Class 2 integrons dissemination among multidrug resistance (MDR) clones of Acinetobacter baumannii (Ab) circulating in the South Cone

. RAMÍREZ M.S., MORALES A., VILACOBA E., NARDELLI M., MARQUEZ C., ARGENTINIAN INTEGRON STUDY GROUP, CENTRÓN D

New Orleans, Louisiana

Congreso; 111 Congreso General de la American Society for Microbiology; 2011

Background: Ab has emerged as a serious problem in the hospital environment over the world. Previous results from our laboratory showed a particular dispersion of class 2 integrons (In2) in Ab clinical isolates from Argentina. To reveal the current epidemiology of In2, a molecular surveillance analyzing 78 MDR Ab isolates from Argentina and Uruguay collected during the years 2008-2010 was performed. Methods: PCR reactions using specific primers and sequence analysis were carried out to determine the presence of In2 and characterize them. PFGE and REP-PCR were used to determine clonal relationships. Results: The intI2 gene was present in 27 Ab isolates (36,61%), of which the typical Tn7::In-7 array was present in 19 of them. In 7 of the isolates carrying the intI2 gene none of the gene cassettes usually described in the context of class 1 and 2 integrons were detected. At least one of the Tn7 transposition genes was present in 74% of the isolates, and only 30% of the intI2 positive isolates contained the 5 genes of the transposition module. Eighteen In2-containing isolates possessed the integron localized within the attTn7 site. Clonal relationship analysis showed the presence of 2 predominant clones (I and IV), which were widespread in Argentina and Uruguay and did not correspond to the European clones. Conclusion: MDR clones of Ab carrying In2 were found widely disseminated in Argentina and Uruguay. The results showed at least the presence of two predominant clones endemic to the South Cone carrying In2, which could explain the high frequency of In2 in Ab isolates circulating in our region. Analysis of the tns genes of Tn7, showed a significant decrease in the presence of the Tn7 module linked to the class 2 integron, which confirms our previous proposal that the class 2 integrons and the transposition module of Tn7 are evolving independently