Staphylococcus Aureus Infection Research Articles

Exhaled Breath Analysis Detects the Clearance of Staphylococcus aureus from the Airways of Children with Cystic Fibrosis.

Electronic nose (eNose) technology can be used to characterize volatile organic compound (VOC) mixes in breath. While previous reports have shown that eNose can detect lung infections with pathogens such as Staphylococcus aureus (SA) in people with cystic fibrosis (CF), the clinical utility of eNose for longitudinally monitoring SA infection status is unknown. In this longitudinal study, a cloud-connected eNose, the SpiroNose, was used for the breath profile analysis of children with CF at two stable visits and compared based on changes in SA infection status between visits. Data analysis involved advanced sensor signal processing, ambient correction, and statistics based on the comparison of breath profiles between baseline and follow-up visits. Seventy-two children with CF, with a mean (IQR) age of 13.8 (9.8-16.4) years, were studied. In those with SA-positive airway cultures at baseline but SA-negative cultures at follow-up (n = 19), significant signal differences were detected between Baseline and Follow-up at three distinct eNose sensors, i.e., S4 (p = 0.047), S6 (p = 0.014), and S7 (p = 0.014). Sensor signal changes with the clearance of SA from airways were unrelated to antibiotic treatment. No changes in sensor signals were seen in patients with unchanged infection status between visits. Our results demonstrate the potential applicability of the eNose as a non-invasive clinical tool to longitudinally monitor pulmonary SA infection status in children with CF.

Rescue of alveolar wall liquid secretion blocks fatal lung injury due to influenza-staphylococcal coinfection.

Secondary lung infection by inhaled Staphylococcus aureus (SA) is a common and lethal event for individuals infected with influenza A virus (IAV). How IAV disrupts host defense to promote SA infection in lung alveoli, where fatal lung injury occurs, is not known. We addressed this issue using real-time determinations of alveolar responses to IAV in live, intact, perfused lungs. Our findings show that IAV infection blocked defensive alveolar wall liquid (AWL) secretion and induced airspace liquid absorption, thereby reversing normal alveolar liquid dynamics and inhibiting alveolar clearance of inhaled SA. Loss of AWL secretion resulted from inhibition of the cystic fibrosis transmembrane conductance regulator (CFTR) ion channel in the alveolar epithelium, and airspace liquid absorption was caused by stimulation of the alveolar epithelial Na+ channel (ENaC). Loss of AWL secretion promoted alveolar stabilization of inhaled SA, but rescue of AWL secretion protected against alveolar SA stabilization and fatal SA-induced lung injury in IAV-infected mice. These findings reveal a central role for AWL secretion in alveolar defense against inhaled SA and identify AWL inhibition as a critical mechanism of IAV lung pathogenesis. AWL rescue may represent a new therapeutic approach for IAV-SA coinfection.

IFP35 aggravates Staphylococcus aureus infection by promoting Nrf2-regulated ferroptosis

IntroductionSerious Staphylococcus aureus (SA) infection is one of the most life-threatening diseases. Interferon-induced protein 35 (IFP35) is a pleiotropic factor that participates in multiple biological functions, however, its biological role in SA infection is not fully understood. Ferroptosis is a new type of regulated cell death driven by the accretion of free iron and toxic lipid peroxides and plays critical roles in tissue damage. Whether ferroptosis is involved in SA-induced immunopathology and its regulatory mechanisms remain unknown. ObjectivesWe aimed to determine the role and underlying mechanisms of IFP35 in SA-induced lung infections. MethodsSA infection models were established using wild-type (WT) and IFP35 knockout (Ifp35−/−) mice or macrophages. Histological analysis was performed to assess lung injury. Quantitative real-time PCR, western blotting, flow cytometry, and confocal microscopy were performed to detect ferroptosis. Co-IP and immunofluorescence were used to elucidate the molecular regulatory mechanisms. ResultsWe found that IFP35 levels increased in the macrophages and lung tissue of SA-infected mice. IFP35 deficiency protected against SA-induced lung damage in mice. Moreover, ferroptosis occurred and contributed to lung injury after SA infection, which was ameliorated by IFP35 deficiency. Mechanically, IFP35 facilitated the ubiquitination and degradation of nuclear factor E2-related factor 2 (Nrf2), aggravating SA-induced ferroptosis and lung injury. ConclusionsOur data demonstrate that IFP35 promotes ferroptosis by facilitating the ubiquitination and degradation of Nrf2 to exacerbate SA infection. Targeting IFP35 may be a promising approach for treating infectious diseases caused by SA.

#3689 RELATIONSHIP BETWEEN STAPHYLOCOCCUS AUREUS NASAL CARRIAGE AND URAEMIC PRURITUS IN HAEMODIALYSIS PATIENTS AND ITS INFLUENCE ON INFECTION

Abstract Background and Aims Uraemic pruritus is a common and distressing comorbid disease among patients undergoing haemodialysis (HD). The aetiology of uraemic pruritus is multifactorial and not fully understood. The role of skin microbiota in chronic inflammatory skin disease has long been discussed, but evidence regarding the relationship between uraemic pruritus and Staphylococcus aureus (SA) colonization is limited. The rate of SA nasal carriage in HD patients was more than double that of healthy individuals, and the phage type of SA infection was often the same as the type of SA carried in the HD patients' nares. SA colonization is associated with greater skin barrier disruption, which suggests a possibility to increase the risk of infection in patients with uraemic pruritus. This study aimed to assess the role of SA nasal carriage in uraemic pruritus, as well as the interplay among SA colonization, uraemic pruritus, and SA infection in HD patients. Method We conducted a prospective cohort study to enrol adult HD patients in the Far Eastern Memorial Hospital, a tertiary medical centre in Taiwan, in April 2019. Eligible patients should had received maintenance HD for more than three months. Patients were excluded if they had active infection or primary skin diseases. The intensity of uraemic pruritus was assessed using a visual analogue scale (VAS) from 0 to 10 (0 = no pruritus, 10 = the worst pruritus imaginable). Nasal swab culture was performed to examine the status of SA nasal carriage. Patients were followed until SA infection, death, or January 2020, whichever had occurred earlier. The definition of SA infection should fulfil both the clinical diagnosis and the results of microbiological culture. Multivariate linear regression models were used to assess the potential predictors for a higher pruritus intensity. Multivariate Cox proportional hazard models were used to analyse the risk of SA nasal carriage on SA infection among the HD patients. Results A total of 100 HD patients were enrolled, the mean age was 61.7 years and 69% were men. The mean dialysis vintage was 6.7 years. Among the participants, 55% had uraemic pruritus and the mean VAS score of pruritus intensity was 4.0. The prevalence of SA nasal carriage was higher in patients with uraemic pruritus than that in patients without uraemic pruritus (33% vs 13%, P = 0.024). The multivariate linear regression model showed that SA nasal carriage was an independent predictor of a higher VAS score of pruritus intensity (parameter estimate, 1.18; 95% CI 0.05-2.30; P = 0.04) (Table 1). After follow-up for 10 months, there were four SA infection events in the pruritus patients and one event in the non-pruritus patients. The multivariate Cox proportional hazard model showed that patients with SA nasal carriage had a borderline higher risk for SA infection (adjusted hazard ratio, 50.9; 95% CI, 0.62-3689; P = 0.08) (Table 2). Conclusion SA nasal carriage is independently associated with uraemic pruritus, and is also an independent predictor for a higher pruritus intensity among HD patients. Moreover, SA colonization might predict SA infection in later follow-up period. This study provide evidence for future studies regarding the survey for SA colonization and application of nasal decolonization among HD patients with uraemic pruritus.

TREATMENT OF INTRACELLULAR S. AUREUS INFECTIONS IN OSTEOMYELITIS

Staphylococcus aureus (SA), the predominant pathogen in human osteomyelitis, is known to persist by forming intracellular reservoirs, including in bone cells (Schwarz et al., 2019, Yang et al., 2018, Krauss et al., 2019, Gao et al., 2020, Bosse et al., 2005), promoting decreased antibiotic susceptibility. However, there are no evidence-based treatment guidelines for intracellular SA infections in osteomyelitis. We sought to address this by systematically reviewing the literature and, testing a selection of antibiotic treatments in a clinically relevant in vitro assay.We conducted a systematic review of the literature to determine the current evidence for the efficacy of antibiotics against intracellular SA infections relevant to osteomyelitis. For the antibiotics identified as potentially useful, we determined their minimal inhibitory concentration (MIC) against 11 clinical osteomyelitis SA- isolates. We selected those for further testing reported able to reach a higher concentration in the bone than the identified MIC against the majority of strains. Thus, rifampicin, oxacillin, linezolid, levofloxacin, oritavancin and doxycycline were tested in human SaOS-2-osteocyte infection models (Gunn et al., 2021) of acute (1d) or chronic (14d) infection to clear intracellular SA. Antibiotics were tested at 1x/4x/10x the MIC for the duration of 1d or 7d in each model.A systematic review found that osteoblasts and macrophages have mostly been used to test immediate short-term activity against intracellular SA, with a high variability in methodology. However, some extant evidence supports that rifampicin, oritravancin, linezolid, moxifloxacin and oxacillin may be effective intracellular treatments. While studies are ongoing, in vitro testing in a clinically relevant model suggests that rifampicin, oxacillin and doxycycline could be effectively used to treat osteomyelitic intracellular SA infections. Importantly, these have lower MICs against multiple clinical isolates than their respective clinically-achievable bone concentrations.The combined approach of a systematic review and disease-relevant in vitro screening will potentially inform as to the best approach for treating osteomyelitis where intracellular SA infection is confirmed or suspected.

Staphylococcus aureus triggers a protective inflammatory response against secondary Cryptococcus gattii infection in a murine model

Prior infections can provide protection or enhance susceptibility to a subsequent infection through microorganism's interaction or host immunomodulation. Staphylococcus aureus (SA) and Cryptococcus gattii (CG) cause lungs infection, but it is unclear how they interact in vivo. This study aimed to study the effects of the primary SA lung infection on secondary cryptococcosis caused by CG in a murine model. The mice's survival, fungal burden, behavior, immune cells, cytokines, and chemokines were quantified to evaluate murine cryptococcosis under the influence of a previous SA infection. Further, fungal-bacterial in vitro interaction was studied in a culture medium and a phagocytosis assay. The primary infection with SA protects animals from the subsequent CG infection by reducing lethality, improving behavior, and impairing the fungal proliferation within the host. This phenotype was associated with the proinflammatory antifungal host response elicited by the bacteria in the early stage of cryptococcosis. There was no direct inhibition of CG by SA, although the phagocytic activity of macrophages was reduced. Identifying mechanisms involved in this protection may lead to new approaches for preventing and treating cryptococcosis.

Staphylococcus Infection: Relapsing Atopic Dermatitis and Microbial Restoration.

Atopic Dermatitis (AD) skin is susceptible to Staphylococcus aureus (SA) infection, potentially exposing it to a plethora of toxins and virulent determinants, including Panton-Valentine leukocidin (PVL) (α-hemolysin (Hla) and phenol-soluble modulins (PSMs)), and superantigens. Depending on the degree of infection (superficial or invasive), clinical treatments may encompass permanganate (aq) and bleach solutions coupled with intravenous/oral antibiotics such as amoxicillin, vancomycin, doxycycline, clindamycin, daptomycin, telavancin, linezolid, or tigecycline. However, when the skin is significantly traumatized (sheathing of epidermal sections), an SA infection can rapidly ensue, impairing the immune system, and inducing local and systemic AD presentations in susceptible areas. Furthermore, when AD presents systemically, desensitization can be long (years) and intertwined with periods of relapse. In such circumstances, the identification of triggers (stress or infection) and severity of the flare need careful monitoring (preferably in real-time) so that tailored treatments targeting the underlying pathological mechanisms (SA toxins, elevated immunoglobulins, impaired healing) can be modified, permitting rapid resolution of symptoms.

Wnt-activating human skin organoid model of atopic dermatitis induced by Staphylococcus aureus and its protective effects by Cutibacterium acnes

SummaryA recently developed human PSC-derived skin organoid model has opened up new avenues for studying skin development, diseases, and regeneration. The current model has limitations since the generated organoids are enclosed, circular aggregates with an inside-out morphology with unintended off-target development of cartilage. Here, we first demonstrated that Wnt signaling activation resulted in larger organoids without off-target cartilage. We optimized further using an air-liquid interface (ALI) culture method to recapitulate structural features representative of human skin tissue. Finally, we used the ALI-skin organoid platform to model atopic dermatitis by Staphylococcus aureus (SA) colonization and infection. SA infection led to a disrupted skin barrier and increased production of epidermal- and dermal-derived inflammatory cytokines. Additionally, we found that pre-treatment with Cutibacterium acnes had a protective effect on SA-infected organoids. Thus, this ALI-skin organoid platform may be a useful tool for modeling human skin diseases and evaluating the efficacy of novel therapeutics.

Mupirocin susceptibility of staphylococci 2022: Is it time for a change in MRSA decolonization protocols?

Nasal decolonization with mupirocin has been a common strategy for the prevention of surgical site infections (SSIs) and recurrent skin and soft tissue infections due to Staphylococcus aureus (SA). We recently noted an increase in SSIs due to SA, including a case of post-operative mupirocin-resistant methicillin-resistant SA (MRSA) infection despite attempted preoperative decolonization with mupirocin. We therefore evaluated the mupirocin susceptibility of SA at our hospital to determine the optimal regimen for decolonization. SA isolates were recovered from clinical and screening samples received in the microbiology laboratory. Mupirocin susceptibility was determined using e-tests and isolates were categorized as susceptible or resistant using a breakpoint MIC value of 4mcg/ml. 223 unique SA isolates from 218 patients were tested. Twenty-four SA isolates (10.8%) were resistant to mupirocin (20 MRSA and 4 methicillin-sensitive SA [MSSA]). MRSA strains were more likely to be resistant to mupirocin than MSSA strains (22.5% vs 3.0%, P < .001). The emergence of drug resistance makes the policy of decolonization with nasal mupirocin a suboptimal strategy for the prevention of MRSA infections. In our study, less than 80% of MRSA strains were mupirocin susceptible. In patients colonized with MRSA at high risk for infection (eg, total joint replacement), other regimens such as intranasal povidone iodine may be preferable to mupirocin for patient decolonization.

Transcriptomics and systems biology identify non-antibiotic drugs for the treatment of ocular bacterial infection

SummaryIncreasing antibiotic resistance among ocular pathogens often results in treatment failure for blinding infections such as endophthalmitis. Hence, newer therapeutics is needed to combat multidrug-resistant infections. Here, we show a drug repurposing approach using a connectivity map based on temporal transcriptomics of Staphylococcus aureus (SA) infected mouse retina. The analysis predicted three non-antibiotic drugs, Dequalinium chloride (DC), Clofilium tosylate (CT), and Glybenclamide (Glb) which reversed the SA infection signatures. Predicted drugs exhibited anti-inflammatory properties in human retinal cells against sensitive and resistant strains of SA. Intravitreal administration of all drugs reduced intraocular inflammation in SA-infected mouse eyes while DC and CT also reduced bacterial burden. Drug treatment improved visual function coinciding with reduced Caspase-3 mediated retinal cell death. Importantly, all drugs exhibited synergy with vancomycin in improving disease outcomes. Overall, our study identified three non-antibiotic drugs and demonstrated their therapeutic and prophylactic efficacies in ameliorating intraocular bacterial infection.

Neonatal Staphylococcus Aureus Sepsis: a 20-year Western Australian experience

ObjectivesThe purpose of this study was to characterise neonatal Staphylococcus aureus (SA) sepsis in Western Australia (WA) between 2001 and 2020 at the sole tertiary neonatal intensive care unit (NICU), examine risk factors for sepsis in the cohort, and compare short- and long-term outcomes to control infants without any sepsis.MethodsRetrospective cohort study at the Neonatal Directorate at King Edward Memorial Hospital (KEMH) and Perth Children’s Hospital, using electronic databases and patient medical records.ResultsThe overall incidence of SA sepsis was 0.10 per 1000 live births (62/614207). From 2001 to 2010 the incidence was 0.13/1000 live births, reducing to 0.07/1000 live births from 2011 to 2020. SA was most frequently isolated from endotracheal aspirates, and infants with SA sepsis had longer median duration of ventilatory support than those without any sepsis (31 days vs 18 days respectively, p < 0.001). In our cohort, SA sepsis was associated with worse neurodevelopmental outcomes compared to infants without any sepsis.ConclusionsThe incidence of neonatal SA sepsis has reduced over the last 20 years, suggesting potential effectiveness of the preventative interventions implemented. Endotracheal tube (ETT) colonisation and prolonged ventilation may be under-recognised as potential sources of SA infection. Our study suggests SA sepsis may negatively impact neurodevelopmental outcomes.

Long non-coding RNA KCNQ1OT1 overexpression promotes osteogenic differentiation of staphylococcus aureus-infected human bone mesenchymal stem cells by sponging microRNA miR-29b-3p

ABSTRACT Osteomyelitis (OM) is an orthopedic disease caused by bone infections in the bone cortex, bone marrow, periosteum, and surrounding soft tissues. Recent studies have implicated non-coding RNAs (ncRNAs) in the development of OM. However, little is known about the role of ncRNAs in the osteogenic differentiation during bone infection. In the present study, we investigated the role of KCNQ1OT1/miR-29b-3p axis in osteogenic differentiation in staphylococcus aureus (SpA)-infected human bone mesenchymal stem cells (hBMSCs). We first examined the expression of lncRNA KCNQ1OT1 and miR-29b-3p in the serum samples of OM patients and healthy controls. We also infected hBMSCs with different concentrations of SpA and studied the osteogenic differentiation after infection. Our results revealed that KCNQ1OT1 was downregulated while miR-29b-3p was upregulated in the serum samples of OM patients, as well as in SpA-infected hBMSCs. Overexpression of KCNQ1OT1 ameliorated the damage in hBMSCs caused by SpA infection. KCNQ1OT1 could support hBMSCs osteogenic differentiation by enhancing ALP activity, alizarin red S accumulation, expressions of osteogenic markers, and attenuating inflammatory responses after SpA infection. We further showed that miR-29b-3p was a downstream target of KCNQ1OT1, mediating the osteogenic differentiation of hBMSCs during SpA infection. Our data suggest that KCNQ1OT1 could ameliorate the SpA-induced suppression of osteogenic differentiation in hBMSCs by sponging miR-29b-3p. Modulating KCNQ1OT1 expression may serve as a strategy to ameliorate osteomyelitis.

Staphylococcus aureus impairs dermal fibroblast functions with deleterious effects on wound healing.

Chronic wounds are a major disease burden worldwide. The breach of the epithelial barrier facilitates transition of skin commensals to invasive facultative pathogens. Therefore, we investigated the potential effects of Staphylococcus aureus (SA) on dermal fibroblasts as key cells for tissue repair. In co-culture systems combining live or heat-killed SA with dermal fibroblasts derived from the BJ-5ta cell line, healthy individuals, and patients with systemic sclerosis, we assessed tissue repair including pro-inflammatory cytokines, matrix metalloproteases (MMPs), myofibroblast functions, and host defense responses. Only live SA induced the upregulation of IL-1β/-6/-8 and MMP1/3 as co-factors of tissue degradation. Additionally, the increased cell death reduced collagen production, proliferation, migration, and contractility, prerequisite mechanisms for wound closure. Intracellular SA triggered inflammatory and type I IFN responses via intracellular dsDNA sensor molecules and MyD88 and STING signaling pathways. In conclusion, live SA affected various key tissue repair functions of dermal fibroblasts from different sources to a similar extent. Thus, SA infection of dermal fibroblasts should be taken into account for future wound management strategies.

Study on the interaction mechanism between C-reactive protein and platelets in the development of acute myocardial infarction.

BackgroundMyocardial infarction (MI) is the single most critical event in coronary disease. Platelets are involved in the processes of acute MI (AMI). They lack nuclear DNA but retain megakaryocyte mRNAs, hence, their transcriptome could provide information preceding coronary events. However, their mechanisms are not clear. In this study, we obtained a gene expression atlas of platelets from patients after their very first AMI, and our purpose was to clarify the mechanisms of platelet involvement in the occurrence of AMI through bioinformatics analyses and animal models of AMI in vivo.MethodsWe obtained a gene expression atlas of platelets from patients after their very first AMI from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were retrieved using R language. Weighted gene co-expression network analysis (WGCNA) was implemented in order to construct a gene co-expression correlation network among DEGs. Animal models of AMI in vivo were constructed to confirm the results of the bioinformatics analysis.ResultsGene integration analysis yielded 2,852 DEGs (P<0.05, |log2FC| >1). Bioinformatics analysis demonstrated a significant association between C-reactive protein (CRP) and Staphylococcus aureus infection (SAI) (P=0.015). Data from in vivo experiments showed that CRP increased significantly in AMI rats (P<0.001), and the expression of FCGR2B mRNA and HLA-DRB4 mRNA was elevated in response to the increase of CRP (P<0.001).ConclusionsFrom the results of this study, we speculate that in the development of AMI, the increase in CRP activates platelets and induces platelets to play an anti-inflammatory role.

255. Ticagrelor Aids Platelet-Mediated Clearance in a Refractory Staphylococcus aureus Endovascular Infection with Septic Emboli

BackgroundThe pore-forming alpha-toxin produced by Staphylococcus aureus (SA) decreases the viability and increases the clearance of platelets, a critical element of innate immune defense in endovascular infection. Our group recently identified that ticagrelor (TICA) blocks alpha-toxin-induced platelet clearance, protecting mice in a lethal systemic SA infection model. Here, we describe a case report in which TICA, added to antimicrobial therapy of a persistent methicillin-susceptible SA (MSSA) bacteremia associated with a septic aortic thrombus, resulted in immediate bacteremia clearance. We further explore TICA synergy with antibiotics and human platelets in vitro.MethodsAntibiotic susceptibility of an MSSA strain from a patient treated with TICA for refractory bacteremia was tested by MIC and checkerboard assays in MHB or RPMI at standard (105 CFU/mL) or high (107 CFU/mL) inocula using TICA, ertapenem (ETP), cefazolin (CZ), or nafcillin (NAF) alone vs. ETP+CZ ± TICA. Killing assays with human platelets ± TICA against SA were also performed.ResultsSA bacteremia secondary to a septic aortic thrombus (>4 mm) with multiple secondary pyogenic foci refractory to standard CZ and subsequent salvage CZ+ETP for 5 days rapidly cleared within 24 h after the addition of TICA. Thrombocytopenia resolved concurrently. Discontinuation of TICA on day 12 led to rebound thrombocytopenia, and TICA was restarted, once again resulting in resolution of thrombocytopenia. TICA alone lacked in vitro activity against SA, nor was TICA synergistic with ETP+CZ. In contrast, addition of a physiological achievable concentration of TICA dramatically sensitized SA to human platelet killing (p< 0.001) in vitro.Figure 1 Figure 2 Figure 3 ConclusionIn a complex case of aortic plaque rupture with septic thrombus, multiple septic emboli, and refractory MSSA bacteremia, addition of TICA to antimicrobial therapy yielded unanticipated immediate clinical and microbiological success. The profound therapeutic effect of TICA in vivo was corroborated by the enhanced staphylocidal activity of human platelets in vitro in the presence of physiological concentrations of the antiplatelet agent. TICA warrants further study as adjunctive treatment of refractory SA bacteremia due to a primary endovascular focus when thrombocytopenia is present.Disclosures Victor Nizet, MD, Centauri Therapeutics (Advisor or Review Panel member)Cidara Therapeutics (Advisor or Review Panel member)InhibRx (Advisor or Review Panel member)Roche Pharmaceutical (Advisor or Review Panel member)

Loranthus acaciae: Alternative medicine for β-lactamase producer and methicillin-resistant Staphylococcus aureus.

Recently, we reported high antibacterial efficiency of Loranthus acaciae (LA) against different standard strains of bacteria including Methicillin-Resistant Staphylococcus aureus (MRSA). Therefore, this study aimed to confirm the effectiveness of LA against clinically isolated Staphylococcus aureus (SA) including β-lactamase producer (Blac) and MRSA. Forty-eight SA isolates collected from various clinical samples were used in this study. Antibiotics susceptibility profile was determined for twenty different antibiotics using automated Microscan Walkaway 96 Plus system as recommended by Clinical and Laboratory Standards Institute (CLSI) guidelines. This system also identified β-lactamase producers and MRSA. In the meantime, LA ethanolic extract was fractionated using liquid–liquid fraction method to hexane, dichloromethane DCM and methanol 80% fractions. Antimicrobial activities of LA extract and fraction were performed with agar well diffusion method for all SA isolates, MIC and MBC were also recorded. Phytochemical screening for various phyto-constituent classes of LA ethanolic extract was determined. Out of 48 SA isolates, Cefoxitin-positive MRSA represent 31 (64.6%), Blac 17 (35.4%), and 41 (85.4%) were multidrug-resistant SA, which was resistant at least to one antibiotic from three different categories. All isolates were resistant to ampicillin and penicillin. Antimicrobial activities of LA extract and fractions revealed that ethanol extract was active against all isolated SA with inhibition zone ranged from 33 ± 2.00 to 25 ± 3.05 mm. While DCM exhibited the largest inhibition zone range from 37 ± 3.00 to 33 ± 2.00 mm. This study is first of its kind conforming the high antibacterial activity of LA against SA isolated from a different source of infection. The study concluded that LA extract and fractions are active and give positive result for all isolated SA. Therefore, suitable pharmacological formulation of LA extract as a promising antibacterial agent for the treatment of SA infection should be given extreme priority.

Type II Natural Killer T Cells Contribute to Protection Against Systemic Methicillin-Resistant Staphylococcus aureus Infection.

Methicillin-resistant Staphylococcus aureus (SA) bacteremia is responsible for over 10,000 deaths in the hospital setting each year. Both conventional CD4+ T cells and γδ T cells play protective roles in SA infection through secretion of IFN-γ and IL-17. However, the role of other unconventional T cells in SA infection is largely unknown. Natural killer T (NKT) cells, a subset of innate-like T cells, are activated rapidly in response to a wide range of self and microbial lipid antigens presented by MHC I-like molecule CD1d. NKT cells are divided into two groups, invariant NKT (iNKT) and type II NKT cells, based on TCR usage. Using mice lacking either iNKT cells or both types of NKT cells, we show that both NKT cell subsets are activated after systemic SA infection and produce IFN-γ in response to SA antigen, however type II NKT cells are sufficient to control bacterial burden and inflammatory infiltrate in infected organs. This protective capacity was specific for NKT cells, as mice lacking mucosal associated invariant T (MAIT) cells, another innate-like T cell subset, had no increased susceptibility to SA systemic infection. We identify polar lipid species from SA that induce IFN-γ production from type II NKT cells, which requires both CD1d-TCR engagement and IL-12 production by antigen presenting cells. We also demonstrate that a population of T cells enriched for type II NKT cells are increased in PBMC of SA bacteremic patients compared to healthy controls. Therefore, type II NKT cells perform effector functions that enhance control of SA infection prior to conventional T cell activation and recognize SA-derived lipid antigens. As CD1d is highly conserved in humans, these CD1d-restricted SA lipid antigens could be used in the design of next generation SA vaccines targeting cell-mediated immunity.

Group 1 CD1-restricted T cells contribute to control of systemic Staphylococcus aureus infection.

Staphylococcus aureus (SA) is the causative agent of both skin/soft tissue infections as well as invasive bloodstream infections. Though vaccines have been developed to target both humoral and T cell-mediated immune responses against SA, they have largely failed due to lack of protective efficacy. Group 1 CD1-restricted T cells recognize lipid rather than peptide antigens. Previously found to recognize lipids derived from cell wall of Mycobacterium tuberculosis (Mtb), these cells were associated with protection against Mtb infection in humans. Using a transgenic mouse model expressing human group 1 CD1 molecules (hCD1Tg), we demonstrate that group 1 CD1-restricted T cells can recognize SA-derived lipids in both immunization and infection settings. Systemic infection of hCD1Tg mice showed that SA-specific group 1 CD1-restricted T cell response peaked at 10 days post-infection, and hCD1Tg mice displayed significantly decreased kidney pathology at this time point compared with WT control mice. Immunodominant SA lipid antigens recognized by group 1 CD1-restricted T cells were comprised mainly of cardiolipin and phosphatidyl glycerol, with little contribution from lysyl-phosphatidyl glycerol which is a unique bacterial lipid not present in mammals. Group 1 CD1-restricted T cell lines specific for SA lipids also conferred protection against SA infection in the kidney after adoptive transfer. They were further able to effectively control SA replication in vitro through direct antigen presentation by group 1 CD1-expressing BMDCs. Together, our data demonstrate a previously unknown role for group 1 CD1-restricted SA lipid-specific T cells in the control of systemic MRSA infection.

P346 The changing epidemiology of infective endocarditis in a tertiary center

Abstract Background Despite the adequate antibiotic prophylaxis, the incidence and mortality rate of infective endocarditis (IE) is still high. In the past few decades, several studies have noted an increase in the proportion of IE caused by staphylococcal species. Aims The aim of our retrospective study was to assess the clinical and microbiological characteristics, trends, and the 1, 6 and 12-month cardiovascular (CV) mortality rate of patients administered for IE in our tertiary hospital between January 1, 2006 and December 31, 2016. Results We identified 465 cases (311 men, 154 women) of 448 patients, mean age was 56,1 ± 16,4 years (14-92). Native left-sided IE (NLIE) was assessed in 286 cases (61,5%, mitral in 117, aorta in 116, combined in 53 cases), prosthetic valve IE (PVIE) was in 111 cases (24%, early in 44, late in 67), right-sided IE (RIE) in 12 cases (2,5%), cardiac device related IE (CDRIE) in 50 cases (11%), other in 6 cases (1%). The underlying infection was caused by streptococci in 124 cases (27%), Staphylococcus aureus (SA) in 112 cases (24%, out of them 23 had MRSA), coagulase negative Staphylococcus (CoNS) in 39 cases (8%), enterococci in 75 cases (16%). Blood culture negative cases found in 61 patients (13%), in 38 cases (8%) other, diversified germs and in 16 cases (4%) there were no data on the pathogen agent. The mortality rates of the total population were one-month was 12.8%, six-month was 26.4%, one-year was 29.7%, and five-year was 40%. There was a significant difference in the mortality rate regarding both of the type of IE and in terms of the underlying microorganism (log-rank p = 0.03 and p = 0.04 resp). The worst survival rate was detected among patients with PVIE, and patients with staphylococcal infection, especially with MRSA. Cox regression found that age (HR: 1.4; CI:1.3-1.6; p &amp;lt;0.001), ejection fraction (HR: 1.4; CI:1.2-1.5; p &amp;lt;0.001), hemoglobin and creatinin levels (HR: 0.9; CI:0.8-0.97 p = 0.01; HR: 1.3; CI: 1.1-1.5; p = 0.001 resp.), MRSA compared to streptococcal infection (HR: 2.5; CI:1.4-4.5; p &amp;lt;0.001), stroke as complication (HR: 1.98; CI:1.4-2.8; p &amp;lt;0.001) were independent risk factors of mortality. In terms of temporal trends the rate of combined NLIE decreased over time (14.5% to 5.1%, p = 0.03), while the rate of other types of IE did not changed. Regarding the type of underlying microorganism the rate of SA infection increased (17% to 41%, p = 0.002) and the rate of CoNS decreased (16.1% - 1.3% p &amp;lt; 0.001) over time. The 1-year mortality rate did not change through the years. Conclusions During the observed 11 years 465 cases were administered with IE to our tertiary hospital, out of which two-third were NLIE. One-quarter of the underlying microorganism were streptococci, and the rate of Staphylococcus aureus infection was increased over time, which was associated with a worse prognosis. In addition IE had a high mortality, which unfortunately did not improve through the years.

Community-acquired Staphylococcus aureus bacteriuria: a warning microbiological marker for infective endocarditis?

BackgroundUrinary tract infection (UTI) is frequently diagnosed in the Emergency Department (ED). Staphylococcus aureus (SA) is an uncommon isolate in urine cultures (0.5–6% of positive urine cultures), except in patients with risk factors for urinary tract colonization. In the absence of risk factors, community-acquired SA bacteriuria may be related to deep-seated SA infection including infective endocarditis. We hypothesized that SA bacteriuria could be a warning microbiological marker of unsuspected infective endocarditis in the ED.MethodsThis is a retrospective chart review of consecutive adult patients between December 2005 and February 2018. All patients admitted in the ED with both SA bacteriuria (104 CFU/ml SA isolated from a single urine sample) and SA bacteremia, without risk factors for UT colonization (i.e., < 1 month UT surgery, UT catheterization) were analyzed. Diagnosis of infective endocarditis was based on the Duke criteria.ResultsDuring the study period, 27 patients (18 men; median age: 61 [IQR: 52–73] years) were diagnosed with community-acquired SA bacteriuria and had subsequently documented bacteremia and SA infective endocarditis. Only 5 patients (18%) had symptoms related to UT infection. Median delay between ED admission and SA bacteriuria identification was significantly shorter than that between ED admission and the diagnosis of infective endocarditis (1.4 ± 0.8 vs. 4.3 ± 4.2 days: p = 0.01). Mitral and aortic valves were most frequently involved by infective endocarditis (93%). Mortality on day 60 reached 56%.ConclusionsThis study suggests that community-acquired SA bacteriuria should warn the emergency physician about a potentially associated left-sided infective endocarditis in ED patients without risk factors for UT colonization.