Molecular Identification and Typing of Stenotrophomonas maltophilia

Available clinical isolates underwent phylogenetic group determination and pulsed-field gel electrophoresis (PFGE). Clinical isolates were screened using a specific 16S rRNA gene polymerase chain reaction (PCR) assay, and sequenced to confirm taxonomic identities. PCR was performed using primers SM1f (5′-GTTGGGAAAGAAATCCAGC-3′) and SM4 (5′-TTAAGCTTGCCACGAACAG-3′) as described previously [16 (link),17 (link)]. Sequence analysis of PCR products was conducted with MEGA version 3.1 using the maximum likelihood method. AB695350 (S. maltophilia strain 4APB) was used as a control [18 (link)]. S. maltohpilia clinical isolates were typed using PFGE with Xba I digestion as described previously [19 (link)]. PFGE was performed with a CHEF-DR III apparatus (Bio-Rad Korea, Seoul, Korea) using 5 to 35 s of linear ramping at 6 V/cm for 20 h at 14°C. Digital images were analyzed with Fingerprinting II Informatix software (Bio-Rad, Hercules, CA, USA) using the Dice coefficient and UPGMA with a 1% tolerance and 0.5% optimizing setting value. The results were interpreted using the criteria of Tenover et al. [20 (link)].