Effects of a recombinant gene expression on ColE1-like plasmid segregation in Escherichia coli

<p>Abstract</p> <p>Background</p> <p>Segregation of expression plasmids leads to loss of recombinant DNA from transformed bacterial cells due to the irregular distribution of plasmids between the daughter cells during cell division. Under non-selective conditions this segregational instability results in a heterogeneous population of cells, where the non-productive plasmid-free cells overgrow the plasmid-bearing cells thus decreasing the yield of recombinant protein. Amongst the factors affecting segregational plasmid instability are: the plasmid design, plasmid copy-number, host cell genotype, fermentation conditions etc. This study aims to investigate the influence of transcription and translation on the segregation of recombinant plasmids designed for constitutive gene expression in <it>Escherichia coli </it>LE392 at glucose-limited continuous cultivation. To this end a series of pBR322-based plasmids carrying a synthetic human interferon-gamma (hIFNγ) gene placed under the control of different regulatory elements (promoter and ribosome-binding sites) were used as a model.</p> <p>Results</p> <p>Bacterial growth and product formation kinetics of transformed <it>E. coli </it>LE392 cells cultivated continuously were described by a structured kinetic model proposed by Lee et al. (1985). The obtained results demonstrated that both transcription and translation efficiency strongly affected plasmid segregation. The segregation of plasmid having a deleted promoter did not exceed 5% after 190 h of cultivation. The observed high plasmid stability was not related with an increase in the plasmid copy-number. A reverse correlation between the yield of recombinant protein (as modulated by using different ribosome binding sites) and segregational plasmid stability (determined by the above model) was also observed.</p> <p>Conclusions</p> <p>Switching-off transcription of the hIFNγ gene has a stabilising effect on ColE1-like plasmids against segregation, which is not associated with an increase in the plasmid copy-number. The increased constitutive gene expression has a negative effect on segregational plasmid stability. A kinetic model proposed by Lee et al. (1985) was appropriate for description of <it>E. coli </it>cell growth and recombinant product formation in chemostat cultivations.</p

Le textilome : aspects épidémiologiques, difficultés diagnostiques et implications médico-légales à propos de 5 cas

Le textilome correspond à un corps étranger composé de compresse(s) ou de champ(s) chirurgicaux laissés au niveau d'un foyer opératoire. C’est une complication post-opératoire très rare mais bien  connue. Il peut mimer, tant sur le plan clinique que radiologique, un abcès ou une tumeur rendant ainsi  son diagnostic difficile. Le but de cette étude était de préciser les conditions de survenue, les difficultés diagnostiques du textilome et de discuter ses implications médico-légales à travers l’analyse de cinq cas. Il s’agissait d’une étude rétrospective portant sur cinq cas de textilomes, colligés durant une période de 20 ans, dans le département d’anatomie et de cytologie pathologique à l’Hôpital Universitaire Fatouma Bourguiba de Monastir (Tunisie). Les corps étrangers non  textiles ont été exclus de ce travail. Le recueil des données était effectué à partir des fiches du service d'anatomie et de cytologie pathologique, des dossiers cliniques des patients et des compte-rendus opératoires. L’âge moyen de notre population d’étude était de 55 ans avec une exclusivité féminine. Le délai de découverte du textilome était au-delà de six mois dans tous les cas avec un extrême allant à 24 ans. Des antécédents de chirurgie gynécologique ont été notés dans 3 cas et de chirurgie abdominale dans 2 cas. La sensation d’une masse palpable en intra-abdominale avait motivé les patientes à consulter dans 4 cas. Aucun examen radiologique n’avait permis de confirmer le diagnostic. Dans tous les cas, l’examen anatomopathologique de la masse prélevée avait permis de faire le diagnostic. Ce travail met l’accent sur les implications médico-légales du textilome qui reste toujours décrit dans la pratique des chirurgiens. La prévention nécessite l’éducation et la promotion de moyens technologiques dans la salle opératoire.Mots clés : textilome, chirurgie, anatomie pathologique, implications médico-légales.Textiloma is a surgical complication resulting from foreign materials, such as a surgical sponge,  accidentally left inside a patient's body. Its actual incidence is difficult to determine. It can often present, clinically or radiologically, similar to tumors or abscesses, with widely variable complications and manifestations, making diagnosis difficult. This study aimed to stress out the diagnostic pitfalls and to discuss its medicolegal implications.This study was retrospective including five cases of textiloma collected in the department of anatomy and pathology of the university hospital of Fattouma Bourguiba Monastir (Tunisia) during a period of 20 years. Diagnosis was made after histological tests. Non-textile foreign bodies were excluded from this study. Data collection was summarized from files of anatomy and cytology department, clinical records of patients and operative reports. The average age of our study population was 55 years. All patients were female. The textiloma was discovered beyond six months in all cases with extreme up to 24 years. History of gynecological surgery was noted in 3 cases and abdominal surgery in 2 cases. Clinically, 4 patients consulted for intra-abdominal mass lesion. Radiologically, the diagnosis was misidentified in all cases. Therefore, histological examination of the removed mass helped to make the diagnosis.Keys words: textiloma, surgery, pathology, medico-legal implication