Recent studies have shown that Cryptosporidium is very susceptible to ultraviolet (UV)
light disinfection, with doses as low as = 25 mJ cm-2 resulting in approximately 3 log10 reduction
in infectivity. Mouse or in vitro cell culture infectivity models have most frequently been used to
measure oocyst inactivation. However, these methods are costly, labor-intensive, and require
several days to weeks to perform. These methods are also impractical for the routine evaluation
of typical full-scale application UV doses in the 40 to 60 mJ cm-2 range. Prior to this work, there
have been no methods developed for the direct quantitation of UV-induced damage to
Cryptosporidium oocysts. In this study, a bench-scale monochromatic 254 nm low-pressure UV system was
used to deliver 0 to 1000 mJ cm-2 doses to C. parvum oocysts suspended in reagent water.
Quantitative sequence detection (QSD), a real-time quantitative polymerase chain reaction
(PCR) method, was used to directly quantify UV-induced damage in low numbers (~200) of
oocysts. QSD allows the comparison of nucleic acid samples based on their amplification
kinetics (i.e. "amplifiability"), and it was hypothesized that UV-induced damage to oocysts
would quantitatively affect DNA amplification. QSD amplification at 10, 20, 40, 60 and 100 mJ
cm-2 doses could readily be distinguished from each other (P = 0.01). Average standard
deviation of all replicates for all UV doses was 16.1%. DNA of oocysts exposed to 1000 mJ cm-
2 was not amplifiable. The developed method could be useful in assessing UV reactor
performance and for evaluating the DNA repair potential of Cryptosporidium.
Includes 8 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 260 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 5 |
| Published : | 11/01/2002 |
