Genetic basis of florfenicol resistance in Acinetobacter isolates from hospital in Chile

Abstract number: P2036

Fernández C., Johnson T., González G., Singer R.

Objective: DNA Sequence analyses suggest that most of the antibiotic resistance genes found in the Acinetobacter baumannii strains have been acquired from bacteria of the genera Pseudomonas, Salmonella, or Escherichia via horizontal gene transfer (HGT). A florfenicol resistance gene (floR) was detected in A. baumannii strains from two hospitals in Chile. Florfenicol is not approved for human use; however, it is related to chloramphenicol and can select for cross-resistance among bacterial pathogens. The aim of this study was to analyse the floR-flanking regions in A. baumannii clinical isolates in order to determine the evolutionary history of the floR gene acquisition in A. baumannii, the linkage between floR and other antibiotic resistance genes, and the potential impact that the floR gene acquisition has on human health.

Methods: The genetic regions upstream and downstream of floR were analysed in four floR-positive, phenicol resistant A. baumannii strains. These strains were isolated from hospitals in Concepción and Santiago, Chile, between 1991 and 2000. The Universal GenomeWalker Kit (BD Biosciences Clontech) was used to PCR amplify and sequence unknown DNA regions adjacent to the floR gene, according to the manufacturer's instructions.

Results: Comparative sequence analysis of the 10 kb fragment revealed that the flanking regions of the floR gene in all isolates had some similarity to regions within previously described Klebsiella pneumoniae plasmid R55, Escherichia coli plasmid 10660–1 and Vibrio cholerae STX animal isolates. Two open reading frames were detected downstream of floR gene. The deduced amino acid sequence of orf1 is shows homology with putative regulator protein and the amino acid sequence of orf2 to those of a putative transposase.

Conclusion: Flanking regions of these isolates indicate that A. baumannii has exchanged genetic material with other bacteria, likely through HGT. The Acinetobacter strains sequenced in this project were almost identical in the region flanking the floR gene, even though these isolates were collected in hospitals 500 km apart and over a span of 10 years. Given that A. baumannii is a common nosocomial pathogen and the fact that these strains were isolated from hospitals, it is unclear when or where the HGT would have occurred, especially considering that florfenicol is used in animal agriculture and has no use in human medicine.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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