Identification and characterization of a novel aac(6')-Iag associated with the blaIMP-1-integron in a multidrug-resistant Pseudomonas aeruginosa.
In a continuing study from Dec 2006 to Apr 2008, we characterized nine multi-drug resistant Pseudomonas aeruginosa strains isolated from four patients in a ward at the Hiroshima University Hospital, Japan. Pulsed-field gel electrophoresis of SpeI-digested genomic DNAs from the isolates suggested the clonal expansion of a single strain; however, only one strain, NK0009, was found to produce metallo-β-lactamase. PCR and subsequent sequencing analysis indicated NK0009 possessed a novel class 1 integron, designated as In124, that carries an array of four gene cassettes: a novel aminoglycoside (AG) resistance gene, aac(6')-Iag, blaIMP-1, a truncated form of blaIMP-1, and a truncated form of aac(6')-Iag. The aac(6')-Iag encoded a 167-amino-acid protein that shows 40% identity with AAC(6')-Iz. Recombinant AAC(6')-Iag protein showed aminoglycoside 6'-N-acetyltransferase activity using thin-layer chromatography (TLC) and MS spectrometric analysis. Escherichia coli carrying aac(6')-Iag showed resistance to amikacin, arbekacin, dibekacin, isepamicin, kanamycin, sisomicin, and tobramycin; but not to gentamicin. A conjugation experiment and subsequent Southern hybridization with the gene probes for blaIMP-1 and aac(6')-Ig strongly suggested In124 is on a conjugal plasmid. Transconjugants acquired resistance to gentamicin and were resistant to virtually all AGs, suggesting that the In124 conjugal plasmid also possesses a gene conferring resistance to gentamicin.
Project Research Center for Nosocomial Infectious Diseases, Hiroshima University, Hiroshima, Japan.
Kanao
K
Kobayashi
Ikue
I
Hayashi
Syuntaro
S
Kouda
Fuminori
F
Kato
Tamaki
T
Fujiwara
Shizuo
S
Kayama
Hideki
H
Hirakawa
Hideyuki
H
Itaha
Hiroki
H
Ohge
Naomasa
N
Gotoh
Tsuguru
T
Usui
Akio
A
Matsubara
Motoyuki
M
Sugai
D000107:Acetylation; D000123:Acetyltransferases / Q000235:genetics* / Q000378:metabolism; D000617:Aminoglycosides / Q000737:chemistry / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D003428:Cross Infection / Q000453:epidemiology; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D023061:Gene Order; D006801:Humans; D032023:Integrons; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D011552:Pseudomonas Infections / Q000453:epidemiology; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000187:drug effects* / Q000235:genetics*; D016415:Sequence Alignment; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000123:Acetyltransferases; C056532:aminoglycoside N(6')-acetyltransferase; D001618:beta-Lactamases