Biomedical subjects

J L Moreira

Publications and source records attributed to J L Moreira.

26 records · Page 2Linked to original sources

PubMedDate not supplied

Modeling retrovirus production for gene therapy. 2. Integrated optimization of bioreaction and downstream processing.

In this work a model envisaging the integrated optimization of bioreaction and downstream processing is presented. This model extends the work presented in part 1 of this pair of papers by adding ultrafiltration to process optimization. The new operational parameters include ultrafiltration time, pressure, and stirring rate. For global optimization, the model uses as constraints the final product titer and quality to be achieved after downstream processing. This extended model was validated with the same system used in part 1, i.e., PA317 cells producing a recombinant retrovirus containing the LacZ gene as a marker in stirred tanks using porous supports. Optimization of the extended model led to the conclusion that bioreaction should have two steps, batch and perfusion, similar to what was found in part 1. Ultrafiltration in a stirred cell should be performed at low pressures and stirring rates to reduce the losses of infective retroviruses. Sensitivity analysis performed on the results of the integrated optimization showed that under optimal conditions the productivity is less sensitive to the parameters related to ultrafiltration than to those associated with bioreaction. These results were interpreted as reflecting the high yield of ultrafiltration (90%). The relevance of the model extension to perform integrated optimization was also demonstrated since a restriction in the specific ultrafiltration area in downstream processing conditioned perfusion duration and perfusion rate in bioreaction. This clearly indicates that overall process optimization cannot be achieved without integrated optimization.

Bioreactors↗

PubMedDate not supplied

Effect of viscosity upon hydrodynamically controlled natural aggregates of animal cells grown in stirred vessels.

The effect of medium viscosity upon cell growth and aggregate characteristics of baby hamster kidney (BHK) cells cultivated in stirred tanks was evaluated. Two thickening agents were tested, 9300 MW dextran and a low-viscosity sodium (carboxymethyl)-cellulose; both were used in two different sets of experiments: (i) 250 cm3 Wheaton spinner flasks with a ball impeller operated at 45 rpm; (ii) 500 cm3 Corning spinner flasks with a paddle impeller, operated at constant power dissipation (88 cm2 s-3). Aggregate diameter and the fraction of cells in aggregates increased with the increase in viscosity. Power laws were applied to the experimental results. A dependence of aggregate size upon power dissipation of the order of -0.19 and kinematic viscosity of 0.34 and 0.49 for the constant agitation and constant power dissipation tests were obtained, respectively. A model based upon the entire universal-equilibrium range (i.e., the entire spectrum of isotropic eddies) was used to predict theoretical relationships between the variables studied. The model leads to a power dependence of -0.25 for the energy dissipated in the entire universal-equilibrium range and between 0.25 and 0.5 for the kinematic viscosity in the viscous dissipation subrange, depending on the energy correlation used; it also gives a good explanation for the dependence of aggregate size on the hydrodynamics of the vessel.

Animals↗

PubMedDate not supplied

Modeling retrovirus production for gene therapy. 1. Determination Of optimal bioreaction mode and harvest strategy.

Although retroviruses are a promising tool for gene therapy, there are two major problems limiting the establishment of viable industrial processes: retrovirus stability and low final yield in the supernatant. This fact emphasizes the need for an effective process optimization, not only at a genetic level but also at a bioprocess engineering level. In part 1 of this paper a mathematical model was developed to optimize the bioreaction yield by determining the best retrovirus harvest strategy in perfusion cultures. PA317 cells producing recombinant retroviruses were used to develop and test this model. Cell culture was performed in stirred tanks using porous supports. The parameters of the proposed model were experimentally determined for batch and perfusion cultures at 32 and 37 degrees C both with and without additives to enhance production; the model was then validated. This model allowed the determination of the optimal values of all operational variables included: batch and perfusion duration and perfusion rate. The highest productivity (2682 virus cm(-)(3) h(-)(1)) was obtained under the following conditions: batch at 37 degrees C for 53 h followed by perfusion at 32 degrees C for 23 h with a perfusion rate of 0.107 h(-)(1). This value was 3.5-fold higher than the best result obtained in batch cultures for the same conditions of titer and quality. A sensitivity analysis of the parameters showed that the parameters that affect most the final productivity depend on the bioreaction phase: cell growth in batch culture and production and product degradation in perfusion culture. In part 2 of this paper, this model is extended to the first step of downstream processing, and the addition of further steps to the process is discussed in order to achieve global process optimization.

Animals↗

PubMedDate not supplied

Epidemiology and antimicrobial resistance of B. fragilis group organisms isolated from clinical specimen and human intestinal microbiota.

Epidemiological aspects and the antimicrobial susceptibility profile of the Bacteroides fragilis group isolated from clinical and human intestinal specimens were examined in this study. B. fragilis group strains were isolated from 46 (37%) of 124 clinical specimens and the source of the samples was: Blood culture (3), intraabdominal infection (27), brain abscess (2), soft tissue infection (17), respiratory sinus (3), pleural aspirate (9), breast abscess (3), surgical infected wound (22), pelvic inflammatory disease (22), chronic otitis media (9) and miscellaneous (7). Intraabdominal and soft tissue infections were responsible for more than half of the clinical isolates. Susceptibility to penicillin, cefoxitin, tetracycline, metronidazole, chloramphenicol and clindamycin was examined. All isolates were susceptible to metronidazole and chloramphenicol. For clindamycin and cefoxitin the resistance rates observed were 21.7% and 10.9% respectively. Susceptibility profiles varied among the different species tested. A total of 37 species of B. fragilis group isolated from intestinal microbiota of individuals who had no antimicrobial therapy for at least 1 month before the sampling was also examined. All strains were also susceptible to chloramphenicol and metronidazole and the resistance rates to clindamycin and cefoxitin were 19.4% and 5.4% respectively. A few institutions, in Brazil, have monitored the antimicrobial susceptibility of B. fragilis group strains isolated from anaerobic infections. The resistance rates to cefoxitin and clindamycin and the variation in susceptibility patterns among the species isolated in this study emphasize the need for monitoring of susceptibility patterns of B. fragilis group organisms isolated, especially at our University Hospitals.

Bacteroides↗

PubMedDate not supplied

Susceptibility of clinical isolates of Bacteroides fragilis group strains to cefoxitin, cefoperazone and ticarcillin/clavulanate.

A total of 40 strains of the B. fragilis group was isolated from clinical specimens in two hospital centers in Fortaleza from 1993 to 1997. The most frequently isolated species was Bacteroides fragilis (19 strains) and most isolates came from intra-abdominal and wound infections. The susceptibility profile was traced for cefoxitin, cefoperazone and ticarcillin-clavulanate by using the agar dilution reference method. All isolates were susceptible to ticarcillin-clavulanate (128/2 microg/ml). Resistance rates of 15 and 70% were detected to cefoxitin (64 microg/ml) and cefoperazone (64 microg/ml), respectively. Such regional results permit a better orientation in choosing this group of antibiotics for prophylaxis and therapy especially in relation to cefoxitin, which is frequently used in the hospital centers studied.

Anti-Bacterial Agents↗

PubMedDate not supplied

[Dermatophytoses in the urban environment and the coexistence of man with dogs and cats].

There have been submitted to clinical exam in laboratory of dermatophytosis and inquired about possible contact with domestic animals (dogs and cats) 158 patients living in the urban area of Fortaleza, that showed lesions suspected of dermatophytosis. This search associated to the obtained data in questionnaires permitted us to identify the frequency of domicile outbreaks. Within the 83 people with dermatosis isolated of human infections, prevailed the anthropophilic species over the zoophilic ones, and that it was observed a confluence of human and animal diagnosis in 100% of the human dermatophytosis zoophilic cases, where the same species were identified in men and contacting animals: M. canis and T. mentagrophytes. As the patients carrying anthropophilic dermatophytosis varied as to the contact with animals, not having been these fungus isolated from none of the contacting animals. Before the low frequency of zoophilic dermatophytosis, it was considered that the intimacy of men with domestic dogs and cats represented was little as a conditional factor of occurrence of dermatophytosis in the urban environment.

Animals↗

PubMedDate not supplied

[Multiple antibiotic resistance mediated by R plasmid in Shigella flexneri strains isolated in the northeast of Brazil].

In Shigella strains were studied the molecular mechanism that mediated the multiply antibiotic-resistance. Twenty-six strains of Shigella flexneri were utilised in this investigation. These strains were submitted to disk diffusion test, mating experiments and plasmid isolation. In relation to antibiotics resistance standard it was observed that all Shigella flexneri strains were resistant to at least, three antibiotics tested. From twenty-six Shigella flexneri strains donors submitted to conjugation process, 34.6% (nine strains) resulted in variable frequency of transconjugants. From strains that conjugated, 100%, transferred the resistance factor acquainted with ampicillin. Being that, in all transconjugants which were observed, just one plasmid with 23.1 Kb was evidenced. This plasmid found in all strains was characterised as the cause of resistance to ampicillin.

Ampicillin Resistance↗

PubMedDate not supplied

[Sepsis in childhood: epidemiological profile and microbiologic diagnosis]

OBJECTIVE: To establish an etiological and epidemiological profile of sepsis among children that were hospitalized in the Hospital Infantil Albert Sabin - HIAS (a reference public hospital for all pediatric diseases in the state of Ceará), since this disease has been of high prevalence in this hospital with considerable mortality. METHODS: All children admitted in the hospital from January 1993 to June 1994, who presented sepsis or developed nosocomial sepsis and presented positive blood cultures were studied prospectively. The epidemiologic study was conducted by gathering information in questionnaire form about the following factors: sex, age, reference area, nutritional status, complaints at admission, sepsis origin (nosocomial or not), and outcome for each case. Microbiologic analysis were formed by means of blood culture, concomitant with sensitivity tests of the isolated bacteria to the most commonly used antibiotics. All samples were processed at the Laboratory of Microbiology of the Health's Science Center of the Federal University in Ceará. RESULTS: 205 children were studied of which 17 presented two septic episodes, making a total of 222 episodes in the period. 56.1% of them were male, 81.4% were less than one-year old, 71.1% were malnourished children and 60.5% came from the countryside of the Ceará State. At the moment of their admission, two-thirds of the children presented gastrointestinal problems (diarrhea) or respiratory complaints, whereas 47.7% of the episodes of sepsis were acquired in hospital. The mortality rate was 56.1%. Blood culture test showed a predominance of the following bacteria: Staphylococcus aureus (24.8%), Klebsiella pneumoniae (22.6%), Pseudomonas aeruginosa (15.2%), Enterobacter sp (11.2%), Escherichia coli (7%), and others (19.2%). CONCLUSIONS: The epidemiological profile of the population in this study was the following: these children were less than one-year old, the majority of them were malnourished and when they were hospitalized, presented with symptoms of diarrhea or respiratory disease. 40% of them had a disease or situation that favored the development of sepsis. The predominant bacterias were Staphylococcus aureus and Klebsiella pneumoniae.

Journal Article↗