The changing epidemiology of Staphylococcus aureus bloodstream infection: a multinational population-based surveillance study

A functionalized surface modification with vanadium nanoparticles of various valences against implant-associated bloodstream infection

Bloodstream infection, especially with implants involved, is an often life-threatening condition with high mortality rates, imposing a heavy burden on patients and medical systems. Herein, we firstly deposited homogeneous vanadium metal, V₂O₃, VO₂, and V₂O₅ nanofilms on quartz glass by magnetron sputtering. Using these platforms, we further investigated the potential antimicrobial efficiency of these nano-VO_x films and the interactions of human erythrocytes and bacteria (methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa) with our samples in a novel cell–bacteria coculture model. It was demonstrated that these nano-VO_x precipitated favorable antibacterial activity on both bacteria, especially on S. aureus, and this effect increased with higher vanadium valence. A possible mechanism accountable for these results might be elevated levels of vanadium-induced intracellular reactive oxygen species. More importantly, based on hemolysis assays, our nano-VO_x films were found to be able to kill prokaryotic cells but were not toxic to mammalian cells, holding the potential for the prevention of implant-related hematogenous infections. As far as we know, this is the first report wherein such nano-VO_x films have assisted human erythrocytes to combat bacteria in a valence-dependent manner. Additionally, vanadium ions were released from these nano-VO_x films in a sustained manner, and low-valence films possessed better biocompatibility with human fibroblasts. This work may provide new insights for biomedical applications of inorganic vanadium compounds and attract growing attention in this field. From the perspective of surface modification and functionalization, this study holds promise to avail the prophylaxis of bloodstream infections involving implantable biomedical devices.

[Antibiotic stewardship and Staphylococcus aureus Bacteremia]

Rates of antibiotic resistance are increasing worldwide and impact on the treatment of patients with bacterial infections. A broad and uncritical application in inpatient and outpatient settings as well as in agriculture has been recognized as the main driving force. Antibiotic stewardship (ABS) programs aim at countering this worrisome development using various direct interventions such as infectious disease counseling. Blood stream infections caused by Staphylococcus (S.) aureus are severe infections associated with high mortality rates. ABS interventions such as de-eskalation of the antibiotic regimen or application of narrow-spectrum beta-lactam antibiotics can significantly reduce mortality rates. In this review, we discuss the importance of ABS programs and infectious disease counseling for the treatment of S. aureus blood stream infection.

Burden of bloodstream infection in an area of Mid-Norway 2002-2013: a prospective population-based observational study

BACKGROUND

Studies from several countries indicate that the incidence and mortality of bloodstream infection (BSI) have been increasing over time.

METHODS

We studied the burden of disease and death related to BSI in a defined geographical area of Mid-Norway, where BSI episodes were prospectively recorded by the same microbiological department during 12 consecutive years. Death from BSI was defined as death within 30 days of BSI detection. Age and sex standardized incidence and mortality rates and case fatality rates were calculated.

RESULTS

Between 2002 and 2013, 1995 episodes of BSI in 1719 patients aged 16 to 99 years were included. The overall incidence of BSI was 215 per 100,000 person-years. The incidence increased exponentially with age, particularly in males. The incidence increased from 205 to 223 per 100,000 person-years from 2002-07 to 2008-13. Escherichia coli was the most frequently isolated infective agent, followed by Streptococcus pneumoniae and Staphylococcus aureus. The rate of S. pneumoniae BSI decreased over time in males (on average by 9.2% annually), but not in females. The total rate of BSI microbes with acquired resistance increased slightly over time, but did not exceed 2 episodes per 100,000 person-years. The mortality of BSI was 32 per 100,000 person-years, higher in males than in females (36 vs. 28 per 100,000 person-years) and was significantly higher in old age, particularly in males. The total BSI mortality was similar in the first and second halves of the study period, but the mortality of S. pneumoniae BSI decreased in males (15.0% annually). The crude case fatality decreased from the first to the second half of the study period (17.2% to 13.1%; p = 0.014). The rate of blood culture sampling increased more than twofold during the study period.

CONCLUSIONS

The mortality of BSI remained stable during 2002-2013. At the same time, BSI incidence increased and case fatality rate decreased, perhaps because an increased rate of blood culture sampling may have led to improved detection of milder BSI episodes. Very low, yet slightly increasing rates of microbes with acquired resistance were observed.

Prognostic impact of hyperglycemia at onset of methicillin-sensitive Staphylococcus aureus bacteraemia

Previous reports have associated hyperglycemia to poor outcome among aged and comorbid Staphylococcus aureus bacteraemia (SAB) patients. However, the prognostic impact of hyperglycemia in SAB irrespective of age and underlying conditions including a diagnosis of diabetes has received little attention. The objective here was to evaluate the prognostic relevance of hyperglycemia at onset of methicillin-sensitive SAB (MS-SAB). It was a retrospective study of MS-SAB patients. Blood glucose was measured within 24 h of positive blood cultures. The patient cohort was analyzed en bloc and by categorization according to age, underlying conditions and a diagnosis of diabetes. Altogether 161 patients were identified. High initial blood glucose levels were observed among diabetics (p < 0.001), patients with deep infections (p < 0.05) and poor outcome at 28- or 90-days (p < 0.05). Receiver operating characteristics presented the glucose cut-off level of 7.2 mmol/L as a significant predictor of mortality with an area under the curve of 0.63 (95% CI 0.52-0.75, p < 0.05). Blood glucose ≥7.2 mmol/L connected to higher 28- (9 vs. 20%, p < 0.05) and 90-day (14 vs. 29%, p < 0.01) mortality. In Cox proportional hazard regression the blood glucose cut-off value of 7.2 mmol/L significantly predicted 90-day mortality (HR, 2.12; 95% CI, 1.01-4.46; p < 0.05). Among young and healthy non-diabetics the negative prognostic impact of high glucose was further accentuated (HR 7.46, p < 0.05). High glucose levels had no prognostic impact among diabetics. Hyperglycemia at SAB onset may associate to poor outcome. The negative prognostic impact is accentuated among young and healthy non-diabetics.

Characteristics of Staphylococcus aureus Bacteraemia and Predictors of Early and Late Mortality

We aimed to describe the characteristics of patients with Staphylococcus aureus bacteremia and to evaluate the risk factors associated with early (7-day) and late (30-day) mortality. We performed an observational study including all consecutive episodes of Staphylococcus aureus bacteremia diagnosed at two Italian university hospitals during 2010–2014. A total of 337 patients were included. Mean age was 69 years (range, 57–78) and 65% were males. Methicillin-resistant S. aureus (MRSA) was identified in 132/337 (39%)cases. Overall 7- and 30-day mortality were 13% and 26%, respectively. Early mortality was associated with increased Charlson scores (OR 1.3, 95% CI 1.1–1.5), MRSA bacteremia (OR 3.2, 95% CI 1.4–8.1), presentation with septic shock (OR 13.5, 95% CI 5.4–36.4), and occurrence of endocarditis (OR 4.5, 95%CI 1.4–14.6). Similar risk factors were identified for late mortality, including increased Charlson scores (OR 1.2, 95% CI 1.1–1.4), MRSA bacteremia (OR 2.1, 95% CI 1.2–3.9), presentation with septic shock (OR 4, 95%CI 1.7–9.7), occurrence of endocarditis (OR 3.8, 95% CI 1.4–10.2) as well as Child C cirrhosis (OR 3.9, 95% CI 1.1–14.4) and primary bacteremia (OR 2.5, 95%CI 1.3–5). Infectious disease consultation resulted in better outcomes both at 7 (OR 0.1, 95% CI 0.05–0.4) and at 30 days (OR 0.4, 95% CI 0.2–0.7). In conclusion, our study highlighted high rates of MRSA infection in nosocomial Staphylococcus aureus bacteremia. Multiple comorbidities, disease severity and methicillin-resistance are key factors for early and late mortality in this group. In patients with Staphylococcus aureus bacteremia, infectious disease consultation remains a valuable tool to improve clinical outcome.

Paediatric Staphylococcus aureus bacteraemia: A single-centre retrospective cohort

AIM

We aimed to describe the clinical epidemiology of Staphylococcus aureus bacteraemia (SAB) at a large, tertiary/quaternary children's hospital in Australia.

METHODS

We performed a retrospective chart review of SAB cases at the Children's Hospital at Westmead (CHW) over 5 years; 2006-2011. We compared frequency, clinical profile and outcomes of SAB with published data from CHW; 1994-1998. We compared health-care associated with community-associated (HCA-SAB and CA-SAB; defined epidemiologically) and methicillin-resistant with methicillin susceptible S. aureus (MRSA and MSSA).

RESULTS

We identified 174 episodes of paediatric SAB with an average annual admission rate of 1.3/1000 which has not increased compared with a decade earlier. Half of the cases (49%) were CA-SAB; 18% were MRSA. The proportion of CA-MRSA bacteraemia (22%) has increased. The proportion of SAB associated with central venous access devices (CVADs; 40%) has increased. CA-SAB cases were more likely to present with a tissue focus of disease (e.g. osteo-articular, pneumonia) and often required surgery. HCA-SAB less frequently required surgery, a minority is MRSA, and vascular device intervention (removal, sterilisation) is common. Six cases (4%) of infective endocarditis (IE) were identified; three with a history of congenital heart disease, two with CVADs in situ. There were no deaths in this cohort.

CONCLUSIONS

Over an 18-year period, the proportion of SAB due to CA-MRSA and SAB associated with CVADs has increased. Categorisation of SAB as HCA and CA reveals two broad phenotypes of paediatric SAB. SAB in children is infrequently associated with IE. The health-care burden of paediatric SAB is considerable', but mortality is low.

Update of the activity of telavancin against a global collection of Staphylococcus aureus causing bacteremia, including endocarditis (2011-2014)

The efficacy and safety of telavancin is under evaluation for the treatment of subjects with complicated Staphylococcus aureus bacteremia and S. aureus right-sided infective endocarditis. This study evaluated the telavancin activity against a global collection of S. aureus causing bloodstream infections (BSI), including endocarditis, to support the development of bacteremia/endocarditis clinical indications. This study included a total of 4191 S. aureus [1490 methicillin-resistant S. aureus (MRSA)], which were unique (one per patient) clinical isolates recovered from blood samples collected during 2011-2014 in a global network of hospitals. All isolates were deemed responsible for BSI, including endocarditis, by local guidelines. Isolates were tested for susceptibility by broth microdilution. Telavancin (MIC_50/90, 0.03/0.06 μg/ml) inhibited all S. aureus at ≤0.12 μg/ml, the breakpoint for susceptibility. Equivalent minimum inhibitory concentration (MIC) values (MIC_50/90, 0.03/0.06 μg/ml) were obtained for telavancin against methicillin-susceptible S. aureus (MSSA) and MRSA isolates, as well as MRSA from community and healthcare origins. Similar telavancin activities (MIC₅₀, 0.03 μg/ml) were observed against MRSA subsets from North America and Europe, while isolates from the Asia-Pacific (APAC) and Latin America regions had MIC₅₀ values of 0.06 μg/ml. MRSA with vancomycin MIC values of 2-4 μg/ml and the multidrug resistance (MDR) subset had telavancin MIC₅₀ results of 0.06 μg/ml, although the MIC₁₀₀ result obtained against these subsets remained identical to those of MSSA (MIC₁₀₀, 0.12 μg/ml, respectively). This study updates the telavancin in vitro activity, which continues to demonstrate great potency against invasive S. aureus, regardless of the susceptibility phenotype or demographic characteristics (100.0% susceptible), and supports the sought-after subsequent indications.

Broad-Range Detection of Microorganisms Directly from Bronchoalveolar Lavage Specimens by PCR/Electrospray Ionization-Mass Spectrometry

The clinical demand on rapid microbiological diagnostic is constantly increasing. PCR coupled to electrospray ionization-mass spectrometry, PCR/ESI-MS, offers detection and identification of over 750 bacteria and Candida species directly from clinical specimens within 6 hours. In this study, we investigated the clinical performance of the IRIDICA BAC LRT Assay for detection of bacterial pathogens in 121 bronchoalveolar lavage (BAL) samples that were received consecutively at our bacterial laboratory for BAL culture. Commensal or pathogenic microorganisms were detected in 118/121 (98%) BAL samples by PCR/ESI-MS, while in 104/121 (86%) samples by routine culture (P<0.01). Detection of potentially pathogenic microorganisms by PCR/ESI-MS was evaluated in comparison with conventional culture-based or molecular methods. The agreement between positive findings was overall good. Most Staphylococcus aureus-positive PCR/ESI-MS results were confirmed by culture or species-specific PCR (27/33, 82%). The identity of Streptococcus pneumoniae could however be confirmed for only 6/17 (35%) PCR/ESI-MS-positive samples. Non-cultivable and fastidious pathogens, which were not covered by standard culture procedures were readily detected by PCR/ESI-MS, including Legionella pneumophila, Bordetella pertussis, Norcadia species and Mycoplasma pneumoniae. In conclusion, PCR/ESI-MS detected a broad range of potential pathogens with equal or superior sensitivity compared to conventional methods within few hours directly from BAL samples. This novel method might thus provide a relevant tool for diagnostics in critically ill patients.

Invasive MRSA infections in neurosurgical patients - a decade of progress

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of bloodstream infection (BSI), which is declining in many countries, including Ireland. However, it also causes other invasive infections, such as meningitis in neurosurgical patients. It is unclear whether the decline in MRSA BSI is reflected in other invasive infections and in specialist units.

AIM

To investigate trends in the incidence of MRSA invasive infection in a national neurosurgical centre over a 10-year period.

METHODS

A retrospective review of neurosurgical patients with MRSA recovered from sterile sites and indicating invasive infection, according to internationally agreed definitions was conducted between January 2006 and December 2015. Rates per 10,000 bed days used (BDU) and neurosurgical bed days used (NBDU) were calculated and trends were analysed.

RESULTS

Forty-four cases of invasive MRSA infection were identified over the study period. The majority were BSI (26, 59%) followed by ventriculitis (8, 18%). Invasive MRSA infections declined significantly from 0.52 per 10,000 BDU (or 4.65 per 10,000 NBU) in 2006 to 0.22 per 10,000 BDU (or 2.04 per 10,000 NBDU) in 2015, p < .01, despite an increase in neurosurgical clinical activity. Half of the infections occurred in patients with no previous history of MRSA colonisation/infection. The mean length-of-stay for neurosurgical patients with invasive MRSA infections was 67 days (median 32.5 days), significantly greater for other neurosurgical patients (p < .01).

CONCLUSION

There has been a significant decrease in invasive MRSA infections in neurosurgical patients, reflecting national and international trends for MRSA BSI. This indicates that infection prevention and control measures have been effective in reducing invasive MRSA infections overall, thus contributing to improved patient care.

Antibacterial Resistance in Patients with Hematopoietic Stem Cell Transplantation

Recipients of hematopoietic stem cell transplantation (HSCT) are at substantial risk of bacterial, fungal, viral, and parasitic infections depending on the time elapsed since transplantation, presence of graft-versus-host disease (GVHD), and the degree of immunosuppression. Infectious complications in HSCT recipients are associated with high morbidity and mortality. Bacterial infections constitute the major cause of infectious complications, especially in the early post-transplant period. The emergence of antibacterial resistance complicates the management of bacterial infections in this patient group. Multidrug-resistant bacterial infections in this group of patients have attracted considerable interest and may lead to significant morbidity and mortality. Empirical antibacterial therapy in patients with HSCT and febrile neutropenia has a critical role for survival and should be based on local epidemiology. This review attempts to provide an overview of risk factors and epidemiology of emerging resistant bacterial infections and their management in HSCT recipients.

Targeting Alpha Toxin and ClfA with a Multimechanistic Monoclonal-Antibody-Based Approach for Prophylaxis of Serious Staphylococcus aureus Disease

Staphylococcus aureus produces numerous virulence factors, each contributing different mechanisms to bacterial pathogenesis in a spectrum of diseases. Alpha toxin (AT), a cytolytic pore-forming toxin, plays a key role in skin and soft tissue infections and pneumonia, and a human anti-AT monoclonal antibody (MAb), MEDI4893*, has been shown to reduce disease severity in dermonecrosis and pneumonia infection models. However, interstrain diversity and the complex pathogenesis of S. aureus bloodstream infections suggests that MEDI4893* alone may not provide adequate protection against S. aureus sepsis. Clumping factor A (ClfA), a fibrinogen binding protein, is an important virulence factor facilitating S. aureus bloodstream infections. Herein, we report on the identification of a high-affinity anti-ClfA MAb, 11H10, that inhibits ClfA binding to fibrinogen, prevents bacterial agglutination in human plasma, and promotes opsonophagocytic bacterial killing (OPK). 11H10 prophylaxis reduced disease severity in a mouse bacteremia model and was dependent on Fc effector function and OPK. Additionally, prophylaxis with 11H10 in combination with MEDI4893* provided enhanced strain coverage in this model and increased survival compared to that obtained with the individual MAbs. The MAb combination also reduced disease severity in murine dermonecrosis and pneumonia models, with activity similar to that of MEDI4893* alone. These results indicate that an MAb combination targeting multiple virulence factors provides benefit over a single MAb neutralizing one virulence mechanism by providing improved efficacy, broader strain coverage, and protection against multiple infection pathologies.

Alternative strategies to broad-spectrum antibiotics are required to combat the antibiotic resistance epidemic. Previous attempts at active or passive immunization against Staphylococcus aureus targeting single antigens have failed in clinical trials despite positive preclinical data. To provide broad disease and isolate coverage, an effective immunization strategy likely must target multiple virulence mechanisms of the pathogen. Herein, we tested a multimechanistic MAb combination targeting alpha toxin (AT) and clumping factor A (ClfA) that neutralizes AT-mediated cytotoxicity, blocks fibrinogen binding by ClfA, prevents bacterial agglutination, targets the bacteria for opsonophagocytic killing, and provides broad isolate coverage in a lethal-bacteremia model. Although each MAb alone was effective in bacteremia against some individual isolates, the MAb combination provided improved protection against other isolates. These results illustrate the importance of targeting multiple virulence mechanisms and highlight the potential for an MAb combination targeting AT and ClfA to effectively prevent S. aureus disease.

Chronic heart failure and mortality in patients with community-acquired Staphylococcus aureus bacteremia: a population-based cohort study

Background

Patients with chronic heart failure (CHF) may experience higher mortality of Staphylococcus aureus bacteremia (SAB) than patients without CHF due to insufficient cardiovascular responses during systemic infection. We investigated 90-day mortality in SAB patients with and without CHF.

Methods

Using population-based medical databases, we conducted a cohort study of all adult patients with community-acquired SAB (CA-SAB) in Northern Denmark, 2000-2011. Ninety-day mortality after SAB for patients with and without CHF was estimated by the Kaplan-Meier method. Based on Cox regression analysis, we computed hazard ratios as estimates of mortality rate ratios (MRRs) overall and stratified by CHF-related conditions (e.g., cardiomyopathy and valvular heart disease), CHF severity (defined by daily dosage of loop-diuretics), and CHF duration while adjusting for potential confounders.

Results

Among 2638 SAB patients, 390 (14.8 %) had a history of CHF. Ninety-day mortality was 45 % in patients with CHF and 30 % in patients without CHF, which yielded an adjusted MRR (aMRR) of 1.24 (95 % CI, 1.04-1.48). Compared to patients without CHF, the excess risk of death was most pronounced among patients with valvular heart disease (aMRR = 1.73 (95 % CI, 1.26–2.38)), patients with daily loop-diuretic dosages of 81–159 mg/day (aMRR = 1.55 (95 % CI, 1.11–2.14)) and ≥160 mg/day (aMRR = 1.62 (95 % CI, 1.21–2.18)), and among patients with <3 years of CHF duration (aMRR = 1.43 (95 % CI, 1.14–1.78)).

Conclusion

CA-SAB patients with CHF experienced increased 90-day mortality compared to patients without CHF.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1570-7) contains supplementary material, which is available to authorized users.

Staphylococcus aureus: the current state of disease, pathophysiology and strategies for prevention

Staphylococcus aureus is both a commensal organism and also an important opportunistic human pathogen, causing a variety of community and hospital-associated pathologies, such as bacteremia-sepsis, endocarditis, pneumonia, osteomyelitis, arthritis and skin diseases. The resurgence of S. aureus during the last decade in many settings has been facilitated not only by bacterial antibiotic resistance mechanisms but also by the emergence of new S. aureus clonal types with increased expression of virulence factors and the capacity to neutralize the host immune response. Prevention of the spread of S. aureus infection relies on the use of contact precautions and adequate procedures for infection control that so far have not been fully effective. Prevention using a prophylactic vaccine would complement these processes, having the potential to bring additional, significant progress toward decreasing invasive disease due to S. aureus.

Epidemiology of antimicrobial resistance in bloodstream infections

Antimicrobial resistance in bacterial pathogens is a worldwide challenge leading high morbidity and mortality in clinical settings. Multidrug resistant patterns in gram-positive and -negative bacteria have resulted in difficult-to-treat or even untreatable infections with conventional antimicrobials. Since the early identification of causative microorganisms and their antimicrobial susceptibility patterns in patients with bacteremia and other serious infections is lacking in many healthcare institutions, broad spectrum antibiotics are liberally and mostly unnecessarily used. Such practice has, in turn, caused dramatic increases in emerging resistance and when coupled with poor practice of infection control, resistant bacteria can easily be disseminated to the other patients and the environment. Thus, availability of updated epidemiological data on antimicrobial resistance in frequently encountered bacterial pathogens will be useful not only for deciding on empirical treatment strategies, but also devising an effective antimicrobial stewardship program in hospitals.

Clonal Structure and Characterization of Staphylococcus aureus Strains from Invasive Infections in Paediatric Patients from South Poland: Association between Age, spa Types, Clonal Complexes, and Genetic Markers

The aim of current study was to examine clonal structure and genetic profile of invasive Staphylococcus aureus isolates recovered from infants and children treated at the Jagiellonian University Children’s Hospital of Krakow, Poland. The 107 invasive S. aureus isolates, collected between February 2012 and August 2014, were analysed retrospectively. Antimicrobial susceptibility testing, spa typing and DNA microarray analysis were performed to determine clonal distribution, diversity and gene content in regard to patients characteristics. In total, 107 isolates were recovered from 88 patients with clinical symptoms of invasive bacterial infection. The final set of 92 non-duplicate samples included 38 MRSA isolates. Additionally, a set of 54 S. aureus isolates collected during epidemiological screening was genotyped and analysed. There were 72 healthcare-associated (HCA) and 20 community-onset (CO) infection events caused by 33 and 5 MRSA isolates, respectively. The majority of isolates were affiliated with the major European clonal complexes CC5 (t003, spa-CC 002), CC45 (spa-CC 015), CC7 or CC15 (t084, t091, spa-CC 084). Two epidemic clones (CC5-MRSA-II or CC45-MRSA-IV) dominated among MRSA isolates, while MSSA population contained 15 different CCs. The epidemiological screening isolates belonged to similar genetic lineages as those collected from invasive infection cases. The HCA infection events, spa types t003, t2642 or CC5 were significantly associated with infections occurring in neonates and children under 5 years of age. Moreover, carriage of several genetic markers, including erm(A), sea (N315), egc-cluster, chp was significantly higher in isolates obtained from children in this age group. The spa types t091 and t008 were underrepresented among patients aged 5 years or younger, whereas spa type t008, CC8 and presence of splE was associated with infection in children aged 10 years or older. The HCA-MRSA strains were most frequently found in children under 5 years, although the majority of invasive infections was associated with MSSA strains. Moreover, an association between age group of children from the study population and a specific strain genotype (spa type, clonal complex or genetic content) was observed among the patients.

The T Cell Response to Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a dangerous pathogen and a leading cause of both nosocomial and community acquired bacterial infection worldwide. However, on the other hand, we are all exposed to this bacterium, often within the first hours of life, and usually manage to establish equilibrium and coexist with it. What does the adaptive immune system contribute toward lifelong control of S. aureus? Will it become possible to raise or enhance protective immune memory by vaccination? While in the past the S. aureus-specific antibody response has dominated this discussion, the research community is now coming to appreciate the role that the cellular arm of adaptive immunity, the T cells, plays. There are numerous T cell subsets, each with differing functions, which together have the ability to orchestrate the immune response to S. aureus and hence to tip the balance between protection and pathology. This review summarizes the state of the art in this dynamic field of research.

The Impact of Infectious Disease Specialist Consultation for Staphylococcus aureus Bloodstream Infections: A Systematic Review

Staphylococcus aureus is a common cause of severe bloodstream infection. We performed a systematic review to assess whether consultation with infectious disease specialists decreased all-cause mortality or rate of complications of S aureus bloodstream infections. The review also assessed parameters associated with the quality of management of the infection. We searched for eligible studies in PubMed, Embase, Scopus, and clinical trials.gov as well as the references of included studies. We identified 22 observational studies and 1 study protocol for a randomized trial. A meta-analysis was not performed because of the high risk of bias in the included studies. The outcomes are reported in a narrative review. Most included studies reported survival benefit, in the adjusted analysis. Recommended management strategies were carried out significantly more often among patients seen by an infectious disease specialist. Trials, such as cluster-randomized controlled trials, can more validly assess the studies at low risk of bias.

Population variation in anti-S. aureus IgG isotypes influences surface protein A mediated immune subversion

BACKGROUND

Staphylococcus aureus is a pathogen which causes life-threatening infection, the incidence of which rises during adult life. This, together with the emergence of drug-resistant strains and the expansion of more susceptible elderly populations, represents the rationale for the ongoing development of S. aureus vaccines targeting adult populations. Humoral responses to S. aureus naturally develop early in life, influence susceptibility to infection, and potentially influence the effect of vaccination. Despite this, the nature of pre-existing anti-S. aureus antibodies in healthy adult populations is not fully characterised.

METHODS

Immunoglobulin levels against S. aureus surface antigens were measured by a filter membrane enzyme-linked immunosorbent assay using fixed ΔSpA S. aureus as an antigen in serum samples obtained from three clinical cohorts comprising 133 healthy adult volunteers from 19 to 65 years of age. Functional capacity of antibody was also assessed, using antibody-mediated attachment of FITC-stained S. aureus to differentiated HL-60 cells.

RESULTS

Wide variation in the concentrations of immunoglobulins recognising S. aureus surface antigens was observed among individuals in all three cohorts. There was a decline of anti-S. aureus IgG1 with age, and a similar trend was observed in IgM, but not in IgA or other IgG sub-classes. Antibody mediated bacterial attachment to cells was associated with IgG1 and IgG3 concentrations in serum. The presence of SpA on the bacterial cell surface reduced antibody-mediated binding of bacteria to phagocytes in serum with low, but not high, levels of naturally occurring anti-S. aureus IgG3 antibodies.

CONCLUSIONS

Naturally acquired immunoglobulin responses to S. aureus are heterogeneous in populations and their concentrations alter during adulthood. Elevated IgG1 or IgG3 titres against S. aureus enhance S. aureus recognition by phagocytosis and may be correlates of natural protection and/or vaccine efficacy in adult populations.

Population-based epidemiology of Staphylococcus aureus bloodstream infection: clonal complex 30 genotype is associated with mortality

Staphylococcus aureus bloodstream infections (SABSI) are associated with a high burden of morbidity and mortality. The impact of specific S. aureus genotypes on outcome is unclear. The aim of this study was to evaluate the epidemiology and outcome of SABSI, with a special emphasis on the impact of bacterial clonal lineage on mortality. We conducted a 3-year population-based prospective study between 2011 and 2014, including 303 consecutive adult patients. Clinical data were obtained from interviews and medical records. S. aureus isolates were genotyped using DNA microarrays. The incidence rate of SABSI was 27.6 per 100,000 inhabitants [95 % confidence interval (CI) 24.6-31.0]. The median age of the patients was 71 years (interquartile range 56-81 years) and 61.4 % were male. Most SABSI (70.6 %) occurred in hospitals or associated to healthcare, and 34.1 % of these were associated with intravascular catheters. Only five (1.6 %) SABSI were caused by methicillin-resistant S. aureus (MRSA). The 30-day case fatality rate was 20.8 % (95 % CI 16.6-25.7). S. aureus clonal complex 30 [hazard ratio (HR) 3.9; 95 % CI 1.8-8.5, p = 0.001], unknown focus of infection (HR 4.5; 95 % CI 1.9-10.8, p = 0.001) and respiratory tract infection (HR 12.7; 95 % CI 4.6-34.6, p < 0.001) were independent predictors of mortality in a Cox regression analysis after adjusting for age, sex and underlying conditions. A high proportion of potential preventable SABSI calls for effective infection control measures. S. aureus clonal complex 30 genotype was associated with mortality in patients with bloodstream infections. The genetic basis underlying this association remains to be demonstrated.

The changing epidemiology of group B streptococcus bloodstream infection: a multi-national population-based assessment

BACKGROUND

Population-based studies conducted in single regions or countries have identified significant changes in the epidemiology of invasive group B streptococcus (GBS) infection. However, no studies have concurrently compared the epidemiology of GBS infections among multiple different regions and countries over time. The study objectives were to define the contemporary incidence and determinants of GBS bloodstream infection (BSI) and assess temporal changes in a multi-national population.

METHODS

Population-based surveillance for GBS BSI was conducted in nine regions in Australia, Canada, Denmark, Sweden, Finland and the UK during 2000-2010. Incidence rates were age- and gender-standardised to the EU population.

RESULTS

During 114 million patient-years of observation, 3464 cases of GBS BSI were identified for an overall annual incidence of 3.4 patients per 100,000 persons. There were marked differences in the overall (range = 1.8-4.1 per 100,000 person-year) and neonatal (range = 0.19-0.83 per 1000 live births) incidences of GBS BSI observed among the study regions. The overall incidence significantly (p = 0.05) increased. Rates of neonatal disease were stable, while the incidence in individuals older than 60 years doubled (p = 0.003). In patients with detailed data (n = 1018), the most common co-morbidity was diabetes (25%). During the study period, the proportion of cases associated with diabetes increased.

CONCLUSIONS

While marked variability in the incidence of GBS BSI was observed among these regions, it was consistently found that rates increased among older adults, especially in association with diabetes. The burden of this infection may be expected to continue to increase in ageing populations worldwide.

Incidence of invasive meticillin-resistant Staphylococcus aureus infections in Germany, 2010 to 2014

Voluntary surveillance systems in Germany suggest a recent decline in the incidence of infections (subsequent to at least 2010) with meticillin-resistant Staphylococcus aureus (MRSA) from various types of specimens and settings. We asked whether this decline is reflected by data from the mandatory national surveillance system for invasive MRSA infections. Our analysis is based on the population in Germany in 2010 to 2014. Cases were identified from passive reporting by microbiological laboratories of the diagnosis of MRSA from blood culture or cerebrospinal fluid. Respective clinical data were subsequently added to the notification. We calculated risk ratios (RR) between consecutive years, stratifying cases by sex, age and federal state of residence. The national incidence increased from 4.6 episodes per 100,000 persons in 2010 to 5.6 in 2012 (2011 vs 2010: RR: 1.13, 95% confidence interval (CI): 1.08–1.18; 2012 vs 2011: RR: 1.08, 95% CI: 1.04–1.13). It stagnated at 5.4 per 100,000 in 2013 (RR: 0.97, 95% CI: 0.93–1.01) before declining to 4.8 in 2014 (RR: 0.88, 95% CI: 0.84–0.91). This trend was observed in most, but not all federal states and strata of sex and age groups. Only 204 of 20,679 (1%) episodes of infection were notified as belonging to an outbreak. Our analysis corroborates previous findings that the incidence of invasive MRSA infections in Germany may be declining.

Infectious disease consultation for Staphylococcus aureus bacteremia - A systematic review and meta-analysis

OBJECTIVE

Mortality and morbidity of Staphylococcus aureus bacteremia (SAB) still remains considerably high. We aimed to evaluate the impact of infectious disease consultation (IDC) on the management and outcomes of patients with SAB.

METHODS

We systematically searched 3 publication databases from inception to 31st May 2015 and reference lists of identified primary studies.

RESULTS

Our search returned 2874 reports, of which 18 fulfilled the inclusion criteria, accounting for 5337 patients. Overall 30-day mortality was 19.95% [95% CI 14.37-27.02] with a significant difference in favour of the IDC group (12.39% vs 26.07%) with a relative risk (RR) of 0.53 [95% CI 0.43-0.65]. 90-day mortality and relapse risk for SAB were also reduced significantly with RRs of 0.77 [95% CI 0.64-0.92] and 0.62 [95% CI 0.39-0.99], respectively. Both, the appropriateness of antistaphylococcal agent and treatment duration was improved by IDC (RR 1.14 [95% CI 1.08-1.20] and 1.85 [95% CI 1.39-2.46], respectively). Follow-up blood cultures and echocardiography were performed more frequently following IDC (RR 1.35 [95% CI 1.25-1.46] and 1.98 [95% CI 1.66-2.37], respectively).

CONCLUSIONS

Evidence-based clinical management enforced by IDC may improve outcome of patients with SAB. Well-designed cluster-randomized controlled trials are needed to confirm this finding from observational studies.

Gender differences in rates of carriage and bloodstream infection caused by methicillin-resistant Staphylococcus aureus: are they real, do they matter and why?

There is increasing interest in sexual and gender dimorphism in disease. We reviewed the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) carriage and bloodstream infection (BSI), which shows a male predominance, and explored some of the possible reasons. Males are more prone to bacterial sepsis, but some studies suggest females may have a poorer prognosis from BSI. Hand-hygiene behavior varies according to gender. Males are less compliant, which in turn may predispose them to higher colonization and infection rates. Female hormones such as estrogen affect the expression of virulence factors in Pseudomonas aeruginosa, and although not studied, this may also apply to S. aureus. Further research is required on the relationship between gender and risk of infection, the reasons for higher MRSA carriage and BSI rates in males, the value of gender-specific infection prevention campaigns, and other factors such as the possible role of contact sports and occupation.

Daptomycin for the Treatment of Infective Endocarditis: Results from European Cubicin(®) Outcomes Registry and Experience (EU-CORE)

INTRODUCTION

The European Cubicin(®) Outcomes Registry and Experience (EU-CORE(SM)) was a retrospective, non-interventional, multicenter study which evaluated the safety and effectiveness of daptomycin therapy in patients with Gram-positive infections including infective endocarditis (IE).

METHODS

Data from the EU-CORE registry were collected for patients with IE who had received at least one dose of daptomycin between January 2006 and April 2012, across 18 countries in Europe (12), Latin America (5) and Asia (1). Clinical outcomes were assessed as success (cured or improved), failure or non-evaluable. Adverse events (AEs) were recorded during treatment and for up to 30 days post-treatment; follow-up data were collected for 2 years.

RESULTS

Of 6075 patients included in the EU-CORE registry, 610 were diagnosed with IE as primary infection; 149 (24.4%) right-sided IE (RIE), 414 (67.9%) left-sided IE (LIE), and 47 (7.7%) with both right- and left-sided IE (BRLIE). Overall clinical success was achieved in 80.0% of patients (RIE 88.6%, LIE 76.6% and BRLIE 82.9%). Success rates for methicillin-resistant Staphylococcus aureus (MRSA) infections were 90.9%, 71.7% and 66.6% in patients with RIE, LIE and BRLIE, respectively. The overall sustained clinical success rate in patients followed for up to 2 years was 86.7% (RIE 93.5%, LIE 88.3% and BRLIE 77.8%). AEs deemed possibly related to daptomycin in the investigator's opinion were reported in 2 (1.3%) RIE, 18 (4.3%) LIE and 1 (2.1%) BRLIE patients. There were 11 (1.8%) patients (2 with RIE, 8 with LIE and 1 with BRLIE) with AEs of creatine phosphokinase elevation reported as possibly related to daptomycin.

CONCLUSION

Data from this real-world clinical setting showed that daptomycin was well tolerated and effective for the treatment of LIE and BRLIE in addition to RIE caused by Gram-positive bacteria, including MRSA. Two-year follow-up data showed that a high proportion of patients had a sustained response.

Staphylococcus aureus infections: epidemiology, pathophysiology, clinical manifestations, and management

Staphylococcus aureus is a major human pathogen that causes a wide range of clinical infections. It is a leading cause of bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections. This review comprehensively covers the epidemiology, pathophysiology, clinical manifestations, and management of each of these clinical entities. The past 2 decades have witnessed two clear shifts in the epidemiology of S. aureus infections: first, a growing number of health care-associated infections, particularly seen in infective endocarditis and prosthetic device infections, and second, an epidemic of community-associated skin and soft tissue infections driven by strains with certain virulence factors and resistance to β-lactam antibiotics. In reviewing the literature to support management strategies for these clinical manifestations, we also highlight the paucity of high-quality evidence for many key clinical questions.

Multicenter study of health care cost of patients admitted to hospital with Staphylococcus aureus bacteremia: Impact of length of stay and intensity of care

BACKGROUND

Methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S aureus bacteremia (SAB) have both been associated with high morbidity and mortality and heavy consumption of health care resources. We compared clinical and economic data for hospitalized cases of SAB in the context of a publicly funded health care system.

METHODS

A cost analysis was undertaken on an adult cohort of patients from 4 hospitals with SAB diagnosed within 3 days of hospitalization. Primary outcome was direct cost of inpatient care per case, determined at discharge and itemized using a standardized methodology.

RESULTS

A total of 435 patients were admitted with SAB; 58 had methicillin-resistant S aureus (MRSA). The median length of stay was similar in patients with MRSA and MSSA. There was no significant difference between the groups for mortality. Median direct medical costs of SAB were $12,078. Patients with MRSA had 1.32 times higher direct costs than MSSA. A similar estimate was derived using a propensity score approach (P = .148). Human health care resources comprised >70% of total costs per case, whereas antibiotics comprised 1%-2%.

CONCLUSION

Understanding the dynamics of resource consumption is critical to improving its efficiency and the quality of patient care. Our findings suggest that hospital length of stay and care intensity should be the major focus of any resource assessment exercise.

Population-based epidemiology and microbiology of community-onset bloodstream infections

Bloodstream infection (BSI) is a major cause of infectious disease morbidity and mortality worldwide. While a positive blood culture is mandatory for establishment of the presence of a BSI, there are a number of determinants that must be considered for establishment of this entity. Community-onset BSIs are those that occur in outpatients or are first identified <48 h after admission to hospital, and they may be subclassified further as health care associated, when they occur in patients with significant prior health care exposure, or community associated, in other cases. The most common causes of community-onset BSI include Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Antimicrobial-resistant organisms, including methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase/metallo-β-lactamase/carbapenemase-producing Enterobacteriaceae, have emerged as important etiologies of community-onset BSI.

Diagnosis and treatment of bacteremia and endocarditis due to Staphylococcus aureus. A clinical guideline from the Spanish Society of Clinical Microbiology and Infectious Diseases (SEIMC)

Both bacteremia and infective endocarditis caused by Staphylococcus aureus are common and severe diseases. The prognosis may darken not infrequently, especially in the presence of intracardiac devices or methicillin-resistance. Indeed, the optimization of the antimicrobial therapy is a key step in the outcome of these infections. The high rates of treatment failure and the increasing interest in the influence of vancomycin susceptibility in the outcome of infections caused by both methicillin-susceptible and -resistant isolates has led to the research of novel therapeutic schemes. Specifically, the interest raised in recent years on the new antimicrobials with activity against methicillin-resistant staphylococci has been also extended to infections caused by susceptible strains, which still carry the most important burden of infection. Recent clinical and experimental research has focused in the activity of new combinations of antimicrobials, their indication and role still being debatable. Also, the impact of an appropriate empirical antimicrobial treatment has acquired relevance in recent years. Finally, it is noteworthy the impact of the implementation of a systematic bundle of measures for improving the outcome. The aim of this clinical guideline is to provide an ensemble of recommendations in order to improve the treatment and prognosis of bacteremia and infective endocarditis caused by S. aureus, in accordance to the latest evidence published.

Validity of calendar day-based definitions for community-onset bloodstream infections

BACKGROUND

Community-onset (CO) bloodstream infections (BSI) are those BSI where the blood culture is drawn <48 hours from hospital admission. However, exact times of culture draw or hospital admission are not always available. We evaluated the validity of using 2- or 3- calendar day based definitions for CO-BSI by comparing to a "gold standard" 48-hour definition.

FINDINGS

Among the population-based cohort of 14,106 episodes of BSI studied, 10,543 were classified as CO based on "gold standard" 48-hour criteria. When 2-day and 3-day definitions were applied, 10,396 and 10,707 CO-BSI episodes were ascertained, respectively. All but 147 (1.4%) true CO-BSI cases were included by using the 2-day definition. When the 3-day definition was applied, all cases of CO-BSI were identified but and additional 164 (1.5%) cases of hospital-onset HO-BSI were also included. Thus the sensitivity and specificity of the 2-day definition was 98.6% and 100% and for the 3-day definition was 100% and 98.5%, respectively. Overall, only 311 (2.2%) cases were potentially miss-classifiable using either the 2- or 3-calendar day based definitions.

CONCLUSIONS

Use of either a 2- or 3-day definition is highly accurate for classifying CO-BSI.

Epidemiology and outcome of Staphylococcus aureus bloodstream infection and sepsis in a Norwegian county 1996-2011: an observational study

BACKGROUND

Staphylococcus aureus is one of the most common and lethal causes of bloodstream infection and the incidence is increasing. We carried out a prospective observational study of patients with Staphylococcus aureus bloodstream infection and sepsis in Nord-Trøndelag county in Norway from 1996-2011. The main outcome of interest was all-cause mortality within 30 and 90 days.

METHODS

Positive blood cultures were registered prospectively by the microbiology laboratory and clinical variables were retrospectively registered from patients' hospital records. The severity of sepsis was assigned according to the 2001 International Sepsis Definition Conference criteria. The association between clinical characteristics and mortality was studied using logistic regression analysis, and adjusted 30- and 90-day mortality risks were estimated.

RESULTS

Among 373 patients, the median age was 74 years and 60.3% were male. 0.8% of the patients were diagnosed with MRSA. 29.8% of the patients developed severe sepsis and 12.9% developed septic shock. The all-cause mortality was 14.5%, 27.3% and 36.2% at 7, 30 and 90 days, respectively. Compared to patients with sepsis without organ failure (Mortality risk 13.3%, 95% CI 7.5-16.3%), the 30-day mortality risk was 3-fold higher among those with severe sepsis (39.9%, 95% CI 29.5-48.5%) and more than 4-fold higher for those with septic shock (57.3%, 95% CI 42.5-72.2%). The 30-day all-cause mortality varied by focus of infection, with the highest 30-day mortality risk among those with a pulmonary focus (42.4%, 95% CI 26.0-58.5%) and unknown focus of infection (38.7%, 95% CI 27.5-48.2%). The mortality risk did not differ between the first and second halves of the study period with a 30-day mortality risk of 27.3%, (95% CI 18.1-33.1%) for 1996-2003 versus 27.4% (95% CI 19.4-31.4%) for 2004-2011. The same pattern was seen for 90-day mortality risk.

CONCLUSION

Staphylococcus aureus bloodstream infection carries a high case fatality rate, especially among those with severe sepsis and septic shock and among those with a pulmonary or unknown focus of infection. There was no decrease in 30- or 90-day mortality risk during the study period. This underscores the importance of continuing surveillance and efforts to improve the outcome of this serious disease.

Impact of prior healthcare-associated exposure on clinical and molecular characterization of methicillin-susceptible Staphylococcus aureus bacteremia: results from a retrospective cohort study

By virtue of medical advances and an aging society, people have increased opportunities for healthcare exposure. Little is known about the impact of healthcare exposure on the clinical features and molecular typing of methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia. We classified the onset of MSSA bacteremia into 3 mutually exclusive categories according to the Centers for Disease Control definition, and conducted a retrospective cohort study to investigate the differences among patients with community-associated (CA), healthcare-associated community onset (HACO), and hospital onset (HO) MSSA bacteremia at a medical center from January 1, 2002 through December 31, 2011. Antibiotic susceptibilities and multilocus sequence typing of MSSA isolates were also determined. A total of 290 patients with MSSA bacteremia, including of 165 (56.9%), 91 (31.4%), and 34 (11.7%) of HACO, HO, and CA, respectively, were studied. ST188 (29.3%) was the most common sequence type regardless of classification. Patients with HACO bacteremia were significantly older, had more solid tumors, higher Charlson scores, and more catheter-related bloodstream infections than those with CA bacteremia. The proportions of osteoarticular infections among patients with both HACO and CA bacteremia were higher than that of patients with HO bacteremia. By univariate analysis, patients with HO bacteremia had significantly higher in-hospital mortality compared to those with CA or HACO bacteremia (31.9% vs 18.8% and 20.4%). Multivariate analysis showed that Charlson score (odds ratio [OR], 1.29; 95% confidence interval [CI], 1.10-1.52), septic shock (OR, 5.28; 95% CI, 2.37-11.78), liver cirrhosis (OR, 3.57; 95% CI, 1.14-11.24), receipt of β-lactams other than oxacillin and cefazolin as definitive therapy (OR, 9.27; 95% CI, 4.25-20.23), and higher oxacillin minimum inhibitory concentration (MIC) (≥0.5 mg/L) (OR, 2.35; 95% CI, 1.05-5.25) of the causative pathogen were independently associated with in-hospital mortality. In conclusion, patients with HACO bacteremia had different host factors compared with those with CA bacteremia. Infection foci varied with different onset settings. Overall, ST188 was the most predominant sequence type. Onset settings were not independently associated with outcomes.

Low mortality of Staphylococcus aureus bacteremia in Icelandic children: nationwide study on incidence and outcome

BACKGROUND

Staphylococcus aureus is a major cause of blood stream infections, but population-based studies on pediatric S. aureus bacteremia (SAB) are sparse. The objective of the study was to evaluate the incidence and mortality of SAB in Icelandic children over time, and to assess the proportions of nosocomial and health-care-associated infections.

METHODS

Children <18 years with positive blood cultures for S. aureus from January 1995 through December 2011 were identified retrospectively at the clinical microbiology laboratories performing blood cultures in Iceland. Clinical data were collected from medical records.

RESULTS

In total, 140 children had 146 distinct episodes of SAB. Bacteremia-related mortality was 0.7% (1/146), all-cause 30-day mortality, 1.4% (2/146), and 1-year mortality, 3.6% (5/140). The annual incidence of SAB was 10.9/100,000 children, decreasing by 36% from 13.1/100,000 in 1995-2003 to 8.4/100,000 in 2004-2011 (P < 0.001). At the same time the annual number of blood cultures analyzed at the main study site decreased from 1529 to 1143 (25%). SAB incidence was highest in infants (<1 year), 58.8/100,000. Of 146 episodes 50 (34%) were nosocomial, 21 (14%) health-care associated and 75 (51%) community acquired. No methicillin-resistant S. aureus isolate was identified.

CONCLUSIONS

In this nationwide study on pediatric SAB, the case fatality ratio was very low. A decreasing incidence was seen, possibly related to fewer blood cultures being collected. Nosocomial and health-care-associated infections accounted for 50% of the cases. The findings provide useful information on the epidemiology and outcome of SAB in children.

Risk and prognosis of Staphylococcus aureus bacteremia among individuals with and without end-stage renal disease: a Danish, population-based cohort study

Background

Staphylococcus aureus is a leading cause of bloodstream infections among hemodialysis patients and of exit-site infections among peritoneal dialysis patients. However, the risk and prognosis of Staphylococcus aureus bacteremia among end-stage renal disease patients have not been delineated.

Methods

In this Danish nationwide, population-based cohort study patients with end-stage renal disease and matched population controls were observed from end-stage renal disease diagnosis/sampling until first episode of Staphylococcus aureus bacteremia, death, or end of study period. Staphylococcus aureus positive blood cultures, hospitalization, comorbidity, and case fatality were obtained from nationwide microbiological, clinical, and administrative databases. Incidence rates and risk factors were assessed by regression analysis.

Results

The incidence rate of Staphylococcus aureus bacteremia was very high for end-stage renal disease patients (35.7 per 1,000 person-years; 95% CI, 33.8-37.6) compared to population controls (0.5 per 1,000 person-years; 95% CI, 0.5-0.6), yielding a relative risk of 65.1 (95% CI, 59.6-71.2) which fell to 28.6 (95% CI, 23.3-35.3) after adjustment for sex, age, and comorbidity. After stratification for type of renal replacement therapy, we found the highest incidence rate of Staphylococcus aureus bacteremia among hemodialysis patients (46.3 per 1,000 person-years) compared to peritoneal dialysis patients (22.0 per 1,000 person-years) and renal transplant recipients (8.9 per 1,000 person-years). In persons with Staphylococcus aureus bacteremia, ninety-day case fatality was 18.2% (95% CI, 16.2%-20.3%) for end-stage renal disease patients and 33.7% (95% CI, 30.3-37.3) for population controls.

Conclusions

Patients with end-stage renal disease, and hemodialysis patients in particular, have greatly increased risk of Staphylococcus aureus bacteremia compared to population controls. Future challenges will be to develop strategies to reduce Staphylococcus aureus bacteremia-related morbidity and death in this high-risk population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0740-8) contains supplementary material, which is available to authorized users.

Bacteremia, Sepsis, and Infective Endocarditis Associated with Staphylococcus aureus

Bacteremia and infective endocarditis (IE) are important causes of morbidity and mortality associated with Staphylococcus aureus infections. Increasing exposure to healthcare, invasive procedures, and prosthetic implants has been associated with a rising incidence of S. aureus bacteremia (SAB) and IE since the late twentieth century. S. aureus is now the most common cause of bacteremia and IE in industrialized nations worldwide and is associated with excess mortality when compared to other pathogens. Central tenets of management include identification of complicated bacteremia, eradicating foci of infection, and, for many, prolonged antimicrobial therapy. Evolving multidrug resistance and limited therapeutic options highlight the many unanswered clinical questions and urgent need for further high-quality clinical research.

Long term molecular epidemiology of methicillin-susceptible Staphylococcus aureus bacteremia isolates in Sweden

Staphylococcus aureus is one of the major pathogens that causes bacteremia; therefore, it is important to understand the long-term molecular epidemiology of S. aureus bacteremia infections. In particular, little is known about the population structure of methicillin-sensitive S. aureus (MSSA) compared to that of methicillin-resistant S. aureus. We investigated potential changes in the MSSA molecular epidemiology in Örebro County, Sweden, from 1980 through 2010. 400 MSSA bacteremia isolates, the first 100 isolated each decade from 1980 through 2010, were retrospectively identified and analyzed regarding assignment to clonal complexes (CCs), presence of virulence genes and antibiotic resistant determinants with DNA microarray-based genotyping. 24 different CCs were identified. Most isolates (80%) belonged to 6 predominant lineages. Of those, the number of isolates assigned to CC5 and CC15 increased, and those assigned to CC8, CC25, and CC30 decreased. The most prevalent clone, CC45, did not show a significant change in prevalence during the study period. A change in prevalence was observed for some of the virulence genes, mainly attributed with their association to certain CCs. With the exception of the common blaZ gene (encoding penicillinase), antibiotic resistance genes were only sporadically detected. In conclusion, the MSSA population structure was genetically diverse. We observed decadal changes in assignments to five predominant clones, and corresponding changes in the prevalence of some virulence genes linked to CC affiliation. In light of the restrictive antibiotics prescriptions and extensive infection control procedures in Sweden, antibiotic resistance genes were rarely detected and their prevalence unaffected during the study period.

A major reduction in hospital-onset Staphylococcus aureus bacteremia in Australia-12 years of progress: an observational study

BACKGROUND

Staphylococcus aureus bacteremia (SAB) is a serious cause of morbidity and mortality. This longitudinal study describes significant reductions in hospital-onset SAB (HO-SAB) in Australian hospitals over the past 12 years.

METHODS

An observational cohort study design was used. Prospective surveillance of HO-SAB in 132 hospitals in Australia was undertaken. Aggregated data from all patients who acquired HO-SAB was collected (defined as 1 or more blood cultures positive for S. aureus taken from a patient who had been admitted to hospital for >48 hours). The primary outcome was the incidence of HO-SAB, including both methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) S. aureus strains.

RESULTS

A total of 2733 HO-SAB cases were identified over the study period, giving an aggregate incidence of 0.90 per 10 000 patient-days (PDs) (95% confidence interval [CI], .86-.93). There was a 63% decrease in the annual incidence, from 1.72 per 10 000 PDs in 2002 (95% CI, 1.50-1.97) to 0.64 per 10 000 PDs (95% CI, .53-.76) in 2013. The mean reduction per year was 9.4% (95% CI, -8.1% to -10.7%). Significant reductions in both HO-MRSA (from 0.77 to 0.18 per 10 000 PDs) and HO-MSSA (from 1.71 to 0.64 per 10 000 PDs) bacteremia were observed.

CONCLUSIONS

There was a major and significant reduction in incidence of HO-SAB caused by both MRSA and MSSA in Australian hospitals since 2002. This reduction coincided with a range of infection prevention and control activities implemented during this time. It suggests that national and local efforts to reduce the burden of healthcare-associated infections have been very successful.

The Danish Collaborative Bacteraemia Network (DACOBAN) database

The Danish Collaborative Bacteraemia Network (DACOBAN) research database includes microbiological data obtained from positive blood cultures from a geographically and demographically well-defined population serviced by three clinical microbiology departments (1.7 million residents, 32% of the Danish population). The database also includes data on comorbidity from the Danish National Patient Registry, vital status from the Danish Civil Registration System, and clinical data on 31% of nonselected records in the database. Use of the unique civil registration number given to all Danish residents enables linkage to additional registries for specific research projects. The DACOBAN database is continuously updated, and it currently comprises 39,292 patients with 49,951 bacteremic episodes from 2000 through 2011. The database is part of an international network of population-based bacteremia registries from five developed countries on three continents. The main purpose of the DACOBAN database is to study surveillance, risk, and prognosis. Sex- and age-specific data on background populations enables the computation of incidence rates. In addition, the high number of patients facilitates studies of rare microorganisms. Thus far, studies on Staphylococcus aureus, enterococci, computer algorithms for the classification of bacteremic episodes, and prognosis and risk in relation to socioeconomic factors have been published.

Synergistic activity and mechanism of action of Stephania suberosa Forman extract and ampicillin combination against ampicillin-resistant Staphylococcus aureus

Background

Ampicillin-resistant S. aureus (ARSA) now poses a serious problem for hospitalized patients, and their care providers. Plant-derived antibacterial that can reverse the resistance to well-tried agents which have lost their original effectiveness are the research objectives of far reaching importance. To this aim, the present study investigated antibacterial and synergistic activities of Stephania suberosa extracts (SSE) against ARSA when used singly and in combination with ampicillin.

Results

The majority chemical compounds of SSE were alkaloid (526.27 ± 47.27 mg/1 g of dried extract). The Minimum inhibitory concentration (MICs) for ampicillin and SSE against all ARSA strains were >512 μg/ml and 4 mg/ml, respectively. Checkerboard assay revealed synergistic activity in the combination of ampicillin (0.15 μg/ml) and SSE (2 mg/ml) at fractional inhibitory concentration index (FICI) <0.5. The killing curve assay had confirmed that the viability of ARSA was dramatically reduced from 5x10⁵ cfu/ml to 10³ cfu/ml within 6 h after exposure to SSE (2 mg/ml) plus ampicillin (0.15 μg/ml) combination. Electron microscopic study clearly revealed that these ARSA cells treated with this combination caused marked morphological damage, peptidoglycan and cytoplasmic membrane damage, and average cell areas significant smaller than control. Obviously, Immunofluorescence staining and confocal microscopic images confirmed that the peptidoglycan of these cells were undoubtedly disrupted by this combination. Furthermore, the CM permeability of ARSA was also increased by this combination. Enzyme assay demonstrated that SSE had an inhibitory activity against β-lactamase in concentrations manner.

Conclusions

So, these findings provide evidence that SSE has the high potential to reverse bacterial resistance to originate traditional drug susceptibility of it and may relate to three modes of actions of SSE: (1) inhibits peptidoglycan synthesis, resulting in morphological damage, (2) inhibits β-lactamases activity, and (3) increases CM permeability. It is widely recognized that many types of drugs are derived from alkaloids. So, this SSE offers the prominent potential to develop a novel adjunct phytopharmaceutical to ampicillin for the treatment of ARSA. Further active ingredients study, toxicity of it, and the synergistic effect on blood and tissue should be performed and confirmed in an animal test or in humans.

Evaluation of vancomycin population susceptibility analysis profile as a predictor of outcomes for patients with infective endocarditis due to methicillin-resistant Staphylococcus aureus

Infective endocarditis due to methicillin-resistant Staphylococcus aureus (MRSA IE) is associated with high morbidity and mortality. Vancomycin continues to be the primary treatment for this disease. The emergence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA), defined as a modified population analysis profile (PAP) of ≥ 0.9, may affect patient outcomes. The objective of this study was to evaluate the relationship of vancomycin subpopulation susceptibility and the clinical outcomes of MRSA IE. We conducted a retrospective cohort study of patients treated with vancomycin for MRSA IE from 2002 to 2013 at the Detroit Medical Center. A modified PAP was used to measure the vancomycin PAP MIC and the PAP-to-area under the curve (AUC) ratio. Treatment failure was defined as bacteremia for ≥ 7 days or death attributed to MRSA. Classification and regression tree (CART) analysis was used to select a failure breakpoint between the PAP-AUC ratios and the PAP MIC. A total of 202 patients were included in the study. Twenty-seven percent of the patients had left-sided IE, 19% of the strains were hVISA, and 70% of the strains were staphylococcal cassette chromosome mec element (SCCmec) type IV. Overall treatment failure was observed in 64%; 59% had persistent bacteremia, and the 30-day attributable mortality rate was 21%. The CART breakpoint between failure and success in terms of the PAP-AUC ratio was 0.9035. On logistic regression analysis, intensive care unit (ICU) admission (adjusted odds ratio [aOR], 2.8; 95% confidence interval [CI], 1.5 to 5.2) and a PAP MIC of ≥ 4 mg/liter (aOR, 3.2; 95% CI, 1.3 to 8.4) were associated with failure (P = 0.001 and 0.015, respectively). A PAP MIC of ≥ 4 mg/liter and ICU admission were significant for treatment failure for patients with MRSA IE. The PAP-AUC ratio of ≥ 0.9035 predicted failure consistent with the hVISA definition. The role of population MIC analysis in predicting outcome with MRSA infections warrants further investigation.

The clinical and molecular epidemiology of Staphylococcus aureus infections in Fiji

Background

There are few data describing the microbiology and genetic typing of Staphylococcus aureus that cause infections in developing countries.

Methods

In this study we observed S. aureus infections in Pacific Island nation of Fiji in both the community and hospital setting with an emphasis on clonal complex (CC) genotyping and antimicrobial susceptibility.

Results

S. aureus was commonly found in impetigo lesions of school children and was recovered from 57% of impetigo lesions frequently in conjunction with group A streptococcal infection. Methicillin-resistant S. aureus (MRSA) comprised 7% (20/299) of isolates and were all non-multi-resistant and all genotyped as CC1. In contrast, there was a diverse selection of 17 CCs among the 105 genotyped methicillin-susceptible S.aureus (MSSA) strains. Isolates of the rare, phylogenetically divergent and non-pigmented CC75 lineage (also called S.argenteus) were found in Fiji.

From hospitalized patients the available 36 MRSA isolates from a 9-month period were represented by five CCs. The most common CCs were CC1 and CC239. CC1 is likely to be a community-acquired strain, reflecting what was found in the school children, whereas the CC239 is the very successful multi-drug resistant MRSA nosocomial lineage. Of 17 MSSA isolates, 59% carried genes for Panton-Valentine leukocidin. The S. aureus bacteraemia incidence rate of 50 per 100,000 population is among the highest reported in the literature and likely reflects the high overall burden of staphylococcal infections in this population.

Conclusions

S. aureus is an important cause of disease in Fiji and there is considerable genotypic diversity in community skin infections in Fijian schoolchildren. Community acquired- (CA)- MRSA is present at a relatively low prevalence (6.7%) and was solely to CC1 (CA-MRSA). The globally successful CC239 is also a significant pathogen in Fiji.

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.

Characteristics of invasive Staphylococcus aureus infections in three regions of Korea, 2009-2011: a multi-center cohort study

BACKGROUND

Despite the importance of invasive Staphylococcus aureus (ISA) infection, its overall burden in non-selected populations has only been defined in a small number of studies in Europe and North America. To define the characteristics of ISA infections in Korea, we conducted a multi-center cohort study to estimate population-based incidence rates.

METHODS

We conducted a multicenter prospective cohort study at nine university-affiliated active-surveillance core centers (ASCs) in three regions of Korea. To cover all available clinical microbiologic laboratories, we classified the laboratories in these regions into three groups according to their clinical environment as: 1) Nine ASCs, 2) Five major commercial laboratories and 3) Forty-four acute-care hospital-affiliated microbiology laboratories. We requested all the laboratories to report prospectively their numbers of cases of S. aureus isolated from normally sterile sites. Detailed clinical information was collected about the cases in the nine ASCs.

RESULTS

From 1 July 2009 to 30 June 2011, a total of 1,198 cases of ISA infection were identified at the nine ASCs, including 748 (62%) methicillin-resistant S. aureus (MRSA) infections. Most (81%) ISA infections were healthcare-associated (HCA): 653 (55%) hospital-onset and 322 (27%) community-onset. 223 (19%) were community-associated infections. The most common primary diagnosis was catheter-associated infection (225 cases, 19%). Respiratory tract infection (160, 13%), skin & soft tissue (152, 13%) and bone & joint infections (120, 10%) were also common. 30-day and 12-week mortality rates were 25.6% (262/1,024) and 36.5% (314/860), respectively. Complications, including metastatic infection within 12 weeks, occurred in 17.8% of ISA infections. The most common site of metastatic infection was the lung (9.8%, 84/860). Based on the total of 2,806 observed cases of ISA infection, estimated annual rates of ISA and invasive MRSA infections were 43.3 and 27.7 per 100,000 populations, respectively.

CONCLUSIONS

Our data provide important information about the clinical characteristics of ISA infections. We estimate that over 21,000 ISA infections and 13,000 invasive MRSA infections occurred in Korea in 2010.

Incidence, trends and demographics of Staphylococcus aureus infections in Auckland, New Zealand, 2001-2011

Background

New Zealand has a higher incidence of Staphylococcus aureus disease than other developed countries, with significant sociodemographic variation in incidence rates. In contrast to North America, the majority of disease is due to methicillin-susceptible S. aureus (MSSA), although relatively little is known about the comparative demographics of MSSA and methicillin-resistant S. aureus (MRSA) infections in New Zealand.

Methods

Our objectives were to describe the trends, incidence and patient demographics of all S. aureus infections in patients presenting to our institution between 2001 and 2011, and compare the epidemiology of MSSA and MRSA infections. We identified all patients with S. aureus infections over the study period. A unique S. aureus infection was defined as the first positive S. aureus culture taken from the same patient within a thirty-day period. Standard definitions were used to classify episodes into community- or healthcare-associated S. aureus infection.

Results

There were 16,249 S. aureus infections over the study period. The incidence increased significantly over the study period from 360 to 412 per 100,000 population (P < 0.001), largely driven by an increase in community-associated non-invasive MSSA infections. When compared with MSSA infections, patients with non-multiresistant MRSA infections were more likely to be older, have hospital-onset infections and be Māori or Pacific Peoples.

Conclusions

Our work provides valuable baseline data on the epidemiology and trends of S. aureus infections in New Zealand. The significant increase in community-associated S. aureus infections is of public health importance. Future studies should investigate the reasons underlying this concerning trend.

A recommendation to perform a blood culture before the administration of intravenous antibiotics increased the detection of Staphylococcus aureus bacteremia

In 2004, the Surviving Sepsis Campaign was launched to increase awareness and improve the outcome of severe sepsis. Accordingly, in Jönköping County, Sweden, a strong recommendation to perform a blood culture before the start of intravenous antibiotic treatment was introduced in 2007. Moreover, a reminder was included in the laboratory report to consult an infectious disease specialist when Staphylococcus aureus was isolated from a blood culture. Retrospectively, patients with at least one blood culture growing S. aureus during 2002 through 2003 (pre intervention n = 58) or during 2008 through 2009 (post intervention n = 100) were included. Medical records were evaluated regarding clinical data and outcome. Blood culture isolates were characterized by antibiotic susceptibility testing (AST) and S. aureus protein A (spa) gene typing. The annual incidence of S. aureus bacteremia (SAB) increased from 28 per 100,000 inhabitants at the pre intervention period to 45 per 100,000 at the post intervention period (p = 0.046). During post intervention, the SAB incidence was significantly higher in men (p = 0.009). The mortality rate during hospital stay was 14 % during pre intervention and 18 % during post intervention (p = 0.47). The most common spa types were t012 and t084. The Surviving Sepsis Campaign resulted in an increased number of detected cases of SAB. The mortality rate was the same before and after the intervention, and no spa type correlated to certain clinical manifestations or mortality.