322,931 research outputs found
Prevalence of cna, fnbA and fnbB adhesin genes among Staphylococcus aureus isolates from orthopedic infections associated to different types of implant.
No full textFEMS Microbiol Lett. 2005 May 1;246(1):81-6.
Prevalence of cna, fnbA and fnbB adhesin genes among Staphylococcus aureus isolates from orthopedic infections associated to different types of implant.
Arciola CR, Campoccia D, Gamberini S, Baldassarri L, Montanaro L.
Research Unit on Implant Infections, Rizzoli Orthopedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy. [email protected]
Here are reported data on virulence determinants of Staphylococcus aureus from orthopedic surgical infections, emphasizing on the genes encoding fibronectin (fnbA, fnbB) and collagen (cna) adhesins. 191 S. aureus strains from orthopedic
infections (53 from internal fixation devices, 29 external fixation devices, 15 knee arthroprostheses, 30 hip arthroprostheses, 45 surgical reconstruction and 19 non-associated to medical devices) were investigated for the presence of the genes of the collagen-binding protein Cna and of the two fibronectin-binding
proteins, FnbA and FnbB. 87 (46%) strains were found to be cna+ without significant variations across the different surgical categories considered. Conversely, the fnbA and the fnbB genes were almost always present in all surgical categories. The finding that, among the investigated adhesins, fibronectin-adhesins are present in the majority of the implant associated S. aureus clinical isolates encourages the development of strategies to specifically block the interaction of bacteria with matrix fibronectin by antagonist ligands
Presence of fibrinogen-binding adhesin gene in Staphylococcus epidermidis isolates from central venous catheters-associated and orthopaedic implant-associated infections.
No full textBiomaterials. 2004 Aug;25(19):4825-9.
Presence of fibrinogen-binding adhesin gene in Staphylococcus epidermidis isolates from central venous catheters-associated and orthopaedic implant-associated infections.
Arciola CR, Campoccia D, Gamberini S, Donati ME, Montanaro L.
Research Laboratory on Biocompatibility of Implant Materials, Rizzoli Orthopedic Institute, Via di Barbiano, 1/10, Bologna 40136, Italy.
Attention has recently been paid to identify and elucidate those pathogenetic mechanisms, which play a significant role in sustaining the early phases of Staphylococcus epidermidis colonisation and infection development. Several analogies with the physiology of Staphylococcus aureus, a more thoroughly investigated pathogen, have lead to carefully consider all bacterial surface components that mediate cell adhesion. This study aimed at investigating the presence of the fbe gene encoding for a fibrinogen-binding protein in a collection of 107 S. epidermidis strains isolated from orthopaedic infections and 67 from central venous catheter-associated infections. The strains isolated
from orthopaedic infections were in large part associated to four different classes of orthopaedic devices, respectively: internal fixation devices, external fixation devices, knee arthroprostheses and hip arthroprostheses. The molecular epidemiology analysis performed by PCR enlightened a statistically significant difference in the prevalence of this adhesion mechanism between orthopaedic infections and catheter-related infections, respectively, of 78% and 91%. The prevalence of fbe ranged from 67% to 91%, suggesting that, even though this adhesin is not strictly necessary for the development of infection, nevertheless it represents a rather common characteristic of strains causing
clinical infections, this independently on the presence or the absence of implant materials
Search for the insertion element IS256 within the ica locus of Staphylococcus epidermidis clinical isolates collected from biomaterial-associated infections.
No full textBiomaterials. 2004 Aug;25(18):4117-25.
Search for the insertion element IS256 within the ica locus of Staphylococcus epidermidis clinical isolates collected from biomaterial-associated infections.
Arciola CR, Campoccia D, Gamberini S, Rizzi S, Donati ME, Baldassarri L, Montanaro L.
Research Laboratory on Biocompatibility of Implant Materials, Rizzoli
Orthopaedic Institute, and Experimental Pathology Department, University of Bologna, Italy. [email protected]
Staphylococcus epidermidis biofilm-forming strains produce a polysaccharide intercellular adhesin (PIA), which mediates bacterial cell aggregation and favours the colonisation on prosthetic implants. PIA synthesis is regulated by the icaADBC locus. In vitro, by repeated subcultures of a biofilm-producing strain, the loss of the ability to produce biofilm appears associated with the
insertion of the IS256 element into the ica locus. This study was aimed (i) to investigate if the five genes of ica locus are always all present in different strains of S. epidermidis, and (ii) to search if IS256 insertion naturally occurs in ica locus without making recourse to the experimental procedure of repeated subcultures of strains. 120 S. epidermidis clinical isolates from peri-prosthesis infections were investigated both by an original multiplex PCR
analysis of the ica genes and by PCR amplification of the IS256 element. Also two reference strains (the biofilm-negative S. epidermidis ATCC 12228 and the biofilm-forming ATCC 35984 [RP62A]) and two biofilm-negative RP62A-derived acriflavin mutants (D9 and HAM892) were analysed. D9 e HAM892 were for the first time shown to contain in ica locus, at the base 3319, a 1300-bp insertion with a DNA sequence corresponding to IS256. Among the 120 clinical isolates, 51 (43%) turned out completely ica-positive, 69 completely ica-negative (57%). The genes of the ica locus appear, in all cases of the present collection, strictly linked
each other, so they are either all present or all absent. In this collection, IS256 was present in eight out of the 69 ica-negative strains and in 34 out of the 51 ica-positive strains. IS256, also when present in bacterial genomic DNA, was never found inside the ica locus, thus suggesting that insertion/excision of this element is not a natural occurring mechanism for off/on switching of
biofilm production
Antibiotic resistance in exopolysaccharide-forming Staphylococcus epidermidis clinical isolates from orthopaedic implant infections
No full textBiomaterials. 2005 Nov;26(33):6530-5.
Antibiotic resistance in exopolysaccharide-forming Staphylococcus epidermidis clinical isolates from orthopaedic implant infections.
Arciola CR, Campoccia D, Gamberini S, Donati ME, Pirini V, Visai L, Speziale P, Montanaro L.
Research Unit on Implant Infections, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy. [email protected]
The opportunistic pathogen Staphylococcus epidermidis is able to produce biofilm and to frequently cause implant infections. In recent years, it has also exhibited an increasing antimicrobial drug resistance. Here, the resistance to a panel of 16 different antibiotics in 342 clinical strains of S. epidermidis from orthopaedic implant infections has been investigated. The isolates were pheno- and genotyped for extracellular polysaccharide production, relevant to staphylococcal biofilm formation, in order to ascertain possible associations with antibiotic resistance. Approximately 10% of the isolates were found to be sensitive to all screened antibiotics. In all, 37-38% were resistant to beta-lactams such as oxacillin and imipenem, while the resistance to penicillin, ampicillin, cefazolin, cefamandole, was consistently observed in over 80% of the
strains. Erythromycin- and clindamycin- resistant strains were approximately 41% and 16%, respectively. Of the isolates, 10% was resistant to chloramphenicol, 23% to sulfamethoxazole and 26% to ciprofloxacin. Resistance to vancomycin was never observed. Interestingly, exopolysaccharide-producing strains exhibited a significantly higher prevalence in the resistance to the four aminoglycosides (gentamicin, amikacin, netilmicin, tobramycin), to sulfamethoxazole and to ciprofloxacin with respect to non-producing isolates. Moreover, multiple resistance to antibiotics was more frequent among exopolysaccharide-forming strains
A multiplex PCR method for the detection of all five individual genes of ica locus in Staphylococcus epidermidis. A survey on 400 clinical isolates from prosthesis-associated infections
No full textJ Biomed Mater Res A.
A multiplex PCR method for the detection of all five individual genes of ica locus in Staphylococcus epidermidis. A survey on 400 clinical isolates from prosthesis-associated infections.
Arciola CR, Gamberini S, Campoccia D, Visai L, Speziale P, Baldassarri L, Montanaro L.
Research Unit on Implant Infections, Rizzoli Orthopedic Institute, Via di Barbiano, 1/10, 40136 Bologna, Italy.
[email protected]
In Staphylococcus epidermidis, ica locus encodes for the synthesis of a polysaccharide intercellular adhesin (slime or biofilm). A multiplex polymerase chain reaction (PCR) for the detection of the five individual genes of ica locus was developed, with the aim to probe the set of genes in a large collection of Staphylococcus epidermidis clinical isolates. Single representative fragments
for icaR, icaA, icaD, icaB, and icaC genes were selected. Multiplex PCR was applied to two reference Staphylococcus epidermidis strains [the non-biofilm-forming ATCC 12228 and the biofilm-forming ATCC 35984 (RP62A)] and to 400 clinical isolates of Staphylococcus epidermidis from orthopedic prosthesis associated infections. The gene profile was compared with the phenotypic biofilm-forming ability, evaluated by means of an optimized Congo red agar (CRA) plate test. Among the clinical isolates, 228 (57%) turned out completely ica positive and were biofilm producing. Among the 172 non-biofilm-forming strains (43%), 164 (41%) were completely ica negative and 8 strains (2%) harbored all five ica genes. The ica locus thus proves to be a cluster of strictly linked genes, without any evidence of single gene deletion.
(c) 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Evaluation of bacterial adhesion of Streptococcus mutans on dental restorative materials.
No full textBiomaterials. 2004 Aug;25(18):4457-63.
Evaluation of bacterial adhesion of Streptococcus mutans on dental restorative materials.
Montanaro L, Campoccia D, Rizzi S, Donati ME, Breschi L, Prati C, Arciola CR.
Research Laboratory on Biocompatibility of Implant Materials, Rizzoli
Orthopaedic Institute, and Experimental Pathology Department, University of Bologna, Italy. [email protected]
Bacterial adhesion to the surface of composite resins and other dental restorative materials is an important parameter in the aetiology of secondary caries formation. The aim of the present study was to investigate the adhesion of a Streptococcus mutans strain (ATCC 25175) on the surface of different restorative materials. The test materials examined included three flowable
composites (Filtek Flow, Tetric Flow, and Arabesk Flow), three microhybrid composites (Clearfil APX, Solitaire 2, and Z250), two glass-ionomers (Fuji IX, Fuji IX fast), a compomer (F2000), an ormocer (Admira), and a control reference material (tissue culture grade, surface treated polystyrene). The adhesion tests
were carried out in 24-well plates. Quantitative turbidimetric measurements were finally performed in order to indirectly evaluate the amount of bacteria retained on the material surface after in vitro exposure to the bacteria suspension. Under these conditions, with the exception of the Admira ormocer and the Fuji IX fast glass ionomer, which were found to be more adhesive, all the other material surfaces showed a similar susceptibility to bacterial adhesion, exhibiting values not significantly different than the reference polystyrene control. Furthermore, the release of fluoride from some of the test surfaces did not appear capable to reduce early bacterial adhesion
Polysaccharide intercellular adhesin in biofilm: structural and regulatory aspects
No full textAbstract
Staphylococcus aureus and Staphylococcus epidermidis are the leading etiologic agents of implant-related infections. Biofilm formation is the main pathogenetic mechanism leading to the chronicity and irreducibility of infections. The extracellular polymeric substances of staphylococcal biofilms are the polysaccharide intercellular adhesin (PIA), extracellular-DNA, proteins, and amyloid fibrils. PIA is a poly-beta(1-6)-N-acetylglucosamine (PNAG), partially deacetylated, positively charged, whose synthesis is mediated by the icaADBC locus. DNA sequences homologous to ica locus are present in many coagulase-negative staphylococcal species, among which S. lugdunensis, however, produces a biofilm prevalently consisting of proteins. The product of icaA is an N-acetylglucosaminyltransferase that synthetizes PIA oligomers from UDP-N-acetylglucosamine. The product of icaD gives optimal efficiency to IcaA. The product of icaC is involved in the externalization of the nascent polysaccharide. The product of icaB is an N-deacetylase responsible for the partial deacetylation of PIA. The expression of ica locus is affected by environmental conditions. In S. aureus and S. epidermidis ica-independent alternative mechanisms of biofilm production have been described. S. epidermidis and S. aureus undergo to a phase variation for the biofilm production that has been ascribed, in turn, to the transposition of an insertion sequence in the icaC gene or to the expansion/contraction of a tandem repeat naturally harbored within icaC. A role is played by the quorum sensing system, which negatively regulates biofilm formation, favoring the dispersal phase that disseminates bacteria to new infection sites. Interfering with the QS system is a much debated strategy to combat biofilm-related infections. In the search of vaccines against staphylococcal infections deacetylated PNAG retained on the surface of S. aureus favors opsonophagocytosis and is a potential candidate for immune-protection
Emerging Issues and Initial Insights into Bacterial Biofilms: From Orthopedic Infection to Metabolomics
No full textBacterial biofilms, enigmatic communities of microorganisms enclosed in an extracellular matrix, still represent an open challenge in many clinical contexts, including orthopedics, where biofilm-associated bone and joint infections remain the main cause of implant failure. This study explores the scenario of biofilm infections, with a focus on those related to orthopedic implants, highlighting recently emerged substantial aspects of the pathogenesis and their potential repercussions on the clinic, as well as the progress and gaps that still exist in the diagnostics and management of these infections. The classic mechanisms through which biofilms form and the more recently proposed new ones are depicted. The ways in which bacteria hide, become impenetrable to antibiotics, and evade the immune defenses, creating reservoirs of bacteria difficult to detect and reach, are delineated, such as bacterial dormancy within biofilms, entry into host cells, and penetration into bone canaliculi. New findings on biofilm formation with host components are presented. The article also delves into the emerging and critical concept of immunometabolism, a key function of immune cells that biofilm interferes with. The growing potential of biofilm metabolomics in the diagnosis and therapy of biofilm infections is highlighted, referring to the latest research
Reliability Analysis of a Stand-Alone PV System for the Supply of a Remote Electric Load
No full textThe work presents a reliability analysis of a
stand-alone photovoltaic system for the supply of electric
loads located in remote areas not easily reachable by the low
voltage distribution network. The analysis is performed by
characterizing the electric load behavior by means of a
Montecarlo approach for taking into account the stochastic
variability of the electrical energy demand. A Montecarlo
approach is used also for evaluating the electricity
production of the stand alone photovoltaic system as a
function of the hourly solar irradiation of the installation
site. The variability both of the load and of the energy
production are correlated and the probability that the load
can remain unsupplied for a certain time can thus be
evaluated. Finally the reliability of the stand-alone system is
compared with the reliability of an eventual connection to
the grid as a function of the length of the connection line
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