High-level aminoglycoside resistant enterococci isolated from swine.

C R Jackson¹, P J Fedorka-Cray, J B Barrett

¹United States Department of Agriculture, Agricultural Research Service, Antimicrobial Resistance Research Unit, USA. cjackson@saa.ars.usda.gov

|April 9, 2005

Summary

High-level aminoglycoside resistance is prevalent in swine enterococci. Many resistant isolates harbored unknown resistance genes, suggesting novel antimicrobial resistance mechanisms in these bacteria.

Area of Science:

Veterinary Microbiology
Antimicrobial Resistance
Molecular Biology

Background:

Enterococci are significant pathogens in both human and animal health.
Aminoglycoside resistance in enterococci poses a therapeutic challenge.
Swine can serve as reservoirs for antimicrobial-resistant bacteria.

Purpose of the Study:

To investigate the prevalence of high-level aminoglycoside resistance (HLAR) in swine enterococci.
To identify known aminoglycoside resistance genes in resistant isolates.
To explore the presence of potentially novel resistance mechanisms.

Main Methods:

Bacterial isolates: Enterococci collected from swine between 1999-2000.
Antimicrobial susceptibility testing: Minimum Inhibitory Concentrations (MICs) for gentamicin, kanamycin, and streptomycin.
Molecular detection: Polymerase Chain Reaction (PCR) for eight known aminoglycoside resistance genes.

Main Results:

42% of swine enterococci exhibited HLAR to gentamicin, kanamycin, or streptomycin.
The most frequent genes detected were ant(6)-Ia and aac(6')-Ii, primarily in Enterococcus faecium.
A significant proportion (24%) of HLAR isolates and 26% of pan-resistant isolates were negative for all tested genes.

Conclusions:

Swine enterococci harbor diverse aminoglycoside resistance mechanisms.
The presence of gene-negative resistant isolates suggests the existence of unidentified aminoglycoside resistance genes.
Further research is needed to characterize novel resistance determinants in swine-associated enterococci.

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High-level aminoglycoside resistant enterococci isolated from swine.

Area of Science:

Background:

Purpose of the Study:

Main Methods:

Main Results:

Conclusions:

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