Antibiotics are effective against harmful bacteria in the body, but not only against these: Destroyed are not only pathogens (i.e. bacteria with disease-causing properties), but also bacteria which are useful, harmless, and occasionally very important for our health. Gut bacteria, in particular, are seriously affected during treatment with broad-spectrum antibiotics.
Recently, a group of researchers from the Berlin Max-Delbrück-Centre for Molecular Medicine (MDC) headed by Sofia Forslund, a biochemist, presented the results of a long-term study. Twelve healthy men received a four-day intervention with a cocktail of three broad-spectrum antibiotics: meropenem, gentamicin, and vancomycin. Subsequently, the group studied the subjects’ gut flora over a six-month period to investigate the gut microbiota’s speed of recovery.
Antibiotic treatment had eradicated most bacteria in the gut. However, the gut was not completely sterile even after the administration of the antibiotic cocktail. Much more important was the insight: Some bacteria had formed spores. As spores, bacteria (including those causing illness) may be able to persist, occasionally for several years.
Another important observation was: The first bacteria to re-colonise the gut were primarily harmful ones, such as Enterococcus faecalis which causes urinary tract infections, or Fusobacterium nucleatum which plays a role in periodontal disease. “This observation is a good explanation why most antibiotics cause gastro-intestinal disturbances,” says Forslund. After six months, the gut flora had almost completely recovered, but several bacterial species remained missing. Some of these bacteria were those which help to protect the gut wall and repel pathogens. Furthermore, the report showed that the number of resistance genes had increased.
This study demonstrates yet again that broad-spectrum antibiotics should be administered with care and only as a means of last resort. In particular in children they affect the long-term development of a healthy gut microbiome. According to Sofia Forslund, probiotics, high-fiber diets, or stool transplantations can be helpful in repopulation of healthy bacteria.
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