Pulsed-Field Gel Electrophoresis Genotyping of A. baumannii Isolates

All the 88 A. baumannii isolates were genotyped by using Pulsed-Field Gel Electrophoresis (PFGE) analysis as previously described [49 (link)]. A. baumannii isolates were grown on Mueller-Hinton agar medium plates overnight at 37 °C and bacterial genomic DNAs were prepared. After the genomic DNA was digested with ApaI (TaKaRa, Dalian, China), the DNA fragments were separated by electrophoresis in 1% gold agarose (Lonza) in 0.5 × Tris - borate - EDTA buffer with a CHEF apparatus (CHEF Mapper XA, Bio-Rad, USA). The conditions included 14°C and 6V/cm with alternating pulses at a 120° angle with a 5-35s pulse time gradient for a total of 22 h. The same method was also used to extract the Salmonella enterica serotype Braenderup H9812 genomic DNAs, which was used as the size marker after being digested by XbaI (TaKaRa, Dalian, China) [50 (link)]. The similarity examination of DNA patterns analyzed with BioNumerics 7.0 (Applied Math, USA) was based on Tenover criteria and Dice coefficient, and 80% relatedness was used as the threshold to distinguish the pulsotype [51 ].