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Lack of evidence for DNA in antibiotic preparations as a source of antibiotic resistance genes

Abstract number: 902_p802

Lau S.K.P.

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Objective:

To investigate the significance of DNA encoding antibiotic resistance genes present in antibiotic preparations in the rapid development of antibiotic-induced antimicrobial resistance.

Methods:

A comprehensive study using sequence alignments and phylogenetic analysis of genes encoding antibiotic resistance in antibiotic-producing bacteria and the corresponding ones in non-antibiotic-producing human or animal bacterial isolates [erythromycin resistant methylase (erm), aminoglycoside 3'-phosphotransferase (aph3), aminoglycoside 6'-phosphotransferase (aph6), aminoglycoside acetyltransferase (aac), class A beta-lactamase, tetracycline resistance efflux protein, tetracycline resistance ribosomal protection protein and vancomycin resistance proteins (vanA, vanH, vanX) and bacitracin transport proteins (bcrA, bcrB, bcrC)] was carried out. If DNA encoding antibiotic resistance genes present in antibiotic preparations has been important in the development of antibiotic resistance, genes of almost identical amino acid sequences would be expected to be present in antibiotic-producing organisms and other human or animal bacteria, inferring that horizontal transfer of antibiotic-resistance genes had occurred from the former to the latter.

Results:

The maximum amino acid identities of genes among different non-antibiotic-producing bacterial isolates were close to 100% for most genes, but those between antibiotic-producing and human or animal bacteria ranged from <28 to <77%. Therefore, recent horizontal transfer of antibiotic resistance genes has not occurred from antibiotic-producing organisms to human or animal bacteria. On the other hand, frequent horizontal transfer of antibiotic resistance genes was observed among the human or animal bacteria, even if they were phylogenetically distantly related. Moreover, such transfer was particularly common among gastrointestinal tract flora or pathogens.

Conclusion:

DNA encoding antibiotic resistance genes in antibiotic preparations has not been an important source of antibiotic resistance genes. DNA decontamination during the process of antibiotic synthesis is probably not necessary. The human gastrointestinal tract has been an important place for bacterial gene exchange. The role of the human gut in the dissemination of antibiotic resistance should be further investigated.

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Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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