Effect of 1-(1-naphthylmethyl)-piperazine on antimicrobial agent susceptibility in multidrug-resistant isogenic and veterinary Escherichia coli field strains

The objective of this study was to evaluate the interaction of the efflux pump inhibitor 1-(1-naphthylmethyl)-piperazine (NMP) when combined with different families of antimicrobial agents against isogenic strains and multidrug-resistant (MDR) Escherichia coli field strains isolated from animals. Laboratory isogenic strains of E. coli with different levels of expression of efflux pumps were used as quality controls. Ten MDR E. coli strains were collected from healthy animals in a cross-sectional study in four commercial dairy farms. The MICs of florfenicol, ciprofloxacin, tetracycline and ampicillin were determined by a serial microdilution method in Luria-Bertani broth in the presence or absence of NMP. NMP used with ampicillin exerted no effect on the isogenic or field strains. In most of the field MDR E. coli strains and in an acrAB-overexpressing (AG112) isogenic strain, the MICs of florfenicol, ciprofloxacin and tetracycline decreased at least fourfold when the antimicrobial was combined with the highest NMP concentrations. In the wild-type strain (AG100), there were no decreases of more than twice the MIC, whilst in strain AG100A, an efflux pump-deficient strain, the MIC did not change, regardless of the concentration of NMP used with these three antimicrobials. Thus, ampicillin was not affected by the efflux pump mechanism, whereas ciprofloxacin, tetracycline and florfenicol were shown to be substrates of efflux pumps, with a consequent significant reduction in MICs. Resistance could not be completely reversed in the E. coli field strains by NMP, probably because other resistance mechanisms were also present. However, in strain AG112, the MIC results demonstrated that NMP expressed an important synergistic activity with florfenicol. The reduction in florfenicol MIC value was sufficient to reverse antimicrobial resistance completely for AG112.Facultad de Ciencias VeterinariasFacultad de Ciencias Médica

Effect of 1-(1-naphthylmethyl)-piperazine on antimicrobial agent susceptibility in multidrug-resistant isogenic and veterinary Escherichia coli field strains

The objective of this study was to evaluate the interaction of the efflux pump inhibitor 1-(1-naphthylmethyl)-piperazine (NMP) when combined with different families of antimicrobial agents against isogenic strains and multidrug-resistant (MDR) Escherichia coli field strains isolated from animals. Laboratory isogenic strains of E. coli with different levels of expression of efflux pumps were used as quality controls. Ten MDR E. coli strains were collected from healthy animals in a cross-sectional study in four commercial dairy farms. The MICs of florfenicol, ciprofloxacin, tetracycline and ampicillin were determined by a serial microdilution method in Luria-Bertani broth in the presence or absence of NMP. NMP used with ampicillin exerted no effect on the isogenic or field strains. In most of the field MDR E. coli strains and in an acrAB-overexpressing (AG112) isogenic strain, the MICs of florfenicol, ciprofloxacin and tetracycline decreased at least fourfold when the antimicrobial was combined with the highest NMP concentrations. In the wild-type strain (AG100), there were no decreases of more than twice the MIC, whilst in strain AG100A, an efflux pump-deficient strain, the MIC did not change, regardless of the concentration of NMP used with these three antimicrobials. Thus, ampicillin was not affected by the efflux pump mechanism, whereas ciprofloxacin, tetracycline and florfenicol were shown to be substrates of efflux pumps, with a consequent significant reduction in MICs. Resistance could not be completely reversed in the E. coli field strains by NMP, probably because other resistance mechanisms were also present. However, in strain AG112, the MIC results demonstrated that NMP expressed an important synergistic activity with florfenicol. The reduction in florfenicol MIC value was sufficient to reverse antimicrobial resistance completely for AG112.Facultad de Ciencias VeterinariasFacultad de Ciencias Médica

Circadian rhythms of proliferation events in two mouse carcinomas

We studied the index of DNA synthesis (DNAs) of two cellular carcinomas: the hepatocellular ES12a and the mammary TN60 of mice, throughout one circadian cycle. In the results, we observed that both tumors have circadian rhythms (CRs), but the peaks of DNAs vary. Besides, the mean of DNAs along 24 h shows significative differences, the TN60 has higher values than the ES12a. These observed CR in the DNAs index in both carcinomas mean that, at least in partly, the proliferation of cancer cells can be regulated by endocrine factor as it normally occurs in ordinary cells. The big problem we can find for the chronopharmacology is that it is impossible to know in advance the rate of proliferation of each tumor.Fil: Garcia, Marcela. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Andrini, Laura Beatríz. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Martinez, Marina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Inda, Ana. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Palma, Maria Belen. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Miriuka, Santiago Gabriel. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Errecalde, Ana Lia. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentin

Characterization of Tn6238 with a New Allele of aac(6′)-Ib-cr

Here, we report that the genetic structure of Tn1331 remained conserved in Argentina from 1989 to 2013 (72 of 73 isolates), with the exception being the plasmid-borne Tn1331-like transposon Tn6238 containing a new aac(6′)-Ib-cr allele recovered from a colistin-resistant Klebsiella pneumoniae clinical isolate. A bioinformatic analysis of aac(6′)-Ib-like gene cassettes suggests that this new aac(6′)-Ib-cr allele emerged through mutation or homologous recombination in the Tn1331 genetic platform. Tn6238 is a novel platform for the dissemination of aminoglycoside and fluoroquinolone resistance determinants.Fil: Quiroga, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Orman, Betina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Errecalde, Laura. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos ; ArgentinaFil: Kaufman, Sara. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos ; ArgentinaFil: Centron, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; Argentin

Circadian rhythm of VEGF expression in the liver of hepatectomized tumor bearing mice

In this study we analyzed VEGF-C expression in regenerating liver (after partial hepactectomy) of ES2 hepatocellular carcinoma bearing mice, throughout one complete circadian cycle. The animals were sacrificed every 4 h throughout one complete circadian cycle from 26 to 50 h post-hepatectomy. Tumor samples were processed for immunohistochemistry. The expression of VEGF was assessed according to the percentage of immunoreactive cells in a total of 1000 cells (quantitative analysis). The results show that controls and tumor bearing mice have statistical differences at all analysed time points, but the maximun value of VEGF expression of treated animals is significantly higher (p < 0.01) than the control group. We can conclude that when a partial hepatectomy is made with the purpose of eradicating a hepatic tumor, the presence of possible metastasis could release factors related with cellular proliferation that could increase the possibilities of tumoral recidives.Facultad de Ciencias Médica

Variaciones en la síntesis de ADN en los hepatocitos de ratones hepatectomizados

La división celular es una propiedad fundamental de los organismos vivos y es el principal mecanismo de crecimiento de órganos y tejidos. Por otro lado, sabemos que la hepatectomía parcial altera las concentraciones de los factores de crecimiento que intervienen en la proliferación celular provocando una hiperplasia compensadora del hígado. Así mismo, uno de los parámetros estudiados para analizar los cambios que se producen durante la regeneración hepática, es a través de la evolución en la síntesis de ADN de los hepatocitos.Facultad de Ciencias Médica

Estudio de la actividad mitótica en hepatocitos de ratones durante la regeneración hepática

El crecimiento y desarrollo de los seres vivos dependen de la capacidad de multiplicación de sus células. Por otro lado, sabemos que tras una hepatectomía la rápida restauración del volumen y de la función hepática es una propiedad exclusiva del hígado. El objetivo del presente estudio preliminar, fue evaluar la actividad mitótica de los hepatocitos de ratones, en distintos puntos horarios luego de una hepatectomía parcial del 70%.Facultad de Ciencias Médica

Variaciones en la síntesis de ADN en los hepatocitos de ratones hepatectomizados

La división celular es una propiedad fundamental de los organismos vivos y es el principal mecanismo de crecimiento de órganos y tejidos. Por otro lado, sabemos que la hepatectomía parcial altera las concentraciones de los factores de crecimiento que intervienen en la proliferación celular provocando una hiperplasia compensadora del hígado. Así mismo, uno de los parámetros estudiados para analizar los cambios que se producen durante la regeneración hepática, es a través de la evolución en la síntesis de ADN de los hepatocitos.Facultad de Ciencias Médica

Circadian rhythm of VEGF expression in the liver of hepatectomized-tumor-bearing adult and young mice

We analyzed VEGF expression in regenerating liver (after partial hepatectomy) of tumor-bearing adult and young mice, throughout one complete circadian cycle. The animals were sacrificed every 4 h, from 26 to 46 h post-hepatectomy. Liver samples were processed for immunohistochemistry. The results showed circadian variation of VEGF expression in hepatectomized mice (control group) and hepatectomized-tumor-bearing mice. The maximum value of VEGF expression was found at 16:00/30 h of day/hour post-hepatectomy (HD/HPH) in tumor-bearing young mice, and at 20:00/34 HD/HPH in the controls. In adult mice the maximum values of VEGF expression were at 16:00/30 HD/HPH in tumor-bearing mice, and at 08:00/46 HD/ HPH in the controls. Young tumor-bearing mice showed significantly higher mean values than the controls. In conclusion, the presence of the tumor in the animals induces modifications in the intensity and the temporal distribution of the circadian curves of VEGF expression.Facultad de Ciencias Médica

Estudio de la actividad mitótica en hepatocitos de ratones durante la regeneración hepática

El crecimiento y desarrollo de los seres vivos dependen de la capacidad de multiplicación de sus células. Por otro lado, sabemos que tras una hepatectomía la rápida restauración del volumen y de la función hepática es una propiedad exclusiva del hígado. El objetivo del presente estudio preliminar, fue evaluar la actividad mitótica de los hepatocitos de ratones, en distintos puntos horarios luego de una hepatectomía parcial del 70%.Facultad de Ciencias Médica