Inhibitory action of antibiotics on Kluyveromyces marxianus.

A bioassay containing Kluyveromyces marxianus in microtiter plates was used to determine the inhibitory action of 28 antibiotics (aminoglycosides, beta-lactams, macrolides, quinolones, tetracyclines and sulfonamides) against this yeast in whey. For this purpose, the dose-response curve for each antibiotic was constructed using 16 replicates of 12 different concentrations of the antibiotic. The plates were incubated at 40°C until the negative samples exhibited their indicator (5-7h). Subsequently, the absorbances of the yeast cells in each plate were measured by the turbidimetric method (λ=600nm) and the logistic regression model was applied. The concentrations causing 10% (IC10) and 50% (IC50) of growth inhibition of the yeast were calculated. The results allowed to conclude that whey contaminated with cephalosporins, quinolones and tetracyclines at levels close to the Maximum Residue Limits inhibits the growth of K. marxianus. Therefore, previous inactivation treatments should be implemented in order to re-use this contaminated whey by fermentation with K. marxianus.

Toxicity of fluoroquinolones on the cladoceran Daphnia magna.

This study evaluates the acute and chronic toxicological effects of six fluoroquinolones on the mortality and growth of Daphnia magna. The NOECs calculated with the multivariate Probit regression model for the chronic study were 56 µg/L ciprofloxacin, 63 µg/L enrofloxacin, 78 µg/L levofloxacin, 85 µg/L marbofloxacin, 69 µg/L norfloxacin, and 141 µg/L ofloxacin. The risk quotients were determined using the measure environmental concentrations reported in water sources from different countries. The risks were low and moderate in water samples from rivers and lakes, although concentrations of ciprofloxacin, norfloxacin, and ofloxacin reported in some countries can cause toxicological damage to D. magna. In addition, urban wastewater and hospital wastewater samples constitute a threat to D. magna (high and moderate risks), requiring the treatment of these wastewater. PRACTITIONER POINTS: The NOECs calculated with the multivariate Probit model for the six fluoroquinolonas are between 56 µg/L ciprofloxacin and 141 µg/L ofloxacin. The levels of ciprofloxacin, norfloxacin, and ofloxacin in urban wastewater and hospital wastewater produce moderate and high risks for D. magna. Water and river samples from some countries containing ciprofloxacin, norlfoxacin, and ofloxacin present high risks for D. magna.

Effect of thermal treatment of whey contaminated with antibiotics on the growth of Kluyveromyces marxianus.

The objective of the studies reported in this research communication was to investigate the use of whey contaminated with antibiotics such as cephalosporins, quinolones and tetracyclines as a nutrient medium for the growth of Kluyveromyces marxianus with particular attention to the effect of thermal treatment used to overcome the inhibitory effects of antibiotic concentrations close to the Maximum Residue Limits. The heat treatments at 120 °C for 40 min, 120 °C for 83 min, and 120 °C for 91 min caused total inactivation of cephalosporins, tetracyclines and quinolone residues in whey respectively.

Coagulación optimizada: influencia en la eliminación de enteroparásitos

Los objetivos del trabajo fueron evaluar modificaciones del pH en la etapa de coagulación con polihidroxicloruro de aluminio, a fin de optimizar la remoción de materia orgánica y comprobar si estas modificaciones afectan la eliminación de enteroparasitos. Se trabajo con equipos de laboratorio para ensayos de coagulación. Para el recuento de enteroparasitos, se aplicaron métodos con antivuerpos monicionales por inmunofluorescencia

Coagulación optimizada: influencia en la eliminación de enteroparásitos

Los objetivos del trabajo fueron evaluar modificaciones del pH en la etapa de coagulación con polihidroxicloruro de aluminio, a fin de optimizar la remoción de materia orgánica y comprobar si estas modificaciones afectan la eliminación de enteroparasitos. Se trabajo con equipos de laboratorio para ensayos de coagulación. Para el recuento de enteroparasitos, se aplicaron métodos con antivuerpos monicionales por inmunofluorescencia