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Restored fitness leads to long-term persistence of resistant Bacteroides strains in the human intestine
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
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2008 (English)In: Anaerobe, ISSN 1075-9964, E-ISSN 1095-8274, Vol. 14, no 3, 157-160 p.Article in journal (Refereed) Published
Abstract [en]

Acquired antibiotic resistance typically confers a cost to the bacteria, but these costs can be reduced by genetic compensation over time. The fitness of two Bacteroides thetaiotaomicron clones consecutively isolated in vivo was studied using an in vitro pair-wise competition method. The isolates derived from faecal samples of two clindamycin-exposed healthy volunteers and the two B. thetaiotaomicron clone types could be followed up to 18 months in these two subjects. The two clones were originally susceptible to clindamycin and lacked erm genes; however, after 7 days of clindamycin administration they carried the erm (erythromycin methylase)(G) or (F) gene, respectively, and expressed phenotypic clindamycin resistance. The initial cost of acquired resistance was high as seen in the in vitro pair-wise competition experiments. At 2 weeks post-administration, no growth disadvantage was detected for isolates of either of the two clones in the in vitro experiments and this regained fitness remained for isolates collected up to 18 months. Competition analysis of an in vitro isolated erm(G) positive transconjugant also demonstrated an initial reduction of fitness that was restored over time. The results indicate that the biological cost associated with a resistance gene can rapidly be compensated during in vivo growth. Thus, once the resistant clone has gained its resistance determinant it will be difficult to eliminate.

Place, publisher, year, edition, pages
2008. Vol. 14, no 3, 157-160 p.
Keyword [en]
Fitness, persistence, competition, bacteroides fragilis, antibiotic resistance
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-100070DOI: 10.1016/j.anaerobe.2008.02.003ISI: 000257552500004PubMedID: 18434218OAI: oai:DiVA.org:uu-100070DiVA: diva2:209348
Available from: 2009-03-24 Created: 2009-03-24 Last updated: 2011-06-30Bibliographically approved

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Andersson, Dan I.
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