Molecular analysis of streptogramin resistance in enterococci

The new semi-synthetic streptogramin antibiotic combination quinupristin/dalfopristin (Synercid) is a promising alternative for a treatment of infections with multiple resistant gram-positive pathogens, e.g. glycopeptide- and multi-resistant Enterococcus faecium. Streptogramins consist of two unrelated compounds, a streptogramin A and B, which act synergistically when given in combination. Mechanisms conferring resistance against both components are essential for resistance against the combination in E. faecium. In this species resistance to streptogramin A compounds is mediated via related acetyltransferases VatD and VatE. Resistance against streptogramins B is either encoded by the widespread ermB gene cluster conferring resistance to macrolide-lincosamide-streptogramin B antibiotics or via expression of the vgbA gene, which encodes a staphylococcal-type lactonase. E. faecalis is intrinsically resistant to streptogramins. Due to a wide use of streptogramins (virginiamycins S/M) in commercial animal farming a reservoir of streptogramin-resistant E. faecium isolates had already been selected. Determinants for streptogramin resistance are localized on plasmids that can be transferred into an E. faecium recipient both in vitro in filter-matings and in vivo in the digestive tracts of rats. Hybridization and sequencing experiments revealed a linkage of resistance determinants for streptogramins A and B on definite plasmid fragments.     

Molecular identification of Wolbachia from the filarial nematode Mansonella ozzardi

Mansonella ozzardi, a filarial parasite of humans in Latin America, has been shown to harbour intracellular bacteria not yet identified. Here we show that these bacteria, like those of other filarial nematodes, belong to the genus Wolbachia (alpha 2 Proteobacteria; Rickettsiales). Their unambiguous placement in the Wolbachia group was shown by 16S rDNA sequence analysis. However, the exact position of the Wolbachia from M. ozzardi relative to the other wolbachiae is not clear. Indeed, 16S rDNA sequence analysis places this bacterium at a deep branch in Wolbachia evolution. It is interesting that analysis of the 5S rDNA gene spacer of the nematode host also suggests that the genus Mansonella, together with the genus Loa, could represent a deep-branching lineage in filarial evolution.     

Expression and localization of mutant p16 proteins in melanocytic lesions from familial melanoma patients

Little is known about the correlation between the loss of p16 expression and tumor progression in familial melanoma; no systematic study has been conducted on p16 expression in melanocytic tumors from patients carrying germline CDKN2A mutations. We analyzed 98 early primary lesions from familial patients, previously tested for germline CDKN2A status, by quantitative immunohistochemistry using 3 p16 antibodies. We found that p16 expression was inversely correlated with tumor progression and was significantly lower in melanomas, including in situ lesions, than in nevi. Of other features analyzed, tumor thickness showed the most significant correlation with p16 levels. Lesions from mutation-negative patients displayed combined nuclear and cytoplasmic staining. However, some mutation-positive lesions (ie, G101W, 113insR, M53I, R24P, and 33ins24), including benign nevi, showed nuclear mislocalization, confirming previous studies suggesting that subcellular distribution indicates functional impairment of p16.     

Presence of autoantibodies to apolipoprotein A-1 in patients with acute coronary syndrome further links autoimmunity to cardiovascular disease

Anti-apolipoprotein A-1 (Apo A-1) autoantibodies were described in autoimmune disorders such as systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) and might be involved in the genesis of arterial and venous thrombotic events. To investigate the presence of these autoantibodies in patients with acute coronary syndrome (ACS) without other features of autoimmunity, we set up an enzyme-linked immunosorbent assay (ELISA) for anti-Apo A-1 antibodies. We used it to investigate their prevalence in ACS as compared to SLE and APS and correlated them to plasma Apo A-1 and serum amyloid A protein (SAA) concentrations. The prevalence of anti-Apo A-1 autoantibodies in the healthy control group was 1% (1/92), but was significantly higher in other groups: 21% (11/53) in ACS group (P=0.001), 13% (12/92) in SLE and/or APS group (P=0.005). Multiple linear regression revealed a significant correlation between plasma Apo A-1 (r=-0.72, P=0.013), plasma SAA concentration (r=0.76, P=0.0066) and anti-Apo A-1 IgG titre in ACS patients. The presence of anti-Apo A-1 autoantibodies in patients with ACS highlights an additional link between autoimmunity, inflammation and atherosclerosis.     

Erratum: Neurofibromatosis type 1 (NF1): Identification of eight unreported mutations in NF1 gene in Italian patients

In the original version of this article, the title was incorrect. Please find the correct title given here. The publisher deeply regrets this error. The original article to which this Erratum refers was published in Human Mutation 22:179–180 Human Mutation(2003) 22(2) 179–180     

Histopathology,hormone products,and clinicopathological profile of endocrine tumors of the upper small intestine: A study of 44 cases

Forty-two duodenal and 3 upper jejunum tumors from 44 patients were investigated. All tumors were tested immunohistochemically for gastroenteropancreatic hormones and general endocrine cell markers. Twenty-eight of the 45 tumors (62%) proved to be gastrin cell tumors, with (12 cases) or without (16 cases) associated Zollinger-Ellison syndrome. Zollinger-Ellison syndrome was part of type 1 multiple endocrine neoplasia syndrome in 3 cases. Twenty-three of the 28 gastrin cell tumors (82%) were from proximal duodenum, 2 were from the second part of the duodenum, and 3 were from the upper jejunum. Seven cases were somatostatin cell tumors, 6 of which were from the ampullary region; 5 cases were associated with biliary tract disease and 2 with associated cutaneous neurofibromatosis. Four ganglioneuromatous paragangliomas, from the ampullary region or nearby duodenum, showed somatostatin cells, coupled with pancreatic polypeptide cells in 2 cases. Two serotonin-producing argentaffin carcinoids were also identified. In addition to the main cell type, 30 tumors showed one or more, usually minor, cell populations producing somatostatin, serotonin, cholecystokinin, pancreatic polypeptide, insulin, neurotensin, or the alpha chain of human chorionic gonadotropin. Only 3 tumors lacked hormone immunoreactivity. Some correlation has been noted between histological structure and hormone content of tumor cells, with prevalence of broad gyriform trabeculae and vascular pseudorosettes among gastrin cell tumors, tubuloacinar patterns among somatostatin cell tumors, thin parallel trabeculae among PP cell growths, and a solid nest pattern among argentaffin carcinoids. Deep infiltration of the intestinal wall was observed in 22 tumors, 6 of which also had metastases to local lymph nodes. All metastatic cases were among ZES tumors or ampullary somatostatin cell tumors. Ganglioneuromatous paragangliomas and nonfunctioning gastrin cell tumors had essentially benign behavior, even when involving deep strata of the intestinal wall. Post operative follow-up study of 36 cases, including all metastatic tumors, showed no evidence of tumor-related death or progressive tumor disease.     

Changes in luteinizing hormone and insulin secretion in polycystic ovarian syndrome

Uncertainties regarding the pathogenetic changes underlying the polycystic ovarian syndrome (PCOS) have been reported. The aim of this study was to investigate the endocrine and metabolic features of PCOS patients in relation to luteinizing hormone (LH) secretion. Androgen assays, oral glucose tolerance tests, hyperinsulinaemic euglycaemic clamps and gonadotrophin releasing hormone (GnRH) tests were performed in 100 patients. Sixty-six patients scheduled as hyperinsulinaemic and 34 as normoinsulinaemic showed similar concentrations of LH, follicle stimulating hormone (FSH), LH/FSH ratio, and LH response to GnRH testing. Hyperinsulinaemic subjects showed higher body mass index (BMI), insulin resistance, testosterone and free androgen index levels compared with those of normoinsulinaemic subjects; when clustered in relation to their LH basal concentrations, the two groups obtained differed only in androstenedione concentrations. Considering both insulin and LH plasma concentrations, four groups were obtained. Hyperinsulinaemia and hyper-LH secretion were not related in 54% and coexisted in the same subjects in 26% of cases. Hyperinsulinaemia as well as hyper-LH secretion affected the expression of the syndrome; the insulinaemia was directly correlated with testosterone concentrations and all metabolic parameters that affected the free androgen index. The LH concentrations were related to androgen production and were independent of BMI and insulin concentrations. It is concluded that the degree of hormonal alteration is the final sum of such pathogenetic factors.     

Modulation of interferon-γ receptor during human T lymphocyte alloactivation

Previous work has shown that neutralization of physiologically secreted interferon(IFN)-γ or blockade of its receptor during T lymphocyte activation inhibits both proliferation and cytotoxic T lymphocyte generation, suggesting that IFN-γ plays a crucial role in T lymphocyte induction and differentiation. In this study, the kinetics of the surface expression of the 90-kDa IFN-γ receptor (IFN-γR) was followed during human mixed lymphocyte reaction (MLR) to alloantigens. IFN-γR mRNA is constitutively expressed on resting peripheral blood lymphocytes emerging from nylon wood column (NW-PBL) and its expression increases two- to threefold on alloactivated NW-PBL. IFN-γR protein is poorly expressed on the membrane of resting CD3⁺ cells, but up-modulates after 3-day MLR and sharply down-modulates at day 6. Both the p55 and the p75 chains of interleukin-2 receptor (IL-2R) were shown to up-modulate in parallel with IFN-γR, whereas they were still highly expressed at day 6. After alloactivation, IFN-γ and IL-2 secretion starts at 24 h, peaks at day 3 and decreases just when IFN-γR and IL-2R begin to up-modulate. Proliferation peaks at day 6. Lastly, stimulation with distinct cell populations showed that the intensity of lymphocyte proliferation, IFN-γR membrane up-modulation, and IFN-γ and IL-2 secretion are regulated in a parallel manner, thus suggesting that they are interrelated. Taken as whole these results demonstrate that increased expression of IFN-γR on T lymphocytes can be a critical event during their activation, and strongly support the hypothesis that IFN-γ/IFN-γR interaction provides a signal for its progression.     

Neutrophil-mediated cellular cytotoxicity triggered by immobilized aggregated IgG: Anin vitro model of cell injury during immune complex diseases

Normal human neutrophils were found to destroy ox red blood-cell targets when incubated on micropore filters coated with aggregated IgG, as determined by the⁵¹Cr release method. An intact neutrophil oxidative metabolism was essential for the cytotoxic event, since cells from patients with chronic granulomatous disease failed to exert any cytolysis. The target-cell destruction was prevented by catalase, azide, and cyanide and was enhanced by superoxide dismutase, suggesting involvement of the myeloperoxidase-hydrogen peroxide system. Neutrophil-mediated cytotoxicity was markedly amplified by the chemotactic peptideN-formyl-methionyl-leucylphenylalanine, as a result of an increased activity of the myeloperoxidase-hydrogen peroxide cytolytic system itself. This system of cytotoxicity provides a direct evidence for the neutrophil capacity of destroying bystander target cells under conditions simulating thein vivo immunologically mediated tissue injury and offers an excellent model to study events occurring during immune complex diseases.Supported by Grant 83.00902.96/115.11547 from the Italian CNR-PFCCN.