were detected by PCR in all the isolates although none carried the Panton–Valentine leukocidin gene. Region-wide surveillance of over 6000 MRSA isolates collected from 1998 to 2004 showed that 95 (1·6%) were closely related to the outbreak strain although only 60 carried the ETA gene. The strain has not been seen elsewhere in Scotland.

Treatment strategies for methicillin-resistant Staphylococcus aureus infections in pediatrics

Staphylococcus aureus is an important pathogen that frequently causes clinical disease in children. A wide array of illnesses can be caused by this common pathogen ranging from non-invasive skin infections to severe, life-threatening sepsis. Additionally, as antibacterials have been used to eradicate S. aureus, it has developed resistance to these important therapeutic agents. Methicillin-resistant S. aureus (MRSA) has become an increasing problem in pediatric patients over the past decade. In this review, we discuss the epidemiology, pathogenesis, and treatment options available in treating MRSA infections in children. Specifically, we address the importance of abscess drainage in the treatment of skin and soft tissue infections, the most common clinical manifestation of MRSA infections, and highlight the various agents that are available for treating this common infection. In severe, life-threatening invasive MRSA infections the primary therapeutic option is vancomycin. In cases of MRSA toxic shock syndrome the addition of clindamycin is necessary. In other invasive MRSA infections, such as pneumonia and musculoskeletal infections, the empiric treatment of choice is clindamycin. Finally, newer agents and additional treatment options are discussed.

Skin and soft-tissue infections caused by community-acquired methicillin-resistant Staphylococcus aureus

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection has become epidemic. Skin and soft-tissue infections (SSTIs) are the most frequent forms of the disease. Obtainment of culture specimens is important for documentation of the presence of MRSA and for susceptibility testing to guide therapy. Purulent lesions should be drained whenever possible. In areas where community-acquired MRSA isolates are prevalent, uncomplicated SSTI in healthy individuals may be treated empirically with clindamycin, trimethoprim-sulfamethoxazole, or long-acting tetracyclines, although specific data supporting the efficacy of these treatments are lacking. In healthy patients with small purulent lesions, drainage alone may be sufficient. In patients with complicated SSTI requiring hospitalization or intravenous therapy, vancomycin is the drug of choice because of the low cost, efficacy, and safety. Linezolid, daptomycin, and tigecycline are also effective, although published studies on the last 2 agents for the treatment of SSTI due to MRSA are more limited. Dalbavancin, telavancin, and ceftobiprole are investigational agents that may expand our therapeutic options for the treatment of SSTI caused by MRSA.

Comparison of community-acquired methicillin-resistant Staphylococcus aureus bacteremia to other staphylococcal species in a neonatal intensive care unit

Hospital acquired infections including staphylococcal species are common in neonatal intensive care units. Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was recently observed in our unit. The clinical and laboratory characteristics of all neonates with Staphylococcus aureus bacteremia during an 11-year period were retrospectively reviewed. Three groups of patients were compared: 1. Patients with CA-MRSA defined as MRSA-resistant only to beta-lactams, but sensitive to all other antibiotic groups and carried SCCmec IV. 2. Patients with multi-drug-resistant (MDR)-MRSA and 3. Patients with MSSA (methicillin-sensitive S. aureus). Forty-three neonates with documented S. aureus bacteremia were included. Of these 41 were preterm babies. Eleven infants had CA-MRSA, 20 had MDR-MRSA and 12 had MSSA bacteremia, the Panton-Valentine-Leukocidine gene (pvl-gene) was not present in any of these strains. Risk factors, clinical manifestations and laboratory tests were similar in all three groups studied. Although neonates infected with CA-MRSA were more premature and had more related diseases, the mortality rate was similar in all groups (9.1% in the CA-MRSA group). Skin infections, osteomyelitis or pneumatocele were not observed more frequently in the CA-MRSA group. We did not find significant differences in risk factors or outcomes in neonates in the three groups. One possible explanation for this observation is that the CA-MRSA outbreak strain did not contain the pvl-gene, which has been suggested to be a significant virulence factor.

Pediatric community-acquired methicillin-resistant Staphylococcus aureus infection and colonization: trends and management

PURPOSE OF REVIEW

The scourge of community-acquired methicillin-resistant Staphylococcus aureus in pediatrics continues unabated. This review provides information on changes in epidemiology, therapeutic considerations, and measures to control the epidemic.

RECENT FINDINGS

The epidemiology and clinical manifestations of methicillin-resistant S. aureus have undergone important changes that pose challenges in recognition, diagnosis, and treatment for the pediatrician. Community-acquired methicillin-resistant S. aureus used to be predominantly associated with localized disease among previously healthy children; however, there are recent reports of more invasive and severe diseases with some fatalities. The antibiotic susceptibility pattern is also changing with some community-acquired methicillin-resistant S. aureus having resistance patterns indistinguishable from that of hospital-acquired methicillin-resistant S. aureus. Thus the choice of antibiotics is becoming even more challenging in pediatrics, with an already-limited armamentarium of antibiotics. The management of common skin diseases such as furunculosis and boils now requires close collaboration between the general pediatrician and the infectious diseases specialist.

SUMMARY

As the burden of community-acquired methicillin-resistant S. aureus disease continues to increase, pediatricians must have a high index of suspicion and must institute appropriate antimicrobial therapy based on community or regional antibiotic susceptibility of community-acquired methicillin-resistant S. aureus. There is an urgent need for effective infection control programs, including active surveillance components, to help curb the epidemic.

Contrasting pediatric and adult methicillin-resistant Staphylococcus aureus isolates

Children may share a reservoir of MRSA strains that have an antimicrobial drug resistance profile distinct from that of adults.

We performed a prospective study of all inpatient and outpatient methicillin-resistant Staphylococcus aureus (MRSA) isolates identified at the University of Chicago Hospitals from November 2003 through November 2004. Differences in resistance to non–β-lactam antimicrobial drugs were determined after stratification of the 578 MRSA isolates into 4 groups by patient age (pediatric vs. adult) and onset location (community vs. hospital). Non–β-lactam resistance was significantly greater among the 288 adult than the 177 pediatric community-associated isolates for erythromycin (93.2 vs. 87.0%, p = 0.03), clindamycin (51.8 vs. 7.3%, p<0.001), ciprofloxacin (62.1 vs. 10.7%, p<0.001), gentamicin (11.1 vs. 1.1%, p<0.001), and tetracycline (19.9 vs. 6.4%, p<0.001). In contrast, hospital-associated MRSA isolates from children and adults had similar rates of non–β-lactam antimicrobial drug resistance. In our region, clindamycin is an appropriate empiric therapy of community-associated MRSA infection in children but should be used with caution in adults.

Community-associated methicillin-resistant Staphylococcus aureus in hospital nursery and maternity units

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has rarely been reported in the hospital setting. We report an outbreak of 7 cases of skin and soft tissue infections due to a strain of CA-MRSA. All patients were admitted to the labor and delivery, nursery, or maternity units during a 3-week period. Genetic fingerprinting showed that the outbreak strain was closely related to the USA 400 strain that includes the midwestern strain MW2. All isolates contained the staphylococcal chromosome cassette mec type IV. Genes for Panton-Valentine leukocidin and staphylococcal enterotoxin K were detected in all isolates, and most contained other enterotoxin genes. Testing of nearly 2,000 MRSA isolates collected during citywide surveillance studies from 1999 to 2003 showed that ≈1% were genetically related to MW2. CA-MRSA strain MW2 has been present in this region at least since 1999. This study documents the spread of this strain among healthy newborns at 1 hospital.

MRSA at an English children's hospital from 1998 to 2003

AIMS

To investigate the epidemiological and clinical aspects of MRSA among inpatients and outpatients presenting to hospital.

METHODS

Analysis of demographic, epidemiological, and clinical data collected on 385 children first identified as having MRSA between January 1998 and December 2003 in a 250 bed English children's hospital.

RESULTS

There were 267 inpatients and 118 outpatients. The number of new cases of MRSA declined from 72 in 1998 to 52 in 2003, whereas hospital activity increased. Ninety nine (37.1%) inpatients acquired MRSA outside the hospital; a further 90 occurred among 31 clusters of cases. One hundred and seventy eight (66.7%) inpatients were aged <2 years; cardiac services and paediatric & neonatal surgery accounted for 59.6% of cases. Dermatology and A&E accounted for 51.7% of outpatients; 73.8% of outpatients had recently previously attended the hospital. A total of 13.9% of inpatients with MRSA developed bacteraemia; MRSA accounted for 15% of Staphylococcus aureus bacteraemias. The risk of MRSA bacteraemia in colonised patients, and the proportion of S aureus bacteraemias that were MRSA, varied between specialties. Intravascular devices were the most common source of MRSA bacteraemia (63.4% of cases). The mortality rate was 7.3%.

CONCLUSIONS

Enhanced surveillance of MRSA can identify at-risk patient groups, thus facilitating targeting of control measures. The absence of a link between numbers of cases of acquisition of MRSA and bacteraemia suggests that the rise in MRSA bacteraemia may not solely reflect an increase in MRSA prevalence in children in the UK. The need for larger epidemiological studies is emphasised.

Utility of the Chronic Disease Score and Charlson Comorbidity Index as comorbidity measures for use in epidemiologic studies of antibiotic-resistant organisms

Comorbidity is a known risk factor for antibiotic-resistant bacterial infections. Although aggregate comorbidity measures are useful in epidemiologic research, none of the existing measures was developed for use with this outcome. This study compared the utility of two comorbidity measures, the Charlson Comorbidity Index and the Chronic Disease Score, in assessing the comorbidity-attributable risk of nosocomial infections with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE). Two case-control studies were conducted at the University of Maryland Medical System in Baltimore, Maryland. Cases were inpatients with a first positive clinical culture of MRSA or VRE at least 48 hours postadmission (July 1, 1998-July 1, 2001). Three inpatient controls were randomly selected per case. The MRSA study included 2,164 patients, and the VRE study included 1,948. The scores' discrimination and calibration were measured by using the c statistic and Hosmer-Lemeshow chi-square test. The Charlson Comorbidity Index (c = 0.653) and Chronic Disease Score (c = 0.608) were similar discriminators of MRSA and VRE (c = 0.670 and c = 0.647, respectively). Calibration of the scores was poor for both outcomes (p < 0.05). A revised comorbidity measure specific to resistant infections would likely provide a better assessment of the comorbidity-attributable risk of antibiotic-resistant infections.

Emergence of community-associated methicillin-resistant Staphylococcus aureus at a Memphis, Tennessee Children's Hospital

BACKGROUND

An epidemiologic investigation was performed because of a perceived increase in infections caused by community-associated methicillin-resistant Staphylococcus aureus (MRSA) among children in the greater Memphis area.

METHODS

We reviewed medical records of 289 children evaluated from January 2000 to June 2002 at a children's hospital. Clinical criteria were applied to classify MRSA isolates as community-associated (n=51) or health care-associated (n=138). The relatedness of 33 archived S. aureus isolates was evaluated using pulsed field gel electrophoresis (PFGE) of Sma I-digested genomic DNA; a common pulsed field type was defined as > or = 80 % similarity based on Dice coefficients. PFGE profiles were compared with those in a national database of MRSA isolates.

RESULTS

During the first 18 study months, 46 of 122 MRSA isolates (38%) were community-associated; this proportion increased to 106 of 167 isolates (63%) during the last 12 study months (P <.0001). Community-associated isolates were recovered from normally sterile sites as frequently as were health care-associated isolates (16% versus 13%). PFGE revealed that 15 of 16 community-associated isolates shared a common pulsed field type (USA300) observed in community-associated MRSA infections elsewhere in the United States and characterized by staphylococcal cassette chromosome mec type IV, clindamycin susceptibility and erythromycin resistance mediated by an msr A-encoded macrolide efflux pump.

CONCLUSIONS

Community-associated MRSA has emerged as a potentially invasive pathogen among children in the greater Memphis area, and this phenomenon is not explained by spread of nosocomial strains into the community.

Community-acquired Methicillin-resistant Staphylococcus aureus: Epidemiology and Potential Virulence Factors

Methicillin-resistant Staphylococcus aureus (MRSA) has been isolated from patients in the community. Some of these strains may have origins in the hospital, but others appear to be novel and unrelated to known hospital strains. Community MRSA strains have several distinguishing characteristics that may enable them to more readily colonize and infect otherwise healthy individuals. This article reviews recent publications addressing the epidemiology of MRSA in the community, risk factors associated with carriage, potentially associated virulence factors, and concepts of strain fitness as they pertain to MRSA. MRSA likely will be an increasingly important pathogen in the community.