Campylobacter is the most common cause of bacterial enteritis in developed countries. But unlike with other enteric pathogens, the mechanisms used by the organism to cause disease are still widely unknown, says bacteriologist Hilpi Rautelin.
“It has been known for a long time that the microbiota can protect a person from colonization by organisms that cause intestinal tract disease. However, very little is known about how human gut microbiota influences susceptibility to these organisms, and to Campylobacter in particular,” says Rautelin, a professor at Uppsala University and Uppsala University Hospital in Sweden. “We wanted to see if the composition of the human gut microbiota plays a role in susceptibility to Campylobacter infection.”
Reporting in mBio® this week, Rautelin and colleagues found that, indeed, the specific composition of bacterial species in a person’s gut may protect against or increase susceptibility to Campylobacter. In particular, elevated proportions of Bacteroides and Eschericia may predispose humans to Campylobacter infection. The team also found that Campylobacter infection can cause lasting changes to the composition of gut bacteria.
The scientists followed 24 workers at three poultry slaughterhouses in Sweden – an ideal environment to study the organism, Rautelin says. The risk of acquiring Campylobacter at a Swedish chicken slaughterhouse is high, especially during the summer peak in June to September, when approximately 25% to 40% of slaughtered chicken flocks are Campylobacter-positive.
They collected fecal samples from the workers once a month from June to September 2010, and again the following February. They cultured fecal samples for Campylobacter and used 16S amplicon sequencing to study the composition of the microbiota. While all participants tested negative for Campylobacter at the beginning of the study, seven became culture positive for the organism during the study. Only one of the Campylobacter-positive participants experienced symptoms of illness.
Those who became Campylobacter-positive had a significantly higher abundance of Bacteroides and Escherichia organisms than those who remained culture negative, suggesting that these bacterial species likely play an important role in colonization resistance. This group also had a significantly higher abundance of Phascolarctobacterium and Streptococcus species than those in the Campylobacter-negative group, which had an overrepresentation of Clostridiales, unclassified Lachnospiraceae, and Anaerovorax species.
The work supports previous studies in mouse models finding that Bacteroides and Escherichia have an important role for susceptibility to gut pathogens and Campylobacter in particular, Rautelin says.
Following the individuals’ fecal microbiota compositions over time, the researchers observed that the Campylobacter-negative individuals had small differences but those who tested positive for Campylobacter showed significant changes by the February sample. Researchers do not yet know the implications of these changes, Rautelin says.
Whether microbiota composition alone or together with an individual’s immune status also plays a significant role in the eradication of Campylobacter from the intestines remains to be studied, she says.