ON FOOD PARASITOLOGY
Ming-Qi Deng, and Dean O.
Our research on food
parasitology is focused on protozoan Cryptosporidium parvum and Giardia lamblia.
C. parvum, a coccidean species, is
the leading waterborne pathogen with worldwide distribution. It causes self-limited
watery diarrhea in immunocompetent persons and persistent, life-threatening
diseases in immunocompromised invividuals, since there is no effective treatment.
Cryptosporidiosis is considered to be a factor contributing to death in AIDS
patients. The tranmissive stage (oocyst) of this organism is exceptionally resistant
to most commercial disinfectants and can transmit among many animal species
and between animals and humans, thus capable of causing large waterbrone outbreaks
via contaminated drinking water supply. The 1993 Milwaukee outbreak, in which
more than 403,000 persons were infected and about 100 persons eventually died,
was the largest waterborne outbreak ever recorded in the history of U.S.A..
Contaminated food stuffs, such as raw milk, unpasteurized apple juice, and salads,
have been associated with cryptosporidial infection. Person-to-person transmission
has been documented. Other transmission routes have also been suggested. You
can read more about this organism here.
G. lamblia (syn. G. duodenalis, G.
intstinalis), a flagellate protozoa, was the number one
cause of waterborne diseases in the U.S before the occurrence of
the 1993 Milwaukee outbreak. Many epidemiological aspects of
giardiasis are similar to those of cryptosporidiosis.
Fortunately, the disease is less severe and it is treatable.
In the past years, our research on C. parvum and G.
lamblia covered several differentaspects, such as
concentration and separation of the organisms from environmental
and food samples, detection of the organisms using (in-)direct
immunofluorescence assays and polymerase chain reaction
techniques, in vitro cultivation and viability determination,
immunomagnetic separation, genetic fingerprinting of iolates of
various origins, and inactivation studies.
Achievements to date
from our work
Developed immunomagnetic separation systems
for concentrating C. parvum oocysts and G. lamblia cysts from environmental and food samples;
Developed PCR methods for detecting C. parvum oocysts
and G. lamblia cysts from environmental samples and PCR-
based DNA fingerprinting methods (RAPD, PCR-RAPD) in
differentiating isolates from various sources;
Established a semi-quantitative in vitro C. parvum infectivity assay for detection of infectious oocysts and in
oocyst inactivation/survival studies;
Modeled C. parvum oocyst transmission from food contact
surfaces into dairy products and oocyst survival, such
information will assist in developing hazard analysis and
critical control point (HACCP) systems;
Conducted research on inactivation of C. parvum by
various modes, as the most recent one being biodegradation of
oocysts by selectd bacterial strains.
Publications to date
from our work
Deng, M. Q., D. O. Cliver, and T. W.
Mariam. 1997. Immunomagnetic capture PCR to detect viable
Cryptosporidium parvum oocysts from environmental
samples. Applied and Environmental Microbiology 63(8): 3134-3138.
Deng, M. Q., and D. O. Cliver. 1998. Cryptosporidium parvum
development in the BS-C-1 cell line. Journal of
Parasitology 84(1): 8-15.
Deng, M. Q., and D. O. Cliver. 1998. Differentiation of Cryptosporidium
parvum isolates by a simplified randomly amplified
polymorphic DNA technique. Applied and Environmental Microbiology
Deng, M. Q., and D. O. Cliver. 1999. Cryptosporidium parvum studies with dairy products. International Journal of Food
Microbiology 46(2): 113-121.
Deng, M. Q., and D. O. Cliver. 1999. Improved immunofluorescence
assay for detection of Giardia and
Cryptosporidium from asymptomatic adult cervine animals.
Parasitology Research 85(8): 733-736.
Deng, M. Q., and D. O. Cliver. 1999. Rapid DNA extraction methods
and new primers for randomly amplified
polymorphic DNA analysis of Giardia duodenalis. Journal of
Microbiological Methods 37(2): 193-200.
Deng, M. Q., and D. O. Cliver. 1999. Comparative detection of Cryptosporidium
parvum oocysts from apple cider. In press (International
Journal of Food Microbiology).
Deng, M. Q., K. M. Lam, and D. O. Cliver. 1999. Immunomagnetic
separation of Cryptosporidium parvum oocysts using MACS
MicroBeads and high gradient separation columns. In press
(Journal of Microbiological Methods).
Deng, M. Q., R. P. Peterson, and D. O. Cliver. 1999. First
findings of Cryptosporidium and Giardia in
California sea lion (Zalophus californianus). Manuscript
submitted (Journal of Microbiology)
Others are in preparation.
to Current Research