Characteristics of Patients With Healthcare-Associated Infection Due to SCCmecType IV Methicillin-ResistantStaphylococcus aureus

Distribution of Staphylococcal cassette chromosome mec Types and correlation with comorbidity and infection type in patients with MRSA bacteremia

Background

Molecular epidemiological definitions that are based on staphylococcal cassette chromosome mec (SCCmec) typing and phylogenetic analysis of methicillin-resistant Staphylococcus aureus (MRSA) isolates are considered a reliable way to distinguish between healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). However, there is little information regarding the clinical features and outcomes of bacteremia patients with MRSA carrying different SCCmec types.

Methods

From January 1 through December 31, 2006, we recorded the demographic data and outcomes of 159 consecutive adult MRSA bacteremia patients from whom isolates for SCCmec analysis were collected. All participants were patients at a tertiary care center in Taiwan.

Principal Findings

The following SCCmec types were identified in MRSA isolates: 30 SCCmec II (18.9%), 87 SCCmec III (54.7%), 22 SCCmec IV (13.8%), and 20 SCCmec V (12.6%). The time from admission to the first MRSA-positive blood culture for patients infected with isolates with the SCCmec III element (mean/median, 50.7/26 days) was significantly longer than for patients infected with isolates carrying SCCmec IV or V (mean/median, 6.7/3 days for SCCmec IV; 11.1/10.5 days for SCCmec V) (P<0.05). In univariate analysis, community onset, soft tissue infection, and deep-seated infection were predictors for SCCmec IV/V. In multivariate analysis, length of stay before index culture, diabetes mellitus, and being bedridden were independent risk factors associated with SCCmec II/III.

Conclusions

These findings are in agreement with previous studies of the genetic characteristics of CA-MRSA. MRSA bacteremia with SCCmec II/III isolates occurred more among patients with serious comorbidities and prolonged hospitalization. Community onset, skin and soft tissue infection, and deep-seated infection best predicted SCCmec IV/V MRSA bacteremia.

Clinical characteristics, outcomes, and microbiologic features associated with methicillin-resistant Staphylococcus aureus bacteremia in pediatric patients treated with vancomycin

Vancomycin is the first-line therapy for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, but its efficacy in adult patients has been questioned. Less is known about the outcomes of MRSA bacteremia treated with vancomycin in pediatric patients. This study reviews the outcomes and clinical characteristics of MRSA bacteremia in children treated with vancomycin and characterizes the microbiologic and molecular features of the bloodstream isolates. A retrospective cohort study was conducted among pediatric patients with MRSA bacteremia treated with vancomycin for >5 days from 1 August 2005 to 31 May 2007 in a large tertiary care center. MRSA bloodstream isolates were characterized by antimicrobial susceptibility testing, PCR analysis of virulence genes, and Diversilab typing. Clinical records were reviewed for outcomes and comorbidities. A total of 22 pediatric patients with MRSA bacteremia were identified. Eleven cases (50.0%) were considered vancomycin treatment failures. Features significantly associated with vancomycin treatment failure were prematurity (P = 0.02) and isolates positive for Panton-Valentine leukocidin (PVL) (P = 0.008). Features typically associated with community-associated MRSA strains were identified in hospital-associated isolates. A dominant clone was not responsible for the high number of treatment failures. Further studies are needed to determine if vancomycin should be the first-line treatment for MRSA bacteremia in premature infants and for PVL-positive isolates.

Rapid Emergence of Co-colonization with Community-acquired and Hospital-Acquired Methicillin-Resistant Staphylococcus aureus Strains in the Hospital Setting

BACKGROUND: Community-acquired methicillin-resistant Staphylococcus aureus (CA- MRSA), a novel strain of MRSA, has recently emerged and rapidly spread in the community. Invasion into the hospital setting with replacement of the hospital-acquired MRSA (HA-MRSA) has also been documented. Co-colonization with both CA-MRSA and HA-MRSA would have important clinical implications given differences in antimicrobial susceptibility profiles and the potential for exchange of genetic information. METHODS: A deterministic mathematical model was developed to characterize the transmission dynamics of HA-MRSA and CA-MRSA in the hospital setting and to quantify the emergence of co-colonization with both strains RESULTS: The model analysis shows that the state of co-colonization becomes endemic over time and that typically there is no competitive exclusion of either strain. Increasing the length of stay or rate of hospital entry among patients colonized with CA-MRSA leads to a rapid increase in the co-colonized state. Compared to MRSA decolonization strategy, improving hand hygiene compliance has the greatest impact on decreasing the prevalence of HA-MRSA, CA-MRSA and the co-colonized state. CONCLUSIONS: The model predicts that with the expanding community reservoir of CA-MRSA, the majority of hospitalized patients will become colonized with both CA-MRSA and HA-MRSA.

Emergence of SCCmec type IV and SCCmec type V methicillin-resistant Staphylococcus aureus containing the Panton-Valentine leukocidin genes in a large academic teaching hospital in central Switzerland: external invaders or persisting circulators?

The hospital epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) has changed in the past few years due to the encroachment of community-associated MRSA (CA-MRSA) strains into health care settings. MRSA strains that were isolated during a 2-year period from patients of the Luzerner Kantonsspital were analyzed to elucidate their epidemiology. Moreover, extended surveillance of individuals who were contacts of those patients was carried out for 6 months to identify the routes of spread and to assess the quality of the infection control measures used in our setting. Patient data were collected to distinguish CA-MRSA strains from health care-associated MRSA (HA-MRSA) strains by epidemiological criteria, as defined by the Centers for Disease Control and Prevention (CDC). On the basis of the CDC definition, the majority of the strains were considered to be HA-MRSA. However, 87% of them belonged to staphylococcal cassette chromosome mec (SCCmec) types IV and V, which are traditionally associated with CA-MRSA. Surprisingly, classical nosocomial SCCmec types I and II represented a minority, whereas SCCmec type III was completely absent. By PFGE analysis, four predominant clonal lineages and 21 highly variable sporadic genotypes were detected. Twenty-eight percent of the MRSA strains studied carried the genes encoding the Panton-Valentine leukocidin (PVL), of which 21% and 83% were associated with SCCmec types IV and V, respectively. Among 289 contact individuals screened for MRSA carriage throughout the extended surveillance, a single secondary patient was discovered. The possibility of nosocomial transmission could be excluded. The high proportions of SCCmec type IV and V strains as well as PVL-positive strains suggest strong infiltration of CA-MRSA into our institution. Moreover, the low endemic prevalence of MRSA demonstrates that current infection control measures are sufficient to limit its spreading and the emergence of large epidemic outbreaks.

Bench-to-bedside review: Understanding the impact of resistance and virulence factors on methicillin-resistant Staphylococcus aureus infections in the intensive care unit

Methicillin-resistant Staphylococcus aureus (MRSA) displays a remarkable array of resistance and virulence factors, which have contributed to its prominent role in infections of the critically ill. We are beginning to understand the function and regulation of some of these factors and efforts are ongoing to better characterize the complex interplay between the microorganism and host response. It is important that clinicians recognize the changing resistance patterns and epidemiology of Staphylococcus spp., as these factors may impact patient outcomes. Community-associated MRSA clones have emerged as an increasingly important subset of Staphyloccocus aureus and MRSA can no longer be considered as solely a nosocomial pathogen. When initiating empiric antibiotics, it is of vital importance that this therapy be timely and appropriate, as delays in treatment are associated with adverse outcomes. Although vancomycin has long been considered a first-line therapy for serious MRSA infections, multiple concerns with this agent have opened the door for existing and investigational agents demonstrating efficacy in this role.

Retrospective review of the use of daptomycin for diabetic foot infections

The increase in antibiotic resistance has led to a search for alternative treatments for diabetic foot infections. This retrospective review outlines the clinical outcomes reported for a lipopetide for these infections.

Community-associated meticillin-resistant Staphylococcus aureus infections: epidemiology, recognition and management

Meticillin-resistant Staphylococcus aureus (MRSA) is an important cause of infection, particularly in hospitalized patients and those with significant healthcare exposure. In recent years, epidemic community-associated MRSA (CA-MRSA) infections occurring in patients without healthcare risk factors have become more frequent. The most common manifestation of CA-MRSA infection is skin and soft tissue infection, although necrotizing pneumonia, sepsis and osteoarticular infections can occur. CA-MRSA strains have become endemic in many communities and are genetically distinct from previously identified MRSA strains. CA-MRSA may be more capable colonizers of humans and more virulent than other S. aureus strains. Specific mechanisms of pathogenicity have not been elucidated, but several factors have been proposed as responsible for the virulence of CA-MRSA, including the Panton-Valentine leukocidin, phenol-soluble modulins and type I arginine catabolic mobile element. The movement of CA-MRSA strains into the nosocomial setting limits the utility of using clinical risk factors alone to designate community- or healthcare-associated status. Identification of unique genetic characteristics and genotyping are valuable tools for MRSA epidemiological studies. Although the optimum pharmacological therapy for CA-MRSA infections has not been determined, many CA-MRSA strains remain broadly susceptible to several non-beta-lactam antibacterial agents. Empirical antibacterial therapy should include an MRSA-active agent, particularly in areas where CA-MRSA is endemic.

Differences between "classical" risk factors for infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and risk factors for nosocomial bloodstream infections caused by multiple clones of the staphylococcal cassette chromosome mec type IV MRSA strain

OBJECTIVE

To identify risk factors associated with nosocomial bloodstream infections caused by multiple clones of the staphylococcal cassette chromosome mec (SCCmec) type IV strain of methicillin-resistant Staphylococcus aureus (MRSA).

DESIGN

An unmatched case-control study (at a ratio of 1:2) performed during the period from October 2002 through September 2003.

SETTING

A 2,000-bed tertiary care teaching hospital affiliated with the University of São Paulo in São Paulo, Brazil.

METHODS

Case patients (n=30) were defined either as patients who had a bloodstream infection due to SCCmec type IV MRSA diagnosed at least 48 hours after hospital admission or as neonates with the infection who were born in the hospital. Control patients (n=60) were defined as patients with SCCmec type III MRSA infection diagnosed at least 48 hours after hospital admission. Genes encoding virulence factors were studied in the isolates recovered from case patients, and molecular typing of the SCCmec type IV MRSA isolates was also done by pulsed-field gel electrophoresis and multilocus sequence typing.

RESULTS

In multivariate analysis, the following 3 variables were significantly associated with having a nosocomial bloodstream infection caused by SCCmec type IV strains of MRSA: an age of less than 1 year, less frequent use of a central venous catheter (odds ratio [OR], 0.07 [95% confidence interval {CI}, 0.02-0.28]; p= .025), and female sex. A second analysis was performed that excluded the case and control patients from the neonatal unit, and, in multivariate analysis, the following variables were significantly associated with having a nosocomial bloodstream infection caused by SCCmec type IV strains of MRSA: less frequent use of a central venous catheter (OR, 0.12 [95% CI, 0.03-0.55]; p= .007), lower Acute Physiology and Chronic Health Evaluation II score on admission (OR, 0.14 [95% CI, 0.03-0.61]; p= .009), less frequent surgery (OR, 0.21 [95% CI, 0.06-0.83]; p= .025), and female sex (OR, 5.70 [95% CI, 1.32-24.66]; p= .020). Of the 29 SCCmec type IV MRSA isolates recovered from case patients, none contained the Panton-Valentine leukocidin, gamma-hemolysin, enterotoxin B or C, or toxic shock syndrome toxin-1. All of the isolates contained genes for the LukE-LukD leukocidin and alpha-hemolysin. Genes for enterotoxin A were present in 1 isolate, and genes for beta-hemolysin were present in 3 isolates.

CONCLUSIONS

"Classical" risk factors do not apply to patients infected with the SCCmec type IV strain of MRSA, which is an important cause of nosocomial bacteremia. This strain infects a patient population that is less ill and has had less frequent invasive procedures than a patient population infected with the multidrug-resistant strain of SCCmec type III MRSA. We found that virulence factors were rare and that Panton-Valentine leukocidin was absent. There were multiple clones of the SCCmec type IV strain in our hospital. Children under 1 year of age were at a higher risk. There was a predominant clone (sequence type 5) in this patient population.

Cost-effectiveness analysis of linezolid vs. vancomycin in treating methicillin-resistant Staphylococcus aureus complicated skin and soft tissue infections using a decision analytic model

PURPOSE

To evaluate the cost-effectiveness of vancomycin vs. linezolid in complicated skin and soft tissue infections (cSSTIs) with methicillin-resistant Staphylococcus aureus (MRSA) using a decision analytic (DA) model.

METHODS

A DA model was created to evaluate the cost-effectiveness of four treatment strategies in the treatment of MRSA cSSTIs: linezolid intravenous (i.v.) to oral (LIN), vancomycin i.v. inpatient treatment (VAN-1), vancomycin i.v. switch to oral linezolid (VAN-2) and vancomycin i.v. switch to outpatient vancomycin i.v. (VAN-3). Probabilities were determined from published clinical trials. Incremental cost-effectiveness ratios for the various strategies were the primary outcome. Univariate (one-way) sensitivity analysis and second-order Monte Carlo simulation (using 10,000 trials) were conducted for all parameters used in the model.

RESULTS

The DA model predicted that VAN-3 was the most cost-effective strategy from the base-case analysis. Average cost-effectiveness ratio for this strategy was $26,831.42/cure. Univariate sensitivity analysis revealed that the model was sensitive to linezolid duration of inpatient stay and duration of i.v. vancomycin before switching to an oral agent or discharged with outpatient i.v. administration with vancomycin. Probabilistic sensitivity analysis showed that VAN-1 was dominated by LIN, but LIN was only 30% cost-effective compared with VAN-3. Acceptability curve showed that the probability of choosing LIN as a cost-effective strategy compared with VAN-1, VAN-2 and VAN-3 increased as the willingness-to-pay (WTP) increased.

CONCLUSION

Alternative vancomycin strategies (VAN-2 and VAN-3) that take advantage of early discharge opportunities were cost-effective compared with LIN. However, LIN's higher efficacy would make it cost-effective for payers with a high WTP threshold.

Modeling the invasion of community-acquired methicillin-resistant Staphylococcus aureus into hospitals

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has traditionally been associated with infections in hospitals. Recently, a new strain of MRSA has emerged and rapidly spread in the community, causing serious infections among young, healthy individuals. Preliminary reports imply that a particular clone (USA300) of a community-acquired MRSA (CA-MRSA) strain is infiltrating hospitals and replacing the traditional hospital-acquired MRSA strains. If true, this event would have serious consequences, because CA-MRSA infections in hospitals would occur among a more debilitated, older patient population.

METHODS

A deterministic mathematical model was developed to characterize the factors contributing to the replacement of hospital-acquired MRSA with CA-MRSA and to quantify the effectiveness of interventions aimed at limiting the spread of CA-MRSA in health care settings.

RESULTS

The model strongly suggests that CA-MRSA will become the dominant MRSA strain in hospitals and health care facilities. This reversal of dominant strain will occur as a result of the documented expanding community reservoir and increasing influx into the hospital of individuals who harbor CA-MRSA. Competitive exclusion of hospital-acquired MRSA by CA-MRSA will occur, with increased severity of CA-MRSA infections resulting in longer hospitalizations and a larger in-hospital reservoir of CA-MRSA.

CONCLUSIONS

Improving compliance with hand hygiene and screening for and decolonization of CA-MRSA carriers are effective strategies. However, hand hygiene has the greatest return of benefits and, if compliance is optimized, other strategies may have minimal added benefit.

Emergence of the USA300 strain of methicillin-resistant Staphylococcus aureus in a burn-trauma unit

Community-associated methicillin-resistant Staphylococcus aureus (MRSA), particularly USA300, is a major pathogen in the outpatient setting. We suspected that USA300 had been introduced into our burn-trauma unit (BTU) when three burn patients presented with numerous simultaneous abscesses. We did molecular typing on 206 MRSA isolates from all patients on the BTU who had MRSA isolated from either nares cultures or clinical specimens obtained between April 11, 2002 and October 24, 2006. We reviewed medical records for all patients who had USA300 and for 75 control patients. Twenty-five of 206 (12.1%) patients who were colonized (n = 3) or infected (n = 22) with MRSA had USA300. Thirteen patients had abscesses drained surgically and eight had necrotizing fasciitis excised. Seven patients had burns (mean burn size 11.8 +/- 3.4%), of who four (66.7%) acquired numerous simultaneous (3-33) abscesses. Fourteen patients acquired USA300 outside of the BTU, and three acquired this strain on the BTU. Cases were more likely to have been hospitalized or to have had an operation in the 6 months before they were hospitalized than were controls (P = .001 for both). To our knowledge, this is the first study to describe numerous simultaneous MRSA abscesses in burn patients. The MRSA strain USA300 may be introduced onto burn units from the community by patients admitted with skin and soft tissue infections, especially abscesses and necrotizing fasciitis. Burn patients may be at risk for numerous abscesses with USA300, because they have open wounds and their immune systems may be compromised.

Role of SCCmec type in outcome of Staphylococcus aureus bacteremia in a single medical center

Staphylococcus aureus virulence factors may determine infection presentation. Whether SCCmec type-associated factors play a role in S. aureus bacteremia is unclear. We conducted a prospective observation of adult inpatients with S. aureus bacteremia (1 November 2005 to 31 December 2006), performed SCCmec typing of methicillin-resistant S. aureus (MRSA) isolates, and stratified the results according to SCCmec type. We studied 253 patients. MRSA accounted for 163 (64.4%) cases. The illness severity index was similar in MRSA and methicillin-sensitive S. aureus (MSSA) cases. MRSA caused higher in-hospital mortality (23.9% versus 8.9%; P=0.003), longer bacteremia (4.7+/-6.5 days versus 2.7+/-2.9 days; P=0.01), but similar metastatic infection (14.7% versus 15.6%). Stratifying the results according to SCCmec type revealed significant differences. SCCmec type II caused highest mortality (33.3%) versus type IVa (13.5%), other MRSA (12.5%), and MSSA (8.9%). SCCmec IVa produced the highest metastatic infection (26.9% versus 9.1% [SCCmec II], 8.3% [other MRSA], and 15.6% [MSSA]). Persistent bacteremia (>or= 7 days) was similar in all SCCmec types (16.7 to 20.7%); each exceeded MSSA (6.7%; P=0.05). In multivariate analysis, SCCmec II was a predictor of mortality (odds ratio [OR]=3.73; 95% confidence interval [CI] = 1.81 to 7.66; P=0.009), SCCmec IVa was a predictor of metastatic infection (OR=3.52; CI=1.50 to 8.23; P=0.004), and MRSA (independent of SCCmec type) was a predictor of persistent bacteremia (OR=4.16; CI=1.47 to 11.73; P=0.007). These findings suggest that SCCmec-associated virulence factors play a role in the outcome of S. aureus bacteremia. Additional studies are needed to identify which virulence factors are the determinants of increased mortality with SCCmec type II and metastatic infection with SCCmec type IVa.

Spread of methicillin-resistant Staphylococcus aureus USA300 in a neonatal intensive care unit

BACKGROUND

Reports of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in neonatal intensive care units (NICU) and in otherwise healthy patients without obvious risk factors have been increasing in frequency. Described herein is a cluster of cases of CA-MRSA USA300 strains in an NICU affecting infants, health-care workers and the health-care workers' families.

METHODS

Infants and health-care workers with infection and colonization due to MRSA between 1 January 2004 and 30 June 2005 in a tertiary care center NICU in San Antonio, TX were studied. Antimicrobial susceptibility testing and polymerase chain reaction detection of the mecA gene characterized the MRSA isolates. All MRSA cases were reviewed for clinical severity of infection and outcome.

RESULTS

During the 18 months studied, a total of four (0.6%) of 676 infants had CA-MRSA bacteremia or colonization. One infant with necrotizing pneumonia died and three health-care workers who directly cared for the infected infants developed soft-tissue infections caused by CA-MRSA. Four family members of two health-care workers subsequently developed soft-tissue infections. All of the analyzed isolates (eight of nine) belonged to pulsed-field type USA300 and possessed Panton-Valentine leukocidin genes, which have been associated with severe skin and soft-tissue infections, and necrotizing pneumonia.

CONCLUSIONS

It is likely that the CA-MRSA USA300 strain can be transmitted between NICU patients to health-care workers and their family members. The CA-MRSA cases reported here reinforce the virulence of CA-MRSA USA300 strains and emphasize the need to embrace infection control practices designed to protect hospitalized patients, health-care workers and their family members.

The role of molecular methods in the prevention of nosocomial methicillin-resistant Staphylococcus aureus clusters in cancer patients

In 2002, an increased incidence of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) in our institution triggered a conventional investigation that failed to identify a common source. Molecular typing of the 70 nosocomial MRSA isolates obtained identified a predominant health care-associated clone A in the first trimester. Aggressive infection control measures led to a significant decrease in the number of isolates per 10,000 hospital days between the first trimester and the last 2 trimesters of 2003 (6.4 vs 3.8; P = .04). This was attributed to a decrease in clone A: SCCmec II, USA100, PVL gene-negative (2.3 per 10.000 patient-days vs 0.1 per 10,000 patient-days; P = .004). However, in 2003, 23% of the nosocomial isolates were SCCmec IV, USA300, PVL gene-positive. At that time, molecular methods allowed the detection and prevention of a nosocomial MRSA outbreak caused by a health care-associated clone; however, the community strains (SCCmec IV) have become a frequent cause of nosocomial infection in our institution.

Community strains of methicillin-resistant Staphylococcus aureus as potential cause of healthcare-associated infections, Uruguay, 2002-2004

Community-associated MRSA appears to be replacing healthcare-associated MRSA strain types in at least 1 facility and is a cause of healthcare-onset infections.

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.

Resistance profiles in surgical-site infection

Surgical-site infections (SSIs) remain a common complication, affecting some 5% of patients undergoing surgical procedures and can sometimes present a major challenge after surgery with life-threatening septic illness. The appearance of organisms that are often resistant to common antibiotic treatment is of great concern. Staphylococcus aureus is the organism most commonly recovered from infected surgical wounds, and usually contaminates wounds from the patients own skin. SSIs occur despite appropriate skin disinfection, sterilization of instruments, use of gown and gloves, appropriate sterile technique and prophylactic antimicrobials. In fact, it is difficult to maintain a sterile field over time, and most wounds become contaminated throughout the course of surgery. Methicillin-resistant S. aureus (MRSA) first arose in the hospital setting, but have more recently evolved in the community. Such community-acquired MRSA are genetically different and seem to be even more virulent owing to genes that encode virulence factors, such as staphylococcal cassette chromosome mec type IV and Panton-Valentine leukocidin. The purpose of this review is to summarize characteristics of frequently isolated bacterial strains from SSIs. The focus will be on Gram-positive organisms because of their increasing prevalence in SSIs and their high potential to develop resistance against several antibiotic agents, including vancomycin.

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.

Hospital-acquired infections in the NICU: epidemiology for the new millennium

Nosocomial infections are an important cause of morbidity and mortality in the preterm neonate. Extrinsic and intrinsic risk factors make the preterm neonate particularly susceptible to infection. This review focuses on two major pathogens that cause nosocomial infection, Candida and methicillin-resistant Staphylococcus aureus. The difficult diagnosis of meningitis in the neonate also is discussed.

USA300 genotype community-associated methicillin-resistant Staphylococcus aureus as a cause of surgical site infections

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains are increasingly recovered from nosocomial settings. We conducted a retrospective study of surgical site infections (SSI) during 2004 and 2005 to determine the prevalence of CA-MRSA; 57% of MRSA strains tested belonged to the USA300 genotype. CA-MRSA has become a prominent cause of SSI at our institution.

Methicillin-resistant Staphylococcus aureus in critical care areas

In recent years the mainstay of treatment for hospital-associated MRSA infections has been vancomycin, but now vancomycin intermediate S aureus strains are beginning to emerge. Complete vancomycin resistant S aureus can develop, possessing the same vanA gene as vancomycin-resistant enterococcus. Four such isolates have been reported, three of which have been in the United States. There are new antibiotics being developed, but there is always a risk of resistance developing. There are some promising new ideas such as staphylococcal conjugate vaccines that reduce the rates of S aureus bacteremia for up to 10 months postimmunization in patients who have end stage renal disease receiving hemodialysis, but studies are ongoing. With all the uncertainty surrounding treatment, at least one medium has remained consistent and effective if used properly--infection control. But this requires complete support of all healthcare workers and hospital administration from the chief medical officer to doctors and nurses to environmental services personnel to take ownership of an effective infection control program. Who will advocate for more stringent infection control policies and for the equipment to successfully carry them out? Who will take the lead by ensuring implementation of infection control policies on a unit is effective? Who will hold themselves and other health care workers including physicians accountable to comply with these infection control policies every time they enter a patient's room? Nurses are on the front lines in the battle against antibiotic-resistant nosocomial infections such as MRSA, and we should not be apathetic or feel we are helpless. It is our duty as patient advocates not to take a spectator role but to answer these questions: "I will."

Antimicrobial Susceptibility and Staphylococcal Chromosomal CassettemecType in Community- and Hospital-Associated Methicillin-ResistantStaphylococcus aureus

STUDY OBJECTIVE

To differentiate the characteristics of community-associated methicillin-resistant Staphylococcus aureus (MRSA) and hospital-associated MRSA isolates on the basis of their susceptibility profiles, induction of clindamycin resistance, and staphylococcal chromosomal cassette (SCC) mec types.

DESIGN

In vitro molecular and susceptibility study of isolates obtained from December 2004-January 2006 as part of a large, ongoing clinical study.

SETTING

Level I trauma center in Detroit, Michigan. BACTERIAL STRAINS: Three hundred eight MRSA isolates randomly collected from patients; 130 were classified as community-associated, and 178 were classified hospital-associated by using definitions from the Centers for Disease Control and Prevention (CDC).

INTERVENTION

Minimum inhibitory concentrations were tested on the basis of current guidelines from the Clinical and Laboratory Standards Institute.

MEASUREMENTS AND MAIN RESULTS

All tested MRSA isolates were susceptible to daptomycin, linezolid, and vancomycin. In addition, community-associated MRSA isolates were significantly (all p < or = 0.05) more susceptible to trimethoprim-sulfamethoxazole (99%), clindamycin (96%), and a fluoroquinolone (76%) than hospital-associated MRSA isolates. Inducible resistance to clindamycin was demonstrated in 8.4% of community-associated MRSA isolates versus 50% of hospital-associated MRSA isolates (p < or = 0.001). Of interest, 35% of the MRSA isolates collected from hospitalized patients (> 48 hrs after admission and according to the CDC definition) possessed SCCmec type IV.

CONCLUSION

Overall, inducible clindamycin resistance occurred at significantly higher rates in the hospital-associated MRSA isolates, susceptibility differed significantly between community- and hospital-associated MRSA, and most of the hospital isolates contained SCCmec type IV.