Secular changes in incidence and mortality associated with Staphylococcus aureus bacteraemia in Quebec, Canada, 1991-2005.

In order to examine secular changes in the incidence and mortality associated with Staphylococcus aureus bacteraemia before and after the emergence of methicillin-resistant S. aureus (MRSA), a retrospective cohort study of 815 patients with S. aureus bacteraemia was performed in the Estrie region of Quebec, Canada, between 1991 and 2005. The primary outcome was all-cause 30-day mortality. Between 1991-1993 and 2003-2005, the proportion of cases attributed to endocarditis and pneumonia increased from 4% to 11% and from 2% to 11%, respectively, while that attributed to catheter infections decreased from 49% to 17%. MRSA was almost absent in 1991-1999, but accounted for 10% and 20% of cases in 2000-2002 and 2003-2005, respectively. The population incidence of bacteraemia caused by methicillin-susceptible S. aureus (MSSA) remained stable between 1997 and 2005, while that of MRSA increased from 0 to 7.4/100 000. Risk-factors for mortality included age, co-morbidities, female gender, residence outside the city of Sherbrooke, pneumonia (OR 3.35, 95% CI 1.96-5.73) or endocarditis (OR 2.89, 95% CI 1.67-5.01) as the source, and an absence of treatment. After adjusting for confounders, patients with MRSA bacteraemia had a higher mortality rate than those with MSSA bacteraemia (OR 2.21, 95% CI 0.99-4.96, p 0.053). Mortality in patients with MSSA bacteraemia was 19% (16/83) in 1991-1993, 23% (26/113) in 1994-1996, 29% (50/173) in 1997-1999, and 28% (52/185) in 2000-2002, decreasing to 15% (28/192) in 2003-2005, which impacted on the relative mortality rates of MRSA and MSSA. MRSA did not replace, but added to, an existing stable incidence of MSSA bacteraemia.     

Secular changes in incidence and mortality associated with Staphylococcus aureus bacteraemia in Quebec, Canada, 1991–2005

In order to examine secular changes in the incidence and mortality associated with Staphylococcus aureus bacteraemia before and after the emergence of methicillin-resistant S. aureus (MRSA), a retrospective cohort study of 815 patients with S. aureus bacteraemia was performed in the Estrie region of Quebec, Canada, between 1991 and 2005. The primary outcome was all-cause 30-day mortality. Between 1991–1993 and 2003–2005, the proportion of cases attributed to endocarditis and pneumonia increased from 4% to 11% and from 2% to 11%, respectively, while that attributed to catheter infections decreased from 49% to 17%. MRSA was almost absent in 1991–1999, but accounted for 10% and 20% of cases in 2000–2002 and 2003–2005, respectively. The population incidence of bacteraemia caused by methicillin-susceptible S. aureus (MSSA) remained stable between 1997 and 2005, while that of MRSA increased from 0 to 7.4/100 000. Risk-factors for mortality included age, co-morbidities, female gender, residence outside the city of Sherbrooke, pneumonia (OR 3.35, 95% CI 1.96–5.73) or endocarditis (OR 2.89, 95% CI 1.67–5.01) as the source, and an absence of treatment. After adjusting for confounders, patients with MRSA bacteraemia had a higher mortality rate than those with MSSA bacteraemia (OR 2.21, 95% CI 0.99–4.96, p 0.053). Mortality in patients with MSSA bacteraemia was 19% (16/83) in 1991–1993, 23% (26/113) in 1994–1996, 29% (50/173) in 1997–1999, and 28% (52/185) in 2000–2002, decreasing to 15% (28/192) in 2003–2005, which impacted on the relative mortality rates of MRSA and MSSA. MRSA did not replace, but added to, an existing stable incidence of MSSA bacteraemia.     

Staphylococcus aureus bacteraemia in Iceland, 1995–2008: changing incidence and mortality

Little is known about temporal changes in the epidemiology of Staphylococcus aureus bacteraemia. The objective of the present study was to analyse changes in the incidence and mortality of adult S. aureus bacteraemia in Iceland. Individuals 18 years or older with a positive blood culture for S. aureus between 1 January 1995 and 31 December 2008 were identified, with the participation of all clinical microbiological laboratories performing blood cultures in Iceland. Infections were categorized as nosocomial, healthcare-associated or community-acquired. National population statistics and dates of death were retrieved from the National Registry. During the study period, 692 individuals from 19 institutions had 721 distinct episodes of S. aureus bacteraemia. The incidence rose from 22.7 to 28.9 per 100 000 per year during the period (p 0.012). Nosocomial infections comprised 46.3% of cases, 14.6% were healthcare-associated, and 39.1% were community-acquired. The proportion of nosocomial infections decreased during the period (p <0.001), whereas an increase was seen in the proportion of community-acquired infections (p <0.001). All-cause 30-day mortality decreased from 25.0% to 8.1% (p 0.001) and 1-year mortality decreased from 37.0% to 27.9% (p 0.061) between the periods 1995–1996 and 2007–2008. Four cases of bacteraemia caused by methicillin-resistant S. aureus were seen (0.6%), none of which was fatal. In conclusion, there was a significant increase in the incidence of S. aureus bacteraemia in Iceland between 1995 and 2008. Concomitantly, there was a significant reduction in mortality, towards one of the lowest reported. Further studies are needed to understand the basis for these changes.     

Virulence factors and phylogenetic grouping of Escherichia coli isolates from patients with bacteraemia of urinary tract origin relate to sex and hospital- vs. community-acquired origin

Worldwide, Escherichia coli is a leading cause of bloodstream infections. Bacteraemia cases in both community- and hospital-acquired infections are often due to E. coli, and it is a major cause of mortality from these infections. These invasive infections are primarily due to extraintestinal pathogenic E. coli (ExPEC), possessing a variety of virulence factors (VFs). The pathogenesis of E. coli bloodstream infections is largely unknown, which is why preventive measures are lacking. We studied 196 epidemiologically and clinically well-characterized E. coli isolates from patients with bacteraemia of urinary tract origin according to virulence-associated genes (VAGs), phylogroups, and antimicrobial resistance, and the relation of these factors to hospital- vs. community-acquired origin, sex, and mortality. We found papAH to be associated with community-acquired (CA) rather than hospital-acquired (HA) episodes, and kpsM II and hlyD to be associated with HA rather than CA episodes. papAH and iss were associated with females, and iroN with males. Phylogroup D was associated with females. None of the variables was found to be related to mortality. This study provides new insights into the relationships between the epidemiology and pathogenesis of E. coli bacteraemia of urinary tract origin.     

Secular trends in incidence and mortality of bacteraemia in a Danish county 1981-1994

We estimated the incidence and mortality of bacteraemia in the County of North Jutland and examined factors that could explain the changes observed. A population-based survey of bacteraemia was conducted in the Danish County of North Jutland during 1981-1994. Data were retrieved from a regional bacteraemia register. The mortality was determined through linkage to the Danish Civil Registration System. A total of 7198 bacteraemias were detected, and the annual incidence increased from 76 per 100,000 person-years in 1981 to 153 in 1994. One major determining factor was a change in blood culture system with a higher volume of blood per sample, but annual numbers of blood cultures also increased. The 30-day mortality rate increased from 17 to 40 per 100,000 person-years during the study period, whereas the case-fatality rate remained constant (23.6%; 95% confidence intervals 22.6%-24.6%). The number of bacteraemias increased significantly. This observation could be explained only partly by changes in demography, in blood culture system, and in diagnostic activity. The case fatality rate remained constant despite the fact that more people were diagnosed with bacteraemia; this indicates that, with recent blood culture practice, more clinically significant bacteraemias are diagnosed.     

Risk factors and mortality of healthcare-associated and community-acquired Staphylococcus aureus bacteraemia

Staphylococcus aureus bacteraemia (SAB) is a leading cause of mortality and morbidity in both nosocomial and community settings. The objective of the study is to explore epidemiological characteristics and predisposing risk factors associated with healthcare-associated (HCA) and community-acquired (CA) SAB, and to evaluate any differences in mortality and efficacy of initial antimicrobial therapy on treatment outcome. We conducted a two-part analysis. First, a triple case-control study in which groups of HCA SAB with onset ≥ 48 h after hospital admission (HCA ≥ 48 h), HCA SAB with onset <48 h of hospital admission (HCA <48 h), and CA SAB were compared with controls. Second, a cohort study including all patients with SAB was performed to identify factors associated with in-hospital mortality. SAB was diagnosed in 165 patients over the study period (January 2007 to December 2007). Five variables were independently associated with HCA ≥ 48 h SAB: presence of central venous catheter, solid tumour, chronic renal failure, previous hospitalization and previous antibiotic therapy. Significant risk factors for HCA <48 h SAB were: Charlson Comorbidity Index ≥ 3, previous hospitalization, living in long-term care facilities and corticosteroid therapy. Factors independently associated with CA SAB were: diabetes mellitus, HIV infection and chronic live disease. Patients with HCA <48 h SAB were significantly more likely to receive initial inadequate antimicrobial treatment than patients with CA or HCA ≥ 48 h SAB (44.8% versus 33.3% and 31.5%, respectively). Logistic-regression analysis identified three variables as independent predictors of mortality: presentation with septic shock, infection with methicillin-resistant S. aureus, and initial inadequate antimicrobial treatment. More than half of patients with SAB have MRSA strains and presentation with septic shock, and inappropriate empirical therapy was associated with increased mortality.     

Trends in MRSA in England and Wales: analysis of morbidity and mortality data for 1993-2002

This article examines trends in infection and mortality from methicillin-resistant Staphylococcus aureus (MRSA) over the period 1993 to 2002. Trends in the number of deaths where MRSA was mentioned on the death certificate were compared with national reporting of microbiologically-confirmed bacteraemia to the Health Protection Agency Communicable Disease Surveillance Centre (CDSC). Alongside national trends, patterns in the place of death were examined. Both the number of deaths and number of laboratory reports increased substantially over the period examined. MRSA mortality rates increased over 15-fold during the period 1993 to 2002. Reporting rates for bacteraemia increased 24-fold.     

Risk of bacteraemia and mortality in patients with haematological malignancies

This study examined the association between type of haematological malignancy, risk of bacteraemia and risk of mortality, with emphasis on the impact of bacteraemia type on mortality. A population-based cohort design was used, and all patients aged > or = 15 years with an incident haematological malignancy who were living in North Jutland County, Denmark, during 1992-2002 were included in the study. Among 1666 patients with an incident haematological malignancy, 358 (21%) suffered an episode of bacteraemia during a median follow-up period of 1.1 years (quartile 0.2-3.4) from the date of cancer diagnosis (overall incidence rate of 96/1000 person-years). In comparison to Hodgkin's disease, adjusted incidence rate ratios (IRRs) were 23.3 (95% CI, 10.0-54.5) for acute myeloid leukaemia, 3.8 (95% CI, 1.5-9.3) for multiple myeloma, and 2.2 (95% CI, 0.9-5.1) for non-Hodgkin's lymphoma or chronic lymphatic leukaemia. Overall cumulative 30-day mortality was 32% (95% CI, 27-37), and 90-day mortality was 50% (95% CI, 44-55). In comparison with acute myeloid leukaemia, adjusted mortality rate ratios (MRRs) were close to 1.0 for other haematological malignancies. In comparison to bacteraemia caused by Gram-positive bacteria, adjusted MRRs were 1.0 (95% CI, 0.6-1.5) for Gram-negative bacteraemia, and 1.9 (95% CI, 1.1-3.3) for polymicrobial bacteraemia or fungaemia. Thus, the risk of bacteraemia varied greatly according to the type of malignancy, while mortality rates were similar for these diseases, although dependent on the type of bacteraemia. Polymicrobial bacteraemia or fungaemia was associated with higher mortality.     

Incidence and mortality of hospital-acquired bacteraemia: a population-based cohort study applying a multi-state model approach

ObjectiveThe effect of hospital-acquired bacteraemia on mortality is sparsely investigated. We investigated the incidence and hospital-acquired bacteraemia impact on mortality.MethodsWe conducted a 13-year population-based cohort study using the North Denmark Bacteraemia Research Database and Danish health registries. The population comprised all adult patients with a hospital admission lasting ≥48 hr. We used Poisson regression to estimate trends in incidence. The 30-day mortality of hospital-acquired bacteraemia was estimated using an illness-death multistate model with recovery using the population at risk of hospital-acquired bacteraemia as reference.ResultsWe identified 3588 episodes of hospital-acquired bacteraemia in 484 264 admissions. The incidence increased proportionally by 1.02 episodes yearly (95% CI 1.01–1.03) between 2006 and 2018. Hospital-acquired bacteraemia was associated with increased mortality (adjusted hazard ratio (aHR) 4.32, 95% CI 3.95–4.72), especially hospital-acquired bacteraemia with unknown source (aHR 6.42 (95% CI 5.67–7.26), “thoracic incl. pneumonia” (aHR 5.89, 95% CI 3.45–10.12) and abdominal source (aHR 4.33, 95% CI 3.27–5.74). The relative impact on mortality diminished with age (aHR 5.66, 95% CI 2.00–16.01 in 18–40 years old vs. 3.69, 95% CI 3.14–4.32 in 81–105 years old) and comorbidity (aHR 5.75, 95% CI 4.45–7.42 in low vs. 3.55, 95% CI 3.16–3.98 in high comorbidity), and was higher in elective admissions (aHR 9.09, 95% CI 7.14–11.57 vs. aHR of 4.03, 95% CI 3.67–4.42).DiscussionHospital-acquired bacteraemia is associated with high mortality, especially when the source is unknown or originating from the thoracic cavity.     

Healthcare-associated,community-acquired and hospital-acquired bacteraemic urinary tract infections in hospitalized patients: a prospective multicentre cohort study in the era of antimicrobial resistance

The clinical and microbiological characteristics of community-onset healthcare-associated (HCA) bacteraemia of urinary source are not well defined. We conducted a prospective cohort study at eight tertiary-care hospitals in Spain, from October 2010 to June 2011. All consecutive adult patients hospitalized with bacteraemic urinary tract infection (BUTI) were included. HCA-BUTI episodes were compared with community-acquired (CA) and hospital-acquired (HA) BUTI. A logistic regression analysis was performed to identify 30-day mortality risk factors. We included 667 episodes of BUTI (246 HCA, 279 CA and 142 HA). Differences between HCA-BUTI and CA-BUTI were female gender (40% vs 69%, p <0.001), McCabe score II–III (48% vs 14%, p <0.001), Pitt score ≥2 (40% vs 31%, p 0.03), isolation of extended spectrum β-lactamase-producing Enterobacteriaciae (13% vs 5%, p <0.001), median hospital stay (9 vs 7 days, p 0.03), inappropriate empirical antimicrobial therapy (21% vs 13%, p 0.02) and mortality (11.4% vs 3.9%, p 0.001). Pseudomonas aeruginosa was more frequently isolated in HA-BUTI (16%) than in HCA-BUTI (4%, p <0.001). Independent factors for mortality were age (OR 1.04; 95% CI 1.01–1.07), McCabe score II–III (OR 3.2; 95% CI 1.8–5.5), Pitt score ≥ 2 (OR 3.2 (1.8–5.5) and HA-BUTI OR 3.4 (1.2–9.0)). Patients with HCA-BUTI are a specific group with significant clinical and microbiological differences from patients with CA-BUTI, and some similarities with patients with HA-BUTI. Mortality was associated with patient condition, the severity of infection and hospital acquisition.     

Putative link between Staphylococcus aureus bacteriophage serotype and community association

Methicillin-resistant Staphylococcus aureus (MRSA) from humans can be broadly separated into 3 groups: healthcare-associated (HA), community-associated (CA), and livestock-associated (LA) MRSA. Initially based on epidemiological features, division into these classes is becoming increasingly problematic. The sequencing of S. aureus genomes has highlighted variations in their accessory components, which likely account for differences in pathogenicity and epidemicity. In particular, temperate bacteriophages have been regarded as key players in bacterial pathogenesis. Bacteriophage-associated Panton-Valentine leukocidin genes (luk-PV) are regarded as epidemiological markers of the CA-MRSA due to their high prevalence in CA strains. This paper describes the development and application of a partial composite S. aureus virulence-associated gene microarray. Epidemic, pandemic, and sporadic lineages of UK HA and CA S. aureus were compared. Phage structural genes linked with CA isolates were identified and in silico analysis revealed these to be correlated with phage serogroup. CA strains predominantly carried a PVL-associated phage either of the A or Fb serogroup, whilst HA strains predominantly carried serogroup Fa or B phages. We speculate that carriage of a serogroup A/Fb PVL-associated phage rather than the luk-PV genes specifically is correlated with CA status.     

Positive follow-up blood cultures identify high mortality risk among patients with Gram-negative bacteraemia

ObjectivesThe role of follow-up blood cultures (FUBCs) in the management of Gram-negative bacteraemia (GNB) is poorly understood. We aimed to determine the utility of FUBCs in identifying patients with increased mortality risk.MethodsAn observational study with a prospectively enrolled cohort of adult inpatients with GNB was conducted at Duke University Health System from 2002 to 2015. FUBCs were defined as blood cultures performed from 24 hours to 7 days from initial positive blood culture.ResultsAmong 1702 patients with GNB, 1164 (68%) had FUBCs performed. When performed, FUBCs were positive in 20% (228/1113) of cases. FUBC acquisition was associated with lower all-cause in-hospital mortality (108/538, 20%, vs. 176/1164, 15%; p 0.01) and attributable in-hospital mortality (78/538, 15%, vs. 98/1164, 8%; p < 0.0001). Propensity score–weighted Cox proportional hazards models revealed that obtaining FUBCs was associated with reductions in all-cause (hazard ratio (HR) 0.629; 95% confidence interval (CI), 0.511–0.772; p < 0.0001) and attributable mortality (HR 0.628; 95% CI, 0.480–0.820; p 0.0007). Positive FUBCs were associated with increased all-cause mortality (49/228, 21%, vs. 110/885, 11%; p 0.0005) and attributable mortality (27/228, 12%, vs. 61/885, 7%; p 0.01) relative to negative FUBCs. Propensity score–weighted Cox proportional hazards models revealed that positive FUBCs were associated with increased all-cause (HR 2.099; 95% CI, 1.567–2.811; p < 0.0001) and attributable mortality (HR 1.800; 95% CI, 1.245–2.603; p 0.002). In a calibration analysis, a scoring system accurately identified patients at high risk of positive FUBCs.ConclusionsRates of positive FUBCs were high and identified patients at increased risk for mortality. Clinical variables can identify patients at high risk for positive FUBCs. FUBCs should be considered in the management of GNB.     

Incidence of and risk factors for clinically significant methicillin-resistant Staphylococcus aureus infection in a cohort of HIV-infected adults

OBJECTIVES: Outbreaks of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) have been noted in multiple sites in the United States. This study's purpose was to estimate trends in the incidence of and risk factors for clinically significant MRSA (CS-MRSA) infection in a cohort of HIV-infected adults. DESIGN: A retrospective clinic-based cohort (January 1, 2000-December 31, 2003) study. METHODS: We ascertained all initial episodes of CS-MRSA and categorized them by primary site. Incidence rates were estimated by half year. Risk factors for CA-MRSA infection were identified using Cox modeling. RESULTS: Of 126 potential events, 94 were CS. Their primary sources were 83% skin or soft tissue, 10% blood, 6% respiratory, and 1.0% other sites. Among these, 60% were CA and 40% were nosocomial. Of antibiotics tested, only cotrimoxazole resistance was associated with nosocomial acquisition. The 3455 patients contributed 7003 person-years at risk. The incidence of CS-MRSA infection increased 6.2-fold from the first to the last half year. In multivariate analysis, independent predictors of CA-MRSA infection included HIV transmission by men who have sex with men or by injection drug use, CD4 count <50 cells/muL, log10 HIV plasma viral load, and absence of cotrimoxazole prophylaxis. CONCLUSIONS: The incidence of initial CS-MRSA events increased more than 6-fold in a 4-year period. The associations between CA-MRSA infection and HIV severity indicators merit examination in other cohorts.     

How I manage a patient with MRSA bacteraemia

BackgroundStaphylococcus aureus bloodstream infections are common and associated with a high mortality of 15–25%. Methicillin-resistant S. aureus (MRSA) bloodstream infection accounts for 10–40% of cases, and has an even higher mortality. Despite being the ‘bread and butter’ of clinical infectious diseases practice, robust evidence to guide optimal management is often lacking and there is wide variation in practice.ObjectivesTo provide a real-world example of a case of MRSA bacteraemia and the thought processes of the authors as key management decision points are reached.SourcesThe discussion is based on recent literature searches of relevant topics. In making recommendations, randomized clinical trial data have been prioritized and highlighted, and where these are not available recommendations are based on the experience and opinions of the authors.ContentFor a patient with MRSA bacteraemia and a primary bone and joint infection the following points are discussed: empirical antibiotic choice for suspected S. aureus bacteraemia; directed antibiotic choice for MRSA; monitoring and dosing of vancomycin; the role of combination therapy when bacteraemia is persistent; and the duration of therapy and role of switching to oral antibiotics.ImplicationsWhile broad principles of aggressive source control and appropriate choice and duration of antibiotics are important, the heterogeneity of S. aureus bacteraemia means that a tailored rather than algorithmic approach to management is often required. Further randomized controlled trials are needed to strengthen the evidence base for the management of MRSA bacteraemia.     

Incidence,clinical characteristics and 30-day mortality of enterococcal bacteraemia in Denmark 2006–2009: a population-based cohort study

Enterococci currently account for approximately 10% of all bacteraemias, reflecting remarkable changes in their epidemiology. However, population-based data of enterococcal bacteraemia are scarce. A population-based cohort study comprised all patients with a first episode of Enterococcus faecalis or Enterococcus faecium bacteraemia in two Danish regions during 2006–2009. We used data collected prospectively during clinical microbiological counselling and hospital registry data. We determined the incidence of mono- and polymicrobial bacteraemia and assessed clinical and microbiological characteristics as predictors of 30-day mortality in monomicrobial bacteraemia by logistic regression analysis. We identified 1145 bacteraemic patients, 700 (61%) of whom had monomicrobial bacteraemia. The incidence was 19.6/100 000 person-years (13.0/100 000 person-years for E. faecalis and 6.6/100 000 person-years for E. faecium). The majority of bacteraemias were hospital-acquired (E. faecalis, 45.7%; E. faecium, 85.2%). Urinary tract and intra-abdominal infections were the predominant foci for the two species, respectively. Infective endocarditis (IE) accounted for 25% of patients with community-acquired E. faecalis bacteraemia. Thirty-day mortality was 21.4% in patients with E. faecalis and 34.6% in patients with E. faecium. Predictors of 30-day mortality included age, co-morbidity and hospital-acquired bacteraemia. In addition, intra-abdominal infection, unknown focus and high-level gentamicin resistance were predictors of mortality in E. faecalis patients. E. faecium was associated with increased risk of mortality compared with E. faecalis. The study emphasizes the importance of enterococci both in terms of incidence and prognosis. The frequency of IE in patients with E. faecalis bacteraemia emphasizes the importance of echocardiography, especially in community-acquired cases.     

Clostridium bacteraemia characterised by 16S ribosomal RNA gene sequencing

BACKGROUND: Owing to problems in accurate species identification of the diverse genus clostridium, the epidemiology and pathogenicity of many species are not fully understood. Moreover, previous studies on clostridium bacteraemia have been limited and relied only on phenotypic species identification. AIMS: To characterise the epidemiology, disease spectrum, and outcome of clostridium bacteraemia using 16S ribosomal RNA (rRNA) gene sequencing. METHOD: During a four year period (1998-2001), all cases of clostridium bacteraemia were prospectively studied and all "non-perfringens" clostridium isolates identified to the species level by 16S rRNA gene sequencing. RESULTS: Fifty one blood culture isolates were identified as Clostridium perfringens and 17 belonged to 11 other clostridium species. The first case of C disporicum infection and two cases of clostridium bacteraemia in children with intussusception were also described. Of the 68 clostridium isolates from 68 different patients, 38 were associated with clinically relevant bacteraemia. The gastrointestinal and hepatobiliary tracts were common sites of both underlying disease and portal of entry in these patients. Clostridium perfringens accounted for 79% of all clinically relevant bacteraemia, with the remainder caused by a diversity of species. The attributable mortality rate of clinically relevant clostridium bacteraemia was 29%. Younger age and underlying gastrointestinal/hepatobiliary tract disease were associated with mortality (p < 0.05). CONCLUSIONS: Patients with clinically relevant clostridium bacteraemia should be investigated for the presence of underlying disease processes in the gastrointestinal or hepatobiliary tracts. 16S rRNA gene analysis will continue to be useful in further understanding the pathogenicity of various clostridium species.     

A hospital-wide outbreak of septicemia due to a few strains of Staphylococcus aureus

During a 6-month period at Walter Reed Army Hospital the monthly attack rate of Staphylococcus aureus bacteremia increased to 3.8 +/- 0.5 (mean +/- SEM) from 2.5 +/- 0.2 cases per 1,000 dispositions for the previous 48 months (P less than 0.05). A predominant phage pattern, designated S, was found in 12 (39%) of 31 bacteremic isolates typed and another strain, delta, was associated with four catheter-related infections. Two other strains also accounted for infections. Patients with isolates of the S phage pattern had a higher mortality (59%) than patients with non-S isolates (37%). Thirty-eight per cent of S. aureus carriers among hospital personnel harbored S or delta strains. Limitation of intravascular devices, strict handwashing, and the use of gloves were associated with a significant decrease in the incidence of S. aureus bacteremia to 1.9 +/- 0.5/1,000 dispositions over the next 6 months (P less than 0.05). S and delta strains were reduced to 20% of these isolates despite their persistence in 32% of staphylococcal carriers upon reculture of personnel. We conclude that S. aureus persists as an important pathogen in the hospitals, and that phage typing S. aureus isolates remains an important tool in hospital epidemiology. The presence of multiple S. aureus strains causing this outbreak and the extent of their dissemination among patients and personnel reported here emphasizes the need to reevaluate strategies of nosocomial staphylococcal control.     

Clinical and molecular epidemiology of community-acquired, healthcare-associated and nosocomial methicillin-resistant Staphylococus aureus in Spain

A prospective cohort study including all new cases of methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection in 64 Spanish hospitals during June 2003 was performed to investigate the epidemiology of MRSA in Spain. Only patients who yielded clinical MRSA-positive samples were included. Epidemiological and clinical data for a total of 370 cases were collected. Genotyping was performed using pulsed-field gel electrophoresis and multilocus sequence typing. Panton–Valentine leukocidin genes and the staphylococcal chromosomal cassette mec (SCC mec ) were identified in representative isolates. MRSA was considered to be nosocomially acquired in 202 cases (55%), healthcare-associated (HCA) in 139 cases (38%), community-acquired (CA) in three cases, and of uncertain mode of acquisition in 26 (7%) cases. The pooled population-based rate was 2.31 cases/100 000 population/month, and the pooled nosocomial rate was 0.21 cases/1000 hospital stays (20.2% of S. aureus ). Peripheral vascular disease, respiratory tract infections, catheter infections, bloodstream infections and crude mortality were more frequent among HCA cases, whereas neoplasia and urinary tract infections were more frequent among nosocomially acquired cases. Two clones related to the paediatric clone ST5-IV accounted for 71% of the isolates; EMRSA-16 has emerged in two different geographical areas. Only one isolate belonged to the formerly predominant Iberian clone. The three CA isolates were related to the USA300 clone. SCC mec type IV was the most frequent type in nosocomial and HCA isolates. The epidemiology of MRSA has changed in Spain; outpatients with previous healthcare contact represent a very important reservoir of MRSA, and community isolates are emerging.     

Case fatality ratio and mortality rate trends of community-onset Staphylococcus aureus bacteraemia

Lethal outcomes can be expressed as a case fatality ratio (CFR) or as a mortality rate per 100 000 population per year (MR). Population surveillance for community-onset methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus bacteraemia was conducted in Canada, Australia, Sweden and Denmark to evaluate 30-day CFR and MR trends between 2000 and 2008. The CFR was 20.3% (MSSA 20.2%, MRSA 22.3%) and MR was 3.4 (MSSA 3.1, MRSA 0.3) per 100 000 per year. Although MSSA CFR was stable the MSSA MR increased; MRSA CFR decreased while its MR remained low during the study. Community-onset S. aureus bacteraemia, particularly MSSA, is associated with major disease burden. This study highlights complementary information provided by evaluating both CFR and MR.