Treatment impact on the intestinal microbiota

PhD ceremony: Mr. R.F.J. Benus, 11.00 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Treatment impact on the intestinal microbiota

Promotor(s): prof. T.S. van der Werf, prof. J.E. Degener

Faculty: Medical Sciences

This thesis describes the effects of antibiotics and tube feeding on our protective intestinal microbiota. Antibiotics are administered to patients in the intensive care unit (ICU) through Selective Digestive Decontamination (SDD) to prevent infections by harmful intestinal bacteria. It was found that suppressing bacteria in the mouth and throat only, i.e., Selective Oropharyngeal Decontamination (SOD), may be as helpful. SDD and SOD were effective in reducing mortality. It was shown that SDD, unlike SOD, severely suppresses certain groups of beneficial bacteria, especially F. prausnitzii. These bacteria produce butyrate which is essential for a healthy intestinal mucosa. ICU patients not only receive antibiotics but also tube feeding. The effects of enteral feeding with or without dietary fiber on the intestinal microbiota were studied. The addition of certain dietary fibers showed a significant effect on these healthy bacteria. Another mechanism that was studied is the suppression of butyrate-producing bacteria. F. prausnitzii appears to be susceptible to many antibiotics. During SDD, a group of bacteria in the gut, enterococci, increases. These are usually relatively harmless, although among patients in the UMCG serious enterococcal infections appear to occur regularly, as evidenced by an exploratory study in which only the bloodstream infections were considered. There was no noticeable effect of the SDD research on the incidence of these infections.