story to find out more.
bacteria in cattle were found to gain strength through their interaction with
protozoa such as the Ophryoscolex spp. pictured here. Click the image
for more information about it.
Microbes Strengthen Inside Animals'
Protozoa By Luis
Pons February 2, 2006
In an animal research "first," disease-causing bacteria have been
found to gain strength from interaction with single-celled organisms called
protozoa that are naturally present inside animals. This finding suggests that
the protozoa in animals' digestive tracts may be a place where dangerous
bacteria can lurk and develop.
In studies at the Agricultural Research Service (ARS)
Animal Disease Center (NADC) in Ames, Iowa, veterinary medical officer
Carlson and microbiologist
Rasmussen discovered that an antibiotic-resistant strain of
Salmonella becomes especially virulent when tucked inside protozoa in
the rumen, or first stomach, of cattle.
Until now, protozoa had never been thought of as reservoirs of disease
in animals, according to Rasmussen.
Microbiologists Mark Rasmussen and Sharon Franklin examine a
culture of rumen protozoa. Click the image for more information about
The researchers set out to study the relationship between rumen
protozoa and Salmonella's virulence and resistance to antibiotics. They
focused on an S. enterica strain named DT104 that's a foodborne pathogen
believed to be more virulent than its antibiotic-sensitive counterparts.
In animals, salmonellosis is usually a diarrheal disease that the
animals recover from without requiring antimicrobial therapy. But antibiotics
are needed when severe diarrhea or systemic infections occur. Unfortunately,
many Salmonella strains have become resistant to many antibiotics,
according to Carlson.
The strengthening of disease-causing bacteria as they occupy protozoa
is a process that's been seen with free-living protozoa in places such as
water-cooling towers and ponds, according to Rasmussen. This strengthening
process was discovered when it was linked to an infamous and deadly 1976
outbreak of Legionnaires' disease. But the recent study marks the first time
the process has been seen inside an animal, Rasmussen added.
Carlson and Rasmussen also found a way to combat DT104 by using a
cleansing process, called "defaunation," which rids the rumen of protozoa.
Postdoctoral molecular biologist Zoe McCuddin and microbiologist
Sharon Franklin assisted with this study. All of the researchers in this study
work in NADC's
Food Safety and Enteric Diseases Research Unit.
about this research in the February 2006 issue of Agricultural Research
ARS is the U.S. Department of
Agriculture's chief scientific research agency.