ABSTRACT
To describe the rates and patterns of colistin and tigecycline resistance among Acinetobacter baumannii [A. baumannii] isolates from clinical specimens from 2 major hospitals in Riyadh Region over a 2-year period. This is a retrospective review of records of all clinical isolates of A. baumannii from the departments of microbiology at King Faisal Specialist Hospital and Research Center [KFSHRC] and Prince Sultan Military Medical City [PSMMC], Riyadh, Kingdom of Saudi Arabia for the period from January 2010 to December 2011. Records for 1307 Acinetobacter species isolates were identified. The overall tigecycline resistance rates were 9.7% and colistin 1.8%. Among Acinetobacter isolates from KFSHRC, tigecycline resistance rate increased from 10.4% in 2010 to 20.5% in 2011. Colistin resistance increased over the same period from 2.6% to 4.7%. No Acinetobacter isolates from PSMMC were reported to be colistin resistant, while tigecycline resistance rates increased from 1.3% in 2010 to 6.6% in 2011. In KFSHRC, resistance to tigecycline was reported significantly more in isolates from samples that originated in the intensive care units, whereas in PSMMC tigecycline resistance was reported exclusively from clinical areas other than intensive care. No temporal clustering of Acinetobacter isolates was apparent in either hospital over the study period. Tigecycline and colistin resistance were reported from a considerable proportion of Acinetobacter clinical isolates from the study hospitals over a 2-year period