Variable resistance patterns of integron-associated multidrug-resistant Acinetobacter baumannii isolates in a surgical intensive care unit.
Between 1998 and 2000, we characterized 91 nosocomial isolates of Acinetobacter baumannii by antibiotyping and genotyping. A total of 25 ribotypes were obtained among these 91 isolates. When the isolates from surgical intensive care units (ICUs) and other wards were compared, multiresistant A. baumannii isolates with the same ribotype 25 (R-25) were significantly more prevalent in nosocomial infections among the surgical patients. Further subtyping of the strains by pulsed-field gel electrophoresis confirmed that strains of the same ribotype in surgical ICUs and a few isolates from other wards were identical or clonally related. Different antibiotic resistance profiles were observed among these R-25 isolates. All R-25 isolates contained intI1 integrase, and two clusters of integron cassettes were found. These clusters of cassettes were encoded by an open reading frame (ORF) of -5'CS-aac(3)Ia-aadA1a-unknown or f-3'CS or 5'CS-aacA4-aadA1-catB8-3'CS, indicating the involvement of different resistant genes. Two isolates contained bla (IMP-1), which was acquired from a conjugatively transferable plasmid and did not involve integron-associated resistance. In conclusion, an epidemic of nosocomial infections associated with A. baumannii strains that have different resistance profiles was identified. Resistance profiles can change by a combination of plasmid- and integron-associated acquisition, especially in a unit with high antibiotic selective pressures. Infectious control personnel should be alert to the change in resistance profiles during routine monitoring.
Wu
Tsu-Lan
TL
Department of Clinical Pathology, Chang Gung University, Taoyuan.
Ma
Ling
L
Chang
Jen-Chang
JC
Su
Lin-Hui
LH
Chu
Chishih
C
Leu
Hsieh-Shong
HS
Siu
L K
LK
D000151:Acinetobacter Infections / Q000453:epidemiology*; D040981:Acinetobacter baumannii / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D015373:Bacterial Typing Techniques; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D032023:Integrons / Q000235:genetics*; D007362:Intensive Care Units; D008826:Microbial Sensitivity Tests; D010802:Phylogeny