Novel genetic determinants of low-level aminoglycoside resistance in Pseudomonas aeruginosa

Pseudomonas aeruginosa strains isolated from patients with persistent lung infections and cystic fibrosis have been found to gradually develop aminoglycoside resistance over time. The aim of this study was to identify potential contributors to low-level aminoglycoside resistance, which may cause such graduated increases in resistance. The Harvard P. aeruginosa PA14 nonredundant library, consisting of approximately 5,800 mutants, was screened for twofold or greater increases in tobramycin resistance. Mutants carrying mutations in a total of 135 unique genes were identified and confirmed to have reduced susceptibility to tobramycin. Many of these genes were involved predominantly in energy metabolism; however, most of these mutants did not exhibit growth defects under the conditions tested, although some exhibited the small-colony phenotype and/or defects in growth under anaerobic conditions. Lipopolysaccharide mutants were also identified, and it was found that tobramycin had a reduced ability to permeabilize the outer membranes of these mutants. The results of this study emphasize the complexity of the interactions that tobramycin may have within the bacterial cell and introduce a large number of novel genes which may play a role in tobramycin resistance.     

Changes in reducing power profile of gastric juice in patients with active duodenal ulcer.

Reactive oxygen species have been postulated to play a role in the pathogenesis of mucosal GI injury and in peptic ulcer disease (PUD). The low molecular weight antioxidants (LMWA) group plays an important role in the defense mechanism of the GI tract against oxidative damage, and is a major component of the reducing capacity of biological tissues and fluids. We hypothesized that altered gastric LMWA anti oxidative status might play a role in the pathogenesis of upper GI disorders such as PUD and could be evaluated by measuring gastric juice reducing power. The aim of the present study was to determine, by cyclic voltammetry, changes in the overall antioxidant activity of the gastric juice in active duodenal ulcer (DU) obtained during upper endoscopy from patients as compared with normal subjects. The results show that in 28/37 (76%) of the control subjects, gastric juice demonstrated a reducing power of at least two anodic waves indicating at least two different LMWA groups. Three or more anodic waves were recorded in 12 normal subject (32%). In contrast, 16/25 (64%) of gastric juice samples obtained from active DU patients exhibited only one anodic wave usually at a high potential (>900 mV). These results imply that gastric juice normally possesses a reducing power profile that can be determined by cyclic voltammetry. This profile is significantly changed in untreated DU disease. These changes in active DU may indicate decreased gastric antioxidant activity reflecting reduced mucosal protection that leading to increased susceptibility of the gastro-duodenum to injury.     

Diagnosis and classification of myelodysplastic syndrome: International Working Group on Morphology of myelodysplastic syndrome (IWGM-MDS) consensus proposals for the definition and enumeration of myeloblasts and ring sideroblasts

The classification of myelodysplastic syndromes is based on the morphological criteria proposed by the French-American-British (FAB) and World Health Organization (WHO) groups. Accurate enumeration of blast cells, although essential for diagnosis of myelodysplastic syndrome and for assignment to prognostic groups, is often difficult, due to imprecise criteria for the morphological definition of blasts and promyelocytes. An International Working Group on Morphology of Myelodysplastic Syndrome (IWGM-MDS) of hematopathologists and hematologists expert in the field of myelodysplastic syndrome reviewed the morphological features of bone marrows from all subtypes of myelodysplastic syndrome and agreed on a set of recommendations, including recommendations for the definition and enumeration of blast cells and ring sideroblasts. It is recommended that (1) agranular or granular blast cells be defined (replacing the previous type I, II and III blasts), (2) dysplastic promyelocytes be distinguished from cytologically normal promyelocytes and from granular blast cells, (3) sufficient cells be counted to give a precise blast percentage, particularly at thresholds that are important for diagnosis or prognosis and (4) ring sideroblasts be defined as erythroblasts in which there are a minimum of 5 siderotic granules covering at least a third of the nuclear circumference. Clear definitions and a differential count of a sufficient number of cells is likely to improve precision in the diagnosis and classification of myelodysplastic syndrome. Recommendations should be applied in the context of the WHO classification.     

Endocrinology: Prevention of irreversible chemotherapy-induced ovarian damage in young women with lymphoma by a gonadotrophin-releasing hormone agonist in parallel to chemotherapy

To examine whether the concomitant administration of a gonadotrophin-releasinghormone agonist (GnRHa) during combination chemotherapy to youngwomen with lymphoma may facilitate preservation of gonadal function,a prospective clinical protocol was undertaken in 18 cyclingwomen with lymphoma, aged 15–40 years. Thirteen patientssuffered from Hodgkin disease (HD) and 5 from non-Hodgkin lymphoma.After informed consent a monthly injection of depot D-TRP⁶-GnRHawas administered for a maximum of 6 months starting prior tochemotherapy. Most of these patients (15/18) were treated withthe MOPP/ABV(D) combination chemotherapy followed by mantlefield irradiation in 10 patients. Hormonal profile [luteinizinghormone (LH), follicle stimulating hormone (FSH), oestradiol,testosterone, progesterone, insulin-like growth factor (IGF)-1,prolactin] was taken before the GnRHa/chemotherapy co-treatment,and monthly thereafter until resuming spontaneous ovulationand menses. This group of prospectivey treated lymphoma patientswas compared to a matched control group of 18 women (aged 17–40years) who have been treated with chemotherapy, mostly MOPP/ABV(14/18), with (11) or without (7) mantle field radiotherapy.Fourteen had Hodgkin's and four non-Hodgkin's lymphoma. Gonadalfunction was determined clinically, hormonally (LH, FSH, oestradiol,progesterone), and sono-graphically. Two of the patients ineach group died from refractory disease. Of the remaining 16patients, 15 (93.7%) resumed spontaneous ovulation and menseswithin 3–8 months of termination of the combined chemotherapy/GnRHaco-treatment. In contrast, only seven (39%) of the 18 similarlytreated patients in the control group (chemotherapy withoutGnRHa) resumed ovarian cyclic activity (regular menses). Theother 11 experienced premature ovarian failure (POF) (61%).Our preliminary data suggest a possible significant protectiveeffect of GnRHa co-treatment with chemotherapy from irreversibleovarian damage (POF).     

MRI parameters of Alzheimer's disease in an Arab population of Wadi Ara, Israel

Magnetic resonance imaging (MRI) findings are reported from 15 individuals in an Arab-Israeli community who were diagnosed with Alzheimer's disease (AD). The quantitative parameters that were used for MRI analyses included gradings (0-3) and linear measurements of different brain structures. Generalized tissue loss was assessed by combined measurements of the ventricles (ventricular score, VS) and sulcal grading and width (SG, SW, respectively). Loss of brain tissue in specific regions of interest, eg, temporal lobes, basal ganglia, and midbrain, was evaluated by precise measurements. We observed abnormal tissue characteristics, expressed as high intensity foci in white matter on T2W sequences, as well as tissue loss, both generalized and focal. Most notable were changes involving the head of the caudate nuclei, the midbrain, and to a lesser degree, medial temporal structures.     

Biochemical and genetic characterization of the beta-lactamases of Y. aldovae, Y. bercovieri, Y. frederiksenii and "Y. ruckeri" strains

The beta-lactamases of five strains each of Y. aldovae and "Y. ruckeri", and 10 strains each of Y. bercovieri and Y. frederiksenii were examined phenotypically and genetically. Beta-lactamase activity and induction assays and SDS-PAGE were applied for phenotypic characterization of these enzymes. Genotypically, PCR experiments applying degenerated primer pairs for the detection of AmpC beta-lactamase genes were performed. All yersiniae yielded specific amplification products for ampC and all these strains expressed beta-lactamases. Each species produced its own, species-specific AmpC beta-lactamase. Inducibility of these enzymes was shown for Y. bercovieri, but not for the low-level enzyme producing species Y. aldovae and "Y. ruckeri". In contrast to these species, induction tests for Y. frederiksenii revealed heterogeneous results. Whereas the beta-lactamases of 6 of 10 strains were inducible, the enzyme activities after induction in the remaining four were similar to those measured without an inducer. In addition to the AmpC enzyme, all Y. frederiksenii strains expressed a second beta-lactamase belonging to Ambler class A. The present study enlarges the knowledge about the beta-lactamases of four novel Yersinia species that are likely to be involved in human disease. Beta-lactamases of Y. aldovae and "Y. ruckeri" have been characterized for the first time.