Dispersion of Class 2 Integrons among Non-Fermenting-Gram-Negative-Bacilli (NFGNB)

MARÍA SOLEDAD RAMÍREZ; CECILIA QUIROGA; SILVIA PIÑEIRO; DANIELA CENTRÓN

Atlanta, Georgia, USA.

Congreso; American Society for Microbiology 105th General Meeting.; 2005

In the last years 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. Class 2 integron are embedded in the Tn7 transposon. In the literature there were only 4 more class 2 integrons described so far, Tn1825 ,Tn1826, Tn4132 and 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 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 (161 Acinetobacter spp.,13 Burkholderia spp, 53 Pseudomonas aeruginosa and 31 Stenotrophomonas maltophilia) from seven hospital from Buenos Aires during a six-year period. Total DNA was extracted and subjected to PCR amplifications for the class 2 integrase gene. We found a high prevalence of this class of integrons among Acinetobacter spp ( 47%). On the other hand , among Pseudomonas aeruginosa and Burkholderia spp. only one isolate of each of them (1/53 and 1/13, respectively) was positive for the class 2 integrase gene. For Stenotrophomonas maltophilia the result was negative. We also proceed to perform PCR cartography in order of characterize the integrons. We unexpectedly found in Acinetobacter spp. that only 32% correspond to the same pattern of Tn7. Since today we have characterized four new class 2 integron rearrangement, 3 in Acinetobacter baumannii and 1 in Burkholderia cenocepacia. In base of the great diversity of class 2 integron found in our bacterial population a clear nomenclature should be elaborated. Our results also suggest that the presence of class 2 integrons could be overlooked in some species.