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Severe infections due to Staphylococcus aureus require prolonged therapy for cure, and relapse may occur even years after the first episode. Persistence of S. aureus may be explained, in part, by nasal carriage of S. aureus, which occurs in a large percentage of healthy humans and represents a major source of systemic infection. However, the persistence of internalized S. aureus within mucosal cells has not been evaluated in humans. Here, we provide the first in vivo evidence of intracellular reservoirs of S. aureus in humans, which were assessed in endonasal mucosa specimens from patients suffering from recurrent S. aureus rhinosinusitis due to unique, patient-specific bacterial clonotypes. Heavily infected foci of intracellular bacteria located in nasal epithelium, glandular, and myofibroblastic cells were revealed by inverted confocal laser scan fluorescence and electron microscopic examination of posttherapy intranasal biopsy specimens from symptom-free patients undergoing surgery on the sinuses. Intracellular residence may provide a sanctuary for pathogenic bacteria by protecting them from host defense mechanisms and antibiotic treatment during acute, recurrent S. aureus rhinosinusitis.

International audience; The increased incidence over the past decade of bloodstream infections (BSIs) caused by gram-positive bacteria, particularly methicillin-resistant Staphylococcus aureus, highlights the critical need for a consistent approach to therapy. However, there is currently no international consensus on the diagnosis and management of gram-positive BSIs. The Clinical Consensus Conference on Gram-Positive Bloodstream Infections was convened as a session at the 9th International Symposium on Modern Concepts in Endocarditis and Cardiovascular Infections held in 2007. Participants discussed various aspects of the practical treatment of patients who present with gram-positive BSI, including therapeutic options for patients with BSIs of undefined origin, the selection of appropriate empirical therapy, and treatment of complicated and uncomplicated BSIs. The opinions of participants about these key issues are reflected in this article.

Introduction: rapid diagnostic tests may allow early identification of previously unknown methicillin-resistant Staphylococcus aureus (MRSA) carriers at intensive care unit (ICU) admission. The aim of this study was twofold: first, to assess whether a new molecular MRSA screening test can substantially decrease the time between ICU admission and identification of MRSA carriers; and, second, to examine the combined effect of rapid testing and pre-emptive contact isolation on MRSA infections. Method: since November 2003, patients admitted for longer than 24 hours to two adult ICUs were screened systematically on admission using quick, multiplex immunocapture-coupled PCR (qMRSA). Median time intervals from admission to notification of test results were calculated for a five-month intervention phase (November 2003-March 2004) and compared with a historical control period (April 2003-October 2003) by nonparametric tests. ICU-acquired MRSA infection rates were determined for an extended surveillance period (January 2003 through August 2005) and analyzed by Poisson regression methods. Results: during the intervention phase, 97% (450/462) of patients admitted to the surgical ICU and 80% (470/591) of patients admitted to the medical ICU were screened. On-admission screening identified the prevalence of MRSA to be 6.7% (71/1053). Without admission screening, 55 previously unknown MRSA carriers would have been missed in both ICUs. Median time from ICU admission to notification of test results decreased from 87 to 21 hours in the surgical ICU (P < 0.001) and from 106 to 23 hours in the medical ICU (P < 0.001). In the surgical ICU, 1,227 pre-emptive isolation days for 245 MRSA-negative patients were saved by using the qMRSA test. After adjusting for colonization pressure, the systematic on-admission screening and pre-emptive isolation policy was associated with a reduction in medical ICU acquired MRSA infections (relative risk 0.3, 95% confidence interval 0.1-0.7) but had no effect in the surgical ICU (relative risk 1.0, 95% confidence interval 0.6-1.7). Conclusion: the qMRSA test decreased median time to notification from four days to one day and helped to identify previously unknown MRSA carriers rapidly. A strategy linking the rapid screening test to pre-emptive isolation and cohorting of MRSA patients substantially reduced MRSA cross-infections in the medical but not in the surgical ICU.

OBJECTIVE: To assess the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in Switzerland. MATERIAL AND METHODS: One-year national survey of all MRSA cases detected in a large sample of Swiss healthcare institutions (HCI). Analysis of epidemiological and molecular typing data (PFGE) of MRSA strains. RESULTS: During 1997, 385 cases of MRSA were recorded in the 5 university hospitals, in 33 acute care community hospitals, and 14 rehabilitation or long-term care institutions. Half of the cases were found at the University of Geneva Hospitals where MRSA was already known to be endemic (41.1 cases/10,000 admissions). The remaining cases (200) were distributed throughout Switzerland. The highest rates (>100 cases/10,000 admissions) were reported from non-acute care institutions. Rates ranged from 3.3 to 41.1 cases/10,000 admissions for university hospitals (mean 15.5); 0.67 to 90.4 for community hospitals (mean 4.8), and 28.2 to 315 for non-acute care institutions reporting MRSA (mean 85.7). Forty percent of MRSA patients were infected, while 60% were only colonised. The leading infection sites were skin and soft tissue (21%), surgical site (15%), and the urinary tract (26%). Whereas in Eastern Swiss HCI most MRSA cases occurred in acute care hospitals (n = 47, 98%), rehabilitation and long-term care institutions accounted for an important number of the identified cases (n = 107, 38%) in Western Switzerland. CONCLUSION: Low rates of MRSA were still observed in Swiss HCI, despite one outlying acute care centre with endemic MRSA and some nonacute care institutions with epidemic MRSA. Rehabilitation and long-term care institutions contributed to a substantial proportion of cases in Western Switzerland and may constitute a significant reservoir. Overall, a national approach to surveillance and control of MRSA is mandatory in order to preserve a still favourable situation, and to decrease the risk of epidemic MRSA dissemination.

Objective:To investigate an outbreak ofStaphylococcus aureussurgical-site infections.Design:Case–control study.Setting:Pediatric cardiothoracic surgery service of a tertiary-care university medical center.Method:Molecular typing was used to identify healthcare workers who carried the epidemic strain.Results:Three children acquired surgical-site infections caused by a single strain ofS. aureus. Fourteen (25%) of the staff members in the operating room and 17 (11%) on nursing units carried the epidemic strain (P= 01). A case–control study identified 4 healthcare workers who were associated statistically with the outbreak, 2 of whom (a cardiothoracic surgeon and a perfusionist) carried the epidemic strain in their nares. The surgeon also carried the epidemic strain on his hands. Each staff member who carried the epidemic strain was treated with mupirocin; those carrying the strain on their hands were required to wash their hands with chlorhexidine. The surgeon was not allowed to perform surgery until 2 of his hand cultures did not growS. aureus.Conclusions:Only three children were infected with the epidemic strain, but it was disseminated widely among staff who cared for children who underwent cardiothoracic surgery. No additional cases were identified after staff members who carried the epidemic strain were decolonized. Both classic epidemiologic methods and molecular typing techniques were necessary to identify the source and extent of this outbreak.

AIM: The prevalence of intracellular Staphylococcus aureus organisms in the nasal mucosa of patients with recurrent infectious rhinosinusitis episodes was studied. METHOD: Twenty-seven consecutive adult patients who failed medical management of chronic rhinosinusitis (CRS) of multiple origins, associated or not with nasal polyposis, were consecutively enrolled for endonasal sinus surgery (including partial middle turbinectomy, middle antrostomy, ethmoidectomy, sphenoidotomy) and followed for a 12-month post-operative period. RESULTS: Seventeen of these patients showed the presence of intracellular S. aureus as detected by confocal laser scan immunofluorescence microscopy in epithelial cells of surgical intranasal biopsy specimens. Nine of the patients with and two without intracellular bacteria yielded S. aureus in endoscopically guided cultures of middle meatus secretions, despite the recent administration of prophylactic antibiotics. Eleven of the 17 patients with intracellular S. aureus relapsed for rhinosinusitis within the 12-month follow-up period. Molecular typing of sequential S. aureus isolates demonstrated the persistence of unique patient-specific S. aureus clonotypes in nine of the patients with intracellular bacteria during the 12-month follow-up. CONCLUSION: The presence of intracellular S. aureus in epithelial cells of the nasal mucosa is a significant risk factor for recurrent episodes of rhinosinusitis due to persistent bacterial clonotypes, which appear refractory to antimicrobial and surgical therapy.