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J Appl Microbiol. 2009 Feb;106(2):564-71. doi: 10.1111/j.1365-2672.2008.04026.x.

Acetylation of fluoroquinolone antimicrobial agents by an Escherichia coli strain isolated from a municipal wastewater treatment plant.

Author information

1
Division of Microbiology, National Centre for Toxicological Research, US FDA, Jefferson, AR, USA.

Abstract

AIMS:

To isolate environmental bacteria capable of transforming fluoroquinolones to inactive molecules.

METHODS AND RESULTS:

Bacteria were isolated from the aerobic liquor of a wastewater treatment plant on a medium containing norfloxacin (100 mg l(-1)). Twenty-two isolates were highly resistant (minimal inhibitory concentration: 6.25-200 microg ml(-1)) to five fluoroquinolones and six of them were positive by PCR amplification for the aminoglycoside resistance gene aac(6')-Ib. Of these, only Escherichia coli strain LR09 had the ciprofloxacin-acetylating variant gene aac(6')-Ib-cr; HPLC and mass spectrometry showed that this strain transformed both ciprofloxacin and norfloxacin by N-acetylation. This bacterium also had mutations in the quinolone-resistance determining regions of the gyrA and parC genes.

CONCLUSIONS:

An E. coli isolate from wastewater, which possessed at least two distinct fluoroquinolone resistance mechanisms, inactivated ciprofloxacin and norfloxacin by N-acetylation.

SIGNIFICANCE AND IMPACT OF THE STUDY:

This is the first report of N-acetylation of fluoroquinolones by an aac(6')-Ib-cr-containing bacterium from an environmental source.

[Indexed for MEDLINE]
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