ResumenLa calidad del agua de consumo es una de las preocupaciones más grandes a las que se enfrentan los entes de salud. En Costa Rica, a pesar de la buena calidad de las fuentes de agua y del agua de consumo, se siguen registrando numerosos casos de diarrea anualmente. En este estudio se realizó un análisis de indicadores de contaminación virales y bacterianos, en dos comunidades del Valle Central con acueducto propio. Se analizaron en total 24 muestras de agua por cada comunidad, durante un año, 12 en la fuente de agua y 12 en el agua tratada. La frecuencia de diarreas en cada comunidad fue comparada con la calidad microbiológica del agua consumida, encontrándose ausencia de indicadores bacterianos en muestras de agua tratada, mientras que la presencia de indicadores virales en el agua de consumo (con cloro residual) se relaciona con un incremento en el número de casos de diarreas, adicionalmente se analizó el comportamiento de las diarreas de acuerdo a la precipitación promedio con el fin de observar posibles patrones de estacionalidad. Estos hallazgos respaldan la necesidad de ampliar el monitoreo de calidad microbiológica del agua con otro tipo de indicadores de contaminación que correlacionen mejor con otros agentes patógenos de transmisión hídrica, principalmente en época seca, periodo en que se observan más casos de diarrea.

AbstractThe quality of potable water is one of the most important issues of public health. In Costa Rica, in spite of having good sources of water and good quality of water for consumption, there continues to be a significant number of diarrhea cases annually. In this investigation, viral and bacterial analyses of indicators of contamination were conducted in two rural communities with their own aqueducts in the Central Valley of Costa Rica. Twenty-four samples were taken from each community during the year; 12 from the water sources and 12 from the treated waters. The frequency of diarrhea in each community was compared to the microbiological quality of the water being consumed, noting an absence of bacterial indicators in samples of treated water, while the presence of viral indicators in the water (with residual chlorine) were associated with an incremental increase in the number of cases of diarrhea. The analysis also included measurements of average monthly rainfall with the aim of observing possible associations between seasonal conditions and the incidence of diarrhea cases. These findings indicate the need to increase the monitoring of the microbiological quality of the water with other types of indicators of contamination that correlate better with other pathogens transmitted by water, especially in the dry seasons when a greater number of cases of diarrhea are observed.

A Multiplex Polymerase Chain Reaction (PCR) assay to be used as an alternative to the conventional culture method in detecting Shigella and enteroinvasive Escherichia coli (EIEC) virulence genes ipaH and ial in lettuce was developed. Efficacy and rapidity of the molecular method were determined as compared to the conventional culture. Lettuce samples were inoculated with different Shigella flexneri concentrations (from 10 CFU/ml to 10(7) CFU/ml). DNA was extracted directly from lettuce after inoculation (direct-PCR) and after an enrichment step (enrichment PCR). Multiplex PCR detection limit was 10(4) CFU/ml, diagnostic sensitivity and specificity were 100% accurate. An internal amplification control (IAC) of 100 bp was used in order to avoid false negative results. This method produced results in 1 to 2 days while the conventional culture method required 5 to 6 days. Also, the culture method detection limit was 10(6) CFU/ml, diagnostic sensitivity was 53% and diagnostic specificity was 100%. In this study a Multiplex PCR method for detection of virulence genes in Shigella and EIEC was shown to be effective in terms of diagnostic sensitivity, detection limit and amount of time as compared to Shigella conventional culture.