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L Baldassarri

Publications and source records attributed to L Baldassarri.

At least 37 records · Page 2Linked to original sources
PubMed1999

Presence and expression of collagen adhesin gene (cna) and slime production in Staphylococcus aureus strains from orthopaedic prosthesis infections.

Prosthesis-associated infections still represent one of the most serious complications in the clinical use of biomaterials. The most frequent causes are Staphylococcus aureus and Staphylococcus epidermidis. Several studies have been devoted to identify adhesion mechanisms for these bacteria. Slime in particular has been extensively investigated. Recently, in Staphylococcus aureus species, considerable attention has been given to the host protein receptors that have been shown in in vitro assays to serve as substrates for bacterial adhesion. Collagen-rich tissues, as bone and cartilage, that are the preferential sites of staphylococcal infections, are also the tissues that harbour orthopaedic implants. These can be easily coated in vivo by collagen and thus become prone to adhesion of Staphylococci strains which carry the collagen adhesin gene (cna). In this study the frequency of cna was determined within a collection of 35 Staphylococcus aureus strains from orthopaedic prosthesis infections by a PCR method. Also the collagen-binding ability and slime forming capacity was evaluated. 29% of the strains were cna-positive and also able to bind collagen in vitro. 83% of the strains were slime forming. The results indicate that in the examined bacterial population slime-positive strains predominate over the cna-positive strains, with a striking association of the two adhesion mechanisms in cna-positive strains.

Adhesins, Bacterial↗
PubMed1999

Slime production and expression of the slime-associated antigen by staphylococcal clinical isolates.

The ability to produce slime and to express a slime-associated antigen was examined in a collection of staphylococcal clinical isolates. Slime-producing strains were found among coagulase-negative staphylococci in percentages comparable to those reported in other studies; surprisingly, a high percentage of Staphylococcus aureus strains also were able to produce this extracellular material. In the latter case, this ability was strongly dependent on the presence of an additional carbohydrate source in the growth medium. Expression of the slime-associated antigen appeared to be species specific and confined to the Staphylococcus epidermidis sensu stricto isolates; its strong association with the ability of these strains to produce thicker biofilms indicated slime-associated antigen as a possible virulence marker for S. epidermidis.

Antigens, Bacterial↗
PubMed1999

Detection of fibronectin-binding protein genes in staphylococcal strains from peri-prosthesis infections.

Several studies have been devoted to identify the adhesion mechanisms of Staphylococcus aureus and Staphylococcus epidermidis, which are the most frequent causes of prosthesis-associated infections. Recently, in particular for Staphylococcus aureus, considerable attention has been given to the host protein receptors as mediators for bacterial adherence. Fibronectin, in important matrix protein, seems to be a major ligand for bacterial adherence in the early stages of infection. To determine the importance of the fibronectin adhesin as virulence factor in Staphylococcus-induced prosthesis infection, a simple and reliable method using a polymerase chain reaction (PCR) was devised to identify fibronectin adhesin genes (fnbA and fnbB). Results obtained by this method were in accordance with those obtained by the in vitro phenotypic characterization of binding ability to fibronectin of Staphylococcus strains.

Adhesins, Bacterial↗
PubMed1999

Slime production by Staphylococci isolated from prosthesis-associated infections.

Clinical isolates of Staphylococcus epidermidis are frequently referred to produce a biofilm, known as slime, involved in adherence to medical devices and in resistance to host defences. A high frequency of slime producing Staphylococcus aureus strains was never reported, at least in the case of human isolates. In the present study the production of slime by clinical isolates of S. aureus and S. epidermidis from catheter associated infections and from post-surgical infections was studied by a sensitive method based on culturing the isolates on Congo red agar. The study demonstrates that in nosocomial surgical infections, considered separately from catheter-associated infections, S. aureus emerges as a more prevalent etiologic agent than S. epidermidis, with a proportion of slime producing strains markedly high.

Biofilms↗
PubMed1998

A polymerase chain reaction (PCR) method for the identification of collagen adhesin gene (CNA) in Staphylococcus-induced prosthesis infections.

Staphylococci are well-recognized pathogens of foreign body-associated infections. The pathogenesis of such infections involves an initial step of contact between the colonizing bacterium and the biomaterial, with subsequent colony formation. Several studies have been devoted to identify adhesion mechanisms for these bacteria. Slime in particular has been extensively investigated. Recently, considerable attention has been given to the host protein receptors that have been shown in in vitro assays to serve as substrates for bacterial adherence. To determine the importance of the collagen adhesin as virulence factor in Staphylococcus-induced prosthesis infection, a simple and reliable method using a polymerase chain reaction (PCR) was devised to identify collagen adhesin gene (cna). By using lysates of ten strains from orthopedic prostheses (5 Staphylococcus aureus and 5 Staphylococcus epidermidis) and two 20-oligonucleotides as primers, a 192-bp region of the cna gene was amplified by PCR and detected by agarose gel electrophoresis. Results obtained by this method were in accordance with those obtained by the in vitro phenotypic characterization of binding ability to collagen of Staphylococcus strains.

Adhesins, Bacterial↗
PubMed1997

Expression of slime interferes with in vitro detection of host protein receptors of Staphylococcus epidermidis.

We hypothesized that slime may mask bacterial molecules important in the attachment of Staphylococcus epidermidis to inanimate surfaces. In support of this hypothesis, we found that slime-negative strains attached significantly better to fibrinogen or fibronectin than the parent strains and exhibited greater surface hydrophobicity. Comparable results were obtained with 53 clinical isolates.

Antigens, Bacterial↗
PubMed1996

Purification and characterization of the staphylococcal slime-associated antigen and its occurrence among Staphylococcus epidermis clinical isolates.

The Staphylococcus epidermidis slime-associated antigen (SAA) was purified and characterized. N-Acetyl-glucosamine accounted for 70% of the dry weight of SAA, which was immunolocalized on the ruthenium red-positive material produced by slime-positive strains. A total of 59% of slime-producing S. epidermidis clinical isolates expressed SAA, while the phenotype slime- SAA+ was never recovered.

Acetylglucosamine↗
PubMed1994

Detection of enteroadherent Escherichia coli associated with diarrhoea in Italy.

One hundred and sixty-eight isolates of Escherichia coli obtained in Italy from 112 children with diarrhoea and 56 age-matched controls were examined by the HEp-2 cell adhesion assay. Sixteen strains showed localised adherence (LA), 29 showed diffuse adherence (DA) and eight strains showed aggregative adherence (AA). No adhesion pattern was significantly associated with disease. Strains that showed LA or AA were further characterised by serotyping, fluorescent actin staining (FAS) test and hybridisation with the EPEC adherence factor (EAF), E. coli attaching and effacing (eae) and enteroaggregative (EAgg) DNA probes. Strains that showed poor LA were FAS-negative, did not belong to EPEC serotypes and did not hybridise with EPEC probes. Conversely, the two strains that showed a good LA pattern belonged to serotype O128:H2, were FAS positive and hybridised with the eae probe. No isolate hybridised with the EAF probe. Only three of the eight strains with the AA pattern hybridised with the EAgg probe. Probe positivity correlated with the ability to produce clumps at the surface of the liquid culture and to agglutinate rat erythrocytes. In two of these EAgg probe-positive strains, electronmicroscopy revealed the presence of fibrillar bundles which seem to mediate bacterial aggregation.

Bacterial Adhesion↗
PubMed1994

[Infections associated with intra- and extravascular catheters: factors involved in microorganism-biomaterial interactions].

Infections is one of the most common cause of catheter failure as well as the most difficult to manage, most often requiring catheter removal. Staphylococcus is the etiologic agent of such infections more frequently isolated, particularly Staphylococcus epidermidis. Several factors have been suggested to be involved in bacteria-biomaterial interactions such as catheter surface morphology, molecular biofilm and bacterial virulence features. Different strategies have been tried to avoid the development to catheter-associated infections: among them adsorption of antibiotic molecules to the catheter surface might represent a successful tool to improve catheter implant life.

Bacterial Adhesion↗
PubMed1993

Variable fixation of staphylococcal slime by different histochemical fixatives.

A variety of histochemical fixatives were used to compare the fixation of bacterial films produced by a standard slime-producing strain of Staphylococcus epidermidis on plastic tissue culture plates. Some reagents were completely ineffective in fixing the slime layer, whereas others gave variable results. The best alternative to the fixative of the reference method, the potentially explosive Bouin's reagent, was air drying.

Bacteriological Techniques↗
PubMed1993

In vitro adherence of Neisseria gonorrhoeae to human epithelial cells.

Gonococcal adherence was studied in vitro using buccal epithelial cells (BEC). In smears stained with the Gram method, a progressive decrease in gonococcal adherence to the BEC after some culture passages was observed. There was a parallel decrease to almost total disappearance in the number of fimbriated bacteria. An electron microscopy study showed that adherence to the epithelial cells was mediated by fimbriae and, in part, by a polysaccharide component of the bacterial cell wall which seems to guarantee persistent adherence ability, even after the loss of fimbriae.

Bacterial Adhesion↗
PubMed1991

HT-29 cells: a new substrate for rotavirus growth.

Susceptibilities of a continuous rhesus monkey kidney cell line (MA-104) and that of a human colon carcinoma cell line (HT-29) to infection by different human and animal rotavirus strains were compared. HT-29 cells appeared to be more sensitive to human rotavirus infection than MA-104 cells, whereas the latter cell line was more susceptible to animal rotavirus replication. The greater sensitivity to human rotavirus infection of HT-29 cells was confirmed by the successful, direct isolation of these viruses from faecal specimens. Human rotavirus infection of HT-29 cells was also followed by transmission electron microscopy. In ultra-thin sections, unenveloped particles of rotaviruses, representing infectious mature virions, were observed in large number. Moreover, many "double-shelled" particles were detected in negative-stained supernatants from infected cultures. Scanning electron microscopy of uninfected HT-29 cells showed that in the presence of Ca++, required for rotavirus growth, they are able to express some of the features of mature intestinal cells. In view of these results, HT-29 cells appear to be a useful in vitro model for the study of rotavirus infection.

Animals↗
PubMed1991

Capsule-like structures in Clostridium difficile strains.

Fourteen strains of Clostridium difficile, previously characterized by SDS-PAGE, were examined for the presence of surface structures. None of the strains were fimbriated but, when grown in the presence of glucose, all exhibited a thin ruthenium red-positive layer. Two strains, belonging to different electrophoretic groups, were also observed after treatment with homologous and heterologous antisera. The strain belonging to the electrophoretic group 2, usually associated with the disease, showed a 30-80nm thick capsule in ultrathin sections. The strains belonging to group 5, mainly observed in isolates from healthy children, exhibited a thinner polysaccharide layer (10-20 nm). No stabilization was observed when these strains were treated with heterologous antisera. This capsule-like material did not seem to be associated with adhesive properties of C. difficile strains.

Cell Wall↗
PubMed1989

Haemagglutination and surface structures in strains of Clostridium spiroforme.

Five strains of Clostridium spiroforme were examined for their surface properties. All strains were able to agglutinate human erythrocytes. Electron microscopy showed a ruthenium red-positive capsule mediating the attachment of bacteria to erythrocytes. Two strains, showing the lowest degree of haemagglutination, exhibited an additional external layer of filamentous structures, possibly interfering with the agglutinating activity. In spite of their agglutinating ability, the C. spiroforme strains did not show surface hydrophobicity, thus suggesting the possible existence of a new type of clostridial adhesin.

Animals↗
PubMed1989

Cryptosporidium as a common cause of childhood diarrhoea in Italy.

Cryptosporidium oocysts were observed in the stools of 9 (7.2%) of 124 Italian children with diarrhoea, examined during the period 1 January-31 December 1984. In two children, the parasite was associated with other enteric pathogens. The duration of diarrhoea was 2-30 days, with a median of 6 days. In all cases the infection was self limiting. The mean age of the Cryptosporidium-positive children was 34 months, and all cases occurred in the warm season. Cryptosporidium was found to be the third most common enteric pathogen after rotavirus and Salmonella spp.

Animals↗
PubMed1989

An unusual strain of Legionella micdadei.

A microorganism antigenically identified as Legionella micdadei but showing a cellular fatty acid profile distinct from that described previously for this species and more similar to that of L. bozemanii has been studied by phenotypic characterization, crossed immunoelectrophoresis, gas-liquid chromatography, and transmission electron microscopy. Although the phenotypic characters, the crossed immunoelectrophoresis, and the ultrastructural features were similar to those of L. micdadei, the fatty acid composition differed significantly from this species; moreover it differed also from L. bozemanii, even though it was quantitatively more similar.

Antigens, Bacterial↗