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Validation of pulsed-field gel electrophoresis and spa typing for long-term, nationwide epidemiological surveillance studies of Staphylococcus aureus infections.

Pulsed-field gel electrophoresis (PFGE) of genomic macrorestriction fragments has been used by the Belgian Reference Laboratory for Staphylococci for national hospital surveys of methicillin-resistant Staphylococcus aureus since 1992. The sequencing of the polymorphic X region of the protein A gene (spa typing) offers significant advantages over PFGE in terms of speed, ease of interpretation, and exportability. To validate its potential use for national surveillance, we evaluated the robustness of spa typing compared with that of PFGE based on a collection of 217 S. aureus strains representative of the Belgian S. aureus epidemiology during the last 13 years. spa typing and PFGE both showed high discriminatory power (discriminatory indexes of 0.98 and 0.96, respectively) and achieved high concordance (95.9%) in type classification. Both methods also showed good concordance with multilocus sequence typing (MLST) (95.5%). However, we observed occasional "violations" of MLST clonal complex assignment by spa typing. Our results suggest that both PFGE and spa typing are reliable methods for long-term, nationwide epidemiological surveillance studies. We suggest that spa typing, which is a single-locus-based method, should preferably be used in combination with additional markers, such as staphylococcal cassette chromosome mec typing or resistance or virulence gene detection.

Anti-Bacterial Agents↗

Interaction with complement receptor 1 (CD35) leads to amelioration of sepsis-triggered mortality but aggravation of arthritis during Staphylococcus aureus infection.

The aim of this study was to assess the importance of complement receptor 1 (CR1, CD35) in Staphylococcus aureus arthritis and sepsis. The murine model of haematogenously acquired septic arthritis was used, injecting toxic shock syndrome toxin 1 (TSST-1)-producing S. aureus LS-1 intravenously. CR1 was blocked using immunoglobulin G (IgG) rat antimouse CR1 monoclonal antibody (MoAb) (8C12). Evaluation of arthritis was performed clinically and histopathologically. In addition, the effect of blocking CR1 was assessed on the phagocytic activity of leucocytes and on T-cell dependent and independent inflammation. Seven days after inoculation with bacteria, 96% of CR1 MoAb-treated mice had clinical symptoms of arthritis compared with 58% of the control animals (P < 0.01). The severity of arthritis, expressed as mean arthritic index, was 2.9 +/- 0.5 and 1.4 +/- 0.5, respectively (P = 0.004). Fifteen days after bacterial inoculation, all CR1 MoAb-treated mice had severe arthritis (mean arthritic index 6.3 +/- 0.6), while only 77% of controls were affected (mean arthritic index 2.9 +/- 0.6; P = 0.002). The potential explanation of these findings is that treatment with CR1 MoAb significantly increases the polymorphonuclear cell-dependent inflammatory response as a result of enhanced vasodilatation in treated animals. We conclude that treatment with CR1 MoAb leads to amelioration of sepsis-induced mortality during S. aureus infection, possibly as a result of the increased phagocytic activity of peripheral phagocytes.

Animals↗

[The effect of the peptide fractions of neutrophilokines on the immune response of mice infected with Staphylococcus aureus].

The influence of immunostimulating and immunosuppressing neutrophilokine fractions on the immune response of mice with staphylococcal infection has been studied. When injected into mice with staphylococcal infection, the immunostimulating fraction of the supernatants of activated neutrophils has been found to restore the activity of the immune system of the infected animals. The secretory products of intact neutrophils do not change or decrease the capacity of the animals for immune response under the conditions of the infectious process.

Animals↗

Erythroderma associated with mixed lymphocyte-endothelial cell interaction and Staphylococcus aureus infection.

We report 11 consecutive cases of erythroderma, a high percentage of which were associated with the growth of Staphylococcus aureus in cultures from blood, joint fluid or skin. In biopsies from all the patients we found close morphological associations between lymphocytes and endothelial cells, with some of the lymphocytes showing features of blastoid transformation to T helper lymphocytes. In extreme cases, sheets of T cells, including T helper lymphocytes, formed a syncytium with endothelial cells in the dermis. Marked capillary proliferation was noted both on light and electron microscopy. We suggest that erythroderma is precipitated by antigens such as protein A, a potent T cell mitogen present on the cell surface of Staphylococcus aureus, or by drugs, such as phenytoin. These antigens induce antigen presentation by individual endothelial cells, leading to T helper transformation and lymphocyte proliferation. Endothelial proliferation resulting from lymphocyte-endothelial interaction results in the vascular proliferation associated with this syndrome.

Adult↗

Vitamin A deficiency predisposes to Staphylococcus aureus infection.

We have investigated the consequences of vitamin A deficiency in a rat model of T-cell-dependent and superantigen-mediated Staphylococcus aureus arthritis. After intravenous inoculation of enterotoxin A-producing staphylococci, the vitamin-A-deficient rats showed a decreased weight gain compared with the paired fed controls despite equal food consumption. The control rats developed arthritis in the first few days after bacterial inoculation, with a peak frequency at day 5, and then gradually recovered; however, the frequency of arthritis 18 days after bacterial inoculation was 86% among the vitamin A-deficient rats and 44% among the control rats. During this period, 3 of 10 deficient rats and 1 of 10 control rats died. Further in vitro analysis revealed that T-cell responses to S. aureus were significantly higher in the vitamin A-deficient rats than in the control animals. In contrast, B-cell reactivity, measured as immunoglobulin levels, autoantibody levels, and specific antibacterial antibody levels in serum, did not differ between the groups. Interestingly, the innate host defense mechanisms against S. aureus were also profoundly affected by vitamin A deficiency. Thus, despite a larger number of circulating phagocytic cells in the vitamin-A-deficient group, the capacity to phagocytize and exert intracellular killing of S. aureus was significantly decreased in comparison with the control rats. Furthermore, serum from the vitamin A-deficient rats inoculated with Staphylococcus aureus displayed decreased complement lysis activity. Our results suggest that the increased susceptibility to S. aureus infection observed in the vitamin-A-deficient rats is due to a concerted action of antigen-specific T-cell hyperactivity, impaired function of the phagocytes, and decreased complement activity.

Adaptation, Biological↗

[Removal of methicillin-resistant staphylococcus aureus infected pacemaker leads under cardiopulmonary bypass: report of a case].

A 71-year-old man, who underwent an intravenous pacemaker implantation previously, suffered from fever and local infection of the generator pocket. A blood culture showed positive for methicillin-resistant staphylococcus aureus (MRSA). He underwent removal of total pacemaker system under cardiopulmonary bypass support successfully. Two leads were tightly adhered to the right atrial free wall, tricuspid valve and right ventricular trabeculation. Postoperative course was uneventful with administration of antibiotics for 5 weeks. Removal under cardiopulmonary bypass is considered to be an effective procedure for treatment of patients with infected pacemaker lead.

Aged↗

Spread of infection, in an animal model, after intramedullary nailing of an infected external fixator pin track.

Implant sepsis. due to previous external fixator pin track infection, is the most common complication of secondary intramedullary (IM) nailing of the tibia. We have developed an animal model, which allows different treatment methods to be studied. Using an established ovine model of a pin track infection, Staphylococcus aureus was used to infect the external fixator pins, two weeks prior to reamed IM nailing. In the control group, the animals were killed at a mean of 10.5 days following nailing, when widespread infection was evident, with septic arthritis, abscess formation, and infection of the entire length of the tibia in all six animals. In the treatment group, before IM nailing, the pin sites were debrided, and both local and systemic antibiotics were administered. All surgical wounds healed without evidence of infection, 4 of the 6 animals survived for 28 days, and bacteria were only isolated from 1 of the 6 implants. Treatment was successful at reducing, but not eliminating, infection after secondary nailing.

Animals↗

Review of Staphylococcus aureus infections requiring admission to a paediatric intensive care unit.

AIMS: To review clinical features and outcome of children with severe Staphylococcus aureus sepsis (SAS) presenting to a paediatric intensive care unit (PICU) with particular focus on ethnicity, clinical presentation, cardiac involvement, and outcome. METHODS: Retrospective chart review of patients coded for SAS over 10 years (October 1993 to April 2004). RESULTS: There were 58 patients identified with SAS over the 10 year study period; 55 were community acquired. This accounted for 4% of hospital admissions for SAS over this time; children with staphylococcal illness comprised 1% of all admissions to the PICU. Maori and Pacific children with SAS were overly represented in the PICU (81%) from a paediatric population where they contribute 21.6%. Musculoskeletal symptoms (79%) dominated presentation rather than isolated pneumonia (10%). An aggressive search for foci and surgical drainage of infective foci was required in 50% of children. Most children had multifocal disease (67%) and normal cardiac valves (95%); the few children (12%) presenting with methicillin resistant S aureus (MRSA) had community acquired infection. The median length of stay in the PICU was 3 (mean 5.8, SD 7.6, range 1-44) days. The median length of stay in hospital was 15 (mean 21, SD 22.7, range 2-149) days. Mortality due to SAS was 8.6% (95% CI 1.4-15.8%) compared with the overall mortality for the PICU of 6% (95% CI 5.3-6.7%). Ten children had significant morbidity after discharge. CONCLUSIONS: Community acquired SAS affects healthy children, is multifocal, and has high morbidity and mortality, in keeping with the high severity of illness scores on admission. It is imperative to look for sites of dissemination and to drain and debride foci. Routine echocardiography had low yield in the absence of pre-existing cardiac lesions, persisting fever, or persisting bacteraemia.

Adolescent↗

Effect of intramammary infusion of bacterial lipopolysaccharide on experimentally induced Staphylococcus aureus intramammary infection.

Mastitis due to Staphylococcus aureus is a significant problem in the dairy industry and is refractory to antibiotic treatment and/or vaccine prevention. Relative to other mastitis-causing pathogens, S. aureus elicits a diminutive host inflammatory response during intramammary infection. To determine whether induction of a heightened inflammatory response could influence outcome of infection, the highly pro-inflammatory molecule bacterial lipopolysaccharide (LPS) was infused into udder quarters experimentally infected with S. aureus. Relative to S. aureus-infected udder quarters receiving saline, quarters infused with LPS demonstrated a heightened inflammatory response as demonstrated by the induction of TNF-alpha and higher milk somatic cell counts and albumin levels. Although there was no overall effect on bacterial clearance, a trend toward reduced bacterial numbers during the immediate pro-inflammatory response following LPS infusion was observed suggesting that this novel approach to treating S. aureus intramammary infection may warrant further investigation.

Animals↗

Sources of intramammary infections from Staphylococcus aureus in dairy heifers at first parturition.

The study objective was to identify probable sources and modes of transmission of 91 Staphylococcus aureus isolates obtained from the colostrum of 76 heifers at parturition. Sources cultured were milk (including colostrum), heifer body sites (teats, muzzle, rectum, vagina, and lacteal secretions), and environmental sites (bedding, insects, housing, water, feedstuffs, humans, nonbovine animals, air, and equipment). Staphylococcus aureus isolates were characterized by 63 phenotypic traits. A similarity coefficient was calculated by herd to identify the S. aureus that most closely resembled the S. aureus obtained from heifer colostrum. Staphylococcus aureus from a heifer's colostrum was compared with all preexisting S. aureus isolates from that heifer's herd. Isolates that were > or = 90% similar were considered to be identical. Because 30 (of the 91) S. aureus isolates from heifer colostrum were collected prior to environmental sampling, only 61 S. aureus isolates from heifer colostrum were available for comparison among all three sources. Possible sources of S. aureus from heifer colostrum at parturition were milk (70%, 43 of 61 isolates), heifer body sites (39%, 24 of 61), environmental sites (28%, 17 of 61), or no identified source (16%, 10 of 61). Three heifers with intramammary infection (IMI) from S. aureus at parturition had the same S. aureus on their teats prior to parturition. Milk was the only source identified for 41% (25 of 61) of isolates from heifer colostrum. Isolates from heifer body sites were the only source identified for 5% (3 of 61) of heifer colostrum isolates. Staphylococcus aureus from the environment was never the sole possible source for S. aureus from heifer colostrum. Data suggest that the major sources of S. aureus IMI in heifers at parturition are milk and heifer body sites. Contact among heifers may be an important mode of transmission of S. aureus leading to IMI in heifers at parturition.

Animals↗

Effects of intrauterine infection by Staphylococcus aureus and Mycoplasma capricolum on the fertility of Nubian goats.

Oestrous cycles were followed by blood progesterone titration and the occurrence of pregnancy was observed after mating in three groups of mature female Nubian goats. Two groups of 4 and 3 goats each were experimentally infected by an in utero injection of either a Staphylococcus aureus or a Mycoplasma capricolum strain of caprine origin. A third group of 4 goats served as a control. Both bacterial infections persisted in all experimental animals, except one, for at least 70 days. As a result, there is a shortening of the first two cycles and progesterone concentration was lower than in the controls. Only one inoculated goat became pregnant after the third oestrus. It is suggested that bacterial inflammation of the uterus may thus modify the oestrous cycle through the prostaglandin pathway.

Animals↗

Can mupirocin prevent methicillin-resistant Staphylococcus aureus infections?

In a retrospective study, Dr Muller and colleagues have assessed the efficacy of mupirocin nasal ointment alongside hygienic measures in methicillin-resistant Staphylococcus aureus (MRSA)-positive patients admitted to the intensive care unit (ICU). Their findings, which suggest that intranasal mupirocin can prevent ICU-related MRSA infections, need confirmation in a well-designed clinical trial. In general: early identification, isolation and treatment of all MRSA carriers, including health care workers, and disinfection of contaminated environments, are the main 'ingredients' of an effective MRSA 'search and destroy' program.

Administration, Intranasal↗

Efficacy of dicloxacillin-coated polyurethane catheters in preventing subcutaneous Staphylococcus aureus infection in mice.

In a mouse model, dicloxacillin-coated polyurethane catheters or control (uncoated) catheters were placed subcutaneously and then Staphylococcus aureus was inoculated at the time of insertion, 24 or 48 h later. The in vivo half-life of the antibiotic was 11 to 16 h. When 10(5) CFU of S. aureus were inoculated at the time of catheter insertion, dicloxacillin-coated catheters kept the number of S. aureus removed from catheters by sonication below 10(2) CFU at 12, 24, 48, and 96 h after inoculation compared with titers greater than 10(3.5) CFU for control catheters (P less than 0.05). When S. aureus was inoculated 24 h after catheter insertion, control catheters averaged greater than 10(2) CFU of S. aureus removed compared with less than 10(1.5) CFU for the dicloxacillin-coated catheters (P less than 0.05). No difference was found between coated and control catheters when S. aureus was inoculated 48 h after catheter insertion, but S. aureus titers averaged less than 10(2) CFU for all experimental groups. Our data suggest that in mice, regional prophylaxis of S. aureus subcutaneous space infection is feasible with catheters coated with dicloxacillin and that the presence of antibiotic is only necessary for the first 24 to 48 h.

Animals↗

Evaluation of intraspecies interference due to agr polymorphism in Staphylococcus aureus during infection and colonization.

In Staphylococcus aureus infection, intraspecies cross-inhibition mediated by the regulatory system agr may lead to the exclusion of heterologous strains at the site of infection or colonization. We analyzed consecutive and cocolonizing strains (classified as different clones by pulsed-field gel electrophoresis) from patients with cystic fibrosis (CF) and healthy individuals. Strain replacement was accompanied by a change in the agr group in 80% of the patients with CF and in 63% of the healthy individuals. Cocolonizing strains from patients with CF were shown to belong to interfering agr groups in 6 of 10 cases. In contrast, in healthy individuals, cocolonization of the nares with strains of interfering agr groups was rarely observed. agr polymorphism has no impact on the colonization dynamics of S. aureus in patients with CF but may influence nasal colonization in health individuals.

Bacterial Proteins↗

[Staphylococcus epidermidis infective endocarditis after mitral surgery, successfully treated with aspirin and antibiotics: a case report].

We report a case of infectious endocarditis from Staphylococcus epidermidis that occurred early after mitral valve repair (one month), suggested by fever of 38.5 degrees C and valvular vegetations of less than 10 mm on the mitral valve. In the absence of standard recommendations (medical or surgical) in treating patients with infectious endocarditis occurring after mitral valve repair, and in the absence of complications, a medical regimen was chosen associating aspirin (anti-aggregant dosages) with antibiotics. The benefit of aspirin in endocarditis has been demonstrated in experimental studies with regards to valvular vegetations and embolic risk but remains to be studied in human clinical trials. With the association of aspirin (100 mg/d) and triple antibiotic therapy (rifampicin 1200 mg/d, vancomycin 2 g/d, gentamycin 180 mg/d), the clinical status improved with complete regression of vegetations in less than 24 days and the absence of recurrence at one-year follow-up.

Adult↗