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Biomedical subjects

G Orefici

Publications and source records attributed to G Orefici.

At least 37 records · Page 2Linked to original sources
PubMed2000

Severity of group B streptococcal arthritis is correlated with beta-hemolysin expression.

Septic arthritis is a clinical manifestation of group B streptococcal (GBS) infection in neonates and adults. To examine the potential role of GBS beta-hemolysin in joint injury, mice were infected with 2 wild-type strains or with nonhemolytic (NH) or hyperhemolytic (HH) variants derived by transposon mutagenesis. Compared with mice infected with the parent strains, mice infected with the NH mutants had decreased mortality and bacterial proliferation. A reduced LD(50) and a higher microbial load were obtained in mice infected with the HH mutants. Greater degrees of joint inflammation and damage were observed in the HH mutant-infected animals than in those infected with the parental strains. NH mutant-infected mice manifested only a mild and transient arthritis. Systemic and local levels of interleukin-6 mirrored the observed differences in virulence and severity of arthritis. These data support a direct correlation of GBS beta-hemolysin expression with mortality and severity of articular lesions.

Animals↗
PubMed2000

Influence of interferon-gamma administration on the severity of experimental group B streptococcal arthritis.

OBJECTIVE: To assess the effect of interferon-gamma (IFNgamma) administration on the evolution of systemic infection and septic arthritis induced by group B streptococci (GBS) in mice. METHODS: CD1 mice were inoculated intravenously with arthritogenic strain 1/82 of type IV GBS. Exogenous murine IFNgamma or anti-IFNgamma monoclonal antibodies were administered intravenously either 2 hours (-2 hours) before or 18 hours after infection with 1 x 10(7) GBS. Mice were monitored daily for survival and for signs of arthritis. In a subsequent set of experiments, mice were killed at selected times for examination of bacterial clearance, joint histopathology, and cytokine production. RESULTS: Mortality in mice treated with IFNgamma at -2 hours was 100%, compared with 20% in those treated at 18 hours and with 40% in controls. As indicated by the arthritis score, mice treated with IFNgamma at -2 hours developed early and more severe arthritis, whereas those treated at 18 hours had milder arthritis compared with infected controls. Less severe joint pathology in the mice treated with IFNgamma at 18 hours correlated with low levels of interleukin-6 (IL-6) and IL-1beta and a low bacterial load in the joints, whereas rapid onset and worsening of articular lesions in those treated at -2 hours corresponded to early and sustained levels of IL-6. CONCLUSION: The findings of this study demonstrate that the effects mediated by IFNgamma on GBS-induced arthritis may be detrimental or beneficial, depending on the time of administration of IFNgamma in relation to infection with the antigen.

Animals↗
PubMed2000

Synthetic oligodeoxynucleotide containing CpG motif induces an anti-polysaccharide type 1-like immune response after immunization of mice with Haemophilus influenzae type b conjugate vaccine.

Synthetic oligodeoxynucleotides containing CpG motifs [immunostimulatory sequences (ISS)] have been described as potent adjuvants of type 1 immune responses when co-administered with protein or peptide vaccines. To investigate their role in the immune response to polysaccharides (CHO), different preparations of anti-Haemophilus influenzae type b (Hib) conjugate vaccine were administered to mice. The unconjugated CHO did not induce the synthesis of specific antibodies even in the presence of ISS. On the other hand, anti-CHO-specific antibodies significantly increased in the presence of ISS, when tetanus (TT) or diphtheria [cross-reacting material (CRM)] toxoid-conjugated CHO were used to immunize mice. The adjuvant effect was also observed for the immune response against the carrier protein (TT and CRM). ISS insured an early and long-lasting specific IgG production. The effects of ISS on the anti-CHO immune response could be attributed to the amplification of the T help provided by the carrier. The analysis of anti-CHO IgG subclasses showed a significant increase of IgG2a and IgG3 in the presence of ISS. ISS caused a rapid release of IL-12 and IFN-gamma in sera from treated mice. This data provide a first evidence for the ability of ISS to induce an anti-CHO type 1-like immune response and demonstrate that ISS have the potential to increase host antibody response against both the CHO and the protein component of a conjugated vaccine.

Adjuvants, Immunologic↗
PubMed2000

Human monocyte receptors involved in tumor necrosis factor responses to group B streptococcal products.

Several group B streptococcal products have been previously found to stimulate human monocytes to produce tumor necrosis factor alpha. In order to identify the receptors involved in these responses, monocytes were stimulated with purified group- or type-specific carbohydrates or lipoteichoic acid in the presence of anti-receptor monoclonal antibodies, soluble CD14, or lipopolysaccharide-binding protein. Results indicate that CD14 plays an important role in tumor necrosis factor alpha responses to all of the stimuli tested. Moreover, both CD14 and complement receptor type 3 may be involved in responses to the group-antigen.

Animals↗
PubMed2000

Surveillance of anti-tuberculosis drug resistance: results of the 1998/1999 proficiency testing in Italy. SMIRA (Italian Multicentre Study on Antituberculosis Drug Resistance) Study Group.

OBJECTIVE: To determine the accuracy of drug-susceptibility testing (DST) for isoniazid, rifampicin, ethambutol and streptomycin in a provisional network of 22 regional laboratories in Italy. METHODS: Methods, definitions and reference Mycobacterium tuberculosis strains were derived from the WHO/IUATLD Global Project on Anti-tuberculosis Drug Resistance Surveillance. The laboratories were selected based on technical skills required by the project, the number of DST performed annually and geographic localisation. The results (sensitive/resistant strain) were compared with the gold standard (global project results). Sensitivity (ability to detect true resistance), specificity (ability to detect true susceptibility), positive predictive values for resistance and susceptibility, efficiency and reproducibility were calculated in two rounds. RESULTS: Eighteen of 22 laboratories completed the first round of proficiency testing for the four drugs. Sensitivity was 76.6%, specificity 97.2%, predictive value of a resistant test 89.8% and of a susceptible test 86.8%, efficiency 87.8% and reproducibility 92.8%. A second round was performed by all those laboratories that did not achieve > or = 90% agreement with the results of the Global Project. Overall, after the second round, all the parameters except specificity improved, exceeding 90%. CONCLUSIONS: A network of 15 regional laboratories that fulfil the quality criteria for determining the susceptibility of M. tuberculosis to the four primary antituberculosis drugs was established in Italy.

Antitubercular Agents↗
PubMed1999

Activities of eighteen antimicrobial regimens against Mycobacterium avium infection in beige mice.

The therapeutic effect of 18 anti-Mycobacterium avium regimens was examined in beige mice after 91 days of infection. Treatments included monotherapy with clarithromycin (CLA), ethambutol (EMB), amikacin (AMI), rifabutin (RFB), ciprofloxacin (CIP), clofazimine (CLO), and combinations of CLA, CLA-EMB, or CLA-AMI with one of the other drugs. After monotherapy, only AMI and CLA displayed bacteriostatic and/or moderate bactericidal effects in spleens and lungs, while CIP and RFB were totally inactive and CLO and EMB showed intermediate effects against the isolate tested. Resistant mutants were isolated in spleens of mice treated with EMB, CIP, RFB, and CLO-Among two-drug combinations, CLA-RFB, CLA-CIP, and CLA-CLO were significantly more active than RFB, CIP, CLO, respectively, but not more active than CLA alone, in both organs; CLA-AMI and CLA-EMB were bactericidal in spleens and lungs, respectively. Although activity of CLA-EMB was significantly potentiated by RFB and CLO in spleens and lungs, that of CLA-AMI was significantly increased by RFB and CLO only in lungs. The most active regimen in spleens and lungs on day 91 was the combination of all three, namely CLA-AMI-EMB, which reduced the CFU numbers of 2.7 and 7.5 log10, in comparison with day 1 and day 91 counts in untreated control mice, respectively.

Amikacin↗
PubMed1999

Activity of 16 antimicrobial agents against drug-resistant strains of Mycobacterium tuberculosis.

The in vitro activity of 16 antimicrobial agents against 46 drug-resistant strains of Mycobacterium tuberculosis recently isolated from Italian patients was determined. As for first-line antituberculosis drugs, while isoniazid was ineffective against all the strains tested, resistance to streptomycin, rifampicin, pyrazinamide, and ethambutol was 80.4%, 71.7%, 39.1%, and 8.7%, respectively. Among second-line antituberculous drugs, resistance to ciprofloxacin, ofloxacin, and sparfloxacin and to amikacin and kanamycin was around 20%. About 10% of the strains were resistant to capreomycin and cycloserine and 4.3% were resistant to ethionamide; no strain was found to be resistant to thiacetazone, para-aminosalicylic acid, and viomycin. Although all strains displayed a rather continuous distribution of minimal inhibitory concentrations (MICs), a bimodal distribution was observed for rifampicin, amikacin, and kanamicin, with very high MIC values for resistant strains; relatively low MICs were found for fluoroquinolone-resistant strains. Among the small number of strains resistant to second-line agents, low resistant levels were observed. Restriction fragment length polymorphism analysis showed few strain clusters with resistance to first-line antituberculous drugs and aminoglycosides, fluoroquinolones, or both. Altogether, these results showed that second-line agents were still active against the isoniazid-resistant and multiply first-line resistant strains tested, with none or low resistance levels; these observations can be of importance for the treatment of multidrug-resistant tuberculosis in Italy.

Antitubercular Agents↗
PubMed1999

Upregulation of p75 tumor necrosis factor alpha receptor in Mycobacterium avium-infected mice: evidence for a functional role.

The bacterial growth and the production of tumor necrosis factor alpha (TNF-alpha) and TNF receptors (TNF-Rs) in the spleen and blood of BALB/c mice challenged with Mycobacterium avium complex (MAC) were monitored. Infection developed in two phases: the first, up to day 21, was associated with rapid MAC multiplication in the spleen and a drop in the mycobacteremia, and the second was associated with control of the infection in both compartments. In the spleen, TNF-alpha and TNF-RII mRNA levels peaked on day 21 and then slowly decreased; however, no increase in the level of TNF-RI mRNA was observed throughout these experiments. The level of circulating soluble TNF-RII (sTNF-RII) was transiently increased after day 21. In a model in which overproduction of bioactive TNF-alpha was triggered in response to a second infection with MAC, an increased production of sTNF-RII by cultured splenocytes was also observed. Administration of an antagonist anti-TNF-RII monoclonal antibody (MAb 6G1) to infected mice inhibited the bacterial growth in the spleen, suggesting that the TNF-RII and/or sTNF-RII was functionally involved in the mechanisms that control the infection. Overall, these observations suggest that upregulation of TNF-RII or sTNF-RII contributes to modulation of the TNF-alpha antibacterial activity in MAC infections.

Animals↗
PubMed1999

Role of tumor necrosis factor alpha, interleukin-1beta, and interleukin-6 in a mouse model of group B streptococcal arthritis.

Intravenous inoculation of CD1 mice with 10(7) CFU of type IV group B Streptococcus (GBS IV) results in a high incidence of diffuse septic arthritis. In this study the roles of tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 in articular pathology were evaluated. Cytokine levels were quantified in the serum and joints by enzyme-linked immunosorbent assay in mice injected with GBS IV and tested or not tested with pentoxifylline (PTF), a methylxanthine that affects cytokine production. PTF was administered intraperitoneally at a dose of 1 mg/mouse (50 mg/kg of body weight) 1 h after GBS infection and then at 24-h intervals for 4 days. High levels of IL-1beta and IL-6, but not TNF-alpha, were detected in the joints of mice injected with GBS IV from 5 to 15 days after infection, when articular lesions were most frequent and severe. IL-1beta and IL-6 concentrations in the joints significantly (P < 0.001) exceeded those detected in the serum, confirming a strong local production. PTF treatment resulted in a strong reduction of cytokine production and in a marked decrease in both the incidence and severity of arthritis. Inoculation of exogenous murine recombinant IL-1beta or IL-6 in mice treated with GBS IV plus PTF resulted in an incidence and severity of articular lesions similar to those obtained with inoculation of GBS IV alone. No significant effect was obtained with TNF-alpha administration. These data show a strong involvement of IL-1beta and IL-6, but not TNF-alpha, in the pathogenesis of GBS arthritis.

Animals↗
PubMed1999

rpoB mutations in multidrug-resistant strains of Mycobacterium tuberculosis isolated in Italy.

Mutations of rpoB associated with rifampin resistance were studied in 37 multidrug-resistant (MDR) clinical strains of Mycobacterium tuberculosis isolated in Italy. At least one mutated codon was found in each MDR strain. It was always a single-base substitution leading to an amino acid change. Nine different rpoB alleles, three of which had not been reported before, were found. The relative frequencies of specific mutations in this sample were different from those previously reported from different geographical areas, since 22 strains (59.5%) carried the mutated codon TTG in position 531 (Ser-->Leu) and 11 (29.7%) had GAC in position 526 (His-->Asp).

Alleles↗
PubMed1998

Group B streptococci persist inside macrophages.

Group B streptococci (GBS) are an important cause of neonatal sepsis, pneumonia and meningitis. In the early phase of infection, macrophages and polymorphonuclear cells (PMN) are the first immune cells that interact with GBS. In this in vitro study, to gain insight into GBS-macrophage interaction in the absence of type-specific antibodies, we examined the features of GBS survival in thioglycollate-elicited murine peritoneal macrophages and the effect of GBS on the protein kinase C (PKC)-dependent transduction pathway. Our results demonstrate that type Ia GBS, strain 090 (GBS-Ia) and type III GBS strain COH 31r/s (GBS-III), after in vitro phagocytosis survive and persist intracellularly in macrophages for up to 24 and 48 hr, respectively. However, macrophage activation by interferon-gamma (IFN-gamma) and lipopolysaccharide from Escherichia coli (LPS) caused a significant reduction in the time of intracellular persistence. Macrophage activation by IFN-gamma and LPS seems to be a multifactorial event involving multiple intracellular signal pathways also including PKC. Since PKC is one of the components in the signal network leading to macrophage activation and an important target for several intracellular micro-organisms, we wondered whether PKC could have a role in intracellular GBS survival. Both PKC depletion by treatment with phorbol 12-myristate 13-acetate (PMA) for 18 hr and PKC inhibition by Calphostin C rendered macrophages more permissive for the intracellular GBS survival. Furthermore, GBS-infected macrophages were unable to respond to PMA and LPS, activators of PKC, by inducing antimicrobial activity. The ability of GBS to impair PKC-dependent cell signalling was also demonstrated by the reduced c-fos gene expression in GBS-infected macrophages with respect to control macrophages, after LPS stimulation. In conclusion, our results indicate that GBS survive in macrophages and impairment of PKC signal transduction contributes to their intracellular survival.

Animals↗
PubMed1998

Resistance of Streptococcus pyogenes to erythromycin and related antibiotics in Italy. The Italian Surveillance Group for Antimicrobial Resistance.

A survey of antimicrobial resistance in Streptococcus pyogenes, performed within the framework of a national surveillance program, has revealed a dramatic increase in resistance of S. pyogenes to erythromycin in most areas of Italy. In virtually all the centers that provided data for 3 consecutive years, the incidence of erythromycin-resistant strains increased twofold to 20-fold from 1993 to 1995 and was greater than 30% in five of the 14 centers participating in the study. The clonality of erythromycin-resistant isolates was studied in 15 strains isolated from different patients at the Institute of Microbiology of Verona University (Verona). The features of the Verona isolates and the substantially different rates of erythromycin and clindamycin resistance observed in most centers suggest that the spread of different resistance genes in multiple clones might be occurring throughout the country.

Anti-Bacterial Agents↗
PubMed1998

Role of group B streptococcal capsular polysaccharides in the induction of septic arthritis.

The ability of different serotypes of group B streptococci (GBS) to induce septic arthritis in mice was compared. Types II, III, IV, V, VI and VII GBS were investigated. A highly capsulate strain of type III GBS, COH1, and its mutants, COH1-11 (lacking capsular sialic acid) and COH1-13 (non-capsulate), obtained by transposon insertional mutagenesis, were used to assess the role of type-specific polysaccharide on the induction of arthritis. At an intravenous dose of 10(7) cfu/mouse, reference strains of types II, III, IV, VI and VII and type III strain COH1 induced arthritis with an incidence ranging from 70 to 90%. For type V and strain COH1-11, 10(8) cfu/mouse was required to obtain a 50% incidence of arthritis; lesions were not evident with strain COH1-13. The presence of the capsule played a major role in the induction of GBS septic arthritis. The presence and amount of sialic acid in capsular polysaccharide influenced the incidence of articular lesions. The bacterial dose affected the manifestations of arthritis; the less virulent strains of GBS also induced articular lesions when an adequate number of micro-organisms reached the joints.

Animals↗
PubMed1997

High incidence of erythromycin-resistant Streptococcus pyogenes in Monza (North Italy) in untreated children with symptoms of acute pharyngo-tonsillitis: an epidemiological and molecular study.

A retrospective analysis of susceptibility data available for Group A streptococcal isolates collected between January 1990 and January 1996 at the Hospital Microbiology Laboratory of Monza (North Italy), showed a sharp rise in the erythromycin resistance rates during the last 3 years. Streptococcus pyogenes resistant to erythromycin accounted for approximately 1% of strains isolated between 1990 and 1992; the percentage then rose from 5% in 1993 to almost 39% in 1995. In January 1996, the resistance rates peaked to 81%. A prospective controlled study performed between March and May of 1996 to determine the percentage of erythromycin-resistant Group A streptococci isolated in Monza from untreated children with acute pharyngo-tonsillitis, gave further confirmation of a high rate of erythromycin resistance (47%) in this area. Molecular characterization by T-serotyping and pulse-field gel electrophoresis analysis of 25 erythromycin-resistant Group A streptococcal isolates, showed a relatively high degree of heterogeneity among these strains, demonstrating that the increased resistance is not caused by the spread of a single clone.

Acute Disease↗