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Distribution of aminoglycoside resistance genes in recent clinical isolates of Enterococcus faecalis, Enterococcus
N Kobayashi1, M Alam, Y Nishimoto
1Department of Hygiene, Sapporo Medical University School of Medicine, Sapporo, Japan.
Abstract:
Aminoglycoside modifying enzymes (AMEs) are major factors which confer aminoglycoside resistance on bacteria. Distribution of genes encoding seven AMEs was investigated by multiplex PCR for 279 recent clinical isolates of enterococci derived from a university hospital in Japan. The aac(6')-aph(2"), which is related to high level gentamicin resistance, was detected at higher frequency in Enterococcus faecalis (42.5%) than in Enterococcus faecium (4.3%). Almost half of E. faecalis and E. faecium isolates possessed ant(6)-Ia and aph(3')-IIIa. The profile of AME gene(s) detected most frequently in individual strains of E. faecalis was aac(6')aph(2") + ant(6)-Ia + aph(3')-IIIa, and isolates with this profile showed high level resistance to both gentamicin and streptomycin. In contrast, AME gene profiles of aac(6')-Ii+ ant(6)-Ia+aph(3')-IIIa, followed by aac(6')-Ii alone, were predominant in E. faecium. Only one AME gene profile of ant(6)-Ia+aph(3')-IIIa was found in Enterococcus avium. The ant(4')-Ia and ant(9)-Ia, which have been known to be distributed mostly among Staphylococcus aureus strains, were detected in a few enterococcal strains. An AME gene aph(2")-Ic was not detected in any isolates of the three enterococcal species. These findings indicated a variety of distribution profiles of AME genes among enterococci in our study site.
Insights
Aminoglycoside modifying enzyme (AME) genes vary in enterococci, impacting antibiotic resistance. Multiplex PCR revealed distinct AME profiles in Enterococcus faecalis and Enterococcus faecium, influencing resistance to gentamicin and streptomycin.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Aminoglycoside modifying enzymes (AMEs) are key drivers of aminoglycoside resistance in bacteria.
- Understanding the distribution of AME genes is crucial for managing antibiotic resistance in clinical settings.
Purpose of the Study:
- To investigate the prevalence and distribution of genes encoding seven AMEs in clinical enterococcal isolates.
- To characterize the AME gene profiles in different enterococcal species and their correlation with antibiotic resistance.
Main Methods:
- Multiplex PCR was employed to detect genes encoding seven AMEs.
- The study analyzed 279 recent clinical isolates of enterococci from a Japanese university hospital.
Main Results:
- The aac(6 olyl)-aph(2 olyl) gene, linked to high-level gentamicin resistance, was more frequent in Enterococcus faecalis (42.5%) than Enterococcus faecium (4.3%).
- Nearly half of E. faecalis and E. faecium isolates carried ant(6)-Ia and aph(3 olyl)-IIIa genes.
- Predominant AME gene profiles differed between E. faecalis (aac(6 olyl)-aph(2 olyl) + ant(6)-Ia + aph(3 olyl)-IIIa) and E. faecium (aac(6 olyl)-Ii + ant(6)-Ia + aph(3 olyl)-IIIa).
- The ant(4 olyl)-Ia and ant(9)-Ia genes were rarely found in enterococci, while aph(2 olyl)-Ic was absent.
Conclusions:
- Significant variation exists in the distribution of AME genes among enterococcal species and strains.
- These findings highlight the diverse genetic basis of aminoglycoside resistance in enterococci at the study site.
- The identified AME profiles provide insights into the mechanisms of high-level gentamicin and streptomycin resistance in these pathogens.