CLASS 1 INTEGRON HARBORING BLA_CTX GENE IN KLEBSIELLA PNEUMONIAE.

Marinalda Anselmo Vilela (UPE); Anna Carolina Soares Almeida (UPE); Beathriz Godoy Vilela Barbosa (UPE); Felipe Lira de Sá Cavalcanti (UPE); Marcia Maria Camargo de Morais (UPE); Marcos Antonio de Morais Junior (UFPE)

An integron is defined as a genetic element that possesses a site for integration of gene cassettes, attI, responsible for these site-especific recombination events. A class 1 integron consists of intI integrase-encoding gene in the 5’conserved sequence (5’CS) and the conserved resistance genes qacE∆1 and sul1 in the 3’ conserved sequence (3’CS). These class 1 integrons are the most prevalent in clinic isolates. However, some other class 1 integron structures have been identified, in which there is one 5’CS and two copies of the 3’CS. The aim of this work was to describe the prevalence of class 1 integrons in ESBL-producing Klebsiella pneumoniae isolates and to perform the PCR-based mapping of an bla_CTX-M–containing class 1 integron. A total of 55 nonreplicate clinical isolates of previously identified as ESBL-producing K. pneumoniae, collected from june 2002 to june 2005 was analysed for the presence of class 1 integrons. Following DNA extraction by boiling procedure, supernatant (1mL) was used as template for amplification reactions, using specific primers to detect the class 1 integron components and to carry out the integron PCR-mapping. Results showed that 90.1% of the ESBL-producing K. pneumoniae showed to be integron-positive isolates. In those isolates, the findings suggested that the bla_CTX gene was only integron-located. The results of specific PCR for the variable region 5’CS-3’CS in nine isolates showed three different sizes of 700, 1448 and 1633 bp. PCR mapping of a representative bla_CTX-M carrying class 1 integron showed a structure similar to unusual sul1 type integrons, with two copies of the 3’CS and the bla_CTX gene located outside the variable region. Sequence analysis of the variable region showed the presence of the genes dfrA, with 591 bp and aadA, with 800 bp, which code the enzymes dihydrofolate reductase and adenyltransferases, respectively.  In conclusion, there was a high prevalence of class 1 integrons in ESBL-producing isolates analysed. The unusual class 1 integron carrying bla_CTX-M showed similarities to others described also in south America, suggesting the in course dissemination of such integron structures.