The susceptibility in vitro of 71 isolations of V. cholerae was evaluated: 24 of clinical origin and 47 strains of clinical and environmental origin collected in the epidemic of 1991 and during the outbreak epidemic of 1998 in Lima-Peru respectively. The biochemical and serological tests carried out established that 43 (60,6%) corresponded to the serogroup O1 Ogawa of the 1998 epidemic; 26 (36.6%) were of the serotype Inaba, being 24 of them isolated in 1991. Two strains did not belong to the serogroup O1. By means of disk diffusion method and Minimal Inhibitory Concentration (MIC), 15 strains with multi-resistance to antibiotics were determined, 10 of which were of clinical origin and 5 of natural origin, showing 9 antibiotypes with different resistance pattern. The evaluation of susceptibility in front of the vibriostatic agent O/129, demonstrated that 11.4% of the strains, collected in 1998, presented resistance to a concentration of 150 µg. A direct relationship among the resistance that presented the strains of clinical and environmental origin isolated in 1991 and 1998 was established as much for tetracycline, sulfa/trimethoprim and 0/129; 88.6% of the clinical strains of the year 1998 presented resistance to these three drugs, while 100% of clinical strains isolated in 1991 were sensitive to O/129 (150 µg), sulfa/trimethoprim and tetracycline. We conclude that V. cholerae O1 has increased its resistance to antimicrobial drugs of clinical use in the same way it is also losing susceptibility to the vibriostatic compound O/129 for what their use is not recommended for taxonomic purposes

The Peruvian Andean Plateau, one of the main production areas of native varieties of Chenopodium quinoa, is exposed to abrupt decreases in environmental temperature, affecting crop production. Plant-growth-promoting rhizobacteria that tolerate low temperatures could be used as organic biofertilizers in this region. We aimed to bioprospect the native psychrotolerant bacteria of the quinoa rhizosphere in this region that show plant-growth-promoting traits. Fifty-one strains belonging to the quinoa rhizosphere were characterised; 73% of the total could grow at low temperatures (4, 6, and 15 °C), whose genetic diversity based on DNA amplification of interspersed repetitive elements (BOX) showed 12 different profiles. According to the 16S rRNA sequence, bacterial species belonging to the classes Beta- and Gammaproteobacteria were identified. Only three (6%) isolates identified as nonpathogenic bacteria exhibited plant-growth-promoting activities, like IAA production, phosphate solubilization, growth in a nitrogen-free medium, and ACC deaminase production at 6 and 15 °C. ILQ215 (Pseudomonas silesiensis) and JUQ307 (Pseudomonas plecoglossicida) strains showed significantly positive plant growth effects in aerial length (about 50%), radicular length (112% and 79%, respectively), and aerial and radicular mass (above 170% and 210%, respectively) of quinoa plants compared with the control without bacteria. These results indicate the potential of both psychrotolerant strains to be used as potential organic biofertilizers for quinoa in this region.

Over the past few decades, research in agricultural microbiology has highlighted the efficacy of plant growth promoting rhizobacteria (PGPR) in inducing seedling emergence, promoting the increase in plant height, weight and overall crop yield. A number of microbial isolates have shown promising antagonistic activity against several soilborne pathogens. In this study, twelve bacterial strains were isolated from root rhizosphere of Peruvian native highlands crops, i.e Goldenberry (Physalis peruviana L.), Potato (Solanum tuberosum L.) and Maca (Lepidum meyenii Walp.). The strains were identified using 16S rRNA gene PCR amplification and sequencing and were characterized for their PGPR activities. Among these isolates, all strains were found to be able to produce indol-acetic acid, two strains were able to solubilize hydroxyapatite, bi- and tri-calcium phosphate and the remaining others were able to solubilize at least one source of inorganic phosphate. Of 12 isolates, 10 strains showed antagonistic activity against Fusarium solani, 5 showed activity against Alternaria alternata and 9 inhibited growth of Curvularia lunata. It was also found that out of 12 isolates, three were able to induce tomato seedling emergence by 75% compared to the control in in-vitro assays. 16S rRNA gene sequence based analysis of these strains confirmed that, of 12 strains, 4 were members of genus Pseudomonas, 3 belong to genus Bacillus, 2 were related to genus Rahnella and 1 each belong to the genus Stenotrophomonas, Serratia and Streptomyces.

El objetivo del presente trabajo fue determinar si los puestos de venta de carne de pollo son una fuente de contaminación con Escherichia coli shigatoxigénica (STEC) en mercados de abastos. Se tomaron hisopados de la superficie de manos, tablas de picar y mesas de expendio de 50 puestos de expendio de carne de pollo en el distrito de San Juan de Miraflores, Lima, Perú (n=150 muestras). Se realizó aislamiento microbiológico estándar e identificación molecular de los genes stx1, stx2 y eaeA mediante PCR. El 42% (63/150) y 25.3% (38/150) de las muestras fueron positivas a E. coli y STEC, respectivamente. El 84% (42/50) y 66% (33/50) de los puestos de venta poseían al menos una de las superficies contaminadas con E. coli y STEC, respectivamente. El 68.3% (43/63) de las cepas de E. coli aisladas fueron patógenas por presentar al menos un gen evaluado. De estas, 38 cepas fueron STEC y presentaron los genes stx1 (19.0%, 12/63), stx2 (14.3%, 9/63) y las asociaciones: stx1 y stx2 (12.7%, 8/63), stx1, stx2 y eaeA (6.3%, 4/63), stx2 y eaeA (4.8%, 3/63), y stx1 y eaeA (3.2%, 2/63). Se observaron prácticas de higiene deficientes en el puesto de venta y durante el expendio. Se confirma que los puestos de venta de carne de pollo del mercado limeño son fuente potencial de contaminación de STEC.

En el presente trabajo, se reporta la síntesis y caracterización de nanopartículas magnéticas de magnetita/plata (Fe3O4/Ag) para el estudio de sus propiedades antibacterianas frente a las bacterias Enterobacter aerogenes (Gramnegativa) y Enterococcus faecalis (Gram-positiva). Las nanopartículas magnéticas de magnetita (MNPs) se sintetizaron por el método de solgel, usando bromuro de cetiltrimetilamonio (CTAB) como surfactante. Posteriormente, en la dispersión coloidal de magnetita, se llevó a cabo la reducción química in situ de iones de plata, usando glucosa como agente reductor y polivinilpirrolidona (PVP) como agente dispersante, para obtener un nanocompuesto magnético Fe3O4/Ag. El análisis morfológico y espectroscópico de las nanopartículas de Fe3O4 y del nanocompuesto de Fe3O4/Ag fue realizado mediante la espectroscopia infrarroja con transformada de Fourier (FTIR), Raman, y Mössbauer (MS), además de la técnica de difracción de rayos X (DRX), la microscopía electrónica de barrido (SEM) y espectroscopia de energía dispersiva de rayos X (EDS). Las nanopartículas de Fe3O4 resultaron esféricas con un diámetro medio de 10 nm y el nanocompuesto de Fe3O4/Ag con un tamaño medio de 28 nm, el test antibacteriano indicó que el uso del nanocompuesto de Fe3O4/Ag a una concentración de 5 mg·mL-1 permite una inhibición total del crecimiento de los microorganismos estudiados a partir de una concentración inicial 108 bacterias mL-1.