Cobalamin cbiP mutant shows decreased tolerance to low temperature and copper stress in Listeria monocytogenes

BACKGROUND: Listeria monocytogenes is a foodborne pathogen that causes listeriosis in humans. This pathogen activates multiple regulatory mechanisms in response to stress, and cobalamin biosynthesis might have a potential role in bacterial protection. Low temperature is a strategy used in the food industry to control bacteria proliferation; however, L. monocytogenes can grow in cold temperatures and overcome different stress conditions. In this study we selected L. monocytogenes List2-2, a strain with high tolerance to the combination of low temperature +copper, to understand whether the cobalamin biosynthesis pathway is part of the tolerance mechanism to this stress condition. For this, we characterized the transcription level of three cobalamin biosynthesis related genes ( cbiP , cbiB, and cysG ) and the eutV gene, a transcriptional regulator encoding gene involved in ethanolamine metabolism, in L. monocytogenes strain List2-2 growing simultaneously under two environmental stressors: low temperature (8 °C) +copper (0.5 mM of CuSO4 ×5H2O). In addition, the gene cbiP , which encodes an essential cobyric acid synthase required in the cobalamin pathway, was deleted by homologous recombination to evaluate the impact of this gene in L. monocytogenes tolerance to a low temperature (8 °C) +different copper concentrations. RESULTS: By analyzing the KEGG pathway database, twenty-two genes were involved in the cobalamin biosynthesis pathway in L. monocytogenes List2-2. The expression of genes cbiP , cbiB, and cysG, and eutV increased 6 h after the exposure to low temperature +copper. The cobalamin cbiP mutant strain List2-2Δ cbiP showed less tolerance to low temperature +copper (3 mM) than the wild type L. monocytogenes List2-2. The addition of cyanocobalamin (5 nM) to the medium reverted the phenotype observed in List2-2Δ cbiP . CONCLUSION: These results indicate that cobalamin biosynthesis is necessary for L. monocytogenes growth under stress and that the cbiP gene may play a role in the survival and growth of L. monocytogenes List2-2 at low temperature +copper.

Ceratocystis fimbriata agente causal de la enfermedad de marchitez vascular de Tectona grandis L.f. (teca) en Ecuador / Ceratocystis fimbriata causative agent of vascular wilt disease of Tectona grandis L.f. (teak) in Ecuador

Tectona grandis L.f. es una especie forestal de madera dura que, a pesar de no ser nativa de América, su plasticidad de adaptación ha permitido que en Ecuador se establezcan plantaciones intensivas con fines de exportación. Una compleja enfermedad con características de marchitez vascular está matando miles de árboles de diferentes edades en el país. Se planteó conocer el agente fitopatógeno causante de la patogénesis y muerte de los árboles. Se aislaron los hongos Fusarium sp. y Ceratocystis fimbriata Ellis & Halst. desde árboles enfermos. A nivel de invernadero se plantearon los postulados de Koch, para el efecto 30 plantas de T. grandis de cuatro meses de edad por cada tratamiento, se inocularon con los microrganismos como se describe a continuación: T1= C. fimbriata, T2 = Fusarium sp., T3 = C. fimbriata + Fusarium sp., T4 = agar-agar (control). Se empleó un diseño completo al azar (DCA) y las plantas se evaluaron a los 45 días después de inoculadas. Los tratamientos C. fimbriata, y C. fimbriata + Fusarium sp., mostraron mayores volúmenes aparentes de necrosis, con 1.52 cm3 y 1.93 cm3, y plantas muertas por la infección durante el tiempo de evaluación, mientras que Fusarium sp. mostró baja o nula patogenicidad y comportamiento similar al control, con 0.27 cm3 y 0.16 cm3 respectivamente. Estos resultados sugieren que el agente causal de la enfermedad de marchitez vascular en T. grandis es C. fimbriata y sería el primer reporte del fitopatógeno atacando teca en Ecuador. (AU)

Tectona grandisL.f. it is a hardwood forest species, which despite not being native to America, its adaptive plasticity has allowed intensive plantations to be established for export purposes in Ecuador. A complex disease with characteristics of vascular wilt is killing thousands of trees of different ages in the country. It was proposed to know the phytopathogenic agent causing the pathogenesis and death of the trees. Fusarium sp. andCeratocystis fimbriata Ellis & Halst. were isolated from diseased trees. At the greenhouselevel, Koch's postulates were proposed, for the effect 30 four month old T. grandisplants for each treatment were inoculated with the microorganisms as described below: T1 = C. fimbriata, T2 = Fusariumsp ., T3 = C. fimbriata+ Fusariumsp., T4 = agar-agar (control). A complete randomized design (DCA) was used and the plants were evaluated 45 days after inoculation. The treatments C. fimbriata, and C. fimbriata+ Fusariumsp. showed higher apparent volumes of necrosis, with 1.52 cm3and 1.93 cm3, and plants killed by the infection during the evaluation time, while Fusariumsp. showed low or no pathogenicity and behavior similar to the control, with 0.27 cm3and 0.16 cm3respectively. These results suggest that the causative agent of vascular wilt disease in T. grandisis C. fimbriataand it would be the first report of phytopathogen attacking teak in Ecuador. (AU)

Influence of different treatment techniques and clinical factors over the intrafraction variation on lung stereotactic body radiotherapy.

PURPOSE: In the present study we compared three different Stereotactic body radiation therapy (SBRT) treatment delivery techniques in terms of treatment time (TT) and their relation with intrafraction variation (IFV). Besides that, we analyzed if different clinical factors could have an influence on IFV. Finally, we appreciated the soundness of our margins. MATERIALS AND METHODS: Forty-five patients undergoing SBRT for stage I lung cancer or lung metastases up to 5 cm were included in the study. All underwent 4DCT scan to create an internal target volume (ITV) and a 5 mm margin was added to establish the planning target volume (PTV). Cone-beam CTs (CBCTs) were acquired before and after each treatment to quantify the IFV. Three different treatment delivery techniques were employed: fixed fields (FF), dynamically collimated arcs (AA) or a combination of both (FA). We studied if TT was different among these modalities of SBRT and whether TT and IFV were correlated. Clinical data related to patients and tumors were recorded as potential influential factors over the IFV. RESULTS: A total of 52 lesions and 147 fractions were analyzed. Mean IFV for x-, y- and z-axis were 1 ± 1.16 mm, 1.29 ± 1.38 mm and 1.17 ± 1.08 mm, respectively. Displacements were encompassed by the 5 mm margin in 96.1 % of fractions. TT was significantly longer in FF therapy (24.76 ± 5.4 min), when compared with AA (15.30 ± 3.68 min) or FA (17.79 ± 3.52 min) (p < 0.001). Unexpectedly, IFV did not change significantly between them (p = 0.471). Age (p = 0.003) and left vs. right location (p = 0.005) were related to 3D shift ≥2 mm. In the multivariate analysis only age showed a significant impact on the IFV (OR = 1.07, p = 0.007). CONCLUSIONS: The choice of AA, FF or FA does not impact on IFV although FF treatment takes significantly longer treatment time. Our immobilization device offers enough accuracy and the 5 mm margin may be considered acceptable as it accounts for more than 95 % of tumor shifts. Age is the only clinical factor that influenced IFV significantly in our analysis.

Toward an understanding of the hydrogenation reaction of MO2 gas-phase clusters (M = Ti, Zr, and Hf).

A theoretical investigation using density functional theory (DFT) has been carried out in order to understand the molecular mechanism of dihydrogen activation by means of transition metal dioxides MO2 (M = Ti, Zr, and Hf) according to the following reaction: MO2 + H2 → MO + H2O. B3LYP/6-311++G(2df,2pd)/SDD methodology was employed considering two possible reaction pathways. As the first step hydrogen activation by M═O bonds yields to metal-oxo hydride intermediates O═MH(OH). This process is spontaneous for all metal dioxides, and the stability of the O═MH(OH) species depends on the transition metal center. Subsequently, the reaction mechanism splits into two paths: the first one takes place passing through the M(OH)2 intermediates yielding to products, whereas the second one corresponds to direct formation of the product complex OM(H2O). A two-state reactivity mechanism was found for the TiO2 system, whereas for ZrO2 and HfO2 no spin-crossing processes were observed. This is confirmed by CASSCF/CASPT2 calculations for ZrO2 that lead to the correct ordering of electronic states not found by DFT. The results obtained in the present paper for MO2 molecules are consistent with the observed reactivity on surfaces.

Density functional theory study of the oxidation of methanol to formaldehyde on a hydrated vanadia cluster.

Density functional theory was used to study the mechanism for the oxidation of methanol to formaldehyde. A vanadium oxide cluster O=V(OH)(3) has been utilized to represent the catalytic system under hydrated conditions, i.e., in the presence of V-OH hydroxyl groups. Two types of methoxy-intermediates have been considered: a penta-coordinate methoxy-intermediate (OH)(4)V(OCH(3)) and a tetrahedral methoxy-intermediate (OH)(2)VO(OCH(3))(H(2)O). The most plausible reaction pathway corresponds to the process involving first the formation of the tetrahedral methoxide, and a subsequent rate-limiting step where hydrogen is transferred from the methoxy groups toward the oxygen atom of the vanadyl V=O site. The reaction mechanism is a typical two-state reactivity process due to a change of the multiplicity (reactive singlet --> product triplet) along the reaction coordinate accompanied by a reduction of the vanadium center from V(V) (d(0)) to V(III) (d(2)). Minimum energy crossing points were localized and possible spin inversion processes are discussed by means of the intrinsic reaction coordinate approach to find the most favorable reaction pathways. The hydration effect is found to be mainly the destabilization of the methoxy intermediates. An alternative reaction pathway with a lower apparent barrier is presented.

Immunoglobulin G antibody response to infection with coccoid forms of Helicobacter pylori.

An increasing number of studies support a potential role for coccoid forms in Helicobacter pylori infection. Evidence for this was obtained through scanning microscopy, genetic analysis for virulence traits, examination of the presence and activity of key enzymes, and other methods. We studied the serum immunoglobulin G responses to coccoid H. pylori forms by enzyme-linked immunosorbent assay (ELISA) and immunoblotting and compared them with those of bacillary cells. Sera from a total of 295 infected individuals were studied; these included sera from 100 patients with duodenal ulcers, 98 patients with nonulcer dyspepsia, 11 patients with gastroduodenal cancer, and 86 asymptomatic individuals. Initially, we characterized and selected coccoid and bacillary antigenic preparations by one-dimensional (1-D) and 2-D gel electrophoresis and immunoblotting. Data showed that coccoid and bacillary preparations with comparable protein contents have similar patterns in 1-D and 2-D electrophoresis gels and antigenic recognition at blotting. These results revealed that coccoid and spiral antigens in ELISA can equally recognize specific antibodies to H. pylori in sera from infected individuals. The analysis of the spiral and coccoid preparations by Western blotting showed no major differences in antigen recognition. No specific bands or profiles associated with a single gastric condition were identified.

Portación de Staphylococcus aureus enterotoxigénicos en manipuladores de alimentos / Carriage of enterotoxigenic Staphylococcus aureus in food handlers

BACKGROUND: One of the most common pathogens causing alimentary toxi-infections is Staphylococcus aureus (S aureus). The presence of S aureus in food, indicates flaws during food manipulations. For this reason most sanitary norms require the detection of S aureus carriers. AIM: To determine the carriage rate of enterotoxin producing S aureus strains in food handlers, and to evaluate the antibiotic susceptibility to six antimicrobial agents. MATERIALS AND METHODS: A total of 102 food handlers from 19 restaurants in Santiago, were analyzed. Samples for microbiological analysis were obtained with a swab from the retropharynx. RESULTS: S aureus grew in 35 out of the 102 samples obtained (34 per cent). Further analysis revealed that 19/35 (54 per cent) strains were able to produce enterotoxins. Therefore the corrected carriage rate was 19 per cent (19/102). The most frequently detected enterotoxin was the type A (12/19). All S aureus isolates were resistant to penicillin and susceptible to oxacillin, clindamycin, kanamycin, vancomycin and linezolid. CONCLUSIONS: The carriage rate of S aureus in food handlers in similar to the rate reported in the general population in our country. These results confirm the need for education and training programs in food safety, directed to food handlers.

[Evaluation of Nugent and Amsel criteria for the diagnosis of bacterial vaginosis]. / Evaluación de los criterios de Nugent y Amsel para el diagnóstico de vaginosis bacteriana.

BACKGROUND: Bacterial vaginosis (BV) is a common disease in reproductive-age women and is associated to important gynecologic and obstetric complications. AIM: To study the occurrence of BV in apparently healthy women attending family planning clinics, using Amsel and Nugent diagnostic criteria. MATERIAL AND METHODS: Two hundred thirty nine women consulting for symptoms associated to cervicovaginitis, were studied. A sample from the lateral walls of the vagina was obtained with a sterile swab for microscopic analysis, Gram stain and amine test. RESULTS: According to Amsel and Nugent criteria a 31.1% and 31.8% BV prevalence was observed. The sensitivity and specificity of Nugent criteria, compared with Amsel criteria were 83.3% and 92.1%, respectively. CONCLUSIONS: The high prevalence of BV found in this study suggests that this vaginal infection should be diagnosed with standardized methods. Nugent criteria are economic easy to perform and sensitive and we propose that they should be used in local health centers.

[Risk factors for home deaths due to pneumonia among low socioeconomic level Chilean children, Santiago de Chile (1994)]. / Factores de riesgo de fallecer en domicilio por neumonía, de niños chilenos de estratos socioeconómicos bajos, Santiago de Chile (1990-1994).

BACKGROUND: Pneumonia is the main cause of late infant mortality in Chile. Over 60% of these deaths occur at home. The lack of hospital beds and the inadequate outpatient management are contributing factors. AIM: To assess risk factors for home deaths due to pneumonia in Chilean children. PATIENTS AND METHODS: The clinical and environmental histories of 53 (39 male) children that died due to pneumonia in their homes were analyzed. The cause of death was confirmed by necropsy with histopathological studies in all cases. These cases were compared with 88 control children of similar age, gender, socioeconomic status and living in the same geographical area of Metropolitan Santiago. RESULTS: Fifty four percent of deceased children were of less than 3 months of age and only 3 cases and their controls were above 1 year old. Identified risk factors for death were malnutrition with an odds ratio of 30.6 (CI 3.9-64.8, p < 0.001), low birth weight with an odds ratio of 5 (CI 1.8-14.1, p < 0.001), previous admissions to hospitals with an odds ratio of 5.79 (CI 2-17.1, p < 0.001), congenital malformations (mainly cardiac) with an odds ratio of 8.4 (CI 2-39.9, p = 0.001) and a history of bronchial obstruction with an odds ratio of 5.68 (p < 0.001). Identified maternal risk factors were smoking with an odds ratio of 4.13 (CI 1.6-10.7 p < 0.001) and being a teenager with an odds ratio of 4.3 (CI 1.7-11, p < 0.001). Malnutrition, low birth weight, history of previous hospital admissions and having a teenager or smoker mother were considered as independent risk factors using a stepwise analysis. CONCLUSIONS: Chilean low income children have identifiable risk factors for death at their homes due to pneumonia, that can be preventively managed.

Control biológico de la diarrea aguda en adultos. Restauración de la ecología intestinal como tratamiento de la diarrea

Se presenta un estudio multicéntrico doble ciego de 28 pacientes con diarrea en las cuales se prueba la eficiencia de un liofilizado de sacchomyces boulardii y se compara con un placebo.Se revisa el tema del ecosistema intestinal,la flora y su fisiología normal así como el concepto de disbacterias intestinal

Síndrome de Treacher Collins en una familia / Treacher Collins' syndrome in a family

El síndrome de Treacher Collins (STC) fue descrito por primera vez en 1846. La ocurrencia familiar ha sido bien establecida y sigue una transmisión regular dominante, con variabilidad interfamiliar e incremento en la severidad en generaciones sucesivas. Se presenta una paciente de 9 años que consulta en Policlínico de Genética por: hipoacusia, cuadros respiratorios a repetición, retraso del desarrollo psicomotor, dismorfias, observación genopatía. Es hija de padres no cosanguíneos, embarazo controlado, actividad fetal lenta, tabaquismo materno, parto eutócico, con peso y talla de nacimiento normales. Al examen físico destaca: facie angosta, oblicuidad antimongoloide de ojos, ausencia de pestañas y coloboma del borde externo del párpado inferior, hipoplasia malar, nariz de pájaro, micrognatia, implantación anormal de pelo en mejillas, comisura labial hacia arriba, hipoacusia. En antecedentes familiares destaca: madre y hermanastra con rasgos físicos similares e hipoacusia. Evaluadas las tres por Otorrino se confirma en ellas hipoacusia de transmisión bilateral y malformaciones de oído medio. El examen radiológico demuestra la hipoplasia malar. Con todos estos antecedentes se concluye que el fenotipo corresponde a un S.T.C.