Molecular characterization of Salmonella enterica Serotype Typhi isolates by pulsed-field gel electrophoresis in Hong Kong, 2000-2004.

Objective: To study Salmonella enterica serotype Typhi by pulsed-field gel electrophoresis in Hong Kong. Materials and Methods: One hundred thirty four isolates of Salmonella enterica serotype Typhi collected from 17 public hospitals and clinics in Hong Kong from 2000 to 2004 were studied in relation to epidemiological and clinical events. Isolates originated from 80 patients, with 29 patients providing multiple isolates. Susceptibility to six antibiotics was tested: ampicillin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, nalidixic acid, and ciprofloxacin. Strains were further subtyped by pulsed-field gel electrophoresis (PFGE) by separating XbaI-restricted genomic DNA of isolates. PFGE patterns that were shared between strains were further examined using restriction enzyme BlnI. Results: Of 134 S. Typhi isolates, 29 (21.6%) were resistant to at least one and up to five of the antibiotics tested. Using restriction fragments between 20 and 700 kb for analysis, the number of fragments gene...