[Multicenter study on the monitoring of in vitro susceptibility to tigeeyeline in Santiago, Chile]. / Estudio multicéntrico de la vigilancia de la susceptibilidad in vitro a tigeciclina en Santiago de Chile.

The objective of this multicenter study was to determine tigecycline susceptibility rates, measured by agar diffusion, in nine hospitals in Santiago and to compare these rates with other antimicrobials. Each center studied 20 strains per month. All intermediate and fully resistant strains as well as 10% of susceptibile strains were also studied by the broth microdilution method. Overall, 2301 strains were studied displaying the following susceptibility rates for tigecycline: 100% for Streptococcus sp, Enterococcus sp, and E. coli respectively, 99.8% for Staphylococcus sp, 93% for Klebsiella and 80% for Acinetobacter baumarmii. For Proteus, Providencia and Morganella the susceptibility rates were 4%. For cefotaxime-resistant Klebsiella and imipenem-resistant A. baumarmii susceptibility rates were 95% and 80% respectively. The agar diffusion and broth dilution method were 100% concordant for tigecycline susceptible strains but only 27% for resistant or intermediate strains represented mostly by Acinetobacter baumannii. The majority of these strains (57/59) proved to be susceptible after retesting. The great majority (96,6%) of strains tested from nine Chilean hospitals proved to be susceptible to tigecycline with exception for Proteus, Providencia and Morganella (66% resistance). Using the agar diffusion method for measuring tigecycline susceptibility to A. baumannii may be misleading.

Estudio multicéntrico de la vigilancia de la susceptibilidad in vitro a tigeciclina en Santiago de Chile / Multicenter study on the monitoring of in vitro susceptibility to tigeeyeline in Santiago, Chile

The objective of this multicenter study was to determine tigeeyeline susceptibility rates, measured by agar diffusion, in nine hospitals in Santiago and to compare these rates with other antimicrobials. Each center studied 20 strains per month. All intermedíate and fully resistant strains as well as 10 percent of susceptibile strains were also studied by the broth microdilution method. Overall, 2301 strains were studied displaying the foliowing susceptibility rates for tigeeyeline: 100 percent for Streptococcus sp, Enterococcus sp, and E. coli respectively, 99.8 percent for Staphylococcus sp, 93 percent for Klebsiella and 80 percent for Acinetobacter baumarmii. For Proteus, Providencia and Morganella the susceptibility rates were 4 percent. For cefotaxime-resistant Klebsiella and imipenem-resistant A. baumarmii susceptibility rates were 95 percent and 80 percent respectively. The agar diffusion and broth dilution method were 100 percent concordant for tigeeyeline susceptible strains but only 27 percent for resistant or intermedíate strains represented mostly by Acinetobacter baumannii. The majority of these strains (57/59) proved to be susceptible after retesting. The great majority (96,6 percent) of strains tested from nine Chilean hospitals proved to be susceptible to tigeeyeline with exception for Proteus, Providencia and Morganella (66 percent resistance). Using the agar diffusion method for measuring tigeeyeline susceptibility to A. baumannii may be misleading.

Para conocer la susceptibilidad a tigeciclina por difusión en agar en nueve hospitales de Santiago y comparar la susceptibilidad con otros antimicrobianos, se diseñó este estudio multicéntrico. Cada centro estudió 20 cepas mensualmente. Las intermedias, resistentes y 10 por cientoo de las susceptibles se re-testearon y estudiaron por microdilución en caldo. Se incluyeron 2.304 cepas. Fueron susceptibles a tigeciclina Strep-tococcus sp (100 por cientoo), Enterococcus sp (100 por ciento), E. coli (100 por cientoo), Staphylococcus sp (99,8 por ciento), Klebsiella pneumoniae (93 por ciento) y Acinetobacter baumannii (80 por ciento). En Proteus, Providencia y Morganella la susceptibilidad fue 4 por cientoo. Klebsiella resistente a cefotaxima y Acinetobacter resistente a imipenem, 95 por cientoo y 80 por cientoo fueron susceptibles a tigeciclina, respectivamente. La concordancia en cepas susceptibles y en las enviadas como resistentes o intermedias (A. baumannii) fue 100 por cientoo y 27 por cientoo respectivamente. El re-testeo confirmó que la mayoría eran susceptibles. Los patrones de susceptibilidad bacteriana muestran muy buena actividad in vitro a tigeciclina. La resistencia in vitro de A. baumannii por difusión en agar debe interpretarse con precaución.

Estudio molecular de 6 episodios de infección intrahospitalaria causados por staphylococcus aureus meticilino-resistente / Molecular study of 6 episodes of intrahospitalary infection due to methicillin resistant staphylococcus aureus

A critical step in any epidemiologic research concerning nosocomial infections is the precise identification of the responsible pathogen. The present work utilized a molecular approach-plasmids identification, restriction lengght polymorphism DNA analysis and random amplified polymorphic DNA for the characterization of 6 nosocomial outbreaks due to 52 strains of methicillin-resistant staphylococcus aureus (MRSA). In these episodes, the clinic-epidemiologic and phenotipic analysis (antibiotype) pointed to a nosocomial infection. Through molecular analysis it was possible to establish in a very precise way, clonality due to MRSA strains in 2 of the studied outbreaks; the same type of analysis allowed to eliminate a MRSA clonal origin in the remainder 4 episodes. The antibiogram was not an useful analytic tool due to its poor discriminatory power. Also, through a PCR procedure, it was possible to identify the presence of the gen mecA in every of the 52 MRSA strains studied

Sensibilidad in vitro de microorganismos anaeróbicos / In vitro sensibility of anaerobic microbial

Los estudios in vitro de sensibilidad antibiótica frente a bacterias anaeróbicas son escasos en nuestro medio. El presente trabajo evaluó la actividad antimicrobiana de seis antibióticos frente a 301 cepas de microorganismos anaeróbicos. Destaca la sensibilidad del grupo Bacteroides fragilis grupo, frente a la clindamicina, en especial cuando se compara con la actividad de metronidazol. Los Bacteroides melaninogenicus presentan una resistencia de 33% al metranidazol, condición que no está descrita en la literatura extranjera. La penicilina y el cloramfenicol son los más activos frente a los microorganismos Gram positivos anaeróbicos. La actividad de metronidazol frente a este grupo de microorganismos es la más baja de todos los antibióticos estudiados. La clindamicina, el cloramfenicol y los nitroimidazólicos presentan mejor actividad que la penicilina frente a los Clostrium perfringens

Estado actual de la sensibilidad in vitro de cocáceas gram positivas aeróbicas / State of in vitro sensibility of gram positive aerobic cocci

Debido a la escasez de publicaciones recientes acerca de las sensibilidades in vitro de cocáceas Gram positivas aeróbicas, hemos considerado de interés analizar estos datos. Del análisis realizado se desprende que los microorganismos de mayor resistencia son los Staphylococcus aureus meticilino-resistentes, para los que el antibiótico adecuado en su manejo clínico debiera ser vancomicina, por sus características de sensibilidad. Los streptococcus faecalis conservan sus niveles de resistencia frente a ampicilina y penicilina. Por último, los Staphylococcus epidermidis no aparecen tan sensibles a las cefalosporinas de 1ª generación como en los datos aparecidos en la literatura extranjera. Se recomienda como alternativa en los Staphylococcus aureus la clindamicina, previa determinación de sensibilidad