RESUMO
A total of 925 Acinetobacter spp. isolates were collected from routine clinical samples of patients admitted to the university hospital of Buenos Aires city during the period 2004-2012. From this collection, 129 isolates identified as Acinetobacter baumannii were selected for molecular studies. Minimal inhibitory concentrations (MICs) of antimicrobials were determined by agar dilution method. Colistin (COL) heteroresistance was investigated by means of population analysis studies. PCR-based methods were used for epidemiological analysis and for the screening of carbapenemases and the bla(tetB) gene. We have observed a steady rise in the MIC50 of imipenem (IMI)-resistant isolates and an increment in the presence of bla(OXA-23)-like gene (74-100%) as well. A rapid increasing rate of minocycline (MIN) resistance and a rise of the MIC50 of the resistant isolates have been detected since the year 2008. All isolates harboured the tet (B) gene. An increase in the value of the tigecycline (TIG) MIC was seen from the year 2007 onwards. This loss of activity was observed among different clones. A rise of COL heteroresistance from 46.4% in 2004 to 95% in 2012 was detected. During this period, COL consumption also increased (11.1-fold). However, COL resistance remained sporadic.
