A retrospective pilot study of correlation of first maxillary premolar root trunk length with age and gender: a cone beam computed tomography study

BACKGROUND

Root trunk length (RTL) plays an important role in the diagnosis, prognosis and treatment of periodontitis. The aim of this retrospective pilot study was to evaluate the RTL of first maxillary premolar and to study the correlation with age and sex in this value.

METHODS

The sample included 110 cone beam computed tomography (CBCT) images comprising 220 maxillaries first premolars from systemically healthy patients aged between 18 and 70 years. The tooth length (TL), root length (RL) and RTL were measured (dependent variables). Age and sex were considered as independent variables.

RESULTS

No statistically significant correlation was found between the RTL and the TL. Longer RL and longer RTL were observed in younger patients than older subjects only in the left maxillary premolars. On the other hand, the sex of the patients had no effect on either of the dependent variables. The single rooted maxillary premolars were more frequent (relative to those with two roots) in woman and in elderly patients.

CONCLUSIONS

A correlation between the age and the RTL and RL has been found but only in left premolars. Sex seemed to have only a slight correlation on the frequency of single-rooted teeth of the right side of the mouth. Further studies should be addressed to clarify the significance of the asymmetries observed in the present study between the two sides of the mouth with the aim of deepening the knowledge and understanding of the different variables that could be correlated with the RTL.

Antibiotic Resistance in Staphylococcus Aureus and Staphylococcus Epidermidis Clinical Isolates from Implant Orthopedic Infections

In the last decade the rising phenomenon of resistance to most common antibiotic drugs among staphylococcal clinical isolates has been a reason for serious concern and alarm. The present study investigated the prevalence of antibiotic resistance within a large microbial collection including 530 clinical strains of S. aureus and 408 strains of S. epidermidis to a panel of 16 different drugs. All strains were isolated from orthopedic infections, either associated or non-associated with implant materials. Interestingly, our data show that the profile of the prevalence of antibiotic resistance within the two species of pathogens is extremely similar for the vast majority of the drugs screened. The only statistically significant variations in prevalence concerned, in order of relevance, the following 5 out of 16 antibiotics: sulfamethoxazole (in combination with trimethoprim), erythromycin, and, to a lesser extent, oxacillin, imipenem, and clindamycin. In the case of Staphylococcus aureus, the isolates associated to implant materials were found more frequently resistant to all 4 aminoglycosides screened as well as to ciprofloxacin.

Prevalence and Antibiotic Resistance of 15 Minor Staphylococcal Species Colonizing Orthopedic Implants

Several species belonging to Staphylococcus genus (nonSau/nonSep species) exhibit increasing abilities as opportunistic pathogens in colonisation of periprosthesis tissues. Here we report on antibiotic resistance of 193 strains, belonging to nonSau/nonSep species, consecutively collected from orthopedic implant infections in a period of about 40 months. The 193 strains (representing 17% of all staphylococci isolated) were analysed for their antibiotic resistance to 16 different drugs. Five species turned out more prevalent, ranging from 1 to 5%: S. hominis (4.2%), S. haemolyticus (3.7%), S. capitis (2.7%), S. warneri (2.6%), and S. cohnii (1.6%). Among these, the prevalence of antibiotic resistance to penicillins was similar, ranging from 51% to 66%. Conversely, significant differences were observed for all the remaining antibiotics. For S. haemolyticus the resistances to oxacillin and imipenem, the four aminoglycosides and erythromycin were at least twice that of the other three species which were compared. S. warneri was on the contrary the species with the lowest occurrence of resistant strains. Ten species appeared only rarely at the infection sites: S. lugdunensis, S. caprae, S. equorum, S. intermedius, S. xylosus, S. simulans, S. saprophyticus, S. pasteuri, S. sciuri, and S. schleiferi. The behaviours of these species, often resistant to penicillins, were individually analysed. Differences in both the frequencies and the panels of antibiotic resistances observed among the nonSau/nonSep species: i) suggest that horizontal spreading of resistance factors, if acting, was not sufficient per se to level their bio-diversities; ii) highlight and confirm the worrisome appearance within the Staphylococcus genus of emerging “new pathogens”, not homogeneous for their virulence and antibiotic resistance prevalence, which deserve to be recognised and treated individually.

A Glance at the Role of Exotoxins in Opportunistic Bacterial Infections

The production and the mechanism of action of exotoxins from Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa are presented. The attack to the immune host's defenses is the main virulence factor of opportunistic bacteria in implant infections, favoring the invasion and colonization of compromised periprosthesis tissues.

Etiology of Implant Orthopedic Infections: A Survey on 1027 Clinical Isolates

In spite of the recent achievements derived from modern protocols of prophylaxis, orthopedic surgical infections still remain unacceptably frequent, especially in light of the often devastating outcomes of septic complications. The spectrum and the prevalence of the bacteria most frequently involved in orthopedic infections are here explored, with particular reference to those infections associated to implant biomaterials, which were grouped based on device typology. During a 30 months period (from September 2000 to April 2003), 1027 microbial strains were consecutively isolated from 699 patients undergoing revision surgery at the Rizzoli Orthopedic Institute. 775 (75.5%) of all these microorganisms were identified as belonging to the Staphylococcus genus, 82 (8%) to the Enterobacteriaceae family, 75 (7.3%) to the Pseudomonas genus, 54 (5.3%) to the Enterococcus genus and 20 (1.9%) to the Streptococcus genus. While confirming the importance of staphylococci as the most diffuse cause of infection, our data indicate an unexpectedly high prevalence of S. epidermidis on infected hip and knee arthroprostheses, respectively of 42% and 44%. The spectrum of bacteria infecting either internal or external fracture fixation devices appears to differ from that of hip and knee arthroprostheses and more closely resembles that of infections non-associated to medical devices, being characterized by a relatively higher prevalence of Staphylococcus aureus (over 40%) and Pseudomonas aeruginosa. Enterobacteriaceae and members of the Streptococcus and Corynebacterium genera are frequently associated with implants in which surgical incisions were made near the perineum, determining a completely altered spectrum.

Implant Infection and Infection Resistant Materials: A Mini Review

Implant infection is an aggressive, often irreducible post-surgical infection. It remains the primary cause of implant failure. Bacterial contamination during surgery and subsequent adhesion onto biomaterial surface of opportunistic microorganisms, such as staphylococcal species, exopolysaccharidic slimes or specific adhesins, initiates the implant infection.

Pathogenesis of periprosthestic infection is the focus of studies aimed at developing infection resistant materials.

Biofilm in Implant Infections: Its Production and Regulation

A significant proportion of medical implants become the focus of a device-related infection, difficult to eradicate because bacteria that cause these infections live in well-developed biofilms.

Biofilm is a microbial derived sessile community characterized by cells that are irreversibly attached to a substratum or interface to each other, embedded in a matrix of extracellular polymeric substances that they have produced.

Bacterial adherence and biofilm production proceed in two steps: first, an attachment to a surface and, second, a cell-to-cell adhesion, with pluristratification of bacteria onto the artificial surface. The first step requires the mediation of bacterial surface proteins, the cardinal of which is similar to S. aureus autolysin and is denominated AtlE.

In staphylococci the matrix of extracellular polymeric substances of biofilm is a polymer of β-1,6-linked N-acetylglucosamine (PIA), whose synthesis is mediated by the ica operon. Biofilm formation is partially controlled by quorum sensing, an interbacterial communication mechanism dependent on population density.

The principal implants that can be compromised by biofilm associated infections are: central venous catheters, heart valves, ventricular assist devices, coronary stents, neurosurgical ventricular shunts, implantable neurological stimulators, arthro-prostheses, fracture-fixation devices, inflatable penile implants, breast implants, cochlear implants, intra-ocular lenses, dental implants.

Biofilms play an important role in the spread of antibiotic resistance. Within the high dense bacterial population, efficient horizontal transfer of resistance and virulence genes takes place.

In the future, treatments that inhibit the transcription of biofilm controlling genes might be a successful strategy in inhibiting these infections.

Automated Ribotyping to Distinguish the Different nonSau/ nonSep Staphylococcal Emerging Pathogens in Orthopedic Implant Infections

Several species belonging to Staphylococcus genus, other than Staphylococcus aureus and Staphylococcus epidermidis (nonSau/ nonSep species), exhibit increasing abilities as opportunistic pathogens in the colonisation of periprosthetic tissues. Consequently, the availability of means for accurate identification is crucial to assess the pathogenic characteristics and to clarify clinical relevance of the individual species. Here, 146 clinical staphylococcal isolates belonging to nonSau/ nonSep species from prosthesis-associated orthopedic infections were analyzed by conventional enzymatic galleries and by automated ribotyping. Twelve different species were recognised: S. capitis, S. caprae, S. cohnii, S. equorum, S. haemolyticus, S. hominis, S. lugdunensis, S. pasteuri, S. sciuri, S. simulans, S. warneri, S. xylosus. Ribotype identifications were compared with the phenotypes obtained by the Api 20 Staph system and/or ID 32 Staph system. ID 32 Staph profiles were more consistent with ribotyping results than Api Staph profiles. Across the different staphylococcal species investigated, correct identifications with Api Staph were 45%, while with ID 32 Staph they were 59%. It has, however, to be mentioned that ID 32 Staph was mostly applied to discriminate unmatched ribotyping and Api Staph identifications, thus to a subpopulation of strains with “atypical” metabolic profile. Automated ribotyping provided a correct identification for 91% of the isolates. These results confirm automated ribotyping as a convenient rapid technique, still subject to improvements, which will accurately and rapidly recognise the newly emerging staphylococcal pathogens in implant-related orthopedic infections.

Bacterial Communications in Implant Infections: A Target for an Intelligence War

The status of population density is communicated among bacteria by specific secreted molecules, called pheromones or autoinducers, and the control mechanism is called “quorum-sensing”. Quorum-sensing systems regulate the expression of a panel of genes, allowing bacteria to adapt to modified environmental conditions at a high density of population.

The two known different quorum systems are described as the LuxR-LuxI system in gram-negative bacteria, which uses an N-acyl-homoserine lactone (AHL) as signal, and the agr system in gram-positive bacteria, which uses a peptide-tiolactone as signal and the RNAIII as effector molecules. Both in gram-negative and in gram-positive bacteria, quorum-sensing systems regulate the expression of adhesion mechanisms (biofilm and adhesins) and virulence factors (toxins and exoenzymes) depending on population cell density.

In gram-negative Pseudomonas aeruginosa, analogs of signaling molecules such as furanone analogs, are effective in attenuating bacterial virulence and controlling bacterial infections. In gram-positive Staphylococcus aureus, the quorum-sensing RNAIII-inhibiting peptide (RIP), tested in vitro and in animal infection models, has been proved to inhibit virulence and prevent infections. Attenuation of bacterial virulence by quorum-sensing inhibitors, rather than by bactericidal or bacteriostatic drugs, is a highly attractive concept because these antibacterial agents are less likely to induce the development of bacterial resistance.

The Alpha-Like Surface Proteins: An Example of an Expanding Family of Adhesins

The Alpha-like protein (Alp) family, repeat-containing surface proteins once thought to be important adhesion factors confined to pathogenic streptococci and enterococci, is broader than previously known. Analysis of the annotated microbial genomes has identified new potential members of the Alp family not only in other Gram- positive opportunistic pathogens but also in commensal microflora of the human gut and the skin. This finding has highlighted the importance of genome sequencing projects for unraveling in greater detail lateral gene transfer events involving virulence factors between pathogens and commensals. These should receive constant attention not only as part of infectious disease prevention programs, but also in the food and biotechnology industries. (Int J Artif Organs 2008; 31: 834–40)

Underestimated Collateral Effects of Antibiotic Therapy in Prosthesis-Associated Bacterial Infections

Antibiotic treatment of infections associated with the use of indwelling medical devices in ageing and/or severely ill patients represents a significant healthcare problem due to the difficulty of treating such infections and to the various collateral effects that may be observed following the often aggressive therapy We summarize some effects of antibiotics on the expression of virulence factors of the microorganisms which cause such infections. These effects, particularly those resulting in a stimulation of bacterial virulence, might be usefully included among the other well-known collateral effects of antibiotic therapy

Innovative Methods of Rapid Bacterial Quantification and Applicability in Diagnostics and in Implant Materials Assessment

In recent years, a variety of new technologies have been proposed that allow rapid qualitative and quantitative microbiological analyses. In this paper we discuss the urgent needs for reliable and rapid microbiological analytical techniques in different applicative fields involving the research, production and medical application of implant materials, and the potential benefits derived from the use of new methods for rapid bacterial quantification. Current compendial methods are easy to perform and have gained confidence over their long period of use, but the supplemental use of new technologies could represent real breakthroughs whenever sensitive and rapid responses are urgently required and not met by the tests currently in use. Overall, the new microbiological methods require critical evaluation depending on their specific type of application and they may still not be thought of as totally substitutive, but they certainly exhibit considerable potential for different areas of biomaterials, as well as for advanced therapy medicinal and tissue engineering treatments.

p53-dependent and p53-independent anticancer activity of a new indole derivative in human osteosarcoma cells

Osteosarcoma (OS) is the most common primary malignant tumor of bone, occurring most frequently in children and adolescents. The mechanism of formation and development of OS have been studied for a long time. Tumor suppressor pathway governed by p53 gene are known to be involved in the pathogenesis of osteosarcoma. Moreover, loss of wild-type p53 activity is thought to be a major predictor of failure to respond to chemotherapy in various human cancers. In previous studies, we described the activity of a new indole derivative, NSC743420, belonging to the tubulin inhibitors family, capable to induce apoptosis and arrest of the cell cycle in the G2/M phase of various cancer cell lines. However, this molecule has never been tested on OS cell line. Here we address the activity of NSC743420 by examine whether differences in the p53 status could influence its effects on cell proliferation and death of OS cells. In particular, we compared the effect of the tested molecule on p53-wild type and p53-silenced U2OS cells, and on SaOS2 cell line, which is null for p53. Our results demonstrated that NSC743420 reduces OS cell proliferation by p53-dependent and p53-independent mechanisms. In particular, the molecule induces proliferative arrest that culminate to apoptosis in SaOS2 p53-null cells, while it brings a cytostatic and differentiating effect in U2OS cells, characterized by the cell cycle arrest in G0/G1 phase and increased alkaline phosphatase activity.

Interleukin 6 downregulates p53 expression and activity by stimulating ribosome biogenesis: a new pathway connecting inflammation to cancer

Chronic inflammation is an established risk factor for the onset of cancer, and the inflammatory cytokine IL-6 has a role in tumorigenesis by enhancing proliferation and hindering apoptosis. As factors stimulating proliferation also downregulate p53 expression by enhancing ribosome biogenesis, we hypothesized that IL-6 may cause similar changes in inflamed tissues, thus activating a mechanism that favors neoplastic transformation. Here, we showed that IL-6 downregulated the expression and activity of p53 in transformed and untransformed human cell lines. This was the consequence of IL-6-dependent stimulation of c-MYC mRNA translation, which was responsible for the upregulation of rRNA transcription. The enhanced rRNA transcription stimulated the MDM2-mediated proteasomal degradation of p53, by reducing the availability of ribosome proteins for MDM2 binding. The p53 downregulation induced the acquisition of cellular phenotypic changes characteristic of epithelial–mesenchymal transition, such as a reduced level of E-cadherin expression, increased cell invasiveness and a decreased response to cytotoxic stresses. We found that these changes also occurred in colon epithelial cells of patients with ulcerative colitis, a very representative example of chronic inflammation at high risk for tumor development. Histochemical and immunohistochemical analysis of colon biopsy samples showed an upregulation of ribosome biogenesis, a reduced expression of p53, together with a focal reduction or absence of E-cadherin expression in chronic colitis in comparison with normal mucosa samples. These changes disappeared after treatment with anti-inflammatory drugs. Taken together, the present results highlight a new mechanism that may link chronic inflammation to cancer, based on p53 downregulation, which is activated by the enhancement of rRNA transcription upon IL-6 exposure.

Proportionally constant quantitative transmission of nucleolin and protein B23 in cycling cancer cells

Objective-To investigate whether and to what extent the two major AgNOR proteins, nucleolin and protein B23, are maintained after one cell division in proliferating cells.Design-Using three asynchronously growing human cancer cell lines, TG, SJNKP, and CHP 212 cells, nucleolin and protein B23 were first identified on SDS-polyacrylamide separated nucleolar proteins, transferred to nitrocellulose and silver stained for AgNOR proteins. Measurement of doubling time indicated a period very close to 24h for each of the cell lines. To quantify the percentage of nucleolin and protein B23 maintained in daughter cells after duplication, cells were labelled with [(35)S]-methionine and a 24h cold chase performed. Nucleolin and protein B23 labelling was evaluated by densitometric analysis on nitrocellulose autoradiograms.Results-The radioactivity relative to nucleolin and protein B23 bands maintained in the daughter cells was a constant fraction of that present before cell duplication. In the three cell lines the percentage of residual radioactivity measured in the nucleolin bands was 42.2, 40.6, and 41.2 and in protein B23 bands 48.0, 46.2, and 44.1.Conclusions-After one cell division the nucleolin and protein B23 quantity present in cells may be highly variable, depending on the amount of the two proteins present in the mother cell. This is important in relation to the correct utilisation of AgNOR protein quantity as an index for evaluating cell kinetics.

High prevalence of retinoblastoma protein loss in triple-negative breast cancers and its association with a good prognosis in patients treated with adjuvant chemotherapy

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive disease, nevertheless exhibiting a high response rate to chemotherapy. Since the retinoblastoma protein (pRb) loss confers a high sensitivity to chemotherapy regimens, we evaluated the prevalence of pRb loss in TNBCs and its relevance on the clinical outcome of patients treated with adjuvant chemotherapy.

PATIENTS AND METHODS

pRb status was prospectively evaluated by immunocytochemistry in 518 consecutive patients with complete receptor information. The predictive value of pRb status in TNBCs was determined according to the adjuvant therapeutic treatments.

RESULTS

Fifty-three tumors were identified as TNBCs. The prevalence of pRb loss was significantly higher in TNBCs than in the other cancer subtypes. All patients with TNBCs lacking pRb and treated with systemic chemotherapy (cyclophosphamide, methotrexate and 5-fluorouracil) were disease free at a medium follow-up time of 109 months, whereas the clinical outcome of those expressing pRb was significantly poorer (P = 0.008). Analysis of disease-free survival including the established anatomo-clinical prognostic parameters indicated pRb loss as the only significant predictive factor.

CONCLUSIONS

pRb loss is much more frequent in TNBCs than in the other breast cancer subtypes. Patients with TNBCs lacking pRb had a very favorable clinical outcome if treated with conventional adjuvant chemotherapy.

Nanostructured materials for inhibition of bacterial adhesion in orthopedic implants: a minireview

Orthopedic implants may fail owing to different reasons: poor osseointegration at the tissue-implant interface, generation of wear debris, stress and strain imbalance between implant and surrounding tissues, and infections. To ensure success in orthopedics, implant materials must not evoke an undesirable inflammatory response, they must be habitable by bone-forming cells (favoring adhesion of osteoblasts), hinder formation of soft connective tissue (hindering adhesion of fibroblasts), and be anti-infective (discouraging bacterial adhesion). Recent studies have suggested that nanophase materials have a better efficacy as bone implants in favoring osseointegration compared to conventional orthopedic implant materials. This minireview discusses studies on nanophase materials as bone implants, focusing on the effect of these materials in inhibiting bacterial adhesion for the prevention of implant infections.

The selection of appropriate bacterial strains in preclinical evaluation of infection-resistant biomaterials

Implant-related infections are broadly recognized as one of the most serious and devastating complications associated with the use of biomaterials in medical practice. The growing interest and need for the development of implant materials with reduced susceptibility to microbial colonization and biofilm formation has necessitated the development of a series of in vitro and in vivo models for evaluation and preclinical testing. Current technologies provide these investigations with an ample choice of qualitative and quantitative techniques for an accurate assessment of the bioactivity and anti-infective efficacy of any new compound or device. These tests are typically performed using a reference bacterial strain designated as the test or reference strain. Recent molecular epidemiological studies have identified the complex clonal nature of most prevalent etiological agents implicated in implant-associated infections. New information which is continually emerging on the identity and the characteristics of both sporadic and epidemic clones must be considered when selecting a reference. A new emerging requirement is that the strain should be representative of the clones causing clinically relevant infections; they should, therefore, belong to the most prevalent epidemic clones rather than to sporadic ones, which may occur in only 1 out of 200 infections or even fewer. The correct choice of reference strain for preclinical tests is of crucial importance for the clinical significance of the achieved results. In this paper we report our experience and recommendations regarding this issue.

Prevalence of genes encoding for staphylococcal leukocidal toxins among clinical isolates of Staphylococcus aureus from implant orthopedic infections

Staphylococcus aureus has emerged as a major cause of implant infections. It is known that it is able to produce several toxins that contribute to its armory of virulent weapons, but there are still no data on their prevalence among isolates recovered from biomaterial-centered infections. In this study, 200 Staphylococcus aureus isolates from infections related to different types of orthopedic implants (hip and knee arthroprostheses, internal and external fixation devices) were tested by polymerase chain reaction for the prevalence of genes encoding for leukotoxins. Although almost all isolates were positive for the ã-hemolysin gene (99%), none was positive for lukM. The leukotoxin genes lukE/lukD were found in 67% of isolates. The presence of lukE/lukD was significantly associated with that of Accessory Gene Regulatory locus agr II. The lukE/lukD-positive isolates were significantly more prevalent in the staphylococcal isolates from knee arthroprostheses than in the isolates from the other implant types. The genes encoding Panton-Valentine leukocidin components were detected in only one isolate that, curiously enough, was taken solely from a knee arthroprosthesis infection.

Different effects of ribosome biogenesis inhibition on cell proliferation in retinoblastoma protein- and p53-deficient and proficient human osteosarcoma cell lines

OBJECTIVES

To evaluate the effects of rRNA synthesis inhibition on cell cycle progression and cell population growth according to the RB and p53 status.

MATERIAL AND METHODS

RB- and p53-proficient U2OS cells and the RB- and p53-deficient SAOS-2 cells were used, rRNA transcription hindered by actinomycin D, and cell cycle analysed by flow cytometry.

RESULTS

One hour of actinomycin D treatment induced in U2OS cells a block at the cell cycle checkpoints G(1)-S and G(2)-M, which was removed only after rRNA synthesis was resumed. rRNA synthesis inhibition did not influence cell cycle progression in SAOS-2 cells. No effect on cell cycle progression after actinomycin D-induced rRNA inhibition was also found in U2OS cells silenced for RB and p53 expression. A mild perturbation of cell cycle progression was observed in U2OS cells silenced for the expression of either RB or p53 alone. We also treated U2OS and SAOS-2 cells with actinomycin D for 1 h/day for 5 days. This treatment lightly reduced growth rate of the U2OS cell population, whereas cell population growth of SAOS-2 cells was completely inhibited. A marked reduction of ribosome content occurred in SAOS-2 cells after the long-term actinomycin D treatment, whereas no modification was observed in U2OS cells.

CONCLUSIONS

These results demonstrate that inhibition of ribosome biogenesis does not hinder cell cycle progression in RB- and p53-deficient cells. A daily-repeated transitory inhibition of ribosome biogenesis leads to a progressive reduction of ribosome content with the consequent extinction of cancer cell population lacking RB and p53.

Controversial relationship between the expression of the RB pathway components and RB protein phosphorylation in human breast cancer

Recent data challenge the relevance of the RB pathway to cancer based on RB inactivation, at least in breast tumors. To obtain information on the actual role of the components of the RB pathway in tumor progression we decided to investigate whether their quantitative changes were associated with variations in the level of RB phosphorylation in human breast cancer. A series of 68 human primary breast carcinomas was studied. Five cases were excluded from the study due to their lack of RB expression. In the remaining 63 cases the expression of cyclin D1, cdk4, cyclin E, and INK4a mRNA was assessed by real-time RT-PCR. The level of RB phosphorylated protein (ppRB) and p27 expression was immunohistochemically analyzed by measuring the percentage of stained cells (labeling index, LI). Cell proliferation rate was measured by Ki67 LI evaluation. The ppRB LI ranged from 5.2 to 73.8 and, as expected, was strongly related to the Ki67 LI (r=0.80; p<0.001). The expression of cyclin D1 mRNA, expressed in arbitrary units (a. u.), ranged from 1.15 to 123.0 and was inversely related to the ppRB LI (p=0.021) and Ki67 LI (p<0.001). Neither the cdk4 (range from 0.07 to 1.13 a. u.) nor the cyclin E (range from 0.13 to 9.27 a. u.) mRNA expression was significantly associated with the ppRB LI (p=0.962 and p=0.103, respectively). Cyclin E was related to Ki67 LI (p=0.022). Both INK4a mRNA (range from 0.01 to 0.60 a. u.) and p27 (LI from 0.0 to 73.1) values were inversely related to the ppRB LI (p=0.022 and p=0.014, respectively). Cyclin D1, cdk4, and cyclin E mRNA expressions were not significantly related to one another. In human primary breast cancers, the expression levels of the factors known to facilitate the cell cycle progression by RB protein phosphorylation were not positively related to ppRB-LI. Pathological increases of cyclin D, cdk4, and cyclin E are very likely associated with other biological functions other than their well-established action on cell cycle progression.

The p53 codon 72 proline allele is endowed with enhanced cell-death inducing potential in cancer cells exposed to hypoxia

The preferential retention of the arginine allele at the p53 codon 72 locus is commonly observed in tumours from arginine/proline heterozygotes. Considering that cancer cells are harboured in a hypoxic environment in vivo, we here tested the hypothesis that the p53 codon 72 proline allele confers a survival disadvantage in presence of hypoxia. Here, we show that the transient transfection of the proline allele in p53 null cancer cells exposed to low oxygen tension or to the hypoxia-mimetic drug Desferoxamine induces a higher amount of cell death than the arginine allele. Accordingly, proline allele transiently transfected cell lines express lower levels of hypoxia pro-survival genes (HIF-1alpha, carbonic anhydrase IX, vascular endothelial growth factor, heme oxygenase-I, hepatocyte growth factor receptor, vascular endothelial growth factor receptor 2), compared to those transiently transfected with the arginine allele. Further, we report that the exposure of the arginine/proline heterozygote MCF-7 breast cancer cell line to cytotoxic concentration of Desferoxamine for several weeks, gives raise to hypoxia-resistant clones, carrying the arginine, but not the proline allele. These data indicate that the p53 codon 72 proline allele is less permissive for the growth of cancer cells in a hypoxic environment, and suggest that the preferential retention of the arginine allele in the tumour tissues of arginine/proline heterozygous patients may depend upon its lowered capacity to induce cell death in a hypoxic tumour environment.

Relationship between the RB1 mRNA level and the expression of phosphorylated RB protein in human breast cancers: their relevance in cell proliferation activity and patient clinical outcome

The aim of the present study was to ascertain the relationship between the level of RB1 mRNA and the expression of phosphorylated RB protein and the relevance of these two parameters in cancer cell proliferation and clinical outcome in human breast cancer. Sixty-eight primary human breast cancers were considered. The amount of RB1 mRNA was evaluated by quantitative RT-PCR analysis. The level of RB phosphorylation was immunohistochemical defined by measuring the phosphorylated (pp) RB labelling index (LI). Cell proliferation rate was measured by calculating the Ki67 LI. No relation was found between the RB1 mRNA level and the ppRB LI (p=0.565). Both RB1 mRNA value and ppRB LI were related (in an inverse and direct manner, respectively) to Ki67 LI. RB1 mRNA expression was more strictly associated with KI67 LI (p=0.001) than the ppRB LI (p=0.013). Regarding the patient clinical outcome, the separately considered RB parameters did not reach the prognostic significance. However, patients with low RB1 mRNA quantity and patients with high ppRB LI, taken together, had a significantly shorter disease free and overall survival than the group comprehending patients with high RB1 mRNA value and low ppRB LI, and this despite the low number of patients considered. Our results demonstrated that the ppRB LI was independent of the RB1 mRNA level; that both RB parameters are related to the cell proliferation rate and, if collectively considered, have a high informative value on breast tumour prognosis.

Prognostic relevance of a novel semiquantitative classification of Bcl2 immunohistochemical expression in human infiltrating ductal carcinomas of the breast

BACKGROUND

Bcl2 is an important prognostic parameter in human breast cancer. However, the evaluation of Bcl2 expression by immunohistochemistry is carried out using arbitrary scoring criteria. In the present study, we evaluated the clinical relevance of a novel, semiquantitative classification of the Bcl2 immunostaining based on both the distribution and the intensity of the staining reaction.

PATIENTS AND METHODS

The proposed classification was first validated in 69 breast cancer specimens by comparing the Bcl2 immunostaining with the Bcl2 messenger RNA (mRNA) levels evaluated by real-time RT-PCR. Since a highly significant association was found between protein and mRNA for Bcl2, the immunohistochemical scoring system was applied to 442 patients with infiltrating ductal carcinomas of the breast with long-term follow-up (median observation time 106 months).

RESULTS

In the entire series, the Bcl2 variable was an independent predictor of clinical outcome, and its prognostic independence was maintained when lymph node-negative and -positive patients were considered separately. In this regard, of particular interest was the observation of a subgroup of node-negative breast cancer patients with a negative Bcl2 immunostaining, who had a very high probability of relapse or death (respectively about five and seven times greater than patients with a positive Bcl2 immunostaining). Moreover, the Bcl2 variable retained prognostic significance also in subgroups of patients treated with either adjuvant endocrine therapy or chemotherapy.

CONCLUSIONS

Our results demonstrated that in breast cancer, Bcl2 protein expression parallels its mRNA level, and it has a highly significant and independent prognostic relevance.

Study of Staphylococcus aureus adhesion on a novel nanostructured surface by chemiluminometry

In recent years the progress in the field of nanotechnologies has offered new possibilities to control the superficial features of implant materials down to a nanoscale level. Several studies have therefore tried to explore the effects of nanostructured biomaterial surfaces on the behavior of eukaryotic cells. However, nanotopography could exert an influence also on the behavior of prokaryotic cells, with relevant implications concerning the susceptibility of implant surfaces to infection. Aim of this study was to examine the behavior of Staphylococcus aureus on polyethylene terephthalate (PET) surfaces either cylindrically nanostructured (PET-N) or flat ion-etched (PET-F), and on tissue culture-grade polystyrene (PS). Microbial adherence was assessed by chemiluminometry under 4 different conditions: (a) bacteria suspended in MEM medium, (b) bacteria in MEM supplemented with 10% fetal bovine serum (FBS), (c) test surfaces preconditioned in FBS, and (d) post-exposure of colonised surfaces to serum-supplemented MEM. Under all circumstances, PET-F and PET-N specimens showed identical bacterial adhesion properties. In the absence of serum, all 3 test materials showed a very high adhesivity to microbial cells and both PET surfaces exhibited greater adhesion than PS. On the contrary, the presence of 10% serum in solution significantly affected cell behavior: the number of microbial cells on all surfaces was drastically reduced, and the adhesion properties of PET surfaces with respect to PS were reversed, with PET being less adhesive. Overall, the specific cylindrical nanostructures created on PET did not significantly influence microbial behavior. Ongoing studies are verifying whether other nanotopographies with different geometry could have more substantial effects.

Virulence factors in enterococcal infections of orthopedic devices

Enterococci are opportunistic pathogens which today represent one of the leading causes of nosocomial infections. We have examined a collection of 52 Enterococcus faecalis isolated from orthopedic infections to determine if they were characterized by a specific pattern of virulence factors. The isolates were evaluated for biofilm formation, presence of genes coding the enterococcal surface protein (esp) and gelatinase (gelE), as well as for gelatinase production. While the rate of esp-positive isolates was comparable to that found among strains from other clinical sources, we found a significantly higher rate of strong biofilm formers and gelatinase producers. Particularly high was the rate of gelE-carrying strains expressing the gene. Data suggest that these two factors in particular may play an important role in enterococcal infections associated with biomaterials.

Antibacterial activity of zinc modified titanium oxide surface

Titanium-based implants are successfully used for various biomedical applications. However, in some cases, e.g. in dental implants, failures due to bacterial colonization are reported. Surface modification is a commonly proposed strategy to prevent infections. In this work, titanium oxide, naturally occurring on the surface of titanium, was modified by promoting the formation of a mixed titanium and zinc oxide, on the basis of the idea that zinc oxide on titanium surface may act as the zinc oxide used in pharmaceutical formulation for its lenitive and antibacterial effects. The present work shows that it is possible to form a mixed titanium and zinc oxide on titanium surfaces, as shown by Scanning Electron Microscopy and XPS analysis. To this end titanium was preactivated by UV on crystalline titanium oxide, both in the anatase form or in the co-presence of anatase and rutile. By performing antibacterial assays, we provide evidence of a significant reduction in the viability of five streptococcal oral strains on titanium oxide surfaces modified with zinc. In conclusion, this type of chemical modification of titanium oxide surfaces with zinc might be considered a new way to reduce the risk of bacterial colonization, increasing the lifetime of dental system applications.

Emerging Staphylococcus species as new pathogens in implant infections

The vast use of prosthetic materials in medicine over the last decades has been accompanied by the appearance of new opportunistic pathogens previously considered incapable of causing infections with significant morbidity and/or mortality. In this regard, the genus Staphylococcus enlisting numerous species usually characterized by a saprophytic habit covers a special role. Apart from Staphylococcus aureus and Staphylococcus epidermidis, well known for their large prevalence in implant-related infections, a number of further staphylococcal species are progressively being indicated for their pathogenic potential. The increasing attention on these opportunistic bacteria is due to an ever growing number of clinical reports, which is also deriving from a more accurate identification of these species with currently available techniques. This synopsis intends to offer an overview on recently emerging coagulase-negative staphylococci (CoNS) as well as coagulase-positive/-variable staphylococci exhibiting distinct traits of virulence, pathogenicity, and epidemiologic impact depending among others on the medical field, the type of prosthetic device and its anatomic location.

Dyskerin expression influences the level of ribosomal RNA pseudo-uridylation and telomerase RNA component in human breast cancer

Dyskerin is a nucleolar protein, altered in dyskeratosis congenita, which carries out two separate functions, both fundamental for proliferating cells. One function is the pseudo-uridylation of ribosomal RNA (rRNA) molecules, necessary for their processing, and the other is the stabilization of the telomerase RNA component, necessary for telomerase activity. A significant feature of dyskeratosis congenita is an increased susceptibility to cancer; so far, however, no data have been reported on dyskerin changes in human tumours. Therefore, in this study, the distribution of dyskerin in a large series of human tumours from the lung, breast, and colon, as well as from B-cell lymphomas, was analysed by immunohistochemistry. Dyskerin proved never to be lost or delocalized outside the nucleolus. A quantitative analysis of dyskerin mRNA expression was then performed in 70 breast carcinomas together with the evaluation of telomerase RNA component levels and rRNA pseudo-uridylation. Dyskerin mRNA levels were highly variable and directly associated with both telomerase RNA component levels and rRNA pseudo-uridylation. Dyskerin gene silencing in the MCF-7 human breast carcinoma cell line reduced telomerase activity and rRNA pseudo-uridylation. Significantly, patients with low dyskerin expression were characterized by a better clinical outcome than those with a high dyskerin level. These data indicate that dyskerin is not lost in human cancers and that the levels of its expression and function are associated with tumour progression.

Pathogenesis of implant infections by enterococci

Enterococci are commensals of human and animal intestinal tract that have emerged in the last decades as a major cause of nosocomial infections of bloodstream, urinary tract and in infected surgical sites. Enterococcus faecalis is responsible for ca. 80% of all enterococcal infections while Enterococcus faecium accounts for most of the others; among the most relevant risk factors for development of enterococcal infections is the presence of implanted devices. The pathogenesis of such infections is poorly understood, but several virulence factors have been proposed. Among them, the ability to form biofilm has recently been shown to be one of the most prominent features of this microorganism, allowing colonization of inert and biological surfaces, while protecting against antimicrobial substances, and mediating adhesion and invasion of host cells and survival within professional phagocytes. Biofilm formation has been shown to be particularly important in the development of prosthetic valve enterococcal endocarditis and stent occlusion. Enterococci are also able to express other surface factors that may support colonization of both inert and biological surfaces, and that may be involved in the invasion of, and survival within, the host cell.

No genotoxicity of a new nickel-free stainless steel

Stainless steel is a metallic alloy largely employed in orthopedics, maxillofacial surgery and orthodontic therapy. However, the presence in its composition of a high quantity of nickel, an agent known to trigger toxic, allergic and cancerogenous responses in humans, is cause of some concern. In this study, we have investigated the in vitro mutagenicity and genotoxicity of a new nickel-free stainless steel, namely P558, in comparison to the conventional stainless steel AISI 316L. The cytogenetic effects were evaluated by studying the frequency of Sister Chromatid Exchanges (SCE) and chromosomal aberrations. Ames test was performed to detect the mutagenic activity. Both P558 and AISI 316L did not cause any significant increase in the average number of SCE and in chromosomal aberrations, either with or without metabolic activation. Furthermore, the Ames test showed that the extracts of both P558 and of AISI 316L are not mutagenic. Overall, these findings prove that P558 is devoid of genotoxicity and mutagenicity. The present results, together with other previous interesting observations that P558 promotes osseointegration, suggest that this new nickel-free stainless steel can represent a better alternative to other conventional steel alloys.

Analysis of virulence factors in cases of enterococcal endocarditis

Eleven isolates of Enterococcus faecalis causing endocarditis were screened for possible virulence factors with PCR and phenotypic assays. The gene coding for the enterococcal surface protein (esp) was detected in one isolate only, and haemolysin was produced by two isolates. Aggregation substance, biofilm formation and gelatinase were present in seven, nine and eight isolates, respectively. Predisposing factors, particularly hospitalisation and multiple antibiotic therapy, appeared to be more relevant to the development of enterococcal endocarditis following bloodstream infections than the pattern of virulence factors.

Enhanced telomere shortening in transformed lymphoblasts from patients with X linked dyskeratosis

AIM

Dyskeratosis congenita (DC) is characterised by the failure of those tissues that are rapidly dividing in the adult, particularly the skin, mucosae, and haemopoietic system. The X linked form of the disease is caused by mutations of the DKC1 gene, which encodes dyskerin, a protein that is necessary for the function of telomerase. Cultured DC lymphoblastoid cells are characterised by a reduced expansion of the cell population because of the progressive increase in apoptosis compared with the number of cell divisions. This report aimed to verify whether this is caused by a defect in telomerase function.

METHODS

Variations in telomere length over time were evaluated in two cultured lymphoblastoid cell lines derived from patients with X linked DC and control cells derived from a non-affected individual. In addition, the effect of inhibiting poly (ADP-ribose) polymerase (PARP), which is involved in the cellular response to excessive telomere shortening, was assessed. One DC cell line and the control cells were treated with the specific PARP inhibitor 1,5-dihydroxyquinoline (IQ).

RESULTS

In DC cells the increase in cell death was associated with progressive telomere shortening, and this was not seen in the control cells. Treatment with IQ delayed the increase of apoptosis in DC cells.

CONCLUSIONS

These observations indicate that the reduced expansion that characterises cultured cells obtained from patients with X linked DC is caused by premature telomere shortening.

Thymidylate synthase protein expression and activity are related to the cell proliferation rate in human cancer cell lines

AIMS

To ascertain whether the expression and enzyme activity of thymidylate synthase (TS) are related to the rapidity of cell proliferation in human cancer cell lines.

METHODS

Ten asynchronously growing human cancer cell lines of different origin were used, characterised by various doubling times. TS expression was evaluated by western blot analysis using the TS 106 monoclonal antibody. TS activity was determined by the enzyme catalytic assay. The quantitative variation of TS in different phases of the cell cycle was investigated using two parameter flow cytometry for the TS protein and DNA analysis. The number of proliferating cells was evaluated by Ki67 immunostaining.

RESULTS

TS expression and activity were significantly related to each other (r = 0.765; p = 0.01) and to the cell doubling time (r = -0.899; p < 0.001 and r = -0.919; p < 0.001, respectively). Ki67 immunolabelling showed no association between the number of cycling cells and TS protein expression and activity. Two parameter flow cytometry indicated that differences of TS expression in the cell lines were not related to the cell cycle phases or to the proportion of S phase cells.

CONCLUSIONS

These results show that the expression and activity of the TS protein in asynchronously growing cancer cells are significantly related to the cell doubling time; the faster the cell proliferation, the greater the expression and activity of TS. These findings could explain why TS values are of prognostic value per se and why tumours with high TS expression benefit more from chemotherapy.

In vitro effects on MG63 osteoblast-like cells following contact with two roughness-differing fluorohydroxyapatite-coated titanium alloys

The chances of integration between an implant and the surrounding bone tissue depend on the surface characteristics of the implant itself. Particularly, chemical composition and surface roughness of the material have emerged as crucial factors in affecting the behaviour of cells in contact with the material. Among various surfaces, calcium phosphate coatings seem to favour a rapid initial integration, but their dissolution by extracellular fluids raises some concern about the long-term stability at the bone-implant interface. Fluorinated apatites are known to be more stable than other ceramic coatings, but, at present, little is known on their effects on human cells. In this study, MG63 osteoblast-like cells were seeded onto two fluorohydroxyapatite (FHA)-coated titanium alloy (Ti6Al4V) materials differing in roughness, respectively, LR-FHA (Ra = 5.6 microm) and HR-FHA (Ra = 21.2 microm). Quantification of the cells in contact with the FHA-coated materials by conventional methods involved some technical difficulties, on which we report. Only the indirect esteem by the measure of total content of proteins and a procedure based on cell count, following a double enzymatic treatment to detach the cells, offered plain results, indicating no significant differences between cellular growth in contact with test materials and with plastic control. Differentiation and functionality of the cells were comparatively evaluated by analysis of alkaline phosphatase activity and osteocalcin production. As far as osteocalcin release is concerned, only slight variations were detected on FHA-coated materials in comparison with the control. Both types of coatings showed a significant increase in alkaline phosphatase activity with respect to the control, the roughest surface exhibiting a more prolonged effect on the time.

Enterococcus spp. produces slime and survives in rat peritoneal macrophages

Enterococcal clinical isolates were investigated for the ability to form biofilm on inert surfaces, as a measure of slime production, in an attempt to find new possible virulence factors for these microorganisms. This property was commonly found among Enterococcus faecalis. Also E. faecium isolates were able to form biofilm, although to a lesser extent; for this species, however, biofilm formation seemed more frequently associated with isolates from infection rather than with environmental strains or isolates from healthy individuals. Biofilm formation was strongly affected by the presence of an additional carbohydrate source in the medium, or by iron deprivation, indicating a role of slime for survival in stressful conditions. Slime-producing E. faecalis were able to survive inside peritoneal macrophages for extended periods compared to slime-negative strains or to slime-positive bacteria grown in conditions depressing slime production. In particular, slime-producing and slime-negative cells showed a decrease of 1 and 2 log units, respectively, at 1 h after infection; slime-negative cells were then rapidly killed, with clearance of bacterial cells at 24 h. Slime-producing bacteria persisted up to 48 h, which was the last time point examined, as after that time viability of both infected and non-infected macrophages started to decline. Scanning electron microscopy observations showed the presence of abundant amorphous extracellular material, of possible polysaccharide nature, embedding bacterial cells to form a multilayered biofilm. Even in conditions not supporting biofilm formation, bacterial cells appeared capsulated, suggesting that capsule and slime might represent different structures. Genes belonging to the epa locus or to a putative icaA homolog did not seem to be involved in synthesis and export of slime.

Congo red agar plate method: improved accuracy and new extended application to Staphylococcus aureus

In the last decade an increasing number of research studies have focused on the role of slime formation in Staphylococcus epidermidis and, more recently, also in S. aureus. In this context, much attention is being paid to evaluating the prevalence of slime production among bacteria strains isolated from clinical infections in an attempt to assess the role and the diagnostic value of this well recognised virulence marker. Such types of investigations require reliable techniques to identify slime producing strains. For years, even though based on a subjective chromatic evaluation, the Congo red agar plate (CRA) represented a reference phenotypic test for S. epidermidis. Only with the new introduction of PCR-based techniques, able to specifically identify the genes necessary for slime production, did the accurate genetic classification of slime producing bacteria become possible. In the present investigation, a comparison with new PCR methods confirmed the validity of the classic CRA test, implemented with minor refinements. Thanks to a few modifications it was also possible to adapt and extend the CRA test, making it also suitable to screen S. aureus strains.

Staphylococci in orthopaedic surgical wounds

From 50 infected surgical wounds of orthopaedic patients, 43 (86%) staphylococcal strains were isolated. 34 of all these staphylococci belonged to Staphylococcus aureus species (i.e. 68 % of all isolates from surgical wounds; 79% of staphylococcal isolates); 9 were coagulase-negative staphylococci (i.e. 21% of all isolates from surgical wounds; 18% of staphylococcal isolates). Among microorganisms isolated from the wounds we also found 2 (4%) of the Enterobacteriaceae family; 2 (4%) of the Pseudomonas genus; 3 (6%) of the Streptococcus genus. Thus, orthopaedic surgical wounds were infected by staphylococci (mainly S. aureus) more frequently than by other micro-organisms. All the staphylococcal strains were screened for methicillin resistance by agar disk diffusion testing and for the presence of mecA gene responsible for methicillin resistance by PCR. 32% of the S. aureus and 33% of the S. epidermidis strains resulted methicillin resistant and mecA-positive. The data confirm the diffusion of methicillin resistant S. aureus in surgical site infections and shows that the so-called "new pathogens", i.e. S. epidermidis and other coagulase-negative staphylococci, also exhibit a frequent and hazardous methicillin-resisting ability.

Presence of icaA and icaD genes and slime production in a collection of staphylococcal strains from catheter-associated infections

Both Staphylococcus epidermidis and Staphylococcus aureus are important causes of infections associated with catheters and other medical devices. It has recently been shown that not only S. epidermidis but also S. aureus can produce slime and carries the ica operon responsible for slime production. In the operon, coexpression of icaA and icaD is required for full slime synthesis. In this study, the presence of icaA and icaD was determined in a collection of 91 staphylococcal (68 S. epidermidis and 23 S. aureus) strains from intravenous catheter-associated infections, in 10 strains from the skin and mucosa of healthy volunteers, and in two reference strains by a PCR method. Slime-forming ability was tested on Congo red agar plates; 49% of S. epidermidis strains from catheters and, surprisingly, 61% of S. aureus strains were icaA and icaD positive and slime forming. All the saprophytic strains turned out to be negative for both icaA and icaD and also non-slime forming. Two S. aureus and one S. epidermidis strain from catheters, detected as icaA and icaD positive by PCR analysis and as slime forming (black colonies) at 24 h on Congo red agar, at 48 h exhibited tiny red spikes at the center of black colonies. The onset of these variants could not be ascribed to a mutagenic potential of Congo red, which, in the Ames test, was devoid of mutagenicity. PCR analysis showed that these red variants were negative for both icaA and icaD and even lacking the entire icaADBC operon. The data reported indicate an important role of ica genes as a virulence marker in staphylococcal infections from intravenous catheters.

In vitro study of blood-contacting properties and effect on bacterial adhesion of a polymeric surface with immobilized heparin and sulphated hyaluronic acid

The blood-contacting properties and the effect on bacterial adhesion of a material based on polyurethane and poly(amido-amine) (PUPA), both in its native form and with the anticoagulant molecules heparin or sulphated hyaluronic acid (HyalS3.5) electrostatically bonded to its surface, were evaluated and compared in vitro. The presence of the biological molecules on the surface was revealed by a dye test and ATR/FTIR analysis. Bound heparin was found to maintain its physiological action, in terms of thrombin inactivation, as well as did free heparin. Moreover, it reduced the degree of platelet adhesion. On the contrary, bound HyalS3.5 lost its anticoagulant activity, though it reduced platelet adhesion. The number of platelets on both modified surfaces was low. Their shape distribution, as determined by SEM, did not differ significantly on the two modified surfaces or with respect to the bare PUPA surface. HyalS3.5 and heparin also inhibited adhesion of Staphylococcus epidermidis to the material. A possible relationship between the platelet and bacterial adhesion is ascribed to the mediating role of plasma proteins.

A rapid PCR method for the detection of slime-producing strains of Staphylococcus epidermidis and S. aureus in periprosthesis infections

In periprosthesis tissues, Staphylococcus epidermidis produces extracellular polysaccharide slime. Recently it has been shown that S. aureus also produces slime and that both S. epidermidis and S. aureus contain the ica operon responsible for slime production. In the operon, icaA encodes for N-acetylglutaminyltransferase, the enzyme for polysaccharide synthesis. However, co-expression of icaA and icaD is required for full slime synthesis. The slime-producing strains of both S. epidermidis and S. aureus are more virulent and are responsible for severe postsurgical or periprosthesis infections. The authors describe a simple, rapid, and reliable polymerase chain reaction method to detect icaA and icaD. The method was applied to the detection of ica genes on two reference strains, 15 strains each of S. epidermidis and S. aureus from periprosthesis infections and 10 strains from the skin and mucosa of healthy volunteers. icaA and icaD were detectable only in slime-producing strains (tested for slime production on Congo Red agar), and never in nonslime-producing ones. This method is a straightforward way of detecting the slime-producing ability by S. epidermidis and S. aureus. In clinical specimens this polymerase chain reaction method enables rapid diagnosis of virulent slime-producing strains with respect to the traditional culture method on Congo Red agar, which requires much more time. Rapid identification of the virulent properties of the bacterial strain responsible for a staphylococcal infection is crucial for deciding treatment.

Effect of iron limitation on slime production by Staphylococcus aureus

The aim of this study was to examine the effect of growth conditions on slime production by Staphylococcus aureus clinical isolates. The addition of glucose to the medium enhanced slime production in the majority of Staphylococcus aureus isolates cultured from infections associated with orthopaedic prostheses. Iron limitation also stimulated this ability even in the absence of the additional carbohydrate source. Staphylococcus aureus isolates were classified as Group 1 [strains producing slime only in trypticase soy broth supplemented with 1% glucose (TSBG) or in iron-limited trypticase soy broth (TSB/Fe-)]; Group 2 (slime + only in TSB/Fe-); or Group 3 (slime+ only in TSBG). Seven repeatedly slime-negative strains were stimulated to produce slime by subpassaging in iron-limited medium. Low iron levels, usually found in vivo, could stimulate slime production by Staphylococcus aureus and support chronic infections associated with orthopaedic prostheses.

Nucleotides U28-A42 and A37 in unmodified yeast tRNA(Trp) as negative identity elements for bovine tryptophanyl-tRNA synthetase

Wild-type bovine and yeast tRNA(Trp) are efficiently aminoacylated by tryptophanyl-tRNA synthetase both from beef and from yeast. Upon loss of modified bases in the synthetic transcripts, mammalian tRNA(Trp) retains the double recognition by the two synthetases, while yeast tRNA(Trp) loses its substrate properties for the bovine enzyme and is recognised only by the cognate synthetase. By testing chimeric bovine-yeast transcripts with tryptophanyl-tRNA synthetase purified from beef pancreas, the nucleotides responsible for the loss of charging of the synthetic yeast transcript have been localised in the anticodon arm. A complete loss of charging akin to that observed with the yeast transcript requires substitution in the bovine backbone of G37 in the anticodon loop with yeast A37 and of C28-G42 in the anticodon stem with yeast U28-A42. Since A37 does not prevent aminoacylation of the wild-type yeast tRNA(Trp) by the beef enzyme, a negative combination apparently emerges in the synthetic transcript after unmasking of U28 by loss of pseudourydilation.

Shiga toxin 1: damage to DNA in vitro

Shiga toxins share with plant ribosome-inactivating proteins the same enzymatic mechanism of action: the removal of a specific adenine from 28S RNA when acting on ribosomes and the removal of multiple adenines when acting on DNA in vitro. The activity on DNA, only recently reported, is particularly evident, and has been studied mostly at acidic pH. For the in vitro activity, on both ribosomes and DNA, Shiga toxins require activation by trypsin, urea and dithiothreitol which release the enzymatically active A(1) fragment. Activation by the classical procedure leaves large amounts of urea and DTT which interfere in the DNA depurination assay and completely abolish depurination at physiological pH. A consistent release of [3H]adenine from DNA at neutral pH is instead observed when the toxin is activated in vitro by an improved method which removes most of the drastic reagents required for proteolytic cleavage and reduction. Damage to single-stranded DNA by Shiga toxin 1 (Stx1) primarily involves depurination. A spontaneous DNA breakdown appears in fact only after extensive base removal, a behavior similar to that observed with uracil-DNA glycosylase, a simple glycosylase devoid of lyase activity. NaCl inhibits the activity of Stx1, probably by minimizing the sliding distance traveled by the enzyme along DNA in search of its target sites and promoting dissociation of the substrate-enzyme complex.

Cytotoxicity, blood compatibility and antimicrobial activity of two cyanoacrylate glues for surgical use

The biocompatibility of two cyanoacrylate surgical glues (Glubran and Glubran 2), supplied by General Enterprise Marketing, Viareggio, Lucca, Italy, was tested through cytotoxicity and blood compatibility tests and the evaluation of antimicrobial activity. Cytotoxicity and blood compatibility tests were performed on the polymerized glues. Using the neutral red uptake test, the extracts from Glubran and Glubran 2 after polymerization were non-toxic to L929 cells only when diluted 1: 10 with culture medium. Glubran and Glubran 2 induced a significant decrease of activated partial thromboplastin time (APTT), which is favourable with regard to the desired haemostasis. The APTT shortening determines a haemostatic effect and therefore contribute to the tissue adhesion induced by the glues. Otherwise, no significant variation of prothrombin activity, fibrinogen, platelet number, total and differential leukocyte count was induced by the glues, which, in addition, did not show haemolytic effect. There was no difference between Glubran and Glubran 2 regarding haemocompatibility. The antimicrobial ability of the unpolymerized glues was tested onto Bacillus subtilis var. niger for 3 weeks: neither Glubran nor Glubran 2 were found effective in this respect. In conclusion, we can assume that cytotoxicity was severe with the undiluted glues, but was acceptable when glues were diluted. On the contrary, blood compatibility was acceptable for the intended use of the glues. No difference was found between Glubran and Glubran 2 after polymerization.

Adhesion of a Staphylococcus aureus strain to biomaterials does not select methicillin-resistant mutants

Bacterial adhesion to polymethylmethacrylate and to silicon elastomer, materials frequently used in clinical applications, has been investigated to assess whether adhesion selects methicillin-resistant mutants in the bacterial population in contact with the materials. The methicillin susceptibility of a susceptible Staphylococcus aureus (ATCC 25923) was measured by a modification of plate antibiogram Kirby-Bauer method, which allows optimised detection of small variations in antibiotic susceptibility. In both adherent and non-adherent bacterial subpopulations, the presence of mecA gene, which encodes for the protein PBP 2a responsible for methicillin resistance was searched for by Polymerase Chain Reaction (PCR). The contact with the two polymers did not induce in the bacteria population any phenotypic increase in methicillin resistance, or the selection of mutants carrying the mecA gene.