[Molecular epidemiological study of multi-drug resistant Acinetobacter baumannii]

To determine the possible genetic background and the source of our hospital's 43 clinical isolates of multidrug-resistant Acinetobacter baumannii, and the category of gene cassettes in type 1 integrons of all strains.

Restriction enzyme Apa I was chosen for all strains in pulsed-field gel electrophoresis (PFGE) methods. Multilocus sequence typing (MLST) was used to compare the allelic profiles of all the strains. PCR method was used for amplify the integrons of all strains.

PFGE results showed that 43 strains were divided into four types. A-type and B-type were divided into 4 and 2 subtypes, respectively. The MLST results showed the existing of three allelic profiles: 1-3-3-2-2-7-3, 1-3-3-2-2-11-3, and 1-3-3-2-2-14-3. B-type and D-type of PFGE have the same allelic profile (1-3-3-2-2-11-3). A-type strains were detected mainly in ICU, and in burn unit only found B- and D-type. The same integron was detected in 62.8% of the strains. The constituent ratio of A1, A2, A3, A4, B1, B2, C and D-type was 40.7%, 18.5%, 7.4%, 3.7%, 14.8%, 3.7%, 3.7% and 7.4%, respectively.

The coexistence of multiple cloning system in this region was proved by the PFGE and MLST, and the same clone can evolve to different subtypes when stimulated by different environmental conditions; and the different carrying-situation of the same integron in strains prove the possibility of the change during the evolution of resistance mechanisms.