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[A case report of early prosthetic valve endocarditis due to methicillin resistant Staphylococcus aureus infection--an experience of intraatrial implantation of mitral prosthesis with a Gore-Tex flange].

A 60-year-old female with mitral stenosis developed prosthetic valve endocarditis due to methicillin resistant staphylococcus aureus septicemia 3 weeks after mitral valve replacement. In vitro test disclosed susceptibility to minocycline and clindamycin. Despite large amount of intravenous administration, progressive heart failure due to massive perivalvular leakage occurred as a consequence of persisting infection. An emergent operation revealed valve detachment of the posterior portion resulting from ring abscess formation. A mitral prosthesis with a Gore-Tex flange was implanted partially in the left atrium just above the mitral ring and sutured to the atrial wall. Postoperative relapse was not detected even after discontinuing antibiotics. Prosthetic valve endocarditis due to methicillin resistant staphylococcus aureus is highly resistant to antibiotic therapy and likely to develop valve ring abscess. Prompt surgical treatment is mandatory in this situation.

Endocarditis, Bacterial↗

Molecular epidemiology of panton valentine leukocidin-producing Staphylococcus aureus infections, Djibouti, 2018-2023.

Between 2018 and 2023, a genomic study was conducted in a military camp in Djibouti to investigate the molecular epidemiology of Panton-Valentine Leukocidin-producing Staphylococcus aureus. Among 43 isolates, Sequence Type 152 was predominant (72%), mainly associated with spa types t355 and t4235. Core-genome Multi-Locus Sequence Typing revealed two concurrent transmission dynamics: localized inter-human outbreaks and repeated introductions from external sources. Comparative genomics with other African Sequence Type 152 isolates showed similar levels of diversity, suggesting a widespread continental dissemination. These findings highlight the importance of genomic surveillance to better understand and control the spread of this virulent lineage in Africa.

Leukocidins↗

Staphylococcus aureus infection in haemodialysis patients. Mupirocin as a topical strategy against nasal carriage: a review.

Staphylococcus aureus is isolated from 42% of the bacteraemic episodes occurring in haemodialysis patients. Several epidemiological studies indicate that nasal carriage of S. aureus is of pivotal importance in determining the risk of subsequent infections by this micro-organism in haemodialysis patients. First, nasal carriage is prevalent in about 42% of these patients, this high rate being observed from the onset of maintenance dialysis therapy. Second, there is a significant relationship between nasal and hand carriage of the organisms. Third, there is usually a similarity between infecting S. aureus strains and those isolated from nasal surveillance cultures obtained from the same patient. The nares are therefore an elective site for the prevention of S. aureus infections in haemodialysis patients; this was shown with oral rifampin. The studies demonstrating the effectiveness of nasal mupirocin for this indication are summarised. The need for continued chemosuppression with maintenance application (e.g. once per week) is underscored. Such a long-term application of nasal mupirocin in haemodialysis patients with nasal carriage is very cost-effective and is only very rarely associated with the emergence of mupirocin resistance in S. aureus.

Administration, Intranasal↗

Staphylococcus aureus infection of mouse or human osteoblasts induces high levels of interleukin-6 and interleukin-12 production.

Staphylococcus aureus is the principal causative agent of the inflammatory bone disease osteomyelitis. Unfortunately, the pathogenesis of this often chronic infection is poorly understood and is complicated by the recent observation that bone-forming osteoblasts can harbor S. aureus. Such an infection presents a significant challenge for the host immune response, because osteoblasts are not known to initiate protective cell-mediated immune responses. Cultured mouse and human osteoblasts infected with S. aureus were found to express high levels of interleukin (IL)-6 and IL-12p75, on the basis of complementary investigations demonstrating both S. aureus-induced up-regulation of expression of IL-6 and IL-12p40 mRNA and secretion of IL-6 and IL-12p75 by these cells. Additionally, a quantitative bioassay demonstrated that IL-12p75 secreted after infection was biologically active. These studies are the first to demonstrate induced IL-12p75 expression by osteoblasts and suggest a previously unrecognized role for osteoblasts in initiating immune responses after S. aureus infection.

Animals↗

Trends and outcome of nosocomial and community-acquired bloodstream infections due to Staphylococcus aureus in Finland, 1995-2001.

In Finland, Staphylococcus aureus bloodstream infections are caused predominantly (>99%) by methicillin-sensitive strains. In this study, laboratory-based surveillance data on Staphylococcus aureus bloodstream infections occurring in Finland from 1995 to 2001 were analyzed. Preceding hospitalizations for all persons with Staphylococcus aureus bloodstream infections were obtained from the national hospital discharge registry, and data on outcome was obtained from the national population registry. An infection was defined as nosocomial when a positive blood culture was obtained more than 2 days after hospital admission or within 2 days of admission if there was a preceding hospital discharge within 7 days. A total of 5,045 cases were identified. The annual incidence of Staphylococcus aureus bloodstream infection rose by 55%, from 11 per 100,000 population in 1995 to 17 in 2001. The increase was detected in all adult age groups, though it was most distinct in patients >74 years of age. Nosocomial infections accounted for 51% of cases, a proportion that remained unchanged. The 28-day death-to-case ratio ranged from 1% in the age group 1-14 years to 33% in patients >74 years of age. The 28-day death-to-case ratios for nosocomial and community-acquired infections were 22% and 13%, respectively, and did not change over time. The increase in incidence among elderly persons resulted in an increase in the annual rate of mortality associated with Staphylococcus aureus bloodstream infections, from 2.6 to 4.2 deaths per 100,000 population per year. Staphylococcus aureus bloodstream infections are increasing in Finland, a country with a very low prevalence of methicillin resistance. While the increase may be due in part to increased reporting, it also reflects a growing population at risk, affected by such factors as high age and/or severe comorbidity.

Adolescent↗

Arteries from human beings are less infectible by Staphylococcus aureus than polytetrafluoroethylene in an aortic dog model.

PURPOSE: Treatment of aortoiliac prosthetic graft infections includes the removal of the infected material and repeat revascularization if necessary. The risk of infection of the graft material used for the repeat revascularization has been the drawback of its use in situ except with autografts. Good results were obtained in this setting by use of in situ arterial allografts. The purpose of our study was to compare in vivo the infectibility of arteries used as allografts to the infectibility of commercially available prostheses. METHODS: Twelve dogs underwent thoracoabdominal aortic bypass with use of either an artery from a human being (n=6) or an expanded polytetrafluoroethylene (ePTFE) graft (n=6). One month later, bacteremia was produced with Staphylococcus aureus. One week after bacterial challenge, the animals were killed to recover the grafts. Each graft then underwent bacterial study. RESULTS: None of the arterial grafts grew bacteria, whereas four of the six ePTFE grafts (p < 0.05) did. In addition, none of the fragments of the arterial grafts grew bacteria, whereas 24 of the 60 ePTFE fragments (p < 0.01) did. CONCLUSION: Nonautologous arteries are less infectible than ePTFE in vivo. This decreased infectibility makes the arterial allograft an appealing material when revascularization must be performed in a contaminated field.

Animals↗

Human immunoglobulin G recognizing fibrinogen-binding surface proteins is protective against both Staphylococcus aureus and Staphylococcus epidermidis infections in vivo.

A human donor-selected immunoglobulin G for intravenous injection (IGIV) product with elevated titers against the staphylococcal fibrinogen-binding MSCRAMM proteins ClfA and SdrG (INH-A21) was tested in vitro and in vivo. INH-A21 contained a significantly increased ability to inhibit the fibrinogen-binding activity of recombinant forms of both ClfA and SdrG. Evaluation of the opsonizing potential of INH-A21 was evaluated using fluorescently labeled bacteria; this assay indicated an increase in phagocytic activity compared to normal IGIV. The prophylactic efficacy of INH-A21 against an intraperitoneal challenge of methicillin-resistant Staphylococcus epidermidis (MRSE) was evaluated in a neonatal rat model. INH-A21 was also evaluated for prophylactic and therapeutic efficacy in a rabbit model of catheter-induced aortic valve infective endocarditis caused by either MRSE or methicillin-resistant Staphylococcus aureus (MRSA). Results from the in vivo models demonstrated potent prophylactic and therapeutic efficacy against both MRSE and MRSA. These data suggest that INH-A21 may be an important tool for the prevention and treatment of staphylococcal infections, especially in high-risk populations.

Animals↗

Immunoglobulin allotypes and genetic susceptibility to invasive Haemophilus influenzae type b and Staphylococcus aureus infections in South African children.

OBJECTIVE: The purpose of this study was to determine whether the G2m(n), G1m(f) and Km(3) immunoglobulin allotypes have any association with susceptibility to invasive Haemophilus influenzae type b (Hib) and Staphylococcus aureus (S. aureus) infections in children. METHODS: Direct enzyme-linked immunosorbent assays with commercially available monoclonal antibodies were established to quantitate G2m(n) and G1m(f) allotypes. A qualitative enzyme-linked immunosorbent assay with polyclonal rabbit anti-Km(3) antibody was established for Km(3) determination. RESULTS: The G2m(n) marker occurred in 34.4% of the mixed ancestry population and 2.9% of the Black population. There was a significantly decreased frequency of the G2m(n) allotype in mixed ancestry children with Hib meningitis (8.5%) and Hib osteomyelitis/septic arthritis and a decreased frequency of Km(3) in black and mixed ancestry children with Hib meningitis. The frequency of G2m(n), G1m(f) and Km(3) allotypes in patients with S. aureus osteomyelitis/septic arthritis were not significantly different from normal population frequency. CONCLUSIONS: This study shows a clear association between the absence of the G2m(n) allotype in mixed ancestry children and susceptibility to invasive infections caused by H. influenzae and an association between the absence of Km(3) and Hib meningitis in both black and mixed ancestry children.

Arthritis, Infectious↗

Live cell imaging of phagosome maturation in Staphylococcus aureus infected human endothelial cells: small colony variants are able to survive in lysosomes.

Small colony variants (SCVs) of Staphylococcus aureus have been proposed to persist within vascular endothelium, thereby sustaining chronic infections. To identify the intracellular SCV location we infected primary human endothelial cells with various wild type and SCV strains of S. aureus and visualised maturation of phagosomes using live cell imaging. Staphylococci-containing phagosomes were matured by sequential and dynamic interactions with Rab5- and Rab7-positive vesicles. Within 45-60 min all internalised staphylococci accumulated in LAMP-1- and LysoTracker-enriched lysosomal organelles and remained there for up to 5 days. Recovery of most staphyloccocal strains was below 1% after a 24 h intracellular stay, indicating a high bactericidal activity of the endothelial cell lysosomes. However, the menadione auxotroph SCV strain JB1 displayed a recovery rate of 4% and, furthermore, through multiple intracellular passaging a subtype (JB1-P4) with a recovery rate of 25-30% could be generated. Interestingly, both JB1 and JB1-P4 also resided exclusively in lysosomes. Thus, on one hand we document effective bactericidal activity of human endothelial cell lysosomes towards staphylococci, and on the other hand we provide evidence that certain SCVs are capable to withstand this activity.

Endothelial Cells↗

Mixed infection by Staphylococcus and Candida, and Wegener's granulomatosis.

We describe the case of a patient who initially presented with pneumonia from Staphylococcus aureus and Candida parapsilosis, which was resolved with antibiotic treatment, but reappeared 6 months later as full-blown Wegener's granulomatosis. The possible pathogenetic correlations between infective agents, in particular Staphylococcus aureus and Candida, and Wegener's granulomatosis are discussed.

Adult↗

Isolation and characterization of a highly specific serine endopeptidase from an oral strain of Staphylococcus epidermidis.

Infection by Staphylococcus epidermidis, an opportunistic pathogen, has become a major problem due to the increased use of implanted medical devices and the growing number of patients who are therapeutically or infectiously immunosuppressed. These infections appear to proceed via modulation of the coagulation and complement systems. In this communication we describe the purification and characterization of a novel extracellular proteinase from an oral strain of S. epidermidis that can degrade fibrinogen, complement protein C5, and several other proteins. This proteinase has a strong preference for cleavage after glutamic acid residues, but not after aspartic acid. The S. epidermidis enzyme may be a multifunctional protein which not only provides this organism with both the ability to evade the complement defense system and to dysregulate the coagulation cascade, but also supplies nutrients for its growth through the degradation of Glu-rich proteins.

Amino Acid Sequence↗

Characterization of a widespread strain of methicillin-susceptible Staphylococcus aureus associated with nosocomial infections.

Thirty Staphylococcus aureus isolates from five hospitals were determined to exhibit borderline susceptibility to the antistaphylococcal penicillins. Of the isolates submitted for phage typing, 96% belonged to phage group 94/96, and 96% possessed a common plasmid, pBW15. Also, four reference borderline-susceptible isolates from the Centers for Disease Control belonged to phage group 94/96 and possessed pBW15. Screening of 43 other phage group 94/96 isolates demonstrated that 36 (84%) contained pBW15 and exhibited the borderline phenotype. In contrast, pBW15 was not identified among 10 penicillin-susceptible, 10 methicillin-resistant, and 40 penicillin-resistant but non-borderline-susceptible S. aureus. These data show a close association between pBW15, phage group 94/96, and the borderline-susceptible phenotype. Furthermore, these isolates were associated with infections in multiple institutions, suggesting the widespread dissemination of a clinically important and pathogenic strain of S. aureus.

Bacteriophage Typing↗

Prior elevation of IL-18 promotes rapid early IFN-gamma production during staphylococcal infection.

Systemic Staphylococcus aureus infection is associated with significant morbidity and mortality arising from both bacterial and host immune factors. IL-18 is a pro-inflammatory cytokine of the IL-1 superfamily that exhibits broad functional effects in innate and acquired immune responses and which has been found in high levels in several chronic inflammatory and autoimmune diseases. Over-expression of IL-18 may promote early resolution of infection or could promote a detrimental exaggerated immune response. This was explored in a model of S. aureus infection. We report increased mortality in Swiss mice that were given recombinant IL-18 prior to inoculation with S. aureus LS-1. IL-18 administration prior to infection induced preferentially enhanced IFN-gamma mRNA expression in peripheral blood leukocytes and spleen, especially splenic NK cells. This correlated with increased IFN-gamma protein detection in serum, and leukocyte and spleen cultures at subsequent discrete time points. These data suggest that increased mortality following gram-positive infection in autoimmune diseases could in part reflect the impact of high levels of pleiotropic pro-inflammatory cytokines such as IL-18 present prior to the onset of infection.

Animals↗