Global scenario of the RmtE pan-aminoglycoside-resistance mechanism: emergence of the gene in South America associated with a hospital-related IncL plasmid.

Antimicrobial resistance (AMR) mechanisms, especially those conferring resistance to critically important antibiotics, are a great concern for public health. 16S rRNA methyltransferases (16S-RMTases) abolish the effectiveness of most clinically used aminoglycosides, but some of them are considered sporadic, such as RmtE. The main goals of this work were the genomic analysis of bacteria producing 16S-RMTases from a 'One Health' perspective in Venezuela, and the study of the epidemiological and evolutionary scenario of RmtE variants and their related mobile genetic elements (MGEs) worldwide.

Population genomics and antimicrobial resistance dynamics of Escherichia coli in wastewater and river environments.

Aquatic environments are key niches for the emergence, evolution and dissemination of antimicrobial resistance. However, the population diversity and the genetic elements that drive the dynamics of resistant bacteria in different aquatic environments are still largely unknown. The aim of this study was to understand the population genomics and evolutionary events of Escherichia coli resistant to clinically important antibiotics including aminoglycosides, in anthropogenic and natural water ecosystems.

Coexistence of mcr-1 and blaNDM-1 in Escherichia coli from Venezuela.

We studied the presence of the mobile colistin resistance gene mcr-1 in human, animal, and environmental Enterobacteriaceae samples from Cumana, Venezuela, that were collected in 2015. The mcr-1 gene was detected in 2/93 Escherichia coli isolates from swine (novel ST452) and human (ST19) samples that were resistant to colistin. Whole-genome sequencing and transformation experiments identified mcr-1 on an IncI2 plasmid.

RmtC and RmtF 16S rRNA Methyltransferase in NDM-1-Producing Pseudomonas aeruginosa.

We investigated 16S rRNA methyltransferases in 38 blaNDM-1-positive Pseudomonas aeruginosa isolates and found RmtC in 3 isolates, 1 of which also harbored RmtF. The isolates were clonally unrelated; rmtC and rmtF genes were located on a chromosome with the blaNDM-1 gene. Strategies are needed to limit the spread of such isolates.

Prevalence and molecular characterisation of New Delhi metallo-β-lactamases NDM-1, NDM-5, NDM-6 and NDM-7 in multidrug-resistant Enterobacteriaceae from India.

The growing prevalence of carbapenem resistance in Enterobacteriaceae worldwide is a major concern. New Delhi metallo-β-lactamase (NDM)-mediated carbapenem resistance has been identified in Enterobacteriaceae from numerous countries including those of the Indian subcontinent. Currently, seven NDM β-lactamase variants (NDM-1 to -7) have been identified.

Klebsiella pneumoniae sequence type 11 from companion animals bearing ArmA methyltransferase, DHA-1 β-lactamase, and QnrB4.

Seven Klebsiella pneumoniae isolates from dogs and cats in Spain were found to be highly resistant to aminoglycosides, and ArmA methyltransferase was responsible for this phenotype. All isolates were typed by multilocus sequence typing (MLST) as ST11, a human epidemic clone reported worldwide and associated with, among others, OXA-48 and NDM carbapenemases. In the seven strains, armA was borne by an IncR plasmid, pB1025, of 50 kb.

SatR is a repressor of fluoroquinolone efflux pump SatAB.

Streptococcus suis is an emerging zoonotic agent responsible for high-mortality outbreaks among the human population in China. In this species, the ABC transporter SatAB mediates fluoroquinolone resistance when overexpressed. Here, we describe and characterize satR, an open reading frame (ORF) encoding a MarR superfamily regulator that acts as a repressor of satAB.

Association of the novel aminoglycoside resistance determinant RmtF with NDM carbapenemase in Enterobacteriaceae isolated in India and the UK.

Objectives: 16S rRNA methyltransferases are an emerging mechanism conferring high-level resistance to clinically relevant aminoglycosides and have been associated with important mechanisms such as NDM-1. We sought genes encoding these enzymes in isolates highly resistant (MIC >200 mg/L) to gentamicin and amikacin from an Indian hospital and we additionally screened for the novel RmtF enzyme in 132 UK isolates containing NDM.

Methods: All highly aminoglycoside-resistant isolates were screened for armA and rmtA-E by PCR, with cloning experiments performed for isolates negative for these genes.

Fitness cost and interference of Arm/Rmt aminoglycoside resistance with the RsmF housekeeping methyltransferases.

Arm/Rmt methyltransferases have emerged recently in pathogenic bacteria as enzymes that confer high-level resistance to 4,6-disubstituted aminoglycosides through methylation of the G1405 residue in the 16S rRNA (like ArmA and RmtA to -E). In prokaryotes, nucleotide methylations are the most common type of rRNA modification, and they are introduced posttranscriptionally by a variety of site-specific housekeeping enzymes to optimize ribosomal function. Here we show that while the aminoglycoside resistance methyltransferase RmtC methylates G1405, it impedes methylation of the housekeeping methyltransferase RsmF at position C1407, a nucleotide that, like G1405, forms part of the aminoglycoside binding pocket of the 16S rRNA.