Staphylococcus Aureus Bacteremia Cases Research Articles

Time to blood culture positivity in Staphylococcus aureus bacteremia: Association with 30-day mortality

Time to blood culture positivity (TTP) has been suggested as a prognostic factor for adverse clinical outcome. This study describes the relationship between TTP and clinical outcome in all patients with Staphylococcus aureus bacteremia (SAB) in a large Canadian health region. We performed a retrospective study of all first episodes of SAB occurring in the former Calgary Health Region (population approximately 1.2 million) from July 1, 2006 to December 31, 2008. Overall, 684 cases of SAB were evaluated. The median TTP was 16 h and 31/684 (5%) cases had TTP at >48 h. Time to positivity was shorter for methicillin-susceptible Staphylococcus aureus compared with methicillin-resistant S. aureus (MRSA) and for endovascular sources compared with other sources of infection. The overall 30-day case-fatality rate was 18% (124/684). Patients with delayed TTP (>48 h) suffered the highest case-fatality rate (39%) compared to those with earlier TTP (17%; P = 0.002). Multivariable logistic regression modeling showed that age, nosocomial acquisition, MRSA, focus of infection, liver disease, and TTP < or =12 and >48 h were associated with 30-day mortality. Although uncommon, delayed TTP may be associated with increased mortality. Empiric antimicrobial therapy should continue beyond 48 h in patients at high risk for SAB.

Clinical and Microbiological Determinants of Outcome inStaphylococcus aureusBacteraemia

Staphylococcus aureus bacteraemia (SAB) is commonly complicated by metastatic infection or relapse after treatment. Objectives. The study aim was to determine the role of bacterial, host, and management factors in development of complicated SAB. Methods. A prospectively-conducted observational study gathered data on predisposition, management and outcome of 100 consecutive SAB cases. Antibiotic susceptibilities and genetic lineage of bacterial isolates were determined. Further clinical and microbiological data were gathered on two retrospective series from 1999–2000 (n = 57) and 2004 (n = 116). Results. In the prospective cases, 27% met our definition of complicated disease. Expressed as RR and 95% CI, complicated disease was associated with diabetes (1.58, 1.00–2.48), injecting-drug use (5.48, 0.88–33.49), community-onset of symptoms (1.4, 1.02–1.92), and symptom duration ≥48 hours prior to starting effective antibiotic therapy (2.10, 1.22–3.61). Uncomplicated disease was associated with the presence of a central line (0.69, 0.55–0.88) and prompt removal of a primary focus (0.71, 0.57–0.90). Neither methicillin resistance nor genetic lineage was associated with complicated disease, but methicillin resistance was associated with higher mortality. Conclusions. This study demonstrates that clinical rather than microbial factors are the major determinants of SAB outcome and underscores the importance of early treatment.

Risk Factors for Late Staphylococcus Aureus Bacteremia after Allogeneic Hematopoietic Stem Cell Transplantation: A Single-Institution, Nested Case-Controlled Study

We report on the incidence, risk factors, and outcome of late Staphylococcus aureus bacteremia (SAB) in a cohort of 709 adult and pediatric patients at Memorial Sloan-Kettering Cancer Center between September 1999 and December 2006. The SAB cases were identified by prospective surveillance and examination of a computerized database. Late SAB was defined as SAB occurring > 50 days post-hematopoietic stem cell transplantation (HSCT). A nested case-controlled study was conducted to identify predictors of late SAB. The incidence of late SAB was 6/100,000 patient-days. The median time from stem cell infusion to incident blood culture was 137 days (range, 55 to 581 days). Eighty-four percent of the cases were community acquired; 40% involved a focal infection. Bacteremia was persistent (>3 days) despite removal of endovascular access in > 50% of cases. Risk factors for late SAB were acute graft-versus-host disease (aGVHD) flare, acute or chronic skin GVHD (cGVHD), corticosteroid use, liver dysfunction, and prolonged hospital length of stay (LOS) post-HSCT. In multivariate models, skin GVHD ( P = .002) and LOS ( P = .02) remained significant. The median survival post-SAB was 135 days (range, 1 to 1765 days). Late SAB occurred mainly in the setting of GVHD or corticosteroid therapy. Clinical manifestations were highly variable. Multiple comorbidities, indicated by organ dysfunction and hospitalization, likely contributed to persistence and increased morbidity and mortality. We recommend a high index of suspicion and empiric antistaphylococcal treatment pending culture results in high-risk patients undergoing HSCT.

Staphylococcus aureusBacteremia, Europe

To the Editor: In their article, Collignon et al. (1) present a table comparing absolute numbers and incidence rates of Staphylococcus aureus bacteremia (SAB) in Australia to those of 5 other countries, and state that data are available from other countries for comparison and 2 countries, Denmark and England, appeared to have comprehensive collection systems. We would like to add data from the European Antimicrobial Resistance Surveillance System (EARSS) to their table. EARSS is a multinational surveillance system that links national networks by collecting comparable and validated data on the prevalence of antimicrobial resistance of 5 microorganisms, including S. aureus (2). A total of 30 countries participate in EARSS. To ensure representativeness of the data it publishes, EARSS has set criteria, which can be found elsewhere (3). In 2003, through a questionnaire, we collected background information on all hospitals served by laboratories participating in EARSS, including the estimated hospitals' catchment populations. Proportion of the country population covered by EARSS was then calculated by dividing the sum of catchment populations by the total population of the country (4). Catchment populations of hospitals providing single specialty or supra-regional type of care were not counted to avoid overlap with other hospitals within the same country. Only the countries that provided denominator data for at least 60% of the isolates were included to ensure that the sample of hospitals was still representative of the country as a whole. The number of SAB and the incidence of SAB per 100,000 inhabitants in 2003 were calculated from EARSS data, adjusted for population coverage, and are presented in the Table. These are crude estimates of the true number of SAB and should, thus, be interpreted with caution. For example, we assumed that the isolates for which hospital background information was not available did not differ from isolates for which we had this information, and that hospitals that participated in EARSS in 2003 were a representative sample of the countries' hospitals. Additionally, the incidence of SAB was positively correlated with the blood culturing rate (Spearman r = 0.74, p = 0.002), which means that the incidence of SAB is likely to have been underestimated in countries that reported few blood cultures. Although some countries did not report their blood culturing rate, the incidences of SAB in these countries were among the highest and are unlikely to be underestimated. For example, the EARSS data for Denmark and Ireland nicely fitted those presented in Table 4 of the article by Collignon et al. (1). Finally, reporting to the EARSS system greatly improved over the years, which is why this study was performed on the last available year, 2003. Nevertheless, one cannot exclude underreporting of SAB by EARSS participating hospitals since EARSS is a voluntary reporting system. For example, England reported 18,403 SAB cases or an incidence of 37 SAB per 100,000 inhabitants from April 2002 to March 2003 through its mandatory surveillance scheme (5), whereas an estimate for the United Kingdom from the EARSS database would only give 7,800 SAB cases for 2003. However, it is impossible to determine whether this discrepancy was due to poor voluntary reporting of SAB cases, a lower blood culturing rate in EARSS participating hospitals, or a poorly representative sample of the country's hospitals. Data from the United Kingdom were excluded from the present study on the basis of the latter possibility; denominator information for <60% of the isolates was available. Table Absolute numbers, rates of Staphylococcus aureus bacteremia (SAB), and percentage of methicillin-resistant Staphylococcus aureus (MRSA), European Antimicrobial Resistance Surveillance System (EARSS), 2003* In conclusion, EARSS is the first comprehensive surveillance system on antimicrobial resistance in Europe. Within certain limitations, EARSS can also provide valuable information on blood-culturing practices and the incidence of SAB in Europe. The system is continuously being improved, and additional information on the representativeness of EARSS data is being collected. This will allow us to improve the quality and accuracy of the reported incidence rates. In the future, the system should allow reporting of similar data for an even larger number of European countries and for additional microorganisms, such as Escherichia coli.

Staphylococcus aureusBacteremia, Australia

Staphylococcus aureus bacteremia (SAB) is common and increasing worldwide. A retrospective review was undertaken to quantify the number of cases, their place of acquisition, and the proportions caused by methicillin-resistant S. aureus (MRSA) in 17 hospitals in Australia. Of 3,192 episodes, 1,571 (49%) were community onset. MRSA caused 40% of hospital-onset episodes and 12% of community-onset episodes. The median rate of SAB was 1.48/1,000 admissions (range 0.61-3.24; median rate for hospital-onset SAB was 0.7/1,000 and for community onset 0.8/1,000 admissions). Using these rates, we estimate that approximately 6,900 episodes of SAB occur annually in Australia (35/100,000 population). SAB is common, and a substantial proportion of cases may be preventable. The epidemiology is evolving, with >10% of community-onset SAB now caused by MRSA. This is an emerging infectious disease concern and is likely to impact on empiric antimicrobial drug prescribing in suspected cases of SAB.

Pelvic floor dyssynergia (PFD): subgroups defined by different methods of balloon expulsion and defecation index

Staphylococcus aureus bacteremia (SAB) is usually monomicrobial (M-SAB). We reviewed SAB in adults (≥18 years old) over a 13 year-period and compared polymicrobial (P-SAB) and M-SAB. We encountered 93 P-SAB among 1537 SAB cases (6.1%). The source distribution was comparable; however, source-specified differences were apparent. P-SAB was noted in 12/58 (20.7%) necrotizing soft tissue infections/sacral decubiti and foot gangrene vs. 1/122 (0.8%) cellulitis/abscesses (P < 0.001), in 7/64 (10.9%) femoral intravascular catheters (IVC) vs.16/376 (4.3%) IVC in other sites (P = 0.03) and 15/134 (11.2%) healthcare-associated pneumonia (HAP) vs. 1/33 (3.0%) community-associated cases (P = 0.1). Methicillin-resistance frequency was similar but community-associated SCCmec types (IV/V) were infrequent (17.9% vs. 34.2%; P = 0.04). P-SAB was associated with higher mortality (50.5% vs. 24.2%; P < 0.001) across nearly all sources. In summary, P-SAB is infrequent, usually encountered in necrotizing soft tissue infections/decubiti, femoral IVC and possibly HAP. The actual incidence of S. aureus in these infections should be defined.

Epidemiology of Staphylococcus aureus bacteremia in Denmark from 1957 to 1990.

OBJECTIVE: To investigate the changes in epidemiology of Staphylococcus aureus (SA) bacteremia in Denmark over a 30-year period, where the population has remained stable. METHODS: Bacteriologic and clinical data were generated on 17 712 SA strains from virtually all SA bacteremia cases in Denmark from 1957 to 1990 submitted to our laboratory for phage typing. The data were related to information about population, hospital activity and blood-culturing activity during that period. RESULTS: SA bacteremia cases increased from 3 to 20/100 000 inhabitants per year, with the largest increases in incidence rates for the <1-year and >50-year age groups. While blood-culturing activity increased three-fold during the period, the rate of SA bacteremias actually decreased relative to the number of blood cultures taken. The increase in SA bacteremia cases was mainly due to increases in nosocomial infections for all age groups and was related to the increasing admission rates to Danish hospitals. Major shifts in antibiotic resistance patterns and phage types took place during the period, i.e. a marked reduction in multiresistant (including methicillin-resistant) strains, but could not explain the change in the epidemiology of the infections. CONCLUSIONS: The data indicate that increases in SA bacteremia rates correlated significantly with increasing numbers of admissions to hospitals. The main increase in SA bacteremia rates was represented by nosocomial infection, although increasing blood-culturing activity during the period may have contributed.