Diversity in VIM-2-encoding class 1 integrons and occasional blaSHV2a carriage in isolates of a persistent, multidrug-resistant Pseudomonas aeruginosa clone from Tunis

From 2002 to 2006, 35 of 73 multidrug-resistant Pseudomonas aeruginosa isolates from different wards at Charles Nicolle hospital of Tunis were positive for class B carbapenemase (using the imipenem-EDTA test), owing to a blaVIM-2 gene cassette in a class 1 integron. Twenty-three isolates additionally produced the extended-spectrum β-lactamase SHV2a. DNA sequences immediately surrounding blaSHV2a shared extensive identity with a Klebsiella pneumoniae plasmid sequence. Despite belonging to the same chromosomal type, as shown by pulsed-field gel electrophoresis (PFGE), the VIM-2 producing P. aeruginosa isolates prevalent at Charles Nicolle hospital displayed a diversity of VIM-2-carrying integrons.