Emergence of ArmA and RmtB aminoglycoside resistance 16S rRNA methylases in Belgium.
OBJECTIVE
16S rRNA methylase-mediated high-level resistance to aminoglycosides has been reported recently in clinical isolates of Gram-negative bacilli only from a limited number of countries. This study was conducted to investigate the occurrence of this type of resistance in clinical isolates of Enterobacteriaceae from two Belgian hospitals and the characteristics of the strains.


METHODS
We screened for high-level gentamicin, tobramycin and amikacin resistance in clinical isolates of Enterobacteriaceae consecutively collected between 2000 and 2005 at two laboratories by PCR for the armA, rmtA and rmtB 16S rRNA methylase genes. The beta-lactamase presence in the strains was also determined by phenotypic and genotypic methods.


RESULTS
Overall armA genes were detected in 18 Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae and Citrobacter amalonaticus whereas rmtB was detected in a single E. coli isolate. The rmtA gene was not found. All 16S rRNA methylase-bearing strains produced extended-spectrum beta-lactamases (ESBLs), predominantly type CTX-M-3, as well as various types of beta-lactamases. In the majority of the strains, the armA gene was carried by conjugative plasmids of the IncL/M incompatibility group whereas rmtB was borne by an IncFI plasmid.


CONCLUSIONS
This is the first report of the emergence of 16S rRNA methylases in Enterobacteriaceae in Belgium. The rapid spread of multidrug-resistant isolates producing both ESBLs and 16S rRNA methylases raises clinical concern and may become a major therapeutic threat in the future.
Bogaerts
Pierre
P
Laboratoire de Bactériologie, Cliniques Universitaires UCL de Mont-Godinne, 1 Av. Dr Gaston Thérasse, B-5530 Yvoir, Belgium. pierre.bogaerts@mont.ucl.ac.be
Galimand
Marc
M
Bauraing
Caroline
C
Deplano
Ariane
A
Vanhoof
Raymond
R
De Mendonca
Ricardo
R
Rodriguez-Villalobos
Hector
H
Struelens
Marc
M
Glupczynski
Youri
Y
D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000235:genetics*; D006801:Humans; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000096:biosynthesis
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; C446079:16S rRNA - m7G methyltransferase; C506767:ArmA protein, E coli; D008780:Methyltransferases; D001618:beta-Lactamases