Healthcare-associated Methicillin-resistant Staphylococcus Aureus Research Articles

Emergence of Community-Associated Methicillin-ResistantStaphylococcus aureusStrains as a Cause of Healthcare-Associated Bloodstream Infections in Korea

The prevalence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains causing bloodstream infection (BSI) has not been studied in Korea. We sought to determine the prevalence of CA-MRSA strains among isolates recovered from patients with MRSA BSIs and to explore epidemiological changes in Korea. We also sought to evaluate clinical characteristics relevant to the development of healthcare-associated BSIs. We prospectively collected consecutive MRSA isolates from patients with BSI at 4 hospitals from July 1 through November 30, 2007, and we also included MRSA isolates recovered from culture of blood samples collected during a previous year (October 1, 2004 through September 30, 2005) at a different hospital. Molecular typing studies were performed, including pulsed-field gel electrophoresis (PFGE), multilocus sequence typing, Staphylococcus protein A (spa) typing, and staphylococcal cassette chromosome mec (SCCmec) typing. We compared the clinical characteristics and outcomes of patients with healthcare-associated BSI due to CA-MRSA strains with those of patients with healthcare-associated BSI due to healthcare-associated MRSA (HA-MRSA) strains. There were 76 cases of MRSA BSI, of which 4 (5.3%) were community-associated and 72 (94.7%) were healthcare-associated. Among the 72 HA-MRSA BSIs, 18 (25%) were community onset, and 54 (75%) were hospital onset. PFGE type D-ST72-spa B-SCCmec type IVA MRSA, the predominant genotype of CA-MRSA in Korea, accounted for 19 (25%) of all 76 MRSA BSIs, including 17 (23.6%) of 72 HA-MRSA BSIs and 11 (20.8%) of 53 hospital-onset HA-MRSA BSIs. Patients with healthcare-associated BSIs due to CA-MRSA strains carrying SCCmec type IVA tended to have fewer healthcare-associated risk factors, compared with patients with healthcare-associated BSIs due to HA-MRSA strains carrying other SCCmec types. The presence of a central venous catheter or other invasive device was the only independent factor differentiating patients infected with hospital-associated genotype strains from patients infected with other strains. Clinical outcomes were similar between both groups. CA-MRSA strains are emerging as a major cause of BSI in healthcare settings in Korea. This changing epidemiology of MRSA poses a challenge to public health and infection control in hospital settings.

Comparison of Community-Associated and Health Care-Associated Methicillin-ResistantStaphylococcus aureusin Canada: Results from CANWARD 2007

BACKGROUND: Community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) differ from health care-associated MRSA (HA-MRSA) in their genotypic and phenotypic characteristics. The purpose of the present study was to compare the demographics, antimicrobial susceptibilities and molecular epidemiology of CA-MRSA and HA-MRSA in Canada. METHODS: In 2007, 385 MRSA isolates were collected from Canadian patients attending hospital clinics, emergency rooms, medical/ surgical wards and intensive care units. Susceptibilities to betalactams, clarithromycin, clindamycin, daptomycin, levofloxacin, linezolid, moxifloxacin, tigecycline, trimethoprim-sulfamethoxazole and vancomycin were determined by Clinical and Laboratory Standards Institute broth microdilution. Strain typing was performed by pulsed-field gel electrophoresis (PFGE) and themecA,nucandpvlgenes were detected by polymerase chain reaction. RESULTS: Of the 385 MRSA, 19.5% were CA-MRSA and 79.2% were HA-MRSA as determined by PFGE. CA-MRSA belonged to PFGE types CMRSA10/USA300 (66.7%) and CMRSA7/USA400 (33.3%); PFGE types identified among HA-MRSA included CMRSA2/USA100/800 (81.6%), CMRSA6 (13.1%), CMRSA1/ USA600 (3.3%), CMRSA5/USA500 (1.3%), CMRSA3 (0.3%) and CMRSA9 (0.3%). Panton-Valentine leukocidin (PVL) was detected in 94.7% of CA-MRSA and 0.7% of HA-MRSA. Resistance rates (CA-MRSA versus HA-MRSA) were 61.3% versus 97.7% to levofloxacin, 73.3% versus 96.7% to clarithromycin, 12.0% versus 74.8% to clindamycin and 0.0% versus 15.4% to trimethoprim-sulfamethoxazole. No MRSA were resistant to vancomycin, linezolid, tigecycline or daptomycin. CONCLUSIONS: CA-MRSA represented 19.5% of all MRSA. CA-MRSA was significantly more susceptible to levofloxacin, clarithromycin, clindamycin and trimethoprim-sulfamethoxazole than HA-MRSA. Of CA-MRSA, 94.7% were PVL-positive while 99.3% of HA-MRSA were PVL-negative. CA-MRSA is an emerging pathogen in Canadian hospitals.

Prevalence of Antimicrobial-Resistant Pathogens in Canadian Hospitals: Results of the Canadian Ward Surveillance Study (CANWARD 2007)

BACKGROUND: Canadian hospitals as well as hospitals worldwide are increasingly faced with antibiotic-resistant pathogens, including multidrug-resistant (MDR) strains. OBJECTIVES: To assess the prevalence of pathogens, including the resistance genotypes of methicillin-resistantStaphylococcus aureus(MRSA), vancomycin-resistant enterococci (VRE) and extendedspectrum beta-lactamase (ESBL)-producingEscherichia coliin Canadian hospitals, as well as their antimicrobial resistance patterns. MEtHODS: Bacterial isolates were obtained between January 1, 2007, and December 31, 2007, inclusive, from patients in 12 hospitals across Canada as part of the Canadian Ward Surveillance Study (CANWARD 2007). Isolates were obtained from bacteremic, urinary, respiratory and wound specimens and underwent antimicrobial susceptibility testing. Susceptibility testing was assessed using the Clinical and Laboratory Standards Institute broth microdilution method. RESULTS: In total, 7881 isolates were recovered from clinical specimens of patients attending Canadian hospitals. The 7881 isolates were collected from respiratory (n=2306; 29.3%), blood (n=3631; 46.1%), wounds/tissue (n=617; 7.8%) and urinary (n=1327; 16.8%) specimens. The 10 most common organisms isolated from 76.5% of all clinical specimens wereE coli(21.6%), methicillin-susceptibleS aureus(13.9%),Streptococcus pneumoniae(8.9%),Pseudomonas aeruginosa(8.0%),Klebsiella pneumoniae(5.8%), MRSA (4.9%),Haemophilus influenzae(4.3%), coagulase-negative staphylococci/taphylococcus epidermidisS (4.0%),Enterococcus species(3.0%) andEnterobacter cloacae(2.1%). MRSA made up 26.0% (385 of 1480) of allS aureus(genotypically, 79.2% of MRSA were health care-associated MRSA and 19.5% were community-associated MRSA), and VRE made up 1.8% of all enterococci (62.5% of VRE had thevanA genotype). ESBLproducingE colioccurred in 3.4% ofE coliisolates. The CTX-M type was the predominant ESBL, with CTX-M-15 as the predominant genotype. With MRSA, no resistance was observed to daptomycin, linezolid, tigecycline and vancomycin, while resistance rates to other agents were: clarithromycin 91.4%, clindamycin 61.8%, fluoroquinolones 88.6% to 89.6%, and trimethoprim-sulfamethoxazole 12.2%. WithE coli, no resistance was observed to ertapenem, meropenem and tigecycline, while resistance rates to other agents were: amikacin 0.1%, cefazolin 14.2%, cefepime 2.0%, ceftriaxone 8.9%, gentamicin 10.6%, fluoroquinolones 23.6% to 24.5%, piperacillin-tazobactam 1.3% and trimethoprim-sulfamethoxazole 26.6%. Resistance rates withP aeruginosawere: amikacin 7.6%, cefepime 11.7%, gentamicin 20.8%, fluoroquinolones 23.4% to 25.1%, meropenem 8.1% and piperacillin- tazobactam 7.3%. A MDR phenotype (resistance to three or more of cefepime, piperacillin-tazobactam, meropenem, amikacin or gentamicin, and ciprofloxacin) occurred frequently inP aeruginosa(10.6%) but uncommonly inE coli(1.2%),K pneumoniae(1.5%),E cloacae(0%) orH influenzae(0%). CONCLUSIONS:E coli,S aureus(methicillin-susceptible and MRSA),S pneumoniae,P aeruginosa,K pneumoniae,H influenzaeandEnterococcusspecies are the most common isolates recovered from clinical specimens in Canadian hospitals. The prevalence of MRSA was 26.0% (of which genotypically, 19.5% was community-associated MRSA), while VRE and ESBL-producingE colioccurred in 1.8% and 3.4% of isolates, respectively. A MDR phenotype is common withP aeruginosain Canadian hospitals.

The Graying of Methicillin-Resistant Staphylococcus aureus

From Rush University Medical Center and Stroger Hospital of Cook County, Chicago, Illinois (both authors). Received August 12, 2008; accepted August 17, 2008; electronically published December 1, 2008. Infect Control Hosp Epidemiol 2008; 30:9-12 2008 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2009/3001-0003$15.00. DOI: 10.1086/592709 Not so long ago, methicillin-resistant Staphylococcus aureus (MRSA) was a quintessential nosocomial pathogen. Over the past few years, however, cases of infection with communityassociated MRSA (CA-MRSA) stricto sensu—that is, infections in patients with no healthcare exposures—have emerged. Most populations affected early appeared to share a characteristic of increased risk of disease spread by direct person-to-person contact (Figure). Since the emergence of CA-MRSA strains, several terms have been used to classify S. aureus strains on the basis of epidemiologic, genotypic, and phenotypic characteristics (Table). These classifications provide rough estimates of likely sources of strains and can be used for epidemiologic tracking. As more healthcare exposures occur among the general population, “healthcare-associated MRSA infection”—cases in which healthcare exposures or risk factors are present in patients whose MRSA infection manifests in the community— have gained attention. However, the lines between categories may be “graying,” with community-associated strains encroaching on hospitals, hospital-associated strains entering the community, and healthcare exposures increasing. The study by Johnson and colleagues in this issue of the journal evaluates MRSA colonization among hospitalized dialysis patients and among healthcare workers on an inpatient dialysis unit. As background, it is known that nasal colonization with S. aureus can be persistent, intermittent, or always absent; that it occurs more frequently in some populations, including hemodialysis patients; and that it usually precedes infection. Surveys of the general US population indicate that the prevalence of nasal colonization with MRSA rose from 0.8% in 2001–2002 to 1.5% in 2003–2004, while the prevalence of S. aureus colonization overall (ie, including both susceptible and resistant strains) decreased from 32.4% to 28.6%. On the basis of nasal culture results, Johnson et al. determined that 33% of dialysis patients in their study were colonized with S. aureus and 21.7% were colonized with MRSA—a 14-fold higher prevalence than national estimates. Johnson et al. identified isolates as being CA-MRSA on the basis of the presence of SCCmec IV genetic elements; colonization with such strains occurred in 38.5% of dialysis patients colonized with MRSA and in 8.3% of the total dialysis population. Among healthcare workers, 31% were colonized with S. aureus, 6% with MRSA, and 2% with CA-MRSA. In case-control analyses, there were few significant differences in demographic characteristics or risk factors between patients colonized with MRSA and patients colonized with methicillin-susceptible S. aureus (MSSA) or between patients colonized with MRSA strains that carried SCCmec II and patients colonized with strains that carried SCCmec IV. Because dialysis patients and healthcare workers were evaluated in different periods, inferences about patient-staff cross-transmission may be unreliable. What is the significance of the findings of Johnson et al.? The 6% prevalence of MRSA colonization among healthcare workers is consistent with the findings of recent studies that examined MRSA colonization among emergency-department

Prevalence of Colonization With Community-Associated Methicillin-ResistantStaphylococcus aureusAmong End-Stage Renal Disease Patients and Healthcare Workers

To evaluate the prevalence, epidemiologic features, and molecular characteristics of colonization with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) among hospitalized dialysis patients and their healthcare workers (HCWs). Prospective observational clinical and laboratory study of nasal colonization. A 600-bed urban academic medical center. One hundred twenty hospitalized dialysis inpatients and 100 HCWs. Of 120 patients, 40 (33%) were colonized with S. aureus; 26 (65%) of these 40 were colonized with MRSA. Among the 26 MRSA isolates, 10 (38.5%) carried staphylococcal cassette chromosome (SCC) mec type IV (ie, CA-MRSA), and 7 of these 10 carried the genes for the Panton-Valentine leukocidin (PVL) toxin. Patients colonized with healthcare-associated MRSA strains and those colonized with CA-MRSA strains were similar, except for a higher frequency of a history of congestive heart failure among those with healthcare-associated MRSA strains (P=.014). Among 10 patients who presented with or developed an S. aureus infection while hospitalized, 8 were colonized with S. aureus, 7 with MRSA, and 3 with SCCmec type IV strains. Among 100 HCWs, 31 were colonized with S. aureus, including 6 with MRSA; 2 of the MRSA isolates belonged to CA-MRSA strains, and soft-tissue infections were reported in one of the HCWs and in the family member of the other HCW colonized with these strains. There is a high rate of colonization with MRSA and CA-MRSA among hospitalized dialysis patients and their HCWs. As other studies have found, it appears that individuals are being colonized with both CA-MRSA strains and healthcare-associated MRSA strains.

Community-Associated Methicillin-Resistant Staphylococcus aureus Colonization in the Upper Respiratory Tracts of Korean Military Recruits

Background: Several large outbreaks have demonstrated the threat of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in close-contact environments, such as occurs during training and quartering of military recruits training. In South Korea, which is a hospital or healthcare-associated MRSA prevalent area, military service is compulsory for all healthy young men. We surveyed and determined the extent of CA-MRSA colonization in the upper respiratory tracts of Korean military recruits. Methods: The Korean military recruits who were enrolled in a military training facility from November 2004 to March 2005 were eligible for this study. Sputum or nasopharyngeal swap was obtained from randomly selected subjects who displayed upper respiratory tract symptoms. Results: Of the 181 participants, 32 participants (17.7%) were colonized with S. aureus, and 12 participants (6.6%) were colonized with MRSA. Among the cases that were colonized with S. aureus, 37.5% (12/32) were colonized with MRSA. Antimicrobial susceptibility testing showed resistant patterns that were suggestive of the CA-MRSA strains for all of the MRSA isolates. Conclusion: This study of Korean military recruits found a great deal of showed MRSA colonization in them, and the antimicrobial resistant profile that was suggestive of a CA-MRSA strain. Further efforts to prevent the spread of MRSA infections and careful monitoring for CA-MRSA outbreaks are warranted, especially in a high risk group such as military recruits.

Multisensitive Panton-Valentine Leukocidin-Positive Methicillin-Resistant Staphylococcus aureus in Kuala Lumpur, Malaysia

Background: Recent years have seen the emergence of methicillin-resistant Staphylococcus aureus (MRSA) strains often characterised by community acquisition, unusual susceptibility to antimicrobials, and the Panton-Valentine leukocidin (PVL) virulence factor. The epidemiology of these strains varies between geographical locations. This study aimed to determine the occurrence and clinical features of such strains in the University of Malaya Medical Centre, Kuala Lumpur. Methods: Laboratory records were examined for MRSA isolates from 2002–2007. Using CLSI disc diffusion standards, multisensitive MRSA was defined as susceptibility to erythromycin, clindamycin, fusidic acid, rifampicin, gentamicin, ciprofloxacin, cotrimoxazole, and tetracycline. PCR detection of mecA and PVL genes lukS-PV-lukF-PV, SCCmec typing, and MLST were carried out. The PVL product was confirmed by sequencing. Only cases with isolates available for PCR confirmation were included in clinical records review. Centers for Diseases Control and Prevention criteria were used to distinguish between community-associated (CA-MRSA) and healthcare-associated MRSA. Results: Multisensitive MRSA from 13 distinct patient-episodes were identified; 1 in 2003, 2 in 2006, and 10 in 2007 (0.27%, 0.62%, and 3.1% of new MRSA cases, respectively). 9 isolates from 2007 were available for mecA confirmation. Of these, only 2 were PVL-positive CA-MRSA; the remaining 7 were healthcare-associated, of which 3 were PVL-positive. All isolates were of SCCmec type IV. There were 3 isolates of each sequence type (ST) ST30 and ST6, 1 ST22 strain, and 2 untypeable isolates. Clinical presentations included skin or soft-tissue infections (6), probable colonisation (2 babies), bacteraemia (1), and no deaths. All 4 isolates unavailable for confirmation were healthcare-associated. Conclusion: We describe the first confirmed clinical infections with multisensitive, SCCmec type IV, PVL-positive MRSA in Malaysia, which were mainly skin or soft-tissue infections. In view of the predominance of healthcare-associated acquisition, and the apparent increase in cases in 2007 (albeit small numbers), further work including multilocus sequence typing is necessary to fully understand the local epidemiology of MRSA.

Prevalence And Antimicrobial Susceptibility Pattern Of Methicillin Resistant <i>Staphylococcus aureus</i> From Healthcare And Community Associated Sources

Methicillin resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen. We report the prevalence and antibiotic susceptibility pattern of MRSA in Amravati, Maharashtra state (India). A total of 150 healthcare-associated (HA) sources (doctors mobiles phone and wound/pus swabs), and 160 community-associated (CA) sources (hand swab) were screened for MRSA and their antibiotic resistance pattern was performed. Out of 41 isolated strains of S. aureus, 77% from HA and 50% CA samples were found to be methicillin resistant. There were high prevalence of MRSA in doctor’s mobile phone (83%) and wound/pus (71%) (HA sources) than the hand swab. Almost all HA and CA MRSA strains were resistant to penicillin and penicillin V (100%) followed by cloxacillin and cephalexin, co-trimoxazole. About 56 - 67% HA and CA-MRSA strains were resistance to erythromycin, ceftazidime, lincomycin, ceftazidime, cephalexin, erythromycin and tetracycline indicating high degree of multi-resistance MRSA prevalence in the region. However, 67% strains of CA and 56% strains of HA were sensitive to vancomycin. The study showed high prevalence of MRSA in hospital setting indicating need of good control measures such as proper hand hygiene, avoiding mobile phone while wound dressing and treating patient, surveillance cultures and monitoring of susceptibility patterns of MRSA may also help in arresting the spread of infections in this part of India.

Community Strains of Methicillin-ResistantStaphylococcus aureusas Potential Cause of Healthcare-associated Infections, Uruguay, 2002–2004

Community-associated MRSA (CA-MRSA) strains have emerged in Uruguay. We reviewed Staphylococcus aureus isolates from a large healthcare facility in Montevideo (center A) and obtained information from 3 additional hospitals on patients infected with CA-MRSA. An infection was defined as healthcare-onset if the culture was obtained >48 hours after hospital admission. At center A, the proportion of S. aureus infections caused by CA-MRSA increased from 4% to 23% over 2 years; the proportion caused by healthcare-associated MRSA (HA-MRSA) decreased from 25% to 5%. Of 182 patients infected with CA-MRSA, 38 (21%) had healthcare-onset infections. Pulsed-field gel electrophoresis determined that 22 (92%) of 24 isolates were USA1100, a community strain. CA-MRSA has emerged in Uruguay and appears to have replaced HA-MRSA strains at 1 healthcare facility. In addition, CA-MRSA appears to cause healthcare-onset infections, a finding that emphasizes the need for infection control measures to prevent transmission within healthcare settings.

Implementation of an Industrial Systems-Engineering Approach to Reduce the Incidence of Methicillin-ResistantStaphylococcus aureusInfection

To measure the effectiveness of an industrial systems-engineering approach to a methicillin-resistant Staphylococcus aureus (MRSA) prevention program. Before-after intervention study. An intensive care unit (ICU) and a surgical unit that was not an ICU in the Pittsburgh Veterans Administration hospital. All patients admitted to the study units. We implemented an MRSA infection control program that consisted of the following 4 elements: (1) the use of standard precautions for all patient contact, with emphasis on hand hygiene; (2) the use of contact precautions for interactions with patients known to be infected or colonized with MRSA; (3) the use of active surveillance cultures to identify patients who were asymptomatically colonized with MRSA; and (4) use of an industrial systems-engineering approach, the Toyota Production System, to facilitate consistent and reliable adherence to the infection control program. The rate of healthcare-associated MRSA infection in the surgical unit decreased from 1.56 infections per 1,000 patient-days in the 2 years before the intervention to 0.63 infections per 1,000 patient-days in the 4 years after the intervention (a 60% reduction; P = .003). The rate of healthcare-associated MRSA infection in the ICU decreased from 5.45 infections per 1,000 patient-days in the 2 years before to the intervention to 1.35 infections per 1,000 patient-days in the 3 years after the intervention (a 75% reduction; P = .001). The combined estimate for reduction in the incidence of infection after the intervention in the 2 units was 68% (95% confidence interval, 50%-79%; P < .001). Sustained reduction in the incidence of MRSA infection is possible in a setting where this pathogen is endemic. An industrial systems-engineering approach can be adapted to facilitate consistent and reliable adherence to MRSA infection prevention practices in healthcare facilities.

Outcome of patients with meticillin-resistant Staphylococcus aureus bacteraemia at an emergency department of a medical centre in Taiwan

The number of patients presenting to the Emergency Department (ED) with meticillin-resistant Staphylococcus aureus (MRSA) is increasing, but few studies focus on patients with bacteraemia. From January 2001 to June 2006 the clinical characteristics and outcome of 177 consecutive patients with MRSA bacteraemia visiting an ED of a university hospital were studied. The average age of the patients was 65.8 years. Healthcare-associated MRSA bacteraemia comprised 76.3% of all cases. Catheter-related bacteraemia was the most common type of infection (22.6%), followed by soft tissue infection (20.9%) and primary bacteraemia (15.3%). Different types of infection were significantly related to different outcome. In-hospital mortality was 33.3%, but the mortality decreased to 17.7% when patients with rapidly fatal disease and mortality within 3 days were excluded. All isolates exhibited lower susceptibility to vancomycin (minimum inhibitory concentration (MIC) 1–2 μg/mL). Factors associated with mortality included severity of underlying illness, severity of bacteraemia and persistent bacteraemia. A detrimental effect of elevated MIC could not be demonstrated despite applying several definitions of patient outcome. Patients admitted to the ED with MRSA bacteraemia carry high overall mortality; however, the severity of underlying illness, severity of bacteraemia and persistent bacteraemia are correlated with mortality, but not vancomycin MICs (2 μg/mL) of MRSA isolates.

Evolutionary relationships between sporadic and epidemic strains of healthcare-associated methicillin-resistant Staphylococcus aureus

National surveillance of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) isolates by pulsed-field gel electrophoresis (PFGE) typing allowed identification of rarely occurring 'sporadic' isolates with patterns significantly distinct from those of major epidemic clones of methicillin-resistant S. aureus (MRSA) circulating in Belgian hospitals. The aim of the present study was to compare the genetic background, antibiotic susceptibility profile and in vitro growth rates of 36 MRSA isolates with either 'epidemic' or 'sporadic' PFGE profiles to identify factors that could be involved in the epidemic behaviour of S. aureus. Sequence analysis of seven housekeeping genes (multilocus sequence typing) and seven surface-associated genes, combined with staphylococcal cassette chromosome mec (SCCmec) typing and spa typing results, segregated sporadic isolates into four groups: (1) isolates phylogenetically distant from epidemic HA-MRSA clones that possessed several properties of community-acquired MRSA strains; (2) isolates derived from the same methicillin-susceptible S. aureus ancestor as epidemic isolates but possessing a distinct type of SCCmec; and (3) and (4) isolates that were closely related to epidemic strains, either as recent descendants of these or as intermediate evolutionary steps between epidemic HA-MRSA strains and their putative ancestors. Sporadic isolates did not show slower growth in vitro than epidemic isolates. These findings suggest that the SCCmec type and insertion/deletion of other mobile genetic elements may be involved in modulating the epidemic behaviour of MRSA strains of similar genetic background, independently of fitness cost.

Community-associated methicillin-resistant Staphylococcus aureus pyomyositis complicated by compartment syndrome in an immunocompetent young woman

Pyomyositis is a bacterial infection of skeletal muscle common in the tropics. Pyomyositis has historically been rare in temperate regions. However, the epidemiology is changing, and over the past decade, the number of cases in the United States and Europe has increased significantly. One major factor appears to be the increase in community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections. This pathogen now accounts for most of the skin and soft tissue infections throughout much of the United States. Most community-associated MRSA infections carry specific virulence factors, most notably the Panton-Valentine leukocidin gene, known to increase invasive capability and predispose to abscess and deep tissue infections. We report a case of a young healthy woman who was initially treated as an outpatient for tendonitis. She presented 3 days later to the emergency department where she was diagnosed with upper extremity pyomyositis complicated by compartment syndrome. A fasciotomy was performed in the operating room, and intraoperative cultures grew MRSA. She did not have any traditional risk factors for the acquisition of health care-associated MRSA. Her subsequent course was complicated by osteomyelitis of the proximal radius. This is the first report of pyomyositis complicated by compartment syndrome in the emergency medicine literature. This case emphasizes the need to remain vigilant for deep muscle infections given the evolving epidemiology. It also highlights possible complications of pyomyositis including the rare but serious complication of compartment syndrome.

Complex Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolates From Children With Cystic Fibrosis in the Era of Epidemic Community-Associated Methicillin-Resistant S aureus

Limited data exist about the molecular types of methicillin-resistant Staphylococcus aureus (MRSA) strains found in children with cystic fibrosis (CF). We sought to characterize MRSA strains from these patients and compare them with MRSA strains from non-CF pediatric patients. All MRSA isolates were collected prospectively at Children's Medical Center in Dallas, TX, and the University of Chicago Comer Children's Hospital in 2004 to 2005. All CF MRSA isolates underwent susceptibility testing, multilocus sequence typing, Panton-Valentine leukocidin gene detection (pvl+), and staphylococcal chromosome cassette mec (SCCmec) typing. A total of 22 of 34 MRSA isolates (64.7%) from patients with CF belonged to clonal complex (CC) 5 and contained SCCmec II, so-called health-care associated MRSA (HA-MRSA) strains. Nine of 34 MRSA strains (26.5%) were CC 8, and contained SCCmec IV, so-called community-associated MRSA (CA-MRSA) strains. The CA-MRSA strains tended to be isolated from newly colonized CF patients. In contrast, CC8 isolates predominated among the non-CF patients (294 of 331 patients; 88.8%). MRSA isolates from children with CF were more likely to be resistant to clindamycin (65% vs 19%, respectively) and ciprofloxacin (62% vs 17%, respectively) compared with strains from non-CF patients (p < 0.001). There was no difference in the rate of pvl+ isolate recovery from children with CF undergoing a surveillance culture (7 of 23 children) compared with those with pulmonary exacerbation (3 of 11 children; p = 1.0). Both CA-MRSA (CC8) isolates and HA-MRSA (CC5) isolates populate the respiratory tracts of children with CF. HA-MRSA isolates predominated, but CA-MRSA strains predominated among CF patients with newly acquired MRSA strains and among the non-CF patients. The presence of CA-MRSA strains in children with CF was not associated with exacerbation or necrotizing pneumonia.

Community-Associated Methicillin-Resistant Staphylococcus aureus as a Cause of Health Care--Associated Infection

From 1975 through 1980, MRSA infection spread to hospitals in previously unaffected areas of the United States, and the number of institutions reporting cases of MRSA infection increased considerably [1], From 1983 through the early 1990s, the prevalence of health care-associated (HA) MRSA infection increased dramatically, and it continued to increase more gradually during the latter half of the 1990s [2, 3]. In 1998, Herold et al. [4] reported an alarming increase in the occurrence of community-associated (CA) MRSA infection among young children with none of the typical risk factors associated with HA MRSA. Within a few years, CA MRSA strains became widely disseminated, accounting for 15%-74% of S. aureus skin and soft-tissue infections seen in emergency departments [5-8]. A recent population-based study of invasive MRSA infection found that 26.6% of infections had onset during a hospitalization, 58.4% were community-onset infections among individuals with previous health care exposures, and 13.7% were CA infections [9]. CA MRSA strains typically have PFGE patterns (e.g., USA300 or USA400) that differ from HA MRSA strains, are staphylococcal cassette chromosome mec type IV or V, produce Panton-Valentine leukocidin (PVL), and are susceptible to most non-/3-lactam antibiotics [6, 10, 11]. The predominant CA MRSA strain in the United States is multilocus sequence type 8 (ST8):USA300:staphylococcal cassette chromosome mec type IVa, whereas the predominant CA MRSA strains in Europe and Oceania are ST80 and ST30, respectively [ 12, 13] . All predominant CA MRSA strains produce PVL, which is strongly associated with the propensity of these organisms to cause skin and soft-tissue infection, necrotizing fasciitis, and necrotizing pneumonia and with the ability of such strains to spread rapidly [14, 15]. USA300 also carries genes for molecular variants of enterotoxins K and Q and a novel arginine catabolic mobile element that encodes an arginine deiminase pathway and oligopeptide permease system, which may contribute to the epidemiological and clinical virulence of USA300 [14]. CA MRSA strains have been introduced into hospitals by the 15%-23% of patients who require hospitalization for management of their infections [7, 8] and most likely by other colonized patients who require hospital admission for other purposes. In 2003, Saiman et al. [16] reported one of the first recognized outbreaks involving transmission of a CA MRSA strain in a health care facility. Subsequently, a number of nosocomial outbreaks, often

Methicillin-Resistant Staphylococcus aureus–Positive Surgical Site Infections in Face-lift Surgery

To determine the incidence of methicillin-resistant Staphylococcus aureus (MRSA)-positive surgical site infections after face-lift surgery and to discuss the screening, prevention, and treatment of such infections. The patient charts of 780 patients who underwent a deep-plane rhytidectomy between 2001 and 2007 were reviewed for postoperative wound infections. Culture results and sensitivities were recorded. To our knowledge, this is the first study that documents MRSA-positive surgical site infections after face-lift surgery. Five of 780 patients (0.6%) who underwent face-lift surgery by the senior surgeon had postoperative surgical site infections. Four of the 5 patients had cultures that were positive for MRSA. Two of these patients (0.3%) required hospitalization and had collections that had to be opened or drained and developed wound breakdown. Both patients eventually responded to wound care along with intravenous and then oral antibiotic therapy. The other 2 MRSA-infected patients responded to oral antibiotic therapy and local wound care alone. The 2 complicated infections occurred on postoperative days 5 and 8. These 2 patients were the only ones among the 5 patients with positive cultures who had known recent contact with another physician or a hospital. All infections occurred in the year 2006, with 3 patients experiencing infection in the last 4 months of the year. Herein, we describe the incidence and sequelae of MRSA infections and colonization. The 2 major different subsets of MRSA are community-acquired MRSA and health care-associated MRSA. Surgical site infections that are positive for MRSA blur this division, which affects many aspects of the course of disease and treatment. We also discuss strategies for screening, preventing, and treating MRSA surgical site infections. Methicillin-resistant S aureus-positive surgical site infection is an increasingly problematic issue in all surgical fields. In the future, MRSA-positive infections will be more prevalent and will require well-developed screening, prevention, and treatment strategies.

Colonization, Fomites, and Virulence: Rethinking the Pathogenesis of Community-Associated Methicillin-Resistant Staphylococcus aureus Infection

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) infection is increasingly common worldwide and causes considerable morbidity and mortality. Of concern, community-associated MRSA infections are often recurrent and are highly transmissible to close contacts. The traditional tenet of pathogenesis is that MRSA colonization precedes infection. This has prompted persons involved in efforts to prevent community-associated MRSA infection to incorporate the use of intranasal topical antibiotics for nasal decolonization. However, data from outbreaks of community-associated MRSA infection suggest that skin-skin and skin-fomite contact represent important and common alternative routes of acquisition of the infecting strain. Furthermore, strain characteristics of the most successful community-associated MRSA strain, USA300, may contribute to a distinct pathogenesis. As we develop strategies to prevent community-associated MRSA infection, we must reconsider the pathogenesis of S. aureus. Reliance on models of health care-associated MRSA transmission for prevention of community-associated MRSA infection may result in the development of flawed strategies that attenuate our ability to prevent this serious and potentially deadly infection.

Antimicrobial-resistant pathogens in intensive care units in Canada: results of the Canadian National Intensive Care Unit (CAN-ICU) study, 2005-2006.

Between 1 September 2005 and 30 June 2006, 19 medical centers collected 4,180 isolates recovered from clinical specimens from patients in intensive care units (ICUs) in Canada. The 4,180 isolates were collected from 2,292 respiratory specimens (54.8%), 738 blood specimens (17.7%), 581 wound/tissue specimens (13.9%), and 569 urinary specimens (13.6%). The 10 most common organisms isolated from 79.5% of all clinical specimens were methicillin-susceptible Staphylococcus aureus (MSSA) (16.4%), Escherichia coli (12.8%), Pseudomonas aeruginosa (10.0%), Haemophilus influenzae (7.9%), coagulase-negative staphylococci/Staphylococcus epidermidis (6.5%), Enterococcus spp. (6.1%), Streptococcus pneumoniae (5.8%), Klebsiella pneumoniae (5.8%), methicillin-resistant Staphylococcus aureus (MRSA) (4.7%), and Enterobacter cloacae (3.9%). MRSA made up 22.3% (197/884) of all S. aureus isolates (90.9% of MRSA were health care-associated MRSA, and 9.1% were community-associated MRSA), while vancomycin-resistant enterococci (VRE) made up 6.7% (11/255) of all enterococcal isolates (88.2% of VRE had the vanA genotype). Extended-spectrum beta-lactamase (ESBL)-producing E. coli and K. pneumoniae occurred in 3.5% (19/536) and 1.8% (4/224) of isolates, respectively. All 19 ESBL-producing E. coli isolates were PCR positive for CTX-M, with bla CTX-M-15 occurring in 74% (14/19) of isolates. For MRSA, no resistance against daptomycin, linezolid, tigecycline, and vancomycin was observed, while the resistance rates to other agents were as follows: clarithromycin, 89.9%; clindamycin, 76.1%; fluoroquinolones, 90.1 to 91.8%; and trimethoprim-sulfamethoxazole, 11.7%. For E. coli, no resistance to amikacin, meropenem, and tigecycline was observed, while resistance rates to other agents were as follows: cefazolin, 20.1%; cefepime, 0.7%; ceftriaxone, 3.7%; gentamicin, 3.0%; fluoroquinolones, 21.1%; piperacillin-tazobactam, 1.9%; and trimethoprim-sulfamethoxazole, 24.8%. Resistance rates for P. aeruginosa were as follows: amikacin, 2.6%; cefepime, 10.2%; gentamicin, 15.2%; fluoroquinolones, 23.8 to 25.5%; meropenem, 13.6%; and piperacillin-tazobactam, 9.3%. A multidrug-resistant (MDR) phenotype (resistance to three or more of the following drugs: cefepime, piperacillin-tazobactam, meropenem, amikacin or gentamicin, and ciprofloxacin) occurred frequently in P. aeruginosa (12.6%) but uncommonly in E. coli (0.2%), E. cloacae (0.6%), or K. pneumoniae (0%). In conclusion, S. aureus (MSSA and MRSA), E. coli, P. aeruginosa, H. influenzae, Enterococcus spp., S. pneumoniae, and K. pneumoniae are the most common isolates recovered from clinical specimens in Canadian ICUs. A MDR phenotype is common for P. aeruginosa isolates in Canadian ICUs.

Etiology and treatment of community-associated methicillin-resistantStaphylococcus aureus

Risk factors and treatment recommendations for community-associated methicillin-resistant Staphylococcus aureus are reviewed. A new strain of methicillin-resistant Staphylococcus aureus (MRSA) has prompted researchers to examine the factors associated with infections acquired in outpatient settings as opposed to those that develop nosocomially. Infections of the skin, lungs, urinary tract, and bloodstream diagnosed within 24-72 hours of hospitalization and with no risk factors present were categorized as community-associated MRSA (CA-MRSA) and differentiated from health-care-associated methicillin-resistant S. aureus (HA-MRSA) on a molecular basis. Pulsed-field electrophoresis has been instrumental in genotyping the S. aureus organism to identify bacterial isolates. Molecular differences between community- and hospital-associated strains show that the organisms were genetically distinct and had not migrated to other settings. Some studies examining antibiotic resistance indicated a steady increase in the rate of MRSA infections. In addition, results of a 15-year longitudinal study indicated significant increases in CA-MRSA-positive isolates between 1991 and 2004. Race, age, sex, hygiene, living environment, and socioeconomic status have been shown to play a key role in the incidence of CA-MRSA. Health care providers should recognize how CA-MRSA and HA-MRSA are differentiated and what factors are associated with infections caused by the organisms. This will enable health care providers to quickly identify and initiate appropriate treatment for these infections.

Methicillin-resistant Staphylococcus aureus: From the hospital to the community

Infections due to community-associated methicillin---resistant Staphylococcus aureus (CA-MRSA) are becoming more prevalent. CA-MRSA infections have unique epidemiologic features and virulence factors. Compared with health care-associated MRSA (HA-MRSA), most CA-MRSA is clonal type USA300 or 400 and has the Staphylococcal cassette chromosome mec type IV, which carries the mecA gene that encodes for resistance to methicillin and other beta-lactam antibiotics but generally not for other antibiotics. CA-MRSA often contains various virulence factors that may result in tissue necrosis. CA-MRSA clinical presentation includes mostly skin and soft tissue infections and less frequently pneumonia. In many of the small soft tissue abscesses due to CA-MRSA, primary treatment with surgical drainage may result in improvement without antibiotic therapy. Optimal treatment and prevention of CA-MRSA infections are unclear. However, distinction between CA-MRSA and HA-MRSA may be less relevant in the future, as CA-MRSA strains are now diagnosed in the hospital setting.