An outbreak of multiply resistant Pseudomonas aeruginosa in a neonatal unit: plasmid pattern analysis.

An outbreak of infection due to multiply resistant Pseudomonas aeruginosa occurred from March to April 1986 in a neonatal unit. Affected neonates were receiving ventilation support and the mortality rate was high. Plasmid analysis and antibiograms indicated that the outbreak was due to a single strain. A survey of bacteria isolated from respirators, potable water and hands of personnel working in the unit failed to recover the outbreak strain. Lack of sterilization of respirators and overcrowding were considered to be the causes of the outbreak and reinforcement of the importance of aseptic techniques helped in its termination.

Adherence of multiresistant strains of Klebsiella pneumoniae to cerebrospinal fluid shunts: correlation with plasmid content.

A nosocomial multiresistant Klebsiella pneumoniae strain (KMD01) isolated from a patient with an infected ventriculoperitoneal (V-P) shunt was found to contain three plasmids of mol. wts (10(6)) c. 85, 50 and 2.4. A derivative isogenic strain (KMD11) carrying only the plasmids of mol. wts (10(6)) 50 and 2.4 was obtained spontaneously by plating the parent strain. The absence of the plasmid of mol. wt 85 X 10(6) in strain KMD11 correlated with an increased adherence to V-P catheters and glass surfaces, as well as autoagglutination in minimal medium. Bacterial cells containing the whole set of plasmids (strain KMD01) also showed the incorporation into the outer membrane of a new polypeptide (mol. wt, c. 41 X 10(3)), when grown in minimal medium. The presence of this polypeptide correlated with absence of autoagglutination, as shown by strain KMD01 under these cultural conditions. These data suggest that the cell-surface characteristics in K. pneumoniae may be affected by the plasmid content of the strain. Since nosocomial strains of K. pneumoniae usually contain one or more plasmids, and strains easily exchange these extrachromosomal elements, it seems reasonable to speculate that new variants with higher V-P shunt colonisation effectiveness, like the one described in this work, may also evolve in nature.

Producción de un polipéptido con actividad antiviral por fusión del gen interferón-alpha 2 humano al gen lacZ del bacteriófago M13mp8 / Production of a polypeptide with antiviral activity by fusion of the alpha 2 IFN gen to the lacZ gen in the M13mp8 bacteriophage

Un gen de IFN-* recientemente aislado en nuestro laboratorio a partir de una librería de ADN crosomal humano, fue genéticamente manipulado in vitro para poder acortar la secuencia señal y mejorar el rendimiento de IFN en cultivos bacterianos. Primero, la secuencia señal fue acortada en una extensión equivalente a nueve codones, usando la enzima de restricción HacIII y la secuencia remanente fue fusionada en fase con el codón iniciador del gen lacZ presente en el bacteriófago M13mp8. Uno de los clones recombinantes fue analizado en detalle. Este clon mostró una alta inestabilidad del inserto y una baja producción de actividad IFN, con un rendimiento similar al obtenido con el gen pre-IFN-*2 completo. El gen fusionado lacZ/IFN-* fue entonces transferido por clonaje mplecular al plásmido pBR322. Uno de los clones obtenidos mostró una buena estabilidad del plásmido híbrido, y aunque el rendimiento de actividad de IFN fue bajo (3x 10 a la 5 unidades/ml de extracto bacteriano crudo) la producción se mantuvo aún después de más de 20 pases. Finalmente, la secuencia señal recombinante presente en este clon fue nuevamente acortada en una extensión equivalente a 4 codones y se encontró que uno de los nuevos clones incrementaba aproximadamente en 20 veces el nivel de producción de actividad IFN. A pesar de que el polipéptido sintetizado constituye un producto de fusión, la actividad biológica antiviral de IFN parece quedar conservada

Deletions in Klebsiella pneumoniae R plasmids induced by growth in the presence of acridine orange at high temperature.

The generation in vivo of plasmids deleted at specific sites in strains of Klebsiella pneumoniae containing R plasmids, by treatment with high concentrations of acridine orange (1.2 mg/ml) at 42 degrees C are reported. These deletions seem to be site specific because loss of specific restriction fragments after digestion with restriction enzymes was demonstrated.