Staphylococcal Bloodstream Infections Research Articles

Caveolin-1 protects endothelial cells from extensive expansion of transcellular tunnel by stiffening the plasma membrane.

Large transcellular pores elicited by bacterial mono-ADP-ribosyltransferase (mART) exotoxins inhibiting the small RhoA GTPase compromise the endothelial barrier. Recent advances in biophysical modeling point toward membrane tension and bending rigidity as the minimal set of mechanical parameters determining the nucleation and maximal size of transendothelial cell macroaperture (TEM) tunnels induced by bacterial RhoA-targeting mART exotoxins. We report that cellular depletion of caveolin-1, the membrane-embedded building block of caveolae, and depletion of cavin-1, the master regulator of caveolae invaginations, increase the number of TEMs per cell. The enhanced occurrence of TEM nucleation events correlates with a reduction in cell height due to the increase in cell spreading and decrease in cell volume, which, together with the disruption of RhoA-driven F-actin meshwork, favor membrane apposition for TEM nucleation. Strikingly, caveolin-1 specifically controls the opening speed of TEMs, leading to their dramatic 5.4-fold larger widening. Consistent with the increase in TEM density and width in siCAV1 cells, we record a higher lethality in CAV1 KO mice subjected to a catalytically active mART exotoxin targeting RhoA during staphylococcal bloodstream infection. Combined theoretical modeling with independent biophysical measurements of plasma membrane bending rigidity points toward a specific contribution of caveolin-1 to membrane stiffening in addition to the role of cavin-1/caveolin-1-dependent caveolae in the control of membrane tension homeostasis.

Caveolin-1 protects endothelial cells from extensive expansion of transcellular tunnel by stiffening the plasma membrane

Large transcellular pores elicited by bacterial mono-ADP-ribosyltransferase (mART) exotoxins inhibiting the small RhoA GTPase compromise the endothelial barrier. Recent advances in biophysical modeling point toward membrane tension and bending rigidity as the minimal set of mechanical parameters determining the nucleation and maximal size of transendothelial cell macroaperture (TEM) tunnels induced by bacterial RhoA-targeting mART exotoxins. We report that cellular depletion of caveolin-1, the membrane-embedded building block of caveolae, and depletion of cavin-1, the master regulator of caveolae invaginations, increase the number of TEMs per cell. The enhanced occurrence of TEM nucleation events correlates with a reduction in cell height due to the increase in cell spreading and decrease in cell volume, which, together with the disruption of RhoA-driven F-actin meshwork, favor membrane apposition for TEM nucleation. Strikingly, caveolin-1 specifically controls the opening speed of TEMs, leading to their dramatic 5.4-fold larger widening. Consistent with the increase in TEM density and width in siCAV1 cells, we record a higher lethality in CAV1 KO mice subjected to a catalytically active mART exotoxin targeting RhoA during staphylococcal bloodstream infection. Combined theoretical modeling with independent biophysical measurements of plasma membrane bending rigidity points toward a specific contribution of caveolin-1 to membrane stiffening in addition to the role of cavin-1/caveolin-1-dependent caveolae in the control of membrane tension homeostasis.

STAPHYLOCOCCAL OSTEOARTICULAR INFECTIONS ASSOCIATED WITH BLOOD STREAM INFECTIONS IN CHILDREN: IS PROLONGED IV ANTIBIOTIC THERAPY ALWAYS INDICATED?

Staphylococcus aureus osteo-articular infections (OAI) are frequently accompanied by blood stream infections (BSI) diagnosed by positive blood culture (BC). Microbiological protocols in adults advise prolonged intravenous antibiotics and repeat BC 48-hourly in the presence of a BSI, however evidence to support the systematic employment of these guidelines in paediatric patients is lacking. We aimed to determine whether there was an increased incidence of orthopaedic and systemic complications in patients with s aureus BSI, and whether a shorter duration of intravenous antibiotics was associated with the development of complications.Following ethical approval, the departmental surgical database was searched for patients that underwent surgery for acute OAI over a 5-year period. Patients with no sample taken for BC were excluded, as were those with other or no organisms identified from any site. Demographic and clinical data were captured, including duration of IV antibiotics and development of complications. Statistical significance was set at p<0.05.Following exclusions, 44 patients with a median age of 85 months remained to be analysed. Thirty patients (68%) had a positive BC. A positive BC was associated with a higher rate of systemic complications (p=0.026) but not orthopaedic complications (p=0.159). Patients who had developed any complication had a significantly longer duration of IV antibiotic treatment compared to those without complications (p<0.001). The presenting CRP levels were significantly higher in patients that developed complications (p=0.004).Patients with staphylococcal BSI in association with an OAI are at increased risk of developing systemic complications. In our cohort, a shorter duration of antibiotic use was not associated with the development of complications, which does not support the systematic use of long courses of IV antibiotics in s aureus BSI. Further research will be required to determine the ideal protocol for these patients.

Predictive models for sepsis in children with Staphylococcus aureus bloodstream infections: a retrospective cohort study

BackgroundThe presence of Staphylococcus aureus in the bloodstream can lead to the development of sepsis; however, the severity and risk factors of the systemic inflammatory response to Staphylococcus aureus bloodstream infections were unclear. This study is aimed to build a model to predict the risk of sepsis in children with Staphylococcus aureus bloodstream infections.MethodsA retrospective analysis of hospitalized pediatric patients diagnosed with Staphylococcus aureus bloodstream infections was performed between January 2013 and December 2019. Each patient was assessed using the pediatric version of the Sequential Organ Failure Assessment score (pSOFA) within 24 h of blood culture collection. A nomogram based on logistic regression models was constructed to predict the risk factors for sepsis in children with Staphylococcus aureus bloodstream infections. It was validated using the area under the receiver-operating characteristic curve (AUC).ResultsOf the 94 patients included in the study, 35 cases (37.2%) developed sepsis. The pSOFA scores ranged from 0 to 8, with 35 patients having a pSOFA score of ≥ 2. Six children (6.4%) died within 30 days, who were all from the sepsis group and had different pSOFA scores. The most common organs involved in sepsis in children with staphylococcal bloodstream infections were the neurologic system (68.6%), respiratory system (48.6%), and coagulation system (45.7%). Hospital-acquired infections (adjusted odds ratio [aOR], 3.0; 95% confidence interval [CI], 1.3–7.2), implanted catheters (aOR, 10.4; 95% CI, 3.8–28.4), procalcitonin level ≥ 1.7 ng/mL (aOR, 15.4; 95% CI, 2.7–87.1), and underlying diseases, especially gastrointestinal malformations (aOR, 14.0; 95% CI, 2.9–66.7) were associated with Staphylococcus aureus sepsis. However, methicillin-resistant Staphylococcus aureus infection was not a risk factor for sepsis. The nomogram had high predictive accuracy for the estimation of sepsis risk, with an AUC of 0.85.ConclusionsWe developed a predictive model for sepsis in children with Staphylococcus aureus infection.

The Relationship Between Antibiotic Agent and Mortality in Patients With Febrile Neutropenia due to Staphylococcal Bloodstream Infection: A Multicenter Cohort Study.

BackgroundMethicillin-susceptible Staphylococcus aureus (MSSA) is a common cause of bloodstream infection (BSI) in patients with febrile neutropenia, but treatment practices vary, and guidelines are not clear on the optimal regimen.MethodsWe conducted a multicenter retrospective cohort study of MSSA BSI in febrile neutropenia. We divided patients into 3 treatment groups: (1) broad-spectrum beta-lactams (ie, piperacillin-tazobactam, cefepime, meropenem); (2) narrow-spectrum beta-lactams (ie, cefazolin, oxacillin, nafcillin); and (3) combination beta-lactams (ie, both narrow- and broad-spectrum). We used multivariable logistic regression to compare 60-day mortality and bacteremia recurrence while adjusting for potential confounders.ResultsWe identified 889 patients with MSSA BSI, 128 of whom had neutropenia at the time of the index culture: median age 56 (interquartile range, 43–65) years and 76 (59%) male. Of those, 56 (44%) received broad-spectrum beta-lactams, 30 (23%) received narrow-spectrum beta-lactams, and 42 (33%) received combination therapy. After adjusting for covariates, including disease severity, combination therapy was associated with a significantly higher odds for 60-day all-cause mortality compared with broad spectrum beta-lactams (adjusted odds ratio [aOR], 3.39; 95% confidence interval [CI], 1.29–8.89; P = .013) and compared with narrow spectrum beta-lactams, although the latter was not statistically significant (aOR, 3.30; 95% CI, .80–13.61; P = .071).ConclusionsUse of combination beta-lactam therapy in patients with MSSA BSI and febrile neutropenia is associated with a higher mortality compared with treatment with broad-spectrum beta-lactam after adjusting for potential confounders. Patients in this study who transitioned to narrow-spectrum beta-lactam antibiotics did not have worse clinical outcomes compared with those who continued broad-spectrum beta-lactam therapy.

Identifying a therapeutic target for vancomycin against staphylococci in young infants.

To determine the therapeutic target of vancomycin in young infants with staphylococcal infections. Retrospective data were collected for infants aged 0 to 90 days with CoNS or MRSA bacteraemia over a 4 year period at the Royal Children's Hospital Melbourne, Australia. Vancomycin broth microdilution MICs were determined. A published pharmacokinetic model was externally validated using the study dataset and a time-to-event (TTE) pharmacodynamic model developed to link the AUC of vancomycin with the event being the first negative blood culture. Simulations were performed to determine the trough vancomycin concentration that correlates with a 90% PTA of the target AUC24. Thirty infants, 28 with CoNS and 2 with MRSA bacteraemia, who had 165 vancomycin concentrations determined were included. The vancomycin broth microdilution MIC was determined for 24 CoNS and 1 MRSA isolate, both with a median MIC of 1 mg/L (CoNS range = 0.5-4.0). An AUC0-24 target of ≥300 mg/L·h or AUC24-48 of ≥424 mg/L·h. increased the chance of bacteriological cure by 7.8- and 7.3-fold, respectively. However, AUC0-24 performed best in the pharmacokinetic-pharmacodynamic model. This correlates with 24 to 48 h trough concentrations of >15-18 mg/L and >10-15 mg/L for 6- and 12-hourly dosing, respectively, and can be used to guide vancomycin therapy in this population. An AUC0-24 ≥300 mg/L·h or AUC24-48 ≥424 mg/L·h was associated with an increase in bacteriological cure in young infants with staphylococcal bloodstream infections.

1110. In Vivo Pharmacodynamics of Vancomycin Against Staphylococci in Young Infants

BackgroundCoagulase-negative staphylococci are the predominant pathogen causing late onset sepsis in young infants, however, the pharmacodynamic target for vancomycin therapy is unknown. This study aimed to determine the pharmacodynamic target of vancomycin in young infants with staphylococcal infections.MethodsRetrospective data were collected for infants aged 0-90 days with methicillin-resistant Staphylococcus aureus (MRSA or coagulase-negative staphylococci (CoNS) bacteraemia over a 4-year period at the Royal Children’s Hospital Melbourne, Australia. Vancomycin broth microdilution minimum inhibitory concentrations (MIC) were determined. A published pharmacokinetic model was externally validated using the study dataset and a time-to-event pharmacodynamic model developed using non-linear mixed effects modelling, with the event being the first negative blood culture. Simulations were performed to determine the 24-hour trough vancomycin concentration correlating with a 90% probability target attainment (PTA) of the area under the curve in the first 24-hours (AUC0-24) exceeding the identified target.ResultsThirty infants, 28 with CoNS and two with MRSA bacteraemia, who had 165 vancomycin concentrations determined were included. The vancomycin broth microdilution MIC was determined for 24 CoNS and one MRSA isolate, both with a median MIC of 1 mg/L (CoNS range 0.5 to 4). An AUC0-24 ≥3 00 mg/L·h was associated with a 7.8-fold increase in the chance of bacteriological cure for all staphylococci at any time point compared to an AUC0-24 < 300 mg/L·h (hazard ratio 95% CI: 3.21-18.8). The 24-hour trough concentrations associated with a 90% PTA of achieving this target were > 13-16 mg/L and > 8-12 mg/L for 6 and 12-hourly dosing, respectively. ConclusionOur study found that an AUC0-24 ≥ 300 mg/L·h was associated with a 7.8-fold increase in bacteriological cure in young infants with staphylococcal bloodstream infections. Disclosures All Authors: No reported disclosures

186. Evaluating Clinical Outcomes for Treatment of Staphylococcal Bloodstream Infection in Patients with Febrile Neutropenia

Background Staphylococcus aureus bloodstream infections (BSIs) in patients with febrile neutropenia (FN) is associated with a mortality rate of up to 49%. For documented infections in patients with FN, guidelines recommend narrowing therapy once susceptibilities result and fever has resolved. Although anti-staphylococcal beta-lactams are the mainstay of treatment for Methicillin-Susceptible and Penicillin-Susceptible Staphylococcus aureus (MSSA and PSSA) BSIs, some clinicians opt to continue broad antibiotics against Pseudomonas during FN. Studies evaluating treatment modalities and outcomes of MSSA and PSSA BSI in patients with FN are lacking.MethodsWe conducted a retrospective cohort study of adult patients with MSSA or PSSA BSI who received antibiotics for the treatment of FN (absolute neutrophil count < 500 cells/L and temperature > 100.4F) at Brigham and Women’s Hospital and Dana-Farber Cancer Institute from 1/2010 to 4/2021. Patients who received < 72-h of antibiotics were excluded. The primary outcome was composite clinical failure (60-day all-cause mortality and/or 60-day BSI recurrence). Other outcomes included inpatient mortality, 60-day readmission, 60-day infection outcomes, incidence of acute kidney injury and hepatotoxicity. Data was analyzed using Chi-Square test or Fisher’s Exact test.ResultsAmong 108 patients who met our criteria, 58% were male, median age was 57 years (IQR 44, 66), 94% had a hematologic malignancy, 4% had a solid tumor, and 2% had both. A total of 41 (38%) received combination therapy with broad spectrum and anti-staphylococcal beta-lactam, 48 (44%) received broad spectrum beta-lactam followed by anti-staphylococcal beta-lactam after neutrophil recovery, and 19 (18%) were narrowed to an anti-staphylococcal beta-lactam prior to resolution of neutropenia. Clinical failure was similar across all treatment arms (34% for combination therapy, 25% for broad spectrum beta-lactam, and 37% for anti-staphylococcal beta-lactam) (Table).Table. Outcomes ConclusionDe-escalation to an anti-staphylococcal beta-lactam prior to neutrophil recovery in FN patients with MSSA or PSSA BSIs did not result in significantly higher clinical failures. Further prospective studies are needed to support antimicrobial stewardship initiatives in oncology patients.Disclosures All Authors: No reported disclosures

High density lipoproteins mediate in vivo protection against staphylococcal phenol-soluble modulins

Staphylococcus aureus virulence has been associated with the production of phenol-soluble modulins (PSMs). These PSMs have distinct virulence functions and are known to activate, attract and lyse neutrophils. These PSM-associated biological functions are inhibited by lipoproteins in vitro. We set out to address whether lipoproteins neutralize staphylococcal PSM-associated virulence in experimental animal models. Serum from both LCAT an ABCA1 knockout mice strains which are characterised by near absence of high-density lipoprotein (HDL) levels, was shown to fail to protect against PSM-induced neutrophil activation and lysis in vitro. Importantly, PSM-induced peritonitis in LCAT−/− mice resulted in increased lysis of resident peritoneal macrophages and enhanced neutrophil recruitment into the peritoneal cavity. Notably, LCAT−/− mice were more likely to succumb to staphylococcal bloodstream infections in a PSM-dependent manner. Plasma from homozygous carriers of ABCA1 variants characterized by very low HDL-cholesterol levels, was found to be less protective against PSM-mediated biological functions compared to healthy humans. Therefore, we conclude that lipoproteins present in blood can protect against staphylococcal PSMs, the key virulence factor of community-associated methicillin resistant S. aureus.

Epidemiology and Pathogenesis of Staphylococcus Bloodstream Infections in Humans: a Review.

Staphylococci are among the most frequent human microbiota components associated with the high level of bloodstream infection (BSI) episodes. In predisposed patients, there is a high risk of transformation of BSI episodes to sepsis. Both bacterial and host factors are crucial for the outcomes of BSI and sepsis. The highest rates of BSI episodes were reported in Africa, where these infections were up to twice as high as the European rates. However, there remains a great need to analyze African data for comprehensive quantification of staphylococcal BSI prevalence. The lowest rates of BSI exist in Australia. Asian, European, and North American data showed similar frequency values. Worldwide analysis indicated that both Staphylococcus aureus and coagulase-negative staphylococci (CoNS) are the most frequent BSI agents. In the second group, the most prevalent species was Staphylococcus epidermidis, although CoNS were not identified at the species level in many studies. The lack of a significant worldwide decrease in BSI episodes indicates a great need to implement standardized diagnostic methods and research etiological factors using advanced genetic methods.

Prevalence of central venous catheter salvage in newborn with staphylococcal bloodstream infection

to establish the prevalence of salvage of central venous catheters in newborns with bloodstream infection caused by coagulase-negative staphylococci. retrospective cross-sectional study with 136 newborns admitted to the Neonatal Intensive Care Unit between 2011 and 2017. The total of 143 infection events undergoing antibiotic therapy were evaluated. among the 143 infection events, 39 catheters in which antibiotic therapy was used were saved and in 69 cases, the device was removed. Positive central blood culture and single lumen catheter were factors associated with salvage failure. The probability of salvage decreased with infections diagnosed from 15 days of using the catheter. Negative blood culture raised the chance of salvage by fourfold. the use of antibiotic therapy in the treatment of infections resulted in a low prevalence of salvage of the central venous catheter. The probability of salvage was associated with variables of the device.

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

BackgroundStaphylococcal 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).MethodsUsing 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.FindingsFrom 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.InterpretationIncidence 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.FundingNo funding was received for this work.

Rational antimicrobial therapy - recommendations for common infections

Infectious diseases are a frequent reason for medical consultations both in the inpatient and outpatient setting. Inadequate management is associated with increased costs, morbidity and mortality. In times of rising antibiotic resistance rational therapy and antimicrobial stewardship are of utmost importance. While it is crucial to avoid excessively broad antimicrobial coverage and unnecessary therapies, serious conditions must be treated effectively. The article highlights common infections and gives recommendations for empiric and targeted antibiotic treatment. Discussed are pulmonary, abdominal, urinary tract, skin and soft tissue infections, as well as sepsis and staphylococcal bloodstream infections. The recommendations consider national and international guidelines, recent publications and current antimicrobial resistance in Germany.

Inhibition of Host Arginase Activity Against Staphylococcal Bloodstream Infection by Different Metabolites.

Staphylococcus aureus is a notorious bacterial pathogen that often causes soft tissue and bloodstream infections and invariably garners resistance mechanisms against new antibiotics. Modulation of the host immune response by metabolites is a powerful tool against bacterial infections, but has not yet been used against S. aureus infections. In this study, we identified four metabolite biomarkers: L-proline, L-isoleucine, L-leucine, and L-valine (PILV), through a metabolomics study using animal models of S. aureus bloodstream infection. The exogenous administration of each metabolite or of PILV showed anti-infective effects, and a higher protection was achieved with PILV in comparison to individual metabolites. During the staphylococcal infection, the expression of most host arginase and nitric oxide synthase (NOS) isozymes was simultaneously induced in mouse liver, kidney, and blood samples. However, the induction of arginase isozymes was dramatically stronger than that of NOS isozymes. This elevated arginase activity was inhibited by the metabolite biomarkers thus killing S. aureus, and PILV exhibited the strongest inhibition of arginase activity and bacterial inhibition. The suppression of arginase activity also contributed to the metabolite-mediated phagocytic killing of S. aureus in mouse and human blood. Our findings demonstrate the metabolite-mediated arginase inhibition as a therapeutic intervention for S. aureus infection.

Hospital-wide ELectronic medical record evaluated computerised decision support system to improve outcomes of Patients with staphylococcal bloodstream infection (HELP): study protocol for a multicentre stepped-wedge cluster randomised trial

IntroductionStaphylococci are the most commonly identified pathogens in bloodstream infections. Identification of Staphylococcus aureus in blood culture (SAB) requires a prompt and adequate clinical management. The detection of coagulase-negative staphylococci...

Clinical efficacy of teicoplanin in the treatment of bloodstream infection caused by methicillin-resistant coagulase-negative staphylococci

Empirical combination therapy with β-lactams and glycopeptides is recommended for patients with presumed staphylococcal bloodstream infection (BSI). While coagulase-negative staphylococci (CNS) remain susceptible to vancomycin, such isolates have become less susceptible to teicoplanin. The aim of this retrospective study was to evaluate the clinical efficacy of teicoplanin in the treatment of BSI caused by methicillin-resistant CNS according to teicoplanin susceptibility. Inclusion criteria were patients with intravascular-catheter related BSIs caused by methicillin-resistant CNS (positive for two or more specimens); teicoplanin therapy; and at least one of the signs or symptoms caused by BSI. Antimicrobial resistance was defined as minimum inhibitory concentration (MIC) ≥8 μg/mL. The primary efficacy endpoint was clinical success evaluated 2 weeks after the completion of teicoplanin therapy [test of cure (TOC)]. Resistant rate of CNS was 0% for vancomycin and 22.9% for teicoplanin, and geometric mean MICs were 1.31 μg/mL and 3.41 μg/mL, respectively (p < 0.001). The catheter was removed in all patients except one, and high early clinical response at 72 h after starting therapy was obtained irrespective of teicoplanin susceptibility. The clinical success rate at TOC was 60% in patients with BSIs caused by teicoplanin-resistant strains, while 90% in patients with BSIs caused by susceptible strains (p = 0.052). In multivariate analyses, teicoplanin resistance was significant factor for decreased clinical success at TOC (adjusted odds ratio 0.138, 95% confidence interval 0.020–0.961, p = 0.045). Because of the poor clinical efficacy of teicoplanin against teicoplanin-resistant CNS, combination therapy comprising vancomycin and β-lactam antibiotics should be considered in presumed staphylococci BSI.

Mechanostability of the Fibrinogen Bridge between Staphylococcal Surface Protein ClfA and Endothelial Cell Integrin αVβ3.

Binding of the Staphylococcus aureus surface protein clumping factor A (ClfA) to endothelial cell integrin αVβ3 plays a crucial role during sepsis, by causing endothelial cell apoptosis and loss of barrier integrity. ClfA uses the blood plasma protein fibrinogen (Fg) to bind to αVβ3 but how this is achieved at the molecular level is not known. Here we investigate the mechanical strength of the three-component ClfA-Fg-αVβ3 interaction on living bacteria, by means of single-molecule experiments. We find that the ClfA-Fg-αVβ3 ternary complex is extremely stable, being able to sustain forces (∼800 pN) that are much stronger than those of classical bonds between integrins and the Arg-Gly-Asp (RGD) tripeptide sequence (∼100 pN). Adhesion forces between single bacteria and αVβ3 are strongly inhibited by an anti-αVβ3 antibody, the RGD peptide, and the cyclic RGD peptide cilengitide, showing that formation of the complex involves RGD-dependent binding sites and can be efficiently inhibited by αVβ3 blockers. Collectively, our experiments favor a binding mechanism involving the extraordinary elasticity of Fg. In the absence of mechanical stress, RGD572-574 sequences in the Aα chains mediate weak binding to αVβ3, whereas under high mechanical stress exposure of cryptic Aα chain RGD95-97 sequences leads to extremely strong binding to the integrin. Our results identify an unexpected and previously undescribed force-dependent binding mechanism between ClfA and αVβ3 on endothelial cells, which could represent a potential target to fight staphylococcal bloodstream infections.

Doing the Same with Less: A Randomized, Multinational, Open-Label, Adjudicator-Blinded Trial of an Algorithm vs. Standard of Care to Determine Treatment Duration for Staphylococcal Bacteremia

BackgroundThe appropriate duration of antibiotics for staphylococcal bloodstream infection (BSI) is unknown. An algorithm to identify patients with staphylococcal BSI who can be safely treated with shorter courses of therapy would improve care and reduce total antibiotic use.MethodsAdult patients with staphylococcal BSI were randomized to treatment based on algorithm-based therapy (ABT) or to standard of care (SOC). Co-primary outcomes were clinical success, as determined by a blinded Adjudication Committee, and serious adverse event (SAE) rates. The prespecified secondary outcome measure was antibiotic days by treatment group, among patients without complicated BSI. Prespecified durations of therapy in ABT were: S. aureus BSI (SAB): uncomplicated: 14 days; complicated: 4–6 weeks. Coagulase-negative staphylococci BSI (CoNSB): simple (1 positive blood culture) (0–3 days), uncomplicated (>1 positive blood culture) (5 days), complicated (7–28 days). Outcomes were compared using intention-to-treat principles. The target sample size was 500 patients, to ensure 90% power for establishing noninferiority within a margin of 15%.ResultsBetween April 2011 and March 2017, 509 adults with suspected staphylococcal BSI at 16 sites in the US and Spain were randomized to ABT (N = 255) or SOC (N = 254). There were 116 patients with SAB (23%) and 385 (76%) with CoNSB (Figure 1). Overall success rate in the ABT group was 82.0% vs. 81.5% in the SOC group, difference 0.5%, 95% CI −5.2% to 6.1%. SAEs were reported in 32.9% of ABT vs. 28.3% of SOC patients (OR 1.2, 95% CI 0.9 to 1.8). Among evaluable patients without complicated BSI, mean duration of therapy was 4.4 days in the ABT group vs. 6.4 days in the SOC group (difference −2.0 days, 95% CI −3.3 to −-0.7, P = 0.003). Among patients with uncomplicated SAB, treatment durations were similar (15.3 days in ABT vs. 16.3 days in SOC, difference −1 day, 95% CI −3.89 to 1.91, P = 0.497), whereas for uncomplicated CoNSB, duration was shorter in the ABT group (5.3 days in ABT vs. 8.4 days in SOC, difference −3 days, 95% CI −4.87 to −1.34, P < 0.001).ConclusionThe use of a treatment algorithm for staphylococcal BSI was associated with significant reductions in duration of antibiotic therapy in patients without complicated BSI, without significant differences in overall success or SAEs.Figure 1.Schematic of Study DesignDisclosures V. Fowler Jr., NIH: Investigator, Contract HHSN272200900023C

Staphylococcal bacteraemia among human immunodeficiency virus positive patients at a screening center in Lagos, Nigeria

Bacteraemia due to Staphylococcus aureus in Human immunodeficiency virus (HIV) – positive patients is associated with increased mortality rate. The present study aimed at determining the species distribution and occurrence of staphylococcal bacteraemia in HIV – positive patients in Lagos, Nigeria. Staphylococcal blood stream infection in febrile HIV patients was investigated by culture technique. The antibiotic resistance pattern was investigated using the disk diffusion and methicillin resistance was confirmed by the salt agar methods. The genetic relatedness of S. aureus was determined using Pulsed Field Gel Electrophoresis (PFGE). Eighty-six patients comprising 47 (55%) female and 39 (45%) male, median aged 34years took part in the study. Staphylococci were identified in 16 (18.6%) patients; 13 (15.1%) and 3 (3.5%) with single and dual Staphylococcus species respectively. The isolates consisted of S. aureus (7 patients), followed by S. haemolyticus (4 patients). Of the thirteen (13) antibiotics tested, isolates were resistant to ampicillin (AMP; 89.5%), tetracycline (TET; 68.4%), cloxacillin (CXC; 89.5%), oxacillin (OXA; 68.4%); chloramphenicol (CHL; 57.9%) and trimethoprim-sulphamethoxazole (SXT; 63.1%). The overall percentage of all the isolates resistant to gentamicin, erythromycin and amoxicillin-clavulanic acid was less than 50%. All the isolates were susceptible to ciprofloxacin and vancomycin and none was positive for methicillin resistance except a strain of S. haemolyticus. Significant genetic diversity was observed among the S. aureus isolates with a predominant pulsotype A. The two isolates with pulsotype A had identical resistotype (AMP, ERY, TET, CXC, SXT). Other PFGE patterns were represented by single isolates except pulsotype C which had a subtype. In these patients, the most frequent Staphylococcus species isolated was S. aureus and the results revealed that clonal dissemination of a virulent pulsotype of S. aureus among this population is plausible and should be a cause for concern.

No survival benefit with empirical vancomycin therapy for coagulase-negative staphylococcal bloodstream infections in infants.

Coagulase-negative Staphylococcus (CoNS) is the most common cause of bloodstream infections (BSI) in hospitalized infants. CoNS BSI is most reliably treated with vancomycin; however, concerns about side effects and promoting resistance often delay empirical vancomycin therapy until culture results become available. All infants with CoNS BSI discharged from 348 neonatal intensive care units managed by the Pediatrix Medical Group from 1997 to 2012 were identified. Empirical vancomycin therapy was defined as vancomycin exposure on the day of the first positive blood culture. Delayed vancomycin therapy was defined as vancomycin exposure 1-3 days after the first positive blood culture. We used multivariable logistic regression with random effects for site to evaluate the association between the use of empirical vancomycin therapy versus delayed vancomycin therapy and 30-day mortality, controlling for gestational age, small-for-gestational age status, postnatal age on the day of the first positive culture, oxygen requirement, ventilator support and inotropic support on the day the first positive culture was obtained. A total of 4364 infants with CoNS BSI were identified; 2848 (65%) were treated with empirical vancomycin. The median postnatal age at first positive culture was 14 days (interquartile range: 9, 21). Unadjusted 30-day mortality was similar for infants treated with empirical vancomycin and infants treated with delayed vancomycin therapy [166/2848 (6%) vs. 69/1516 (4%); P = 0.08]. There was no significant difference in 30-day mortality on multivariable analysis [odds ratio: 1.14 (0.84, 1.56)]. The median duration of bacteremia was 1 day longer for infants with delayed vancomycin therapy [4 days (interquartile range: 2, 6) vs. 3 days (2, 5); P < 0.0001]. The median duration of bacteremia was 1 day longer in infants with CoNS BSI who received delayed vancomycin therapy. Despite this finding, empirical vancomycin therapy for CoNS BSI was not associated with improved mortality.