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Novel 16S rRNA methyltransferase RmtE3 in Acinetobacter baumannii ST79
Emma Taylor1,2,3, Elita Jauneikaite1,4, Shiranee Sriskandan1,5
1National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Healthcare Associated Infections and Antimicrobial Resistance, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK.
Abstract:
Introduction. The 16S rRNA methyltransferase (16S RMTase) gene armA is the most common mechanism conferring high-level aminoglycoside resistance in Acinetobacter baumannii, although rmtA, rmtB, rmtC, rmtD and rmtE have also been reported.Hypothesis/Gap statement. The occurrence of 16S RMTase genes in A. baumannii in the UK and Republic of Ireland is currently unknown.Aim. To identify the occurrence of 16S RMTase genes in A. baumannii isolates from the UK and the Republic of Ireland between 2004 and 2015.Methodology. Five hundred and fifty pan-aminoglycoside-resistant A. baumannii isolates isolated from the UK and the Republic of Ireland between 2004 and 2015 were screened by PCR to detect known 16S RMTase genes, and then whole-genome sequencing was conducted to screen for novel 16S RMTase genes.Results. A total of 96.5 % (531/550) of isolates were positive for 16S RMTase genes, with all but 1 harbouring armA (99.8 %, 530/531). The remaining isolates harboured rmtE3, a new rmtE variant. Most (89.2 %, 473/530) armA-positive isolates belonged to international clone II (ST2), and the rmtE3-positive isolate belonged to ST79. rmtE3 shared a similar genetic environment to rmtE2 but lacked an ISCR20 element found upstream of rmtE2.Conclusion. This is the first report of rmtE in A. baumannii in Europe; the potential for transmission of rmtE3 to other bacterial species requires further research.
Insights
High-level aminoglycoside resistance in Acinetobacter baumannii is often due to the 16S rRNA methyltransferase (16S RMTase) gene armA. This study identified armA and a novel variant, rmtE3, in UK and Ireland isolates, highlighting potential transmission risks.
Area of Science:
- Molecular biology and microbiology
- Antimicrobial resistance mechanisms
- Genomics and bioinformatics
Background:
- The 16S rRNA methyltransferase (16S RMTase) gene armA is a primary cause of high-level aminoglycoside resistance in Acinetobacter baumannii.
- Other 16S RMTase genes (rmtA-E) have been reported, but their prevalence in the UK and Republic of Ireland remains unknown.
- Understanding the distribution of these resistance genes is crucial for combating antimicrobial resistance.
Purpose of the Study:
- To determine the occurrence of known 16S RMTase genes in Acinetobacter baumannii isolates from the UK and Republic of Ireland.
- To identify novel 16S RMTase genes within these isolates.
- To characterize the genetic context of identified resistance genes.
Main Methods:
- Screening of 550 pan-aminoglycoside-resistant Acinetobacter baumannii isolates (2004-2015) using PCR for known 16S RMTase genes.
- Whole-genome sequencing to identify potential novel 16S RMTase genes.
- Analysis of sequence data to determine isolate lineages (STs) and genetic environments of resistance genes.
Main Results:
- 96.5% of isolates harbored 16S RMTase genes, with armA present in 99.8% of positive cases.
- A novel variant, rmtE3, was identified in one isolate, representing the first report of rmtE in Acinetobacter baumannii in Europe.
- Most armA-positive isolates belonged to international clone II (ST2), while the rmtE3-positive isolate was ST79.
Conclusions:
- The study provides the first comprehensive data on 16S RMTase gene prevalence in Acinetobacter baumannii from the UK and Republic of Ireland.
- The discovery of rmtE3 highlights the emergence of new resistance mechanisms.
- Further research is needed to assess the potential for rmtE3 transmission to other bacterial species.
