Characterization of clinical isolates of Helicobacter pylori in Singapore.

Of the 69 Helicobacter pylori isolates analysed, 31 strains (45%) showed resistance to metronidazole, one strain (1.4%) was resistant to amoxicillin while two strains (2.9%) were resistant to clarithromycin. It was found that metronidazole resistance rates increased in Singapore from 20% to 62% between late 1995 and early 1997. By biotyping using API ZYM, a total of 80% (55/69) strains were characterized as biotype II, while the remaining 20% (14/69) strains belonged to biotype III. Interestingly, 71% (10/14) of biotype III were resistant to metronidazole compared with 38% (21/55) of biotype II. DNA profiles generated by random amplified polymorphic DNA from 69 isolates showed highly diversified DNA fingerprints allowing effective discrimination among strains. Of the 60 H. pylori isolates from peptic ulcer patients, it was found that cagA and vacA occurred in 80% (48/60) and 82% (49/60) isolates, respectively.