Determination of immunoglobulin A against Gardnerella vaginalis hemolysin,sialidase, and prolidase activities in vaginal fluid: implications for adverse pregnancy outcomes

A nested case-control study of low birth weight and preterm delivery was performed with singleton women. Immunoglobulin A (IgA) against the Gardnerella vaginalis hemolysin (anti-Gvh IgA) and sialidase and prolidase activities were determined in vaginal fluid at 17 weeks of gestation. Sialidase positivity and bacterial vaginosis with high prolidase activity were associated with 2- and 11-fold increased risks for low birth weight, respectively. No woman with bacterial vaginosis plus a strong anti-Gvh IgA response had an adverse outcome.     

Abortive potency of Chlamydophila abortus in pregnant mice is not directly correlated with placental and fetal colonization levels

Abortion, placental and fetal colonization, and levels of gamma interferon were analyzed for four Chlamydophila abortus strains presenting antigenic variations in a mouse model. Expression of virulence of these strains varied and indicated that abortion was not directly related to the number of bacteria in the placenta, and thus, other factors may have an important role in activating the abortion process.     

Evaluation of three techniques for detection of low-level methicillin-resistant Staphylococcus aureus (MRSA): a disk diffusion method with cefoxitin and moxalactam,the Vitek 2 system,and the MRSA-screen latex agglutination test

Very-low-level methicillin-resistant Staphylococcus aureus (MRSA), or class 1 MRSA, is often misdiagnosed as methicillin-susceptible S. aureus (MSSA). We evaluated the performances of three methods for detection of low-level methicillin resistance: the disk diffusion method using the cephamycin antibiotics cefoxitin and moxalactam, the Vitek 2 system (bioMérieux), and the MRSA-screen test (Denka). Detection of the mecA gene by PCR was considered to be the "gold standard." We also determined the sensitivity of the oxacillin disk diffusion method with 5- and 1-microg disks and that of the Oxascreen agar assay with 6 mg of oxacillin liter(-1) for detection of MRSA. We compared the distributions of MICs of oxacillin and cefoxitin by the E-test (AB Biodisk), and those of moxalactam by dilutions in agar, for MRSA and MSSA isolates. The 152 clinical isolates of S. aureus studied were divided into 69 MSSA (mecA-negative) and 83 MRSA (mecA-positive) isolates, including 63 heterogeneous isolates and 26 class 1 isolates (low-level resistance). The cefoxitin and moxalactam disk diffusion tests detected 100% of all the MRSA classes: cefoxitin inhibition zone diameters were <27 mm, and moxalactam inhibition zone diameters were <24 mm. The Vitek 2 system and the MRSA-screen test detected 94 and 97.6% of all MRSA isolates, respectively. The sensitivities of the 5- and 1-microg oxacillin disks were 95.2 and 96.4%, respectively, whereas that of the Oxascreen agar screen assay was 94%. All of the tests except the 1-microg oxacillin disk test were 100% specific. For the class 1 MRSA isolates, the sensitivity of the Vitek 2 test was 92.3%, whereas those of the MRSA-screen test and the disk diffusion method with cefoxitin and moxalactam were 100%. Therefore, the cefoxitin and moxalactam disk diffusion methods were the best-performing tests for routine detection of all classes of MRSA.     

Impairment of intramacrophagic Brucella suis multiplication by human natural killer cells through a contact-dependent mechanism

Brucella spp. are facultative intracellular bacteria that can establish themselves and cause chronic disease in humans and animals. NK cells play a key role in host defense. They are implicated in an early immune response to a variety of pathogens. However, it was shown that they do not control Brucella infection in mice. On the other hand, NK cell activity is impaired in patients with acute brucellosis, and recently it was demonstrated that human NK cells mediate the killing of intramacrophagic Mycobacterium tuberculosis in in vitro infection. Therefore, we have analyzed the behavior of Brucella suis infecting isolated human macrophages in the presence of syngeneic NK cells. We show that (i) NK cells impair the intramacrophagic development of B. suis, a phenomenon enhanced by NK cell activators, such as interleukin-2; (ii) NK cells cultured in the presence of infected macrophages are highly activated and secrete gamma interferon and tumor necrosis factor alpha; (iii) impairment of bacterial multiplication inside infected cells is marginally associated with the cytokines produced during the early phase of macrophage-NK cell cocultures; (iv) direct cell-to-cell contact is required for NK cells to mediate the inhibition of B. suis development; and (v) inhibition of B. suis development results from an induction of NK cell cytotoxicity against infected macrophages. Altogether, these findings show that NK cells could participate early in controlling the intramacrophagic development of B. suis in humans. It seems thus reasonable to hypothesize a role for NK cells in the control of human brucellosis. However, by impairing the activity of these cells in the acute phase of the illness, the pathogen should avoid this control.     

Loss of fibroblast Thy-1 expression correlates with lung fibrogenesis

Fibroblasts consist of heterogeneous subpopulations that have distinct roles in fibrotic responses. Previously we reported enhanced proliferation in response to fibrogenic growth factors and selective activation of latent transforming growth factor (TGF)-beta in fibroblasts lacking cell surface expression of Thy-1 glycoprotein, suggesting that Thy-1 modulates the fibrogenic potential of fibroblasts. Here we report that compared to controls Thy-1-/- C57BL/6 mice displayed more severe histopathological lung fibrosis, greater accumulation of lung collagen, and increased TGF-beta activation in the lungs 14 days after intratracheal bleomycin. The majority of cells demonstrating TGF-beta activation and myofibroblast differentiation in bleomycin-induced lesions were Thy-1-negative. Histological sections from patients with idiopathic pulmonary fibrosis demonstrated absent Thy-1 staining within fibroblastic foci. Normal lung fibroblasts, in both mice and humans, were predominantly Thy-1-positive. The fibrogenic cytokines interleukin-1 and tumor necrosis factor-alpha induced loss of fibroblast Thy-1 surface expression in vitro, which was associated with Thy-1 shedding, Smad phosphorylation, and myofibroblast differentiation. These results suggest that fibrogenic injury promotes loss of lung fibroblast Thy-1 expression, resulting in enhanced fibrogenesis.     

In vitro activity of tigecycline against clinical isolates of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, Serratia marcescens and Enterobacter cloacae

BACKGROUND AND PURPOSE: Strains of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae have spread widely in Taiwan hospitals. In this study, we evaluated the in vitro antimicrobial activity of tigecycline against ESBL-producing Enterobacteriaceae, including Klebsiella pneumoniae, Serratia marcescens and Enterobacter cloacae. METHODS: 104 confirmed ESBL-producing bacteria were isolated from 4 hospitals in mid- and southern Taiwan between 2000 and 2006. The in vitro activity of tigecycline against these ESBL producers was tested by use of Etest strips. RESULTS: The minimal tigecycline concentration at which 50% of isolates were inhibited and minimal concentration at which 90% of isolates were inhibited for ESBL-producing isolates ranged from 0.38 to 0.75 mug/mL and 0.5 to 1.5 mug/mL, respectively. CONCLUSIONS: Tigecycline, a new semisynthetic glycylcycline, may be considered an alternative drug of choice for patients infected with ESBL-producing bacteria.     

Latent membrane protein-1 of Epstein-Barr virus inhibits cell growth and induces sensitivity to cisplatin in nasopharyngeal carcinoma cells.

Nasopharyngeal carcinoma is closely associated with Epstein-Barr virus (EBV) and the EBV encoded latent membrane protein-1 expression (LMP1) is commonly found in the tumour cells. LMP1 has been shown to be involved in modulation of cell growth in B cells but the biological properties of LMP1 expression in nasopharyngeal carcinoma cells are less defined. In this study, a full length LMP1 gene was introduced into an EBV negative nasopharyngeal carcinoma cell line, CNE2, and five LMP1-expressing clones were isolated. Expression of LMP1 did not confer cell growth advantage in CNE2 cells; instead, it induced growth inhibition both in vitro and in vivo. In addition, the LMP1 transfected cells were more susceptible to cisplatin-induced cell death and showed 1.4-4.0-fold increased sensitivity to cisplatin compared to the vector infected control clones. The effect of LMP1 on the balance of Bcl-2 and Bax ratio may play a role in inducing susceptibility to cisplatin-induced cell death. These results demonstrated that LMP1 did not confer growth advantage in CNE2 cells, suggesting that expression of LMP1 may not be crucial in sustaining cell growth in established cell lines. Alternatively, LMP1 alone may not be sufficient to facilitate nasopharyngeal carcinoma cell growth and additional oncogenic factors may be needed along with LMP1 in modulating the malignant property of nasopharyngeal carcinoma.     

Studies on cell surface antigens of mouse leukemic and normal lymphocytes. IV. Functional studies on mouse T lymphocyte subpopulations. B. Lyt phenotype of cytotoxic T lymphocytes and their precursors in B6-Lyt-1.1 mice.

Lyt phenotype of in vitro generated alloreactive cytotoxic T lymphocytes (CTL) and their precursors in B6-Lyt-1.1 (Thy-1.2, Lyt-1.1, Lyt-2.2) congenic strain of mice was studied. The generation of CTL in vitro was completely abrogated by pretreatment of responder cells with antisera to Thy-1.2, Lyt-1.1 and Lyt-2.2 antigens and complement. Mixing of anti-Lyt-1.1-pretreated cells with anti-Lyt-2.2-pretreated cells did not restore CTL generation indicating that both Lyt antigens are expressed on the same precursor cell population. The effect of anti-Lyt sera was specific because the generation of CTL was prevented only when cells from strains possessing appropriate Lyt alleles were pretreated. CTL were eliminated by lysis with anti-Thy-1.2 serum and strongly reduced by anti-Lyt-1.1 and anti-Lyt. 2.2 sera. Nevertheless, a small but significant proportion of CTL was insensitive to lysis with anti-Lyt sera. These data indicate that a phenotype of precursor cells and of majority of CTL is Thy-1.2+ Lyt-1.1+ Lyt-2.2+.