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

Antibiotics Resistance and Adhesive Properties of Clinical Staphylococcus aureus Isolated from Wound Infections

Staphylococcus aureus (S. aureus) is a ubiquitous pathogen responsible for several severe infections. This study aimed to investigate the adhesive properties and antibiotic resistance among clinical S. aureus isolated from Hail Hospital Province, Kingdom of Saudi Arabia (KSA), using molecular approaches. This study was conducted according to the ethical committee at Hail's guidelines on twenty-four S. aureus isolates. A polymerase chain reaction (PCR) was performed to identify genes encoding the β-lactamase resistance (blaZ), methicillin resistance (mecA), fluoroquinolone resistance (norA), nitric oxide reductase (norB), fibronectin (fnbA and fnbB), clumping factor (clfA) and intracellular adhesion factors (icaA and icaD). This qualitative study tested adhesion based on exopolysaccharide production on Congo red agar (CRA) medium and biofilm formation on polystyrene by S. aureus strains. Among 24 isolates, the cna and blaz were the most prevalent (70.8%), followed by norB (54.1%), clfA (50.0%), norA (41.6%), mecA and fnbB (37.5%) and fnbA (33.3%). The presence of icaA/icaD genes was demonstrated in almost all tested strains in comparison to the reference strain, S. aureus ATCC 43300. The phenotypic study of adhesion showed that all tested strains had moderate biofilm-forming capacity on polystyrene and represented different morphotypes on a CRA medium. Five strains among the twenty-four harbored the four genes of resistance to antibiotics (mecA, norA, norB and blaz). Considering the genes of adhesion (cna, clfA, fnbA and fnbB), these genes were present in 25% of the tested isolates. Regarding the adhesive properties, the clinical isolates of S. aureus formed biofilm on polystyrene, and only one strain (S17) produced exopolysaccharides on Congo red agar. All these results contribute to an understanding that the pathogenesis of clinical S. aureus isolates is due to their antibiotic resistance and adhesion to medical material.

Staphylococcus aureus bacteraemia and mortality: a population-based study in Olmsted County, Minnesota, from 2006 to 2020

OBJECTIVES

To provide an evaluation of predictors of 6-month mortality in incident Staphylococcus aureus bacteraemia cases.

METHODS

A retrospective population-based study of 541 adult residents of Olmsted County, MN with monomicrobial S. aureus bacteraemia from 1 January 2006 through 31 December 2020. Multivariable Cox regression was used to investigate risk factors of 6-month mortality.

RESULTS

The median (interquartile range [IQR]) age of 541 patients with S. aureus bacteraemia was 66.8 (54.4-78.5) years and 39.6% were female. The median (IQR) Charlson Comorbidity Index was 6 (3-9). Overall, 144 patients died during the six-month period following their initial episode (30-day and 6-month mortality = 16.5% and 26.7%, respectively). In a multivariable analysis, older age, ICU admission, and unknown source of infection were significant predictors of increased 6-month mortality. In contrast, having an infectious diseases (ID) consultation was associated with reduced mortality in the first 2 weeks of follow-up. Secondary analyses revealed an early benefit of ID consultation during the first 30 days of follow-up and that infective endocarditis was an additional predictor of 6-month mortality.

CONCLUSIONS

To our knowledge, this investigation represents the only US population-based study evaluating predictors of mortality in patients with S. aureus bacteraemia. The finding of a short-term survival benefit associated with early ID consultation may be due to more extensive diagnostic efforts.

A Population-Based Evaluation of Polymicrobial Staphylococcus aureus Bacteremia

OBJECTIVE

To provide an evaluation of incidence and six-month mortality rates of polymicrobial Staphylococcus aureus bacteremia (p-SAB) in the United States (US).

METHODS

A retrospective population-based study of all incident adults with monomicrobial SAB (m-SAB) and p-SAB in Olmsted County, Minnesota (MN) from 1 January 2006, through 31 December 2020, was conducted. Demographics, clinical characteristics, in-hospital outcomes, and six-month survival were compared between groups.

RESULTS

Overall, 31 incident p-SAB cases occurred during the 15-year study period, corresponding to an overall age- and sex-standardized incidence rate of 1.9/100,000 person-years (95% CI, 1.3-2.6). One-third of p-SAB cases were due to MRSA, and almost one-half (15/31) were caused by Gram-positive bacteria. As compared to the 541 cases with incident m-SAB, p-SAB patients were more likely to have a catheter-related infection (p = 0.008) and less likely to be community-acquired cases (p = 0.027). The unadjusted risk of six-month mortality was greater in the p-SAB group (14/31, 45.2%) compared to the m-SAB group (144/541, 26.6%) (HR = 1.94, 95% CI = 1.12-3.36, p = 0.018). After adjusting for relevant covariates, this difference approached significance (HR = 1.93, 95% = CI 0.96-3.87, p = 0.064).

CONCLUSIONS

To our knowledge, the current investigation represents the only US population-based study evaluating p-SAB patients. We found lower incidence rates for p-SAB than previously reported, with almost one-half of the cases caused by Gram-positive bacteria. Furthermore, these patients had poor survival compared to incident m-SAB cases.

Antimicrobial activity of cyanidin-3-O-glucoside-lauric acid ester against Staphylococcus aureus and Escherichia coli

Enzymatic acylation of anthocyanin with fatty acid improves its lipophilic solubility and application potential. Nevertheless, evaluation of functional properties of product is premise for application. This study investigated the antimicrobial potential and the underlying mechanisms of an acylated anthocyanin, namely, cyanidin-3-O-glucoside-lauric acid ester (C3G-LA), to provide guidelines for its application. C3G-LA exhibited outstanding antibacterial activity against Staphylococcus aureus [minimum inhibitory concentration (MIC) = 0.3125 mg/mL] and modest activity against Escherichia coli (MIC = 5 mg/mL). Moreover, C3G-LA manifested bactericide ability against S. aureus at 0.625 mg/mL. Decreases in membrane integrity (by 96% and 92% at MIC in S. aureus and E. coli, respectively), intracellular ATP concentration (by 96% and 92%) and intracellular pH (by 11% and 9%) and changes in cellular morphology altogether indicated the dysfunction of cell membrane under C3G-LA treatment. These findings demonstrated that C3G-LA could be adopted as an alternative food preservative against foodborne pathogens.

Hospital-Wide Protocol Significantly Improved Appropriate Management of Patients with Staphylococcus aureus Bloodstream Infection

Background:Staphylococcus aureus bloodstream infection (SA-BSI) causes morbidity and mortality. We established a management protocol for patients with SA-BSI aimed at improving quality of care and patient outcomes. Methods: A retrospective pre−post intervention study was conducted at Maharaj Nakorn Chiang Mai Hospital from 1 October 2019 to 30 September 2020 in the pre-intervention period and from 1 November 2020 to 31 October 2021 in the post-intervention period. Results: Of the 169 patients enrolled, 88 were in the pre-intervention and 81 were in the post-intervention periods. There were similar demographic characteristics between the two periods. In the post-intervention period, evaluations for metastatic infections were performed more frequently, e.g., echocardiography (70.5% vs. 91.4%, p = 0.001). The appropriateness of antibiotic prescription was higher in the post-intervention period (42% vs. 81.5%, p < 0.001). The factors associated with the appropriateness of antibiotic prescription were ID consultation (OR 15.5; 95% CI = 5.9−40.8, p < 0.001), being in the post-intervention period (OR 9.4; 95% CI: 3.5−25.1, p < 0.001), and thorough investigations for metastatic infection foci (OR 7.2; 95% CI 2.1−25.2, p = 0.002). However, the 90-day mortality was not different (34.1% and 27.2% in the pre- and post-intervention periods, respectively). The factors associated with mortality from the multivariate analysis were the presence of alteration of consciousness (OR 11.24; 95% CI: 3.96−31.92, p < 0.001), having a malignancy (OR 6.64; 95% CI: 1.83−24.00, p = 0.004), hypoalbuminemia (OR 5.23; 95% CI: 1.71−16.02, p = 0.004), and having a respiratory tract infection (OR 5.07; 95% CI: 1.53−16.84, p = 0.008). Source control was the only factor that reduced the risk of death (OR 0.08; 95% CI: 0.01−0.53, p = 0.009). Conclusion: One-third of patients died. Hospital-wide protocol implementation significantly improved the quality of care. However, the mortality rate did not decrease.

Incidence Trends and Epidemiology of Staphylococcus aureus Bacteremia: A Systematic Review of Population-Based Studies

OBJECTIVES

To determine incidence trends of Staphylococcus aureus bacteremia (SAB) from population-based studies from multiple countries.

METHODS

A contemporary systematic review was conducted using Ovid Cochrane Central Register of Controlled Trials (1991+), Ovid Embase (1974+), Ovid Medical Literature Analysis and Retrieval System Online (MEDLINE) (1946+ including epub ahead of print, in-process & other non-indexed citations), and Web of Science Core Collection (Science Citation Index Expanded 1975+ and Emerging Sources Citation Index 2015+). Two authors (J.R.H. and J.A.Q.M.) independently reviewed all studies and included those that reported population-based incidence of SAB in patients aged 18 years and older.

RESULTS

Twenty-six studies met inclusion criteria with the highest number (n=6) of studies conducted in Canada. The incidence of SAB ranged from 9.3 to 65 cases/100,000/year. The median age of patients with SAB ranged from 62 to 72 years and SAB cases were more commonly observed in men than in women. The most common infection sources were intravascular catheters and skin and soft tissue infections. SAB incidence trends demonstrated high variability for geographic regions and calendar years. Overall, there was no change in the incidence trend across all studies during the past two decades.

CONCLUSION

Multiple factors, both pros, and cons are likely responsible for the overall stable SAB incidence in countries included in this systematic review. Some of these factors vary in geographic location and prompt additional investigations from countries not included in the current review so that a more global characterization is defined.