S. Aureus Bacteremia Research Articles

High rate of decreasing daptomycin susceptibility during the treatment of persistent Staphylococcus aureus bacteremia

Daptomycin is bactericidal against Staphylococcus aureus, with susceptibility defined as a minimal inhibitory concentration (MIC) < or =1 microg/ml. Higher MIC developed in a few cases during therapy. The frequency of MIC rise in persistent bacteremia is unknown. We evaluated all patients with S. aureus bacteremia (SAB) treated with daptomycin (> or =2 days) from 1 April 2004 to 30 October 2006. All patients with post-daptomycin-exposure saved isolates were studied. Daptomycin susceptibility was determined (in duplicate) on all pre- and post-daptomycin-exposure isolates by the broth (Mueller-Hinton) microdilution method. Among 74 treatment courses in 67 patients, 18 were for SAB. Ten had persistent bacteremia (median = 11 days; range = 1-21) and post-daptomycin-exposure saved isolates. The patient age was 29-84 years (median = 57.5 years). Intravascular catheter was the most common source (50%). Most patients (90%) failed therapy prior to starting daptomycin. The initial daptomycin dose was 4 mg/kg in four (40%) cases. The pre-exposure MIC was 0.125-0.5 microg/ml. The post-exposure MIC increased in four cases and was elevated in two cases (60%), to 2 microg/ml in five and 4 microg/ml in one. MIC rise was noted within 5-15 days of exposure and persisted up to 247 days after stopping daptomycin. Pulse-field gel electrophoresis (PFGE) band pattern of isolates with increased MIC revealed 1-3-band differences, implying genetic relatedness. All patients with non-susceptible isolates relapsed or failed therapy. These findings illustrate that daptomycin susceptibility often decreases during the treatment of persistent SAB. Therefore, susceptibility should be closely monitored during therapy.

Risk Factors for Infective Endocarditis and Outcome of Patients With Staphylococcus aureus Bacteremia

To investigate the risk factors for Staphylococcus aureus infective endocarditis (SAIE) and 6-month mortality in patients with S aureus bacteremia (SAB). This study consisted of patients who were diagnosed as having nosocomial or community-acquired SAB or SAIE between June 1, 2000, and December 31, 2005. Clinical characteristics of patients with SAB were compared with those of patients with SAIE, and predictors of mortality in patients with SAB were analyzed. The median age of the 132 randomly selected patients with SAB and the 66 patients with SAIE was 66 and 68 years, respectively. Univariable analysis showed that unknown origin of SAB, a valvular prosthesis, a pacemaker, persistent fever, and persistent bacteremia were significantly associated with SAIE. In multivariable analysis, unknown origin of SAB (odds ratio [OR], 4.2; 95% confidence interval [CI], 1.9-9.3; P=.001), a valvular prosthesis (OR, 9.2; 95% CI, 3.2-26.2; P<.001), persistent fever (OR, 3.1; 95% CI, 1.0-9.0; P=.04), and persistent bacteremia (OR, 6.8; 95% CI, 2.3-20.2- P=.001) were independently associated with SAIE. Six- month mortality was 8% in patients with SAB vs 35% in patients with SAIE (OR, 6.5; 95% CI, 2.9- 14.8; P<.001). In univariable analysis, methicillin- resistant S aureus (OR, 7.2; 95% CI, 1.7 - 29.4; P=.005) was significantly associated with 6-month mortality in patients with SAB. Unknown origin of SAB, a valvular prosthesis, persistent fever, and persistent bacteremia were independently associated with SAIE in patients with SAB. In univariable analysis, methicillin-resistant S aureus was associated with 6-month mortality in patients with SAB. S aureus infective endocarditis had a significantly higher mortality than SAB. The optimal management of SAB and SAIE deserves further study.

Changing Epidemiology of Pediatric Staphylococcus aureus Bacteremia in Denmark From 1971 Through 2000

Staphylococcus aureus is known to be a leading cause of bacteremia in childhood, and is associated with severe morbidity and increased mortality. To determine developments in incidence and mortality rates, as well as risk factors associated with outcome, we analyzed data from 1971 through 2000. Nationwide registration of S. aureus bacteremia (SAB) among children and adolescents from birth to 20 years of age was performed. Data on age, sex, source of bacteremia, comorbidity and outcome were extracted from discharge records. Rates were population adjusted and risk factors for death were assessed by multivariate logistic regression analysis. During the 30-year study period, 2648 cases of SAB were reported. Incidence increased from 4.6 to 8.4 cases per 100,000 population and case-mortality rates decreased from 19.6% to 2.5% (P = 0.0001). Incidence in the infant age group (<1 year) were 10- to 17-fold greater compared with that in the other age strata and mortality rate was twice as high. Hospital-acquired infections dominated the infant group, accounting for 73.9%-91.0% versus 39.2%-50.5% in the other age groups. By multivariate analysis, pulmonary infection and endocarditis for all age groups, comorbidity for the older than 1 year, and hospital-acquired infections for the oldest group were independently associated with an increased risk of death. Mortality rates associated with SAB decreased significantly in the past 3 decades, possibly because of new and improved treatment modalities. However, incidence rates have increased significantly in the same period, underscoring that S. aureus remains an important invasive pathogen.

Analysis of Methicillin Resistance among Staphylococcus aureus Blood Isolates in an Emergency Department

The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) has become of great concern in both hospital and community settings. To evaluate the prevalence and risk factors for methicillin resistance among Staphylococcus aureus, blood isolates in our Emergency Department (ED) were collected. All patients with S. aureus bacteremia (SAB) who presented to the ED from January 2000 to August 2005 were included, and a retrospective study was performed. A total of 231 patients with SAB were enrolled (median age, 59 yr; M:F, 125:106). Among these patients, methicillin-resistant strains accounted for 27.3% (63 patients). Catheter-related infection was the most frequent primary site of SAB (39.0%), followed by skin and soft tissue infection (16.5%). In multivariate analysis, recent surgery (OR, 3.41; 95% CI, 1.48-7.85), recent hospitalization (2.17; 1.06-4.62), and older age (≥61 yr) (2.39; 1.25-4.57) were independently associated with the acquisition of methicillin-resistant strains. When antimicrobial therapy is considered for the treatment of a patient with suspected SAB, clinicians should consider obtaining cultures and modifying empirical therapy to provide MRSA coverage for patients with risk factors: older age, recent hospitalization, and recent surgery.

Clinical and economic impact of methicillin resistance in patients with Staphylococcus aureus bacteremia

We performed a retrospective cohort study to determine the morbidity, mortality, and hospital costs attributable to methicillin resistance in patients with S. aureus bacteremia (SAB). Episodes of SAB occurring at the Detroit Receiving Hospital in 1999–2001 were evaluated. Controlling for confounding variables, patients with methicillin-resistant Staphylococcus aureus (MRSA) had a 1.5-fold longer length of stay (19.1 versus 14.2 days, P = 0.005) and a 2-fold increased cost of hospitalization ($21 577 versus $11 668, P = 0.001) compared with methicillin-susceptible S. aureus (MSSA). MRSA patients were at increased risk for delayed treatment, and delayed therapy was an independent predictor of mortality. Efforts should be made to ensure that appropriate therapy is initiated promptly in patients at risk for MRSA. Infection control policies must be strictly enforced to limit the spread of MRSA and potentially minimize excess hospital expenditures incurred with MRSA. With the advent of new treatment options, the impact of MRSA will need to be revisited to determine if these therapies can remedy the increased morbidity associated with MRSA.

Healthcare-AssociatedStaphylococcus aureusBacteremia and the Risk for Methicillin Resistance: Is the Centers for Disease Control and Prevention Definition for Community-Acquired Bacteremia Still Appropriate?

To evaluate a new classification for bloodstream infections that differentiates hospital acquired, healthcare associated, and community acquired in patients with blood cultures positive for Staphylococcus aureus. Prospective, observational study. Three tertiary-care, university-affiliated hospitals in Dublin, Ireland, and Strasbourg, France. Two hundred thirty consecutive patients older than 18 years with blood cultures positive for S. aureus. S. aureus bacteremia (SAB) was defined as hospital acquired if the first positive blood culture was performed more than 48 hours after admission. Other SABs were classified as healthcare associated or community acquired according to the definition proposed by Friedman et al. When available, strains of methicillin-resistant Staphylococcus aureus (MRSA) were analyzed by pulsed-field gel electrophoresis (PFGE). Eighty-two patients were considered as having community-acquired bacteremia according to the Centers for Disease Control and Prevention (CDC) classification. Of these 82 patients, 56% (46) had healthcare-associated SAB. MRSA prevalence was similar in patients with hospital-acquired and healthcare-associated SAB (41% vs 33%; P > .05), but significantly lower in the group with community-acquired SAB (11%; P < .03). PFGE of MRSA strains showed that most community-acquired and healthcare-associated MRSA strains were similar to hospital-acquired MRSA strains. On multivariate analysis, Friedman's classification was more effective than the CDC classification for predicting MRSA. These results support the call for a new classification for community-acquired bacteremia that would account for healthcare received outside the hospital by patients with SAB.

Nonvalvular cardiovascular device-related infections.

More than a century ago, Osler took numerous syndrome descriptions of cardiac valvular infection that were incomplete and confusing and categorized them into the cardiovascular infections known as infective endocarditis. Because he was both a clinician and a pathologist, he was able to provide a meaningful outline of this complex disease. Technical advances have allowed us to better subcategorize infective endocarditis on the basis of microbiological etiology. More recently, the syndromes of infective endocarditis and endarteritis have been expanded to include infections involving a variety of cardiovascular prostheses and devices that are used to replace or assist damaged or dysfunctional tissues (Table 1). Taken together, infections of these novel intracardiac, arterial, and venous devices are frequently seen in medical centers throughout the developed world. In response, the American Heart Association’s Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease wrote this review to assist and educate clinicians who care for an increasing number of patients with nonvalvular cardiovascular device–related infections. Because timely guidelines1,2 exist that address the prevention and management of intravascular catheter–related infections, these device-related infections are not discussed in the present Statement. View this table: TABLE 1. Nonvalvular Cardiovascular Device–Related Infections This review is divided into two broad sections. The first section examines general principles for the evaluation and management of infection that apply to all nonvalvular cardiovascular devices. Despite the marked variability in composition, structure, function, and frequency of infection among the various types of nonvalvular cardiovascular devices reviewed in this article, there are several areas of commonality for infection of these devices. These include clinical manifestations, microbiology, pathogenesis, diagnosis, treatment, and prevention. The second section addresses each device and describes unique clinical features of infection. Each device is placed into one of 3 categories—intracardiac, arterial, or venous—for discussion. ### Clinical Manifestations The specific signs and symptoms associated with an infection of a …

Staphylococcus aureus: The Persistent Pathogen

<i>Staphylococcus aureus</i>: The Persistent Pathogen

Increased incidence of Staphylococcus aureus bacteremia in hospitalized patients with acquired immunodeficiency syndrome.

Staphylococcus aureus is a common cause of bacterial infections in patients infected with human immunodeficiency virus (HIV). We studied 53 male patients who had 57 episodes of S. aureus bacteremia (SAB). The incidence of SAB per 1000 hospitalized patients was 13.2 among HIV-positive male patients and 0.8 among HIV-negative male patients, yielding a 16.5-fold increase in the odds ratio for SAB among HIV-positive male patients. Almost all episodes of SAB were community acquired. Long-term indwelling catheters were the most common predisposing factor. Prior antibiotic use was more frequently associated with SAB in HIV-positive patients than in HIV-negative patients. A trend was seen among HIV-positive patients toward more numerous infections with beta-lactam antibiotic-resistant (i.e., methicillin-resistant) S. aureus, but such patients had similar outcomes, even though they often did not receive vancomycin during the initial 48 hours of treatment. A better understanding of the epidemiology and clinical manifestations of SAB in HIV-positive patients will offer important opportunities for prevention of this frequent complication.