Georgia Tech's Research Horizons magazine - Fall 1999
A New Bacterium
 In 1986, a Georgia Tech biology professor in collaboration with scientists
at the Centers for Disease Control (CDC) confirmed and reported the first
cases of human gastrointestinal illness associated with a bacterium they
had first identified only two years earlier in pigs with gastrointestinal
illness.
The bacterium, Campylobacter hyointestinalis, is a distinct species in
the genus Campylobacter. One other species in this genus (C. jejuni) is
responsible for an estimated two million cases of diarrheal illness in people
in the United States every year. C. hyointestinalis is one of the least
common species of the genus, but it caused severe illness in the four patients
in which it was reported in the Journal of Clinical Microbiology in 1987.
Researchers, led by Georgia Tech's Dr. Paul Edmonds, isolated the bacterium
from the patients' stool specimens. They used the DNA-DNA hybridization
technique to genetically confirm the identification of the strains. The
technique, developed at the CDC, continues to be a state-of-the-art method
for identifying unknown strains of bacteria based on a high degree of matching
gene sequences in the DNA from samples examined.
The authors also reported that, like patients with illnesses caused by
other species in the Campylobacter genus, patients with C. hyointestinalis
infections responded well to treatment with the antibiotic erythromycin.
The researchers noted that all four patients in this study could be considered
as having compromised health: One was an elderly woman who had recently
traveled in Egypt; two were homosexual men; and the fourth was an infant
who had been drinking raw milk and untreated well water.
Shortly after the study ended, the researchers received two additional
stool specimens containing C. hyointestinalis. These were from an elderly
man and a 3-year-old boy. Researchers suggested that further research needed
to confirm whether the bacterium is restricted to presumably compromised
patients or whether it can infect otherwise healthy people.
The researchers' findings were published in the April 1987 issue of the
Journal of Clinical Microbiology. Edmonds was the lead author. Since the
publication of the article, other researchers have reported at least six
more cases of human gastrointestinal disease associated with C. hyointestinalis.
At least one of those cases was in a patient whose immune system was compromised
by leukemia. The CDC does not compile statistics on disease related to this
bacterium.
Also, since publication of the Edmonds, et al. article, C. hyointestinalis
has been reported in cattle, sheep, mussels, oysters, Macaca nemestrina
monkeys and Moluccan rusa deer. A new subspecies has been identified in
pigs.
Another more recently developed hybridization technique for identifying
bacterial strains is based on 16S rRNA sequence analysis. But the technique
called polymerase chain reaction (PCR) is now the most efficient method
of detecting the presence of C. hyointestinalis in clinical specimens.
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