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Roberta Creti

Publications and source records attributed to Roberta Creti.

11 recordsLinked to original sources
PubMed2006

Enterococcal colonization of the gastro-intestinal tract: role of biofilm and environmental oligosaccharides.

BACKGROUND: Biofilm formation in E. faecalis is presumed to play an important role in a number of enterococcal infections. We have previously identified a genetic locus provisionally named bop that is involved in maltose metabolism and biofilm formation. A transposon insertion into the second gene of the locus (bopB) resulted in loss of biofilm formation, while the non-polar deletion of this gene, together with parts of the flanking genes (bopA and bopC) resulted in increased biofilm formation. A polar effect of the transposon insertion on a transcriptional regulator (bopD) was responsible for the reduced biofilm formation of the transposon mutant. RESULTS: The amount of biofilm formed is related to the presence of maltose or glucose in the growth medium. While the wild-type strain was able to produce biofilm in medium containing either glucose or maltose, two mutants of this locus showed opposite effects. When grown in medium containing 1% glucose, the transposon mutant showed reduced biofilm formation (9%), while the deletion mutant produced more biofilm (110%) than the wild-type. When grown in medium containing 1% maltose, the transposon mutant was able to produce more biofilm than the wild-type strain (111%), while the deletion mutant did not produce biofilm (4%). Biofilm formation was not affected by the presence of several other sugar sources. In a gastrointestinal colonization model, the biofilm-negative mutant was delayed in colonization of the mouse intestinal tract. CONCLUSION: The biofilm-positive phenotype of the wild-type strain seems to be associated with colonization of enterococci in the gut and the presence of oligosaccharides in food may influence biofilm formation and therefore colonization of enterococci in the gastrointestinal system.

Animals↗
PubMed2006

Relationship between biofilm formation, the enterococcal surface protein (Esp) and gelatinase in clinical isolates of Enterococcus faecalis and Enterococcus faecium.

One-hundred and twenty-eight enterococcal isolates were examined for their ability to form biofilm in relation to the presence of the gene encoding the enterococcal surface protein (esp), production of gelatinase and to the source of isolation. Neither esp nor gelatinase seemed to be required for biofilm formation: both Enterococcus faecalis and Enterococcus faecium did not show a correlation between the presence of either esp or the production of gelatinase and biofilm formation. However, in E. faecium while esp was found in isolates from either source, the presence of both esp and biofilm together was only found in strains from clinical settings, suggesting that there exists a synergy between these factors which serves as an advantage for the process of infection.

Bacterial Proteins↗
PubMed2006

Therapeutic failures of antibiotics used to treat macrolide-susceptible Streptococcus pyogenes infections may be due to biofilm formation.

Streptococcus pyogenes infections often fail to respond to antibiotic therapy, leading to persistent throat carriage and recurrent infections. Such failures cannot always be explained by the occurrence of antibiotic resistance determinants, and it has been suggested that S. pyogenes may enter epithelial cells to escape antibiotic treatment. We investigated 289 S. pyogenes strains isolated from different clinical sources to evaluate their ability to form biofilm as an alternative method to escape antibiotic treatment and host defenses. Up to 90% of S. pyogenes isolates, from both invasive and noninvasive infections, were able to form biofilm. Specific emm types, such as emm6, appeared to be more likely to produce biofilm, although variations within strains belonging to the same type might suggest biofilm formation to be a trait of individual strains rather than a general attribute of a serotype. Interestingly, erythromycin-susceptible isolates formed a significantly thicker biofilm than resistant isolates (P < 0.05). Among resistant strains, those carrying the erm class determinants formed a less organized biofilm than the mef(A)-positive strains. Also, prtF1 appeared to be negatively associated with the ability to form biofilm (P < 0.01). Preliminary data on a selection of strains indicated that biofilm-forming isolates entered epithelial cells with significantly lower efficiency than biofilm-negative strains. We suggest that prtF1-negative macrolide-susceptible or mef(A)-carrying isolates, which are poorly equipped to enter cells, may use biofilm to escape antimicrobial treatments and survive within the host. In this view, biofilm formation by S. pyogenes could be responsible for unexplained treatment failures and recurrences due to susceptible microorganisms.

Adhesins, Bacterial↗
PubMed2006

Isolation of Corynebacterium tuscaniae sp. nov. from blood cultures of a patient with endocarditis.

A strain of an unknown coryneform bacterium was repeatedly isolated in pure culture from the blood of a patient affected by endocarditis. Comparative 16S rRNA gene sequence analysis revealed that this isolate represented a new subline within the genus Corynebacterium. This new taxon can be identified by the presence of corynomycolic acids and its enzymatic activities and fermentation of sugars. Acid production from glucose and maltose, pyrazinamidase and alkaline phoshatase activities, and hippurate hydrolysis were the most characteristic phenotypic features of the bacterium. On the basis of both phenotypic and phylogenetic evidence, it is proposed that this isolate be classified as a novel species, Corynebacterium tuscaniae sp. nov. The type strain, ISS-5309, has been deposited in the American Type Culture Collection (ATCC BAA-1141) and in the Culture Collection of the University of Göteborg (CCUG 51321).

Aged, 80 and over↗
PubMed2005

Glycosaminoglycans mediate invasion and survival of Enterococcus faecalis into macrophages.

Enterococcus faecalis is responsible for a large variety of nosocomial infections. The intestinal barrier is thought to be one of the preferential portals of entry of enterococci, and the ability of E. faecalis to survive within peritoneal macrophages may contribute to spreading to distant sites. We examined the ability of a polysaccharide-expressing (biofilm-positive) E. faecalis strain and an isogenic biofilm-negative mutant to enter and survive within professional and nonprofessional phagocytes. Biofilm-positive bacteria survived longer in all cell systems than did biofilm-negative bacteria, through a process of receptor-mediated endocytosis that is dependent on functional reorganization of microtubules and polymerization of microfilament and on activation of protein kinases but not ATPases or protein phosphatases. We suggest that glycosaminoglycans--specifically heparin, heparan sulfate, and chondroitin sulfate A--are the host receptors for enterococci on professional and, possibly, nonprofessional phagocytes, allowing entry of enterococci into cell compartments where killing mechanisms are inhibited.

Animals↗
PubMed2005

Association of group A streptococcal emm types with virulence traits and macrolide-resistance genes is independent of the source of isolation.

Streptococcus pyogenes (group A streptococci; GAS) recovered from paediatric pharyngitis (101 isolates) and asymptomatic children (79 isolates) in the same geographical area and period, as well as isolates collected during an enhanced national surveillance programme for GAS invasive diseases (79 isolates), were screened for the incidence of the streptococcal pyrogenic exotoxin (spe) genes speA and speC, as well as the macrolide-resistance genes erm(B), erm(A) subclass erm(TR) and mef(A), and typed by emm sequencing. The speA gene was detected with comparable incidence among throat isolates (13.9 % of asymptomatic children and 16.8 % of pharyngitis isolates) and in 25 % of invasive cases; in contrast, speC incidence was, surprisingly, higher in paediatric populations (55.4 % in pharyngitis isolates and 65.8 % in asymptomatic children) than in invasive isolates (30 %; P < 0.0001). Macrolide resistance was detected in 26.6, 38.0 and 37.6 % of strains belonging to invasive, asymptomatic and pharyngitis populations, respectively. The different incidences of exotoxin and antibiotic-resistance genes among populations did not appear to have an intrinsic clinical significance, but may reflect the propensity of these traits to be associated with certain emm types independent of the source from which the strains were isolated. Further investigations with larger emm-type populations are warranted to confirm this.

Anti-Bacterial Agents↗
PubMed2004

A putative sugar-binding transcriptional regulator in a novel gene locus in Enterococcus faecalis contributes to production of biofilm and prolonged bacteremia in mice.

A biofilm-negative transposon mutant was created from an Enterococcus faecalis strain that produces a lot of biofilm. The transposon had been inserted in the second gene of a locus consisting of 4 open-reading frames, designated bop (biofilm on plastic surfaces). A nonpolar deletion of this gene and of parts of the 2 flanking genes was created; production of biofilm by this deletion mutant was significantly enhanced, compared with that by the wild-type strain. Expression of a downstream gene was significantly lower in the transposon mutant than in the wild-type strain and the biofilm-enhanced deletion mutant. Transformation of this gene into the transposon mutant partially restored production of biofilm. Mice challenged by intravenous injection with the biofilm-negative mutant strain showed significantly reduced numbers of colony-forming units in the blood, compared with mice challenged with the biofilm-enhanced deletion mutant and the wild-type. These results indicate that bop is involved in production of biofilm and probably regulates expression of biofilm in the E. faecalis strain tested.

Animals↗
PubMed2004

Survey for virulence determinants among Enterococcus faecalis isolated from different sources.

A collection of Enterococcus faecalis strains from clinical isolates, healthy individuals and the environment was screened for the presence of virulence factor genes, such as those for collagen-binding protein (ace), endocarditis antigen (efaA), haemolysin activator (cylA), gelatinase (gelE), aggregation substances (asa1 and asa373), a surface protein (esp) and two novel putative surface antigens (EF0591 and EF3314). Apart from some genes that were present in all strains (ace, efaA and EF3314), the gelE gene was the most common factor, although its presence did not correlate with its expression. The genes that encode Esp and CylA were never detected in endocarditis isolates, whereas an association was noted between the esp gene and isolates from urinary tract infection (UTI) and bacteraemia. An aggregation substance gene was always present in commensal strains. As for gelatinase, the presence of the cylA and asa genes did not correlate completely with their phenotypic expression. Generally, isolates from endocarditis, biliary stents and the environment were equipped with fewer virulence factors than isolates from other sources. UTI strains possessed the highest number of factors.

Adhesins, Bacterial↗
PubMed2004

Receptor-mediated endocytosis of biofilm-forming Enterococcus faecalis by rat peritoneal macrophages.

BACKGROUND & OBJECTIVES: Enterococci are important nosocomial pathogens that are increasingly difficult to treat due to intrinsic and acquired resistance to antibiotics. Studies were taken up to identify virulence factors and to characterise pathogenic mechanisms of such infections to evaluate potential targets for treatments alternative to antibiotic therapy. This study was carried out to evaluate the contribution of extracellular polysaccharide expressed by Enterococcus faecalis to resistance to phagocytosis and survival within rat peritoneal macrophages. METHODS: Six E. faecalis clinical isolates were tested for their ability to survive within rat peritoneal macrophages. Cytochalasin D, colchicine and monodansylcadaverine were used to investigate the route of enterococcal entry inside macrophages. RESULTS: Four of the isolates were able to produce extracellular polysaccharide and form biofilm after growth in glucose-supplemented medium, while no production could be detected in glucose deficient medium. Two isolates were polysaccharide-negative in both conditions. Isolates expressing extracellular polysaccharide were able to survive for more than 24 h compared to polysaccharide-negative bacterial cells of the same strain grown in glucose-deficient medium, which were readily cleared. Cytochalasin D virtually abolished the number of viable intracellular bacteria, after growth in either trypticase soy broth (TSB) or TSB supplemented with glucose; colchicine and monodansylcadaverine strongly affected survival of polysaccharide-positive bacteria, significantly more than that of polysaccharide-negative ones. INTERPRETATION & CONCLUSION: Biofilm-forming E. faecalis survived within rat peritoneal macrophages significantly better than polysaccharide-negative isolates. Perturbators of cytoskeleton and of surface receptors turnover, indicated receptors-mediated endocytosis as the most likely route for enterococcal entry into macrophages.

Animals↗
PubMed2002

Recombinant GroES in combination with CpG oligodeoxynucleotides protects mice against Mycobacterium avium infection.

The groES gene of Mycobacterium avium strain 485 was cloned and expressed in Escherichia coli and the recombinant GroES protein was purified by affinity chromatography. The GroES preparation showed high purity by electrophoresis and immunoblotting. Immuno-electron microscopy showed that GroES was located both in the cytoplasm and on the surface of the mycobacterial cells and thus is readily available to interact with the host immune system. BALB/c mice were immunised intranasally with recombinant GroES, alone or in combination with a synthetic oligodeoxynucleotide containing unmethylated CpG motifs, and tested for protection against infection with M. avium. Neither GroES nor CpG alone provided any protection against subsequent challenge with M. avium, whereas a combination of the two significantly protected the lungs and spleen against colonisation by M. avium after intranasal challenge with a low dose of the organism. This indicates that intranasal administration of GroES and CpG oligodeoxynucleotides increases the resistance of BALB/c mice to M. avium infection.

Adjuvants, Immunologic↗