FIELD TESTING OF COLIPHAGE METHODS FOR SCREENING GROUND WATER FOR FECAL CONTAMINATION

摘要

Two coliphage methodologies, Method 1601(enrichment method) and Method 1602 (single agar layer enumeration method were field tested for ground water screening for indicators of fecal contamination. The sampling volumes for Method 1601 and 1602 are 1000 ml and 100 ml respectively. Ground water samples used for the study were obtained from 17 shallow public water supply wells located within vulnerable aquifers along the US-Mexico border near El Paso, Texas. The collected samples were screened for the presence of somatic and male specific coliphages and for the presence of bacterial indicators, E.coli and enterococci. Bacteriophages were detected in 8 of the 17 samples, (47%) by both methods combined. Six of the 17 samples (35%) were positive for coliphages by Method 1601 and only two of the 17 samples (12%) were positive by Method 1602. The concentration of phages detected were very low not exceeding 1 PFU/100 ml. Bacterial indicators, enterococci were detected in only 2 samples while E.coli was detected in one sample. A co-occurrence of both bacterial indicators was not detected in the same wells. A co-occurrence of both the viral indicators and the bacterial indicators was not detected in the same wells except one well. Method 1601, the phage enrichment assay, is easy to use and the results obtained suggest that it is a promising method for recovering coliphages from ground water sources. Method 1602, the single agar enumeration method can only screen 100 ml of sample as compared to Method 1601 which can screen 1000 ml of sample. Overall, Method 1601 appears to be suitable for routine screening of ground water samples for the presence/absence of coliphages.