In169, A New Class 1 Integron that Encoded blaIMP-18 in a Multidrug-Resistant Pseudomonas aeruginosa Isolate from Mexico
Received 13 January 2010; accepted 21 May 2010.
Background and Aims
Carbapenem resistance in Pseudomonas aeruginosa may be due to the presence of metallo-β-lactamases (MβL). The genes that encode these enzymes can be located in association with aminoglycoside-modifying enzymes on class 1 integrons. This study describes the blaIMP-18 class 1 integron array (In169) from a carbapenem-resistant P. aeruginosa clinical isolate obtained at the Centro Medico Nacional La Raza (CMNR) in Mexico City and compares it to other blaIMP-type producers.
Methods
Twenty six multiresistant P. aeruginosa clinical isolates were recovered between June and December 2004 and tested by MicroScan and CLSI agar dilution methods. The MβL production was screened by a disk approximation test and MβL Etest strips, whereas MβL genes and integrons were detected using PCR primers. DNA sequence analysis was carried out by BLAST, and epidemiological typing was performed by pulsed-field gel electrophoresis (PFGE). A Southern hybridization analysis was performed with a blaIMP specific DNA probe.
Results
Nine of 26 P. aeruginosa isolates were imipenem-resistant with unique PFGE patterns (no clonal relation), and only one strain (5106) was positive for MβL production, corresponding to the IMP-type. The class 1 integron encoding the MβL was characterized: it contained the IMP-18, two copies of aadA2 and OXA-2 genes, corresponding to a new class 1 integron array, denoted In169. P. aeruginosa isolate 5106 is genetically related to blaIMP-18 positive P. aeruginosa isolate from a distant hospital (Hospital Infantil de Morelia).
Conclusion
This report is the first to describe the blaIMP-18 in two genetically related isolates from two different institutions.
ABSTRACT