RESUMEN
Planetary rings are observed not only around giant planets1, but also around small bodies such as the Centaur Chariklo2 and the dwarf planet Haumea3. Up to now, all known dense rings were located close enough to their parent bodies, being inside the Roche limit, where tidal forces prevent material with reasonable densities from aggregating into a satellite. Here we report observations of an inhomogeneous ring around the trans-Neptunian body (50000) Quaoar. This trans-Neptunian object has an estimated radius4 of 555 km and possesses a roughly 80-km satellite5 (Weywot) that orbits at 24 Quaoar radii6,7. The detected ring orbits at 7.4 radii from the central body, which is well outside Quaoar's classical Roche limit, thus indicating that this limit does not always determine where ring material can survive. Our local collisional simulations show that elastic collisions, based on laboratory experiments8, can maintain a ring far away from the body. Moreover, Quaoar's ring orbits close to the 1/3 spin-orbit resonance9 with Quaoar, a property shared by Chariklo's2,10,11 and Haumea's3 rings, suggesting that this resonance plays a key role in ring confinement for small bodies.
RESUMEN
Resistance phenotypes characterized by minimum inhibitory concentration, disk diffusion and beta-lactamase production were determined in 434 isolates from patients attending the Sexually Transmitted Disease Service at Dr. José Maria Cullen Hospital in Santa Fe, Argentina. Susceptibility tests to penicillin, tetracycline, ciprofloxacin, espectinomycin, azithromycin and ceftriaxone were performed. Pulsed-field gel electrophoresis was conducted made to on three ciprofloxacin-resistant isolates. Epidemiologically speaking, three interesting events should be highlighted: during 1997, plasmid-mediated high level tetracycline-resistant strains were observed (33.3%); from 2002 to 2004 a significant increase of plasmid-mediated penicillin-resistant strains was registered (9.7% to 34.8%); and in the year 2000 the first two quinolone-resistant strains emerged in the province. In our hospital, the first azithromycin-resistant isolate emerged in 2004. We therefore emphasize the importance of the Clinical Microbiology Laboratory in order to provide information for the empiric treatment of this infection.
Asunto(s)
Antibacterianos/farmacología , Neisseria gonorrhoeae/efectos de los fármacos , Argentina , Farmacorresistencia Bacteriana , Hospitales , Humanos , Pruebas de Sensibilidad Microbiana , Neisseria gonorrhoeae/aislamiento & purificación , Factores de TiempoRESUMEN
Se determinaron los fenotipos de resistencia caracterizados por la concentración inhibitoria mínima, la difusión con discos y la producción de β-lactamasa de 434 aislamientos de Neisseria gonorrhoeae obtenidos de pacientes atendidos en el Servicio de Enfermedades de Transmisión Sexual del Hospital Dr. José María Cullen, Santa Fe, Argentina. Se realizaron pruebas de sensibilidad a los siguientes antimicrobianos: penicilina, tetraciclina, ciprofloxacina, espectinomicina, azitromicina y ceftriaxona. A tres aislamientos resistentes a ciprofloxacina se les realizó electroforesis de campo pulsado. Se destacaron tres situaciones epidemiológicas de interés: en el año 1997, alta incidencia de aislamientos con resistencia plasmídica a tetraciclina (33,3%); en el período 2002-2004, un aumento significativo de la resistencia plasmídica a penicilina (9,7% a 34,8%); y en el año 2000, la emergencia de dos de los tres primeros aislamientos con resistencia a quinolonas del país. El primer aislamiento resistente a azitromicina en nuestro hospital emerge en el 2004. Este trabajo jerarquiza el rol del Laboratorio de Microbiología Clínica en la orientación del tratamiento empírico de la gonorrea.
Resistance phenotypes characterized by minimum inhibitory concentration, disk diffusion and β-lactamase production were determined in 434 isolates from patients attending the Sexually Transmitted Disease Service at Dr. José María Cullen Hospital in Santa Fe, Argentina. Susceptibility tests to penicillin, tetracycline, ciprofloxacin, espectinomycin, azithromycin and ceftriaxone were performed. Pulsed-field gel electrophoresis was conducted made to on three ciprofloxacin-resistant isolates. Epidemiologically speaking, three interesting events should be highlighted: during 1997, plasmid-mediated high level tetracycline-resistant strains were observed (33.3%); from 2002 to 2004 a significant increase of plasmid-mediated penicillin-resistant strains was registered (9.7% to 34.8%); and in the year 2000 the first two quinolone-resistant strains emerged in the province. In our hospital, the first azithromycin-resistant isolate emerged in 2004. We therefore emphasize the importance of the Clinical Microbiology Laboratory in order to provide information for the empiric treatment of this infection.