Healthcare-associated Methicillin-resistant Staphylococcus Aureus Research Articles

Varying fitness cost associated with resistance to fluoroquinolones governs clonal dynamic of methicillin-resistant Staphylococcus aureus

The purpose of this study was to investigate the impact of fluoroquinolone resistance on the existence and dynamic of MRSA clones. Resistance to ciprofloxacin was induced in strains of community-acquired (CA) MRSA from various sequence types and the fitness cost suffered by mutant derivatives measured in a propagation assay. In addition, the fitness of fluoroquinolone resistant health care-associated (HA) MRSA isolates from major clones prevalent in Hungary were compared with each other and with those of the CA-MRSA derivatives. The genetic background of fluoroquinolone resistance and fitness cost in CA-MRSA was investigated. The fitness cost observed in the CA-MRSA derivatives proved diverse; the derivatives of the ST30-MRSA-IV strain suffered significantly greater fitness cost than those of the ST8-MRSA-IV and ST80-MRSA-IV isolates. Strains from the New York-Japan (ST5-MRSA-II), South German (ST228-MRSA-I) and EMRSA-15 (ST22-MRSA-IV) HA-MRSA clones proved more viable than CA-MRSA derivatives with similar MIC values to ciprofloxacin and HA-MRSA strains from the Hungarian/Brazilian clone (ST239-MRSA-III). Our strains from the New York-Japan, South-German and EMRSA-15 clones seem to have a competitive edge over the tested CA-MRSA isolates in the health care setting. The greater fitness observed in our New York-Japan and South-German strains could account for the replacement by them of the Hungarian/Brazilian clone in Hungary about ten years ago. Alterations in relevant genes were detected. The Ser80 → Phe mutation in the grlA gene may have seriously compromised viability. Surprisingly silent nucleotide substitutions in the grlB gene seemed to impact fitness in derivatives of the ST30-MRSA-IV isolate.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolated from Children in a Community with Low Antimicrobial Pressure in Japan

Sado Island in Japan is an area with low antimicrobial pressure. A total of 41 community-onset methicillin-resistant Staphylococcus aureus (MRSA) isolates were obtained from pediatric outpatients and healthy children between August 2009 and January 2012, and genotyping and antimicrobial susceptibility testing of the MRSA isolates were performed. Additionally, the sources of MRSA isolated from healthy 1-month-old neonates were assessed. All isolates were negative for the Panton-Valentine leukocidin genes. Our data showed a lower prevalence of staphylococcal cassette chromosome (SCC)mecII on Sado Island (31.7% in total and 46.7% in healthy carriage) than that in the other areas of Japan, suggesting that a low level of antimicrobial use may be related to a low SCCmecII carriage rate in the community. To our knowledge, this is the first report of sequence type (ST)81/SCCmecIVg strains as well as the novel ST strain (ST2180/SCCmecIVa) in Japan. In addition, we detected an arginine catabolic mobile element (ACME)-arcA-positive ST764/SCCmecIIa clone that could disseminate successfully in the community. Intrafamilial transmission was observed in neonates identified with the SCCmecIV MRSA strains, and these strains were genetically typed as community-associated MRSA; the transmission routes of the remaining SCCmecIIa MRSA (genetically typed as healthcare-associated MRSA) strains could not be defined. In this study, we have shown that multiple MRSA strains can circulate in a community even under low antimicrobial pressure.

Changing Epidemiology of S. aureus Infections in the U.S.

The emergence of the USA300 strain as an important cause of community-onset methicillin-resistant Staphylococcus aureus (MRSA) infections in the late 1990s and early 2000s profoundly changed the epidemiology of staphylococcal disease, both in the U.S. and worldwide. Although several recent studies have suggested that the incidence of healthcare-associated and hospital-onset MRSA infections may be decreasing, less …

Impact of a hospital-wide hand hygiene promotion strategy on healthcare-associated infections.

BackgroundDuring the Severe Acute Respiratory Syndrome (SARS) outbreak, high compliance in healthcare workers to hand hygiene was primarily driven by fear. However, the post-SARS period confirmed that this practice was not sustainable. At the Singapore General Hospital, a 1,600-bedded acute tertiary care hospital, the hand hygiene program was revised in early 2007 following Singapore's signing of the pledge to the World Health Organization (WHO) "Clean Care is Safer Care" program.FindingsA multi-prong approach was used in designing the hand hygiene program. This included system change; training and education; evaluation and feedback; reminders in the workplace; and institutional safety climate. Hand hygiene compliance rate improved from 20% (in January 2007) to 61% (2010). Improvement was also seen annually in the compliance to each of the 5 moments as well as in all staff categories. Healthcare-associated MRSA infections were reduced from 0.6 (2007) to 0.3 (2010) per 1000 patient-days.ConclusionsLeadership's support of the program evidenced through visible leadership presence, messaging and release of resources is the key factor in helping to make the program a true success. The hospital was recognised as a Global Hand Hygiene Expert Centre in January 2011. The WHO multi-prong interventions work in improving compliance and reducing healthcare associated infections.

Differences in Methicillin-Resistant Staphylococcus aureus Strains Isolated from Pediatric and Adult Patients from Hospitals in a Large County in California

Studies of U.S. epidemics of community- and health care-associated methicillin-resistant Staphylococcus aureus (MRSA) suggested differences in MRSA strains in adults and those in children. Comprehensive population-based studies exploring these differences are lacking. We conducted a prospective cohort study of inpatients in Orange County, CA, collecting clinical MRSA isolates from 30 of 31 Orange County hospitals, to characterize differences in MRSA strains isolated from children compared to those isolated from adults. All isolates were characterized by spa typing. We collected 1,124 MRSA isolates from adults and 159 from children. Annual Orange County population estimates of MRSA inpatient clinical cultures were 119/100,000 adults and 22/100,000 children. spa types t008, t242, and t002 accounted for 83% of all isolates. The distribution of these three spa types among adults was significantly different from that among children (χ(2) = 52.29; P < 0.001). Forty-one percent of adult isolates were of t008 (USA300), compared to 69% of pediatric isolates. In multivariate analyses, specimens from pediatric patients, wounds, non-intensive care unit (ICU) wards, and hospitals with a high proportion of Medicaid-insured patients were significantly associated with the detection of t008 strains. While community- and health care-associated MRSA reservoirs have begun to merge, significant differences remain in pediatric and adult patient populations. Community-associated MRSA spa type t008 is significantly more common in pediatric patients.

The Epidemiology of Methicillin-Resistant Staphylococcus aureus (MRSA) in Germany

For decades, methicillin-resistant Staphylococcus aureus (MRSA) has been a major cause of infection in hospitals and nursing homes (health care-associated MRSA, HA-MRSA). Beginning in the late 1990s, many countries have also experienced a rising incidence of MRSA infection outside of the health care setting (community-associated MRSA, CA-MRSA). Moreover, animal reservoirs are increasingly considered to represent an important source of human MRSA acquisition. In this review article the authors describe the current epidemiological situation of MRSA in Germany. This review is based on pertinent articles published up to 2010 that were retrieved by a selective PubMed search, as well as on publications issued by national reference institutions up to 2010. There are about 132 000 cases of MRSA in German hospitals each year. MRSA is found in about 18% to 20% of all inpatient-derived culture specimens that are positive for S. aureus. CA-MRSA is not yet endemic in Germany; important risk factors for its acquisition include travel to high-prevalence areas and household contact with persons that harbor a CA-MRSA infection. Agricultural livestock is the main animal reservoir for MRSA, which is often zoonotically transmitted from animals to human beings by direct contact. However, both CA-MRSA and MRSA from animal reservoirs can be imported into hospitals and cause nosocomial infections. Hospitals and nursing homes were once the main reservoirs of MRSA, but new ones have now emerged outside of the healthcare setting. Efforts to prevent MRSA and limit its spread must rise to this new challenge.

Assessment of risk factors related to healthcare-associated methicillin-resistant Staphylococcus aureus infection at patient admission to an intensive care unit in Japan

BackgroundHealthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) infection in intensive care unit (ICU) patients prolongs ICU stay and causes high mortality. Predicting HA-MRSA infection on admission can strengthen precautions against MRSA transmission. This study aimed to clarify the risk factors for HA-MRSA infection in an ICU from data obtained within 24 hours of patient ICU admission.MethodsWe prospectively studied HA-MRSA infection in 474 consecutive patients admitted for more than 2 days to our medical, surgical, and trauma ICU in a tertiary referral hospital in Japan. Data obtained from patients within 24 hours of ICU admission on 11 prognostic variables possibly related to outcome were evaluated to predict infection risk in the early phase of ICU stay. Stepwise multivariate logistic regression analysis was used to identify independent risk factors for HA-MRSA infection.ResultsThirty patients (6.3%) had MRSA infection, and 444 patients (93.7%) were infection-free. Intubation, existence of open wound, treatment with antibiotics, and steroid administration, all occurring within 24 hours of ICU admission, were detected as independent prognostic indicators. Patients with intubation or open wound comprised 96.7% of MRSA-infected patients but only 57.4% of all patients admitted.ConclusionsFour prognostic variables were found to be risk factors for HA-MRSA infection in ICU: intubation, open wound, treatment with antibiotics, and steroid administration, all occurring within 24 hours of ICU admission. Preemptive infection control in patients with these risk factors might effectively decrease HA-MRSA infection.

Risk Factors for Household Transmission of Community-associated Methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a community pathogen. Community-associated (CA) MRSA infections have occurred among multiple members of a household. We describe the incidence of and risk factors for MRSA colonization among household contacts of children with CA-MRSA infections. MRSA-infected children <18 years of age who lacked established healthcare-associated MRSA risk factors were identified through surveillance at 12 Minnesota hospital laboratories. Nasal swab specimens and information on medical history and hygiene behaviors were collected from case-patients and enrolled household contacts during home visits. S. aureus isolates obtained from nasal cultures were screened for oxacillin resistance. In all, 236 households consisting of 236 case-patients and 712 household contacts were enrolled. Home visits were conducted on an average of 69 days after the onset of symptom in case-patients (range: 16-178 days). Twenty-nine (13%) case-patients and 82 (12%) household contacts had MRSA nasal colonization. Nasal MRSA colonization in ≥ 1 household contact occurred in 58 (25%) households. Household contacts who assisted the case-patient to bathe or who shared balms/ointments/lotion with the case-patient were more likely to be colonized (P < 0.01, P < 0.05), whereas those who reported using antibacterial versus nonantibacterial soap for hand washing were less likely to be colonized (P < 0.05) with MRSA clonally related to the case-patient infection isolate. Only 13% of case-patients had MRSA nasal colonization on an average of 69 days after their initial MRSA infection. CA-MRSA colonization may be short-lived or may occur at non-nasal sites. One quarter of households had at least one household contact colonized with MRSA. Modifiable behaviors, such as sharing personal items, may contribute to transmission.

Panton Valentine Leukocidin Exotoxin Has No Effect on the Outcome of Cancer Patients With Methicillin-Resistant Staphylococcus aureus (MRSA) Infections

The presence of Panton-Valentine leukocidin (PVL) gene in methicillin-resistant Staphylococcus aureus (MRSA) infections has been associated with high severity and mortality rates. In this study we evaluated the effect of PVL on outcome in cancer patients with MRSA infections.We retrospectively reviewed the records of 173 cancer patients diagnosed with MRSA pneumonia (n = 47), skin and soft tissue infections (n = 77), and bacteremia (n = 49) between September 2003 and September 2007 at M. D. Anderson Cancer Center. We obtained demographic and clinical data and tested isolates for the presence of PVL. The data were compared between patients with PVL (+) and those with PVL (-) strains. Statistical methods for comparison included Cochran-Mantel-Haenszel tests, 2-way nonparametric analysis of variance, chi-square or Fisher exact tests, and Wilcoxon rank sum tests. All tests were 2-sided with a significance level of 0.05.Seventy patients with PVL (+) strains and 103 patients with PVL (-) strains were included in our study. Fewer PVL (+) patients had pneumonia than did PVL (-) patients (14% vs. 36%, p = 0.002). PVL (-) patients were more likely to have concomitant infections (35% vs. 17%, p = 0.012). The 2 groups were similar in terms of fever, sepsis, vasopressor use, mechanical ventilation, antibiotics response, infection relapse, death, and death due to MRSA. In a skin and soft tissue subset analysis, PVL (+) patients were more likely to have solid tumors (73% vs. 47%, p = 0.02) and less likely to have fever (20% vs. 44%, p = 0.02) and sepsis (12% vs. 36%, p = 0.013). There were no differences in outcome between patients with pneumonia and bacteremia; however, most patients with pneumonia were PVL (-) (79% vs. 21%). Among the 73 patients who received vancomycin and the 20 who received linezolid, there was no difference in response to treatment, regardless of PVL status or neutropenia. In conclusion, the presence of the PVL gene had no negative effect on cancer patients with health care-associated MRSA.

Length of exposure to the hospital environment is more important than antibiotic exposure in healthcare associated infections by methicillin-resistant Staphylococcus aureus: a comparative study

ObjectivesBoth total antimicrobial use and specific antimicrobials have been implicated as risk factors for healthcare-associated methicillin-resistant Staphylococcus aureus (HCA-MRSA) infection. The aims of this study were: (I) to explore predictors of a new HCA-MRSA infection in comparison with a new healthcare-associated methicillin-sensitive Staphylococcus aureus (HCA-MSSA); (II) to thoroughly assess the role of recent antibiotic use qualitatively and quantitatively. MethodsThe time-period for our study was from October 1997 through September 2001. Through applying strict criteria, we identified two groups of inpatients, one with a new HCA-MRSA infection and one with a new HCA-MSSA infection. We recorded demographic, clinical and antibiotic use-related data up to 30 days before the positive culture date. ResultsWe identified 127 and 70 patients for each group, respectively. Two logistic regression models were carried out to assess the role of antimicrobial use (qualitatively and quantitatively). In model I, duration of hospital stay, presence of chronic wounds, aminoglycoside and fluoroquinolone use retained statistical significance. In model II, duration of hospital stay and history of intubation during the last month stood out as the only significant predictors of a subsequent HCA-MRSA infection. No significant differences in outcome were noted. ConclusionsThe length of exposure to the hospital environment may be the best predictor of a new HCA-MRSA infection. Use of aminoglycosides and fluoroquinolones may also stand independently along with presence of chronic ulcers and surgical procedures. No independent association between quantitative antibiotic use and subsequent HCA-MRSA infection was documented.

Is methicillin-resistant Staphylococcus aureus replacing methicillin-susceptible S. aureus?

Despite extensive research on the emergence of and treatments for methicillin-resistant Staphylococcus aureus (MRSA), prior studies have not rigorously evaluated the impact of methicillin resistance on the overall incidence of S. aureus infections. Yet, there are direct clinical and research implications of determining whether methicillin-susceptible S. aureus (MSSA) infection rates remain stable in the face of increasing MRSA prevalence or whether MSSA will be replaced over time. A synthesis of prior studies indicates that the emergence of healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA) has led to an increase in the overall incidence of S. aureus infections, with MRSA principally adding to, rather than replacing, MSSA. However, colonization with CA-MRSA may at least partially replace colonization with MSSA. So far, evidence indicates that MSSA still accounts for many infections. Therefore, eradication of MRSA alone is not sufficient to address the public health burden of S. aureus.

Carriage of healthcare-associated methicillin-resistant Stapyloccous aureus and empiric treatment for skin and soft tissue infections

Previous skin carriage of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) leads frequently to empiric MRSA coverage for the antibiotic treatment of skin and soft tissue infections.

Is Universal Screening of Children for Nasal Methicillin-Resistant Staphylococcus aureus Colonization Necessary on Hospital Admission?

Methicillin-resistant Staphylococcus aureus (MRSA) infections have increased significantly over the last decade. Increased prevalence and concern for nosocomial spread has led many states to mandate screening for nasal MRSA carriage. In December 2007, our institution implemented universal surveillance of all admitted patients. Nasal MRSA colonization rates and the role of universal surveillance in prevention and control of MRSA transmission in pediatric wards is not well characterized. The objectives of our study were to determine the incidence of nasal MRSA colonization, the concordance between nasal MRSA colonization and culture-proven MRSA disease at admission, and the impact of universal surveillance on MRSA transmission among children admitted to our pediatric ward. Loyola University Medical Center is an academic center with a pediatric hospital within the larger hospital. Of the 123 pediatric beds, 34 are ward beds. All children admitted from December 1, 2007, through June 30, 2010, were screened for nasal MRSA colonization, using the Cepheid GeneXpert system (Cepheid), and they were identified through the Epic electronic medical record system (Epic Systems). Contact isolation precautions were instituted if a polymerase chain reaction test or a clinical culture was positive. Microbiology laboratory data were used to identify patients with a positive nasal screen or MRSA cultures. Data on hospitalization within the previous 12 months, presence of an indwelling device, and site of the positive MRSA culture were collected. Recent antibiotic use and family history of MRSA disease were not analyzed because these data could not be reliably ascertained from charts. Antimicrobial susceptibilities of MRSA clinical isolates against oxacillin, gentamicin, cefazolin, rifampin, tetracycline, clindamycin, erythromycin, trimethoprim-sulfamethoxazole, and vancomycin were recorded. Isolates were considered to be community-associated MRSA (CA-MRSA) if they were resistant only to b-lactams erythromycin. Resistance to other antibiotics tested was considered to indicate healthcareassociated MRSA (HA-MRSA). Infection control data were reviewed to determine nosocomial MRSA cases in the pediatric ward. Four thousand and eighty-four patients were admitted to the pediatric ward, and 3,934 were screened for nasal MRSA colonization during the study. Of these, 234 patients (5.7%) were colonized, and 99 had culture-proven MRSA disease (2.4%). MRSA nasal colonization and disease rates were uniform throughout the study period. MRSA colonization and disease were highest among young children; 8.4% of infants less than 1 year old were colonized versus 5.2% of children 1 or more years old ( ). MRSA disease was more P p .004 prevalent in children 5 years old and under, 3.6% versus 1% in those more than 5 years old ( ). The incidence of P ! .002 nasal colonization markedly decreased in older age groups (Table 1). Most pediatric patients with MRSA colonization or disease had no identifiable risk factors; 9% had an indwelling catheter, and 39% were hospitalized in the year before. Most positive MRSA cultures (89%) were from skin and soft tissue sites, and 84% were CA-MRSA. Bacteremia was noted in 5 patients, 3 of whom had concurrent osteomyelitis. Only 54% of patients admitted with MRSA disease had a positive nasal screen. The use of MRSA nasal colonization to predict MRSA disease on admission had a sensitivity of 54% and a specificity of 96%. The positive predictive value was 24%, and the negative predictive value was 99%. Nosocomial MRSA infections were infrequent in our pediatric ward. There were 2 cases in the 2 years before universal surveillance and 1 during universal surveillance. The overall cost of universal screening of pediatric ward patients for the institute for the study period was $204,200, at $50 per test. Nasal MRSA colonization rates vary by geographic area and have increased over the last decade from less than 1% to 10%. Nasal MRSA colonization rate in admitted children was 5.7%, which is similar to the rate in our adult population (∼7%). The majority of colonized or infected children had no risk factors for HA-MRSA (!60%). Skin and soft tissue infections, mainly due to CA-MRSA, comprised the bulk of MRSA disease. Concerns for nosocomial spread of CA-MRSA have led many states to mandate screening of hospitalized patients and to observe contact precautions of identified carriers. While absence of MRSA nasal colonization is highly predictive of absence of disease, we found poor concordance between

Infection Prevention Practices in Adult ICUs in a Large Community Hospital System Experiencing Sustained Reduction in Healthcare-Associated (HA) MRSA Infections

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of HA and community-associated infections. HCA implemented an enterprise wide campaign to reduce HA-MRSA in 2007 consisting of active MRSA surveillance, barrier precautions, hand hygiene and disinfection. Mean HA-MRSA rates decreased for central line associated bloodstream infections (CLABSI), ventilator associated pneumonia (VAP) and surgical site infections (SSI) in 2008 and again in 2009 compared to 2006 baseline. MRSA colonization in adult ICUs was 8.9%.

Preferential Emergence of Reduced Vancomycin Susceptibility in Health Care-Associated Methicillin-Resistant Staphylococcus aureus Isolates during Continuous-Infusion Vancomycin Therapy in an In Vitro Dynamic Model

Bacterial killing and the development of reduced vancomycin susceptibility during continuous-infusion vancomycin (CIV) therapy were dependent on the area under the concentration-time curve over 24 h divided by the MIC (ƒAUC(24)/MIC), with values of ≥ 240 (equivalent total serum AUC(24)/MICs of ≥ 480) being bactericidal and suppressing emerging resistance in methicillin-resistant Staphylococcus aureus (MRSA). Also, vancomycin therapy was less likely to be bactericidal and 4.4 times more likely to lead to reduced vancomycin susceptibility in health care-associated MRSA than in community-associated MRSA.

Veterans Affairs Initiative to Prevent Methicillin-ResistantStaphylococcus aureusInfections

Health care-associated infections with methicillin-resistant Staphylococcus aureus (MRSA) have been an increasing concern in Veterans Affairs (VA) hospitals. A "MRSA bundle" was implemented in 2007 in acute care VA hospitals nationwide in an effort to decrease health care-associated infections with MRSA. The bundle consisted of universal nasal surveillance for MRSA, contact precautions for patients colonized or infected with MRSA, hand hygiene, and a change in the institutional culture whereby infection control would become the responsibility of everyone who had contact with patients. Each month, personnel at each facility entered into a central database aggregate data on adherence to surveillance practice, the prevalence of MRSA colonization or infection, and health care-associated transmissions of and infections with MRSA. We assessed the effect of the MRSA bundle on health care-associated MRSA infections. From October 2007, when the bundle was fully implemented, through June 2010, there were 1,934,598 admissions to or transfers or discharges from intensive care units (ICUs) and non-ICUs (ICUs, 365,139; non-ICUs, 1,569,459) and 8,318,675 patient-days (ICUs, 1,312,840; and non-ICUs, 7,005,835). During this period, the percentage of patients who were screened at admission increased from 82% to 96%, and the percentage who were screened at transfer or discharge increased from 72% to 93%. The mean (±SD) prevalence of MRSA colonization or infection at the time of hospital admission was 13.6±3.7%. The rates of health care-associated MRSA infections in ICUs had not changed in the 2 years before October 2007 (P=0.50 for trend) but declined with implementation of the bundle, from 1.64 infections per 1000 patient-days in October 2007 to 0.62 per 1000 patient-days in June 2010, a decrease of 62% (P<0.001 for trend). During this same period, the rates of health care-associated MRSA infections in non-ICUs fell from 0.47 per 1000 patient-days to 0.26 per 1000 patient-days, a decrease of 45% (P<0.001 for trend). A program of universal surveillance, contact precautions, hand hygiene, and institutional culture change was associated with a decrease in health care-associated transmissions of and infections with MRSA in a large health care system.

Pre-emptive contact precautions for intubated patients reduced healthcare-associated meticillin-resistant Staphylococcus aureus transmission and infection in an intensive care unit

Healthcare-associated infection by meticillin-resistant Staphylococcus aureus (MRSA) is still a great concern in an intensive care unit (ICU). Our surveillance data in the ICU revealed that intubated patients were at eight times higher risk of acquiring MRSA than non-intubated patients, so we hypothesised that pre-emptive contact precautions for all intubated patients would prevent healthcare-associated infection by MRSA in the ICU. Patients staying in our ICU for >2 days were included in this study. The study period was divided into two periods. During 2004 (1st period), contact precautions were performed only for patients with MRSA. During 2005–2007 (2nd period), contact precautions were applied to all intubated patients regardless of MRSA infection status. Patients were defined as MRSA-positive on admission when MRSA was detected by surveillance or clinical culture on enrolment. Other MRSA-positive results were defined as healthcare-associated MRSA (HA-MRSA) transmission. HA-MRSA infection was diagnosed according to the National Nosocomial Infections Surveillance Manual. The 1st period comprised 415 patients, and the 2nd period comprised 1280 patients. In intubated patients, HA-MRSA infection rate decreased significantly in the 2nd period (1st period 12.2%, 2nd period 5.6%; P = 0.015). HA-MRSA infection of all patients decreased from 3.6 to 2.3 incidents per 1000 patient-days (P < 0.05), despite a significant increase in the rate of patients MRSA positive on admission in the 2nd period (1st period 2.9%; 2nd period 6.1%). Pre-emptive contact precautions for intubated patients would be helpful in reducing HA-MRSA infection in ICU.

Glycopeptide and daptomycin resistance in community-associated MRSA in the UK

Methicillin-resistant Staphylococcus aureus (MRSA) infections are commonly treated with glycopeptides. When glycopeptide resistance occurs, one of the few remaining therapeutic options is daptomycin. We describe the in vivo development of both glycopeptide and daptomycin resistance in a patient from the UK with community-associated (CA) MRSA infective endocarditis. A 35-year-old man presented to our hospital in Liverpool, UK, in 2008. A diagnosis of tricuspid valve infective endocarditis was made, secondary to intravenous drug use. Both MRSA and group G haemolytic streptococcus grew from the blood cultures. Antimicrobial therapy was initiated with teicoplanin and rifampicin, but after 3 weeks of treatment MRSA was cultured again from the patient’s blood, suggesting that resistance may have developed. Glycopeptide minimum inhibitory concentration (MIC) testing was therefore performed. The MIC to teicoplanin was determined to be 8 mg/L, identifying the MRSA isolate as glycopeptide-resistant S. aureus (GRSA). Daptomycin therapy was prescribed, but 1 week later, after an initial clinical improvement, the patient suffered cerebral emboli. Blood cultures again recovered MRSA, leading to daptomycin MIC testing. Daptomycin resistance was confirmed with an MIC to daptomycin of 4 mg/L. Linezolid, ciprofloxacin and gentamicin were then administered to the patient (Fig. 1). The patient clinically responded to this treatment, and mitral valve replacement was subsequently completed. A total of 6 weeks of oral ciprofloxacin and linezolid were prescribed post-operatively, and the patient was well upon review in January 2010. This patient was initially infected with a glycopeptidesusceptible MRSA, with initial teicoplanin and vancomycin MICs of B2 mg/L [MICs by Etest method (bioMerieux, Marcy l’Etoile, France)]. However, following treatment with teicoplanin, the isolate became glycopeptide resistant, with teicoplanin and vancomycin MICs of 8 and 3 mg/L, respectively. The MIC breakpoint for glycopeptide resistance is[2 mg/L according to the European Committee on Antimicrobial Susceptibility testing (EUCAST 2010: http://www.eucast.org). The development of glycopeptide resistance was associated with that of daptomycin resistance. The daptomycin MIC increased from a range of 0.19–0.25 to 1.5–3 mg/L, and this occurred prior to in vivo exposure to daptomycin (EUCAST MIC breakpoint for daptomycin resistance is [1 mg/L). Daptomycin therapy was associated with a further rise in the daptomycin MIC to 4 mg/L (Table 1). The MRSA isolate was confirmed as CA-MRSA [1] based on its susceptibility to ciprofloxacin [2], positivity for the Panton–Valentine Leukocidin (PVL) gene [3] and spa type t127 [4]. SCCmec typing, which is also used to differentiate CA-MRSA and health care-associated MRSA (HA-MRSA) is not valid in the UK as HA-MRSA and CA-MRSA are both commonly SCCmec type IV [5]. Pulsed field gel electrophoresis (PFGE) confirmed the A. Kirby (&) C. M. Broughton Institute of Infection and Global Health, Department of Clinical Infection, Microbiology and Immunology, University of Liverpool, 8th Floor Duncan Building, Daulby Street, Liverpool L69 3GA, UK e-mail: amk@liv.ac.uk

Survival and transmission of community-associated methicillin-resistant Staphylococcus aureus from fomites

Transmission of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) from fomites appears to play an important role in CA-MRSA outbreaks. However, the amount and duration of transmissibility of MRSA have not been quantified. We assessed the survival and transmission of the CA-MRSA strain USA300-0114 from 9 fomites (razors, plastic toys, ceramic, soap, wood, vinyl, towels, bed sheets, and shoulder pads). Fomites were inoculated then briefly pressed onto sterile pigskin at 5 minutes; days 1, 2, 3, 7, and 10; and then weekly for 10 weeks. The experiment was repeated using 2 methicillin-susceptible S aureus (MSSA) and 3 health care-associated (HA) MRSA strains on select fomites. Bacteria could be transmitted to skin from all fomites except soap. Transmissibility decreased over time but more rapidly from porous (eg, towels) than nonporous (eg, vinyl) fomites (P = .0002), with some fomites showing transmissibility for more than 8 weeks after contamination. The CA-MRSA strain was transmissible longer than the HA-MRSA strains (P < .0001) and 1 MSSA strain. CA-MRSA strains are transmissible from many fomites to skin with contaminated nonporous fomites exhibiting transmissibility many weeks after contamination. Transmissibility of HA-MRSA strains demonstrated attenuated transmissibility compared with CA-MRSA strains. Findings may have implications for CA-MRSA infection prevention.

Rates of hospital-acquired and healthcare-associated MRSA declined in the USA between 2005 and 2008

Commentary on: AJ Kallen, Y Mu, S Bulens, et al..; Active Bacterial Core surveillance (ABCs) MRSA Investigators of the Emerging Infections Program. Health care-associated invasive MRSA infections, 2005–2008. JAMA2010;304:641–8.