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PubMed2001

Characterization of the importance of Staphylococcus epidermidis autolysin and polysaccharide intercellular adhesin in the pathogenesis of intravascular catheter-associated infection in a rat model.

A rat central venous catheter (CVC) infection model was used to assess the importance of the proteinacious autolysin (AtlE) and the polysaccharide intercellular adhesin (PIA) in the pathogenesis of Staphylococcus epidermidis CVC-associated infection. Wild-type (wt) S. epidermidis O-47 was significantly more likely to cause a CVC infection than was either of the isogenic mutant strains (AtlE-negative [O-47mut1] or PIA-negative [O-47mut2]). Bacteria were retrieved from the explanted catheters of 87.5% of rats inoculated with S. epidermidis O-47, compared with 25% of rats challenged with either S. epidermidis O-47mut1 or O-47mut2 (P=.007). Peripheral bacteremia was documented in 75% of rats challenged with S. epidermidis O-47, compared with 12.5% and 25% challenged with O-47mut1 and O-47mut2, respectively (P=.009). Metastatic disease was more common in rats inoculated with wt S. epidermidis, compared with AtlE- or PIA-deficient mutants. These results confirm the importance of initial adherence, associated with AtlE, and biofilm production, mediated by PIA, in the pathogenesis of S. epidermidis experimental CVC infection.

Animals↗
PubMed1996

Multiresistant Staphylococcus epidermidis in a neonatal care unit.

OBJECTIVE: To study the presence and diversity of types of Staphylococcus epidermidis in the neonatal intensive care unit of a university hospital. METHODS: During a period of 6 weeks, samples were taken from nose, external auditory canal, axilla, groin and umbilicus from consecutively admitted patients. Patients were sampled two times a week for up to 2 weeks. Isolates of S. epidermidis were characterized by antibiogram, plasmid pattern and biotype. RESULTS: Fifteen patients were included. Each patient was sampled in one to four successive surveys, depending on the admission period. A total of 128 isolates of S. epidermidis were obtained and allocated to seven antibiogram types, 36 plasmid types and 14 biotypes. One plasmid type found in 58 isolates (six patients) corresponded with one multiresistant antibiogram type. The number of isolates with these characteristics increased per neonate from the first survey to the fourth. Nineteen isolates from four patients were allocated to a second plasmid type and were of a common antibiogram type. The remaining 34 plasmid types were sporadic. No clear correspondence of biotypes with antibiogram or plasmid types was found. CONCLUSIONS: The present study revealed the increase in colonization of a multiresistant type of S. epidermidis in the compromised patients during admission to the ward. Further studies have to assess whether this type remains persistent in the ward.

Journal Article↗
PubMed2005

Isolation and structural characterization of epilancin 15X, a novel lantibiotic from a clinical strain of Staphylococcus epidermidis.

The potential application of lantibiotics as food-preserving agents and more recently as antibiotics has strongly increased the interest in these antibacterial peptides. Here, we report the elucidation of the primary and three-dimensional structures of the novel lantibiotic epilancin 15X from Staphylococcus epidermidis using high-resolution nuclear magnetic resonance spectroscopy and tandem mass spectrometry. The molecule contains ten post-translationally modified amino acids, three lanthionine ring structures and a hydroxy-propionyl N-terminal moiety. The primary and tertiary structure and the distribution of positive charges are closely similar to the previously identified lantibiotic epilancin K7, most likely indicative of a common mode of action.

Amino Acid Sequence↗
PubMed2006

Effect of iron on the expression of sirR and sitABC in biofilm-associated Staphylococcus epidermidis.

BACKGROUND: Different gene expression patterns correlate with the altered phenotype in biofilm-associated bacteria. Iron and iron-linked genes are thought to play a key-role in biofilm formation. The expression of Fe-linked genes (sirR, sitABC operon) in Staphylococcus epidermidis, was compared in planktonic versus sessile bacteria in vitro and in vivo in a subcutaneous foreign body rat model. RESULTS: In vitro in a Fe-limited environment, the planktonic form of S. epidermidis produces siderophores and grows slower than in Fe-rich environment. The expression of sirR in planktonic bacteria, in vitro, was not different in medium without Fe or with 1 microM FeCl3. High Fe concentrations (25 microM FeCl3) increased expression of sirR transiently during the early phase of incubation. Expression of sitC in vitro, in planktonic bacteria, was inversely correlated with sirR expression in medium with 25 microM FeCl3: sitC expression decreased for the first 3 hours followed by an up regulation.In sessile bacteria in vitro, sirR expression was high and independent of the Fe concentration. The expression of sitC was not inversely correlated to sirR expression. In vivo, expression levels of sirR and of sitABC were high during the initial phase after implantation and, after a transient decrease, remained stable over a period of two weeks. CONCLUSION: Our data suggest that the expression of sirR and the regulatory effect of sirR on the sitABC operon are different in planktonic and sessile bacteria.

Analysis of Variance↗
PubMed1994

Time-kill efficacy of antibiotics in combination with rifampin against Staphylococcus epidermidis biofilms.

Infections associated with implants are frequently resistant to conventional antibiotic therapy. This resistance has been ascribed to the presence of bacteria on the artificial surface within a protective glue-like matrix forming a bacterial biofilm. We have demonstrated that experimental biofilms of Staphylococcus epidermidis, the main pathogen associated with implantation, are exquisitely sensitive to the action of rifampin. This effect of rifampin is incomplete, however, with the emergence of rifampin-resistant survivors that readily repopulate the biofilm. Studies were therefore performed to determine the effect of combinations of 13 different antibiotics with rifampin against standardized S. epidermidis biofilm preparations in an in vitro assay enabling the kinetic measurement of antibiotic action over a five-day period. The antibiotic combinations with rifampin demonstrated unsuspected divergent patterns of antimicrobial activity against the biofilms: 1. rapid synergy with rifampin was observed with cell-wall active antibiotics (cloxacillin, cephalothin, cefazolin, and cefamandole), whereas slower synergy occurred with vancomycin, ciprofloxacin, tetracycline, and amikacin; 2. some antibiotics (tobramycin, erythromycin, clindamycin, fusidic acid) did not influence the outcome; 3. gentamicin unexpectedly showed marked antagonism to rifampin. These results are relevant to the design of optimal therapeutic regimens for the management of resistant implant-associated infections.

Anti-Bacterial Agents↗
PubMed2005

Microplate Alamar blue assay for Staphylococcus epidermidis biofilm susceptibility testing.

Biofilms are at the root of many infections largely because they are much more antibiotic resistant than their planktonic counterparts. Antibiotics that target the biofilm phenotype are desperately needed, but there is still no standard method to assess biofilm drug susceptibility. Staphylococcus epidermidis ATCC 35984 biofilms treated with eight different approved antibiotics and five different experimental compounds were exposed to the oxidation reduction indicator Alamar blue for 60 min, and reduction relative to untreated controls was determined visually and spectrophotometrically. The minimum biofilm inhibitory concentration was defined as < or = 50% reduction and a purplish well 60 min after the addition of Alamar blue. All of the approved antibiotics had biofilm MICs (MBICs) of >512 microg/ml (most >4,096 microg/ml), and four of the experimental compounds had MBICs of < or = 128 microg/ml. The experimental aaptamine derivative hystatin 3 was used to correlate Alamar blue reduction with 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction and viable counts (CFU/ml) for S. epidermidis ATCC 35984, ATCC 12228, and two clinical isolates. For all four strains, Alamar blue results correlated well with XTT (r = 0.83 to 0.97) and with CFU/ml results (r = 0.85 to 0.94). Alamar blue's stability and lack of toxicity allowed CFU/ml to be determined from the same wells as Alamar blue absorbances. If the described method of microplate Alamar blue biofilm susceptibility testing, which is simple, reproducible, cost-effective, nontoxic, and amenable to high throughput, is applicable to other important biofilm forming species, it should greatly facilitate the discovery of biofilm specific agents.

Anti-Bacterial Agents↗
PubMed2000

Comparative in vitro activity of vancomycin and levofloxacin in combination with rifampin against planktonic versus sessile cells of Staphylococcus epidermidis.

STUDY OBJECTIVE: To evaluate the activity of vancomycin and levofloxacin alone and combined with rifampin against planktonic and sessile cells. INTERVENTION: Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the three drugs were determined against a clinical isolate of methicillin-resistant Staphylococcus epidermidis (MRSE 23) and a reference strain of MRSE (ATCC 35984). MEASUREMENTS AND MAIN RESULTS: The MICs/MBCs of vancomycin, levofloxacin, and rifampin against MRSE 23 were 0.78/0.78 microg/ml, 0.19/0.19 microg/ml or below, and 0.19/0.19 microg/ml or below, and against ATCC 35984 were 0.78/1.56 microg/ml, 0.19/0.19 microg/ml or below, and 0.19/0.19 microg/ml or below, respectively. A 99.9% killing activity was achieved with vancomycin, levofloxacin, and vancomycin-levofloxacin against planktonic cells of MRSE 23 (18.9, 21.3, and 17.5 hrs, respectively) and only with levofloxacin against ATCC 35984 (21.5 hrs). No regimen achieved 99.9% killing activity against sessile cells. CONCLUSION: Adding rifampin was antagonistic against planktonic cells and had an additive effect against sessile cells. Activity typically reported using nutrient-rich, planktonic cells may not be applicable to sessile cells under environmental and growth restrictions.

Drug Therapy, Combination↗
PubMed2004

Metabolic activity of Staphylococcus epidermidis is high during initial and low during late experimental foreign-body infection.

Foreign-body infection (FBI) is notoriously resistant to eradication by antibiotic treatment. It is hypothesized that reduced bacterial metabolic activity contributes to this resistance. We examined the metabolic activity of Staphylococcus epidermidis in 204 samples recovered during in vitro foreign-body colonization and in 424 samples recovered during in vivo FBI in a rat model. Metabolic activity was measured by determining the amount of 16S rRNA per genome by quantitative PCR. The initial foreign-body-associated growth proved to be a metabolically active process, both in vitro and in vivo. The initial 16S rRNA content was similar to that observed during in vitro exponential-growth phase. However, during late in vivo FBI, a 114-fold (P << 0.0001) decrease in the 16S rRNA content was observed, indicating that there was markedly decreased metabolic activity. This decreased metabolic activity during late FBI can explain at least in part why such infections are so difficult to eradicate with conventional antibiotic treatment.

Animals↗
PubMed1981

Variable tolerance of a clinical isolate of Staphylococcus epidermidis from an infected hydrocephalus shunt for several beta-lactam antibiotics, vancomycin and fosfomycin.

A strain of Staphylococcus epidermidis isolated from an infected hydrocephalus shunt with associated ventriculitis in a 3-month-old infant proved variably tolerant for the beta-lactam antibiotics ampicillin, cephalothin, cefotaxime, cefoxitin, oxacillin, penicillin G, as well as vancomycin and fosfomycin. In contrast, Staphylococcus aureus control strain ATCC 25923 was regularly tolerant to the above stated beta-lactam antibiotics; however, this latter strain displayed variable tolerance for vancomycin and fosfomycin. The beta-lactam tolerance of both strains proved inoculum sizes. Penicillin G-tolerant variants were detected more readily among cells of the S. epidermidis strain in the stationary than in the logarithmic growth phase; in contrast, the yield of penicillin G-tolerant variants from S. aureus ATCC 25923 was independent of the growth phase. Tolerant variants of both staphylococcal strains failed to survive more than three successive passages in Mueller-Hinton broth with added beta-lactam antibiotics at concentrations identical to those which had originally served to select these tolerant variants. Gentamicin combined with vancomycin displayed additive bactericidal activity against both staphylococcal strains; conversely, the combination of rifampin plus vancomycin showed inadequate bactericidal activity against both strains.

Anti-Bacterial Agents↗
PubMed2002

Quinupristin/dalfopristin bonding in combination with intraperitoneal antibiotics prevent infection of knitted polyester graft material in a subcutaneous rat pouch model infected with resistant Staphylococcus epidermidis.

OBJECTIVE: to investigate the efficacy of quinupristin/dalfopristin in the prevention of prosthetic graft infection in a rat subcutaneous pouch model. METHODS: graft infections were established in the subcutaneous tissue of 140 male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with Staphylococcus epidermidis with intermediate resistance to glycopeptides. The study included one group without contamination, one contaminated group without prophylaxis, one contaminated group that received 50mg/l quinupristin/dalfopristin-soaked graft, one contaminated group that received 10mg/kg intraperitoneal levofloxacin, one contaminated group that received 3mg/kg intraperitoneal doxycycline, and two contaminated groups that received 50mg/l quinupristin/dalfopristin-soaked plus 10mg/kg intraperitoneal levofloxacin or 3mg/kg intraperitoneal doxycycline. Each group included 20 animals. The grafts were removed after 7 days and evaluated by quantitative culture. RESULTS: quinupristin/dalfopristin showed a significantly higher efficacy than levofloxacin and doxycycline, even though quantitative graft cultures for rats that received only quinupristin/dalfopristin-soaked graft showed bacterial growth. Otherwise, the efficacy of levofloxacin was similar to that of doxycycline. Only the group treated with quinupristin/dalfopristin combined with levofloxacin or doxycycline showed no evidence of staphylococcal infection. CONCLUSIONS: quinupristin/dalfopristin as adjunctive topical antibiotic prophylaxis can be useful for the prevention of vascular graft infections caused by staphylococcal strains with high levels of resistance.

Animals↗
PubMed2004

Genomewide analysis of gene expression in Staphylococcus epidermidis biofilms: insights into the pathophysiology of S. epidermidis biofilms and the role of phenol-soluble modulins in formation of biofilms.

Many bacterial pathogens form cellular agglomerations known as biofilms, which considerably limit the success of both antibiotic treatment and the human immune defense. To gain insight into the pathophysiology of the leading nosocomial pathogen, Staphylococcus epidermidis, we analyzed the genome of biofilm-forming S. epidermidis, constructed a microarray representing its entire transcriptome, and performed expression profiling of an S. epidermidis biofilm. Gene-regulated processes in the biofilm led to a nonaggressive and protected form of bacterial growth with low metabolic activity, which is optimally suited to guarantee long-term survival during chronic infection. A class of peptides known as phenol-soluble modulins, which combine proinflammatory activity with a putative role in detachment of biofilms, evolved as potential key determinants controlling the switch between aggressive and quiescent modes of infection. Our data suggest that S. epidermidis adjusts its lifestyle to varying requirements during colonization and infection by means of an expansive change of gene expression. The observed physiological characteristics of the biofilm mode of growth--in particular, the contribution of surfactant-like peptides--might serve as a model for a variety of biofilm-forming pathogens.

Bacterial Toxins↗
PubMed1998

Structure of the pheromone peptide of the Staphylococcus epidermidis agr system.

The agr quorum-sensing system is responsible for the regulation of several virulence factors in staphylococci, with an extracellular pheromone peptide as signalling molecule. By monitoring the biological activity of synthetic peptides, it could be demonstrated that the pheromone of the agr system in Staphylococcus epidermidis is an octapeptide containing a thiolester linkage between the central cysteine and the C-terminal carboxyl group. The peptide was active at nanomolar concentrations. The N-terminus of the peptide pheromone, which is encoded as part of a protein precursor, proved to be crucial for biological activity.

Amino Acid Sequence↗
PubMed1993

Peptidoglycan and teichoic acid from Staphylococcus epidermidis stimulate human monocytes to release tumour necrosis factor-alpha, interleukin-1 beta and interleukin-6.

Cytokines play a major role in the pathophysiology of septic shock. In this study, human peripheral blood monocytes were stimulated with peptidoglycan and teichoic acid, purified from a strain of Staphylococcus epidermidis. Polymyxin B (PM-B) was added to avoid the effects of possible contamination with endotoxin. Tumour necrosis factor-alpha (TNF), interleukin-1 beta (IL-1), and interleukin-6 (IL-6) in the supernates were measured by enzyme-linked immunosorbent assays. Peptidoglycan and teichoic acid induced TNF, IL-1, and IL-6 in a concentration-dependent manner. Teichoic acid was a weaker inducer than peptidoglycan, especially for IL-1. Lipopolysaccharide from an E. coli strain was used as a control, being 100-1000 times more potent than peptidoglycan and teichoic acid.

Enzyme-Linked Immunosorbent Assay↗
PubMed1999

[An animal model of corneal bacterial infection induced by intra-corneal injection of Staphylococcus epidermidis].

PURPOSE: Pharmacokinetic studies of anti-bacterial agents for infectious eye diseases have usually been performed using non-infected rabbit eyes with few studies using infected animal eyes. METHODS: In order to induce bacterial corneal inflammation in rabbit eyes, an intra-corneal injection of Staphylococcus epidermidis was done. The applied bacterial dose was 50 microliters of 1 x 10(4) cfu/ml. RESULTS: The characteristic corneal change was well-defined ulcer formation located in a limited area and relatively elevated. The area surrounding the infected part of the cornea was rather transparent. Using these infected eyes as models, the intraocular drug dynamics of 0.3% Ofloxacin were examined. The model was successfully induced in 78.6% of the rabbits. The drug concentration in the aqueous humor was 2 times higher in the infectious eyes than in the control eyes. CONCLUSION: The model might be useful for drug dynamic studies in infected eyes.

Animals↗
PubMed1994

Isolation and characterization of a novel 20-kDa sulfated polysaccharide from the extracellular slime layer of Staphylococcus epidermidis.

Slime-producing coagulase-negative staphylococci have emerged as important pathogens especially in immunocompromised hosts and patients with implanted devices. Although the extracellular slime layer is considered an important virulence factor, the chemical composition of the slime polysaccharide(s) remains unknown. The crude slime product derived from two reference Staphylococcus epidermidis strains (ATCC 35983 and 35984) and two clinical isolates was found to contain protein (11-20.5%), hexosamines (8-19%), neutral sugars (12.2-14%), phosphates (4-9.5%), uronic acids (1-13%), and small amounts of sulfates (0.5-3%). Preparative anion-exchange chromatography separated a main carbohydrate component which was isolated by combined chromatographies on DEAE-Sephacel and Sepharose CL-6B. HPLC and electrophoreses on polyacrylamide gel and cellulose acetate membrane revealed the presence of one species of low-sulfated polysaccharide with a relative molecular mass of 20-kDa. Chemical analyses of the polysaccharide showed that it is rich in glucosamine (46%) and neutral sugars (30-34%) with small amounts of sulfates (5.7-6.5%) and glucuronic acid (2.9-3.4%). Ten percent of the glucosamine is sulfated at the amino group. The neutral monosaccharides present are glucose, fucose, and xylose with glucose as the predominant one. It is estimated that the polysaccharide consists of 61-65 molecules of glucosamine (6-7 of which are N-sulfated), 30-35 neutral monosaccharides, 3-4 molecules of glucuronic acid, and 1-3 of fucose and xylose. Isolation and characterization of such a polysaccharide from the extracellular slime layer of S. epidermidis has not been previously reported. Its role to pathogenicity remains to be elucidated.

Bacterial Proteins↗