RESUMEN
Objective To investigate the clonal relatedness of A.baumannii isolates from senile patients by conducting cross-sectional and longitudinal studies on antimicrobial susceptibility profiling and genomic diversity.Methods Cross-sectional study was done among the 170 non-repetitive A.baumannii isolates which were collected from senile patients during two years.Longitudinal study was conducted among 77 A.baumannii collected from 8 senile patients within longtime hospitalization.Results 75.3 ％ of the 170 isolates were non-susceptible to carbapenems,and the phenotype were XDR or MDR which spread evenly all over the senile wards.The isolates belonged to 36 pulsotypes determined by PFGE.Groups Ⅰ (contain119 isolates) were major epidemic strains,which were CRAB with XDR phenotype.In longitudinal study,comparison of pulsotypes was performed for each patient and all isolates were clustered into group Ⅰ except one isolate.All the 77 isolates were XDR.Conclusion Extensive drug-resistance of A.baumannii was a serious problem in the gerontal wards.Clone dissemina tion was the most important style of XDR strains spread.Horizontal infection control measures to interrupt person-to-person transmission should be reinforced to reduce the further spread of XDR A.baumannii.