title: Integron carrying a novel metallo-beta-lactamase gene, blaIMP-16, and a fused form of aminoglycoside-resistant gene aac(6')-30/aac(6')-Ib': report from the SENTRY Antimicrobial Surveillance Program.
abstract: Since January 2002 Pseudomonas sp. strains resistant to carbapenems and ceftazidime have been routinely screened as part of the SENTRY Antimicrobial Surveillance Program for metallo-beta-lactamase production, and their resistance determinants have been analyzed. Pseudomonas aeruginosa index strain 101-4704, which harbors a novel bla(IMP) variant, bla(IMP-16), was isolated in April 2002 from a 60-year-old man in Brasilia, Brazil. bla(IMP-16) was found on the chromosome of the P. aeruginosa index strain, and the deduced amino acid sequence (IMP-16) showed the greatest identities to IMP-11 (90.3%) and IMP-8 (89.5%). Sequence analysis revealed that bla(IMP-16) was associated with a class 1 integron, which also encoded aminoglycoside-modifying enzymes. Downstream of bla(IMP-16) resided an open reading frame, which consisted of a new aminoglycoside-modifying gene, namely, aac(6')-30, which was fused with aac(6')-Ib'. The amino acid sequence of the aac(6')-30 putative protein showed the most identity (52.7%) to the sequence of AAC(6')-29b described previously. The fourth gene cassette constituted aadA1. The steady-state kinetics of IMP-16 demonstrated that the enzyme preferred cephalosporins and carbapenems to penicillins. The main functional difference observed among the kinetic values for IMP-16 compared to those for other IMPs was a lack of cefoxitin hydrolysis and a lower kcat/Km value for imipenem (0.36 microM(-1) . s(-1)). This report further emphasizes the spread of metallo-beta-lactamase genes and their close association with various aminoglycoside resistance genes.
authors.affiliation: Disciplina de Doenças Infecciosas e Parasitárias, Universidade Federal de São Paulo, São Paulo, Brazil. rodrigo.mendes@lemc.com.br
authors.forename: Rodrigo E
authors.initials: RE
authors.lastname: Mendes
authors.forename: Mark A
authors.initials: MA
authors.lastname: Toleman
authors.forename: Julival
authors.initials: J
authors.lastname: Ribeiro
authors.forename: Helio S
authors.initials: HS
authors.lastname: Sader
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Walsh
mesh_terms: D000595:Amino Acid Sequence; D000617:Aminoglycosides / Q000494:pharmacology*; D015780:Carbapenems / Q000378:metabolism; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004591:Electrophoresis, Polyacrylamide Gel; D032023:Integrons / Q000235:genetics*; D007700:Kinetics; D007843:Latin America / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D011159:Population Surveillance; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014169:Transformation, Bacterial; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000617:Aminoglycosides; D015780:Carbapenems; D004269:DNA, Bacterial; D001618:beta-Lactamases; C495218:beta-lactamase IMP-16, Pseudomonas aeruginosa