Taking probiotics after antibiotics is not the same as with intact gut flora

An interesting study just published in the journal Genome Research examines the differing effects of introducing microflora into the gut environment with and without prior antibiotic treatment. The authors note:

"The intestinal microbiota consists of over 1000 species, which play key roles in gut physiology and homeostasis. Imbalances in the composition of this bacterial community can lead to transient intestinal dysfunctions and chronic disease states. Understanding how to manipulate this ecosystem is thus essential for treating many disorders."

They employed recent technological advances to examine by DNA analysis the long-term effects of transplanting bacteria into the intestine with and without antibiotic pretreatment. Their findings were most interesting:

"The transplantation produced a marked increase in the microbial diversity of the recipients, which stemmed from both capture of new phylotypes and increase in abundance of others. However, when transplantation was performed after antibiotic intake, the resulting state simply combined the reshaping effects of the individual treatments (including the reduced diversity from antibiotic treatment alone). Therefore, lowering the recipient bacterial load by antibiotic intake prior to transplantation did not increase establishment of the donor phylotypes...Remarkably, all of these effects were observed after 1 mo of treatment and persisted after 3 mo."

In other words, rather than opening a niche for the transplantation of beneficial flora, engendering a diverse microbial ecology was inhibited by the destruction of organisms and change in gut homeostasis by the antibiotic.  Moreover, the effects are long-lasting. The authors conclude by stating:

"Overall, our results indicate that the indigenous gut microbial composition is more plastic that previously anticipated. However, since antibiotic pretreatment counterintuitively interferes with the establishment of an exogenous community, such plasticity is likely conditioned more by the altered microbiome gut homeostasis caused by antibiotics than by the primary bacterial loss."

Clinicians should take this into consideration when charting a course for the re-establishment of a healthy gut microbial ecology. Patients should understand that it may take a long time and may not be easy as it goes through a sequence of stages.