Spectrum of causative agents of nosocomial infections (NI) and their susceptibility to antimicrobials (AM) in multiward clinical hospital: results of one-year surveillance study

Abstract

piperacillin/tazobactam and ciprofloxacin. Ninety percent of tested isolates were resistant to amikacin, gentamicin, netilmicin and tobramycin, but 80% were still susceptible to colistin. The MIC ranges for colistin and rifampicin were 1-4 g/ml and 8-16 g/ml, respectively. MIC50 and MIC90 of colistin were 1, 2 g/ml, respectively and MIC50 and MIC90 of rifampicin were 8 g/ml. The synergy study showed the partial synergy effect of colistin when combined with rifampicin in 26.7% of the isolates. Bactericidal activity of the combination was observed at all incubation times by time-kill study. The more damaging effect of the bacterial cell lysis was clearly observed when the bacteria were grown in the combined antimicrobials as compared with the growth in each antimicrobial agent. Conclusion: The in vitro bactericidal activity of the combination between colistin and rifampicin was superior to the single agent. The combination could be a promising alternative for the treatment of infections due to carbapenem-resistant A. baumannii.