Hospital effluent constitutes a source of vancomycin-resistant Enterococci / El efluente hospitalario como fuente de enterococos vancomicina resistentes

Objectives: Enterococci are intrinsically resistant to many commonly used antimicrobial agents. They are able to acquire resistance with relative ease and can spread these genes to other species. Enterococci resistant to antibiotics are associated with the use of these in clinical practice and also the spread of resistant clones in the world. The aim of this work was to compare the characteristics of the strains of vancomycin-resistant enterococci (VRE) isolated from municipal wastewater and hospital effluent. Methods: Samples were obtained from the effluent of the Hospital Universitario José de San Martín (Buenos Aires) and the municipal wastewater of the city of Buenos Aires. Results: The bacterial counts of VRE were greater in the hospital effluent, with an odds ratio of 36.4 (95% CI: 26.0-50.8; p<0.0001). The VRE isolated were mainly identified as E. faecium. The results indicate a high prevalence of enterococci resistant to the antibiotics tested. Conclusion: We may conclude that the effluents of hospitals constitute a source of VRE showing multiple resistance to antibiotics

Objetivos: Las especies de enterococos son intrínsecamente resistentes a varios antibióticos, adquieren resistencia con relativa facilidad, y difunden estos genes de resistencia a otras especies. La resistencia a los antibióticos en enterococos está asociada al uso de los mismos en la clínica médica y también a la diseminación de clones resistentes en el mundo. El objetivo de este trabajo fue comparar las características de las cepas de enterococos resistentes a vancomicina (ERV) aisladas en efluentes hospitalarios y aguas residuales urbanas. Métodos: Se obtuvieron muestras de los efluentes del Hospital Universitario José de San Martín (Buenos Aires) y muestras de aguas residuales urbanas de la ciudad de Buenos Aires. Resultados: Los recuentos de ERV fueron mayores en los efluentes hospitalarios, siendo la odds ratio 36.4 (IC95%: 26.0-50.8; p<0.0001). Los ERV aislados se identificaron principalmente como E. faecium. Los resultados indicaron una alta prevalencia de enterococos resistentes al resto de los antibióticos ensayados. Conclusión: Podemos concluir que los efluentes de los centros hospitalarios constituyen una fuente de enterococos de resistencia múltiple a antibióticos

Prevalence of CTX-M-Type extended-spectrum ß-lactamases in Escherichia coli strains isolated in poultry farms.

The aim of the study was to detect the prevalence of CTX-M-type extended-spectrum ß-lactamases (ESBL) in Escherichia coli strains isolated in healthy chickens at poultry farms in Tenerife, Spain. From November 2012 to February 2013, 260 live chickens were screened. Samples were cultured in chromogenic media. Suspect strains were identified by Vitek 2 system and ESBL production was confirmed by the double-disk synergy test. Pulsed-field gel electrophoresis (PFGE) was performed with XbaI (Promega, Madison, WI) to ESBL-E. coli isolates. The presence of CTX-M-type was detected by real-time polymerase chain reaction. Of 260 rectal swabs, 237 (91.1%) were ESBL-E. coli, 196 (75.38%) strains were characterized by PFGE, and CTX-M-type was detected in 116 (59.1%) of these strains. With respect to the susceptibility patterns of E. coli blaCTX-M strains, 7.8% showed resistance to more than two non-ß-lactam antibiotics. In our area, the prevalence of CTX-M-type in E. coli isolated in chicken was even higher than those found in other countries. The impact of food animals as a possible reservoir for ESBL-E. coli, especially CTX-M-type ESBL, and the dissemination of such strains into the food production chain need to be assessed.

Sustainable and effective control of trihalomethanes in the breakpoint chlorination of wastewater effluents.

The control of trihalomethanes (THMs) in waters subjected to chlorination is essential for protecting public health. However, the necessary means are not always available, especially in developing countries and regions. Under circumstances of scarce resources, one can utilize various means available for the control of THMs: a simple and affordable analytical method for testing of THMs, the study of the parameters tested routinely that could be used as indicators and the dose of chlorine used for the chlorination process. The objective of this work was to study the potential formation of THMs in wastewater effluents using a simple method of detection and various doses of chlorine in relation to the breakpoint and to validate some commonly determined parameters as indicators of THM formation. THM concentrations were measured using a simple spectrophotometric method based on the Fujiwara reaction. To determine the chlorine demand, a super-chlorination was performed and free and residual chlorine was measured; the mean value of chlorine demand was 166.6 mgCl2/L. The chlorination with concentrations well below the chlorine demand produces a significant reduction in microbial content. With regard to the formation of THMs the higher the dose of chlorine added, the higher the concentration of THMs. In relation to commonly determined parameters our data only provide a logarithmic linear regression between THMs and ammonium. According to our results, the breakpoint must be determined for the chlorination of sewage and their effluents, and chlorination should be performed with concentrations of chlorine at approximately 1/3 of the demand.

Isolation of Salmonella serotypes in wastewater and effluent: Effect of treatment and potential risk.

The characteristics of strains of Salmonella isolated in wastewater were compared before and after treatment with activated sludge (conventional sewage treatment). Of the 21 strains studied, 11 came from raw wastewater and 10 from treated water. Our objective was to determine if the treatment affected all serotypes to the same extent, and whether it had an effect on the plasmidic composition and selection of resistances to antibiotics and disinfectants. The serotypes of all strains were identified, and we also determined the sensitivity to antibiotics, the minimal bactericidal concentration of three disinfectants (peracetic acid, glutaraldehyde, and sodium hypochlorite), and plasmidic content. Results showed no significant differences in the isolated strains before versus after treatment, thus indicating that the conventional treatment of sewage does not constitute a risk factor in the selection of Salmonella strains with a greater pathogenic potential.

Evaluating trihalomethane content in drinking water on the basis of common monitoring parameters: regression models.

The presence of trihalomethanes (THMs) in potable-water sources is an issue of great interest because of the negative impact THMs have on human health. The objective of this study was to correlate the presence of trihalomethanes with more routinely monitored parameters of water quality, in order to facilitate THM control. Water samples taken at various stages of treatment from a water treatment plant were analyzed for the presence of trihalomethanes with the Fujiwara method. The data collected from these determinations were compared with the values obtained for free-residual-chlorine and combined-residual-chlorine levels as well as standard physico-chemical and microbiological indicators such as chemical oxygen demand (by the KMnO4 method), total chlorophyll, conductivity, pH, alkalinity, turbidity, chlorides, sulfates, nitrates, nitrites, phosphates, ammonia, calcium, magnesium, heterotrophic bacteria count, Pseudomonas spp., total and fecal coliforms, and fecal streptococci. The data from these determinations were compiled, and statistical analysis was performed to determine which variables correlate best with the presence and quantity of trihalomethanes in the samples. Levels of THMs in water seem to correlate directly with levels of combined residual chlorine and nitrates, and inversely with the level of free residual chlorine. Statistical analysis with multiple linear regression was conducted to determine the best-fitting models. The models chosen incorporate between two and four independent variables and include chemical oxygen demand, nitrites, and ammonia. These indicators, which are commonly determined during the water treatment process, demonstrate the strongest correlation with the levels of trihalomethanes in water and offer great utility as an accessible method for THM detection and control.