Submitted to: Journal of Microbiological Methods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 20, 1998
Publication Date: N/A
Interpretive Summary: Cryptosporidium parvum is a waterborne pathogen infectious for livestock and humans. It is the only species of Cryptosporidium infectious for humans. Because water samples from surface waters, ground water, or post treatment potable water can contain oocysts of several species of Cryptosporidium it is important to differentiate C. parvum from other species and to determine if the oocysts are alive and infectious, or dead. An earlier report described a signature lipid useful in identifying live C. parvum oocysts. The present study has demonstrated that those earlier findings were based on an artifact and therefore cannot be used for detection of C. parvum oocysts.
Heating or freezing leads to loss in infectivity of oocysts of Cryptosporidium parvum towards neonatal BALB/c mice and is reflected in the profile of the polar lipid fatty acids (PLFA). Upon loss of infectivity, the polar lipid to neutral lipid fatty acid ratio decreased and the relative proportions of 18:1 omega 9 also decreased, proportions 18:2 omega a6 and 20:5 omega 6 increased, while the proportions of 16:0 remained constant with freezing. During these investigations, a novel fatty acid, 10-OH 18:0, was discovered in the glycolipid fraction. The identification of a fatty acid unique to species of Cryptosporidium was thought to provide a specific biomarker for this organism. Cryptosporidium also demonstrated fluctuations in absolute quantities of 10-OH 18:0 with events that lead to loss of infectivity. This led to the presumed correlation of this biomarker with infectious Cryptosporidium. The 10-OH 18:0 was putatively localized at the sn-2 position of phosphatidylethanolamine. High performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI/MS) revealed that the 10-OH 18:0 existed principally in the free fatty acid form. Herein, we establish that the free fatty acids 10-OH 18:0 was, in actuality, an artifact of the procedures for sample preparation.