Antimicrobial resistance and genotyping of Acinetobacter baumannii in ICU

Objective To investigate the outbreak of acinetobacter baumannii in the ICU, and to explore the antimicrobial resistance characteristics of pathogens, and therefore to determine the optimal prevention strategies. Methods From May to June 2007, most of the cases of infection by acinetobacter baumannii in our ICU were collected. PFGE(pulsed field gel electrophoresis)and standard disk diffusion susceptibility tests were performed on the strains isolated from the patients' body fluids including sputum, blood, urine, secretion and from the ICU environment involving the patients' bed sheet, skin surface and medical staff's hands, humidification water of ventilator tubes. Results Twelve strains were resistant to imipenem and meropenem. Colistin sulphate and tigecycline showed a high rate of antimicrobial activity against the strains, the rate of susceptibility being 100% and 91.7% respectively. These strains belonged to 3 clones (clone A, B, C)and there were 2 sub-clones (A1, A2) belonging to clone A. The sub-clone A1 was isolated from the surface of unwashed medical staff's hands and patients' body fluids. From intermediate to resistance, the antimicrobial characteristics of clone A and clone B to minocycline changed over a month, and there was one strain that was resistant to tigecycline. Conclusion The outbreak of acinetobacter baumannii in the ICU was caused by carbapenem resistant acinetobacter baumannii (CRAb). The delicate changes of disk diffusion susceptibility in clones A and B occurred in one month. Unwashed hands of medical staff were probably responsible for the outbreak. Key words: Acinetobacter baumannii; Drug resistance; Sequence homology; Cross infection