The main goal of this work was to identify the mechanisms responsible for carbapenem resistance in 61 Chilean clinical isolates of Enterobacteriaceae (Enterobacter spp., Serratia marcescens, Morganella morganii, Escherichia coli and Klebsiella pneumoniae) with reduced susceptibility to at least one carbapenem (ertapenem, imipenem or meropenem). All of the isolates were analysed for the presence of carbapenemases, extended spectrum b-lactamases (ESBLs), AmpC enzymes and outer-membrane proteins. None of the isolates exhibited carbapenemase activity nor did they have any of the carbapenemase genes that were screened for. Most of the 61 strains produced at least one ESBL and/or one AmpC enzyme and either lost their porins or had altered porins according to sequence analysis. The distribution of ESBLs and AmpC enzymes was different among the species studied. Resistance in K. pneumoniae and E. coli isolates was associated with ESBLs; in M. morganii isolates, resistance was attributed to overexpression of an AmpC enzyme; and in Enterobacter spp. isolates, resistance was associated with both types of enzymes. In K. pneumoniae isolates, porin integrity was more a determinant of carbapenem resistance than the presence of ESBLs, whereas in isolates of Enterobacter spp., M. morganii and S. marcescens, the presence of an overexpressed AmpC enzyme was associated with higher imipenem and meropenem MIC values. Therefore, carbapenem resistance in Chilean isolates is not due to true carbapenemases but rather to a combination of porin loss/alteration and b-lactamase activity. The fact that carbapenemases were not detected in this study is unique, given that many countries in the region have already reported the presence of these enzymes.

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Streptococcus pyogenes causes a variety of infections because of virulence factors such as capsular hyaluronic acid and M protein. The aim of this study was to determine emm types and capsule phenotype in 110 isolates of S. pyogenes from patients with invasive (sterile sites) and non-invasive (mainly pharyngitis) infections in Chile, and the relationship between both virulence factors. The most abundant types found were emm12, emm1, emm4 and emm28 and their distribution was similar to that seen in Latin America and developed countries, but very different from that in Asia and Pacific Island countries. Ten of 16 emm types identified in pharyngeal isolates were found in sterile-site isolates, and three of nine emm types of sterile-site isolates occurred in pharyngeal isolates; three emm subtypes were novel. The amount of hyaluronic acid was significantly higher in sterile-site isolates but did not differ substantially among emm types. Only three isolates were markedly capsulate and two of them had mutations in the csrR gene that codes for a repressor of capsule synthesis genes. We found a non-random association between emm types and csrR gene alleles suggesting that horizontal gene transfer is not freely occurring in the population.

The activity of daptomycin against 141 Staphylococcus aureus and 63 Streptococcus agalactiae isolates was assessed. The isolates were previously characterized and showed resistance to the antibiotics normally used against gram-positive cocci. Daptomycin was active against 100% of the isolates (minimum inhibitory concentration [MIC(90)] = 0.5 microg/ml, for both species). This antibiotic shows good in vitro activity; therefore, it is an excellent therapeutic alternative against these isolates.

Presence of metallo ß-lactamases in imipenem-resistant Pseudomonas aeruginosa Background: Metallo-ß-lactamases (MBL) confer high resistance to carbapenems in Pseudomonas aeruginosa (Psae). They are encoded in mobile elements of different genes (VIM, IMP, SMP, GIM), along with other resistance genes. Aim: To detect the presence of MBL in imipenem resistant Psae strains. Material and methods: Fifty-nine imipenem resistant Psae strains isolated from January 2004 to August 2005 in a University Clinical Hospital, were included. The presence of MBL was studied by Etest (phenotypic) and genotypic polymerase chain reaction (PCR) methods. To rule out a nosocomial outbreak, MBL positive strains, were studied by pulse field gel electrophoresis. Results: The presente of MBL was detected in eleven strains. All were type VIM and were not clonally related. There was no concordance between phenotypic and genotypic MBL detecting methods. All the strains were also multiresistant.

Fueron evaluados 621 estudiantes, con un rango de edad de 6 a 13 años. A cada niño se le tomaron, medidas antropométricas de peso, talla, circunferencia de cintura, pliegue de tríceps y de pantorrilla; se utilizó el programa Epi Info Versión 3.3.2 para calcular el índice de masa corporal (IMC), estableciendo como obesidad un valor mayor o igual al percentil 95 y el sobrepeso un valor mayor o igual al percentil 85 y menor al 95 de acuerdo con la edad y sexo, tomando en cuenta la medición de circunferencia de cintura se determinó obesidad abdominal mayor o igual al percentil 90 de acuerdo con la edad y sexo; el porcentaje de grasa corporal de determino por la ecuación de slaughter. Las variables con prevalencias más altas resultaron las del estado nutricional, con donde el 19,1% de la población estudiada presentó sobrepeso y 25,1% obesidad. La prevalencia combinada de sobrepeso y obesidad en niños fue de 51,3% mientras que en niñas 37,4%. Los resultados encontrados en estos niños muestran claramente altas prevalencias de sobrepeso y obesidad. Inclusive más altas al promedio de los niños mexicanos. Concluyendo que en esta escuela es necesario tomar medidas, como poner en marcha programas de actividad física y nutrición orientados a frenar el problema del sobrepeso y obesidad.

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