Prevalence of methicillin-resistant and methicillin-susceptible Staphylococcus aureus in the community

Recent reports indicate that community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections are increasing and may now involve persons without risk factors predisposing for acquisition. To estimate the extent of community MRSA in New York City, the prevalence of S. aureus and MRSA nasal colonization in a well-patient population of 500 children and guardians was determined. The prevalence of S. aureus nasal carriage was 35% for children and 28% for guardians. One person with predisposing risk factors was colonized with an MRSA, which was identified as the predominant clone found in New York City hospitals. A high degree of methicillin-susceptible S. aureus strain diversity was noted, with no apparent selection for specific clonal types. Thus, MRSA colonization is not ubiquitous in persons without predisposing risk outside of the health care environment. Bacterial competition and a lack of strong selection may limit the community spread of MRSA and can account for its sporadic distribution.     

Investigation of colonization with methicillin-resistant and methicillin-susceptible Staphylococcus aureus in an outpatient population in Turkey

Methicillin-resistant Staphylococcus aureus (MRSA), known as a nosocomial pathogen, has been isolated from community-acquired infections since the 1980s. It has been reported that there are carriers of MRSA in the community although the rate of carriers is low and the most important risk factor of community-acquired carriage is hospitalization or referral to healthcare facilities. We attempted to investigate methicillin-resistant and methicillin-susceptible S. aureus colonization, respectively, in nasal and axillary swabs obtained from 500 patients without a history of hospitalization who were admitted to outpatient clinics and from 102 healthcare workers chosen as a control group. Of the patients, 9.4% had nasal S. aureus colonization without methicillin-resistant strains. Of the health care workers, 8.8% had S. aureus colonization without methicillin-resistant strains and only one worker had MRSA. The nasal carriage ratio of S. aureus in children was found to be 19.1% (22 of 115), and that in adults was 6.5% (25 of 385). The difference between the two age groups was determined as statistically significant (P = 0.006).     

Outcome and attributable mortality in critically Ill patients with bacteremia involving methicillin-susceptible and methicillin-resistant Staphylococcus aureus

BACKGROUND: Staphylococcus aureus bacteremia carries high mortality rates. The clinical impact of methicillin resistance remains controversial: outcome comparisons between patients with bacteremia involving methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) S aureus are difficult to perform because of important differences in severity of illness. METHODS: A retrospective cohort analysis and 2 independent case-control analyses were performed to determine and compare outcomes and attributable mortality rates of MSSA (n = 38) and MRSA bacteremia (n = 47) in critically ill patients. For the case-control studies, matching (1:2 ratio) was based on the APACHE (Acute Physiology and Chronic Health Evaluation) II classification: APACHE II score (+/-1 point) and diagnostic category. RESULTS: Patients with MRSA bacteremia had more acute renal failure and hemodynamic instability than patients with MSSA bacteremia. They had a longer intensive care unit stay and ventilator dependency. Patients with MRSA bacteremia had a higher 30-day mortality rate (53.2% vs 18.4%) and in-hospital mortality rate (63.8% vs 23.7%) (P<.05). Multivariate survival analysis demonstrated acute renal failure, length of mechanical ventilation, age, and methicillin resistance to be independently associated with mortality (P<.05). The attributable mortality rate for MSSA bacteremia was 1.3%: mortality rates for cases and controls were respectively 23.7% and 22.4% (P =.94). The attributable mortality rate for MRSA bacteremia was 23.4%: mortality rates for cases and controls were respectively 63.8% and 40.4% (P =.02). The difference (22.1%) between both attributable mortality rates was significant (95% confidence interval, 8.8%-35.3%). CONCLUSION: In critically ill patients, after accurate adjustment for disease severity and acute illness, we found MRSA bacteremia to have a higher attributable mortality than MSSA bacteremia.     

Poststernotomy mediastinitis due to Staphylococcus aureus: comparison of methicillin-resistant and methicillin-susceptible cases.

The objective of the study was to compare the outcome of poststernotomy mediastinitis (PSM) caused by methicillin-resistant and methicillin-susceptible Staphylococcus aureus (MRSA and MSSA, respectively). Hospital records of 41 patients with S. aureus PSM who were all treated by closed drainage from 1 April 1996 through 1 February 2000 were reviewed. PSM was caused by MRSA in 15 patients and by MSSA in 26. Follow-up (+/-SD) averaged 12.5+/-14.0 months per patient. Both groups had similar perioperative characteristics. Patients with MRSA PSM had a significantly lower actuarial survival rate than did patients with MSSA PSM (60.0%+/-12.6%, 52.5%+/-3.4%, and 26.3%+/-19.7% versus 84.6%+/-7.1%, 79.0%+/-8.6%, and 79.0%+/-8.65 at 1 month, and at 1 and 3 years, respectively; values are +/- SD; P=.04). PSM-related death and treatment failure were significantly higher in the MRSA group than in the MSSA group (P=.03 and.02, respectively). Logistic regression analysis revealed that MRSA was the only independent risk factor for overall mortality. In conclusion, the clinical outcome of PSM caused by MRSA is poorer than that caused by MSSA.     

社区获得性耐甲氧西林金黄色葡萄球菌

社区获得性耐甲氧西林金黄色葡萄球菌是社区感染中重要的致病菌之一,以往由其所致感染多发生在医院环境,如今其引起的社区感染的比例不断上升.自1961年发现第1株耐甲氧西林金黄色葡萄球菌以来,耐甲氧西林金黄色葡萄球菌在世界各地流行并引起暴发流行,耐药程度不断加重.尤其1996年万古霉素不敏感金黄色葡萄球菌及2002年耐万古霉素金黄色葡萄球菌的出现,显示其对人类的威胁愈趋严重,已成为当今感染医学一个难题.本文介绍社区获得性耐甲氧西林金黄色葡萄球菌的流行情况及防治措施.     

Comparison of both clinical features and mortality risk associated with bacteremia due to community-acquired methicillin-resistant Staphylococcus aureus and methicillin-susceptible S. aureus.

BACKGROUND: The majority of research about community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection has focused on skin and soft-tissue infections. No literature has been published on the clinical features and outcomes of adult patients with CA-MRSA bacteremia in comparison with patients with community-acquired methicillin-susceptible S. aureus (CA-MSSA) bacteremia. METHODS: From 1 January 2001 through 31 December 2006, the demographic data and outcome of 215 consecutive adult patients admitted to a tertiary care center in Taiwan with S. aureus bacteremia (age, >16 years) who fulfilled the criteria for community-acquired S. aureus bacteremia were collected for analysis. RESULTS: The mean age (+/-SD) was 56.8+/-20.5 years. There were 30 patients (14%) with CA-MRSA bacteremia and 185 (86%) patients with CA-MSSA bacteremia. Cutaneous abscess (odds ratio, 5.46; 95% confidence interval, 1.66-17.94) and necrotizing pneumonia (odds ratio, 24.81; 95% confidence interval, 2.63-234.03) were the independent predictors of CA-MRSA bacteremia; endovascular infection was the only independent predictor of CA-MSSA bacteremia. After Cox regression analysis, the independent significant risk factors for 30-day mortality included increased age, shock, and thrombocytopenia (<100,000 cells/microL). After adjustment, the day 30 mortality of patients with CA-MRSA bacteremia was not significantly higher than that of patients with CA-MSSA bacteremia (adjusted hazard ratio, 1.01; 95% confidence interval, 0.30-3.39; P = .986). Most (92%) of 25 available CA-MRSA isolates were multilocus sequence typing 59. CONCLUSIONS: The number of adult patients with CA-MRSA bacteremia increased with time, and the disease was associated with more necrotizing pneumonia and cutaneous abscess but less endovascular infection than was CA-MSSA bacteremia. Patients with CA-MRSA bacteremia did not have higher mortality than did patients with CA-MSSA, even though most of the patients with CA-MRSA bacteremia did not receive empirical glycopeptide therapy.     

Control of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of nosocomial infections worldwide. Different approaches to the control of this pathogen have met with varying degrees of success in different health care settings. Controversies exist with regards to various MRSA control strategies. The implementation and outcomes of control measures depend on several factors, including scientific, economic, administrative, governmental, and political influences. It is clear that flexibility to adapt and institute these measures in the context of local epidemiology and resources is required.     

Community-acquired methicillin-resistant Staphylococcus aureus pneumonia

Community-acquired methicillin-resistant Staphylococcus aureus is increasingly recognized as an important pathogen causing skin and soft tissue infections. We report a case of severe necrotizing pneumonia caused by community-acquired methicillin-resistant S. aureus in a peripartum woman. This case illustrates that community-acquired methicillin-resistant S. aureus must be considered as a potential pathogen in severe community-acquired pneumonia.     

Bacteremic pneumonia due to Staphylococcus aureus: A comparison of disease caused by methicillin-resistant and methicillin-susceptible organisms.

We performed a prospective study of all patients with bacteremic pneumonia due to Staphylococcus aureus over a period of 6 years during an outbreak of methicillin-resistant S. aureus (MRSA). Patients with bacteremic pneumonia due to MRSA (32 cases) or methicillin-susceptible S. aureus (MSSA; 54 cases) were compared. The patients with MRSA pneumonia were older and were more likely than those with MSSA pneumonia to have predisposing factors for acquisition of the infection. There were no differences in clinical findings, radiological pattern, or complications in clinical evolution among patients with MRSA and MSSA pneumonia. Mortality was significantly higher among MSSA-infected patients treated with vancomycin than among those treated with cloxacillin (47% vs. none; P<.01). Multivariate analysis (stepwise logistic regression method) showed a relationship between mortality and the following variables: septic shock (odds ratio [OR], 61), vancomycin treatment (OR, 14), and respiratory distress (OR, 8).     

In vitro activity of fosfomycin against methicillin-susceptible and methicillin-resistant staphylococcus aureus

Summary Thein vitro antibacterial activity of fosfomycin was compared to that of oxacillin, cefazolin, ceftriaxone and vancomycin against isolates ofStaphylococcus aureus from patients treated at the University of Vienna General Hospital. Of 211 strains, 104 were methicillin-susceptible and 107 were methicillin-resistant. Fosfomycin inhibited over 90% of the strains at concentrations of 64 mg/l, independent of methicillin susceptibility or resistance. The minimal bactericidal concentrations (MBC) were one dilution above the minimal inhibitory concentrations (MIC). Vancomycin showed activity similar to fosfomycin while other -lactam antibiotics such as oxacillin, cefazolin and ceftriaxone were inactive against methicillin-resistantS. aureus. Fosfomycin at a high dosage seems to be a potential drug for the treatment of infections due to methicillin-resistantS. aureus.

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In vitro-Aktivität von Fosfomycin gegen Methicillin-empfindliche und Methicillin-resistente Stämme von Staphylococcus aureus

Zusammenfassung Die antibakterielle Aktivität von Fosfomycin gegenStaphylococcus aureus wurde mit der von Oxacillin, Cefazolin, Ceftriaxon und Vancomycin verglichen. Von 211 klinischen Isolaten aus dem Bereiche der Universitätskliniken in Wien waren 107 Methicillin-resistent. Mehr als 90 Prozent der untersuchten Stämme wurden durch 64 mg/l Fosfomycin gehemmt, unabhängig davon, ob die Stämme Methicillin-empfindlich oder -resistent waren. Die minimalen bakteriziden Konzentrationen (MBK) waren eine Verdünnungsstufe höher als die minimalen Hemmkonzentrationen (MHK). Vancomycin zeigte ein ähnliches Verhalten wie Fosfomycin bei Methicillin-resistenten Stämmen vonS. aureus, während Oxacillin, Cefazolin und Ceftriaxon keinerlei Aktivität zeigten. Fosfomycin stellt in hoher Dosierung ein potentielles Therapeutikum bei Infektionen mit Methicillin-resistentenS. aureus-Stämmen dar.

     

Methicillin-resistant and methicillin-susceptible community-acquired Staphylococcus aureus infection among children

Methicillin-resistant Staphylococcus aureus has emerged as a pathogen associated with community-acquired infections worldwide. We report the spectrum of community-acquired S. aureus infections and compare the patients infected with methicillin-susceptible or methicillin-resistant strains among patients aged <20 years. Overall, 90 cases of community-acquired S. aureus were detected in an 11-year period. Clinical and microbiological data were registered. Fifty-nine (66%) patients were male and the median age was two years. The majority (87%) of the patients were hospitalized and chronic underlying illnesses were detected in 27 (30%) cases. Overall, 34 (37.8%) patients had skin/soft tissue infections and 56 (62.2%) patients had deep-seated infection. Four (5.1%) patients were transferred to the intensive care unit and two (2.6%) died. Complications were detected in 17 (18.9%) cases, such as pleural effusion (41.2%), osteomyelitis (23.5%), and sepsis (17.6%). Six (6.7%) methicillin-resistant strains were detected. Patients infected with methicillin-susceptible or methicillin-resistant strains had similar baseline characteristics and treatment outcomes. Approximately 93% of the cases received systemic antibiotics, out of which 59 (65.5%) used oxacillin or cefalotin. Both methicillin-susceptible and methicillin-resistant S. aureus strains resulted in morbidity and death among children in this setting where methicillin-resistant strains are infrequent.     

Rapid development of ciprofloxacin resistance in methicillin-susceptible and -resistant Staphylococcus aureus

The fluoroquinolones, particularly ciprofloxacin, have been suggested to treat methicillin-resistant Staphylococcus aureus (MRSA) infections and colonization and methicillin-susceptible S. aureus (MSSA) infections. The development of ciprofloxacin resistance in MRSA and MSSA was prospectively evaluated. After 3 months of ciprofloxacin use, high-level resistance (MIC90, 64 micrograms/ml) developed in MRSA and increased at an alarming rate, from none to 79% over a 1-year period. High-level ciprofloxacin resistance also developed in MSSA, increasing to 13.6% over the same period. Antibiograms, phage typing, and plasmid profile analysis suggest that more than one clone of MRSA developed resistance and that ciprofloxacin resistance is not associated with the acquisition of a new plasmid. Most patients had nosocomial acquisition and about one-half had a history of previous ciprofloxacin use. Ciprofloxacin resistance can develop rapidly in S. aureus; thus, ciprofloxacin appears to have limited usefulness in treating staphylococcal infections and colonization, especially those due to MRSA.