DISPERSION OF CLASS 2 INTEGRON AMONG NON-FERMENTING GRAM NEGATIVE BACILLI (NFGNB)

RAMÍREZ MS, CENTRÓN D.

Atlanta, USA

Congreso; American Society of Microbiology 105th General Meeting; 2005

ASM

In the last years Non-Fermenting Gram negative Bacilli (NFGNB) become a threat in the hospital environment and the cause of terrible infections. The characteristic of this bacilli is that most of them are multiresistant organisms and few drugs are available for the treatment of the infections caused  by them. Integrons are elements that contain the genetic determinants of the components of a site-specific recombination system that recognizes and captures mobile gene cassettes. The basic structure of an integron contains a gene for an integrase (intI), a recombination site (attI) and a promoter (PANT) that allows the expression of the cassettes incorporated in the integron structure .The different integrons are classify according to the nucleotide sequence of the integrase gene. Class 2 integron are embedded in the Tn7 transposon and consist of an integrase gene and the  gene cassettes dfrA1, sat1, aadA1 in the variable region. In the literature there were only 4 more class 2 integrons described so far, Tn1825 ,Tn1826, (Tietze, 1988) Tn4132 (Young H) and the last one described by Biskri et al (2003) Tn7::ISI-ere-A. The class 2 integron integrase is not functional because the presence of an internal stop codon. This might be the reason for the few  rearrangements of class 2 integrons found . There are no evidence of the distribution of this class of integron in S. maltophilia and Burkholderia cepacia in the literature. The aim of this study was to evaluate the dispersion and characterization of class 2 integrons among multiresistant clinical isolates of 258 NFGNB from our country in a six-year period. For this purpose we account with ,161 Acinetobacter spp.,13 Burkholderia spp, 53 Pseudomonas aeruginosa and 31 Stenotrophomonas maltophilia. Total DNA  was extracted and subjected to PCR amplifications with specific primers for the class 2  integrase gene. We found a high prevalence of this class of integrons among Acinetobacter spp,  47% of positives; in contrast of this the rest of the NFGNB  had hardly any class 2 integrons. Pseudomonas aeruginosa and Burkholderia spp had each of them only one class 2 integron positive among the isolates analyzed. For Stenotrophomonas maltophilia the result was negative. We also proceed to performed PCR cartography in order of characterize the variable region of class 2 integron. We unexpectedly found in Acinetobacter spp. that only the 32% of the positive isolates for class 2 integron have Tn7 (o 32% correspond to the same pattern of Tn7) and the 68% are new rearrangement. Since today we have characterized four new class 2 integron rearrangement, 3 in Acinetobacter baumannii and 1 in Burkholderia cenocepacia We named it as, In2-1::Tn7 (sat, aadB, catB2, dfrA1, sat, aadA1, orfX), In2-2::Tn7-like (sat and only tnsE),  In2-3::Tn7 (dfrA1, aadB, catB2, dfrA1, carB4, aadA1, orfX) , In2-4-IS26::Tn7-like (sat, aadA1, ^orfX). In2-1::Tn7, In2-3::Tn7 and In2-4-IS26::Tn7-like correspond to integrons found in Acinetobacter baumannii.