Management of Patients with Staphylococcus aureus Bacteraemia in a University Hospital: A Retrospective Study

What Is the Optimal Follow-up Length for Mortality in Staphylococcus aureus Bacteremia? Observations From a Systematic Review of Attributable Mortality

Background

Deaths following Staphylococcus aureus bacteremia (SAB) may be related or unrelated to the infection. In SAB therapeutics research, the length of follow-up should be optimized to capture most attributable deaths and minimize nonattributable deaths. We performed a secondary analysis of a systematic review to describe attributable mortality in SAB over time.

Methods

We systematically searched Medline, Embase, and Cochrane Database of Systematic Reviews from 1 January 1991 to 7 May 2021 for human observational studies of SAB. To be included in this secondary analysis, the study must have reported attributable mortality. Two reviewers extracted study data and assessed risk of bias independently. Pooling of study estimates was not performed due to heterogeneity in the definition of attributable deaths.

Results

Twenty-four observational cohort studies were included. The median proportion of all-cause deaths that were attributable to SAB was 77% (interquartile range [IQR], 72%–89%) at 1 month and 62% (IQR, 58%–75%) at 3 months. At 1 year, this proportion was 57% in 1 study. In 2 studies that described the rate of increase in mortality over time, 2-week follow-up captured 68 of 79 (86%) and 48 of 57 (84%) attributable deaths that occurred by 3 months. By comparison, 1-month follow-up captured 54 of 57 (95%) and 56 of 60 (93%) attributable deaths that occurred by 3 months in 2 studies.

Conclusions

The proportion of deaths that are attributable to SAB decreases as follow-up lengthens. Follow-up duration between 1 and 3 months seems optimal if evaluating processes of care that impact SAB mortality.

Clinical Trials Registration

PROSPERO CRD42021253891.

Implementing a hospital-wide protocol for Staphylococcus aureus bacteremia

Staphylococcus aureus bacteraemia (SAB) is associated with high-mortality and complication rates. A multidisciplinary approach is needed to predict, detect and treat complications. In this pre- and post-intervention study, we investigated the effects of a hospital-wide protocol for diagnosis, classification and treatment of SAB. It was hypothesized that complications and endocarditis would be better identified and treated. Medical records of SAB patients admitted in 2011 and 2012 (pre) were analysed. In 2013, a protocol, describing risk factors, diagnostic classification and recommended treatment, was implemented. In 2014 and 2015 (post), SAB patients were followed prospectively. Transthoracic (TTE) or transoesophageal cardiac ultrasound (TEE) was chosen following a decision tree. A resident internal medicine acted as contact person. Pre-intervention, 98 patients were eligible for analysis compared to 85 patients post-intervention. Age and number of risk factors were slightly higher post-intervention; other baseline characteristics were similar. Most SAB-patients were classified as complicated (89 and 82% pre- and post-intervention, respectively). Follow-up blood cultures drawn within 2 days after initiating treatment increased from 51 to 85%. Cardiac ultrasounds increased from 44 to 83% for TTE and 13 to 24% for TEE. Endocarditis was more frequently diagnosed (4 vs. 12%). Additionally, duration of antibiotic therapy increased. The 3-month mortality did not change significantly (33% pre-intervention vs. 35% post-intervention; p > 0.05). Introduction of a hospital-wide protocol for SAB management increased standard of care, created awareness among clinicians to properly classify SAB, search for endocarditis and adapt duration of antibiotic treatment. Mortality did not decrease.

Staphylococcus aureus bacteraemia and endocarditis - epidemiology and outcome: a review

PURPOSE

To review the epidemiology of Staphylococcus aureus bacteraemia (SAB) and endocarditis (SAE), and discuss the short- and long-term outcome.  Materials and methods: A literature review of the epidemiology of SAB and SAE.

RESULTS

The reported incidence of SAB in Western countries is 16-41/100,000 person-years. Increasing incidence has been observed in many regions, in Iceland by 27% during 1995-2008. The increase is believed to depend on changes in population risk factors and possibly better and more frequent utilization of diagnostic procedures. S. aureus is now the leading causes of infective endocarditis (IE) in many regions of the world. It accounts for 15-40% of all IE cases, and the majority of cases in people who inject drugs (PWID). Recently, the incidence of SAE in PWID in Stockholm, Sweden, was found to be 2.5/1000 person-years, with an in-hospital mortality of 2.5% in PWID as compared to 15% in non-drug users. The 30-day mortality associated with SAB amounts to 15-25% among adults in Western countries, but is lower in children (0-9%). Mortality associated with SAE is high (generally 20-30% in-hospital mortality), and symptomatic cerebral embolizations are common (12-35%). The 1-year mortality reported after SAB and SAE is 19-62% and reflects deaths from underlying diseases and complications caused by the infection. In a subset of SAE cases, valvular heart surgery is needed (15-45%), but active intravenous drug use seems to be a reason to refrain from surgery. Despite its importance, there are insufficient data on the optimal management of SAB and SAE, especially on the required duration of antibiotic therapy.  Conclusions: The epidemiology of SAB and SAE has been changing in the past decades. They still carry a substantial morbidity and mortality. Intensified studies on treatment are warranted for improving patient outcome.

Selection of peptidoglycan-specific aptamers for bacterial cells identification

Peptidoglycan is a highly complex and essential macromolecule of bacterial outer cell wall; it is a heteropolymer made up of linear glycan strands cross-linked by peptides. Peptidoglycan has a particular composition which makes it a possible target for specific bacterial recognition. Aptamers are single-stranded DNA or RNA oligonucleotides that bind to target molecules with high affinity and specificity. Aptamers can be labeled with different radioisotopes and possess several properties that make them suitable for molecular imaging. The purpose of this study was to obtain aptamers for use as radiopharmaceutical in bacterial infection diagnosis. Two aptamers (Antibac1 and Antibac2) against peptidoglycan were selected through the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) methodology. The dissociation constant (Kd) for Antibac1 was 0.415 + 0.047 μM and for Antibac2 was 1.261 + 0.280 μM. These aptamers labeled with (32)P showed high affinity for Staphylococcus aureus cells. The binding to S. aureus and Escherichia coli in vitro were significantly higher than for Candida albicans and human fibroblasts, demonstrating their specificity for bacterial cells. These results point Antibac1 and Antibac2 as promising tools for bacterial infections identification.

Thirty-day mortality in UK patients with community-onset and hospital-acquired meticillin-susceptible Staphylococcus aureus bacteraemia

BACKGROUND

The difference in mortality between patients with community-onset and hospital-acquired Staphylococcus aureus infections has rarely been described and where it has, results have been conflicting.

AIM

To determine 30-day mortality in consecutive patients with meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia and the association between community-onset infection and outcome.

METHODS

From August 2007 to July 2011, demographic, clinical and microbiological data were prospectively collected on patients with MSSA bacteraemia. Patients were followed until death, hospital discharge or recovery from infection. Multivariate logistic regression was used to determine the association between community-onset infection and 30-day mortality.

FINDINGS

A total of 403 bacteraemic episodes occurred in 392 patients. Overall, there were 44 deaths (11.2%; 95% confidence interval: 7.9-14.0%) at 7 days and 101 deaths (25.8%; 21.5-30.4%) at 30 days. The difference in 30-day mortality between patients with community-onset and hospital-acquired infection was 71/256 (27.7%) versus 31/147 21.1%). Community-onset infection more frequently caused infective endocarditis (13/14, 92.9%), vertebral osteomyelitis (12/13, 92.3%) and skin and soft tissue infection (61/71, 85.9%) whereas intravascular catheter-associated infections were predominantly hospital-acquired (60/82, 73.2%). Age, Pitt score, Charlson comorbidity index (CCI), specific sites of infection (skin and soft tissue, lower respiratory tract and peripheral joints) and delay in appropriate treatment were strongly associated with 30-day mortality. In multivariate analysis, after adjustment for age, CCI and delay in appropriate treatment, community-onset infection was strongly associated with 30-day mortality (odds ratio: 1.59; 95% confidence interval: 0.91-2.80).

CONCLUSIONS

Compared with hospital-acquired MSSA bacteraemic infection, community-onset infection was associated with worse 30-day outcomes. Hospital-acquired MSSA bacteraemic infections were rarely metastatic, frequently associated with medical devices and patients had better outcomes.

Metastatic infectious disease and clinical outcome in Staphylococcus aureus and Streptococcus species bacteremia

Early detection of metastatic infection in patients with Gram-positive bacteremia is important as morbidity and mortality are higher in the presence of these foci, probably due to incomplete eradication of clinically silent foci during initial treatment. We performed a prospective study in 115 patients with Staphylococcus aureus or Streptococcus species bacteremia with at least 1 risk factor for the development of metastatic foci, such as community acquisition, treatment delay, persistently positive blood cultures for >48 hours, and persistent fever >72 hours after initiation of treatment. An intensive search for metastatic infectious foci was performed including ¹⁸F-fluorodeoxyglucose-positron emission tomography in combination with low-dose computed tomography scanning for optimizing anatomical correlation (FDG-PET/CT) and echocardiography in the first 2 weeks of admission. Metastatic infectious foci were detected in 84 of 115 (73%) patients. Endocarditis (22 cases), endovascular infections (19 cases), pulmonary abscesses (16 cases), and spondylodiscitis (11 cases) were diagnosed most frequently. The incidence of metastatic infection was similar in patients with Streptococcus species and patients with S. aureus bacteremia. Signs and symptoms guiding the attending physician in the diagnostic workup were present in only a minority of cases (41%). An unknown portal of entry, treatment delay >48 hours, and the presence of foreign body material were significant risk factors for developing metastatic foci. Mean C-reactive protein levels on admission were significantly higher in patients with metastatic infectious foci (74 vs. 160 mg/L). FDG-PET/CT was the first technique to localize metastatic infectious foci in 35 of 115 (30%) patients. As only a minority of foci were accompanied by guiding signs or symptoms, the number of foci revealed by symptom-guided CT, ultrasound, and magnetic resonance imaging remained low. Mortality tended to be lower in patients without complicated infection compared to those with metastatic foci (16% vs. 25%, respectively). Five of 31 patients (16%) without proven metastatic foci died. In retrospect, 3 of these 5 patients likely had metastatic foci that could not be diagnosed while alive. In patients with Gram-positive bacteremia and a high risk of developing complicated infection, a structured protocol including echocardiography and FDG-PET/CT aimed at detecting metastatic infectious foci can contribute to improved outcome.

Staphylococcus aureus bacteraemia--Nationwide assessment of treatment adequacy and outcome

OBJECTIVES

To assess the treatment adequacy for Staphylococcus aureus bacteraemia (SAB) and its association with outcome on a whole population basis.

METHODS

All individuals ≥18 years old diagnosed with SAB in Iceland between December 1 2003 and November 30 2008 were retrospectively identified. Clinical data was collected from medical records and adequacy of antibiotic treatment based on antibiotic choice, dose, administration route and treatment duration.

RESULTS

Empirical therapy was considered adequate in 262 of 325 (81%) SAB episodes, with no correlation to outcome. The complete antibiotic treatment was deemed adequate in 147 of 279 (53%) episodes. Among patients with complicated SAB median duration of active intravenous therapy was 14 days in those experiencing relapse compared to 30 days in patients without relapse (p = 0.03). No patient died after completing adequate treatment compared to 4 (3.0%) following inadequate therapy (p = 0.01). Despite no overall change being seen in antibiotic treatment, 30-day mortality decreased from 25.0 to 6.8% from first to last year of study (p = 0.001).

CONCLUSION

Appropriate antibiotic therapy for SAB was associated with lower relapse rates and mortality. Although treatment adequacy was regarded as insufficient in half of cases, mortality of SAB in Iceland is amongst the lowest recorded.

SUMMARY

In a national study of S. aureus bacteraemia the antibiotic treatment was judged inadequate in 53% of episodes, while appropriate treatment was associated with lower relapse rate and mortality. Despite this, the mortality in Iceland is among the lowest reported.

Staphylococcus aureus: An old pathogen with new weapons

Staphylococcus aureus has been recognized as an important human pathogen for more than 100 years. S aureus has been able to adapt and evolve in terms of its resistance traits and virulence factors; it is among the most important causes of human infections in the twenty-first century. Rapid molecular identification in the clinical microbiology laboratory of these resistance and virulence factors expressed by S aureus will play an important role in the future in decreasing the morbidity and mortality of infections. This article addresses the emerging aspects of infections caused by S aureus, including microbiology, epidemiology, clinical presentation, pathogenesis, diagnosis, treatment and prognosis, and immunity.

Outcome for invasive Staphylococcus aureus infections

We report a survey of invasive Staphylococcus aureus (ISA) infections concerning outcome variables such as mortality, recurrence and residual symptoms. A prospective, population-based study of all cases of ISA was conducted in the catchment area of Skaraborg Hospital (population 255,109) in western Sweden during the period from 1st March 2003 to 28th February 2005. One hundred and fifty-seven patients were included. Recurrences were seen in 13 cases (9.3%). Thirty patients (19.1%) died during the first 28 days. Mortality rates for complicated bacteraemia and severe sepsis were 32% and 54%, respectively. Older patients (>65 years of age), patients with concomitant heart disease and patients with endovascular infections all suffered higher mortality. Line-associated infections had a higher recurrence rate. Residual symptoms were common, with 34% of the living patients reporting incomplete recovery. Accessory gene regulator (agr) type within the bacteria did not affect disease presentation. We conclude that ISA infections are of major medical importance, with high rates of mortality (19.1%), recurrence (9.3%) and residual functional impairment (34%).

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Epidemiology, clinical and laboratory characteristics of Staphylococcus aureus bacteraemia in a university hospital in UK

There has been a persistent increase in the number of meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia in the UK. This prospective study included 147 episodes of S. aureus bacteraemia in 139 patients over a 14 month period, from 1 November 2001 to 31 December 2002. Eighty-seven (59%) episodes in 84 patients and 60 (41%) in 56 patients were due to MRSA and MSSA, respectively. An intra-vascular device (29, 33%) and a soft-tissue (15, 25%) source were the commonest identifiable foci for bacteraemia in the MRSA and MSSA groups, respectively. Attributable mortality in the MRSA group was higher than the MSSA group (33% vs 16%; P=0.03) but there was no statistical difference for either attributable (P=0.35) or crude (P=0.39) mortality between the two groups, when adjusted for age, respiratory focus and inappropriate antibiotic therapy. A respiratory source (P=0.02) and inappropriate antibiotic therapy (P=0.02) were associated with attributable mortality in the MRSA group whereas advanced age was the only risk factor (P=0.02) in the MSSA group. The present study shows that S. aureus bacteraemia continues to be a serious infection mostly affecting the elderly and emphasizes the need for improved strategy in the control and management of this condition.

Clinical and molecular epidemiology of nursing home-associated Staphylococcus aureus bacteremia

BACKGROUND AND OBJECTIVES

Although nursing home residents who have Staphylococcus aureus bacteremia (SAB) have been included in large studies of this infection, there are no published descriptions of SAB solely in nursing home residents. The objectives were to describe the clinical and molecular epidemiology of SAB in nursing home residents admitted to one hospital.

METHODS

This was a retrospective review of hospital medical records of nursing home residents from 22 separate facilities who had SAB and were admitted to a specialty unit at one hospital from 1997 to 2003.

RESULTS

For the seven-year study period, 39 episodes of SAB were identified; 15 were due to methicillin-susceptible S. aureus (MSSA) and 24 were due to methicillin-resistant S. aureus (MRSA). The incidence of SAB among all residents admitted to the specialty unit increased by more than eightfold primarily because of an increased incidence of bacteremia due to MRSA. The most common identified source was the urinary tract (18% of all episodes) but for 17 (44%) episodes, no focus was identified. Hospital mortality was 28% with all deaths occurring within 15 days of admission. Analysis of the MRSA strains by pulsed-field gel electrophoresis revealed that two pulsed-field types predominated when compared with the CDC national database: USA100- (N = 13) and USA 800-like strains (N = 7).

CONCLUSIONS

In the study population there was a substantial increase in incidence of SAB over a 7-year period due almost exclusively to an increased occurrence of MRSA. Hospital strains of MRSA predominated, as one would expect. Mortality was high but complications were low among survivors. These findings have important implications for choosing empiric antibiotic therapy in nursing home residents who have suspected S. aureus infection.

Course and outcome of Staphylococcus aureus bacteraemia: a retrospective analysis of 308 episodes in a Swiss tertiary-care centre

Staphylococcus aureus bacteraemia (SAB) is associated with substantial morbidity and mortality worldwide. The charts of adult patients with SAB who were hospitalised in a Swiss tertiary-care centre between 1998 and 2002 were studied retrospectively. In total, 308 episodes of SAB were included: 2% were caused by methicillin-resistant strains; 49% were community-acquired; and 51% were nosocomial. Bacteraemia without focus was the most common type of community-acquired SAB (52%), whereas intravenous catheter-related infection predominated (61%) among nosocomial episodes of SAB. An infectious diseases (ID) specialist was consulted in 82% of all cases; 83% received appropriate antibiotic treatment within 24 h of obtaining blood cultures. Overall hospital-associated mortality was 20%. Community-acquired SAB was associated independently with a higher mortality rate than nosocomial SAB (26% vs. 13%; p 0.009). Independent risk-factors for a fatal outcome were age (p < 0.001), immunosuppression (p 0.007), alcoholism (p < 0.001), haemodialysis (p 0.03), acute renal failure (p < 0.001) and septic shock (p < 0.001). Consultation with an ID specialist was associated with a better outcome in univariate analysis (p < 0.001). Compared with a previous retrospective analysis performed at the same institution between 1980 and 1986, there was a 140% increase in community-acquired SAB, a 60% increase in catheter-related SAB, and a 14% reduction in mortality. In conclusion, mortality in patients with SAB remained high, despite effective antibiotic therapy. Patients with community-acquired SAB were twice as likely to die as patients with nosocomial SAB. Consultation with an ID specialist may reduce mortality in patients with SAB.

Fatal central venous catheter-related infection in haemophilia

Central venous catheters (CVC) are frequently used in children with haemophilia to deliver factor infusions for the treatment or prophylaxis of bleeding. Complications of CVCs in patients with haemophilia include thrombosis and infection. We report a young boy with severe haemophilia A and an inhibitor who developed disseminated Staphylococcus aureus infection most likely related to a CVC. To our knowledge, this is the first reported case of fatal sepsis secondary to a CVC in a patient with haemophilia.

Infective endocarditis and acute purulent pericarditis in a patient with hyperglycemia

A diabetic patient was admitted to our hospital for infective endocarditis with acute purulent pericarditis and diabetic ketoacidosis. Echocardiography revealed attachment of vegetation to the chordae tendineae in the left ventricle and pericaridial effusion. The vegetation was enlarged and pendulated for a few days despite maximal antimicrobial therapy. Surgical resection was desirable to decrease the risk of embolic complications and cardiovascular collapse. We could not open the heart because of accumulation of purulent pericardial fluid, and right renal infarction was complicated. We believe that the immunocompromised and hypercoagulable state due to diabetes caused these conditions.