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

Bacteriophage Tail Proteins as a Tool for Bacterial Pathogen Recognition-A Literature Review

In recent years, a number of bacterial detection methods have been developed to replace time-consuming culture methods. One interesting approach is to mobilize the ability of phage tail proteins to recognize and bind to bacterial hosts. In this paper, the authors provide an overview of the current methodologies in which phage proteins play major roles in detecting pathogenic bacteria. Authors focus on proteins capable of recognizing highly pathogenic strains, such as Acinetobacter baumannii, Campylobacter spp., Yersinia pestis, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, Enterococcus spp., Salmonella spp., and Shigella. These pathogens may be diagnosed by capture-based detection methods involving the use of phage protein-coated nanoparticles, ELISA (enzyme-linked immunosorbent assay)-based methods, or biosensors. The reviewed studies show that phage proteins are becoming an important diagnostic tool due to the discovery of new phages and the increasing knowledge of understanding the specificity and functions of phage tail proteins.

The Effectiveness of Combination Therapy for Treating Methicillin-Susceptible Staphylococcus aureus Bacteremia: A Systematic Literature Review and a Meta-Analysis

Background: This meta-analysis aims to evaluate the effectiveness of combination therapy for treating MSSA bacteremia. Methods: We searched Ovid MEDLINE, EMBASE, Cochrane CENTRAL, and clinicaltrials.gov for studies including adults with MSSA bacteremia. The monotherapy group used a first-line antibiotic active against MSSA and the combination group used a first-line antibiotic plus additional antibiotic/s. The primary outcome was all-cause mortality. Secondary outcomes included persistent bacteremia, duration of bacteremia, relapse, and adverse events. Random-effects models with inverse variance weighting were used to estimate pooled risk ratios (pRR). Heterogeneity was assessed using the I² value and the Cochrane’s Q statistic. Results: A total of 12 studies (6 randomized controlled trials [RCTs]) were included. Combination therapy did not significantly reduce 30-day mortality (pRR 0.92, 95% CI, 0.70–1.20), 90-day mortality (pRR 0.89, 95% CI, 0.74–1.06), or any-time mortality (pRR 0.91, 95% CI, 0.76–1.08). Among patients with deep-seated infections, adjunctive rifampicin may reduce 90-day mortality (3 studies with moderate-high risk of bias; pRR 0.62, 95% CI, 0.42–0.92). For secondary outcomes, combination therapy decreased the risk of relapse (pRR 0.38, 95% CI, 0.22–0.66), but this benefit was not maintained when pooling RCTs (pRR 0.54, 95% CI, 0.12–2.51). Combination therapy was associated with an increased risk of adverse events (pRR 1.74, 95% CI, 1.31–2.31). Conclusions: Combination therapy not only did not decrease mortality in patients with MSSA bacteremia, but also increased the risk of adverse events. Combination therapy may reduce the risk of relapse, but additional high-quality studies are needed.

Risk of Staphylococcus aureus bacteraemia in patients with rheumatoid arthritis and the effect of orthopaedic implants on the risk: a nationwide observational cohort study

OBJECTIVE

It remains disputed how much the risk of Staphylococcus aureus bacteraemia (SAB) is increased in patients with rheumatoid arthritis (RA), and the extent to which orthopaedic implants explain the risk. We assessed SAB incidence rates (IRs) and incidence rate ratios (IRRs), comparing RA patients with a general population cohort (GPC) and individuals with versus without orthopaedic implants.

METHOD

Danish residents aged ≥ 18 years without prior RA or SAB (=GPC) were followed up for RA and microbiologically verified SAB events (1996-2017). IRRs were calculated by age- and sex-stratified Poisson regression adjusted for age, comorbidities, calendar year, and socioeconomic status.

RESULTS

The GPC comprised 5 398 690 individuals. We identified 33 567 incident RA patients (=RA cohort) (median follow-up 7.3 years, IQR 3.6-12.3). We observed 25 023 SAB events (n = 224 in the RA cohort). IRs per 100 000 person-years were 81.0 (RA cohort) and 29.9 (GPC). IRs increased with age. Adjusted IRRs in 18-59-year-old RA patients were 2.6 (95% confidence interval 1.8-3.7) for women and 1.8 (1.1-3.1) for men, compared with same sex and age group GPC. IRRs declined with age. Compared with the GPC without implants, IRRs for RA patients with implants ranged from 1.9 (1.3-2.8) (women ≥ 70 years) to 5.3 (2.2-12.8) (18-59-year-old men).

CONCLUSION

In this nationwide registry-based cohort study RA was a risk factor for SAB, and orthopaedic implants further increased the risk. Clinicians should be aware of potential SAB in patients with RA and orthopaedic implants.

Clinical prediction scores and the utility of time to blood culture positivity in stratifying the risk of infective endocarditis in Staphylococcus aureus bacteraemia

Background

Infective endocarditis (IE) complicates up to a quarter of Staphylococcus aureus bacteraemia (SAB) cases. Risk scores predict IE complicating SAB but have undergone limited external validation, especially in community-acquired infections and those who use IV drugs. Addition of the time to positive culture (TTP) may provide incremental risk prognostication.

Objectives

To externally validate risk scores for predicting IE in SAB and assess the incremental value of TTP.

Methods

The modified Duke score was calculated for adults hospitalized with SAB at a major tertiary institution. All patients underwent echocardiography. Sensitivity and specificity of the risk scores for predicting IE were calculated, and the incremental value of TTP was assessed.

Results

One hundred and six cases were analysed and 18 (17%) met definite IE criteria. The optimal TTP to predict IE was 11.5 h (sensitivity 88.9%; specificity 71.6%). The sensitivity of VIRSTA and PREDICT (Predicting risk of endocarditis using a clinical tool) were similar (94.4% for both) and higher than POSITIVE (Prediction Of Staphylococcus aureus Infective endocarditis Time to positivity, IV drug use, Vascular phenomena, pre-Existing heart condition; 77.8%). The receiver-operator characteristic AUCs were VIRSTA 0.83, PREDICT 0.75, POSITIVE 0.89 and TTP 0.85. Adding TTP to VIRSTA (i.e. VIRSTA+) resulted in the highest AUC (0.90), sensitivity (100%) and negative predictive value (100%), albeit with a low specificity (33%).

Conclusions

The VIRSTA and POSITIVE scores were the strongest predictors for IE complicating SAB. The addition of TTP to VIRSTA (VIRSTA+) significantly improved discriminatory value and may be safely used to rationalize echocardiography strategies.

Incidence of Monomicrobial Staphylococcus aureus Bacteremia: A Population-Based Study in Olmsted County, Minnesota – 2006 to 2020

Background

Population-based studies of Staphylococcus aureus bacteremia (SAB) in the United States are limited. We provide a contemporary evaluation of SAB incidence in Olmsted County, Minnesota, from 2006 to 2020.

Methods

This was a retrospective population-based study of all adult patients with SAB residing in Olmsted County from 1 January 2006 through 31 December 2020. Initial episodes of SAB were identified using the microbiology laboratory databases at both Olmsted Medical Center and Mayo Clinic Rochester.

Results

Overall, 541 incident SAB cases were identified with a median age of 66.8 (interquartile range, 54.4–78.5) years, and 60.4% were male. Among these cases, 298 (56.2%) were due to methicillin-susceptible S aureus (MSSA) and 232 (43.8%) cases of methicillin-resistant S aureus (MRSA). The overall age- and sex-adjusted SAB incidence rate (IR) was 33.9 (95% confidence interval [CI], 31.0–36.8) cases/100 000 person-years (PY). Males had a higher age-adjusted IR of 46.0 (95% CI, 41.0–51.0) cases/100 000 PY compared to females (IR, 24.4 [95% CI, 21.1–27.7] cases/100 000 PY). Age- and sex-adjusted SAB IRs due to MSSA and MRSA were 18.7 and 14.6 cases/100 000 PY, respectively, and the percentage of incident SAB cases due to MRSA fluctuated across the study period. There was no apparent temporal trend in SAB incidence over the study period (P = .093).

Conclusions

Our investigation represents the only contemporary population-based study in the United States. Despite the impression that SAB incidence may have increased based on Centers for Disease Control and Prevention surveillance data, our finding of no change in SAB incidence was somewhat unanticipated.

Whole genome sequencing and molecular epidemiology of pediatric Staphylococcus aureus bacteremia

BACKGROUND

The role Staphylococcus aureus antimicrobial resistance genes and toxins play in disease severity, management and outcome in childhood is an emerging field requiring further exploration.

METHODS

A prospective multi-site study of Australian and New Zealand children hospitalized with S. aureus bacteremia (SAB), occurred over 24-months (2017-2018). Whole genome sequencing (WGS) data was paired with clinical information from the ISAIAH cohort.

RESULTS

353 SAB isolates were sequenced; 85% methicillin-susceptible S. aureus ([MSSA], 301/353); 15% methicillin-resistant S. aureus ([MRSA], 52/353). There were 92 sequence types (STs), most commonly; ST5 (18%) and ST30 (8%), grouped into 23 clonal complexes (CCs), most frequently CC5 (21%) and CC30 (12%). MSSA comprised the majority of healthcare-associated SAB (87%, 109/125), with principal clones CC15 (48%, 11/21) and CC8 (33%, 7/21). Panton Valentine Leukocidin (PVL)-positive SAB occurred in 22% (76/353); predominantly MSSA (59%, 45/76), community-onset (92%, 70/76) infections. For community-onset SAB, the only microbiological independent predictor of poor outcomes was PVL-positivity (aOR 2.6 [CI 1.0-6.2]).

CONCLUSION

From this WGS pediatric SAB data, we demonstrate the previously under-recognized role MSSA has in harboring genetic virulence and causing healthcare-associated infections. PVL-positivity was the only molecular independent predictor of poor outcomes in children. These findings underscore the need for further research to define the potential implications PVL-producing strains may have on approaches to S. aureus clinical management.

Staphylococcus aureus adaptive evolution: Recent insights on how immune evasion, immunometabolic subversion and host genetics impact vaccine development

Despite meritorious attempts, a S. aureus vaccine that prevents infection or mitigates severity has not yet achieved efficacy endpoints in prospective, randomized clinical trials. This experience underscores the complexity of host-S. aureus interactions, which appear to be greater than many other bacterial pathogens against which successful vaccines have been developed. It is increasingly evident that S. aureus employs strategic countermeasures to evade or exploit human immune responses. From entering host cells to persist in stealthy intracellular reservoirs, to sensing the environmental milieu and leveraging bacterial or host metabolic products to reprogram host immune responses, S. aureus poses considerable challenges for the development of effective vaccines. The fact that this pathogen causes distinct types of infections and can undergo transient genetic, transcriptional or metabolic adaptations in vivo that do not occur in vitro compounds challenges in vaccine development. Notably, the metabolic versatility of both bacterial and host immune cells as they compete for available substrates within specific tissues inevitably impacts the variable repertoire of gene products that may or may not be vaccine antigens. In this respect, S. aureus has chameleon phenotypes that have alluded vaccine strategies thus far. Nonetheless, a number of recent studies have also revealed important new insights into pathogenesis vulnerabilities of S. aureus. A more detailed understanding of host protective immune defenses versus S. aureus adaptive immune evasion mechanisms may offer breakthroughs in the development of effective vaccines, but at present this goal remains a very high bar. Coupled with the recent advances in human genetics and epigenetics, newer vaccine technologies may enable such a goal. If so, future vaccines that protect against or mitigate the severity of S. aureus infections are likely to emerge at the intersection of precision and personalized medicine. For now, the development of S. aureus vaccines or alternative therapies that reduce mortality and morbidity must continue to be pursued.

Infective Endocarditis Caused by Staphylococcus aureus After Transcatheter Aortic Valve Replacement

BACKGROUND

Staphylococcus aureus (SA) has been extensively studied as causative microorganism of surgical prosthetic-valve infective endocarditis (IE). However, scarce evidence exists on SA IE after transcatheter aortic valve replacement (TAVR).

METHODS

Data were obtained from the Infectious Endocarditis After TAVR International Registry, including patients with definite IE after TAVR from 59 centres in 11 countries. Patients were divided into 2 groups according to microbiologic etiology: non-SA IE vs SA IE.

RESULTS

SA IE was identified in 141 patients out of 573 (24.6%), methicillin-sensitive SA in most cases (115/141, 81.6%). Self-expanding valves were more common than balloon-expandable valves in patients presenting with early SA IE. Major bleeding and sepsis complicating TAVR, neurologic symptoms or systemic embolism at admission, and IE with cardiac device involvement (other than the TAVR prosthesis) were associated with SA IE (P < 0.05 for all). Among patients with IE after TAVR, the likelihood of SA IE increased from 19% in the absence of those risk factors to 84.6% if ≥ 3 risk factors were present. In-hospital (47.8% vs 26.9%; P < 0.001) and 2-year (71.5% vs 49.6%; P < 0.001) mortality rates were higher among patients with SA IE vs non-SA IE. Surgery at the time of index SA IE episode was associated with lower mortality at follow-up compared with medical therapy alone (adjusted hazard ratio 0.46, 95% CI 0.22-0.96; P = 0.038).

CONCLUSIONS

SA IE represented approximately 25% of IE cases after TAVR and was associated with very high in-hospital and late mortality. The presence of some features determined a higher likelihood of SA IE and could help to orientate early antibiotic regimen selection. Surgery at index SA IE was associated with improved outcomes, and its role should be evaluated in future studies.

Epidemiological and clinical features of Panton-Valentine Leukocidin positive Staphylococcus aureus bacteremia: A case-control study

BACKGROUND

Panton-Valentine Leukocidin (PVL) toxin in Staphylococcus aureus has been associated with both severe pneumonia and skin and soft tissue infections. However, there are only limited data on how this virulence factor may influence the clinical course or complications of bacteremic S. aureus infections.

METHODS

Between September 2016 and March 2018, S. aureus isolates from clinical cultures from hospitals in an academic medical center underwent comprehensive genomic sequencing. Four hundred sixty-nine (29%) of 1681 S. aureus sequenced isolates were identified as containing the genes that encode for PVL. Case patients with one or more positive blood cultures for PVL were randomly matched with control patients having positive blood cultures with lukF/lukS-PV negative (PVL strains from a retrospective chart review).

RESULTS

51 case and 56 control patients were analyzed. Case patients were more likely to have a history of injection drug use, while controls more likely to undergo hemodialysis. Isolates from 78.4% of case patients were methicillin resistant as compared to 28.6% from control patients. Case patients had a higher incidence of pneumonia and skin and soft tissue infection and longer duration of fever without differences in length of bacteremia. Clinical cure or expiration was comparable.

CONCLUSIONS

These results are consistent with prior observations associating the PVL toxin with both community-acquired MRSA strains as well as severe staphylococcal pneumonia. The presence of the PVL toxin does not appear to otherwise influence the natural history of bacteremic S. aureus disease other than in prolonging the duration of fever.

Bloodstream Infection and Endocarditis Caused by Staphylococcus aureus in Patients with Cancer: A Multicenter Cohort Study

INTRODUCTION

In a large cohort of patients with Staphylococcus aureus bloodstream infection (SABSI), we aimed to analyze the incidence and risk factors for infective endocarditis (IE) among patients with active cancer (PAC) in comparison with those without cancer (PWC).

METHODS

Multicenter cohort study of patients with SABSI admitted to two tertiary care hospitals, from 2011 to 2019. PAC were defined as those with an active solid organ cancer or hematological malignancies. SABSI and S. aureus IE were compared between PAC and PWC.

RESULTS

Among 978 episodes of SABSI, 217 (22.2%) occurred in PAC. PAC were younger, had fewer comorbidities, carried cardiac devices less often, and had less community-acquired SABSI than PWC. Compared to PWC, PAC more frequently had catheter-related SABSI, less IE (2.8% vs 10.9%, p < 0.001) and osteoarticular infection (2.3% vs 14.3%, p < 0.001). Independent risk factors for IE were cardiopathy (aOR 4.392, 95% CI 2.719-7.094) and persistent bacteremia (aOR 3.545, 95% CI 2.159-5.820). Thirty-day mortality was high, and similar between groups (24.2% vs 25.5%, p = 0.282).

CONCLUSIONS

PAC with SABSI developed IE less frequently than PWC did. This finding seems related to the differences in baseline characteristics and may have significant clinical implications, such as transesophageal echocardiography in PAC without cardiopathy or persistent bacteremia.

Synergism of a Novel 1,2,4-oxadiazole-containing Derivative with Oxacillin against Methicillin-Resistant Staphylococcus aureus

Staphylococcusaureus is an important opportunistic pathogen that causes many infections in humans and animals. The inappropriate use of antibiotics has favored the diffusion of methicillin-resistant S. aureus (MRSA), nullifying the efforts undertaken in the discovery of antimicrobial agents. Oxadiazole heterocycles represent privileged scaffolds for the development of new drugs because of their unique bioisosteric properties, easy synthesis, and therapeutic potential. A vast number of oxadiazole-containing derivatives have been discovered as potent antibacterial agents against multidrug-resistant MRSA strains. Here, we investigate the ability of a new library of oxadiazoles to contrast the growth of Gram-positive and Gram-negative strains. The strongest antimicrobial activity was obtained with compounds 3 (4 µM) and 12 (2 µM). Compound 12, selected for further evaluation, was found to be noncytotoxic on the HaCaT cell line up to 25 µM, bactericidal, and was able to improve the activity of oxacillin against the MRSA. The highest synergistic interaction was obtained with the combination values of 0.78 μM for compound 12, and 0.06 μg/mL for oxacillin. The FIC index value of 0.396 confirms the synergistic effect of compound 12 and oxacillin. MRSA treatment with compound 12 reduced the expression of genes included in the mec operon. In conclusion, 12 inhibited the growth of the MRSA and restored the activity of oxacillin, thus resulting in a promising compound in the treatment of MRSA infection.

Impact of a pharmacist-facilitated, evidence-based bundle initiative on Staphylococcus aureus bacteremia management

OBJECTIVE

To evaluate a pharmacist-facilitated evidence-based bundle (EBB) initiative with infectious disease consultation (IDC) for Staphylococcus aureus bacteremia (SAB).

METHODS

This was a before-and-after quasi-experimental study of adult patients with SAB before and after the pharmacist-facilitated EBB initiative, which included IDC, timely definitive antibiotics, source control, echocardiography, and repeat blood cultures.

RESULTS

Ninety and 111 patients were included in pre- and post-intervention cohorts, respectively. We observed significant increases in adherence to all 5 (4.4% vs 68.5%, P < 0.001) and 4 (10.0% vs 76.6%, P < 0.001) EBB elements. Time to definitive antibiotics (48 vs 16 hours, P < 0.001), time to IDC (43.5 vs 32 hours, P < 0.001), SAB duration (95 vs 66 hours, P = 0.009), persistent SAB (18.9% vs 9.0%, P = 0.041), and length of stay (14 vs 13 days, P = 0.027) also improved. No statistically significant differences for SAB-related readmission or all-cause mortality were observed.

CONCLUSIONS

Our pharmacist-facilitated SAB initiative was associated with improved EBB adherence and clinical outcomes.

Low Diversity in Nasal Microbiome Associated With Staphylococcus aureus Colonization and Bloodstream Infections in Hospitalized Neonates

BACKGROUND

Staphylococcus aureus is a leading cause of infectious morbidity and mortality in neonates. Few data exist on the association of the nasal microbiome and susceptibility to neonatal S. aureus colonization and infection.

METHODS

We performed 2 matched case-control studies (colonization cohort-neonates who did and did not acquire S. aureus colonization; bacteremia cohort-neonates who did [colonized neonates] and did not [controls] acquire S. aureus colonization and neonates with S. aureus bacteremia [bacteremic neonantes]). Neonates in 2 intensive care units were enrolled and matched on week of life at time of colonization or infection. Nasal samples were collected weekly until discharge and cultured for S. aureus, and the nasal microbiome was characterized using 16S rRNA gene sequencing.

RESULTS

In the colonization cohort, 43 S. aureus-colonized neonates were matched to 82 controls. At 1 week of life, neonates who acquired S. aureus colonization had lower alpha diversity (Wilcoxon rank-sum test P < .05) and differed in beta diversity (omnibus MiRKAT P = .002) even after adjusting for birth weight (P = .01). The bacteremia cohort included 10 neonates, of whom 80% developed bacteremia within 4 weeks of birth and 70% had positive S. aureus cultures within a few days of bacteremia. Neonates with bacteremia had an increased relative abundance of S. aureus sequences and lower alpha diversity measures compared with colonized neonates and controls.

CONCLUSIONS

The association of increased S. aureus abundance and decrease of microbiome diversity suggest the need for interventions targeting the nasal microbiome to prevent S. aureus disease in vulnerable neonates.

Population-Based Study of Bloodstream Infection Incidence and Mortality Rates, Finland, 2004-2018

A 2-fold increase in incidence and death during this period emphasizes the need for additional prevention efforts.

We evaluated the incidence, outcomes, and causative agents of bloodstream infections (BSI) in Finland during 2004–2018 by using data from the national registries. We identified a total of 173,715 BSIs; annual incidence increased from 150 to 309 cases/100,000 population. BSI incidence rose most sharply among persons >80 years of age. The 1-month case-fatality rate decreased from 13.0% to 12.6%, but the 1-month all-cause mortality rate rose from 20 to 39 deaths/100,000 population. BSIs caused by Escherichia coli increased from 26% to 30% of all BSIs. BSIs caused by multidrug-resistant microbes rose from 0.4% to 2.8%, mostly caused by extended-spectrum β-lactamase-producing E. coli. We observed an increase in community-acquired BSIs, from 67% to 78%. The proportion of patients with severe underlying conditions rose from 14% to 23%. Additional public health and healthcare prevention efforts are needed to curb the increasing trend in community-acquired BSIs and antimicrobial drug–resistant E. coli.

Staphylococcus aureus Bacteremia in Hospitalized Patients and Associated Factors: A Cross-sectional Study from Mashhad, Iran

Background: Staphylococcus aureus is an important cause of resistant infection with high mortality and morbidity. Objectives: We aimed to evaluate the clinical characteristics and comorbidities of patients with S. aureus infection to define the predictors of adverse outcomes. Methods: In this cross-sectional study, patients (aged ≥ 15 years) with positive S. aureus blood cultures were included. Their demographic and clinical characteristics were recorded, and their association with the main adverse outcomes (methicillin-resistant S. aureus [MRSA], infective endocarditis, source of infection, and the final outcome were analyzed using SPSS software version 16. Results: The male-to-female ratio was 54/51. The mean age was 55.13 years (women: 58.45 ± 20.4 and men: 53.6 ± 17.6). Of 105 cases analyzed, 40% had hospital-, 25.7% community-, and 34.3% healthcare-associated bacteremia. The median duration of hospital admission was 13 days. Thirty-two percent had MRSA, differently based on the source of infection (P = 0.029). Twenty-eight patients had infective endocarditis, differently based on the source of infection, prosthetics, considerable foci of infection, and receipt of blood and its derivatives (P < 0.05). Most patients with neurological and end-stage renal disease (both P = 0.001) did not have infective endocarditis. Finally, 61.9% of the patients were discharged with good condition, 38.1% died, and 9% left the hospital before diagnosis of the foci. Conclusions: Vascular catheters and cardiovascular diseases, including hypertension, are among the most common factors associated with S. aureus bacteremia, and it is necessary to carefully examine the presence of these factors, as well as infective endocarditis in these patients.

Increasing incidence and antimicrobial resistance in Escherichia coli bloodstream infections: a multinational population-based cohort study

BACKGROUND

Escherichia coli is an important pathogen in humans and is the most common cause of bacterial bloodstream infections (BSIs). The objectives of our study were to determine factors associated with E. coli BSI incidence rate and third-generation cephalosporin resistance in a multinational population-based cohort.

METHODS

We included all incident E. coli BSIs (2014-2018) from national (Finland) and regional (Australia [Canberra], Sweden [Skaraborg], and Canada [Calgary, Sherbrooke, and western interior]) surveillance. Incidence rates were directly age and sex standardized to the European Union 28-country 2018 population. Multivariable negative binomial and logistic regression models estimated factors significantly associated with E. coli BSI incidence rate and third-generation cephalosporin resistance, respectively. The explanatory variables considered for inclusion in both models were year (2014-2018), region (six areas), age (< 70-years-old and ≥ 70-years-old), and sex (female and male).

RESULTS

We identified 31,889 E. coli BSIs from 40.7 million person-years of surveillance. Overall and third-generation cephalosporin-resistant standardized rates were 87.1 and 6.6 cases/100,000 person-years, respectively, and increased 14.0% and 40.1% over the five-year study. Overall, 7.8% (2483/31889) of E. coli BSIs were third-generation cephalosporin-resistant. Calgary, Canberra, Sherbrooke, and western interior had significantly lower E. coli BSI rates compared to Finland. The significant association between age and E. coli BSI rate varied with sex. Calgary, Canberra, and western interior had significantly greater odds of third-generation cephalosporin-resistant E. coli BSIs compared to Finland. Compared to 2014, the odds of third-generation cephalosporin-resistant E. coli BSIs were significantly increased in 2016, 2017, and 2018. The significant association between age and the odds of having a third-generation cephalosporin-resistant E. coli BSI varied with sex.

CONCLUSIONS

Increases in overall and third-generation cephalosporin-resistant standardized E. coli BSI rates were clinically important. Overall, E. coli BSI incidence rates were 40-104% greater than previous investigations from the same study areas. Region, sex, and age are important variables when analyzing E. coli BSI rates and third-generation cephalosporin resistance in E. coli BSIs. Considering E. coli is the most common cause of BSIs, this increasing burden and evolving third-generation cephalosporin resistance will have an important impact on human health, especially in aging populations.

Clinical Utility of Molecular Tests for Guiding Therapeutic Decisions in Bloodstream Staphylococcal Infections: A Meta-Analysis

Background: Treatment of bloodstream staphylococcal infections (BSI) necessitates the prompt initiation of appropriate antimicrobial agents and the rapid de-escalation of excessive broad-spectrum coverage to reduce the risk of mortality. We, therefore, aimed to demonstrate the diagnostic accuracy of nucleic acid amplification tests (NAAT) for the identification of methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) in clinically suspected patients. Methods: Until November 23, 2020, databases including PubMed, Scopus, Embase, and Web of Science were scanned for eligible studies. A bivariate random-effects model was used for meta-analysis of the 33 included studies obtained from 1606 citations, and pooled summary estimates with 95% confidence intervals (CI) were generated. Results: Twenty-three studies (n = 8,547) assessed NAAT accuracy for MSSA detection, while three studies (n = 479) evaluated MRSA detection in adults. The pooled NAAT sensitivity and specificity for MRSA in adults was higher [sensitivity: 0.83 (95% CI 0.59-0.96), specificity: 0.99 (95% CI 0.98-1.0)] as compared to MSSA [sensitivity: 0.76 (95% CI 0.69-0.82), specificity: 0.98 (95% CI 0.98-0.99)]. Similarly, eight studies (n = 4,089) investigating MSSA in pediatric population reported higher NAAT accuracy [sensitivity: 0.89 (95% CI 0.76-0.96), specificity: 0.98 (95% CI 0.97-0.98)] compared to adults. Among NAA tests, SeptiFast (real-time PCR, commercial) was frequently applied, and its diagnostic accuracy corresponded well to the overall summary estimates. A meta-regression and subgroup analysis of study design, sample condition, and patient selection method could not explain the heterogeneity (P > 0.05) in the diagnostic efficiency. Conclusions: NAAT could be applied as the preferred initial tests for timely diagnosis and BSI management.

Ward-level factors associated with methicillin-resistant Staphylococcus aureus acquisition-an electronic medical records study in Singapore

Background

Methicillin-Resistant Staphylococcus aureus (MRSA) is endemic in hospitals worldwide. Intrahospital transfers may impact MRSA acquisition risk experienced by patients. In this study, we investigated ward characteristics and connectivity that are associated with MRSA acquisition.

Methods

We analysed electronic medical records on patient transfers and MRSA screening of in-patients at an acute-care tertiary hospital in Singapore to investigate whether ward characteristics and connectivity within a network of in-patient wards were associated with MRSA acquisition rates over a period of four years.

Results

Most patient transfers concentrated in a stable core network of wards. Factors associated with increased rate of MRSA acquisition were MRSA prevalence among patients transferred from other wards (rate ratio (RR): 7.74 [95% confidence interval (CI): 3.88, 15.44], additional 5 percentage point), critical care ward (RR: 1.72 [95% CI: 1.09, 2.70]) and presence of MRSA cohorting beds (RR: 1.39 [95% CI: 1.03, 1.90]. Oncology ward (RR: 0.66 [95% CI: 0.46, 0.94]) (compared to medical ward), and median length of stay (RR: 0.70 [95% CI: 0.55, 0.90], additional 1.5 days) were associated with lower acquisition rates. In addition, we found evidence of interaction between MRSA prevalence among patients transferred from other wards and weighted in-degree although the latter was not associated with MRSA acquisition after controlling for confounders.

Conclusion

Wards with higher MRSA prevalence among patients transferred from other wards were more likely to have higher MRSA acquisition rate. Its effect further increased in wards receiving greater number of patients. In addition, critical care ward, presence of MRSA cohorting beds, ward specialty, and median length of stay were associated with MRSA acquisition.

Mortality in Escherichia coli bloodstream infections: a multinational population-based cohort study

Background

Escherichia coli is the most common cause of bloodstream infections (BSIs) and mortality is an important aspect of burden of disease. Using a multinational population-based cohort of E. coli BSIs, our objectives were to evaluate 30-day case fatality risk and mortality rate, and determine factors associated with each.

Methods

During 2014–2018, we identified 30-day deaths from all incident E. coli BSIs from surveillance nationally in Finland, and regionally in Sweden (Skaraborg) and Canada (Calgary, Sherbrooke, western interior). We used a multivariable logistic regression model to estimate factors associated with 30-day case fatality risk. The explanatory variables considered for inclusion were year (2014–2018), region (five areas), age (< 70-years-old, ≥70-years-old), sex (female, male), third-generation cephalosporin (3GC) resistance (susceptible, resistant), and location of onset (community-onset, hospital-onset). The European Union 28-country 2018 population was used to directly age and sex standardize mortality rates. We used a multivariable Poisson model to estimate factors associated with mortality rate, and year, region, age and sex were considered for inclusion.

Results

From 38.7 million person-years of surveillance, we identified 2961 30-day deaths in 30,923 incident E. coli BSIs. The overall 30-day case fatality risk was 9.6% (2961/30923). Calgary, Skaraborg, and western interior had significantly increased odds of 30-day mortality compared to Finland. Hospital-onset and 3GC-resistant E. coli BSIs had significantly increased odds of mortality compared to community-onset and 3GC-susceptible. The significant association between age and odds of mortality varied with sex, and contrasts were used to interpret this interaction relationship. The overall standardized 30-day mortality rate was 8.5 deaths/100,000 person-years. Sherbrooke had a significantly lower 30-day mortality rate compared to Finland. Patients that were either ≥70-years-old or male both experienced significantly higher mortality rates than those < 70-years-old or female.

Conclusions

In our study populations, region, age, and sex were significantly associated with both 30-day case fatality risk and mortality rate. Additionally, 3GC resistance and location of onset were significantly associated with 30-day case fatality risk. Escherichia coli BSIs caused a considerable burden of disease from 30-day mortality. When analyzing population-based mortality data, it is important to explore mortality through two lenses, mortality rate and case fatality risk.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06326-x.

Prospective surveillance for invasive Staphylococcus aureus and group A Streptococcus infections in a setting with high community burden of scabies and impetigo

BACKGROUND

Invasive Staphylococcus aureus (iSA) and group A Streptococcus (iGAS) impose significant health burdens globally. Both bacteria commonly cause skin and soft tissue infections (SSTIs), which can result in invasive disease. Understanding of the incidence of iSA and iGAS remains limited in settings with a high SSTI burden.

METHODS

Prospective surveillance for admissions with iSA or iGAS was conducted at the referral hospital in Fiji's Northern Division over 48 weeks between July 2018 and June 2019.

RESULTS

There were 55 admissions for iSA and 15 admissions for iGAS (incidence 45.2 and 12.3 per 100,000 person-years, respectively). The highest incidence was found in patients aged ≥65 years (59.6 per 100,000 person-years for iSA and iGAS). The incidence of iSA was higher in indigenous Fijians (iTaukei) (71.1 per 100,000 person-years) compared with other ethnicities (incidence rate ratio 9.7, 95% confidence interval 3.5-36.9). SSTIs were found in the majority of cases of iSA (75%) and iGAS (53.3%). Thirteen of the 14 iGAS strains isolated belonged to emm cluster D (n = 5) or E (n = 8). The case fatality rate was high for both iSA (10.9%) and iGAS (33.3%).

CONCLUSIONS

The incidence of iSA and iGAS in Fiji is very high. SSTIs are common clinical foci for both iSA and iGAS. Both iSA and iGAS carry a substantial risk of death. Improved control strategies are needed to reduce the burden of iSA and iGAS in Fiji.

National database study of trends in bacteraemia aetiology among children and adults in Japan: a longitudinal observational study

OBJECTIVES

Domestic epidemiological studies are needed to ascertain the disease burden of bacteraemia in individual countries. This study aimed to evaluate the domestic trends in paediatric and adult bacteraemia in Japan.

SETTING

Laboratory-based surveillance was used to obtain data from 592 hospitals located throughout Japan.

PARTICIPANTS

The study was conducted using the results of 827 780 and 3 512 524 blood culture tests obtained from children and adults, respectively, between January 2010 and December 2016.

OUTCOME MEASURES

We analysed the temporal trends in specific bacterial species (Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, Escherichia coli, Klebsiella pneumoniae, Salmonella enterica, Haemophilus influenzae, Listeria monocytogenes and Neisseria meningitidis) detected from the blood cultures of children and adults. For children aged ≤2 years, the data were analysed for each year of age. The proportions of bacteraemia-positive results among the patients were also evaluated.

RESULTS

The number of bacteraemia-positive samples over the study period was 47,125/827,855 (5.7%) in children and 959,765/3,513,885 (27.3%) in adults. S. pneumoniae was the most frequent cause of bacteraemia in children in 2010. However, after 2011, S. aureus bacteraemia was the most frequent, followed by S. pneumoniae and E. coli. E. coli bacteraemia showed significant increases in both children and adults. In children, S. pneumoniae and H. influenzae bacteraemia decreased from 2010 to 2013. However, S. pneumoniae bacteraemia case numbers stabilised from 2013, whereas H. influenzae bacteraemia cases continued to decrease until 2016.

CONCLUSION

The results suggest that the introduction of the 13-valent pneumococcal conjugate vaccine did not substantially affect disease occurrence. In contrast to the decreasing trends in H. influenzae and S. pneumoniae bacteraemia, S. aureus, E. coli and S. agalactiae bacteraemia showed increasing trends. These findings shed light on recent temporal trends in bacteraemia in both children and adults in Japan.

Correlations of Host and Bacterial Characteristics with Clinical Parameters and Survival in Staphylococcus aureus Bacteremia

Staphylococcus aureus bacteremia (SAB) is a frequent, severe condition that occurs in patients of all age groups and affects clinical departments of all medical fields. It is associated with a high mortality rate of 20-30%. In this study, we analyzed patient mortality associated with SAB at our tertiary care university hospital, assessed the clinical management in terms of administered antimicrobial therapy, and determined which factors have an impact on the clinical course and outcome of patients with this disease. We collected clinical data and blood culture isolates of 178 patients diagnosed with SAB between May 2013 and July 2015. For this study, bacteria were cultured and analyzed concerning their phenotype, hemolysis activity, biofilm formation, nuclease activity, prevalence of toxin genes, spa and agr type. Overall mortality was 24.2% and 30-day mortality was 14.6%. Inadequate initial therapy was administered to 26.2% of patients and was associated with decreased survival (p = 0.041). Other factors associated with poor survival were patient age (p = 0.003), agr type 4 (p ≤ 0.001) and pathological leukocyte counts (p = 0.029 if elevated and p = 0.003 if lowered). The type of infection focus, spa clonal complex and enterotoxin genes seg and sei had an impact on severity of inflammation. Our results indicate that mortality and burden of disease posed by SAB are high at our university hospital.

The Prevalence, Risk, and Management of Methicillin-Resistant Staphylococcus aureus Infection in Diverse Populations across Canada: A Systematic Review

Methicillin-resistant Staphylococcus aureus (MRSA) first emerged after methicillin was introduced to combat penicillin resistance, and its prevalence in Canada has increased since the first MRSA outbreak in the early 1980s. We reviewed the existing literature on MRSA prevalence in Canada over time and in diverse populations across the country. MRSA prevalence increased steadily in the 1990s and 2000s and remains a public health concern in Canada, especially among vulnerable populations, such as rural, remote, and Indigenous communities. Antibiotic resistance patterns and risk factors for MRSA infection were also reported. All studies reported high susceptibility (>85%) to trimethoprim-sulfamethoxazole, with no significant resistance reported for vancomycin, linezolid, or rifampin. While MRSA continues to have susceptibility to several antibiotics, the high and sometimes variable resistance rates to other drugs underscores the importance of antimicrobial stewardship. Risk factors for high MRSA infection rates related to infection control measures, low socioeconomic status, and personal demographic characteristics were also reported. Additional surveillance, infection control measures, enhanced anti-microbial stewardship, and community education programs are necessary to decrease MRSA prevalence and minimize the public health risk posed by this pathogen.

Management of Staphylococcus aureus Bloodstream Infections

Staphylococcus aureus bloodstream infections are associated with a high morbidity and mortality. Nevertheless, significance of a positive blood culture with this pathogen is often underestimated or findings are misinterpreted as contamination, which can result in inadequate diagnostic and therapeutic consequences. We here review and discuss current diagnostic and therapeutic key elements and open questions for the management of Staphylococcus aureus bloodstream infections.

Staphylococcus aureus bloodstream infection: Secular changes associated with the implementation of a de novo clinical infectious diseases service in a Canadian population

OBJECTIVE

To investigate the epidemiology of Staphylococcus aureus bloodstream infections (BSI) in a mixed rural to small city population and examine secular changes associated with the implementation of a regional clinical infectious diseases program.

METHODS

Population-based surveillance for incident S. aureus BSI was conducted in the western interior of British Columbia, Canada between April 2010 and March 2020. An infectious diseases service was progressively implemented starting in 2013.

RESULTS

581 incident S. aureus BSI were identified. There was an increasing incidence during the study and the overall age- and gender-adjusted annual rate was 32.9 per 100,000 population. Implementation of the infectious diseases program was associated with an increase in rates of blood culture sampling, documentation of persistent bacteremia, use of transthoracic and transesophageal echocardiography, and a reduction in cases of relapsed BSI. Infectious diseases consultation was independently associated with a reduced risk for death (odds ratio 0.5; 95% CI 0.3-0.9).

CONCLUSIONS

Although the implementation of a clinical infectious diseases service was associated with changes in management and improved outcome, S. aureus BSI still causes a major burden of illness.

Effect of the vancomycin minimum inhibitory concentration on clinical outcomes in patients with methicillin-susceptible Staphylococcus aureus bacteraemia: a systematic review and meta-analysis

OBJECTIVE

The use of the vancomycin minimum inhibitory concentration (MIC) as a prognostic predictor in patients with methicillin-susceptible Staphylococcus aureus (MSSA) has been debated in the last decade. We performed a systematic review and meta-analysis to investigate whether an elevated vancomycin MIC is associated with a worse prognosis for patients with MSSA bacteraemia.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, Embase and the Cochrane Library were searched from inception to December 2019.

ELIGIBILITY CRITERIA

Randomised controlled trials or observational studies were considered eligible if they provided clinical outcomes of patients with MSSA bacteraemia, stratified by vancomycin MIC.

DATA SYNTHESIS

Primary outcome was mortality. Secondary outcomes included septic thrombophlebitis, persistent bacteraemia and complicated bacteraemia. Pooled ORs and 95% CIs were calculated. Subgroup analyses included the susceptibility testing method.

RESULTS

Fifteen observational studies were included. Bacteraemia due to MSSA isolates with high vancomycin MICs was associated with higher mortality than isolates with low MICs (OR 1.44; 95% CI 1.12 to 1.84; I²=40.3%). Additionally, significantly greater septic thrombophlebitis (OR 3.16; 95% CI 1.11 to 9.00; I²=58.6%) and a trend towards more persistent bacteraemia (OR 1.79; 95% CI 0.97 to 3.31; I²=0%) were observed in patients with high vancomycin MICs than in patients with low MICs. Differences in complicated bacteraemia were not significant. Similar findings were obtained in subgroup analyses using Etest. However, significant differences in outcomes were not observed between the high and low vancomycin MICs detected using broth microdilution.

CONCLUSION

The available data suggest an association between elevated vancomycin MICs detected using Etest and adverse clinical outcomes for patients with MSSA bacteraemia. Future studies should validate these findings and explore the potential mechanisms.

PROSPERO REGISTRATION NUMBER

CRD42018090547.

Forgoing transesophageal echocardiogram in selected patients with complicated Staphylococcus aureus bacteremia

Infective endocarditis (IE) has been increasingly recognized as an important complication of Staphylococcus aureus bacteremia (SAB), leading to a low threshold for echocardiography and extended treatment with anti-staphylococcal agents. However, outside of IE, many indications for prolonged anti-staphylococcal therapy courses are present. We sought to determine the frequency in which findings from a transesophageal echocardiogram (TEE) changed clinical SAB management in a large Canadian health region. Residents (> 18 years) with SAB from 2012 to 2014 who underwent transthoracic echocardiogram (TTE) and TEE were assessed. Patients potentially benefiting from an extended course of anti-staphylococcal agents were defined a priori. Patient demographics, treatment (including surgical), and clinical outcomes were extracted and evaluated. Of the 705 episodes of SAB that underwent a screening echocardiogram, 203 episodes underwent both a TTE and TEE, of which 92.1% (187/203) contained an a priori indication for extended anti-staphylococcal therapy. Regardless of TEE results, actual duration of therapy did not differ in SAB episodes that had ≥ 1 extended anti-staphylococcal therapy criteria (36.7 days, IQR 23.4-48.6 vs. 43.8 days, IQR 33.3-49.5, p = 0.17). Additionally, there were no cases in which TEE was utilized as the sole reason to shorten duration of therapy or proceed to surgery for those with SAB. Routine performance of TEE may be unnecessary in all SAB as many patients have pre-existing indications for extended anti-staphylococcal therapy independent of TEE findings. An algorithm to selectively identify cases of SAB that would benefit from TEE can reduce resource and equipment expenditure and patient risks associated with TEE.

A retrospective analysis of community-onset bloodstream infections at a tertiary-care academic hospital in South Africa. Are current empiric antimicrobial practices appropriate?

Background:

Community-onset bloodstream infection (CO-BSI) is associated with substantial morbidity and mortality. Knowledge of locally prevalent pathogens and antimicrobial susceptibility patterns can promptly guide appropriate empiric therapy and improve outcomes.

Objectives:

We sought to determine the epidemiology of CO-BSI, the blood culture positivity rate and the contamination rate. We also sought to establish appropriateness of current empiric antimicrobial therapy practices.

Methods:

We retrospectively analyzed blood cultures taken from January 2015 to December 2019 at the emergency departments (EDs) of a tertiary-care academic hospital in South Africa using extracted laboratory data.

Results:

The overall positivity rate of blood cultures taken at the EDs was 15% (95% confidence interval [CI], 0.15–0.16) and the contamination rate was 7% (95% CI, 0.06–0.07). Gram-positive bacteria predominated in the pediatric cohort: neonates, 52 (54%) of 96; infants, 57 (52%) of 109; older children, 63 (61%) of 103. Methicillin-susceptible Staphylococcus aureus was the predominant pathogen among older children: 30 (35%) of 85. Escherichia coli was the most common pathogen isolated among adults and the elderly: 225 (21%) of 1,060 and 62 (29%) of 214, respectively. Among neonates, the susceptibility of E. coli and Klebsiella pneumoniae to the combination of ampicillin and gentamicin was 17 (68%) of 25. Among adults, the susceptibility of the 5 most common pathogens to amoxicillin-clavulanate was 426 (78%) of 546 and their susceptibility to ceftriaxone was 481 (85%) of 565 (P = .20). The prevalence of methicillin-resistant S. aureus, extended-spectrum β-lactamase–producing and carbapenem-resistant Enterobacterales were low among all age groups.

Conclusions:

Review of blood culture collection techniques is warranted to reduce the contamination rate. High rates of resistance to currently prescribed empiric antimicrobial agents for CO-BSI warrants a re-evaluation of local guidelines.

Longitudinal evaluation of risk factors and outcomes of blood stream infections due to Staphylococcus species in persons with HIV: An observational cohort study

BACKGROUND

Staphylococcal blood stream infections (SBSI) are a significant cause of morbidity and mortality, however there is little data on such infections in persons with HIV (PWH) in the combination antiretroviral therapy era, particularly when divided by species; methicillin-sensitive (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative Staphylococcus (CoNS).

METHODS

Using linked longitudinal clinical and microbiologic databases, all cases of SBSI in PWH accessing care at Southern Alberta Clinic were identified and demographic features and outcomes characterized. We compared participants with SBSI to those with no SBSI and determined the 1-year all-cause mortality following SBSI and longitudinally over the study period.

FINDINGS

From 2000 to 2018, 130 SBSI occurred in 95 PWH over 21,526 patient-years follow-up. MSSA caused 38.4%, MRSA 26.1% and CoNS 35.3% of SBSI. Highest risks for SSBI were in Hepatitis C coinfection, low CD4 nadir, Indigenous/Metis ethnicity and in persons who use injection drugs (PWID). During follow-up, 423 deaths occurred in all PWH. Mortality rates for PWH with SBSI was 74.9/1000 patient-years (95% CI 59.2-94.9) compared with no SBSI 16.0/1000 patient-years (95% CI 14.4-17.7). The mortality Hazard Ratio was 2.61(95% CI 1.95-3.49, P= <0.001) for SBSI compared to no SBSI, following adjusting for confounding. Seventy deaths occurred in persons with SBSI with 40% in the first year. Higher 1-year mortality rates occurred in hospital-acquired infections.

INTERPRETATION

Incidence rates of SBSI are high in PWH, with identified characteristics that further increase this risk. PWH who experience SBSI have a significant mortality risk within the first year of follow-up, however they also have greater long-term all-cause mortality compared to those with no SBSI. Further investigation is needed in PWH evaluating host, environment and pathogen differences that lead to differing rates of SBSI and mortality seen here.

FUNDING

No funding was received for this work.

Comprehensive Genomic Investigation of Adaptive Mutations Driving the Low-Level Oxacillin Resistance Phenotype in Staphylococcus aureus

Antistaphylococcal penicillins such as oxacillin are the key antibiotics in the treatment of invasive methicillin-susceptible Staphylococcus aureus (MSSA) infections; however, mec gene-independent resistance adaptation can cause treatment failure. Despite its clinical relevance, the basis of this phenomenon remains poorly understood. Here, we investigated the genomic adaptation to oxacillin at an unprecedented scale using a large collection of 503 clinical mec-negative isolates and 30 in vitro-adapted isolates from independent oxacillin exposures. By combining comparative genomics, evolutionary convergence, and genome-wide association analysis, we found 21 genetic loci associated with low-level oxacillin resistance, underscoring the polygenic nature of this phenotype. Evidence of adaptation was particularly strong for the c-di-AMP signal transduction pathways (gdpP and dacA) and in the clpXP chaperone-protease complex. The role of mutations in gdpP in conferring low-level oxacillin resistance was confirmed by allele-swapping experiments. We found that resistance to oxacillin emerges at high frequency in vitro (median, 2.9 × 10^-6; interquartile range [IQR], 1.9 × 10^-6 to 3.9 × 10^-6), which is consistent with a recurrent minimum inhibitory concentration (MIC) increase across the global phylogeny of clinical isolates. Nevertheless, adaptation in clinical isolates appears sporadically, with no stably adapted lineages, suggesting a high fitness cost of resistance, confirmed by growth assessment of mutants in rich media. Our data provide a broader understanding of the emergence and dynamics of oxacillin resistance adaptation in S. aureus and a framework for future surveillance of this clinically important phenomenon.IMPORTANCE The majority of Staphylococcus aureus strains causing human disease are methicillin-susceptible (MSSA) and can be treated with antistaphylococcal penicillins (such as oxacillin). While acquisition of the mec gene represents the main resistance mechanism to oxacillin, S. aureus can acquire low-level resistance through adaptive mutations in other genes. In this study, we used genomic approaches to understand the basis of S. aureus adaption to oxacillin and its dynamic at the population level. By combining a genome analysis of clinical isolates from persistent MSSA infections, in vitro selection of oxacillin resistance, and genome-wide association analysis on a large collection of isolates, we identified 21 genes linked to secondary oxacillin resistance. Adaptive mutations in these genes were easy to select when S. aureus was exposed to oxacillin, but they also came at a substantial cost in terms of bacterial fitness, suggesting that this phenotype emerges preferentially in the setting of sustained antibiotic exposure.

Adjuvant β-Lactam Therapy Combined with Vancomycin or Daptomycin for Methicillin-Resistant Staphylococcus aureus Bacteremia: a Systematic Review and Meta-analysis

Infections due to methicillin-resistant Staphylococcus aureus bacteremia (MRSAB) seriously threaten public health due to poor outcomes and high mortality. The objective of this study is to perform a systematic review and meta-analysis of the current evidence on adjuvant β-lactam (BL) therapy combined with vancomycin (VAN) or daptomycin (DAP) for MRSAB. PubMed, Embase, and Cochrane Library were systematically searched for publications reporting clinical outcomes of BLs+VAN or BLs+DAP for adult patients with MRSAB through 5 April 2020. Meta-analysis techniques were applied using random effects modeling. Three randomized controlled trials and 12 retrospective cohort studies were identified, totaling 2,594 patients. Combination treatment significantly reduced the risk of clinical failure (risk ratio [RR] = 0.80; 95% confidence interval [CI], 0.66 to 0.96; P = 0.02; I² = 39%), bacteremia recurrence (RR = 0.66; 95% CI, 0.50 to 0.86; P = 0.002; I² = 0%), and persistent bacteremia (RR = 0.65; 95% CI, 0.55 to 0.76; P < 0.00001; I² = 0%) and shortened the duration of bacteremia (standardized mean difference [SMD] = -0.37; 95% CI, -0.48 to -0.25; P < 0.00001; I² = 0%). There was no significant difference in the risk of crude mortality, nephrotoxicity, or thrombocytopenia between groups. Notably, combination treatment might nonsignificantly increase the risk of Clostridium difficile infection (CDI) (RR = 2.13; 95% CI, 0.98 to 4.63; P = 0.06; I² = 0%). Subgroup analysis suggested that DAP+BLs could reduce crude mortality (RR = 0.53; 95% CI, 0.28 to 0.98; P = 0.04; I² = 0%). The meta-analysis suggested that although combination therapy with BLs could improve some microbial outcomes, it could not reduce crude mortality but might increase the risk of CDI and should be applied very cautiously. Regarding mortality reduction, the combination of DAP+cephalosporins appears more promising.

Trends in Bacteremia Over 2 Decades in the Top End of the Northern Territory of Australia

Background

Information on the local distribution of bloodstream pathogens helps to guide empiric antibiotic selection and can generate hypotheses regarding the effectiveness of infection prevention practices. We assessed trends in bacterial blood culture isolates at Royal Darwin Hospital (RDH) in the Northern Territory of Australia between 1999 and 2019.

Methods

 Species identification was extracted for all blood cultures first registered at RDH. Thirteen organisms were selected for focused analysis. Trends were examined graphically and using univariable linear regression.

Results

 Between 1999 and 2019, 189 577 blood cultures from 65 276 patients were processed at RDH. Overall, 6.72% (12 747/189 577) of blood cultures contained a bacterial pathogen. Staphylococcus aureus was the most common cause of bacteremia during the first decade, with an estimated incidence of 96.6 episodes per 100 000 person-years (py; 95% CI, 72.2-121/100 000 py) in 1999. Since 2009, S. aureus bacteremia has declined markedly, whereas there has been an inexorable rise in Escherichia coli bacteremia (30.1 to 74.7/100 000 py between 1999 and 2019; P < .001), particularly in older adults. Since 2017, E. coli has been more common than S. aureus. Rates of Streptococcus pneumoniae bacteremia have reduced dramatically in children, while Burkholderia pseudomallei remained the fourth most common bloodstream isolate overall.

Conclusions

 The incidence of S. aureus bacteremia, though high by international standards, is declining at RDH, possibly in part due to a sustained focus on both community and hospital infection prevention practices. Gram-negative bacteremia, particularly due to E. coli, is becoming more common, and the trend will likely continue given our aging population.

Structural Basis for the Inhibitor and Substrate Specificity of the Unique Fph Serine Hydrolases of Staphylococcus aureus

Staphylococcus aureus is a prevalent bacterial pathogen in both community and hospital settings, and its treatment is made particularly difficult by resilience within biofilms. Within this niche, serine hydrolase enzymes play a key role in generating and maintaining the biofilm matrix. Activity-based profiling has previously identified a family of serine hydrolases, designated fluorophosphonate-binding hydrolases (Fph's), some of which contribute to the virulence of S. aureus in vivo. These 10 Fph proteins have limited annotation and have few, if any, characterized bacterial or mammalian homologues. This suggests unique hydrolase functions even within bacterial species. Here we report structures of one of the most abundant Fph family members, FphF. Our structures capture FphF alone, covalently bound to a substrate analogue and bound to small molecule inhibitors that occupy the hydrophobic substrate-binding pocket. In line with these findings, we show that FphF has promiscuous esterase activity toward hydrophobic lipid substrates. We present docking studies that characterize interactions of inhibitors and substrates within the active site environment, which can be extended to other Fph family members. Comparison of FphF to other esterases and the wider Fph protein family suggest that FphF forms a new esterase subfamily. Our data suggest that other Fph enzymes, including the virulence factor FphB, are likely to have more restricted substrate profiles than FphF. This work demonstrates a clear molecular rationale for the specificity of fluorophosphonate probes that target FphF and provides a structural template for the design of enhanced probes and inhibitors of the Fph family of serine hydrolases.

Community-acquired Invasive Bacterial Disease in Urban Gambia, 2005-2015: A Hospital-based Surveillance

Background. Invasive bacterial diseases cause significant disease and death in sub-Saharan Africa. Several are vaccine preventable, although the impact of new vaccines and vaccine policies on disease patterns in these communities is poorly understood owing to limited surveillance data.

Methods. We conducted a hospital-based surveillance of invasive bacterial diseases in The Gambia where blood and cerebrospinal fluid (CSF) samples of hospitalized participants were processed. Three surveillance periods were defined in relation to the introduction of pneumococcal conjugate vaccines (PCVs), before (2005- 2009), during (2010–2011) and after (2012–2015) PCV introduction. We determined the prevalences of commonly isolated bacteria and compared them between the different surveillance periods.

Results. A total of 14 715 blood and 1103 CSF samples were collected over 11 years; overall, 1045 clinically significant organisms were isolated from 957 patients (972 organisms [6.6%] from blood and 73 [6.6%] from CSF). The most common blood culture isolates were Streptococcus pneumoniae (24.9%), Staphylococcus aureus (22.0%), Escherichia coli (10.9%), and nontyphoidal Salmonella (10.0%). Between the pre-PCV and post-PCV eras, the prevalence of S. pneumoniae bacteremia dropped across all age groups (from 32.4% to 16.5%; odds ratio, 0.41; 95% confidence interval, .29–.58) while S. aureus increased in prevalence, becoming the most prevalent bacteria (from 16.9% to 27.2%; 1.75; 1.26–2.44). Overall, S. pneumoniae (53.4%), Neisseria meningitidis (13.7%), and Haemophilus influenzae (12.3%) were the predominant isolates from CSF. Antimicrobial resistance to common antibiotics was low.

Conclusions. Our findings demonstrate that surveillance data on the predominant pathogens associated with invasive disease is necessary to inform vaccine priorities and appropriate management of patients.

Development of quality indicators for the management of Staphylococcus aureus bacteraemia

Background

Staphylococcus aureus bacteraemia (SAB) is a serious and often fatal infectious disease. The quality of management of SAB is modifiable and can thus affect the outcome. Quality indicators (QIs) can be used to measure the quality of care of the various aspects of SAB management in hospitals, enabling professionals to identify targets for improvement and stimulating them to take action.

Objectives

To develop QIs for the management of hospitalized patients with SAB.

Methods

A RAND-modified Delphi procedure was used to develop a set of QIs for the management of SAB in hospitalized patients. First, available QIs for the management of SAB were extracted from the literature published since 1 January 2000 (MEDLINE and Embase databases). Thereafter, an international multidisciplinary expert panel appraised these QIs during two questionnaire rounds with an intervening face-to-face meeting.

Results

The literature search resulted in a list of 39 potential QIs. After appraisal by 30 medical specialists, 25 QIs describing recommended care at patient level were selected. These QIs defined appropriate follow-up blood cultures (n=2), echocardiography (n=6), source control (n=4), antibiotic therapy (n=7), antibiotic dose adjustment (n=2), intravenous-to-oral switch (n=2), infectious disease consultation (n=1) and medical discharge report (n=1).

Conclusions

A set of 25 QIs for the management of SAB for hospitalized patients was developed by using a RAND-modified Delphi procedure among international experts. These QIs can measure the quality of various aspects of SAB management. This information can be fed back to the relevant stakeholders in order to identify improvement targets and optimize care.

Impact of β-Lactam and Daptomycin Combination Therapy on Clinical Outcomes in Methicillin-susceptible Staphylococcus aureus Bacteremia: A Propensity Score-matched Analysis

BACKGROUND

Mortality rates from Staphylococcus aureus bacteremia are high and have only modestly improved in recent decades. We compared the efficacies of a β-lactam in combination with daptomycin (BL/D-C) and β-lactam monotherapy (BL-M) in improving clinical outcomes in methicillin-susceptible S. aureus (MSSA) bacteremia.

METHODS

A retrospective cohort study of MSSA bacteremia was performed in a tertiary hospital from January 2011 to December 2017. Patients receiving BL/D-C and BL-M were compared to assess 7-, 30-, and 90-day mortality rates. A 1:2 propensity score matching analysis was performed. Differences were assessed using Cox regression models.

RESULTS

Of the 514 patients with MSSA bacteremia, 164 were excluded as they had received combination therapies other than BL/D-C, had pneumonia, or died within 48 hours of admission. Of the remaining 350 patients, 136 and 214 received BL/D-C and BL-M, respectively. BL/D-C patients had higher Pitt scores and persistent bacteremia more often than BL-M patients. In the raw analysis, there were no differences in mortality rates between groups. After propensity score matching, there were no significant differences between the BL/D-C (110 patients) and BL-M (168 patients) groups for all-cause mortality rates at 7 days (8.18% vs 7.74%; P = 1.000), 30 days (17.3% vs 16.1%; P = .922), and 90 days (22.7% vs 23.2%; P = 1.000), even in a subanalysis of patients with high-risk source of infection and in a subgroup excluding catheter-related bacteremia.

CONCLUSIONS

BL/D-C failed to reduce mortality rates in patients with MSSA bacteremia. Treatment strategies to improve survival in MSSA bacteremia are urgently needed.

Impact of Location of Acquisition of Gram-Positive Bloodstream Infections on Clinical Outcomes Among Patients Admitted to Community Hospitals

Purpose

We investigated the association between location of acquisition (LOA) of gram-positive (GP) bloodstream infections (BSI) in community hospitals and clinical outcomes.

Methods

We performed a multicenter cohort study of adult inpatients with GP BSI in nine community hospitals from 2003 to 2006. LOA was defined by CDC criteria: 1) community-acquired (CA), 2) healthcare-associated (HCA) such as BSI <48 hours after admission plus hospitalization, surgery, dialysis, invasive device, or residence in a long-term care facility in the prior 12 months, and 3) hospital-acquired (HA) as BSI ≥48 hours after hospital admission.

Results

A total of 750 patients were included. Patients with HCA or HA GP BSI were significantly more likely to require assistance with ≥1 activity of daily living, have higher Charlson scores, and die during the hospitalization. Patients with HCA or HA GP BSI were more likely to have BSI due to a multidrug-resistant GP organism, but less likely to receive appropriate antibiotics within 24 hours of BSI presentation. Those with CA BSI were more likely to have a streptococcal BSI and to be discharged home following hospitalization. HA BSI was a risk factor for requiring a procedure for BSI and receiving inappropriate antibiotics within 24 hours of BSI. Both HA and HCA GP BSI were risk factors for in-hospital mortality.

Conclusion

LOA for patients with GP BSI in community hospitals was significantly associated with differences in clinical outcomes including receiving inappropriate antibiotics and in-hospital mortality. Distinguishing LOA in a patient presenting with suspected GP BSI is a critical assessment that should influence empiric treatment patterns.

Early Oral Switch to Linezolid for Low-risk Patients With Staphylococcus aureus Bloodstream Infections: A Propensity-matched Cohort Study

BACKGROUND

Oral switch to linezolid is a promising alternative to standard parenteral therapy (SPT) in Staphylococcus aureus bacteremia (SAB).

METHODS

We conducted a prospective cohort study of all adult cases of SAB between 2013 and 2017 in a Spanish university hospital. We compared the efficacy, safety, and length of hospital stay of patients receiving SPT and those where SPT was switched to oral linezolid between days 3 and 9 of treatment until completion. We excluded complicated SAB and osteoarticular infections. A k-nearest neighbor algorithm was used for propensity score matching with a 2:1 ratio.

RESULTS

After propensity score matching, we included 45 patients from the linezolid group and 90 patients from the SPT group. Leading SAB sources were catheter related (49.6%), unknown origin (20.0%), and skin and soft tissue (17.0%). We observed no difference in 90-day relapse between the linezolid group and the SPT group (2.2% vs 4.4% respectively; P = .87). No statistically significant difference was observed in 30-day all-cause mortality between the linezolid group and the SPT group (2.2% vs 13.3%; P = .08). The median length of hospital stay after onset was 8 days in the linezolid group and 19 days in the SPT group (P < .01). No drug-related events leading to discontinuation were noted in the linezolid group.

CONCLUSIONS

Treatment of SAB in selected low-risk patients with an oral switch to linezolid between days 3 and 9 of treatment until completion yielded similar clinical outcomes as SPT, allowing earlier discharge from the hospital.

Moving beyond unsolicited consultation: additional impact of a structured intervention on mortality in Staphylococcus aureus bacteraemia

BACKGROUND

Some evidence-based bundles have tried to standardize the management of Staphylococcus aureus bacteraemia (SAB) to improve the outcome. The aim of our study was to analyse the additional impact on mortality of a structured intervention in patients with SAB.

METHODS

Compliance with the bundle was evaluated in an ambispective cohort of patients with SAB, which included a retrospective cohort [including patients treated before and after the implementation of a bacteraemia programme (no-BP and BP, respectively)] and a prospective cohort (i-BP), in which an additional specific intervention for bundle application was implemented. Multivariate logistic regression was used to measure the influence of the independent variables including compliance with the bundle on 14 and 30 day crude mortality.

RESULTS

A total of 271 adult patients with SAB were included. Mortality was significantly different among the three groups (no-BP, BP and i-BP): mortality at 14 days was 18% versus 7% versus 2%, respectively, P = 0.002; and mortality at 30 days was 20% versus 12% versus 5%, respectively, P = 0.011. The factors associated with 14 and 30 day mortality in multivariable analysis were heart failure (OR = 7.63 and OR = 2.27, respectively), MRSA infection (OR = 4.02 and OR = 4.37, respectively) and persistent bacteraemia (OR = 11.01 and OR = 7.83, respectively); protective factors were catheter-related bacteraemia (OR = 0.16 and OR = 0.19, respectively) and >75% bundle compliance (OR = 0.15 and OR = 0.199, respectively). Time required to perform the intervention and the follow-up was 50 min (IQR 40-55 min) per patient.

CONCLUSIONS

High-level compliance with a standardized bundle of intervention for management of SAB that requires little time was associated with lower mortality at 14 and 30 days.

Prospective Validation of PREDICT and its Impact on the Transesophageal Echocardiography Use in Management of Staphylococcus aureus Bacteremia

BACKGROUND

Infective endocarditis (IE) is the most feared complication of Staphylococcus aureus bacteremia (SAB). Transesophageal echocardiogram (TEE) is generally recommended for all patients with SAB, however, supporting data for this are limited. We previously developed a scoring system, "PREDICT", that quantifies the risk of IE and identifies patients who would benefit the most from undergoing TEE. The current prospective investigation aims to validate this score.

METHODS

We prospectively screened all consecutive adults (≥18 years) hospitalized with SAB at three Mayo Clinic sites between January 2015 and March 2017.

RESULTS

Of 220 patients screened, 199 with SAB met study criteria and were included in the investigation. Of them, 23 (11.6%) patients were diagnosed with definite IE within 12 weeks of initial presentation based on modified Duke's criteria. Using the previously derived PREDICT model, the day 1 score of ≥4 had a sensitivity of 30.4% and a specificity of 93.8%, whereas day 5 score of ≤2 had a sensitivity and negative predictive value of 100%. Additional factors including surgery or invasive procedure in the past 30 days, prosthetic heart valve, and higher number of positive blood culture bottles in the first set of cultures were associated with increased risk of IE independent of the day 5 risk score.

CONCLUSION

We validated the previously developed PREDICT scoring tools for stratifying risk of IE, and the need for undergoing a TEE, among cases of SAB. We also identified other factors with predictive potential, although larger prospective studies are needed to further evaluate possible enhancements to the current scoring system.

A case study on Staphylococcus aureus bacteraemia: available treatment options, antibiotic R&D and responsible antibiotic-use strategies

Objectives

This case study addresses: (i) antibiotic treatment options for Staphylococcus aureus bacteraemia (SAB), for both empirical and targeted therapy; (ii) the current status of and priorities for the antibiotic pipeline to ensure access of effective antibiotics for SAB; and (iii) strategies for responsible antibiotic use relevant to the clinical management of SAB.

Methods

Evidence to address the aims was extracted from the following information sources: (i) EUCAST and CLSI recommendations, summaries of product characteristics (SPCs), antibiotic treatment guidelines and the textbook Kucers’ The Use of Antibiotics; (ii) the www.clinicaltrial.gov database; and (iii) quality indicators for responsible antibiotic use.

Results

Current monotherapy treatment options for SAB include only three drug classes (β-lactams, glycopeptides and lipopeptides), of which two also cover MRSA bacteraemia (glycopeptides and lipopeptides). The analysis of the antibiotic pipeline and ongoing clinical trials revealed that several new antibiotics with S. aureus (including MRSA) coverage were developed in the past decade (2009–19). However, none belonged to a new antibiotic class or had superior effectiveness and their added clinical value for SAB remains to be proven. Responsible antibiotic use for the treatment of SAB was illustrated using 11 quality indicators.

Conclusions

Awareness of the problem of a limited antibiotic arsenal, together with incentives (e.g. push incentives), is needed to steer the R&D landscape towards the development of novel and effective antibiotics for treating SAB. In the meantime, responsible antibiotic use guided by quality indicators should preserve the effectiveness of currently available antibiotics for treating SAB.

Adherence to standards of care and mortality in the management of Staphylococcus aureus bacteraemia in Peru: A prospective cohort study

BACKGROUND

Despite high mortality rates, physicians can alter the course of the Staphylococcus aureus bacteraemia (SAB) by following recommended standards of care. We aim to assess the adherence of these guidelines and their impact on mortality.

METHODS

Substudy from a prospective cohort of hospitalized patients with SAB from three hospitals from Peru. Hazard ratios were calculated using Cox proportional regression to evaluate the association between 30-day mortality and the performance of standards of care: removal of central venous catheters (CVC), follow-up blood cultures, echocardiography, correct duration, and appropriate definitive antibiotic therapy.

RESULTS

150 cases of SAB were evaluated; 61.33% were MRSA. 30-day attributable mortality was 22.39%. CVC removal was done in 42.86% of patients. Follow-up blood cultures and echocardiograms were performed in 8% and 29.33% of cases, respectively. 81.33% of cases had appropriate empirical treatment, however, only 22.41% of MSSA cases were given appropriate definitive treatment, compared to 93.47% of MRSA. The adjusted regression for all-cause mortality found a substantial decrease in hazards when removing CVC (aHR 0.28, 95% CI: 0.10 - 0.74) and instituting appropriate definitive treatment (aHR 0.27, 95% CI: 0.08 - 0.86), while adjusting for standards of care, qPitt bacteraemia score, comorbidities, and methicillin susceptibility; similar results were found in the attributable mortality model (aHR 0.24, 95% CI: 0.08 - 0.70 and aHR 0.21, 95% CI: 0.06 - 0.71, respectively).

CONCLUSIONS

Deficient adherence to standards of care was observed, especially definitive treatment for MSSA. CVC removal and the use of appropriate definitive antibiotic therapy reduced the hazard mortality of SAB.

Characteristics and Outcomes of Staphylococcus aureus Bloodstream Infection Originating From the Urinary Tract: A Multicenter Cohort Study

Background

Staphylococcus aureus bloodstream infection (SABSI) arising from a urinary tract source (UTS) is poorly understood.

Methods

We conducted a retrospective analysis in 3 major teaching hospitals in Spain of prospectively collected data of hospitalized patients with SABSI. SABSI-UTS was diagnosed in patients with urinary tract symptoms and/or signs, no evidence of an extra-urinary source of infection, and a urinary S. aureus count of ≥10⁵ cfu/mL. Susceptibility of S. aureus strains and patient mortality were compared between SABSI from UTS (SABSI-UTS) and other sources (SABSI-other).

Results

Of 4181 episodes of SABSI, we identified 132 (3.16%) cases of SABSI-UTS that occurred predominantly in patients who were male, had high Charlson comorbidity scores, were dependent for daily life activities, and who had undergone urinary catheterization and/or urinary manipulation before the infection. SABSI-UTS was more often caused by MRSA strains compared with SABSI-other (40.9% vs 17.5%; P < .001). Patients with SABSI-UTS caused by MRSA more often received inadequate empirical treatment compared with those caused by susceptible strains (59.7% vs 23.1%; P < .001). The 30-day case fatality rate was lower in patients with SABSI-UTS than in those with SABSI-other (14.4% vs 23.8%; P = .02). Factors independently associated with mortality were dependence for daily activities (aOR, 3.877; 95% CI, 1.08–13.8; P = .037) and persistent bacteremia (aOR, 7.88; 95% CI, 1.57–39.46; P = .012).

Conclusions

SABSI-UTS occurs predominantly in patients with severe underlying conditions and in those who have undergone urinary tract manipulation. Moreover, it is frequently due to MRSA strains and causes significant mortality.

Therapy of Staphylococcus aureus bacteremia: Evidences and challenges

Staphylococcus aureus bacteremia (SAB) is still a daily challenge for clinicians. Despite all efforts, the associated mortality and morbidity has not significantly improved in the last 20 years. The available evidence suggests that adherence to some quality-of-care indicators with regard to clinical management is important in improving the outcome of patients, but it is lower than desired in many hospitals; as such, management of patients with SAB by infectious diseases specialists has been demonstrated to contribute in the reduction of the mortality rate of these patients. In this article, the most relevant clinical studies published over the last few years evaluating the efficacy and safety of alternative drugs for the treatment of SAB are reviewed. However, classic drugs are still used in a high proportion of patients because the promising results obtained from in vivo and in vivo studies with these alternative drugs have not translated as frequently as expected into evident superiority in clinical studies. Nevertheless, some data suggest that certain alternatives may offer advantages in specific situations. Overall, an individualised and expert approach is needed in order to decide the best treatment according to the source, severity, complications, patients' features and microbiological data.

Graphene Oxide-Silver Nanoparticle Nanohybrids: Synthesis, Characterization, and Antimicrobial Properties

Drug resistance of pathogenic microorganisms has become a global public health problem, which has prompted the development of new materials with antimicrobial properties. In this context, antimicrobial nanohybrids are an alternative due to their synergistic properties. In this study, we used an environmentally friendly one-step approach to synthesize graphene oxide (GO) decorated with silver nanoparticles (GO-AgNPs). By this process, spherical AgNPs of average size less than 4 nm homogeneously distributed on the surface of the partially reduced GO can be generated in the absence of any stabilizing agent, only with ascorbic acid (L-AA) as a reducing agent and AgNO3 as a metal precursor. The size of the AgNPs can be controlled by the AgNO3 concentration and temperature. Smaller AgNPs are obtained at lower concentrations of the silver precursor and lower temperatures. The antimicrobial properties of nanohybrids against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, Gram-positive Staphylococcus aureus, and the yeast Candida albicans were found to be concentration- and time-dependent. C. albicans and S. aureus showed the highest susceptibility to GO-AgNPs. These nanohybrids can be used as nanofillers in polymer nanocomposites to develop materials with antimicrobial activity for applications in different areas, and another potential application could be cancer therapeutic agents.

Staphylococcus Aureus Bacteriuria as a Predictor of In-Hospital Mortality in Patients with Staphylococcus Aureus Bacteremia. Results of a Retrospective Cohort Study

Staphylococcus aureus bloodstream infection (SA-BSI) is an infection with increasing morbidity and mortality. Concomitant Staphylococcus aureus bacteriuria (SABU) frequently occurs in patients with SA-BSI. It is considered as either a sign of exacerbation of SA-BSI or a primary source in terms of urosepsis. The clinical implications are still under investigation. In this study, we investigated the role of SABU in patients with SA-BSI and its effect on the patients' mortality. We performed a retrospective cohort study that included all patients in our university hospital (Charité Universitätsmedizin Berlin) between 1 January 2014 and 31 March 2017. We included all patients with positive blood cultures for Staphylococcus aureus who had a urine culture 48 h before or after the first positive blood culture. We identified cases while using the microbiology database and collected additional demographic and clinical parameters, retrospectively, from patient files and charts. We conducted univariate analyses and multivariable Cox regression analysis to evaluate the risk factors for in-hospital mortality. 202 patients met the eligibility criteria. Overall, 55 patients (27.5%) died during their hospital stay. Cox regression showed SABU (OR 2.3), Pitt Bacteremia Score (OR 1.2), as well as moderate to severe liver disease (OR 2.1) to be independent risk factors for in-hospital mortality. Our data indicates that SABU in patients with concurrent SA-BSI is a prognostic marker for in-hospital death. Further studies are needed for evaluating implications for therapeutic optimization.

Early-Stage Staphylococcus aureus Bloodstream Infection Causes Changes in the Concentrations of Lipoproteins and Acute-Phase Proteins and Is Associated with Low Antibody Titers against Bacterial Virulence Factors

S. aureus sepsis has a high complication and mortality rate. Given the limited therapeutic possibilities, effective prevention strategies, e.g., a vaccine, or the early identification of high-risk patients would be important but are not available. Our study showed an acute-phase response in patients with S. aureus bloodstream infection and evidence that lipoproteins are downregulated in plasma. Using immunoproteomics, stratification of patients appears to be achievable, since at the early stages of systemic S. aureus infection patients had low preexisting anti-S. aureus antibody levels. This strengthens the notion that a robust immune memory for S. aureus protects against infections with the pathogen.

Systemic and quantitative investigations of human plasma proteins (proteomics) and Staphylococcus aureus-specific antibodies (immunoproteomics) provide complementary information and hold promise for the discovery of biomarkers in Staphylococcus aureus bloodstream infection (SABSI). Usually, data-dependent acquisition (DDA) is used for proteome analysis of serum or plasma, but data-independent acquisition (DIA) is more comprehensive and reproducible. In this prospective cohort study, we aimed to identify biomarkers associated with the early stages of SABSI using a serum DIA proteomic and immunoproteomic approach. Sera from 49 SABSI patients and 43 noninfected controls were analyzed. In total, 608 human serum proteins were identified with DIA. A total of 386 proteins could be quantified, of which 9 proteins, mainly belonging to acute-phase proteins, were significantly increased, while 7 high-density lipoproteins were lower in SABSI. In SABSI, total anti-S. aureus serum IgG was reduced compared with controls as shown by immunoproteomic quantification of IgG binding to 143 S. aureus antigens. IgG binding to 48 of these anti-S. aureus proteins was significantly lower in SABSI, while anti-Ecb IgG was the only one increased in SABSI. Serum IgG binding to autoinducing peptide MsrB, FadB, EsxA, Pbp2, FadB, SspB, or SodA was very low in SABSI. This marker panel discriminated early SABSI from controls with 95% sensitivity and 100% specificity according to random forest prediction. This holds promise for patient stratification according to their risk of S. aureus infection, underlines the protective function of the adaptive immune system, and encourages further efforts in the development of a vaccine against S. aureus.

IMPORTANCES. aureus sepsis has a high complication and mortality rate. Given the limited therapeutic possibilities, effective prevention strategies, e.g., a vaccine, or the early identification of high-risk patients would be important but are not available. Our study showed an acute-phase response in patients with S. aureus bloodstream infection and evidence that lipoproteins are downregulated in plasma. Using immunoproteomics, stratification of patients appears to be achievable, since at the early stages of systemic S. aureus infection patients had low preexisting anti-S. aureus antibody levels. This strengthens the notion that a robust immune memory for S. aureus protects against infections with the pathogen.

Age-Dependent Increase in Incidence of Staphylococcus aureus Bacteremia, Denmark, 2008-2015

During 2008–2015, overall incidence increased by 50%, with a dramatic increase in persons >80 years of age.

Staphylococcus aureus bacteremia (SAB) is a major cause of illness and death worldwide. We analyzed temporal trends of SAB incidence and death in Denmark during 2008–2015. SAB incidence increased 48%, from 20.76 to 30.37 per 100,000 person-years, during this period (p<0.001). The largest change in incidence was observed for persons >80 years of age: a 90% increase in the SAB rate (p<0.001). After adjusting for demographic changes, annual rates increased 4.0% (95% CI 3.0–5.0) for persons <80 years of age, 8.4% (95% CI 7.0–11.0) for persons 80–89 years of age, and 13.0% (95% CI 9.0–17.5) for persons >90 years of age. The 30-day case-fatality rate remained stable at 24%; crude population death rates increased by 53% during 2008–2015 (p<0.001). Specific causes and mechanisms for this rapid increase in SAB incidence among the elderly population remain to be clarified.