Andrés Chordi

Assessment of toxicity of river water and effluents by the bioluminescence assay using Photobacterium phosphoreum

Abstract The toxicity bioassay employing Photobacterium phosphoreum (LUMISTOX system) was used to evaluate the evolution of the quality of the River Tormes water during its passage through the city of Salamanca. To do so the toxicity of all the discharges into the river Tormes (22 total) were studied in the stretch in question, together with the impact of such discharges on the river course. Since pollution at low concentrations or the toxicity due to compounds that are strongly diluted in a fast flowing river may go undetected by the system, a technique of organic microcontaminant concentration using XAD-2 resins was used to detect different degrees of toxicity along the stretch studied. To a greater or lesser extent, all the discharges analyzed proved to be toxic for the photobacteria; the impact to the river caused by each was found to be a function of its EC50 and flow rate (Equitox/m 3 ). The toxicity of the water of the river increases (the inhibition of luminescence (%H15), the dilution factor that inhibits luminescence by 20% (G120) and the concentration values leading to a 50% decrease in the emission of light (EC50) for an incubation time of 15 min, increase) as the river receives the different discharges, from the first sample (before the discharges studied), where the water concentrate has a low effective concentration 50 value (EC50 = 1.3) until the last sample (after the discharges studied), where the effective concentration 50 value is maximum (EC50 = 2.9).

Effect of different factors on the die-off of fecal bacteria in a stabilization pond purification plant

A study was made of the effect of aeration on the die-off of different bacterial indicators of fecal waste at the wastewater lagoon purification plant of La Velles (Salamanca, Spain). In situ, the efficacy of the purification system, when the lagoons of the plant were partially aerated, rose from 92, 91, 95 and 17% in the die-off of total coliforms, fecal coliforms, fecal streptococci and sulfite-reducing clostridia to 99, 99, 97 and 53%, respectively. In order to study the effects of the microbial load on the die-off of fecal coliform bacteria and fecal streptococci, in vitro experiments were conducted. The results show that the reduction in the bacterial flora of the wastewater due to different treatments involved a proportional reduction in the die-off of fecal bacteria.

Characterization of smooth Brucella lipopolysaccharides and polysaccharides by monoclonal antibodies

Two mouse monoclonal antibodies (mAb) generated to the M antigen of Brucella melitensis 16M were analysed. Binding profiles of both monoclonals were established by a competitive enzyme-linked immunosorbent assay using chemically defined lipopolysaccharides, O polysaccharides and native hapten polysaccharides from B. melitensis 16M, B. abortus 544 and Yersinia enterocolitica O:9. Using this assay, significant differences in the reactivity of both antibodies were found with A and M antigens from Brucella spp. and the O polysaccharide from Y. enterocolitica O:9. These findings are consistent with the simultaneous expression of A and M epitopes on the lipopolysaccharide of all smooth Brucella strains. Quantitatively similar inhibitory powers were established for the native hapten and O polysaccharide from B. melitensis 16M. However, different behaviour was observed between both antigenic preparations obtained from B. abortus 544. The use of lipopolysaccharide-M-specific mAb in different serological tests instead of polyclonal antisera may be of great practical use for minimizing the risk of the appearance of cross-serological reactions between smooth Brucella strains and Y. enterocolitica O:9.

Influence of pH on the elimination of fecal coliform bacteria in waste stabilization ponds

From the results of in vitro studies carried out on wastewater from a stabilization pond it can be concluded that pH values close to 9, as a single factor, do not play any essential role in the die-off of fecal coliform bacteria. The percentage of elmination that occurs in pond water inoculated with 1.1×1010 cells of E. coli mL−1 where the pH is maintained at 8.2 (original pH) is 99.997%, a much greater reduction than that observed (94.1%) in distilled water inoculated with the same concentration of E. coli and where pH is increased up to 9.

Analysis of the immune response to Yersinia enterocolitica serotype-O:9-released proteins by immunoblot and ELISA

The immune response towards the released Yersinia enterocolitica outer membrane proteins (Yop) was analysed by immunoblotting and ELISA using a rabbit experimental model. Rabbits orogastrically or intravenously infected with the virulent (plasmid-bearing) Y. enterocolitica O:9 W836 strain developed a significant response by (IgG) antibodies to the released proteins having molecular weights of 51 (YopH) and 41 (LcrV) kDa, respectively. However, only in animals infected via the orogastric route were specific antibodies of the IgG class found against plasmid-encoded polypeptides of 35 (YopN) and 20 (YopQ) kDa. These results suggest that the expression of Yop in vivo may be conditioned by the route of infection used. Using ELISA, a significant response by IgG-class antibodies to YopH protein was evident in the sera from rabbits both orogastrically and intravenously infected with the virulent (pYV+) Y. enterocolitica O:9 W836 strain. By contrast, no specific antibodies to this antigen were detected in sera of rabbit infected with an avirulent (plasmid-cured) derivative (pYV-) strain. Accordingly, this protein could be very useful as an antigen in ELISA for serological diagnosis of infections caused by enteropathogenic strains of Yersinia spp.