Biochemical characterization of a novel extended-spectrum beta-lactamase from Pseudomonas aeruginosa 802

Pseudomonas aeruginosa 802 was isolated at Rabta hospital in Tunis and was resistant to extended-spectrum cephalosporins and aztreonam. It produced a pI 7.6 extended-spectrum beta-lactamase (ESBL). The ESBL, named LBT 802, was purified to homogeneity by filtration on Sephadex G-75 followed by CM-Sepharose chromatography and high-performance liquid chromatography (HPLC) on a TSK-gel SP-5PW column. The LBT 802 enzyme had a molecular mass of 30 kDa. It showed a broad-substrate profile by hydrolyzing benzylpenicillin, ampicillin, cephalothin, cephaloridine, cefotaxime, ceftriaxone, and cefpirome but not ceftazidime, cefoxitin, imipenem, or aztreonam. The highest hydrolytic efficiency (Vmax/Km) was obtained for ampicillin, cephalothin, cephaloridine, and benzylpenicillin. Among extended-spectrum cephalosporins the best substrate was ceftriaxone followed by cefotaxime and cefpirome. LBT 802 activity was inhibited by clavulanic acid, sulbactam, imipenem, cefoxitin, and aztreonam. It showed its lowest Ki values for clavulanic acid, imipenem and sulbactam.     

Allergy to macrolide antibiotics. Review of the literature

MACROLIDE CLASSES: Macrolides are characterized by their basic structure made up of a lactonic cycle with 2 osidic chains. They are classified according to the number of carbon atoms in the cycle: 14-membered macrolides (erythromycin, troleandomycin, roxithromycin, dirithromycin, clarithromycin), 15-membered macrolides (azithromycin) and 16-membered macrolides (spiramycin, josamycin, midecamycin). MACROLIDE ALLERGY: Allergy to macrolides is extremely rare (0.4% to 3% of treatments). The little information available in the literature is insufficient to establish the usefulness of diagnostic tests. An immediate IgE-dependent hypersensitivity has been shown with erythromycin in some cases but the mechanism remains unknown and skin tests are quite often negative. Clinical manifestations are the same as those encountered with beta-lactams. It would appear that macrolide allergies are unlikely to be class allergies. This is important as eviction advice could be limited to the single causal macrolide.     

Validation of diffuse correlation spectroscopy against 15O-water PET for regional cerebral blood flow measurement in neonatal piglets

Diffuse correlation spectroscopy (DCS) can non-invasively and continuously asses regional cerebral blood flow (rCBF) at the cot-side by measuring a blood flow index (BFI) in non-traditional units of cm²/s. We have validated DCS against positron emission tomography using ¹⁵O-labeled water (¹⁵O-water PET) in a piglet model allowing us to derive a conversion formula for BFI to rCBF in conventional units (ml/100g/min). Neonatal piglets were continuously monitored by the BabyLux device integrating DCS and time resolved near infrared spectroscopy (TRS) while acquiring ¹⁵O-water PET scans at baseline, after injection of acetazolamide and during induced hypoxic episodes. BFI by DCS was highly correlated with rCBF (R = 0.94, p < 0.001) by PET. A scaling factor of 0.89 (limits of agreement for individual measurement: 0.56, 1.39)×10⁹× (ml/100g/min)/(cm²/s) was used to derive baseline rCBF from baseline BFI measurements of another group of piglets and of healthy newborn infants showing an agreement with expected values. These results pave the way towards non-invasive, cot-side absolute CBF measurements by DCS on neonates.     

Demographic, clinical and therapeutic features of adult visceral leishmaniasis at the Rabta hospital in Tunis (tunisia) from 1983 to 2002

The purpose of this study was to evaluate in a retrospective analysis, cases of Mediterranean visceral leishmaniasis (VL) diagnosed in adults during a 20-year period in a department of infectious diseases. Demographic data, clinical and laboratory features and therapeutic findings were considered. During the study period, 22 cases of VL were diagnosed, and 6 (27%) were associated with HIV infection. Fever and splenomegaly were observed in all cases. Anaemia was constant. The anti-leishmanial IF titer was positive among 21 patients (95%). Smears from bone marrow aspiration were positive at microscopy in 95% of cases. Zymodeme analysis was carried out in nine isolates. L. infantum zymodeme MON-1 was characterized in all cases. Seventeen patients (77%) received meglumine antimoniate (MA) (20 mg SbV/kg per day) and 5 (23%) patients amphotericin B (AB) (0.5-1 mg/kg per day) for an average period of 25 days (10-49 days). Adverse events occurred in 7 patients (32%), among them 4 received AB. Clinical cure was achieved with success in 21 patients (95%). After a successful MA treatment of the initial episode, VL relapse was observed in one HIV-positive patient. Only one HIV-positive patient died from neurological disorders. VL is rare in adults. However, its incidence is increasing everywhere in the world, because of HIV-related cases. Its prognosis depends on the precocity of diagnosis and treatment.     

How to target estrogen receptor-negative breast cancer?

Estrogen receptor (ER)-positive breast cancers generally have a better prognosis and are often responsive to anti-estrogen therapy, which is the first example of a successful therapy targeted on a specific protein, the ER. Unfortunately ER-negative breast cancers are more aggressive and unresponsive to anti-estrogens. Other targeted therapies are thus urgently needed, based on breast cancer oncogene inhibition or suppressor gene activation as far as molecular studies have demonstrated the alteration of expression, or structure of these genes in human breast cancer. Using the MDA-MB.231 human breast cancer cell line as a model of ER-negative breast cancers, we are investigating two of these approaches in our laboratory. Our first approach was to transfect the ER or various ER-deleted variants into an ER-negative cell line in an attempt to recover anti-estrogen responsiveness. The unliganded receptor, and surprisingly estradiol, were both found to inhibit tumor growth and invasiveness in vitro and in vivo. The mechanisms of these inhibitions in ER-negative cancer cells are being studied, in an attempt to target the ER sequence responsible for such inhibition in these cancer cells. Another strategy is trying to inhibit the activity or expression of an oncogene specifically overexpressed in most breast cancers. This approach was recently shown by others to be efficient in breast cancer therapy with HER2-Neu oncogene amplification using Herceptin. Without excluding other molecular putative targets, we have focused our research on cathepsin D as a potential target, since it is often overexpressed in aggressive human breast cancers, including ER-negative tumors, and rarely associated with HER2-Neu amplification. Our first results obtained in vitro on cell lines and in vivo in tumor xenografts in nude mice, illustrate that the mode of action of cathepsin D in breast cancer is useful to guide the development of these therapies. In the past 20 years we have learned that the action of cathepsin D is complex and involves both intracellular and extracellular activities due to its proteolytic activity and to interactions with membrane components without catalytic activity. Each of these mechanisms could be potentially inhibited in an attempt to prevent tumor growth. Breast cancer is a very heterogeneous and multigenic disease and different targeted therapies adapted to each category of breast cancer are therefore required. Validated assays in the primary tumor of molecular markers such as ER, HER2-Neu and cathepsin D should help to predict which targeted therapy should be applied to cure breast cancer patients.     

Plasmodium falciparum causing hemophagocytic syndrome after allogeneic blood stem cell transplantation

We describe a case of Plasmodium falciparum infection in a 25-year-old male patient with a myelodysplastic syndrome, who underwent allogeneic peripheral blood stem cell transplantation (PBSCT) in September 2003. Conditioning regimen consisted of total body irradiation (10 Gy) and cyclophosphamide 60 mg/kg for 2 days. A dose of 4 x 10(6) CD34+ cells/kg was transfused. Engraftment was well documented on day 17 post-transplantation. Spiking fevers occurred on days 19 and 21, associated with a pancytopenia, hepatosplenomegaly and neurological signs. P. falciparum parasites were found on the peripheral blood smear (parasitemia = 23%). Marrow aspiration showed P. falciparum parasites and proliferation of mature histiocytes with hemophagocytosis. Quinine 10 mg/kg i.v. three times a day for 10 consecutive days was given. The fever subsided within 3 days, and pancytopenia vanished in 14 days. Parasitemia cleared in 6 days. The patient left the unit on day 46 with no further complications. The screening of donors showed that infection was acquired from two blood units (from a single donor) given 5 days before transplantation. We report the first case of profound hemophagocytosis in immunosuppressed patient with malaria of high parasitemia after a bone marrow transplant.     

Forme pseudo-pathomimique de granulomatose avec polyangéite (anciennement maladie de Wegener)

Introduction

ANCA vasculitis may involve the skin and develop slowly without specific histology, and without autoantibodies.

Case report

We report a 50-year-old woman who experienced bilateral mastectomy because of ulcero-necrotic, non-specific inflammatory cutaneous lesions of the breasts. First considered by others as a malinger patient, she developed oto-neurological lesions leading to the diagnosis of Wegener's granulomatosis. Five years later, specific antibodies of the disease were present.

Conclusion

Cutaneous involvement by ANCA vasculitis can be isolated for a long time. Physicians must have a high degree of suspicion to avoid diagnostic delay of ANCA vasculitis.     

Asthme du petit enfant : facteurs prédictifs de sévérité et de persistance Analyse de 180 observations

Background : Asthma is the most common chronic disease in infants. In young children, asthma still raises many questions and many points are still being debated. Aim : The aim of this study is to identifies, in asthmatic children, factors predictors of severity and persistence of symptoms. Methods: A retrospective study of asthmatic infants<3 years enrolled in the pediatric department of Sfax over a period of 5 years (2007-2011). We were interested to social and environmental factors, the allergic background, clinical severity of the disease, results of allergic skin tests, treatment and respiratory outcome.Results: We collected 180 children with a sex ratio of 2.2. Family history of atopy and exposition to passive tobacco were noted in 45 % and 52% of cases respectively. The mean age of onset of wheezing was 6.6 months. Skin tests were positives in 32% of cases. At the time of diagnosis, asthma was classified intermittent (21%), mild to moderate (55.6%) and severe (22.2%). Inhaled corticosteroids was initiated in 142 infants (78.8%). Skin tests performed in 84 patients, were positive in 32%. Factors associated with severe asthma were passive smoking, early age of onset, number of hospitalizations for exacerbation and existence of an aggravating factor.Factors predictors of persistence were an early age of onset, caesarean delivery, passive smoking and positive skin tests. Conclusion : Factors associated with persistence of asthma at the individual level remains uncertain. However, atopy and passive smoking are major indicators.