[Evolution of antimicrobial susceptibility of Acinetobacter baumannii clinical isolates].

Acinetobacter baumannii is a microorganism frequently implicated in colonization and infection in hospitalized patients. An increase of resistance has been observed in recent years making these infections difficult to treat. The in vitro activity of 24 antibiotics, 15 betalactam agents and nine nonbetalactams, was studied in 156 A. baumannii clinical isolates. The strains were collected from different clinical samples obtained from inpatients (92%) and 8% were from outpatients. Evolution of susceptibility from January 1995 to December 1997 was studied. MIC of the following antibiotics was determined by the agar dilution method: ampicillin, ticarcillin, piperacillin, ampicillin-sulbactam, amoxicillin- clavulanic acid, ticarcillin-clavulanic acid, piperacillin-tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, meropenem, clavulanic acid, sulbactam, tazobactam, amikacin, gentamicin, tobramycin, ofloxacin, doxycycline, fosfomycin, rifampin, azithromycin and colistin. Low antimicrobial susceptibility was observed in most A. baumannii strains. Colistin, imipenem, meropenem and ampicillin-sulbactam showed the greatest susceptibility (100, 88.4, 88.4 and 84.6%, respectively). A. baumannii strains from inpatients showed a lower antimicrobial susceptibility than strains from outpatients, who showed a high percentage of susceptibility to most antibiotics. Rifampin and azithromycin showed certain in vitro activity against the most susceptible A. baumannii strains. A progressive decrease in susceptibility to most antibiotics was observed during the period studied. Carbapenem-resistant A. baumannii emerged in 1996 and increased in 1997.