Gender differences in the outcome of community-acquired Staphylococcus aureus bacteraemia: a historical population-based cohort study

Collaborative Cross mice have diverse phenotypic responses to infection with Methicillin-resistant Staphylococcus aureus USA300

Staphylococcus aureus (S. aureus) is an opportunistic pathogen causing diseases ranging from mild skin infections to life threatening conditions, including endocarditis, pneumonia, and sepsis. To identify host genes modulating this host-pathogen interaction, we infected 25 Collaborative Cross (CC) mouse strains with methicillin-resistant S. aureus (MRSA) and monitored disease progression for seven days using a surgically implanted telemetry system. CC strains varied widely in their response to intravenous MRSA infection. We identified eight 'susceptible' CC strains with high bacterial load, tissue damage, and reduced survival. Among the surviving strains, six with minimal colonization were classified as 'resistant', while the remaining six tolerated higher organ colonization ('tolerant'). The kidney was the most heavily colonized organ, but liver, spleen and lung colonization were better correlated with reduced survival. Resistant strains had higher pre-infection circulating neutrophils and lower post-infection tissue damage compared to susceptible and tolerant strains. We identified four CC strains with sexual dimorphism: all females survived the study period while all males met our euthanasia criteria earlier. In these CC strains, males had more baseline circulating monocytes and red blood cells. We identified several CC strains that may be useful as new models for endocarditis, myocarditis, pneumonia, and resistance to MRSA infection. Quantitative Trait Locus (QTL) analysis identified two significant loci, on Chromosomes 18 and 3, involved in early susceptibility and late survival after infection. We prioritized Npc1 and Ifi44l genes as the strongest candidates influencing survival using variant analysis and mRNA expression data from kidneys within these intervals.

Sex differences in infective endocarditis: a Danish nationwide study

PURPOSE

Sex differences in infective endocarditis (IE) are reported, but patient characteristics are sparse and conflicting findings on the association between sex and short-term outcomes demand further research. We aimed to characterize sex differences in IE in terms of patient characteristics, frailty, microbiology, socioeconomic status, management and outcome on a nationwide scale.

METHODS

Between 2010 and 2020, we used Danish national registries to characterize patients with IE according to sex using ICD codes and microbiological lab reports. Frailty was assessed with the Hospital Frailty Risk Score. Mortality was reported with Kaplan-Meier estimates. Logistic regression and Cox regression were used for adjusted analyses.

RESULTS

We included 6259 patients with IE with 2047 (32.7%) female patients and 4212 (67.3%) male patients. Female patients were older (median age 75.0 years (64.3-82.2) vs. 71.7 (61.7-78.9)) and more frail (Intermediate frailty: 36.5% vs. 33.1%, High frailty: 11.4% vs. 9.2%). Staphylococcus aureus-IE were most common in both sexes (34.6% vs. 28.8%), but fewer female patients had Enterococcus-IE (10.5% vs. 18.1%). Female patients were less surgically treated (14.0% vs. 21.2%). Female sex was associated with increased in-hospital mortality (adj. OR 1.33, 95% CI 1.16-1.52), but no statistically significant difference in associated 1- and 5-year mortality from hospital discharge were identified (adj. HR 1.09, 95% CI 0.95-1.24 and 1.02, 95% CI 0.92-1.12, respectively).

CONCLUSION

Female sex is associated with increased in-hospital mortality, but not in long-term mortality as compared with male patients. Female patients have a lower prevalence of Enterococcus-IE and rates of surgery. Further research is needed to understand these differences.

Androgens at the skin surface regulate S. aureus pathogenesis through the activation of agr quorum sensing

Staphylococcus aureus, the most frequent cause of skin infections, is more common in men than women and selectively colonizes the skin during inflammation. Yet, the specific cues that drive infection in these settings remain unclear. Here we show that the host androgens testosterone and dihydrotestosterone promote S. aureus pathogenesis and skin infection. Without the secretion of these hormones, skin infection in vivo is limited. Testosterone activates S. aureus virulence in a concentration dependent manner through stimulation of the agr quorum sensing system, with the capacity to circumvent other inhibitory signals in the environment. Taken together, our work defines a previously uncharacterized inter-kingdom signal between the skin and the opportunistic pathogen S. aureus and identifies the mechanism of sex-dependent differences in S. aureus skin infection.

One-Sentence Summary

Testosterone promotes S. aureus pathogenesis through activation of the agr quorum sensing system.

Female Sex and Mortality in Patients with Staphylococcus aureus Bacteremia: A Systematic Review and Meta-analysis

Importance

Staphylococcus aureus is the leading cause of death due to bacterial bloodstream infection. Female sex has been identified as a risk factor for mortality in S aureus bacteremia (SAB) in some studies, but not in others.

Objective

To determine whether female sex is associated with increased mortality risk in SAB.

Data Sources

MEDLINE, Embase, and Web of Science were searched from inception to April 26, 2023.

Study Selection

Included studies met the following criteria: (1) randomized or observational studies evaluating adults with SAB, (2) included 200 or more patients, (3) reported mortality at or before 90 days following SAB, and (4) reported mortality stratified by sex. Studies on specific subpopulations (eg, dialysis, intensive care units, cancer patients) and studies that included patients with bacteremia by various microorganisms that did not report SAB-specific data were excluded.

Data Extraction and Synthesis

Data extraction and quality assessment were performed by 1 reviewer and verified by a second reviewer. Risk of bias and quality were assessed with the Newcastle-Ottawa Quality Assessment Scale. Mortality data were combined as odds ratios (ORs).

Main Outcome and Measures

Mortality at or before 90-day following SAB, stratified by sex.

Results

From 5339 studies retrieved, 89 were included (132 582 patients; 50 258 female [37.9%], 82 324 male [62.1%]). Unadjusted mortality data were available from 81 studies (109 828 patients) and showed increased mortality in female patients compared with male patients (pooled OR, 1.12; 95% CI, 1.06-1.18). Adjusted mortality data accounting for additional patient characteristics and treatment variables were available from 32 studies (95 469 patients) and revealed a similarly increased mortality risk in female relative to male patients (pooled adjusted OR, 1.18; 95% CI, 1.11-1.27). No evidence of publication bias was encountered.

Conclusions and Relevance

In this systematic review and meta-analysis, female patients with SAB had higher mortality risk than males in both unadjusted and adjusted analyses. Further research is needed to study the potential underlying mechanisms.

Mortality patterns in patients with Staphylococcus aureus bacteremia during the COVID-19 pandemic: Predictors and insights

Objectives

This paper aims to determine the Staphylococcus aureus bacteremia (SAB) in-hospital mortality rate and its associated risk factors during the COVID-19 pandemic.

Methods

A total of 167 SAB samples were collected between March 2020 and March 2022 at a teaching hospital in Tehran, Iran. The patient's baseline data and antibiograms were collected. The outcome of the study was in-hospital mortality.

Results

The overall in-hospital mortality rate was 41.9 %, with higher mortality observed in patients over 60 years old (P = 0.032), those with community-acquired Staphylococcus aureus bacteremia (P = 0.010), and those admitted to the ICU (P = 0.016). Antibiotic resistance profiles indicated a higher mortality in resistant S.aureus strains but only significant for ciprofloxacin (P = 0.001), methicillin (P = 0.047), and sulfamethoxazole (P = 0.023). Multivariate analysis identified age, sex, ICU admission, and the source of bacteremia as independent predictors of mortality, while COVID-19 coinfection and resistance to antibiotics were not found to be significant predictors.

Conclusion

SAB remains a challenging infection that is amplified by the pandemic. Older age and ICU admission are significant mortality predictors. In settings with a high prevalence of MRSA, factors like age, sex, and quality of care outweigh pathogen-related factors such as antibiotic resistance.

The association of female sex with management and mortality in patients with Staphylococcus aureus bacteraemia

OBJECTIVES

The association of biological female sex with outcome in patients with Staphylococcus aureus bacteraemia remains unresolved. The aim of this study was to determine the independent association of female sex with management and mortality in patients with S. aureus bacteraemia.

METHODS

This is a post hoc analysis of prospectively collected data from the S. aureus Bacteraemia Group Prospective Cohort Study. Adult patients with monomicrobial S. aureus bacteraemia at Duke University Medical Center were enrolled from 1994 to 2020. Univariable and multivariable Cox regression analyses were performed to assess differences in management and mortality between females and males.

RESULTS

Among 3384 patients with S. aureus bacteraemia, 1431 (42%) were women. Women were, as compared with men, more often Black (581/1431 [41%] vs. 620/1953 [32%], p < 0.001), haemodialysis dependent (309/1424 [22%] vs. 334/1940 [17%], p 0.001) and more likely to be infected with methicillin-resistant S. aureus (MRSA) (697/1410 [49%] MRSA in women vs. 840/1925 [44%] MRSA in men, p 0.001). Women received shorter durations of antimicrobial treatment (median 24 [interquartile range 14-42] vs. 28 [interquartile range 14-45] days, p 0.005), and were less likely to undergo transesophageal echocardiography as compared with men (495/1430 [35%] vs. 802/1952 [41%], p < 0.001). Despite these differences, female sex was not associated with 90-day mortality in either univariable (388/1431 [27%] in women vs. 491/1953 [25%] in men, p 0.204) or multivariable analysis (adjusted hazard ratio for women 0.98 [95% CI, 0.85-1.13]).

DISCUSSION

Despite significant differences in patient characteristics, disease characteristics, and management, women and men with S. aureus bacteraemia have a similar mortality risk.

[Sex in infectious diseases-How sex differences influence the immune response to infections]

The humoral and cellular immune responses to antigen stimulation, vaccinations and infections differ between women and men. Genetic, epigenetic and hormonal factors contribute to the sex-specific immunity. The expression of genes on the X‑chromosome and the effect of sex hormones substantially influence the immune defence against infections. Females show stronger cellular and humoral immune responses to infections than males, but the enhanced immune response often leads to aberrant inflammatory reactions and autoimmune diseases. Men are principally more prone to bacterial, viral and fungal infections and more often show severe disease courses. In contrast, a more reactive female immune system results in significantly more adverse reactions to vaccinations. In order to be able to better identify the multiple sex-specific that have an influence on the immune system, sex-specific differences should be investigated in a differentiated way. The better understanding of the sex-specific differences in the immune response will have a long-term influence on the prevention, diagnostics and treatment of infectious diseases, and will ultimately contribute to improving healthcare of both women and men.

GENDER-RELATED VARIATIONS IN PATHOPHYSIOLOGICAL RESPONSES TO METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS PNEUMONIA AND SEPSIS

ABSTRACT

In preclinical studies, the protective effects of female sex hormones and the immunosuppressive effects of male sex hormones were demonstrated. However, gender-related differences in multiorgan failure and mortality in clinical trials have not been consistently explained. This study aims to investigate gender-related differences in the development and progression of sepsis using a clinically relevant ovine model of sepsis. Adult Merino male (n=7) and female (n=7) sheep were surgically prepared with multiple catheters before the study. To induce sepsis, bronchoscopy instilled methicillin-resistant Staphylococcus aureus into sheep's lungs. The time from the bacterial inoculation until the modified Quick Sequential Organ Failure Assessment (q-SOFA) score became positive was measured and analyzed primarily. We also compared the SOFA score between these male and female sheep over time. Survival, hemodynamic changes, the severity of pulmonary dysfunction, and microvascular hyperpermeability were also compared. The time from the onset of bacterial inoculation to the positive q-SOFA in male sheep was significantly shorter than in female sheep. Mortality was not different between these sheep (14% vs. 14%). There were no significant differences in hemodynamic changes and pulmonary function between the two groups at any time point. Similar changes in hematocrit, urine output, and fluid balance were observed between females and males. The present data indicate that the onset of multiple organ failure and progression of sepsis is faster in male sheep than in female sheep, even though the severity of cardiopulmonary function is comparable over time. Further studies are warranted to validate the above results.

Comparison of Length of Hospital Stay for Community-Acquired Infections Due to Enteric Pathogens, Influenza Viruses and Multidrug-Resistant Bacteria: A Cross-Sectional Study in Hungary

Community-acquired infections (CAI) can affect the duration of care and mortality of patients. Therefore, we aimed to investigate these as well as factors influencing the length of hospital stay in patients with CAI due to enteric pathogens, influenza viruses and multidrug-resistant (MDR) bacteria. We obtained data on 531 patients with CAI from the medical databases of a Hungarian university hospital and analyzed their characteristics using a regression model. Patients with MDR bacterial infection had the highest mortality (26.24%) and they stayed significantly longer in the hospital than cases with other CAIs. Our results showed that infection by Clostridioides difficile (odds ratio (OR): 6.98, 95% confidence interval (CI): 1.03-47.48; p = 0.047), MDR Escherichia coli (OR: 7.64, 95% CI: 1.24-47.17; p = 0.029), MDR Klebsiella spp. (OR: 7.35, 95% CI: 1.15-47.07; p = 0.035) and hospitalization in the department of pulmonology (OR: 5.48, 95% CI: 1.38-21.76; p = 0.016) and surgery (OR: 4.19, 95% CI: 1.18-14.81; p = 0.026) significantly increased, whereas female sex (OR: 0.62, 95% CI: 0.40-0.97; p = 0.037) and hospitalization in the department of pediatrics (OR: 0.17, 95% CI: 0.04-0.64; p = 0.009) decreased the odds of staying in the hospital for more than 6 days. Our findings provide new information on the epidemiology of CAI and can contribute to the development of public health programs that decrease the burden of infections acquired in the community.

Impact of neutropenia on clinical manifestations and outcome of Staphylococcus aureus bloodstream infection - A propensity score-based overlap weight analysis in two large, prospectively evaluated cohorts

OBJECTIVE

To investigate whether neutropenia influenced mortality and long-term outcome of Staphylococcus aureus bloodstream infection (SAB).

METHODS

Data from two prospective, multicentre cohort studies (INSTINCT and ISAC) conducted in 20 tertiary care hospitals in 6 countries between 2006 and 2015 were analysed. Neutropenic and severely neutropenic patients (defined by the proxy of total white blood cell count <1000/μl and <500/μl, respectively, at onset of SAB) were compared to a control group using a propensity score model and overlap weights to adjust for baseline characteristics. Overall survival and time to SAB-related late complications (SAB recurrence, infective endocarditis, osteomyelitis, or other deep-seated manifestations) were analysed by Cox regression and competing risk analyses, respectively.

RESULTS

Of 3,187 patients, 102 were neutropenic and 70 were severely neutropenic at onset of SAB. Applying overlap weights yielded two groups of 83 neutropenic and 220 non-neutropenic patients, respectively. Baseline characteristics of these groups were exactly balanced. In the Cox regression analysis, we observed no significant difference in survival between the two groups (death during follow-up: 36.1 % in neutropenic vs. 30.6 % in non-neutropenic patients, hazard ratio 1.21 (95 % CI 0.79-1.83)). This finding remained unchanged when we considered severely neutropenic patients (hazard ratio 1.08 [0.60; 1.94]). Competing risk analysis showed a cause-specific hazard ratio (CSHR) of 0.39 (95 % CI 0.11-1.39) for SAB-related late-complications in neutropenic patients.

CONCLUSIONS

Neutropenia was not associated with a higher survival during follow-up. The lower rate of SAB-related late complications in neutropenic patients should be validated in other cohorts.

A biological approach to adult sex differences in skeletal indicators of childhood stress

OBJECTIVES

In previous work examining the etiology of cribra orbitalia (CO) and porotic hyperostosis (PH) in a contemporary juvenile mortality sample, we noted that males had higher odds of having CO lesions than females. Here, we examine potential reasons for this pattern in greater detail. Four non-mutually exclusive mechanisms could explain the observed sex differences: (1) sex-biased mortality; (2) sexual dimorphism in immune responses; (3) sexual dimorphism in bone turnover; or (4) sexual dimorphism in marrow conversion.

SUBJECTS AND METHODS

The sample consists of postmortem computed tomography scans and autopsy reports, field reports, and limited medical records of 488 individuals from New Mexico (203 females; 285 males) aged between 0.5 and 15 years. We used Kaplan-Meier survival analysis, predicted probabilities, and odds ratios to test each mechanism.

RESULTS

Males do not have lower survival probabilities than females, and we find no indications of sex differences in immune response. Overall, males have a higher probability of having CO or PH lesions than females.

CONCLUSIONS

All results indicate that lesion formation in juveniles is influenced by some combination of sex differences in the pace of red-yellow conversion of the bone marrow and bone turnover. The preponderance of males with CO and PH likely speaks to the potential for heightened osteoblastic activity in males. We find no support for the hypotheses that sex biases in mortality or immune responses impacted lesion frequency in this sample. Sex differences in biological processes experienced by children may affect lesion formation and lesion expression in later life.

Impact of Immunosuppressive Agents on Clinical Manifestations and Outcome of Staphylococcus aureus Bloodstream Infection: A Propensity Score-Matched Analysis in 2 Large, Prospectively Evaluated Cohorts

BACKGROUND

Staphylococcus aureus bloodstream infection (SAB) is a common, life-threatening infection. The impact of immunosuppressive agents on the outcome of patients with SAB is incompletely understood.

METHODS

Data from 2 large prospective, international, multicenter cohort studies (Invasive Staphylococcus aureus Infections Cohort [INSTINCT] and International Staphylococcus aureus Collaboration [ISAC]) between 2006 and 2015 were analyzed. Patients receiving immunosuppressive agents were identified and a 1:1 propensity score-matched analysis was performed to adjust for baseline characteristics of patients. Overall survival and time to SAB-related late complications (SAB relapse, infective endocarditis, osteomyelitis, or other deep-seated manifestations) were analyzed by Cox regression and competing risk analyses, respectively. This approach was then repeated for specific immunosuppressive agents (corticosteroid monotherapy and immunosuppressive agents other than steroids [IMOTS]).

RESULTS

Of 3188 analyzed patients, 309 were receiving immunosuppressive treatment according to our definitions and were matched to 309 nonimmunosuppressed patients. After propensity score matching, baseline characteristics were well balanced. In the Cox regression analysis, we observed no significant difference in survival between the 2 groups (death during follow-up: 105/309 [33.9%] immunosuppressed vs 94/309 [30.4%] nonimmunosuppressed; hazard ratio [HR], 1.20 [95% confidence interval {CI}, .84-1.71]). Competing risk analysis showed a cause-specific HR of 1.81 (95% CI, .85-3.87) for SAB-related late complications in patients receiving immunosuppressive agents. The cause-specific HR was higher in patients taking IMOTS (3.69 [95% CI, 1.41-9.68]).

CONCLUSIONS

Immunosuppressive agents were not associated with an overall higher mortality. The risk for SAB-related late complications in patients receiving specific immunosuppressive agents such as IMOTS warrants further investigations.

Daptomycin versus Vancomycin for the Treatment of Methicillin-Resistant Staphylococcus aureus Bloodstream Infection with or without Endocarditis: A Systematic Review and Meta-Analysis

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of invasive infections, mainly bloodstream infections (BSI) with or without endocarditis. The purpose of this meta-analysis was to compare vancomycin, the mainstay treatment, with daptomycin as therapeutic options in this context. Materials: PubMed, Embase and the Cochrane Database were searched from their inception to 15 February 2020. The primary outcome was all-cause mortality. Secondary outcomes included clinical failure, infection recurrence, persistence of infection, length-of-stay, antibiotic discontinuation due to adverse events (AEs) and 30-day re-admission. This study was registered with PROSPERO, CRD42020169413. Results: Eight studies (1226 patients, 554 vs. 672 in daptomycin vs. vancomycin, respectively) were included. No significant difference in terms of overall mortality was observed [odds ratio (OR) 0.73, 95% confidence interval (CI) 0.40–1.33, I² = 67%]. Daptomycin was associated with a significantly reduced risk of clinical failure (OR 0.58, 95% CI 0.38–0.89, I² = 60%), as confirmed by pooling adjusted effect sizes (adjusted OR against the use of vancomycin 1.94, 95%CI 1.33–1.82, I² = 41%), and was linked with fewer treatment-limiting AEs (OR 0.15, 95%CI 0.06–0.36, I² = 19%). No difference emerged between the two treatments as secondary outcomes. Results were not robust to unmeasured confounding (E-value lower than 95% CI 1.00 for all-cause mortality). Conclusions: Against MRSA BSI, with or without endocarditis, daptomycin seems to be associated with a lower risk of clinical failure and treatment-limiting AEs compared with vancomycin. Further studies are needed to better characterize the differences between the two drugs.

Sex differences in vancomycin-resistant enterococci bloodstream infections-a systematic review and meta-analysis

Background

Vancomycin-resistant enterococci (VRE) have emerged in the healthcare setting worldwide. Infections with these pathogens, i.e., bloodstream infections (BSI), are accompanied with an impaired patient outcome. Diverse factors comprising patient characteristics, therapeutic strategies, and infection control measures are positively or negatively associated with VRE BSI occurrence. However, whether sex-specific differences influence the frequency of VRE BSI is yet unknown.

The aim of this systematic review was to comprehensively summarize and analyze sex prevalence in VRE BSI patients.

Main text

A systematic search for relevant articles was conducted in PubMed and Web of Science. After screening for eligibility, data extraction from included articles and risk of bias assessment were processed. The prevalence of male/female sex in VRE BSI patients and 95% CI were calculated for each study and summarized as pooled estimated effect.

In total, nine articles met the inclusion criteria. Risk of bias assessment resulted in low (six studies) to moderate bias (three studies). The pooled prevalence of male patients suffering from VRE BSI was 59% resulting in a 1.4 male/female prevalence ratio.

Conclusions

Current literature suggests sex differences with male preference (59%) in the distribution of VRE BSI cases. Further primary studies should address the question of male-specific factors favoring the enhanced frequency of VRE BSI.

C-reactive protein predicts complications in community-associated S. aureus bacteraemia: a cohort study

Background

Staphylococcus aureus (S. aureus) bacteraemia is increasingly acquired from community settings and is associated with a mortality rate of up to 40% following complications. Identifying risk factors for complicated S. aureus bacteraemia would aid clinicians in targeting patients that benefit from expedited investigations and escalated care.

Methods

In this prospective observational cohort study, we aimed to identify risk factors associated with a complicated infection in community-onset S. aureus bacteraemia. Potential risk factors were collected from electronic medical records and included: - patient demographics, symptomology, portal of entry, and laboratory results.

Results

We identified several potential risk factors using univariate analysis. In a multiple logistic regression model, age, haemodialysis, and entry point from a diabetic foot ulcer were all significantly protective against complications. Conversely, an unknown entry point of infection, an entry point from an indwelling medical device, and a C-reactive protein concentration of over 161 mg/L on the day of admission were all significantly associated with complications.

Conclusions

We conclude that several factors are associated with complications including already conducted laboratory investigations and portal of entry of infection. These factors could aid the triage of at-risk patients for complications of S. aureus bacteraemia.

Methicillin resistant staphylococci isolated in clinical samples: a 3-year retrospective study analysis

Aim

To determine the prevalence and describe the antimicrobial resistance patterns of circulating methicillin-resistant staphylococci (MRS) isolated from clinical specimens during a 3-year period in Yaoundé, Cameroon.

Materials & methods

From January 2017 to December 2019, 1683 clinical samples were plated onto Mannitol salt agar. Bacterial identification was performed followed by antibiotic susceptibility testing. Data were analyzed using R program.

Results

Staphylococci were identified in 90 (5.35%) of the 1683 clinical samples. Among these, 83.33% were MRS with 78.67% being methicillin-resistant Staphylococcus aureus (MRSA). The prevalence of MRS infection increased significantly with age.

Conclusion

The study offers a good baseline for surveillance intervention to contain antimicrobial resistance and highlights the need to strengthen antimicrobial stewardship and infection, prevention and control programs in the country.

Reduced Mortality of Staphylococcus aureus Bacteremia in a Retrospective Cohort Study of 2139 Patients: 2007-2015

BACKGROUND

Understanding the changing epidemiology of Staphylococcus aureus bacteremia, as well as the variables associated with poor outcomes, can yield insight into potential interventions.

METHODS

This study was a retrospective, observational cohort study of adult patients at an academic medical center in New York City who had S. aureus bloodstream infections between 1 January 2007 and 31 December 2015. Participants were divided into 3 periods: group 1 (2007-2009), group 2 (2010-2012), and group 3 (2013-2015) for trend analysis. All clinical strains were genotyped (spa.). The main outcome was 30-day all-cause mortality.

RESULTS

There were 1264 episodes of methicillin-susceptible S. aureus (MSSA) and 875 episodes of methicillin-resistant S. aureus (MRSA) bacteremia, with a rising proportion due to MSSA (55% group 1; 59% group 2; 63% group 3; P = .03.) There were no significant changes in average age, gender, Charlson score, and distribution of strain genotypes. Mortality in MRSA infection was unchanged (25% group 1; 25% group 2; 26% group 3), while mortality in MSSA infection significantly declined (18% group 1; 18% group 2; 13% group 3). The average time to antistaphylococcal therapy (AST) in MSSA infection declined during the study (3.7 days group 1; 3.5 group 2; 2.2 group 3). In multivariate analysis, AST within 7 days of initial positive MSSA culture was associated with survival.

CONCLUSIONS

Mortality in MSSA bloodstream infection is declining, associated with a decrease in time to targeted therapy. These results emphasize the potential for rapid diagnostics and early optimization of treatment to impact outcomes in MSSA bacteremia.

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.

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.

Comparison of patient characteristics, clinical management, infectious specialist consultation, and outcome in men and women with methicillin-sensitive Staphylococcus aureus bacteremia: a propensity-score adjusted retrospective study

BACKGROUND

Sex-related treatment inequalities are suggested to explain outcome differences between men and women in Staphylococcus aureus bacteremia (SAB). We compared patient characteristics, clinical management, infectious specialist consultation (ISC) and outcome in men and women with SAB.

METHODS

Multicenter retrospective study of methicillin-sensitive (MS-) SAB patients categorized according to sex and ISC consultation provided within 7 days of diagnosis.

RESULTS

Altogether 617 SAB patients were included in the analysis: 62% males and 38% females. Male sex was associated less often to nosocomial bacteremia (OR 0.69, 95% CI 0.50-0.96, p = 0.029) and more often to alcoholism (OR 2.25, 95% CI 1.31-3.87, p = 0.003). No sex-related differences were seen in basic or immunologic laboratory tests, illness severity, intensive care unit treatment or thromboembolic events. ISC was provided to most patients (94%) irrespective of sex. No differences were seen in clinical management of men or women: Transthoracic or -esophageal echocardiography (61% vs. 65%), deep infection (77% vs. 72%), infection removal (30% vs. 27%) and anti-staphylococcal antibiotics as first-line treatment (54% vs. 51%). However, male sex was connected to more frequent adjunctive rifampicin treatment (52% vs. 41%, p = 0.025). No difference in 28- or 90-day mortality (13% vs. 13% and 18% vs. 20%) or SAB relapse (0% vs. 1%) was observed between men and women. Propensity-score adjusted Cox proportional analysis gave no connection of sex to mortality within 90 days.

CONCLUSION

Patient characteristics, clinical management, ISC guidance, bacteremia relapse, and outcome did not differ in men and women with MS-SAB.

The management and outcomes of Staphylococcus aureus bacteraemia at a South African referral hospital: A prospective observational study

OBJECTIVES

Data on the management and outcomes of Staphylococcus aureus bacteraemia (SAB) in resource-limited settings are limited. The aim of this study was to describe a cohort of South African patients with SAB, and explore the factors associated with complicated infection and death.

METHODS

This was a prospective observational study of patients over the age of 13 years admitted to a South African referral hospital with SAB.

RESULTS

One hundred SAB infection episodes occurring in 98 patients were included. SAB was healthcare-associated in 68.4%; 24.0% of all cases were caused by methicillin-resistant S. aureus (MRSA). Ninety-day mortality was 47.0%, with 83.3% of deaths attributable to SAB. There was a trend towards increased 90-day mortality with MRSA infection (odds ratio (OR) 1.28, 95% confidence interval (CI) 1.0-15.1) and the presence of comorbidities (OR 4.1, 95% CI 1.0-21.6). The risk of complicated infection was higher with non-optimal definitive antibiotic therapy (OR 8.5, 95% CI 1.8-52.4), female sex (OR 3.8, 95% CI 1.1-16.3), and community-acquired infection (OR 7.4, 95% CI 2.0-33.1). Definitive antibiotic therapy was non-optimal in 22.6% of all cases.

CONCLUSIONS

SAB-related mortality was high. A large proportion of cases may be preventable, and there is a need for improved antibiotic management.

Gender affects prognosis of methicillin-resistant Staphylococcus aureus bacteremia differently depending on the severity of underlying disease

We aimed to elucidate the potential impact of gender on prognosis of Staphylococcus aureus bacteremia (SAB). We analyzed SAB cases prospectively collected over an 8-year period at 11 hospitals in Korea. SAB-related mortality was pre-defined as a death within 30 days from the onset of SAB without other apparent cause of death. The effect of gender on SAB-related mortality was examined in the entire cohort and in subgroups stratified according to methicillin resistance and Charlson's comorbidity-weighted index (CCWI) score. Those factors independently associated to SAB-related mortality were explored. Among 1974 eligible cases, SAB-related mortality rates in male and female were 21.2% (259/1224) and 21.9% (164/750), respectively (P = 0.786). The SAB-related mortality rate was independently higher in male than that in female in CCWI score ≤ 3 methicillin-resistant SAB (MRSAB) group (15.9 vs. 6.2%; aOR 3.65, 95% CI 1.46-9.13; P = 0.006) while the association tended to be inverse when CCWI score rises. Interaction between CCWI score and gender to MRSAB-related mortality was significant in multivariate analysis (aOR 0.85, 95% CI 0.74-0.96; P = 0.011). There was no significant interaction between gender and CCWI in entire SAB or methicillin-susceptible SAB cohorts. Gender may affect clinical outcomes of MRSAB differently depending on the severity of underlying disease.

The Acid-Base Balance and Gender in Inflammation: A Mini-Review

In humans, acid–base balance is crucial to cell homeostasis. Acidosis is observed in numerous inflammatory processes, primarily acute conditions such as sepsis, trauma, or acute respiratory distress where females tend to exhibit better prognosis compared with males. The mechanisms underlying these gender-dependent differences are multiple, probably involving hormonal and genetic factors, particularly the X chromosome. Although pH influences multiple immunological functions, gender differences in acid–base balance have been poorly investigated. In this review, we provide an update on gender differences in human susceptibility to inflammatory diseases. We additionally discuss the potential impact of acid–base balance on the gender bias of the inflammatory response in view of our recent observation that girls present higher neutrophilic inflammation and lower pH with a trend toward better prognosis in severe sepsis. We also highlight the potent role played by endothelial cells in gender differences of inflammation through activation of proton-sensing G protein-coupled receptors.

Innate Sex Bias of Staphylococcus aureus Skin Infection Is Driven by α-Hemolysin

Numerous studies have reported sex bias in infectious diseases, with bias direction dependent on pathogen and site of infection. Staphylococcus aureus is the most common cause of skin and soft tissue infections (SSTIs), yet sex bias in susceptibility to S. aureus SSTI has not been described. A search of electronic health records revealed an odds ratio of 2.4 for S. aureus SSTI in males versus females. To investigate the physiological basis of this bias, we compared outcomes between male and female mice in a model of S. aureus dermonecrosis. Consistent with the epidemiological data, female mice were better protected against SSTI, with reduced dermonecrosis followed later by increased bacterial clearance. Protection in females was disrupted by ovariectomy and restored by short-term estrogen administration. Importantly, this sex bias was mediated by a sex-specific response to the S. aureus-secreted virulence factor α-hemolysin (Hla). Infection with wild-type S. aureus suppressed inflammatory cytokine production in the skin of female, but not male, mice when compared with infection with an isogenic hla deletion mutant. This differential response was conserved following injection with Hla alone, demonstrating a direct response to Hla independent of bacterial burden. Additionally, neutrophils, essential for clearing S. aureus, demonstrated sex-specific S. aureus bactericidal capacity ex vivo. This work suggests that sex-specific skin innate responsiveness to Hla and neutrophil bactericidal capacity play important roles in limiting S. aureus SSTI in females. Understanding the molecular mechanisms controlling this sex bias may reveal novel targets to promote host innate defense against S. aureus skin infection.

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.