One hundred eighty-four clinical isolates of Klebsiella pneumoniae were recovered from August 1996 to October 1997 at the Pediatric Hospital of the Instituto Mexicano del Seguro Social in Mexico City, Mexico. Most of the isolates were collected from the neonatal intensive care unit and infant wards, which are located on the same floor of the hospital. Isolates were genotypically compared by pulsed-field gel electrophoresis with XbaI restriction of chromosomal DNA. Of 184 clinical isolates, 91 belonged to cluster A and comprised three subtypes (A1, A2, and A3), while 93 isolates, comprising two minor clones, B (10 isolates) and C (7 isolates), and 76 unique patterns, were considered unrelated isolates (URI). Susceptibility patterns were indistinguishable in both groups. Fifty extended-spectrum -lactamase-producing isolates, including 34 from clone A and 16 from URI, were examined for further studies. Molecular and genetic analysis showed that 47 of 50 clinical isolates expressed the SHV-5 -lactamase. This enzyme, in combination with TEM-1, was encoded in a >170-kb conjugative plasmid. Results indicate that dissemination of this resistance was due to clonal and horizontal spread.
After isolation of multiresistant (MR) Pseudomonas aeruginosa from 3 hospitalized patients in a paediatric intensive care unit (PICU), a prospective surveillance programme was established to detect infected and/or colonized patients in the hospital. Isolates were examined by means of outer membrane protein (OMP) profiles, serotyping and DNA genomic analysis using pulsed-field gel electrophoresis (PFGE). Fifty-five P. aeruginosa strains were isolated from 23 hospitalized patients during September and October 1997. The median hospital stay before isolation of P. aeruginosa was 8 d. PFGE demonstrated that the same clone infected 14 patients, 4 of whom were not hospitalized in the PICU. Susceptibility patterns and OMP profiles correlated with PFGE results in 37.8% and 36.4% of cases, respectively. Serotype O11 correlated with pattern A in 77% of cases and serotype O4 correlated with unrelated strains in 75% of cases but did not discriminate between outbreak and unrelated isolates. Extensive investigation of cultures failed to identify a reservoir of P. aeruginosa. PFGE was superior to OMP analysis and serotyping for discriminating between strains. The possible mode of acquisition for most of the patients infected with the same clone was cross-contamination.
Resumen -Los fertilizantes fosforados pueden contener cadmio (Cd) y al utilizarlos pueden entrar en las cadenas tróficas. El objetivo de este estudio fue evaluar el efecto de la fertilización fosforada sobre la concentración de Cd disponible en cuatro tipos de suelos de Chile, que pertenecían a los ordenes Inceptisol, Alfisol, Ultisol y Andisol. Los dos tratamientos usados fueron el testigo sin fertilización y la aplicación de una dosis de corrección con un fertilizante comercial, superfosfato triple (SFT), que tenía una concentración de 53,2 mg de Cd por kg de fertilizante. La dosis de fertilizante aplicada fue la necesaria para alcanzar un nivel de 30 mg kg -1 de P-Olsen. Los suelos se incubaron en estufa durante 90 días, a 25ºC y humedad de capacidad de campo. El diseño experimental fue completamente al azar, con tres repeticiones para cada suelo y donde la unidad experimental fue un contenedor con 250 g de suelo seco. Se midió Cd disponible a los 1, 2, 7, 14, 21, 36, 49, 63, 77 y 90 días después de la incubación. La aplicación de P en dosis agronómica, utilizando fertilizante con alto contenido de Cd, tuvo un efecto estadísticamente significativo sobre la concentración de Cd disponible en los suelos estudiados, sin embargo, no hubo efecto del tiempo de incubación en la disponibilidad de Cadmio.Términos para índece: metales pesados, sorción del suelo, contaminación, niveles tróficos. Effect of phosphate fertilizer on the soil cadmium content in four types of Chilean soilsAbstract -Phosphate fertilizers may contain cadmiun (Cd) which may become part of the trophic chains. The objective of this study was to evaluate the effect of phosphate fertilizer on available Cd content in four Chilean soil types, belonging to orders Alfisol, Inceptisol, Ultisol and Andisol. Treatments consisted of control without P fertilizer and P application with commercial triple superphosphate containing 53.2 mg Cd per kg of fertilizer. The dose of phosphate fertilizer applied was enough to reach the level of 30 mg kg -1 P-Olsen. The soils were incubated up to 90 days, at 25 o C and field capacity. The experimental design was completely randomized with three replications, and the experimental unit was a container with 250 g of soil (dry matter). Available Cd was measured at 1, 2, 7, 14, 21, 36, 49, 63, 77, and 90 days after incubation. Application of P at agronomic rate using fertilizer with a high Cd content produced significant effects on available Cd content in the soil types studied, however, incubation time period did not present such effect.
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