Staphylococcus aureus bacteremia. Current clinical patterns

Host stress drives tolerance and persistence: The bane of anti-microbial therapeutics

Antibiotic resistance, typically associated with genetic changes within a bacterial population, is a frequent contributor to antibiotic treatment failures. Antibiotic persistence and tolerance, which we collectively term recalcitrance, represent transient phenotypic changes in the bacterial population that prolong survival in the presence of typically lethal concentrations of antibiotics. Antibiotic recalcitrance is challenging to detect and investigate-traditionally studied under in vitro conditions, our understanding during infection and its contribution to antibiotic failure is limited. Recently, significant progress has been made in the study of antibiotic-recalcitrant populations in pathogenic species, including Mycobacterium tuberculosis, Staphylococcus aureus, Salmonella enterica, and Yersiniae, in the context of the host environment. Despite the diversity of these pathogens and infection models, shared signals and responses promote recalcitrance, and common features and vulnerabilities of persisters and tolerant bacteria have emerged. These will be discussed here, along with progress toward developing therapeutic interventions to better treat recalcitrant pathogens.

Antimicrobial Treatment Duration in Sepsis and Serious Infections

Sepsis mortality has improved following advancements in early recognition and standardized management, including emphasis on early administration of appropriate antimicrobials. However, guidance regarding antimicrobial duration in sepsis is surprisingly limited. Decreased antibiotic exposure is associated with lower rates of de novo resistance development, Clostridioides difficile-associated disease, antibiotic-related toxicities, and health care costs. Consequently, data weighing safety versus adequacy of shorter treatment durations in sepsis would be beneficial. We provide a narrative review of evidence to guide antibiotic duration in sepsis. Evidence is significantly limited by noninferiority trial designs and exclusion of critically ill patients in many trials. Potential challenges to shorter antimicrobial duration in sepsis include inadequate source control, treatment of multidrug-resistant organisms, and pharmacokinetic alterations that predispose to inadequate antimicrobial levels. Additional studies specifically targeting patients with clinical indicators of sepsis are needed to guide measures to safely reduce antimicrobial exposure in this high-risk population while preserving clinical effectiveness.

HANDOC: A Handy Score to Determine the Need for Echocardiography in Non-β-Hemolytic Streptococcal Bacteremia

Background

Non-β-hemolytic streptococci (NBHS) can cause infective endocarditis (IE). Echocardiography is used to diagnose IE, but it is not known which patients with NBHS bacteremia should undergo echocardiography.

Method

Medical records of patients with NBHS bacteremia in southern Sweden from 2012 to 2014 were studied retrospectively. The patients were divided into 2 cohorts. In the first, correlations between the reported data and IE were studied. These variables were used to construct the HANDOC score, which was then validated in the second cohort.

Results

Three hundred thirty-nine patients with NBHS bacteremia were included in the first cohort, of whom 26 fulfilled the criteria for IE. Several factors differed significantly between the patients with IE and those without. Among these variables, the presence of Heart murmur or valve disease; Aetiology with the groups of Streptococcus mutans, Streptococcus bovis, Streptococcus sanguinis, or Streptococcus anginosus; Number of positive blood cultures ≥2; Duration of symptoms of 7 days or more; Only 1 species growing in blood cultures; and Community-acquired infection were chosen to form the HANDOC score. With a cutoff between 2 and 3 points, HANDOC had a sensitivity of 100% and specificity of 73% in the first cohort. When tested in the validation cohort (n = 399), the sensitivity was 100% and the specificity 76%.

Conclusions

HANDOC can be used in to identify patients with NBHS bacteremia who have a risk of IE so low that echocardiography can be omitted; therefore, its implementation might reduce the use of echocardiography.

Prediction of methicillin-resistant Staphylococcus aureus bloodstream infection: do we need rapid diagnostic tests?

Staphylococcus aureus (SA) is the leading cause of bloodstream infection (BSI). The incidence of methicillin-resistant SA (MRSA) has decreased in France and Europe since one decade. Early and precise prediction of methicillin susceptibility is needed to improve probabilistic antibiotic therapy of MRSA-BSI. The aim of this study was to identify MRSA-BSI risk factors at admission and evaluate which patients need costly rapid diagnostic tests. A single-center retrospective descriptive study of all diagnosed SA-BSI was conducted in a French University Hospital between January 2015 and December 2016. All medical charts were reviewed. Univariate and multivariate analyses by a logistic regression model were performed on the data. We then build a prediction score of MRSA-BSI by assigning one point for each of the risk factor identified. During the study period, 151 SA-BSI were identified including 32 (21%) MRSA-BSI. In multivariate analysis, three factors were associated with MRSA-BSI: coming from long-term care facility, known previous MRSA colonization and/or infection, and chronic renal disease. Among our population, respectively, 5% and 100% had a MRSA-BSI when no or three risk factors were identified. Therefore, among the PCR performed, 43 (96%) could be avoided according to our clinical score. In our study, methicillin-susceptible SA and MRSA-BSI can be predictable by counting MRSA risk factors. This prediction rule could avoid the use of expensive rapid diagnostic tests. Prospective studies and prediction rules could help physicians to predict SA-BSI susceptibility to improve appropriate empiric therapy choice.

Onset of symptoms, diagnostic confirmation, and occurrence of multiple infective foci in patients with Staphylococcus aureus bloodstream infection: a look into the order of events and potential clinical implications

PURPOSE

Data on the systemic dissemination in Staphylococcus aureus bloodstream infection (SAB) remain sparse. We investigated the timing and the sequence of clinical symptoms, diagnostic confirmation, and occurrence of multiple infective foci in relation to three major infective foci.

METHODS

From 2006 to 2011, all adult patients with first-time SAB in Cologne and Freiburg, Germany were followed prospectively. The study was restricted to patients with short-term central venous catheter (CVC)-related SAB, vertebral osteomyelitis (VO), and infective endocarditis (IE). The collection date of the first positive blood culture was used as reference point for determining time to onset of clinical symptoms, microbiological findings, imaging results compatible with focal infection, and occurrence of additional infective foci.

RESULTS

We included 266 patients with first-time SAB. Among patients with CVC-related SAB, clinical onset, collection of the first positive blood culture, and microbiological confirmation almost coincided. In contrast, among patients with VO or IE, the onset of clinical symptoms most often preceded the collection of the first positive blood culture, and imaging and microbiological confirmation were most frequently obtained subsequent to the SAB diagnosis. CVC-related SAB was infrequently associated with further foci (n = 15/15.5%). Conversely, more than one infective focus was observed in 44 (56.4%) patient with VO and 68 (64.8%) patients with IE.

CONCLUSIONS

The sequence of clinical symptoms, diagnostic confirmation, and occurrence of multiple infective foci varied considerably with different infective foci in SAB. Based on these results, we propose a pragmatic and evidence-based terminology for the clinical course of SAB and suggest the terms "portal of entry", "infective focus", "multiple infective foci", and "dominant infective focus".

Hospital-acquired Staphylococcus aureus primary bloodstream infection: A comparison of events that do and do not meet the central line-associated bloodstream infection definition

BACKGROUND

This study was done to describe the incidence and outcomes of primary hospital-acquired bloodstream infection (HABSI) secondary to Staphylococcus aureus (SA) that did and did not meet the National Healthcare Safety Network's (NHSN's) definition for central line-associated bloodstream infection (CLABSI).

METHODS

Consecutive hospitalized patients during a 48-month study period with an SA HABSI were categorized according to those who did and did not meet the NHSN's definitions for CLABSI and non-CLABSI. Primary outcomes were mortality at 30 days and 1 year. Secondary outcomes were the incidence of complicated bacteremia and the need for operative intervention secondary to the HABSI event.

RESULTS

A total of 122 episodes of primary SA HABSIs were identified: 78 (64%) were CLABSIs, and 44 (36%) were non-CLABSIs. Overall 30-day and 1-year mortality in the cohort was 21.3% and 38.5%, respectively, and did not differ significantly between the 2 groups. Complicated SA HABSI was significantly more common in the non-CLABSI group (15.9% [n = 7] vs 0% [n = 0], P ≤ .001).

CONCLUSIONS

Primary SA HABSI was associated with significant 30-day and 1-year mortality. Complications from SA non-CLABSI requiring surgical intervention were significantly more common than in those with a CLABSI event. Our findings affirm the significance of non-device-related hospital-acquired infections.

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

Objective:

To evaluate a new classification for bloodstream infections that differentiates hospital acquired, healthcare associated, and community acquired in patients with blood cultures positive forStaphylococcus aureus.

Design:

Prospective, observational study.

Setting:

Three tertiary-care, university-affiliated hospitals in Dublin, Ireland, and Strasbourg, France.

Patients:

Two hundred thirty consecutive patients older than 18 years with blood cultures positive forS. aureus.

Methods:

S. aureusbacteremia (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-resistantStaphylococcus aureus(MRSA) were analyzed by pulsed-field gel electrophoresis (PFGE).

Results:

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.

Conclusion:

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.

Optimizing antibiotic therapy of bacteremia and endocarditis due to staphylococci and enterococci: new insights and evidence from the literature

Gram-positive cocci are a well-recognised major cause of nosocomial infection worldwide. Bloodstream infections due to methicillin-resistant Staphylococcus aureus, methicillin-resistant coagulase-negative staphylococci, and multi-drug resistant enterococci are a cause of concern for physicians due to their related morbidity and mortality rates. Aim of this article is to review the current state of knowledge regarding the management of BSI caused by staphylococci and enterococci, including infective endocarditis, and to identify those factors that may help physicians to manage these infections appropriately. Moreover, we discuss the importance of an appropriate use of antimicrobial drugs, taking in consideration the in vitro activity, clinical efficacy data, pharmacokinetic/pharmacodynamic parameters, and potential side effects.

Nosocomial Endocarditis

We analyzed 14 cases of nosocomial infective endocarditis which occurred over a seven-year period at the Beth Israel Hospital in Boston, and compared them with 90 cases of community-acquired endocarditis. Patients with nosocomial endocarditis were older, more often female, and had a greater incidence of underlying valvular heart disease and bacteremia precipitating invasive procedures (93% v 50%, P < .05). Forty-three percent of patients had infection at the site of prosthetic valves or intracardiac prosthetic material. The disease carried a significantly higher mortality than community-acquired endocarditis (43% v 11%, P < .01). The clinical presentation was acute and the infecting organisms reflected the site of origin of bacteremia, with staphylococci from skin and enterococci from urinary sources. Half of the cases in this series may have been prevented by the application of currently recommended preventive and therapeutic practices. Nosocomial endocarditis occurs in a definable sub-population of hospitalized patients and is potentially preventable.

Staphylococcus aureus bacteremia: targeting the source

Bacteremia due to Staphylococcus aureus is one of the major causes of morbidity and mortality in India, but studies targeting the source of Staphylococcus aureus bacteremia are lacking. S. aureus has a vivid armamentarium consisting of toxins, adhesins, and other virulence factors by virtue of which it can cause varied types of infections, sometimes of a serious nature. This review highlights the possible causes of S. aureus bacteremia, and discusses the necessity of tracing its source and eliminating it with proper antibiotic therapy to avoid recurrences or relapses.

Clinical management of Staphylococcus aureus bacteremia: a review

IMPORTANCE

Several management strategies may improve outcomes in patients with Staphylococcus aureus bacteremia.

OBJECTIVES

To review evidence of management strategies for S. aureus bacteremia to determine whether transesophageal echocardiography is necessary in all adult cases and what is the optimal antibiotic therapy for methicillin-resistant S. aureus (MRSA) bacteremia.

EVIDENCE REVIEW

A PubMed search from inception through May 2014 was performed to identify studies addressing the role of transesophageal echocardiography in S. aureus bacteremia. A second search of PubMed, EMBASE, and the Cochrane Library from January 1990 through May 2014 was performed to find studies addressing antibiotic treatment for MRSA bacteremia. Studies reporting outcomes from antibiotic therapy for MRSA bacteremia were included. All searches, which were limited to English and focused on adults, were augmented by review of bibliographic references from included studies. The quality of evidence was assessed using the Grades of Recommendation, Assessment, Development and Evaluation system with consensus of independent evaluations by at least 2 of the authors.

FINDINGS

In 9 studies with a total of 4050 patients, use of transesophageal echocardiography was associated with higher rates of a diagnosis of endocarditis (14%-28%) compared with transthoracic echocardiography (2%-15%). In 4 studies, clinical or transthoracic echocardiography findings did not predict subsequent transesophageal echocardiography findings of endocarditis. Five studies identified clinical or transthoracic echocardiography characteristics associated with low risk of endocarditis (negative predictive values from 93% to 100%). Characteristics associated with a low risk of endocarditis include absence of a permanent intracardiac device, sterile follow-up blood cultures within 4 days after the initial set, no hemodialysis dependence, nosocomial acquisition of S. aureus bacteremia, absence of secondary foci of infection, and no clinical signs of infective endocarditis. Of 81 studies of antibiotic therapy for MRSA bacteremia, only 1 high-quality trial was identified. In that study of 246 patients with S. aureus bacteremia, daptomycin was not inferior to vancomycin or an antistaphylococcal penicillin, each in combination with low-dose, short-course gentamicin (clinical success rate, 44.2% [53/120] vs 41.7% [48/115]; absolute difference, 2.4% [95% CI, -10.2% to 15.1%]).

CONCLUSIONS AND RELEVANCE

All adult patients with S. aureus bacteremia should undergo echocardiography. Characteristics of low-risk patients with S. aureus bacteremia for whom transesophageal echocardiography can be safely avoided have been identified. Vancomycin and daptomycin are the first-line antibiotic choices for MRSA bacteremia. Well-designed studies to address the management of S. aureus bacteremia are needed.

High nasal burden of methicillin-resistant Staphylococcus aureus increases risk of invasive disease

In a retrospective cohort study of 1,140 patients harboring methicillin-resistant Staphylococcus aureus, the nasal burden was low in 31%, category 1+ to 2+ in 54%, and category 3+ to 4+ in 15%. There was a significant trend in infection risk with increasing nasal burden (P = 0.007). In multivariate models, high nasal burden remained significantly associated with invasive infection.

Echocardiography is dispensable in uncomplicated Staphylococcus aureus bacteremia

Current Staphylococcus aureus bacteremia (SAB) practice guidelines stratify treatment duration according to the likelihood of complications and recommend transesophageal echocardiography (TEE) in all cases. The benefit of TEE in uncomplicated SAB has not been validated. We performed a retrospective analysis of TEE and transthoracic echocardiography (TTE) among hospitalized adults with SAB in 3 prior observational studies (2002-2003, 2005-2006, and 2008-2009). Echocardiograms were ordered at the attending physician's discretion. SAB cases were stratified into the following types: complicated (persistent bacteremia [duration ≥3 d], relapse, and/or secondary foci); device-associated (intracardiac prosthetic devices); suspected endocarditis (the presence of murmurs or emboli); and uncomplicated (bacteremia duration ≤2 d, no device and/or secondary foci). We encountered 960 SAB cases; 83 were excluded (57 death/transfer/discharge within 48 h; 19 contaminants/no treatment; 7 care withdrawn). TEE and TTE were performed within 0-28 days of SAB onset in 177 (20.2%) and 321 (36.6%) instances, respectively. TEE was positive (with signs of endocarditis) in 42/177 (23.7%) cases: 7/39 (17.9%) community associated and 35/138 (25.4%) health care associated. It was positive in 29/120 (24.2%) complicated, 3/11 (27.3%) device-associated, 9/15 (60.0%) suspected endocarditis, and 1/31 (3.2%) uncomplicated cases of SAB. TTE was positive in 25/321 (7.8%) cases of SAB, 1 was uncomplicated; it was negative in 20/30 (66.7%) TEE-positive cases. Follow-up of ≥100 days was possible in 282/361 (78.1%) uncomplicated SAB; many (46.8%) received ≤15 days of therapy. None of them had relapses or secondary foci.These findings suggest that echocardiography is dispensable in cases of uncomplicated community-associated and health care-associated SAB. It should be limited to subsets with clinical findings of endocarditis, persistence, intracardiac devices, secondary foci, and relapse. The cost effectiveness of TTE prior to TEE among these patients is unknown.

Persistent Staphylococcus aureus bacteremia: a prospective analysis of risk factors, outcomes, and microbiologic and genotypic characteristics of isolates

Persistent Staphylococcus aureus bacteremia (SAB) that fails to respond to appropriate antibiotic therapy is associated with poor outcomes. Comprehensive prospective studies on risk factors and outcomes of persistent bacteremia are limited. We investigated outcomes and risk factors encompassing clinical, pharmacokinetic, microbiologic, and genotypic characteristics associated with persistent bacteremia using a case-control study nested in a prospective cohort of patients with SAB at a tertiary-care hospital from August 2008 through September 2010. We compared the clinical characteristics, management, and outcomes of patients with persistent bacteremia (≥7 d) with controls with resolving bacteremia (<3 d). To detect associations between microbiologic and genotypic characteristics of methicillin-resistant S. aureus (MRSA) isolates and persistent bacteremia, we determined the heteroresistance phenotype, SCCmec type, agr genotype and functionality, multilocus sequence typing, and presence of 41 virulence genes. Our cohort consisted of 483 patients; 76 (15.7%) had persistent bacteremia, 212 (43.5%) had resolving bacteremia. In the multivariate analysis, independent risk factors associated with persistent bacteremia were community-onset bacteremia (odds ratio [OR], 2.91; 95% confidence interval [CI], 1.24-6.87), bone and joint infection (OR, 5.26; 95% CI, 1.45-19.03), central venous catheter-related infection (OR, 3.36; 95% CI, 1.47-7.65), metastatic infection (OR, 36.22; 95% CI, 12.71-103.23), and methicillin resistance (OR, 16.99; 95% CI, 5.53-52.15). For patients with eradicable foci, delay (>3 d) in the removal of the infection focus was significantly associated with persistent bacteremia (OR, 2.18; 95% CI, 1.05-4.55). There were no significant associations of persistent bacteremia with high vancomycin minimal inhibitory concentration, vancomycin heteroresistance, and microbiologic/genotypic characteristics of MRSA isolates. However, initial vancomycin trough level <15 mg/L was an independent risk factor for persistent MRSA bacteremia (OR, 4.25; 95% CI, 1.51-11.96) in the multivariate analysis. Clinical outcomes were significantly worse for patients with persistent bacteremia. Relapse of bacteremia and attributable mortality within 12 weeks after SAB were significantly higher in patients with persistent bacteremia than in those with resolving bacteremia (9.2% [7/76] vs. 2.4% [5/212], p = 0.02 and 21.1% [16/76] vs. 9.4% [20/212], p = 0.009, respectively). In conclusion, patients with SAB should be given early aggressive treatment strategies, including early source control and maintenance of a vancomycin trough level ≥15 mg/L, to reduce the risk of persistent bacteremia.

Comparative epidemiology of bacteremia due to methicillin-resistant Staphylococcus aureus between older and younger adults: a propensity score analysis

OBJECTIVE

We evaluated the clinical and molecular epidemiology of bloodstream infections (BSIs) due to methicillin-resistant Staphylococcus aureus (MRSA) in older versus younger patients treated with vancomycin, determining the independent effect of increased age on outcomes.

DESIGN

Observational retrospective cohort study.

SETTING

Detroit Medical Center, level I trauma center.

PATIENTS

Adult older (65 years and older) and younger (younger than 65 years) patients with documented BSIs due to MRSA treated with vancomycin (2005-2010).

METHODS

Collected demographics, comorbidities, microbiology, treatment, outcomes. Multivariable model used to generate propensity score for each patient on the basis of the probability of being 65 years of age or older.

RESULTS

Three hundred twenty patients were eligible (69 patients 65 years and older; 251 patients younger than 65 years). Catheter-related infections and endocarditis were the most common sites of infection for older (20.3%) and younger (19.1%) adults, respectively. Median first total 24-hour vancomycin dose (1,000 vs 2,000 mg; [Formula: see text]) and initial trough (13.1 vs 15.0 mg/L; [Formula: see text]) was significantly lower in older versus younger patients. Vancomycin treatment failure rates were similar among older and younger patients (49.3% vs 53.4%; [Formula: see text]). In multivariable analysis of outcomes, after controlling for predictors of older age, there was no difference in clinical outcomes between older and younger adults.

CONCLUSIONS

After accounting for confounders associated with increased age, failure rate of patients with BSIs due to MRSA treated with vancomycin was similar between older and younger patients. Older adults were less likely to have optimal vancomycin dosing and initial trough levels than younger patients. Efforts should be made to optimize dosing of medications such as vancomycin in older adults.

Treatment duration for uncomplicated Staphylococcus aureus bacteremia to prevent relapse: analysis of a prospective observational cohort study

Practice guidelines recommend at least 14 days of antibiotic therapy for uncomplicated Staphylococcus aureus bacteremia (SAB). However, these recommendations have not been formally evaluated in clinical studies. To evaluate the duration of therapy for uncomplicated SAB, we analyzed data from our prospective cohort of patients with SAB. A prospective observational cohort study was performed in patients with SAB at a tertiary-care hospital in Korea between August 2008 and September 2010. All adult patients with SAB were prospectively enrolled and observed over a 12-week period. Uncomplicated SAB was defined as follows: negative results of follow-up blood cultures at 2 to 4 days, defervescence within 72 h of therapy, no evidence of metastatic infection, and catheter-related bloodstream infection or primary bacteremia without evidence of endocarditis on echocardiography. Of 483 patients with SAB, 111 met the study criteria for uncomplicated SAB. Fifty-three (47.7%) had methicillin-resistant SAB. When short-course therapy (<14 days) and intermediate-course therapy (≥14 days) were compared, the treatment failure rates (10/38 [26.3%] versus 16/73 [21.9%]) and crude mortality (7/38 [18.4%] versus 16/73 [21.9%]) did not differ significantly between the two groups. However, short-course therapy was significantly associated with relapse (3/38 [7.9%] versus 0/73; P = 0.036). In multivariate analysis, primary bacteremia was associated with a trend toward increased treatment failure (P = 0.06). Therefore, in the treatment of uncomplicated SAB, it seems reasonable to consider at least 14 days of antibiotic therapy to prevent relapse, as practice guidelines recommend. Because of its poor prognosis, primary bacteremia, even with a low risk of complication, should not be treated with short-course therapy.

Infectious disease emergencies: frontline clinical pearls

This article reviews various infectious disease emergencies from an internist's perspective. Key epidemiologic, diagnostic, and therapeutic points are reviewed with an emphasis on timely and appropriate initial management. The content serves to highlight essential points that are discussed in subsequent articles in this issue and to elucidate pearls that may facilitate timely and appropriate management.

Incidence and risk factors for endocarditis among patients with health care-associated Staphylococcus aureus bacteraemia

BACKGROUND

Staphylococcus aureus infective endocarditis (IE) is a characteristic community-acquired infection, however most cases are presently occurring in the health care setting. This study investigated the incidence and risk factors for S. aureus IE in patients with nosocomial and health care-associated S. aureus bacteraemia (SAB).

METHODS

Consecutive patients with health care-associated and hospital-acquired SAB were prospectively recruited over a 30-month period. Patients were followed up for at least 12 weeks after the initial positive blood culture result. The primary endpoint was the diagnosis of IE.

RESULTS

IE occurred in 11 of 303 patients (3.6%). Patient characteristics at diagnosis and that were associated with IE included the number of positive blood cultures obtained during hospitalization (p = 0.003), the duration of bacteraemia (p < 0.001), bacteraemia persisting for > 3 days (odds ratio (OR) 14.5, 95% confidence interval (CI) 4.0-52.8; p < 0.001), performance of echocardiography (OR 1.88, 95% CI 1.69-2.1; p = 0.001), presence of a well known predisposing risk for IE (OR 57.2, 95% CI 13.6-240.5; p < 0.001), a non-fatal McCabe score (OR 2.10, 95% CI 1.4-3.1; p = 0.02), and the duration of fever related to the infection (p = 0.026). On multivariable analysis, the presence of a predisposing risk for IE, prolonged bacteraemia, and non-fatal McCabe score remained significantly associated with IE.

CONCLUSIONS

In this study the incidence of IE was lower than previously reported. Three clinical characteristics were identified as risk factors for IE among patients with SAB acquired in a health care setting.

Appropriate use of echocardiography in managing Staphylococcus aureus bacteremia

Staphylococcus aureus bacteremia (SAB) is increasing, both in the community and in healthcare settings. Accurate and timely diagnosis of underlying infective endocarditis (IE) is critical for optimal management of SAB cases as it has significant management and prognostic implications. Reported prevalence of IE in patients with SAB varies depending on the study population, and ranges from 10 to 30%. As clinical presentation of IE can be nonspecific, echocardiography is usually recommended in SAB cases to 'rule out' IE. Due to its poor sensitivity (<50%), especially for diagnosing prosthetic valve IE, transthoracic echocardiography is considered inadequate in this setting and clinicians have to rely on transesophageal echocardiography (TEE) to confirm or exclude endocarditis in SAB cases. Although some experts recommend TEE in all patients presenting with SAB, it is believed that the use of TEE could be guided by individual patient risk factors, mode of acquisition of SAB and clinical presentation. In this article, published data regarding the use of TEE in the SAB population are reviewed and a simplified algorithm to guide use of TEE in SAB cases is proposed.

Infectious Disease Consultation for Staphylococcus aureus Bacteremia Improves Patient Management and Outcomes

BACKGROUND: Staphylococcus aureus bacteremia (SAB) is a common, severe infectious disease with accepted standards of care. METHODS: A retrospective cohort study of all 233 SAB cases at the Minneapolis Veterans Affairs Medical Center (MVAMC) between October 2004 and February 2008 was performed to measure the impact of Infectious Disease (ID) consultation on conformance to standards and patient outcomes. Outcomes were classified as survived without relapse, relapsed, or died without relapse. ID involvement was classified as consultation, curbside, or no involvement. RESULTS: ID involvement occurred in 179/233 cases (77%). Management conformed to accepted standards in 162/197 cases (82%) evaluable for conformance. ID involvement was associated with increased conformance in univariable analysis and multivariable analysis adjusted for propensity for ID consultation (OR 5.9, 95% CI 2.5 - 13.8). Relapse occurred in 14/156 cases (9%) in which therapy conformed to standards compared with 8/35 cases (23%) in which therapy did not conform to standards (p=0.045). Relapse was more common in older patients (OR 1.05, CI 1.01-1.09) and in cases without ID involvement (OR 3.02, CI 1.003-9.1). Death was associated with greater Charlson Index scores (OR 1.89, CI 1.4-2.5). Of 111 cases with definitely or possibly infected devices, relapse occurred in 9/92 cases (9.8%) in which the device was wholly or partially removed compared with 6/19 cases (32%) in which the device was left in place (p=0.02). CONCLUSIONS: ID involvement in SAB cases was associated with increased adherence to accepted standards and fewer relapses. ID consultation should be performed for all SAB cases.

Clinical significance and outcome of polymicrobial Staphylococcus aureus bacteremia

OBJECTIVES

The clinical significance of polymicrobial Staphylococcus aureus bacteremia (SAB) remains unclear. We therefore compared the clinical features and outcomes of polymicrobial and monomicrobial SAB.

METHODS

A prospective cohort study of patients with SAB was performed during a 20-months. Polymicrobial SAB was defined as the simultaneous isolation of S. aureus and other microorganisms from blood cultures. However, Corynebacterium spp., Bacillus spp., and coagulase-negative staphylococci were considered contaminants unless they were related to device infection and grew in two or more blood cultures.

RESULTS

During the study period, 44 (10%) patients had polymicrobial and 412 (90%) had monomicrobial SAB. A total of 54 microorganisms were isolated from the former, with Enterococcus spp. (22%) being the most common. Independent risk factors for polymicrobial SAB included neutropenia (odds ratio [OR] 3.5, p = 0.02), biliary tract catheters (OR 5.0, p = 0.001), and intra-abdominal infection (OR 10.3, p < 0.001). Clinical outcomes were significantly worse among patients with polymicrobial than monomicrobial SAB, including bacteremia-related and 7-day mortality rates. Independent predictors of bacteremia-related mortality were solid tumors (HR 2.0, p = 0.03) and polymicrobial SAB (HR 2.8, p = 0.007).

CONCLUSIONS

Polymicrobial SAB is associated with more severe illness than monomicrobial SAB, with neutropenia, biliary tract catheters and intra-abdominal infection being significant risk factors for polymicrobial SAB.

Purulent Meningitis as an Unusual Presentation of Staphylococcus aureus Endocarditis: A Case Report and Literature Review

On presentation of Staphylococcus aureus endocarditis, unusual manifestations may represent the main clinical features of the disease. Isolated bacterial meningitis as the first manifestation of endocarditis is considered to be an unusual neurological complication. Here, we describe a case S. aureus endocarditis presenting as isolated meningitis and mimicking meningococcal septicaemia. Because of the high mortality rate of the disease, the prompt recognition of this infectious syndrome is of crucial importance for the correct management of patients.

Predisposing factors, disease progression and outcome in 430 prospectively followed patients of healthcare- and community-associated Staphylococcus aureus bacteraemia

Staphylococcus aureus bacteraemia (SAB) episodes identified in a prospective multicentre study during 1999-2002 (not including MRSA) were followed up by an infectious disease specialist. The aim of this study was to compare predisposing factors, disease progression and outcome of healthcare (HA)- and community (CA)-associated SAB. Of 430 SAB episodes, 232 (54%) were HA. The HA-SAB patients were significantly older and more chronically ill compared to CA-SAB. Deep infection foci prevalence within three days of onset of SAB for HA versus CA were deep-seated abscesses (26% vs 37%, P < 0.05), pneumonia [25% vs 31%, non-significant (NS)], osteomyelitis (24% vs 36%, P<0.01), permanent foreign body (24% vs 9%, P<0.001), endocarditis (11% vs 15%, NS), septic arthritis (9% vs 13%, NS) and no infection focus (3% vs 6%, NS). The case fatality rates for HA-SAB versus CA-SAB at 28 days were 14% vs 11% (NS). Independent risk factors according to multivariate analysis for a fatal outcome were age, chronic alcoholism, immunosuppressive treatment, ultimately or rapidly fatal underlying diseases, severe sepsis on the onset of SAB, S. aureus pneumonia and endocarditis. As a result of a prospective study design, meticulous infection foci search and infectious disease specialist follow-up of each SAB episode, the case fatality remained low and 97% of the HA-SAB episodes presented infection foci within three days of onset of bacteraemia.

Complicated Community-Acquired Staphylococcus Endocarditis and Multiple Lung Abscesses: Case Report and Review of Literature

Background. Isolated tricuspid valve endocarditis in the absence of risk factors in the community setting is very rare and can be easily missed in patients with hitherto normal valves. Case Presentation. We present a case of a 49 year old gentleman who presented with generalized body aches, fever, and jaundice and was initial diagnosed as hepatitis. He subsequently developed recurrent episodes of panic attacks and shortness of breath and later multiple skin abscesses. Further investigations excluded pulmonary embolism but revealed multiple abscesses in the body including the lungs. Blood cultures and culture from abscesses grew S. aureus. An initial transthoracic echocardiogram was normal. A transesophageal echocardiogram subsequently confirmed endocarditis on a normal natural tricuspid valve and multiple lung abscesses. He was successfully treated with appropriate antibiotics. Conclusion. We discuss the pathogenesis of this patient's presentation highlight the need for assessment and proper evaluation of patients with unexplained bacteremia.

Use of echocardiography in the diagnosis and management of infective endocarditis

The first use of echocardiography in infective endocarditis (IE) was described in 1973. Since then, echocardiography has emerged as a major tool for the diagnosis and management of this disease. In general, transthoracic echocardiography (TTE) is adequate for diagnosing IE in cases where cardiac structures-of-interest are well visualized. Specific situations where transesophageal echocardiography is preferred over TTE include the presence of a prosthetic device, suspected periannular complications, children with complex congenital cardiac lesions, selected patients with Staphylococcus aureus bacteremia, and certain pre-existing valvular abnormalities that make TTE interpretation problematic (eg, calcific aortic stenosis). Echocardiography is also useful for risk stratification. Evidence suggests that vegetation size can predict embolic complications, although the data are inconsistent. Careful clinical assessment is essential to the proper use of echocardiography in diagnosing IE, visualizing complications related to IE, and evaluating candidacy for surgical intervention.

Staphylococcus aureus bacteremia in patients with hematological malignancies and/or agranulocytosis

A total of 6,253 cases of Staphylococcus aureus bacteremia, including 274 (4.4%) endocarditis cases, were registered in Denmark in the period 1975-1984. Patients with hematological malignancies and/or agranulocytosis accounted for 479 of the bacteremia cases. The incidence of endocarditis in this group of patients was only 0.4% as compared to 4.7% in other patients with staphylococcal bacteremia (p less than 0.01). The lower incidence of endocarditis complicating bacteremia in these patients may justify a shorter course of therapy than usually recommended for suspected endocarditis. Patients with hematological malignancies and other patients with agranulocytosis had a higher mortality (49 and 46%, respectively) than other patients with S. aureus bacteremia (33%). The highest mortality was found in patients with multiple myeloma (71%, p less than 0.01), the lowest in patients with acute lymphocytic leukemia (28%, p less than 0.01). The higher mortality in these patients may indicate that empiric antibiotic regimens in granulocytopenic patients should include a specific anti-staphylococcal agent.

Endocarditis caused by Staphylococcus aureus: A reappraisal of the epidemiologic, clinical, and pathologic manifestations with analysis of factors determining outcome

Staphylococcus aureus is the leading cause of infectious endocarditis and its mortality has remained high despite better diagnostic and therapeutic procedures over time. We conducted a retrospective review of 133 cases of definite S. aureus endocarditis seen at a single tertiary care hospital over 22 years to assess changes in the epidemiology and incidence of the infection, manifestations, outcome, risk factors for mortality, and impact of cardiac surgery on prognosis.Patients were classified into 2 groups: 1) right-sided endocarditis (64 patients) and 2) left-sided endocarditis (69 patients). While the number of cases of left-sided endocarditis remained steady at 1-3 cases per 10,000 admissions, the incidence of right-sided endocarditis, after a peak in the early 1990s, declined to almost disappear in 2001. Among the cases of right-sided endocarditis, we found 2 subsets of patients with different clinical features and prognosis: the first subset comprised 53 intravenous drug abusers, and the second subset comprised 11 patients with catheter-associated S. aureus bacteremia and endocarditis. Fifty-one patients were human immunodeficiency virus (HIV)-positive drug abusers, most of whom (80.3%) had right-sided endocarditis. We did not find differences in mortality between HIV-positive and HIV-negative individuals; mortality seemed to depend more on the site of the heart involved than on HIV status.Among the cases of left-sided endocarditis, the mitral valve was more commonly involved than the aortic valve (61% vs. 30%). Overall, 74% of patients with left-sided endocarditis developed 1 or more cardiac or extracardiac complication. In comparison, only 23.4% of patients with right-sided endocarditis developed complications.Prosthetic valve endocarditis (PVE) was hospital-acquired more frequently than native valve endocarditis (NVE). Patients with PVE had a shorter duration of symptoms until diagnosis and presented with or developed cardiac murmurs less frequently than patients with NVE. Cardiac failure (49%), renal failure (43%) and central nervous system (CNS) events (35%) were frequently observed in patients with both PVE and NVE. Valve replacement was more frequently needed and more rapidly performed in patients with PVE than in their counterparts with NVE.The overall mortality of patients with right-sided endocarditis was 17%. While the mortality of right-sided endocarditis in injection drug users was 3.7%, the mortality of patients with right-sided endocarditis associated with infected intravenous catheters was 82% (odds ratio [OR], 0.01; 95% confidence interval [CI], 0.001-0.07). For left-sided endocarditis mortality was 38% and was not significantly different in patients with NVE or PVE (OR, 0.65; 95% CI, 0.23-1.87). CNS complications were associated with mortality in both NVE (OR, 6.55; 95% CI, 1.78-24.04) and PVE (OR, 32; 95% CI, 2.63-465.40). Development of 2 or 3 complications was associated with an increased risk of mortality (OR, 5.59; 95% CI, 1.08-28.80 and OR, 9.25; 95% CI, 1.36-62.72 for 2 vs. 1 complication and for 3 vs. 2 complications, respectively).Surgical treatment did not significantly influence mortality in cases of NVE, (OR, 3.19; 95% CI, 0.76-13.38) but significantly improved the prognosis of patients with PVE (OR, 69; 95% CI, 2.89-1647.18).S. aureus endocarditis is an aggressive, often fatal, infection. The results of the current study suggest that valve replacement will improve the outcome of infection, particularly in patients with PVE.

Staphylococcus aureus bacteraemia of unknown primary source: where do we stand?

There is no generally held definition of Staphylococcus aureus bacteraemia (SAB) of unknown source. For this paper, we consider it to occur when one or more positive blood cultures obtained from a patient grows S. aureus and the origin of the bacteraemia is uncertain after history, physical examination, chest radiography and any further investigations provoked by clinical findings. The incidence of SAB appears to be rising, particularly community-acquired (CA), but also hospital- or healthcare-acquired (HA). Major drivers appear to be intravenous drug use and increasing use of indwelling intravascular devices. There is an increasing prevalence of meticillin-resistant S. aureus (MRSA), both CA and HA. There is increasing hospital acquisition of MRSA that is phenotypically like CA strains, and there is increasing community-based treatment of HA infection. Metastatic infection is a risk of SAB. Infective endocarditis (IE) is a longstanding dreaded concern of SAB. Transoesophageal echocardiography appears to be a superior modality of recognising IE in the context of SAB and can guide the duration of therapy. Prosthetic joints and heart valves are at particular risk of haematogenous seeding from SAB. Implications of the rise of CA-MRSA in terms of metastatic infection warrant further study.

Frequency and risk factors for deep focus of infection in children with Staphylococcus aureus bacteremia

BACKGROUND

Staphylococcus aureus bacteremia (SAB) in children may be associated with development of deep-seated foci of infection, often prompting extensive diagnostic testing. The objective of this study was to establish the frequency and risk factors for deep foci of infection from SAB in pediatric patients.

METHODS

Medical charts of all children admitted with SAB to a tertiary-care center from January 1992 to June 2006 were reviewed. Study outcome was the presence of a deep focus of infection as documented by positive echocardiogram, bone imaging or abdominal imaging.

RESULTS

We studied 298 children, of whom 190 (64%) had echocardiograms, 116 (39%) had abdominal imaging, and 103 (35%) had bone imaging. Forty-seven subjects (16%) had symptoms of a deep focus of infection on discovery of SAB, which then was confirmed by 1 of the 3 tests. Eleven (3.7%) additional subjects had a clinically unsuspected deep focus identified before discharge. All children with an unsuspected deep focus of infection had either an underlying medical condition that potentially obscured the diagnosis or a central venous catheter. More than 1 day of positive blood cultures was associated with an unsuspected deep-seated infection (P < 0.01). Endocarditis was uncommon (2.7%), and occurred only in children with known congenital heart disease or with a central catheter.

CONCLUSIONS

Deep-seated infections from SAB in children are most often clinically apparent at discovery of bacteremia. Unsuspected deep-seated infection is uncommon and confined to specific hosts. Routine diagnostic imaging is not indicated in all children with SAB.

Complicating infectious foci in patients with Staphylococcus aureus or Streptococcus species bacteraemia

Complicating infectious foci resulting from haematogenous or local spread of microorganisms are observed frequently in patients with Staphylococcus aureus bacteraemia (SAB) or Streptococcus species bacteraemia (SSB). The aim of this study was to compare the epidemiology of complicating infectious foci during SAB and SSB in a university hospital in The Netherlands. The charts of all adult patients diagnosed with SAB or SSB (except for Streptococcus pneumoniae bacteraemia) from July 2002 until December 2004 were reviewed retrospectively. Overall, 180 immunocompetent patients were identified, 127 with SAB and 53 with SSB. The percentage of patients with complicating infectious foci (39% of SAB patients, 25% of SSB patients) did not differ significantly between the groups. Endocarditis and cerebral involvement, however, were significantly more common in the SSB group. Of all complicating infectious foci, 32% lacked guiding signs or symptoms and 10% were detected only at autopsy. Factors associated with the development of complicating infectious foci were a delay in treatment for more than 48 h after the onset of symptoms, community acquisition, persistently positive blood cultures, congenital heart disease, and the presence of foreign bodies or prosthetic valves. Infection-related mortality was 18% in SAB patients and 11% in SSB patients and was significantly higher in patients with complicating infectious foci (29 vs. 9%). In conclusion, complicating infectious foci develop in approximately one-third of all patients with SAB and SSB. An active approach that entails searching for the complicating infectious foci is warranted in these patients, because only two-thirds of complicated infectious foci have guiding symptoms or signs, and infection-related mortality is significantly increased in patients with complicating infectious foci compared to patients without these infections.

Why is long-term therapy required to cure tuberculosis?

The authors argue that understanding and countering general bacterial mechanisms of phenotypic antibiotic resistance may hold the key to reducing the duration of treatment of all recalcitrant bacterial infections, including tuberculosis.

The role of transthoracic echocardiography in excluding left sided infective endocarditis in Staphylococcus aureus bacteraemia

In all patients with Staphylococcus aureus bacteraemia a transoesophageal echocardiogram is recommended to exclude infective endocarditis. We determined that a finding of normal to trivial valvular regurgitation on transthoracic echocardiogram in these patients significantly reduced the probability of infective endocarditis. Furthermore, in the absence of embolic phenomena the likelihood of infective endocarditis was less than 2%. This probability could be further reduced if the echocardiogram was performed greater than 5 days after the bacteraemia. Therefore, in the assessment of patients with S. aureus bacteraemia a transoesophageal echocardiogram is not always required to exclude infective endocarditis.

Classifying spa types in complexes improves interpretation of typing results for methicillin-resistant Staphylococcus aureus

A total of 382 isolates of methicillin-resistant Staphylococcus aureus originating from three Austrian regions and one adjacent Italian region (Vienna, Lower Austria, North Tyrol, and South Tyrol) were typed by DNA sequence analysis of the variable repeat region of the protein A gene (spa typing). The strain collection consisted of arbitrarily chosen isolates originating from clinical specimens taken in the years 2003 to 2005 at 17 hospitals. The most common spa types found were t001 (28.8% of all isolates), t190 (27.0%), t008 (14.1%), and t041 (11.3%). The 42 remaining spa types accounted for Collapse

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MESH Headings

• Austria
• Bacterial Typing Techniques/methods
• DNA, Bacterial/chemistry
• DNA, Bacterial/genetics
• Humans
• Italy
• Methicillin Resistance
• Molecular Epidemiology
• Repetitive Sequences, Nucleic Acid/genetics
• Sequence Analysis, DNA
• Staphylococcal Infections/microbiology
• Staphylococcal Protein A/genetics
• Staphylococcus aureus/classification
• Staphylococcus aureus/genetics
• Staphylococcus aureus/isolation & purification

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Grants Collapse

Affiliation(s)

Werner Ruppitsch Austrian Agency for Health and Food Safety, Institute of Medical Microbiology and Hygiene, Spargelfeldstrasse 191, A-1226 Vienna, Austria.
Alexander Indra
Anna Stöger
Barbara Mayer
Silke Stadlbauer
Günther Wewalka
Franz Allerberger

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[Staphylococcus aureus infections: new challenges from an old pathogen]

Staphylococcus aureus is a versatile organism with several virulent characteristics and resistance mechanisms at its disposal. It is also a significant cause of a wide range of infectious diseases in humans. S. aureus often causes life-threatening deep seated infections like bacteremia, endocarditis and pneumonia. While traditionally confined mostly to the hospital setting, methicillin-resistant S. aureus (MRSA) is now rapidly becoming rampant in the community. Community-acquired MRSA is particularly significant because of its potential for unchecked spread within households and its propensity for causing serious skin and pulmonary infections. Because of the unfavorable outcome of many MRSA infections with the standard glycopeptide therapy, new antimicrobial agents belonging to various classes have been introduced and have been evaluated in clinical trials for their efficacy in treating resistant staphylococcal infections. A number of preventive strategies have also been suggested to contain the spread of such infections. In this review, we address the recent changes in the epidemiology of S. aureus and their impact on the clinical manifestations and management of serious infections. We also discuss new treatment modalities for MRSA infections and emphasize the importance of preventive approaches.

Persistence in Staphylococcus aureus bacteremia: incidence, characteristics of patients and outcome

Staphylococcus aureus bacteremia often persists. The reasons for persistence and its outcome are poorly defined. We conducted a prospective-observational study among 245 consecutive S. aureus (MRSA: n=125; MSSA: n=120) bacteremias (>or=1 positive blood cultures (BC)) among 234 adults (18-103-y-old; median=59 y) hospitalized during 1 January 2002-31 December 2002 at a 600-bed teaching hospital. Measurements included bacteremia duration, complication-rate (metastatic infection, relapse or attributable mortality) and outcome. Bacteremia duration was measured based on follow-up BC among 193 patients and estimated based on symptoms resolution in the rest. Measured (1-59 d; median=2) and estimated (median=1 d) duration correlated (r=0.885) though positive follow-up BC was often detected without fever (57/105 patients, 54.3%). Persistence (defined as bacteremia for >or=3 d) was noted in 84 cases (38.4%). Complication-rate increased steadily with bacteremia duration (6.6%, 24.0% and 37.7% in bacteremia for 1-2, 3 and >or=4 d, respectively; p=0.05). Cox regression analysis revealed that bacteremia duration correlated positively with endovascular sources (p=0.006), vancomycin treatment (p=0.016), cardiovascular prosthesis (p=0.025), metastatic infections (p=0.025) and diabetes (p=0.038). It is concluded that persistent bacteremia is a feature of S. aureus infection, irrespective of oxacillin susceptibility, associated with worse outcome. Risk factors include endovascular sources, cardiovascular prosthesis, metastatic infections, vancomycin treatment and diabetes. Patients at risk may benefit from novel treatment strategies.

Bacteraemia due to Staphylococcus aureus

AIMS

To describe the clinical features and outcome of bacteraemia due to Staphylococcus aureus in children admitted to a rural Kenyan hospital.

METHODS

Retrospective case review of all children with a positive blood culture for S aureus admitted to Kilifi District Hospital, Kenya, between January 1996 and December 2001.

RESULTS

Ninety seven children (median age 17 months, range 1 day to 12 years; 46 male) with bacteraemia due to S aureus were identified, accounting for 5% of all positive blood cultures; 10 were considered to be nosocomially acquired. A focus that was clinically consistent with staphylococcal infection was identified in 52 cases; of these, 88% had multiple foci. Children with a focus were likely to be older, present later, and have a longer duration of hospital stay. Most children in this group (90%) received intravenous cloxacillin on admission in contrast to none of those without a focus. In the former group, mortality was only 6% compared to 47% among those without a focus; 10/13 neonates without an apparent staphylococcal focus died compared to none of the 11 with a focus. Eight of the 10 neonates in the former group died within 48 hours of admission, before empirical antibiotics could be changed to include cloxacillin.

CONCLUSIONS

Children most at risk of death associated with bacteraemia due to S aureus are least likely to have clinical features traditionally associated with this infection.

Staphylococcus aureus bacteremia and endocarditis: the Grady Memorial Hospital experience with methicillin-sensitive S aureus and methicillin-resistant S aureus bacteremia

BACKGROUND

Staphylococcus aureus has become the leading cause of endocarditis in most published series, and nosocomial acquisition is becoming more frequent. Previous studies involved community acquired methicillin-sensitive S aureus (MSSA), but recently, methicillin-resistant S aureus(MRSA) infection has increased. This may reflect the growing presence of this microorganism in clinical practice. Few data exist comparing the relative rates of endocarditis with MSSA and MRSA bacteremia. The purpose of this study was to compare these rates in a bacteremic population referred for diagnostic echocardiography.

METHODS

Since July 1999, the demographic and clinical information of 104 consecutive patients with at least 2 blood cultures with positive results for S aureus who were referred for echocardiography to be evaluated for endocarditis at Grady Memorial Hospital (Atlanta, Ga) have been entered into a database. This database has further been restricted to patients who have undergone either a transesophageal echocardiogram or a transthoracic echocardiogram.

RESULTS

Of the 104 patients with S aureus bacteremia, 53 had an infection of MSSA and 51 had an infection of MRSA. There were 33 patients (31.7%) with echocardiographically confirmed endocarditis, 23 patients (43.4%) in the MSSA group versus 10 patients (19.6%) in the MRSA group (P <.009). Community-acquired MSSA bacteremia was the cause of most of the community-acquired S aureus endocarditis (20 patients [87%] vs 3 patients [30%], P =.004), and the nosocomial-acquired MRSA bacteremia was the cause of most of the nosocomial-acquired S aureus endocarditis (3 patients [13%] vs 7 patients [70%], P =.0001).

CONCLUSION

Our study confirms that S aureus bacteremia is associated with high rates of endocarditis. MSSA bacteremia is associated with higher rates of endocarditis than MRSA. Community MSSA is the cause of most of the community endocarditis, whereas nosocomial MRSA is the cause of most of the MRSA endocarditis. Patients with S aureus bacteremia should be aggressively evaluated for endocarditis.

A prospective multicenter study of Staphylococcus aureus bacteremia: incidence of endocarditis, risk factors for mortality, and clinical impact of methicillin resistance

Our objectives were to determine the incidence of endocarditis in patients whose Staphylococcus aureus bacteremia was community-acquired, related to hemodialysis, or hospital-acquired; to assess clinical factors that would reliably distinguished between S. aureus bacteremia and S. aureus endocarditis; to assess the emergence of methicillin-resistant S. aureus (MRSA) as a cause of endocarditis; and to examine risk factors for mortality in patients with S. aureus endocarditis. We conducted a prospective observational study in 6 university teaching hospitals; we evaluated 505 consecutive patients with Staphylococcus aureus bacteremia. Thirteen percent of patients with S. aureus bacteremia were found to have endocarditis, including 21% with community-acquired S. aureus bacteremia, 5% with hospital-acquired bacteremia, and 12% on hemodialysis. Infection was due to MRSA in 31%. Factors predictive of endocarditis included underlying valvular heart disease, history of prior endocarditis, intravenous drug use, community acquisition of bacteremia, and an unrecognized source. Twelve patients with bacteremia had a prosthetic valve; 17% developed endocarditis. Unexpectedly, nonwhite race proved to be an independent risk factor for endocarditis by both univariate and multivariate analyses. Persistent bacteremia (positive blood cultures at day 3 of appropriate therapy) was identified as an independent risk factor for both endocarditis and mortality, a unique observation not reported in other prospective studies of S. aureus bacteremia. Patients with endocarditis due to MRSA were significantly more likely to have complicating renal insufficiency and to experience persistent bacteremia than those with endocarditis due to MSSA. The 30-day mortality was 31% among patients with endocarditis compared to 21% in patients who had bacteremia without endocarditis (p = 0.055). Risk factors for death due to endocarditis included severity of illness at onset of bacteremia (as measured by Apache III and Pitt bacteremia score), MRSA infection, and presence of atrioventricular block on electrocardiogram. Patients with S. aureus bacteremia who have community acquisition of infection, underlying valvular heart disease, intravenous drug use, unknown portal of entry, history of prior endocarditis, and possibly, nonwhite race should undergo echocardiography to screen for the presence of endocarditis. We recommend that blood cultures be repeated 3 days following initiation of antistaphylococcal antibiotic therapy in all patients with S. aureus bacteremia. Positive blood cultures at 3 days may prove to be a useful marker in promoting more aggressive management, including more potent antibiotic therapy and surgical resection of the valve in endocarditis cases. MRSA as the infecting organism should be added to the list of risk factors for consideration of valvular resection in cases of endocarditis.

Persistent methicillin-resistant Staphylococcus aureus bacteremia due to a prostatic abscess

This report describes a patient with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia secondary to a prostatic abscess. The literature describing complications of S. aureus bacteremia and the bacteriology of prostatic abscesses is reviewed. This was found to be the first report of a patient with persistent MRSA bacteremia maintained by a prostatic focus.

Risk factors for metastatic infection in patients with Staphylococcus aureus bacteremia with and without endocarditis

Background: Staphylococcus aureus bacteremia (SAB) may be complicated by endocarditis or metastatic infection without evidence of endocarditis (MIWE). The aim of this study was to identify risk factors for MIWE and endocarditis in patients with SAB. METHODS: We performed a retrospective chart review to compare characteristics of patients with uncomplicated SAB and patients whose SAB course was complicated by MIWE or endocarditis. We reviewed the charts of patients with SAB diagnosed in our department from 1992 to 1999 for S. aureus portal of entry, secondary foci of infection, underlying conditions, previous valvular defects, and foreign material. Endocarditis was defined according to the Duke criteria. Patients were classified as having MIWE when the diagnosis of endocarditis was not definite according to the Duke criteria and when there was evidence of at least one secondary metastatic infection other than endocarditis. RESULTS: Some 109 patients had 111 episodes of SAB. Sixty-three patients had no evidence of metastatic infection and constituted the control group. Twenty-seven patients developed at least one episode of MIWE. A community-acquired SAB (CI 95% OR: 1.4-12.3, P<0.02), two or fewer underlying conditions (CI 95% OR: 1.2-83, P<0.04), and a non-severe portal of entry (CI 95% OR: 1.2-20, P<0.03) were independently predictive for MIWE. The characteristics of 21 patients with endocarditis were compared with those of the control group. Only a previous valvular defect was significantly associated with endocarditis. CONCLUSION: A previous valvular defect seems to be an important factor for developing endocarditis during SAB. Risk factors for having MIWE may differ from those found for patients with endocarditis.

Staphylococcus aureus bacteremic pneumonia: differences between community and nosocomial acquisition

OBJECTIVE

The aim of the study was to ascertain the clinical and epidemiologic characteristics of patients with nosocomial or community-acquired Staphylococcus aureus bacteremic pneumonia.

METHODS

A prospective study of 134 cases diagnosed between January 1990 and December 1995 was performed.

RESULTS

Fifty cases involved primary bacteremic pneumonias, of which 80% were nosocomial (the majority, 72%, in intensive care unit patients, of whom 57% were post-surgery). Of the 84 cases of secondary pneumonia, 36 were non-intravenous drug users (78% nosocomial, of whom 43% were in the intensive care unit), and 48 cases were intravenous drug users (98% community-acquired).

CONCLUSIONS

Nosocomial S. aureus bacteremic pneumonia was especially frequent in intensive care unit patients (68.1%), and community-acquired pneumonia in intravenous drug users (72.3%). In non-intravenous drug users, clinical outcome and mortality were similar for nosocomial and community-acquired pneumonia.

Staphylococcus aureus bacteremia and endocarditis

Staphylococcus aureus is a leading cause of bacteremia and endocarditis. Over the past several years, the frequency of S aureus bacteremia (SAB) has increased dramatically. This increasing frequency, coupled with increasing rates of antibiotic resistance, has renewed interest in this serious, common infection. S aureus is a unique pathogen because of its virulent properties, its protean manifestations, and its ability to cause endocarditis on architecturally normal cardiac valves. Although the possibility of underlying endocarditis arises in virtually every patient with SAB, only a minority of bacteremic patients will actually have cardiac involvement. Distinguishing patients with S aureus infective endocarditis (IE) from those with uncomplicated SAB is essential, but often difficult. In this review, the authors summarize recent changes in the epidemiology of SAB and IE, discuss the challenges in distinguishing SAB from IE, and discuss current trends in the management of patients with SAB and IE.