RESUMEN

Bacterial indicators and bacteriophages suggested as potential indicators of water quality were determined by public laboratories in water from springs, household water wells, and rural and metropolitan water supplies in north-eastern Spain. Indicator bacteria were detected more frequently than bacteriophages in springs, household water wells and rural water supplies. In contrast, positive bacteriophage detections were more numerous than those of bacteria in metropolitan water supplies. Most of the metropolitan water supply samples containing indicators had concentrations of chlorine below 0.1 mg l(-1), their indicator loads resembling more closely those of rural water supplies than any other samples taken from metropolitan water supplies. The number of samples from metropolitan water supplies containing more than 0.1 mg l(-1) of chlorine that contained phages clearly outnumbered those containing indicator bacteria. Some association was observed between rainfall and the presence of indicators. Sediments from service reservoirs and water from dead ends in the distribution network of one of the metropolitan water supplies were also tested. Bacterial indicators and phages were detected in a higher percentage than in samples of tap water from the same network. Additionally, indicator bacteria were detected more frequently than bacteriophages in sediments of service reservoirs and water from dead end samples. We conclude that naturally occurring indicator bacteria and bacteriophages respond differently to chlorination and behave differently in drinking water distribution networks. Moreover, this study has shown that testing for the three groups of phages in routine laboratories is easy to implement and feasible without the requirement for additional material resources for the laboratories.

Asunto(s)

Bacteriófagos/aislamiento & purificación , Monitoreo del Ambiente/métodos , Microbiología del Agua , Abastecimiento de Agua/análisis , Abastecimiento de Agua/normas , Cloro/administración & dosificación , Enterobacteriaceae/aislamiento & purificación , Enterococcus/aislamiento & purificación , Escherichia coli/aislamiento & purificación , Heces/microbiología , Humanos , Lluvia , Medición de Riesgo/métodos , Salud Rural , España , Salud Urbana , Purificación del Agua/métodos

RESUMEN

The bacteriophage elution procedure described further after adsorption to acetate-nitrate cellulose membrane filters allows better recovery of phages concentrated from 1l of water than elution procedures used previously. The improvement is due to the combined effect of the eluent (3% (w/v) beef extract, 3% (v/v) Tween 80, 0.5M NaCl, pH 9.0) and the application of ultrasound instead of agitation or swirling. Average recovery of somatic coliphages, 82 +/- 7%, was the greatest, and that of phages infecting Bacteroides fragilis, 56 +/- 8%, the lowest, with intermediate values for F-specific and F-specific RNA bacteriophages. Thus, the method allowed recovery of over 56% for all the phages suggested as surrogate indicators. The method was then validated according to an International Standardisation Organisation validation standard procedure and implemented in routine laboratories, which obtained reproducible results.

Asunto(s)

Bacteriófagos/aislamiento & purificación , Microbiología del Agua , Bacteriófagos/clasificación , Colifagos/aislamiento & purificación , Indicadores y Reactivos , Soluciones , Abastecimiento de Agua

RESUMEN

OBJECTIVE: To assess restriction endonuclease analysis (REA) of chromosomal DNA using SalI enzyme, low-concentration (0.4%) agarose gels and digitalized data management of the REA patterns obtained for the typing of clinical Pseudomonas aeruginosa isolates. METHODS: A group of 67 clinical unrelated isolates from 10 Spanish hospitals was used to study the discriminatory power, reproducibility and typeability of REA typing. RESULTS: A SalI REA pattern consisted of a variety (1--10) of restriction bands in the range between 12.2 and 48.5 kb and an unresolvable smear of low-molecular-weight bands. Forty different SalI REA patterns with an index of discrimination of 0.979 were obtained. Low typeability (91.04%) was the major limitation of REA typing. Analysis of blinded subcultures of eight Pseudomonas aeruginosa strains showed the reproducibility of REA typing to be 87.5%. Combined phenotypic typing (O-serotyping and phage typing) performed on the same group of strains showed comparable discrimination but much lower reproducibility. Isolates selected from five clusters of nosocomial infections in hospitals in the UK were typed by REA typing, and the results show high agreement when compared with conventional phenotypic typing methods in distinguishing between strains. CONCLUSIONS: These data underline the usefulness of REA typing enhanced with digitalized data management for the epidemiologic subtyping of clinical Pseudomonas aeruginosa isolates.

RESUMEN

The efficiency of semisolid Rappaport medium, brilliant green agar, and bismuth sulfite agar was compared for the recovery of Salmonella from 104 naturally contaminated meat products that had been pre-enriched and subsequently enriched in Rappaport-Vassiliadis broth, Müller-Kauffmann tetrathionate broth, and selenite-F broth. The semisolid Rappaport incubated at 35°C was the most sensitive of the plating media (p<0.01), detecting 90.2% of the 41 samples that were positive with any medium. Incubation of this medium at 43°C increased the specificity to 100%, but clearly lowered sensitivity compared to incubation at 35°C. The best sensitivity-specificity ratio of all the plating media used was obtained with the semisolid Rappaport incubated at 35°C. Its use gave an increase of 36.6% in the number of positive samples, with it also having a bias toward the isolation of the enteritidis serotype of Salmonella .