Multidrug-Resistant <i>Pseudomonas aeruginosa</i> Strain That Caused an Outbreak in a Neurosurgery Ward and Its <i>aac(6′)-Iae</i> Gene Cassette Encoding a Novel Aminoglycoside Acetyltransferase

<jats:title>ABSTRACT</jats:title> <jats:p> We characterized multidrug-resistant <jats:italic>Pseudomonas aeruginosa</jats:italic> strains isolated from patients involved in an outbreak of catheter-associated urinary tract infections that occurred in a neurosurgery ward of a hospital in Sendai, Japan. Pulsed-field gel electrophoresis of SpeI-, XbaI-, or HpaI-digested genomic DNAs from the isolates revealed that clonal expansion of a <jats:italic>P. aeruginosa</jats:italic> strain designated IMCJ2.S1 had occurred in the ward. This strain possessed broad-spectrum resistance to aminoglycosides, β-lactams, fluoroquinolones, tetracyclines, sulfonamides, and chlorhexidine. Strain IMCJ2.S1 showed a level of resistance to some kinds of disinfectants similar to that of a control strain of <jats:italic>P. aeruginosa</jats:italic> , ATCC 27853. IMCJ2.S1 contained a novel class 1 integron, In113, in the chromosome but not on a plasmid. In113 contains an array of three gene cassettes of <jats:italic>bla</jats:italic> <jats:sub>IMP-1</jats:sub> , a novel aminoglycoside resistance gene, and the <jats:italic>aadA1</jats:italic> gene. The aminoglycoside resistance gene, designated <jats:italic>aac(6′)-Iae</jats:italic> , encoded a 183-amino-acid protein that shared 57.1% identity with AAC(6′)-Iq. Recombinant AAC(6′)-Iae protein showed aminoglycoside 6′- <jats:italic>N</jats:italic> -acetyltransferase activity by thin-layer chromatography. <jats:italic>Escherichia coli</jats:italic> expressing exogenous <jats:italic>aac(6′)-Iae</jats:italic> showed resistance to amikacin, dibekacin, isepamicin, kanamycin, netilmicin, sisomicin, and tobramycin but not to arbekacin, gentamicins, or streptomycin. Alterations of <jats:italic>gyrA</jats:italic> and <jats:italic>parC</jats:italic> at the amino acid sequence level were detected in IMCJ2.S1, suggesting that such mutations confer the resistance to fluoroquinolones observed for this strain. These results indicate that <jats:italic>P. aeruginosa</jats:italic> IMCJ2.S1 has developed multidrug resistance by acquiring resistance determinants, including a novel member of the <jats:italic>aac(6′)-I</jats:italic> family and mutations in drug resistance genes. </jats:p>